The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform

Chenji Wang - One of the best experts on this subject based on the ideXlab platform.

  • truncated erg oncoproteins from tmprss2 erg fusions are resistant to SPOP mediated proteasome degradation
    Molecular Cell, 2015
    Co-Authors: Jian An, Sumiya Dalangood, Cunjie Chang, Xiaodong Pang, Geoffrey C Halling, Chenji Wang, Stephen J. Murphy, Liguo Wang, Xiaowei Zhang, Liang Cheng
    Abstract:

    SPOP mutations and TMPRSS2-ERG rearrangements occur collectively in up to 65% of human prostate cancers. Although the two events are mutually exclusive, it is unclear whether they are functionally interrelated. Here, we demonstrate that SPOP, functioning as an E3 ubiquitin ligase substrate-binding protein, promotes ubiquitination and proteasome degradation of wild-type ERG by recognizing a degron motif at the N terminus of ERG. Prostate cancer-associated SPOP mutations abrogate the SPOP-mediated degradation function on the ERG oncoprotein. Conversely, the majority of TMPRSS2-ERG fusions encode N-terminal-truncated ERG proteins that are resistant to the SPOP-mediated degradation because of degron impairment. Our findings reveal degradation resistance as a previously uncharacterized mechanism that contributes to elevation of truncated ERG proteins in prostate cancer. They also suggest that overcoming ERG resistance to SPOP-mediated degradation represents a viable strategy for treatment of prostate cancers expressing either mutated SPOP or truncated ERG.

  • tumor suppressor SPOP mediates the proteasomal degradation of progesterone receptors prs in breast cancer cells
    American Journal of Cancer Research, 2015
    Co-Authors: Kun Gao, Xiaofeng Jin, Pingzhao Zhang, Yan Tang, Jingtiao Peng, Chenji Wang
    Abstract:

    Progesterone induces proliferation of breast cancer cells and contributes to the development of breast cancer. The effects of progesterone are mediated by progesterone receptors (PRs). However, it is still not fully understood how the proliferative effects of PR is regulated in vivo. Increasing amount of evidence strongly suggests that dysregulation of ubiquitin-proteasome system is closely associated with cancer pathogenesis. Speckle-type POZ protein (SPOP) is an adaptor protein of the CUL3-based E3 ubiquitin ligase complexes. SPOP represents one of the highest loci for loss of heterozygosity (LOH) in breast cancer. SPOP downregulation contributes to breast cancer cell growth and invasion. In this study, we revealed PR as a bona fide substrate for SPOP. SPOP interacts with PR in vivo and targets PR for ubiquitin-dependent proteasomal degradation. Moreover, SPOP suppresses progesteroneinduced PR transactivation, S phase entry, and Erk1/2 activation. Our study revealed novel molecular mechanisms underlying the regulation of PR protein homeostasis in breast cancer cells, and provided insights in understanding the relationship between SPOP inactivation and the development of breast cancer.

  • destruction of ddit3 chop protein by wild type SPOP but not prostate cancer associated mutants
    Human Mutation, 2014
    Co-Authors: Pingzhao Zhang, Xiaofeng Jin, Kun Gao, Yan Tang, Haojie Huang, Dejie Wang, Huan Wang, Yuanyuan Zhang, Chenji Wang
    Abstract:

    Characterization of the exome and genome of prostate cancers by next-generation sequencing has identified numerous genetic alternations. SPOP (speckle-type POZ protein) was identified as one of the most frequently affected genes by somatic point mutations in prostate cancer, suggesting SPOP is potentially a key driver for prostate cancer development and progression. However, how SPOP mutations contribute to prostate cancer remains to be elucidated. SPOP acts as an adaptor protein of the CUL3-RBX1 E3 ubiquitin ligase complex and selectively recruits substrates for their ubiquitination and subsequent degradation. DDIT3 is an endoplasmic reticulum (ER) stress-responsive transcription factor playing an essential role in apoptotic execution pathways triggered by ER stress. Here, we identified DDIT3/CHOP as a bona fide substrate for the SPOP-CUL3-RBX1 E3 ubiquitin ligase complex. SPOP recognizes a Ser/Thr-rich degron in the transactivation domain of DDIT3 and triggers DDIT3 degradation via the ubiquitin-proteasome pathway. Strikingly, prostate cancer-associated mutants of SPOP are defective in promoting DDIT3 degradation. This study reveals novel molecular events underlying the regulation of DDIT3 protein homeostasis and provides insight in understanding the relationship between SPOP mutations and ER stress dysregulation in prostate cancer.

  • destruction of full length androgen receptor by wild type SPOP but not prostate cancer associated mutants
    Cell Reports, 2014
    Co-Authors: Chenji Wang, Yibin Deng, Haojie Huang
    Abstract:

    The SPOP E3 ubiquitin ligase gene is frequently mutated in human prostate cancers. Here, we demonstrate that SPOP recognizes a Ser/Thr-rich degron in the hinge domain of androgen receptor (AR) and induces degradation of full-length AR and inhibition of AR-mediated gene transcription and prostate cancer cell growth. AR splicing variants, most of which lack the hinge domain, escape SPOP-mediated degradation. Prostate-cancer-associated mutants of SPOP cannot bind to and promote AR destruction. Furthermore, androgens antagonize SPOP-mediated degradation of AR, whereas antiandrogens promote this process. This study identifies AR as a bona fide substrate of SPOP and elucidates a role of SPOP mutations in prostate cancer, thus implying the importance of this pathway in resistance to antiandrogen therapy of prostate cancer.

Christopher E Barbieri - One of the best experts on this subject based on the ideXlab platform.

