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Andrew S. Kraft - One of the best experts on this subject based on the ideXlab platform.
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PIM1 kinase regulates c kit gene translation
Experimental hematology & oncology, 2016Co-Authors: Bo Cen, Andrew S. Kraft, Houjian Cai, Jin H Song, Yubin KangAbstract:Receptor tyrosine kinase, c-Kit (CD117) plays a pivotal role in the maintenance and expansion of hematopoietic stem/progenitor cells (HSPCs). Additionally, over-expression and/or mutational activation of c-Kit have been implicated in numerous malignant diseases including acute myeloid leukemia. However, the translational regulation of c-Kit expression remains largely unknown. We demonstrated that loss of PIM1 led to specific down-regulation of c-Kit expression in HSPCs of PIM1−/− mice and PIM1−/−2−/−3−/− triple knockout (TKO) mice, and resulted in attenuated ERK and STAT3 signaling in response to stimulation with stem cell factor. Transduction of c-Kit restored the defects in colony forming capacity seen in HSPCs from PIM1−/− and TKO mice. Pharmacologic inhibition and genetic modification studies using human megakaryoblastic leukemia cells confirmed the regulation of c-Kit expression by PIM1 kinase: i.e., PIM1-specific shRNA knockdown down-regulated the expression of c-Kit whereas overexpression of PIM1 up-regulated the expression of c-Kit. Mechanistically, inhibition or knockout of PIM1 kinase did not affect the transcription of c-Kit gene. PIM1 kinase enhanced c-Kit 35S methionine labeling and increased the incorporation of c-Kit mRNAs into the polysomes and monosomes, demonstrating that PIM1 kinase regulates c-Kit expression at the translational level. Our study provides the first evidence that PIM1 regulates c-Kit gene translation and has important implications in hematopoietic stem cell transplantation and cancer treatment.
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regulation of prostate stromal fibroblasts by the PIM1 protein kinase
Cellular Signalling, 2015Co-Authors: Marina Zemskova, Bo Cen, Jin H Song, Javier Cerdainfante, Viviana P Montecinos, Andrew S. KraftAbstract:The PIM1 oncogene is over-expressed in human prostate cancer epithelial cells. Importantly, we observe that in human hyperplastic and cancerous prostate glands PIM1 is also markedly elevated in prostate fibroblasts, suggesting an important role for this kinase in epithelial/stromal crosstalk. The ability of PIM1 to regulate the biologic activity of stromal cells is demonstrated by the observation that expression of PIM1 kinase in human prostate fibroblasts increases the level and secretion of the extracellular matrix molecule, collagen 1A1 (COL1A1), the pro-inflammatory chemokine CCL5, and the platelet-derived growth factor receptors (PDGFR). PIM1 is found to regulate the transcription of CCL5. In co-cultivation assays where PIM1 over-expressing fibroblasts are grown with BPH1 prostate epithelial cells, PIM1 activity markedly enhances the ability of these fibroblasts to differentiate into myofibroblasts and express known markers of cancer-associated fibroblasts (CAFs). This differentiation can be reversed by the addition of small molecule PIM kinase inhibitors. Western blots demonstrate that PIM1 expression in prostate fibroblasts stimulates the phosphorylation of molecules that regulate 5'Cap driven protein translation, including 4EBP1 and eIF4B. Consistent with the hypothesis that the kinase controls translation of specific mRNAs in prostate fibroblasts, we demonstrate that PIM1 expression markedly increases the level of COL1A1 and PDGFRβ mRNA bound to polysomes. Together these results point on PIM1 as a novel factor in regulation of the phenotype and differentiation of fibroblasts in prostate cancer by controlling both the transcription and translation of specific mRNAs.
