The Experts below are selected from a list of 19320 Experts worldwide ranked by ideXlab platform
Geoffrey I Shapiro - One of the best experts on this subject based on the ideXlab platform.
-
abstract ct047 phase 1 dose escalation study of the CDK Inhibitor dinaciclib in combination with the parp Inhibitor veliparib in patients with advanced solid tumors
Cancer Research, 2017Co-Authors: Geoffrey I Shapiro, Khanh Do, Sara M Tolaney, John Hilton, James M Cleary, Andrew Wolanski, Brian Beardslee, Faith Hassinger, Ketki Bhushan, Elizabeth DowneyAbstract:Background: Although PARP inhibition is effective against HR repair-deficient cancers, efficacy is limited by HR proficiency, whether present de novo or as a result of acquired resistance, prompting HR disrupting strategies to sensitize tumor cells. Inhibition of CDK1 and CDK12 compromise HR by blocking BRCA1 phosphorylation, affecting recruitment to sites of DNA damage, and by reducing HR gene expression, respectively. Dinaciclib is a pan-CDK Inhibitor that inhibits both CDK1 and CDK12 at nanomolar potency. We conducted a Phase 1 study combining dinaciclib and veliparib in patients with advanced solid tumors who are not germline BRCA carriers. Methods: A 3+3 design was utilized. Veliparib was administered twice daily continuously in 28-day cycles. Dinaciclib was administered intravenously on days 8 and 22. In part 1A, escalation followed a two-dimensional schema, utilizing doses of dinaciclib between 10 - 45 mg/m2 and veliparib between 20 - 120 mg. In part 1B, veliparib was escalated between 200 mg - 400 mg with dinaciclib maintained at 30 mg/m2. PK and PD assessments were performed at baseline, after veliparib, and after the combination. Preliminary Results: Sixty-three heavily pretreated patients were enrolled in part 1A (n = 39) and 1B (n = 24). Thirty-four patients had breast or gynecologic malignancies. The MTD was 400 mg twice-daily veliparib with dinaciclib at 30 mg/m2. DLTs included G4 neutropenia > 7 days (n =1), febrile neutropenia (n = 1), mucositis (n = 1) and fatigue (n = 1). Common drug-related toxicities were neutropenia (78%), nausea (75%), fatigue (67%), electrolyte abnormalities (59%), elevated liver function tests (57%), diarrhea (52%), lymphopenia (52%), anemia (43%), dehydration (37%), anorexia (30%), vomiting (29%), hypoalbuminemia (29%), dizziness (29%), headache (22%), mucositis (18%), elevated creatinine (16%), alopecia (16%), thrombocytopenia (14%), abdominal pain (13%), insomnia (13%), and dysgeusia (11%). The median number of cycles completed was 2 (r: 1 - 10). One patient with TNBC achieved complete resolution of axillary adenopathy lasting > 8 months. Twenty-four patients (38%) had stable disease as the best response, with 9 progression-free > 4 months (TNBC, gynecologic and thymic ca). Paired tumor biopsies from one patient demonstrated reduced Ki-67 and increased gamma-H2AX staining after combination treatment compared to after veliparib alone. Conclusions: Dinaciclib administered at doses known to produce PD effects is tolerable with full dose veliparib. Anti-tumor activity is limited in non-BRCA carriers, possibly related to intermittent administration of a CDK Inhibitor with known short half-life. Additional patients are being enrolled utilizing dinaciclib in more dose-intense schedules. Citation Format: Geoffrey I. Shapiro, Khanh T. Do, Sara M. Tolaney, John F. Hilton, James M. Cleary, Andrew Wolanski, Brian Beardslee, Faith Hassinger, Ketki Bhushan, Dongpo Cai, Elizabeth Downey, Solida Pruitt-Thompson, Suzanne M. Barry, Bose Kochupurakkal, Joseph Geradts, Christine Unitt, Alan D. D9Andrea, Alona Muzikansky, Richard Piekarz, L. Austin Doyle, Jeffrey Supko. Phase 1 dose-escalation study of the CDK Inhibitor dinaciclib in combination with the PARP Inhibitor veliparib in patients with advanced solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr CT047. doi:10.1158/1538-7445.AM2017-CT047
-
abstract 1788 the CDK Inhibitor dinaciclib sensitizes triple negative breast cancer cells to parp inhibition