  • quantification of mutant SPOP proteins in prostate cancer using mass spectrometry based targeted proteomics
    Journal of Translational Medicine, 2017
    Co-Authors: Hui Wang, Juan Miguel Mosquera, Christopher E Barbieri, Yuqian Gao, Tujin Shi, Athena A Schepmoes, Thomas L Fillmore, Sungsuk Chae, Dennis Huang, Weijun Qian
    Abstract:

    Speckle-type POZ protein (SPOP) is an E3 ubiquitin ligase adaptor protein that functions as a potential tumor suppressor, and SPOP mutations have been identified in ~10% of human prostate cancers. However, it remains unclear if mutant SPOP proteins can be utilized as biomarkers for early detection, diagnosis, prognosis or targeted therapy of prostate cancer. Moreover, the SPOP mutation sites are distributed in a relatively short region with multiple lysine residues, posing significant challenges for bottom-up proteomics analysis of the SPOP mutations. To address this issue, PRISM (high-pressure, high-resolution separations coupled with intelligent selection and multiplexing)-SRM (selected reaction monitoring) mass spectrometry assays have been developed for quantifying wild-type SPOP protein and 11 prostate cancer-derived SPOP mutations. Despite inherent limitations due to amino acid sequence constraints, all the PRISM-SRM assays developed using Arg-C digestion showed a linear dynamic range of at least two orders of magnitude, with limits of quantification ranged from 0.1 to 1 fmol/μg of total protein in the cell lysate. Applying these SRM assays to analyze HEK293T cells with and without expression of the three most frequent SPOP mutations in prostate cancer (Y87N, F102C or F133V) led to confident detection of all three SPOP mutations in corresponding positive cell lines but not in the negative cell lines. Expression of the F133V mutation and wild-type SPOP was at much lower levels compared to that of F102C and Y87N mutations; however, at present, it is unknown if this also affects the biological activity of the SPOP protein. In summary, PRISM-SRM enables multiplexed, isoform-specific detection of mutant SPOP proteins in cell lysates, providing significant potential in biomarker development for prostate cancer.

  • abstract 4174 SPOP mutation drives tumorigenesis in mouse prostate a novel model of ets negative prostate cancer
    Cancer Research, 2016
    Co-Authors: Mirjam Blattner, Deli Liu, Andrea Sboner, Yu Chen, Mark A. Rubin, Dennis Huang, Dong Gao, Christopher E Barbieri
    Abstract:

    Background: Recurrent mutations in SPOP are the most common point mutations in prostate cancer, occurring in about 10% of cases across multiple independent cohorts. F133V is the most frequently (50%) mutated residue. SPOP mutation defines a distinct molecular subclass of prostate cancer, universally negative for ETS rearrangements. No available prostate cancer cell lines harbor endogenous SPOP mutations, making model systems a critical need. Here, we describe a new mouse model with conditional transgenic expression of SPOP-F133V in the mouse prostate. Experimental Design: We generated a conditional mouse with the SPOP-F133V transgene knocked in to the Rosa26 locus (R26 F133V ); these mice were crossed with Pb-Cre4 mice to express SPOP-F133V specifically in the prostate. Since PTEN deletion is known to drive prostate cancer progression, we crossed Pb-Cre4; R26 F133V mice with Pten f/f mice to study the impact of SPOP mutation in the background of conditional heterozygous ( f/+ ) and homozygous ( f/f ) loss of Pten. Organoid lines were derived from transgenic mouse prostates and infected with inducible Cre-ERT2 to serve as in vitro platforms, 2D as well as 3D, for additional studies. RNA-Seq was performed on independently induced samples. Results: Pb-Cre4;R26 F133V mouse prostates showed a minimal histological phenotype, with rare cytological changes of atypical nuclei (p f/+ , SPOP-F133V expression resulted HG-PIN in 80% (n = 6) of mice, age 6 month, compared to only 20% (n = 8) in control mice. In addition, the HG-PIN in R26 F133V ;Pten f/+ mice showed a distinct phenotype with strong nuclear atypia absent in controls. In the background of Pten f/f , SPOP-F133V leads to poorly differentiated, invasive cancer (n = 8 out of 9) compared to control mice (Pten f/f ), which displayed only HG-PIN (n = 6). Organoids with expression of SPOP-F133V showed increased proliferation and increased ki67 staining. To define signaling pathways controlled by mutant SPOP in the prostate, we performed RNA-seq on mouse organoids expressing SPOP-F133V and controls. We interrogated the gene space nominated by the mouse F133V mutation to the human prostate cancer TCGA transcriptome. Unsupervised clustering demonstrated a highly significant enrichment of ETS negative human prostate cancer (p −16 ), supporting the relevance of our transgenic models to human prostate cancer. Summary: Mutation in SPOP causes an early onset of HG-PIN in the prostate of Pten f/+ mice, and progression to poorly differentiated invasive cancer in Pten f/f mice. HG-PIN shows a very distinct histological phenotype with strong nuclear atypia. Gene expression in murine prostate organoids expressing SPOP-F133V strongly correlates with human tumors, providing relevance for this novel mouse model in defining the biology and therapeutic vulnerability of this subclass of prostate cancer. Citation Format: Mirjam Blattner, Deli Liu, Dennis Huang, Dong Gao, Andrea Sboner, Yu Chen, Mark A. Rubin, Christopher Barbieri. SPOP mutation drives tumorigenesis in mouse prostate - a novel model of ETS negative prostate cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4174.