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PIM1 serine threonine kinase regulates the number and functions of murine hematopoietic stem cells
Stem Cells, 2013Co-Authors: Yingwei Lin, Sandeep Mahajan, Yong Wang, Andrew S. Kraft, Joshua Kellner, Yubin KangAbstract:The genes and pathways that govern the functions and expansion of hematopoietic stem cells (HSC) are not completely understood. In this study, we investigated the roles of serine/threonine Pim kinases in hematopoiesis in mice. We generated PIM1 transgenic mice (PIM1-Tx) overexpressing human PIM1 driven by vav hematopoietic promoter/regulatory elements. Compared to wild-type littermates, PIM1-Tx mice showed enhanced hematopoiesis as demonstrated by increased numbers of Lin(-) Sca-1 (+) c-Kit (+) (LSK) hematopoietic stem/progenitor cells and cobblestone area forming cells, higher BrdU incorporation in long-term HSC population, and a better ability to reconstitute lethally irradiated mice. We then extended our study using PIM1(-/-), Pim2(-/-), Pim3(-/-) single knockout (KO) mice. HSCs from PIM1(-/-) KO mice showed impaired long-term hematopoietic repopulating capacity in secondary and competitive transplantations. Interestingly, these defects were not observed in HSCs from Pim2(-/-) or Pim3(-/-) KO mice. Limiting dilution competitive transplantation assay estimated that the frequency of LSKCD34(-) HSCs was reduced by approximately 28-fold in PIM1(-/-) KO mice compared to wild-type littermates. Mechanistic studies demonstrated an important role of PIM1 kinase in regulating HSC cell proliferation and survival. Finally, our polymerase chain reaction (PCR) array and confirmatory real-time PCR (RT-PCR) studies identified several genes including Lef-1, Pax5, and Gata1 in HSCs that were affected by PIM1 deletion. Our data provide the first direct evidence for the important role of PIM1 kinase in the regulation of HSCs. Our study also dissects out the relative role of individual Pim kinase in HSC functions and regulation.
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p53 dependent induction of prostate cancer cell senescence by the PIM1 protein kinase
Molecular Cancer Research, 2010Co-Authors: Marina Zemskova, Michael B. Lilly, Yingwei Lin, Jin H Song, Andrew S. KraftAbstract:The PIM family of serine threonine protein kinases plays an important role in regulating both the growth and transformation of malignant cells. However, in a cell line-dependent manner, overexpression of PIM1 can inhibit cell and tumor growth. In 22Rv1 human prostate cells, but not in Du145 or RWPE-2, PIM1 overexpression was associated with marked increases in cellular senescence, as shown by changes in the levels of beta-galactosidase (SA-beta-Gal), p21, interleukin (IL)-6 and IL-8 mRNA and protein. During early cell passages, PIM1 induced cellular polyploidy. As the passage number increased, markers of DNA damage, including the level of gammaH2AX and CHK2 phosphorylation, were seen. Coincident with these DNA damage markers, the level of p53 protein and genes transcriptionally activated by p53, such as p21, TP53INP1, and DDIT4, increased. In these 22Rv1 cells, the induction of p53 protein was associated not only with senescence but also with a significant level of apoptosis. The importance of the p53 pathway to PIM1-driven cellular senescence was further shown by the observation that expression of dominant-negative p53 or shRNA targeting p21 blocked the PIM1-induced changes in the DNA damage response and increases in SA-beta-Gal activity. Likewise, in a subcutaneous tumor model, PIM1-induced senescence was rescued when the p53-p21 pathways are inactivated. Based on these results, PIM1 will have its most profound effects on tumorigenesis in situations where the senescence response is inactivated.
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PIM1 protein kinase regulates pras40 phosphorylation and mtor activity in fdcp1 cells
Cancer Biology & Therapy, 2009Co-Authors: Fengxue Zhang, Michael B. Lilly, Sandeep Mahajan, Zanna Beharry, Thurl E Harris, Charles D Smith, Andrew S. KraftAbstract:PIM1 is a serine/threonine kinase that has diverse biological roles in cell survival, proliferation and differentiation. PIM1 has been implicated in early transformation and tumor progression in haematopoietic malignancies and prostate carcinomas. The ability of PIM1 to regulate these processes is thought to be in part secondary to its activity in stimulating 4EBP1 phosphorylation and enhancement of protein synthesis. Because 4EBP1 is an mTOR substrate, we have investigated how PIM1 might regulate this latter enzyme. We have examined the ability of PIM1 to modulate PRAS40, a protein known to negatively regulate mTOR activity in FDCP1 cells. Upon phosphorylation, PRAS40 dissociates from the mTOR complex and increases mTOR kinase activity. We find that enforced overexpression of PIM1 increases PRAS40 phosphorylation at Thr(246), an AKT phosphorylation site, whether grown in complete media or deprived of IL-3 and serum. The increase in PRAS40 phosphorylation was independent of AKT activation and not inhibited by wortmannin. In vitro kinase assays indicate that the PIM1 protein kinase is capable of directly phosphorylating Thr(246) in PRAS40. PIM1 protein kinase overexpression reduced the association of PRAS40 with mTOR, and increased the mTOR directed phosphorylation of 4EBP1 and p70S6Kinase. Treatment of FDCP1 cells transfected with PIM1 (FD/mpim44) with small molecule inhibitors of PIM1 kinase activity reduced both PRAS40 and 4EBP1 phosphorylation. These results suggest that PIM1 regulates mTOR activity through phosphorylation of PRAS40. Thus, increases in mTOR activity mediated by the PIM protein kinase may have the potential to control cell growth.