Cancer Research, 2013Co-Authors: Shawn F Johnson, Neil F Johnson, Benjamin Primack, Alan D Dandrea, Geoffrey I ShapiroAbstract:Background: Triple Negative Breast Cancer (TNBC) comprises 15% of all breast cancers, and has a poor prognosis relative to other breast cancer subtypes. Inhibition of poly (ADP-ribose) polymerase (PARP) causes the degeneration of single-strand DNA breaks to more lethal double-strand breaks (DSBs), and also traps PARP-DNA complexes, which must be repaired or bypassed by homologous recombination (HR). BRCA1 plays a critical role in HR and its activity is in part regulated by cyclin-dependent kinase 1 (CDK1)-mediated phosphorylation. PARP inhibition results in synthetic lethality in cells that have impaired HR, such as BRCA-deficient cells. Other CDK family members activate additional components of the HR pathway. Here, we show that HR-proficient TNBC cells can be sensitized to PARP inhibition through use of CDK inhibition to impair BRCA1 function and disrupt HR. Methods: We examined the effects of dinaciclib (CDK1, 2, 5 and 9 Inhibitor), γ-irradiation and veliparib (PARP Inhibitor) on a panel of BRCA1 wild type TNBC cell lines (MDA-MB-231, MDA-MB-468, and BT549). Levels of phospho-S1497 BRCA1 (pBRCA1; CDK phosphorylation site), γ-H2AX, and RAD51 were measured by western blot to assess effects on HR proteins. A direct assessment of DSB repair was measured using the U2OS-DR-GFP reporter system. Cell viability was measured using Cell-Titer Glo assays. Patient-derived TNBC xenograft models were established in immunocompromised NOD-SCID-IL2γ-/- mice, and implanted orthotopically into cohorts of mice for in vivo efficacy studies. Results: There was a significant reduction in total and pBRCA1 and RAD51 protein levels with increasing concentrations of dinaciclib in all TNBC cell lines. In response to 10 Gy γ-irradiation treatment, pretreatment with dinaciclib (20 nM) reduced the percentage of cells with greater than five BRCA1 foci from 54% to 5% (P Conclusion: CDK inhibition effectively inhibits HR, and renders BRCA-proficient TNBC cells sensitive to PARP inhibition. This combination represents an effective strategy for the treatment of TNBC. Citation Format: Shawn F. Johnson, Neil Johnson, David Chi, Benjamin Primack, Alan D. D9Andrea, Elgene Lim, Geoffrey I. Shapiro. The CDK Inhibitor dinaciclib sensitizes triple-negative breast cancer cells to PARP inhibition. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1788. doi:10.1158/1538-7445.AM2013-1788
-
cyclin dependent kinases CDKs and the dna damage response rationale for CDK Inhibitor chemotherapy combinations as an anticancer strategy for solid tumors
Expert Opinion on Therapeutic Targets, 2010Co-Authors: Neil F Johnson, Geoffrey I ShapiroAbstract:Importance of the field: The eukaryotic cell division cycle is a tightly regulated series of events coordinated by the periodic activation of multiple cyclin-dependent kinases (CDKs). Small-molecule CDK-Inhibitory compounds have demonstrated preclinical synergism with DNA-damaging agents in solid tumor models. An improved understanding of how CDKs regulate the DNA damage response now provides an opportunity for optimization of combinations of CDK Inhibitors and DNA damaging chemotherapy agents that can be translated to clinical settings. Areas covered in this review: Here, we discuss novel work uncovering multiple roles for CDKs in the DNA-damage-response network. First, they activate DNA damage checkpoint and repair pathways. Later their activity is turned off, resulting in cell cycle arrest, allowing time for DNA repair to occur. Recent clinical data on CDK Inhibitor–DNA-damaging agent combinations are also discussed. What the reader will gain: Readers will learn about novel areas of CDK biology, the co...
Hui Zhang - One of the best experts on this subject based on the ideXlab platform.
-
Involvement of CUL4 ubiquitin E3 ligases in regulating CDK Inhibitors Dacapo/p27Kip1 and cyclin E degradation.