  • abstract 3872 quantification of mutant SPOP proteins in prostate cancer using targeted proteomics
    Cancer Research, 2016
    Co-Authors: Hui Wang, Juan Miguel Mosquera, Christopher E Barbieri, Yuqian Gao, Tujin Shi, Athena A Schepmoes, Thomas L Fillmore, Sungsuk Chae, Dennis Huang, Weijun Qian
    Abstract:

    Speckle-type POZ protein (SPOP) is an E3 ubiquitin ligase adaptor protein that functions as a potential tumor suppressor, and SPOP mutations have been identified in ∼10% of human prostate cancers. However, it remains unclear if mutant SPOP proteins can be utilized as biomarkers for diagnosis, prognosis or targeted therapy of prostate cancer. To address this issue, selected reaction monitoring (SRM) and PRISM (high-pressure, high-resolution separations coupled with intelligent selection and multiplexing) -SRM mass spectrometry assays have been developed for quantifying mutant SPOP proteins. SRM assays for wild-type SPOP protein and 11 prostate cancer-derived mutations were developed. The presence of multiple lysine residues in the mutation regions precludes the use of conventional tryptic digestion. Arg-C was selected instead due to its superior performance in generating mutation site(s) containing SPOP peptides that are more suitable for SRM analysis comparing to other proteases (e.g., Asp-N). Although the resulting Arg-C peptides are longer and more hydrophobic than typical tryptic peptides, all the SRM assays showed a linear dynamic range of more than two orders of magnitude. The limits of quantification for the mutation site(s) containing peptides range from 10 to 100 fmol/μg of total protein in the cell lysate. Applying these SRM assays to analyze 293T cells with and without expression of the three most frequent SPOP mutations in prostate cancer (Y87N, F102C or F133V) led to confident detection of all three SPOP mutations in corresponding positive cell lines but not in the negative cell lines. Expression of the F133V mutation and wild-type SPOP was at much lower levels compared to that of F102C and Y87N mutations, which agrees with RT-PCR results. It is unknown if this is related to activity of the SPOP protein. PRISM-SRM assays have shown further improvement in sensitivity. SRM enables multiplexed, isoform-specific detection of mutant SPOP proteins in cell lysates, which holds great potential in biomarker development for prostate cancer. Citation Format: Hui Wang, Christopher Barbieri, Jintang He, Yuqian Gao, Chaochao Wu, Athena Schepmoes, Thomas Fillmore, Tujin Shi, Sung-Suk Chae, Dennis Huang, Juan Miguel Mosquera, Wei-Jun Qian, Richard Smith, Sudhir Srivastava, Jacob Kagan, David Camp, Karin Rodland, Mark Rubin, Tao Liu. Quantification of mutant SPOP proteins in prostate cancer using targeted proteomics. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3872.

  • SPOP mutation leads to genomic instability in prostate cancer
    eLife, 2015
    Co-Authors: Gunther Boysen, Mirjam Blattner, Christopher E Barbieri, Sungsuk Chae, Srilakshmi Nataraj, Davide Prandi, Arun Dahija, Dennis Huang
    Abstract:

    Prostate cancer is the most common type of cancer in men in the UK and USA. Cancers develop when cells in the body acquire genetic mutations that allow the cells to grow rapidly and form a mass known as a tumor. Prostate cancer cells from different individuals can carry different genetic mutations, which affects whether the disease progresses and how the tumors respond to medical treatments. This genetic variety arises in cancer cells partly from a phenomenon known as genomic instability, in which DNA mutations accumulate due to defects in DNA repair. Genetic studies of biopsies taken from human prostate cancers have shown that genomic instability causes chromosomes—the structures in which the cell's DNA is organized—to break and then be stuck back together haphazardly. As a result, fragments of chromosomes can end up in the wrong position, be duplicated, or be lost altogether. All of these mutations could spur on the growth of the tumor. However, it is currently not clear why some prostate cancers are more genomically unstable than others, or what exactly causes this instability. Boysen, Barbieri et al. studied prostate cancer cells taken from patients before they started medical treatment. The experiments show that the cancer cells with high levels of genomic instability also often had mutations in a gene that encodes a protein called SPOP. These mutations occur in about 10 percent of men with prostate cancer and appear early in the development of the tumors. Next, they studied the SPOP protein in zebrafish (which is nearly identical to human SPOP), as well as in mouse and human cells. The experiments show that SPOP normally helps the cell to accurately repair DNA that has been damaged. Mutations in SPOP change the DNA repair process, which lead to genomic instability by increasing the likelihood that broken chromosomes will be stuck back together incorrectly. Further experiments tested drugs known as PARP inhibitors on mouse and human prostate cancer cells. The drugs, which have been recently tested successfully in patients with prostate cancer, block a different method of DNA repair that operates separately to the one that involves SPOP. When both of these pathways were inactivated—one by the SPOP mutation, the other by the drug—the cancer cells died more quickly. Therefore, men that are diagnosed with types of prostate cancer in which the gene that encodes SPOP is mutated might benefit from treatment with PARP inhibitors or other therapies that affect DNA repair.

  • abstract 1108 SPOP mutation leads to genomic instability in prostate cancer
    Cancer Research, 2015
    Co-Authors: Gunther Boysen, Mirjam Blattner, Christopher E Barbieri, Sungsuk Chae, Srilakshmi Nataraj, Davide Prandi, Clarisse Marotz, Paola Lecca, Sagar Chhangawala, Pengbo Zou
    Abstract:

    Background: Genomic instability is a fundamental feature of human cancer, and DNA repair defects resulting in impaired genome maintenance promote pathogenesis of many types of cancers. In prostate cancer, structural genomic rearrangements, including translocations and copy number aberrations, are a key mechanism driving tumorigenesis. Recently, whole genome sequencing revealed a striking abundance, complexity, and heterogeneity of genomic rearrangements, potentially suggesting distinct mechanisms of instability in different molecular classes of prostate cancer. However, the somatic alterations underlying these phenomena remain largely undefined. Recurrent mutations in SPOP, the substrate-recognition component of an E3-ubiquitin ligase, represent the most common point mutations in primary prostate cancer, occurring in about 10% of tumors. SPOP mutations define a distinct molecular class of prostate cancer; they are mutually exclusive with TMPRSS2-ERG fusions, but harbor distinct patterns of copy number aberrations. Here, we report that SPOP mutant prostate cancers also harbor increased numbers of genomic rearrangements, and functional data suggest that SPOP mutation alters repair of DNA double strand breaks (DSB). Methods: We systematically investigated somatic alterations associated with genomic rearrangements, using a composite data set of 402 clinically localized prostate cancers. Functional analyses in vitro and in vivo were used to define pathways affected, and interrogate DNA repair phenotypes. Results: In human prostate cancers, SPOP mutation is an early event specifically associated with increased intrachromosomal genomic rearrangements. Using a zebrafish model, SPOP mutation results in a transcriptional response consistent with BRCA1 inactivation, implicating altered repair of DSB. In vitro data suggest that SPOP participates in repair of DSB, and SPOP mutation impairs homology-directed repair (HDR), instead promoting error-prone non-homologous end joining (NHEJ). Finally, SPOP mutation sensitizes prostate cancer cells to DNA damaging therapeutic agents such as PARP inhibitors. Conclusions: These results implicate SPOP as a novel participant in DSB repair, suggest that SPOP mutation drives prostate tumorigenesis in part through genomic instability, and indicate that SPOP mutant prostate cancer may be selectively responsive to DNA damaging therapeutics. Citation Format: Gunther Boysen, Christopher E. Barbieri, Davide Prandi, Sung-Suk Chae, Srilakshmi Nataraj, Mirjam Blattner, Clarisse Marotz, Limei Xu, Paola Lecca, Sagar Chhangawala, Pengbo Zou, Andrea Sboner, Francesca Demichelis, Yariv Houvras, Mark A. Rubin. SPOP mutation leads to genomic instability in prostate cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1108. doi:10.1158/1538-7445.AM2015-1108

Haojie Huang - One of the best experts on this subject based on the ideXlab platform.

  • mutated SPOP e3 ligase promotes 17βhsd4 protein degradation to drive androgenesis and prostate cancer progression
    Cancer Research, 2021
    Co-Authors: Lei Shi, Yuqian Yan, Binyuan Yan, Yunqian Pan, Jacob J Orme, Jun Zhang, Jun Pang, Haojie Huang
    Abstract:

    Molecular mechanisms underlying intratumoral androgenesis and aberrant androgen receptor (AR) activation in prostate cancer (PCa) remain poorly understood. Here we demonstrate that ectopic expression of the E3 ubiquitin ligase adaptor speckle-type poxvirus and zinc finger domain protein (SPOP) stabilizes 17βHSD4. SPOP bound a functional substrate-binding consensus (SBC) motif 315RATST319 in 17βHSD4 and promoted non-degradable K27- and K29-linked poly-ubiquitination of 17βHSD4. The effect of SPOP was antagonized by serum- and glucocorticoid kinase-3 (SGK3)-mediated phosphorylation of serine 318 (S318) in the SBC and S318 phosphorylation-dependent binding of SKP2 E3 ligase and subsequent K48-linked poly-ubiquitination and proteasomal degradation of 17βHSD4. PCa-associated SPOP mutations impaired the SPOP-17βHSD4 interaction, caused 17βHSD4 protein destruction in PCa cells in culture and patient specimens, and increased testosterone production and PCa cell growth in vitro and in mouse models. Thus, we have identified SPOP and SKP2 as two essential E3 ubiquitin ligases that exert opposite effects on 17βHSD4 protein degradation and intratumoral androgenesis in PCa cells. We further demonstrate that SPOP mutations or SKP2 overexpression contribute to PCa progression by decreasing 17βHSD4 expression and increasing intratumoral androgen synthesis.

  • abstract lb a25 pten loss promotes phosphorylation dependent acetylation and inhibition of SPOP tumor suppressor
    Molecular Cancer Therapeutics, 2015
    Co-Authors: Haojie Huang
    Abstract:

    The Cullin 3-based E3 ubiquitin ligase substrate-binding protein SPOP is inactivated in approximately 8-15% of human prostate cancers due to gene mutation. Intriguingly, SPOP mutations and inactivation of the PTEN tumor suppressor in human prostate cancers are mutually exclusive. However, it is unclear whether SPOP remains functionally active in PTEN-deficient prostate cancer cells. In the current study, we demonstrate that PTEN loss induces phosphorylation and nuclear exportation of SPOP. We identify a putative cyclin-dependent kinase (CDK) phosphorylation site (serine 222) in SPOP BTB domain, a motif interacting with Cullin 3 and demonstrate that PTEN loss induces SPOP cytoplasm accumulation in a manner dependent on CDK2-mediated phosphorylation of SPOP at serine 222. We further show that serine 222 phosphorylation impairs dimerization and the E3 ligase activity of SPOP without affecting its interaction with Cullin 3. We also identify a potential p300 acetylation site in the C-terminal nuclear localization sequence of SPOP. We demonstrate that acetylation by p300 promotes SPOP translocation from nucleus to cytoplasm and this effect is enhanced by CDK2-mediated phosphorylation of SPOP at serine 222. In contrast, Sirt 2 and Sirt 6 of the sirtuin family are verified to be responsible for deacetylation of SPOP. In the conditional Pten knockout prostate cancer mouse model, Pten deletion induces cytosolic accumulation of SPOP, but the process is reversed in Pten and p300 double knockout prostatic cells. Collectively, our findings reveal cytoplasmic localization and enzymatic inactivation of SPOP as a previously uncharacterized mechanism that contributes to PTEN loss-induced prostate tumorigenesis. They also suggest that blocking SPOP cytoplasm localization represents a viable therapeutic option for treatment of prostate cancers harboring PTEN inactivation. Citation Format: Jian An, Haojie Huang. PTEN loss promotes phosphorylation-dependent acetylation and inhibition of SPOP tumor suppressor. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr LB-A25.