Michael B. Lilly - One of the best experts on this subject based on the ideXlab platform.
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p53 dependent induction of prostate cancer cell senescence by the PIM1 protein kinase
Molecular Cancer Research, 2010Co-Authors: Marina Zemskova, Michael B. Lilly, Yingwei Lin, Jin H Song, Andrew S. KraftAbstract:The PIM family of serine threonine protein kinases plays an important role in regulating both the growth and transformation of malignant cells. However, in a cell line-dependent manner, overexpression of PIM1 can inhibit cell and tumor growth. In 22Rv1 human prostate cells, but not in Du145 or RWPE-2, PIM1 overexpression was associated with marked increases in cellular senescence, as shown by changes in the levels of beta-galactosidase (SA-beta-Gal), p21, interleukin (IL)-6 and IL-8 mRNA and protein. During early cell passages, PIM1 induced cellular polyploidy. As the passage number increased, markers of DNA damage, including the level of gammaH2AX and CHK2 phosphorylation, were seen. Coincident with these DNA damage markers, the level of p53 protein and genes transcriptionally activated by p53, such as p21, TP53INP1, and DDIT4, increased. In these 22Rv1 cells, the induction of p53 protein was associated not only with senescence but also with a significant level of apoptosis. The importance of the p53 pathway to PIM1-driven cellular senescence was further shown by the observation that expression of dominant-negative p53 or shRNA targeting p21 blocked the PIM1-induced changes in the DNA damage response and increases in SA-beta-Gal activity. Likewise, in a subcutaneous tumor model, PIM1-induced senescence was rescued when the p53-p21 pathways are inactivated. Based on these results, PIM1 will have its most profound effects on tumorigenesis in situations where the senescence response is inactivated.
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PIM1 protein kinase regulates pras40 phosphorylation and mtor activity in fdcp1 cells
Cancer Biology & Therapy, 2009Co-Authors: Fengxue Zhang, Michael B. Lilly, Sandeep Mahajan, Zanna Beharry, Thurl E Harris, Charles D Smith, Andrew S. KraftAbstract:PIM1 is a serine/threonine kinase that has diverse biological roles in cell survival, proliferation and differentiation. PIM1 has been implicated in early transformation and tumor progression in haematopoietic malignancies and prostate carcinomas. The ability of PIM1 to regulate these processes is thought to be in part secondary to its activity in stimulating 4EBP1 phosphorylation and enhancement of protein synthesis. Because 4EBP1 is an mTOR substrate, we have investigated how PIM1 might regulate this latter enzyme. We have examined the ability of PIM1 to modulate PRAS40, a protein known to negatively regulate mTOR activity in FDCP1 cells. Upon phosphorylation, PRAS40 dissociates from the mTOR complex and increases mTOR kinase activity. We find that enforced overexpression of PIM1 increases PRAS40 phosphorylation at Thr(246), an AKT phosphorylation site, whether grown in complete media or deprived of IL-3 and serum. The increase in PRAS40 phosphorylation was independent of AKT activation and not inhibited by wortmannin. In vitro kinase assays indicate that the PIM1 protein kinase is capable of directly phosphorylating Thr(246) in PRAS40. PIM1 protein kinase overexpression reduced the association of PRAS40 with mTOR, and increased the mTOR directed phosphorylation of 4EBP1 and p70S6Kinase. Treatment of FDCP1 cells transfected with PIM1 (FD/mpim44) with small molecule inhibitors of PIM1 kinase activity reduced both PRAS40 and 4EBP1 phosphorylation. These results suggest that PIM1 regulates mTOR activity through phosphorylation of PRAS40. Thus, increases in mTOR activity mediated by the PIM protein kinase may have the potential to control cell growth.
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potential roles for the PIM1 kinase in human cancer a molecular and therapeutic appraisal
European Journal of Cancer, 2008Co-Authors: Nilesh Shah, Michael B. Lilly, Brendan Pang, Khay Guan Yeoh, Shannon Thorn, Chienshing Chen, Manuel SaltotellezAbstract:In vitro experiments have shown the PIM1 kinase to have diverse biological roles in cell survival, proliferation and differentiation. In humans, PIM1 is often expressed in both normal and transformed cells. The PIM1 kinase is a true oncogene implicated in early transformation and tumour progression in haematopoietic malignancies and prostate carcinomas. It is associated with aggressive subgroups of lymphoma, is a marker of poor prognosis in prostate carcinomas and has been suggested to have a role in hormone insensitivity of prostate malignancies. PIM1 has a possible role in other carcinomas with 6p21 genomic alterations. On one hand, PIM1 (due to its role in malignancy) appears to be a promising target for drug development programmes but, on the other hand, the complexity of its molecular structure has posed challenges in the development of PIM1 inhibitors. In this review we discuss PIM1 expression in human tissues (including some new data from our laboratory), its role in human malignancies, as well as the possibilities and challenges in the development of target therapy for PIM1.