Cell Cycle, 2006Co-Authors: Leigh Ann Higa, Xiaoming Yang, Jianyu Zheng, Damon Banks, Min Wu, Papia Ghosh, Hui ZhangAbstract:The CUL4 (cullin 4) proteins are the core components of a new class of ubiquitinE3 ligases that regulate replication and transcription. To examine the roles of CUL4 incell cycle regulation, we analyzed the effect of inactivation of CUL4 in both Drosophilaand human cells. We found that loss of CUL4 in Drosophila cells causes G1 cell cyclearrest and an increased protein level of the CDK Inhibitor Dacapo. Co-elimination ofDacapo with CUL4 abolishes the G1 cell arrest. In human cells, inactivation of CUL4Ainduces CDK Inhibitor p27Kip1 stabilization and G1 cell cycle arrest which is dependenton the presence of p27, suggesting that this regulatory pathway is evolutionarilyconserved. In addition, we found that the Drosophila CUL4 also regulates the proteinlevel of cyclin E independent of Dacapo. We provide evidence that human CUL4B, aparalogue of human CUL4A, is involved in cyclin E regulation. Loss of CUL4B causesthe accumulation of cyclin E without a concomitant increase of p27. The human CUL4Band cyclin E pro...
-
pten regulates the ubiquitin dependent degradation of the CDK Inhibitor p27kip1 through the ubiquitin e3 ligase scfskp2
Current Biology, 2001Co-Authors: Ramanaiah Mamillapalli, Nadia Gavrilova, Valia T Mihaylova, Lyuben M Tsvetkov, Hong Wu, Hui ZhangAbstract:Abstract The PTEN tumor suppressor acts as a phosphatase for phosphatidylinositol-3,4,5-trisphosphate (PIP3) [1, 2]. We have shown previously that PTEN negatively controls the G1/S cell cycle transition and regulates the levels of p27 KIP1 , a CDK Inhibitor [3, 4]. Recently, we and others have identified an ubiquitin E3 ligase, the SCF SKP2 complex, that mediates p27 ubiquitin-dependent proteolysis [5–7]. Here we report that PTEN and the PI 3-kinase pathway regulate p27 protein stability. PTEN-deficiency in mouse embryonic stem (ES) cells causes a decrease of p27 levels with concomitant increase of SKP2, a key component of the SCF SKP2 complex. Conversely, in human glioblastoma cells, ectopic PTEN expression leads to p27 accumulation, which is accompanied by a reduction of SKP2. We found that ectopic expression of SKP2 alone is sufficient to reverse PTEN-induced p27 accumulation, restore the kinase activity of cyclin E/CDK2, and partially overcome the PTEN-induced G1 cell cycle arrest. Consistently, recombinant SCF SKP2 complex or SKP2 protein alone can rescue the defect in p27 ubiquitination in extracts prepared from cells treated with a PI 3-kinase Inhibitor. Our findings suggest that SKP2 functions as a critical component in the PTEN/PI 3-kinase pathway for the regulation of p27 KIP1 and cell proliferation.
-
cleavage of CDK Inhibitor p21cip1 waf1 by caspases is an early event during dna damage induced apoptosis
Journal of Biological Chemistry, 1998Co-Authors: Jennifer L M Gervais, Prem Seth, Hui ZhangAbstract:Abstract Activation of the p53-mediated DNA damage response induces either G1 cell cycle arrest or apoptosis. The G1 cell cycle arrest is in part caused by the p53-dependent transcriptional activation of the CDK Inhibitor, p21Cip1/Waf1. We report here that human p21 protein is rapidly induced but selectively cleaved during the apoptotic response to γ-irradiation. Such an event occurred early, well before the morphological appearance of apoptosis. Ectopical expression of p53 in tumor cells alone could induce p21 expression, followed by p21 cleavage and apoptosis. The cleavage of p21 could be reproduced in extracts prepared from irradiated cells or by recombinant caspase-3, suggesting that a caspase-like activity is responsible for this cleavage. p21 binds independently to both CDK2 and proliferation cell nuclear antigen (PCNA). Our studies indicated that p21 cleavage by the caspase-like activity specifically abolished its interaction with PCNA, suggesting that p21 cleavage may interfere with normal PCNA-dependent repair. Our data suggest that p21 may serve as a critical checkpoint regulator for both cell cycle arrest and apoptosis during the p53-mediated DNA damage response. Manipulation of the checkpoint regulators involved in cell cycle arrest and apoptosis may thus provide a novel strategy to cancer therapy.