  • destruction of ddit3 chop protein by wild type SPOP but not prostate cancer associated mutants
    Human Mutation, 2014
    Co-Authors: Pingzhao Zhang, Xiaofeng Jin, Kun Gao, Yan Tang, Haojie Huang, Dejie Wang, Huan Wang, Yuanyuan Zhang, Chenji Wang
    Abstract:

    Characterization of the exome and genome of prostate cancers by next-generation sequencing has identified numerous genetic alternations. SPOP (speckle-type POZ protein) was identified as one of the most frequently affected genes by somatic point mutations in prostate cancer, suggesting SPOP is potentially a key driver for prostate cancer development and progression. However, how SPOP mutations contribute to prostate cancer remains to be elucidated. SPOP acts as an adaptor protein of the CUL3-RBX1 E3 ubiquitin ligase complex and selectively recruits substrates for their ubiquitination and subsequent degradation. DDIT3 is an endoplasmic reticulum (ER) stress-responsive transcription factor playing an essential role in apoptotic execution pathways triggered by ER stress. Here, we identified DDIT3/CHOP as a bona fide substrate for the SPOP-CUL3-RBX1 E3 ubiquitin ligase complex. SPOP recognizes a Ser/Thr-rich degron in the transactivation domain of DDIT3 and triggers DDIT3 degradation via the ubiquitin-proteasome pathway. Strikingly, prostate cancer-associated mutants of SPOP are defective in promoting DDIT3 degradation. This study reveals novel molecular events underlying the regulation of DDIT3 protein homeostasis and provides insight in understanding the relationship between SPOP mutations and ER stress dysregulation in prostate cancer.

  • destruction of full length androgen receptor by wild type SPOP but not prostate cancer associated mutants
    Cell Reports, 2014
    Co-Authors: Chenji Wang, Yibin Deng, Haojie Huang
    Abstract:

    The SPOP E3 ubiquitin ligase gene is frequently mutated in human prostate cancers. Here, we demonstrate that SPOP recognizes a Ser/Thr-rich degron in the hinge domain of androgen receptor (AR) and induces degradation of full-length AR and inhibition of AR-mediated gene transcription and prostate cancer cell growth. AR splicing variants, most of which lack the hinge domain, escape SPOP-mediated degradation. Prostate-cancer-associated mutants of SPOP cannot bind to and promote AR destruction. Furthermore, androgens antagonize SPOP-mediated degradation of AR, whereas antiandrogens promote this process. This study identifies AR as a bona fide substrate of SPOP and elucidates a role of SPOP mutations in prostate cancer, thus implying the importance of this pathway in resistance to antiandrogen therapy of prostate cancer.

Xiaofeng Jin - One of the best experts on this subject based on the ideXlab platform.

  • crl3 SPOP ubiquitin ligase complex suppresses the growth of diffuse large b cell lymphoma by negatively regulating the myd88 nf κb signaling
    Leukemia, 2020
    Co-Authors: Xiaofeng Jin, Jian Wang, Zihan Lin, Ting Lin, Qing Shi, Kai Feng, Xiaying Zhao, Linyi Zhou, Lei Jiang, Hui Zhuang
    Abstract:

    Recurrent oncogenic mutations of MyD88 have been identified in a variety of lymphoid malignancies. Gain-of-function mutations of MyD88 constitutively activate downstream NF-κB signaling pathways, resulting in increased cellular proliferation and survival. However, whether MyD88 activity can be aberrantly regulated in MyD88-wild-type lymphoid malignancies remains poorly understood. SPOP is an adaptor protein of CUL3-based E3 ubiquitin ligase complex and frequently mutated genes in prostate and endometrial cancers. In this study, we reveal that SPOP binds to and induces the nondegradative ubiquitination of MyD88 by recognizing an atypical SPOP-binding motif in MyD88. This modification blocks Myddosome assembly and downstream NF-κB activation. SPOP is mutated in a subset of lymphoid malignancies, including diffuse large B-cell lymphoma (DLBCL). Lymphoid malignancies-associated SPOP mutants exhibited impaired binding to MyD88 and suppression of NF-κB activation. The DLBCL-associated, SPOP-binding defective mutants of MyD88 escaped from SPOP-mediated ubiquitination, and their effect on NF-κB activation is stronger than that of wild-type MyD88. Moreover, SPOP suppresses DLBCL cell growth in vitro and tumor xenograft in vivo by inhibiting the MyD88/NF-κB signaling. Therefore, SPOP acts as a tumor suppressor in DLBCL. Mutations in the SPOP-MyD88 binding interface may disrupt the SPOP-MyD88 regulatory axis and promote aberrant MyD88/NF-κB activation and cell growth in DLCBL.

  • SPOP targets oncogenic protein zbtb3 for destruction to suppress endometrial cancer
    American Journal of Cancer Research, 2019
    Co-Authors: Xiaofeng Jin, Jian Wang, Hui Zhuang, Jianye Yang, Zihan Lin, Ting Lin, Liliang Shen, Chunhong Yan, Jingfei Zheng, Jie Zhu
    Abstract:

    Dysregulation of the ubiquitin-proteasome pathway is closely associated with cancer initiation and progression. SPOP is an adapter protein of the CUL3-based E3 ubiquitin ligase complexes. Several whole genome/exome sequencing studies on endometrial cancers (ECs) revealed that the SPOP gene is frequently mutated. However, how SPOP mutations contribute to EC remains poorly understood. In this study, transcription factor ZBTB3 was identified as a proteolytic substrate for the SPOP-CUL3-RBX1 E3 ubiquitin ligase complex. SPOP specifically recognizes two Ser/Thr (S/T)-rich degrons located in ZBTB3 and triggers the degradation of ZBTB3 via the ubiquitin-proteasome pathway. By contrast, EC-associated SPOP mutants are defective in regulating ZBTB3 stability. SPOP inactivation promotes endometrial cell proliferation, migration, and invasion partly through ZBTB3 accumulation. Sonic hedgehog (SHH) was found to be a transcriptional target of ZBTB3. SPOP inactivation leads to ZBTB3-dependent SHH upregulation in EC cells. RUSKI-43, a small molecule inhibitor of SHH, suppresses cell proliferation, migration, and invasion in SPOP-depleted or EC-associated SPOP mutant-overexpressed EC cells. Our data indicate that pharmacological inhibition of SHH represents a possible treatment strategy for SPOP-mutated ECs.