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the PIM1 kinase is a critical component of a survival pathway activated by docetaxel and promotes survival of docetaxel treated prostate cancer cells
Journal of Biological Chemistry, 2008Co-Authors: Marina Zemskova, Eva Sahakian, Svetlana Bashkirova, Michael B. LillyAbstract:A defining characteristic of solid tumors is the capacity to divide aggressively and disseminate under conditions of nutrient deprivation, limited oxygen availability, and exposure to cytotoxic drugs or radiation. Survival pathways are activated within tumor cells to cope with these ambient stresses. We here describe a survival pathway activated by the anti-cancer drug docetaxel in prostate cancer cells. Docetaxel activates STAT3 phosphorylation and transcriptional activity, which in turns induces expression of the PIM1 gene, encoding a serine-threonine kinase activated by many cellular stresses. Expression of PIM1 improves survival of docetaxel-treated prostate cancer cells, and PIM1 knockdown or expression of a dominant-negative PIM1 protein sensitize cells to the cytotoxic effects of docetaxel. PIM1 in turn mediates docetaxel-induced activation of NFκB transcriptional activity, and PIM1 depends in part on RELA/p65 proteins for its prosurvival effects. The PIM1 kinase plays a critical role in this STAT3 → PIM1 → NFκB stress response pathway and serves as a target for intervention to enhance the therapeutic effects of cytotoxic drugs such as docetaxel.
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characterization of a potent and selective small molecule inhibitor of the PIM1 kinase
Molecular Cancer Therapeutics, 2007Co-Authors: Sheldon L Holder, Marina Zemskova, Chao Zhang, Ryan Bremer, Maryam Tabrizizad, Jonathan W Neidigh, Michael B. LillyAbstract:The pim-1 kinase is a true oncogene that has been implicated in the development of leukemias, lymphomas, and prostate cancer, and is the target of drug development programs. We have used experimental approaches to identify a selective, cell-permeable, small-molecule inhibitor of the pim-1 kinase to foster basic and translational studies of the enzyme. We used an ELISA-based kinase assay to screen a diversity library of potential kinase inhibitors. The flavonol quercetagetin (3,3',4',5,6,7-hydroxyflavone) was identified as a moderately potent, ATP-competitive inhibitor (IC(50), 0.34 micromol/L). Resolution of the crystal structure of PIM1 in complex with quercetagetin or two other flavonoids revealed a spectrum of binding poses and hydrogen-bonding patterns in spite of strong similarity of the ligands. Quercetagetin was a highly selective inhibitor of PIM1 compared with PIM2 and seven other serine-threonine kinases. Quercetagetin was able to inhibit PIM1 activity in intact RWPE2 prostate cancer cells in a dose-dependent manner (ED(50), 5.5 micromol/L). RWPE2 cells treated with quercetagetin showed pronounced growth inhibition at inhibitor concentrations that blocked PIM1 kinase activity. Furthermore, the ability of quercetagetin to inhibit the growth of other prostate epithelial cell lines varied in proportion to their levels of PIM1 protein. Quercetagetin can function as a moderately potent and selective, cell-permeable inhibitor of the pim-1 kinase, and may be useful for proof-of-concept studies to support the development of clinically useful PIM1 inhibitors.
Sarki A Abdulkadir - One of the best experts on this subject based on the ideXlab platform.
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rnai screen identifies a synthetic lethal interaction between PIM1 overexpression and plk1 inhibition
Clinical Cancer Research, 2014Co-Authors: Riet Van Der Meer, Sarki A Abdulkadir, Ha Yong Song, Seong Hoon Park, Meejeon RohAbstract:Purpose: To identify genes whose depletion is detrimental to PIM1-overexpressing prostate cancer cells and to validate this finding in vitro and in vivo . Experimental Design: RNAi screening was used to identify genes whose depletion is detrimental to PIM1-overexpressing cells. Our finding was validated using shRNA or PLK1-specific inhibitor BI 2536. Xenograft studies were performed using both PLK1-knockdown cells and BI 2536 to investigate the effects of PLK1 inhibition on tumorigenesis in PIM1-overexpressing cells. Finally, PLK1 and PIM1 expression patterns in human prostate tumors were examined by immunohistochemistry using tissue microarrays. Results: We identified the mitotic regulator polo-like kinase (PLK1) as a gene whose depletion is particularly detrimental to the viability of PIM1-overexpressing prostate cancer. Inhibition of PLK1 by shRNA or BI 2536 in PIM1-overexpressing prostate cancer xenograft models resulted in a dramatic inhibition of tumor progression. Notably, PIM1-overexpressing cells were more prone to mitotic arrest followed by apoptosis due to PLK1 inhibition than control cells. Furthermore, inhibition of PLK1 led to the reduction of MYC protein levels both in vitro and in vivo . Our data also suggest that PIM1 and PLK1 physically interact and PIM1 might phosphorylate PLK1. Finally, PLK1 and PIM1 are frequently co-expressed in human prostate tumors, and co-expression of PLK1 and PIM1 was significantly correlated to higher Gleason grades. Conclusions: Our findings demonstrate that PIM1-overexpressing cancer cells are particularly sensitive to PLK1 inhibition, suggesting that PIM1 might be used as a marker for identifying patients who will benefit from PLK1 inhibitor treatment. Clin Cancer Res; 20(12); 3211–21. ©2014 AACR .