Michele Pagano - One of the best experts on this subject based on the ideXlab platform.
-
deregulated degradation of the CDK Inhibitor p27 and malignant transformation
Seminars in Cancer Biology, 2003Co-Authors: Joanna Bloom, Michele PaganoAbstract:p27 acts as a critical negative regulator of the cell cycle by inhibiting the activity of cyclin/CDK complexes during G0 and G1. Degradation of p27 is a critical event for the G1/S transition and occurs through ubiquitination by SCF Skp2 and subsequent degradation by the 26S-proteasome. A tumor suppressing function of p27 has been demonstrated in mouse models and studies of human tumors. More recent evidence suggests that Skp2, the specific recognition factor for p27 ubiquitination, has oncogenic properties. This review will focus on the regulation of p27 proteolysis and its consequences for tumorigenesis. © 2002 Elsevier Science Ltd. All rights reserved.
-
regulation of the CDK Inhibitor p27 and its deregulation in cancer
Journal of Cellular Physiology, 2000Co-Authors: Joyce M Slingerland, Michele PaganoAbstract:p27 is a cell cycle Inhibitor whose cellular abundance increases in response to many antimitogenic stimuli. In this review, we summarize the current knowledge on p27 function and its regulation by synthesis and by ubiquitin-mediated degradation. Importantly, p27 degradation is enhanced in many aggressive human tumors. The frequency with which this is observed suggests that loss of p27 may confer a growth advantage to these cancers. From a practical point of view, immunodetection of p27 in tumors may prove to be useful in the assessment of prognosis and may ultimately influence the therapy of this disease. J. Cell. Physiol. 183:10–17, 2000. © 2000 Wiley-Liss, Inc.
-
skp2 is required for ubiquitin mediated degradation of the CDK Inhibitor p27
Nature Cell Biology, 1999Co-Authors: Andrea C Carrano, Esther Eytan, Avram Hershko, Michele PaganoAbstract:Degradation of the mammalian cyclin-dependent kinase (CDK) Inhibitor p27 is required for the cellular transition from quiescence to the proliferative state. The ubiquitination and subsequent degradation of p27 depend on its phosphorylation by cyclin–CDK complexes. However, the ubiquitin–protein ligase necessary for p27 ubiquitination has not been identified. Here we show that the F-box protein SKP2 specifically recognizes p27 in a phosphorylation-dependent manner that is characteristic of an F-box-protein–substrate interaction. Furthermore, both in vivo and in vitro, SKP2 is a rate-limiting component of the machinery that ubiquitinates and degrades phosphorylated p27. Thus, p27 degradation is subject to dual control by the accumulation of both SKP2 and cyclins following mitogenic stimulation.
Gianpiero Di Leva - One of the best experts on this subject based on the ideXlab platform.
-
abstract 1850 CDK Inhibitor pha 848125 preferentially inhibits proliferation of triple negative breast cancer and synergizes with cisplatin
Cancer Research, 2018Co-Authors: Douglas G Cheung, Marta Buzzetti, Carlo M Croce, Gianpiero Di LevaAbstract:Triple-negative breast cancer (TNBC), defined by the lack of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2), is highly aggressive with a poor prognosis as it lacks targeted therapies. Several Inhibitors of the cyclin-dependent kinase 4 and 6 (CDK4/6) have been approved by the FDA for the treatment of ER-positive breast cancer. However, the effectiveness of these Inhibitors against TNBC tumors is less than expected. Here, we tested the efficacy of PHA-848125, a potent ATP-competitive CDK2 Inhibitor, on a panel of breast cancer cell lines showing a selective impaired proliferation in TNBC cells (IC50 of ER-positive MCF7 cells: 25.9 μM vs. IC50 of TNBC MDA-MB-231 cells: 430.8 nM). TNBC cells treated with PHA-848125 exhibited effects consistent with CDK2 inhibition, including G1 cell cycle arrest and reduced phosphorylation levels of the retinoblastoma protein (pRB) and CDK2. Interestingly, PHA-848125 was also effective against pRB-null TNBC cell lines, unlike other approved CDK Inhibitors. Oral administration of PHA-848125 to TNBC xenograft mice and MMTV-PyMT transgenic mice impaired both tumor growth and metastasis at a tolerable dose (40 mg/kg), but not in ER-positive xenograft mice. A combination treatment of PHA-848125 and cisplatin inhibited tumor growth and induced apoptosis synergistically in vitro and in vivo. Thus, our preclinical experiments set the rationale for the clinical evaluation of PHA-848125, either alone or in combination with cisplatin, for the treatment of TNBC. Citation Format: Douglas G. Cheung, Marta Buzzetti, Carlo M. Croce, Gianpiero di Leva. CDK Inhibitor PHA-848125 preferentially inhibits proliferation of triple negative breast cancer and synergizes with cisplatin [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1850.