  • Dysregulation of INF2-mediated mitochondrial fission in SPOP-mutated prostate cancer.
    PLoS genetics, 2017
    Co-Authors: Xiaofeng Jin, Jie Wang, Kun Gao, Pingzhao Zhang, Longfang Yao, Yan Tang, Lisha Tang, Jiantao Xiao, Enceng Zhang
    Abstract:

    Next-generation sequencing of the exome and genome of prostate cancers has identified numerous genetic alternations. SPOP (Speckle-type POZ Protein) was one of the most frequently mutated genes in primary prostate cancer, suggesting SPOP is a potential driver of prostate cancer development and progression. However, how SPOP mutations contribute to prostate cancer pathogenesis remains poorly understood. SPOP acts as an adaptor protein of the CUL3-RBX1 E3 ubiquitin ligase complex that generally recruits substrates for ubiquitination and subsequent degradation. ER-localized isoform of the formin protein inverted formin 2 (INF2) mediates actin polymerization at ER-mitochondria intersections and facilitates DRP1 recruitment to mitochondria, which is a critical step in mitochondrial fission. Here, we revealed that SPOP recognizes a Ser/Thr (S/T)-rich motif in the C-terminal region of INF2 and triggers atypical polyubiquitination of INF2. These ubiquitination modifications do not lead to INF2 instability, but rather reduces INF2 localization in ER and mitochondrially associated DRP1 puncta formation, therefore abrogates its ability to facilitate mitochondrial fission. INF2 mutant escaping from SPOP-mediated ubiquitination is more potent in prompting mitochondrial fission. Moreover, prostate cancer-associated SPOP mutants increase INF2 localization in ER and promote mitochondrial fission, probably through a dominant-negative effect to inhibit endogenous SPOP. Moreover, INF2 is important for SPOP inactivation-induced prostate cancer cell migration and invasion. These findings reveal novel molecular events underlying the regulation of INF2 function and localization, and provided insights in understanding the relationship between SPOP mutations and dysregulation of mitochondrial dynamics in prostate cancer.

  • tumor suppressor SPOP mediates the proteasomal degradation of progesterone receptors prs in breast cancer cells
    American Journal of Cancer Research, 2015
    Co-Authors: Kun Gao, Xiaofeng Jin, Pingzhao Zhang, Yan Tang, Jingtiao Peng, Chenji Wang
    Abstract:

    Progesterone induces proliferation of breast cancer cells and contributes to the development of breast cancer. The effects of progesterone are mediated by progesterone receptors (PRs). However, it is still not fully understood how the proliferative effects of PR is regulated in vivo. Increasing amount of evidence strongly suggests that dysregulation of ubiquitin-proteasome system is closely associated with cancer pathogenesis. Speckle-type POZ protein (SPOP) is an adaptor protein of the CUL3-based E3 ubiquitin ligase complexes. SPOP represents one of the highest loci for loss of heterozygosity (LOH) in breast cancer. SPOP downregulation contributes to breast cancer cell growth and invasion. In this study, we revealed PR as a bona fide substrate for SPOP. SPOP interacts with PR in vivo and targets PR for ubiquitin-dependent proteasomal degradation. Moreover, SPOP suppresses progesteroneinduced PR transactivation, S phase entry, and Erk1/2 activation. Our study revealed novel molecular mechanisms underlying the regulation of PR protein homeostasis in breast cancer cells, and provided insights in understanding the relationship between SPOP inactivation and the development of breast cancer.

  • endometrial cancer associated mutants of SPOP are defective in regulating estrogen receptor α protein turnover
    Cell Death and Disease, 2015
    Co-Authors: Pingzhao Zhang, Xiaofeng Jin, Kun Gao, Yan Tang, Jing Peng, Reziya Wumaier, Yiyin Zhang, Q Yan, Y Dong, H Huang
    Abstract:

    Increasing amounts of evidence strongly suggests that dysregulation of ubiquitin-proteasome system is closely associated with cancer pathogenesis. Speckle-type POZ protein (SPOP) is an adapter protein of the CUL3-based E3 ubiquitin ligase complexes. It selectively recruits substrates for their ubiquitination and subsequent degradation. Recently, several exome-sequencing studies of endometrial cancer revealed high frequency somatic mutations in SPOP (5.7–10%). However, how SPOP mutations contribute to endometrial cancer remains unknown. Here, we identified estrogen receptor-α (ERα), a major endometrial cancer promoter, as a substrate for the SPOP-CUL3-RBX1 E3 ubiquitin ligase complex. SPOP specifically recognizes multiple Ser/Thr (S/T)-rich degrons located in the AF2 domain of ERα, and triggers ERα degradation via the ubiquitin-proteasome pathway. SPOP depletion by siRNAs promotes endometrial cells growth. Strikingly, endometrial cancer-associated mutants of SPOP are defective in regulating ERα degradation and ubiquitination. Furthermore, we found that SPOP participates in estrogen-induced ERα degradation and transactivation. Our study revealed novel molecular mechanisms underlying the regulation of ERα protein homeostasis in physiological and pathological conditions, and provided insights in understanding the relationship between SPOP mutations and the development of endometrial cancer.