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PIM1 kinase as a target in prostate cancer roles in tumorigenesis castration resistance and docetaxel resistance
Current Cancer Drug Targets, 2014Co-Authors: Sheldon L Holder, Sarki A AbdulkadirAbstract:PIM1 kinase is a serine/threonine kinase that has been shown to be overexpressed in multiple human malignancies, including prostate cancer. PIM1 phosphorylates multiple cellular substrates to inhibit apoptosis and promote cell cycle progression. Increased PIM1 can also facilitate genomic instability to promote neoplastic processes. PIM1 kinase is overexpressed in high-grade prostate intraepithelial neoplasia and in prostate cancer compared to normal prostatic tissue and benign prostate hyperplasia. Elevated PIM1 levels have been shown to be the direct result of oncogenic fusion proteins and active signal transduction pathways. In vitro and in vivo mouse studies indicate that PIM1 is weakly tumorigenic but synergizes dramatically when coexpressed with MYC. PIM1 kinase can also phosphorylate the androgen receptor (AR), thereby regulating AR degradation and function, in a low androgen environment. This finding implicates PIM1 in castration -resistant prostate cancer. Furthermore, expression of PIM1 has been shown to be increased in prostate tissue after docetaxel exposure, conferring partial resistance to docetaxel. Correlatively, decreased PIM1 levels sensitize prostate cancer cells to docetaxel treatment. Thus, PIM1 may be a target in docetaxel resistant disease. In summary, PIM1 kinase is involved in prostate tumorigenesis, castration resistance, and docetaxel resistance. Several PIM1 kinase inhibitors have been reported and are in varied stages of drug development. PIM1 is involved in multiple processes in the development and propagation of prostate cancer, thus a PIM1 kinase inhibitor may serve as an effective therapeutic agent in this prevalent disease.
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PIM1 kinase is required to maintain tumorigenicity in myc expressing prostate cancer cells
Oncogene, 2012Co-Authors: J Wang, Meejeon Roh, Philip D Anderson, Weifeng Luo, David Gius, Sarki A AbdulkadirAbstract:PIM1 kinase and MYC are commonly co-expressed in human prostate cancer and synergize to induce rapidly progressing prostate cancer in mouse models. Deficiency of the Pim kinase genes is well tolerated in vivo, suggesting that PIM1 inhibition might offer an attractive therapeutic modality for prostate cancer, particularly for MYC-expressing tumors. Here we examine the molecular consequences of PIM1 and MYC overexpression in the prostate as well as the effects of depleting PIM1 in prostate carcinoma cells with high levels of MYC. Overexpression of PIM1 in the mouse prostate induces several pro-tumorigenic genetic programs including cell cycle genes and Myc-regulated genes before the induction of any discernible pathology. PIM1 depletion by RNA interference in mouse and human prostate cancer cells decreased cellular proliferation, survival, Erk signaling and tumorigenicity even when MYC levels were not significantly altered. These results indicate that PIM1 may be necessary to maintain tumorigenicity, and further support efforts aimed at developing PIM1 inhibitors for prostate cancer therapy.