Mirjam Blattner - One of the best experts on this subject based on the ideXlab platform.

  • SPOP mutation drives prostate neoplasia without stabilizing oncogenic transcription factor ERG
    The Journal of clinical investigation, 2017
    Co-Authors: Jonathan Shoag, Deli Liu, Mirjam Blattner, Andrea Sboner, Kyung Park, Lesa D. Deonarine, Brian D. Robinson, Juan Miguel Mosquera, Yu Chen, Mark A. Rubin
    Abstract:

    Nearly 50% of prostate cancers harbor gene fusions that lead to overexpression of the transcription factor ERG, while a mutually exclusive 10% of prostate cancers harbor recurrent mutations in the gene encoding the E3 ubiquitin ligase SPOP. Recent reports suggest that SPOP acts as a ubiquitin ligase for ERG and propose that ERG stabilization is the oncogenic effector of SPOP mutation. Here, we used human prostate cancer samples and showed that the vast majority of human SPOP-mutant cancers do not express ERG. Comparison of SPOP-mutant and ERG-fusion organoid models showed evidence of divergent, rather than common, transcriptional programs. Furthermore, expression of prostate cancer-associated SPOP mutations in genetically engineered mouse models of SPOP-mutant prostate cancer did not result in the expression of ERG protein in histologically normal prostate glands, high-grade prostatic intraepithelial neoplasia, invasive adenocarcinoma, or prostate organoids. In summary, we found no evidence that ERG is an effector of SPOP mutation in human prostate cancer or mouse models.

  • SPOP mutation drives prostate tumorigenesis in vivo through coordinate regulation of pi3k mtor and ar signaling
    Cancer Cell, 2017
    Co-Authors: Mirjam Blattner, Deli Liu, Lesa D. Deonarine, Brian D. Robinson, Dennis Huang, Anton Poliakov, Dong Gao, Srilakshmi Nataraj, Michael A Augello, Verena Sailer
    Abstract:

    Recurrent point mutations in SPOP define a distinct molecular subclass of prostate cancer. Here, we describe a mouse model showing that mutant SPOP drives prostate tumorigenesis in vivo. Conditional expression of mutant SPOP in the prostate dramatically altered phenotypes in the setting of Pten loss, with early neoplastic lesions (high-grade prostatic intraepithelial neoplasia) with striking nuclear atypia and invasive, poorly differentiated carcinoma. In mouse prostate organoids, mutant SPOP drove increased proliferation and a transcriptional signature consistent with human prostate cancer. Using these models and human prostate cancer samples, we show that SPOP mutation activates both PI3K/mTOR and androgen receptor signaling, effectively uncoupling the normal negative feedback between these two pathways.

  • abstract 4174 SPOP mutation drives tumorigenesis in mouse prostate a novel model of ets negative prostate cancer
    Cancer Research, 2016
    Co-Authors: Mirjam Blattner, Deli Liu, Andrea Sboner, Yu Chen, Mark A. Rubin, Dennis Huang, Dong Gao, Christopher E Barbieri
    Abstract:

    Background: Recurrent mutations in SPOP are the most common point mutations in prostate cancer, occurring in about 10% of cases across multiple independent cohorts. F133V is the most frequently (50%) mutated residue. SPOP mutation defines a distinct molecular subclass of prostate cancer, universally negative for ETS rearrangements. No available prostate cancer cell lines harbor endogenous SPOP mutations, making model systems a critical need. Here, we describe a new mouse model with conditional transgenic expression of SPOP-F133V in the mouse prostate. Experimental Design: We generated a conditional mouse with the SPOP-F133V transgene knocked in to the Rosa26 locus (R26 F133V ); these mice were crossed with Pb-Cre4 mice to express SPOP-F133V specifically in the prostate. Since PTEN deletion is known to drive prostate cancer progression, we crossed Pb-Cre4; R26 F133V mice with Pten f/f mice to study the impact of SPOP mutation in the background of conditional heterozygous ( f/+ ) and homozygous ( f/f ) loss of Pten. Organoid lines were derived from transgenic mouse prostates and infected with inducible Cre-ERT2 to serve as in vitro platforms, 2D as well as 3D, for additional studies. RNA-Seq was performed on independently induced samples. Results: Pb-Cre4;R26 F133V mouse prostates showed a minimal histological phenotype, with rare cytological changes of atypical nuclei (p f/+ , SPOP-F133V expression resulted HG-PIN in 80% (n = 6) of mice, age 6 month, compared to only 20% (n = 8) in control mice. In addition, the HG-PIN in R26 F133V ;Pten f/+ mice showed a distinct phenotype with strong nuclear atypia absent in controls. In the background of Pten f/f , SPOP-F133V leads to poorly differentiated, invasive cancer (n = 8 out of 9) compared to control mice (Pten f/f ), which displayed only HG-PIN (n = 6). Organoids with expression of SPOP-F133V showed increased proliferation and increased ki67 staining. To define signaling pathways controlled by mutant SPOP in the prostate, we performed RNA-seq on mouse organoids expressing SPOP-F133V and controls. We interrogated the gene space nominated by the mouse F133V mutation to the human prostate cancer TCGA transcriptome. Unsupervised clustering demonstrated a highly significant enrichment of ETS negative human prostate cancer (p −16 ), supporting the relevance of our transgenic models to human prostate cancer. Summary: Mutation in SPOP causes an early onset of HG-PIN in the prostate of Pten f/+ mice, and progression to poorly differentiated invasive cancer in Pten f/f mice. HG-PIN shows a very distinct histological phenotype with strong nuclear atypia. Gene expression in murine prostate organoids expressing SPOP-F133V strongly correlates with human tumors, providing relevance for this novel mouse model in defining the biology and therapeutic vulnerability of this subclass of prostate cancer. Citation Format: Mirjam Blattner, Deli Liu, Dennis Huang, Dong Gao, Andrea Sboner, Yu Chen, Mark A. Rubin, Christopher Barbieri. SPOP mutation drives tumorigenesis in mouse prostate - a novel model of ETS negative prostate cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4174.