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PIM1 promotes human prostate cancer cell tumorigenicity and c myc transcriptional activity
BMC Cancer, 2010Co-Authors: Jongchan Kim, Meejeon Roh, Sarki A AbdulkadirAbstract:The serine/threonine kinase PIM1 has been implicated as an oncogene in various human cancers including lymphomas, gastric, colorectal and prostate carcinomas. In mouse models, PIM1 is known to cooperate with c-Myc to promote tumorigenicity. However, there has been limited analysis of the tumorigenic potential of PIM1 overexpression in benign and malignant human prostate cancer cells in vivo. We overexpressed PIM1 in three human prostate cell lines representing different disease stages including benign (RWPE1), androgen-dependent cancer (LNCaP) and androgen-independent cancer (DU145). We then analyzed in vitro and in vivo tumorigenicity as well as the effect of PIM1 overexpression on c-MYC transcriptional activity by reporter assays and gene expression profiling using an inducible MYC-ER system. To validate that PIM1 induces tumorigenicity and target gene expression by modulating c-MYC transcriptional activity, we inhibited c-MYC using a small molecule inhibitor (10058-F4) or RNA interference. Overexpression of PIM1 alone was not sufficient to convert the benign RWPE1 cell to malignancy although it enhanced their proliferation rates when grown as xenografts in vivo. However, PIM1 expression enhanced the in vitro and in vivo tumorigenic potentials of the human prostate cancer cell lines LNCaP and DU145. Reporter assays revealed increased c-MYC transcriptional activity in PIM1-expressing cells and mRNA expression profiling demonstrated that a large fraction of c-MYC target genes were also regulated by PIM1 expression. The c-MYC inhibitor 10058-F4 suppressed the tumorigenicity of PIM1-expressing prostate cancer cells. Interestingly, 10058-F4 treatment also led to a reduction of PIM1 protein but not mRNA. Knocking-down c-MYC using short hairpin RNA reversed the effects of PIM1 on PIM1/MYC target genes. Our results suggest an in vivo role of PIM1 in promoting prostate tumorigenesis although it displayed distinct oncogenic activities depending on the disease stage of the cell line. PIM1 promotes tumorigenicity at least in part by enhancing c-MYC transcriptional activity. We also made the novel discovery that treatment of cells with the c-MYC inhibitor 10058-F4 leads to a reduction in PIM1 protein levels.
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PIM1 kinase synergizes with c-MYC to induce advanced prostate carcinoma
Oncogene, 2010Co-Authors: J Wang, J Kim, M Roh, O E Franco, S W Hayward, M L Wills, Sarki A AbdulkadirAbstract:The oncogenic PIM1 kinase has been implicated as a cofactor for c-MYC in prostate carcinogenesis. In this study, we show that in human prostate tumors, coexpression of c-MYC and PIM1 is associated with higher Gleason grades. Using a tissue recombination model coupled with lentiviral-mediated gene transfer we find that PIM1 is weakly oncogenic in naive adult mouse prostatic epithelium. However, it cooperates dramatically with c-MYC to induce prostate cancer within 6-weeks. Importantly, c-MYC/PIM1 synergy is critically dependent on PIM1 kinase activity. c-MYC/PIM1 tumors showed increased levels of the active serine-62 (S62) phosphorylated form of c-MYC. Grafts expressing a phosphomimetic c-MYCS62D mutant had higher rates of proliferation than grafts expressing wild type c-MYC but did not form tumors like c-MYC/PIM1 grafts, indicating that PIM1 cooperativity with c-MYC in vivo involves additional mechanisms other than enhancement of c-MYC activity by S62 phosphorylation. c-MYC/PIM1-induced prostate carcinomas show evidence of neuroendocrine (NE) differentiation. Additional studies, including the identification of tumor cells coexpressing androgen receptor and NE cell markers synaptophysin and Ascl1 suggested that NE tumors arose from adenocarcinoma cells through transdifferentiation. These results directly show functional cooperativity between c-MYC and PIM1 in prostate tumorigenesis in vivo and support efforts for targeting PIM1 in prostate cancer.
Thomas Langer - One of the best experts on this subject based on the ideXlab platform.
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The ATP-dependent PIM1 protease is required for the expression of intron-containing genes in mitochondria
Genes & development, 1998Co-Authors: L Van Dyck, Walter Neupert, Thomas LangerAbstract:The ATP-dependent PIM1 protease, a Lon-like protease localized in the mitochondrial matrix, is required for mitochondrial genome integrity in yeast. Cells lacking PIM1 accumulate lesions in the mitochondrial DNA (mtDNA) and therefore lose respiratory competence. The identification of a multicopy suppressor, which stabilizes mtDNA in the absence of PIM1, enabled us to characterize novel functions of PIM1 protease during mitochondrial biogenesis. The synthesis of mitochondrially encoded cytochrome c oxidase subunit I (CoxI) and cytochrome b (Cob) is impaired in PIM1 mutants containing mtDNA. PIM1-mediated proteolysis is required for the translation of mature COXI mRNA. Moreover, deficiencies in the splicing of COXI and COB transcripts, which appear to be restricted to introns encoding mRNA maturases, were observed in cells lacking the PIM1 gene. Transcripts of COXI and COB genes harboring multiple introns are degraded in the absence of PIM1. These results establish multiple, essential functions of the ATP-dependent PIM1 protease during mitochondrial gene expression.
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Autocatalytic processing of the ATP-dependent PIM1 protease: crucial function of a pro-region for sorting to mitochondria
The EMBO journal, 1997Co-Authors: Ingrid Wagner, Walter Neupert, Luc Van Dyck, A.s. Savel'ev, Thomas LangerAbstract:The biogenesis of the ATP-dependent PIM1 protease of mitochondria was studied by mutational analysis. The ATPase and proteolytic activities of PIM1 were shown to be essential for mitochondrial function. A proteolytically inactive mutant form of PIM1 protease accumulated as a pro-form in mitochondria, revealing a two-step processing of PIM1: the matrix targeting signal is removed by the mitochondrial processing peptidase and then a pro-region of 61 amino acids is cleaved off in an autocatalytic reaction. This latter process depended on the ATP-dependent assembly of PIM1 protease subunits and can occur by an intermolecular and, most probably, also an intramolecular pathway. The respiratory competence of cells harboring mutant PIM1 protease lacking the pro-region was strongly impaired. Subcellular fractionation revealed a cytosolic localization of mutant PIM1 protease. This demonstrates the requirement for the propeptide for efficient sorting of PIM1 protease to mitochondria.
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molecular chaperones cooperate with PIM1 protease in the degradation of misfolded proteins in mitochondria
The EMBO Journal, 1994Co-Authors: Ingrid Wagner, Thomas Langer, L Van Dyck, Heike Arlt, Walter NeupertAbstract:ATP dependent proteolytic degradation of misfolded proteins in the mitochondrial matrix is mediated by the PIM1 protease and depends on the molecular chaperone proteins mt-hsp70 and Mdj1p. Chaperone function is essential to maintain misfolded proteins in a soluble state, a prerequisite for their degradation by PIM1 protease. In the absence of functional mt-hsp70 or Mdj1p misfolded proteins either remain associated with mt-hsp70 or form aggregates and thereby are no longer substrates for PIM1 protease. Mdj1p is shown to regulate the ATP dependent association of an unfolded polypeptide chain with mt-hsp70 affecting binding to as well as release from mt-hsp70. These findings establish a central role of molecular chaperone proteins in the degradation of misfolded proteins by PIM1 protease and thereby demonstrate a functional interrelation between components of the folding machinery and the proteolytic system within mitochondria.
Marina Zemskova - One of the best experts on this subject based on the ideXlab platform.
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regulation of prostate stromal fibroblasts by the PIM1 protein kinase
Cellular Signalling, 2015Co-Authors: Marina Zemskova, Bo Cen, Jin H Song, Javier Cerdainfante, Viviana P Montecinos, Andrew S. KraftAbstract:The PIM1 oncogene is over-expressed in human prostate cancer epithelial cells. Importantly, we observe that in human hyperplastic and cancerous prostate glands PIM1 is also markedly elevated in prostate fibroblasts, suggesting an important role for this kinase in epithelial/stromal crosstalk. The ability of PIM1 to regulate the biologic activity of stromal cells is demonstrated by the observation that expression of PIM1 kinase in human prostate fibroblasts increases the level and secretion of the extracellular matrix molecule, collagen 1A1 (COL1A1), the pro-inflammatory chemokine CCL5, and the platelet-derived growth factor receptors (PDGFR). PIM1 is found to regulate the transcription of CCL5. In co-cultivation assays where PIM1 over-expressing fibroblasts are grown with BPH1 prostate epithelial cells, PIM1 activity markedly enhances the ability of these fibroblasts to differentiate into myofibroblasts and express known markers of cancer-associated fibroblasts (CAFs). This differentiation can be reversed by the addition of small molecule PIM kinase inhibitors. Western blots demonstrate that PIM1 expression in prostate fibroblasts stimulates the phosphorylation of molecules that regulate 5'Cap driven protein translation, including 4EBP1 and eIF4B. Consistent with the hypothesis that the kinase controls translation of specific mRNAs in prostate fibroblasts, we demonstrate that PIM1 expression markedly increases the level of COL1A1 and PDGFRβ mRNA bound to polysomes. Together these results point on PIM1 as a novel factor in regulation of the phenotype and differentiation of fibroblasts in prostate cancer by controlling both the transcription and translation of specific mRNAs.