  • SPOP mutation leads to genomic instability in prostate cancer
    eLife, 2015
    Co-Authors: Gunther Boysen, Mirjam Blattner, Christopher E Barbieri, Sungsuk Chae, Srilakshmi Nataraj, Davide Prandi, Arun Dahija, Dennis Huang
    Abstract:

    Prostate cancer is the most common type of cancer in men in the UK and USA. Cancers develop when cells in the body acquire genetic mutations that allow the cells to grow rapidly and form a mass known as a tumor. Prostate cancer cells from different individuals can carry different genetic mutations, which affects whether the disease progresses and how the tumors respond to medical treatments. This genetic variety arises in cancer cells partly from a phenomenon known as genomic instability, in which DNA mutations accumulate due to defects in DNA repair. Genetic studies of biopsies taken from human prostate cancers have shown that genomic instability causes chromosomes—the structures in which the cell's DNA is organized—to break and then be stuck back together haphazardly. As a result, fragments of chromosomes can end up in the wrong position, be duplicated, or be lost altogether. All of these mutations could spur on the growth of the tumor. However, it is currently not clear why some prostate cancers are more genomically unstable than others, or what exactly causes this instability. Boysen, Barbieri et al. studied prostate cancer cells taken from patients before they started medical treatment. The experiments show that the cancer cells with high levels of genomic instability also often had mutations in a gene that encodes a protein called SPOP. These mutations occur in about 10 percent of men with prostate cancer and appear early in the development of the tumors. Next, they studied the SPOP protein in zebrafish (which is nearly identical to human SPOP), as well as in mouse and human cells. The experiments show that SPOP normally helps the cell to accurately repair DNA that has been damaged. Mutations in SPOP change the DNA repair process, which lead to genomic instability by increasing the likelihood that broken chromosomes will be stuck back together incorrectly. Further experiments tested drugs known as PARP inhibitors on mouse and human prostate cancer cells. The drugs, which have been recently tested successfully in patients with prostate cancer, block a different method of DNA repair that operates separately to the one that involves SPOP. When both of these pathways were inactivated—one by the SPOP mutation, the other by the drug—the cancer cells died more quickly. Therefore, men that are diagnosed with types of prostate cancer in which the gene that encodes SPOP is mutated might benefit from treatment with PARP inhibitors or other therapies that affect DNA repair.

  • abstract 1108 SPOP mutation leads to genomic instability in prostate cancer
    Cancer Research, 2015
    Co-Authors: Gunther Boysen, Mirjam Blattner, Christopher E Barbieri, Sungsuk Chae, Srilakshmi Nataraj, Davide Prandi, Clarisse Marotz, Paola Lecca, Sagar Chhangawala, Pengbo Zou
    Abstract:

    Background: Genomic instability is a fundamental feature of human cancer, and DNA repair defects resulting in impaired genome maintenance promote pathogenesis of many types of cancers. In prostate cancer, structural genomic rearrangements, including translocations and copy number aberrations, are a key mechanism driving tumorigenesis. Recently, whole genome sequencing revealed a striking abundance, complexity, and heterogeneity of genomic rearrangements, potentially suggesting distinct mechanisms of instability in different molecular classes of prostate cancer. However, the somatic alterations underlying these phenomena remain largely undefined. Recurrent mutations in SPOP, the substrate-recognition component of an E3-ubiquitin ligase, represent the most common point mutations in primary prostate cancer, occurring in about 10% of tumors. SPOP mutations define a distinct molecular class of prostate cancer; they are mutually exclusive with TMPRSS2-ERG fusions, but harbor distinct patterns of copy number aberrations. Here, we report that SPOP mutant prostate cancers also harbor increased numbers of genomic rearrangements, and functional data suggest that SPOP mutation alters repair of DNA double strand breaks (DSB). Methods: We systematically investigated somatic alterations associated with genomic rearrangements, using a composite data set of 402 clinically localized prostate cancers. Functional analyses in vitro and in vivo were used to define pathways affected, and interrogate DNA repair phenotypes. Results: In human prostate cancers, SPOP mutation is an early event specifically associated with increased intrachromosomal genomic rearrangements. Using a zebrafish model, SPOP mutation results in a transcriptional response consistent with BRCA1 inactivation, implicating altered repair of DSB. In vitro data suggest that SPOP participates in repair of DSB, and SPOP mutation impairs homology-directed repair (HDR), instead promoting error-prone non-homologous end joining (NHEJ). Finally, SPOP mutation sensitizes prostate cancer cells to DNA damaging therapeutic agents such as PARP inhibitors. Conclusions: These results implicate SPOP as a novel participant in DSB repair, suggest that SPOP mutation drives prostate tumorigenesis in part through genomic instability, and indicate that SPOP mutant prostate cancer may be selectively responsive to DNA damaging therapeutics. Citation Format: Gunther Boysen, Christopher E. Barbieri, Davide Prandi, Sung-Suk Chae, Srilakshmi Nataraj, Mirjam Blattner, Clarisse Marotz, Limei Xu, Paola Lecca, Sagar Chhangawala, Pengbo Zou, Andrea Sboner, Francesca Demichelis, Yariv Houvras, Mark A. Rubin. SPOP mutation leads to genomic instability in prostate cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1108. doi:10.1158/1538-7445.AM2015-1108