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p53 dependent induction of prostate cancer cell senescence by the PIM1 protein kinase
Molecular Cancer Research, 2010Co-Authors: Marina Zemskova, Michael B. Lilly, Yingwei Lin, Jin H Song, Andrew S. KraftAbstract:The PIM family of serine threonine protein kinases plays an important role in regulating both the growth and transformation of malignant cells. However, in a cell line-dependent manner, overexpression of PIM1 can inhibit cell and tumor growth. In 22Rv1 human prostate cells, but not in Du145 or RWPE-2, PIM1 overexpression was associated with marked increases in cellular senescence, as shown by changes in the levels of beta-galactosidase (SA-beta-Gal), p21, interleukin (IL)-6 and IL-8 mRNA and protein. During early cell passages, PIM1 induced cellular polyploidy. As the passage number increased, markers of DNA damage, including the level of gammaH2AX and CHK2 phosphorylation, were seen. Coincident with these DNA damage markers, the level of p53 protein and genes transcriptionally activated by p53, such as p21, TP53INP1, and DDIT4, increased. In these 22Rv1 cells, the induction of p53 protein was associated not only with senescence but also with a significant level of apoptosis. The importance of the p53 pathway to PIM1-driven cellular senescence was further shown by the observation that expression of dominant-negative p53 or shRNA targeting p21 blocked the PIM1-induced changes in the DNA damage response and increases in SA-beta-Gal activity. Likewise, in a subcutaneous tumor model, PIM1-induced senescence was rescued when the p53-p21 pathways are inactivated. Based on these results, PIM1 will have its most profound effects on tumorigenesis in situations where the senescence response is inactivated.
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the PIM1 kinase is a critical component of a survival pathway activated by docetaxel and promotes survival of docetaxel treated prostate cancer cells
Journal of Biological Chemistry, 2008Co-Authors: Marina Zemskova, Eva Sahakian, Svetlana Bashkirova, Michael B. LillyAbstract:A defining characteristic of solid tumors is the capacity to divide aggressively and disseminate under conditions of nutrient deprivation, limited oxygen availability, and exposure to cytotoxic drugs or radiation. Survival pathways are activated within tumor cells to cope with these ambient stresses. We here describe a survival pathway activated by the anti-cancer drug docetaxel in prostate cancer cells. Docetaxel activates STAT3 phosphorylation and transcriptional activity, which in turns induces expression of the PIM1 gene, encoding a serine-threonine kinase activated by many cellular stresses. Expression of PIM1 improves survival of docetaxel-treated prostate cancer cells, and PIM1 knockdown or expression of a dominant-negative PIM1 protein sensitize cells to the cytotoxic effects of docetaxel. PIM1 in turn mediates docetaxel-induced activation of NFκB transcriptional activity, and PIM1 depends in part on RELA/p65 proteins for its prosurvival effects. The PIM1 kinase plays a critical role in this STAT3 → PIM1 → NFκB stress response pathway and serves as a target for intervention to enhance the therapeutic effects of cytotoxic drugs such as docetaxel.
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characterization of a potent and selective small molecule inhibitor of the PIM1 kinase
Molecular Cancer Therapeutics, 2007Co-Authors: Sheldon L Holder, Marina Zemskova, Chao Zhang, Ryan Bremer, Maryam Tabrizizad, Jonathan W Neidigh, Michael B. LillyAbstract:The pim-1 kinase is a true oncogene that has been implicated in the development of leukemias, lymphomas, and prostate cancer, and is the target of drug development programs. We have used experimental approaches to identify a selective, cell-permeable, small-molecule inhibitor of the pim-1 kinase to foster basic and translational studies of the enzyme. We used an ELISA-based kinase assay to screen a diversity library of potential kinase inhibitors. The flavonol quercetagetin (3,3',4',5,6,7-hydroxyflavone) was identified as a moderately potent, ATP-competitive inhibitor (IC(50), 0.34 micromol/L). Resolution of the crystal structure of PIM1 in complex with quercetagetin or two other flavonoids revealed a spectrum of binding poses and hydrogen-bonding patterns in spite of strong similarity of the ligands. Quercetagetin was a highly selective inhibitor of PIM1 compared with PIM2 and seven other serine-threonine kinases. Quercetagetin was able to inhibit PIM1 activity in intact RWPE2 prostate cancer cells in a dose-dependent manner (ED(50), 5.5 micromol/L). RWPE2 cells treated with quercetagetin showed pronounced growth inhibition at inhibitor concentrations that blocked PIM1 kinase activity. Furthermore, the ability of quercetagetin to inhibit the growth of other prostate epithelial cell lines varied in proportion to their levels of PIM1 protein. Quercetagetin can function as a moderately potent and selective, cell-permeable inhibitor of the pim-1 kinase, and may be useful for proof-of-concept studies to support the development of clinically useful PIM1 inhibitors.