Neil F Johnson - One of the best experts on this subject based on the ideXlab platform.
-
abstract 1788 the CDK Inhibitor dinaciclib sensitizes triple negative breast cancer cells to parp inhibition
Cancer Research, 2013Co-Authors: Shawn F Johnson, Neil F Johnson, Benjamin Primack, Alan D Dandrea, Geoffrey I ShapiroAbstract:Background: Triple Negative Breast Cancer (TNBC) comprises 15% of all breast cancers, and has a poor prognosis relative to other breast cancer subtypes. Inhibition of poly (ADP-ribose) polymerase (PARP) causes the degeneration of single-strand DNA breaks to more lethal double-strand breaks (DSBs), and also traps PARP-DNA complexes, which must be repaired or bypassed by homologous recombination (HR). BRCA1 plays a critical role in HR and its activity is in part regulated by cyclin-dependent kinase 1 (CDK1)-mediated phosphorylation. PARP inhibition results in synthetic lethality in cells that have impaired HR, such as BRCA-deficient cells. Other CDK family members activate additional components of the HR pathway. Here, we show that HR-proficient TNBC cells can be sensitized to PARP inhibition through use of CDK inhibition to impair BRCA1 function and disrupt HR. Methods: We examined the effects of dinaciclib (CDK1, 2, 5 and 9 Inhibitor), γ-irradiation and veliparib (PARP Inhibitor) on a panel of BRCA1 wild type TNBC cell lines (MDA-MB-231, MDA-MB-468, and BT549). Levels of phospho-S1497 BRCA1 (pBRCA1; CDK phosphorylation site), γ-H2AX, and RAD51 were measured by western blot to assess effects on HR proteins. A direct assessment of DSB repair was measured using the U2OS-DR-GFP reporter system. Cell viability was measured using Cell-Titer Glo assays. Patient-derived TNBC xenograft models were established in immunocompromised NOD-SCID-IL2γ-/- mice, and implanted orthotopically into cohorts of mice for in vivo efficacy studies. Results: There was a significant reduction in total and pBRCA1 and RAD51 protein levels with increasing concentrations of dinaciclib in all TNBC cell lines. In response to 10 Gy γ-irradiation treatment, pretreatment with dinaciclib (20 nM) reduced the percentage of cells with greater than five BRCA1 foci from 54% to 5% (P Conclusion: CDK inhibition effectively inhibits HR, and renders BRCA-proficient TNBC cells sensitive to PARP inhibition. This combination represents an effective strategy for the treatment of TNBC. Citation Format: Shawn F. Johnson, Neil Johnson, David Chi, Benjamin Primack, Alan D. D9Andrea, Elgene Lim, Geoffrey I. Shapiro. The CDK Inhibitor dinaciclib sensitizes triple-negative breast cancer cells to PARP inhibition. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1788. doi:10.1158/1538-7445.AM2013-1788
-
cyclin dependent kinases CDKs and the dna damage response rationale for CDK Inhibitor chemotherapy combinations as an anticancer strategy for solid tumors
Expert Opinion on Therapeutic Targets, 2010Co-Authors: Neil F Johnson, Geoffrey I ShapiroAbstract:Importance of the field: The eukaryotic cell division cycle is a tightly regulated series of events coordinated by the periodic activation of multiple cyclin-dependent kinases (CDKs). Small-molecule CDK-Inhibitory compounds have demonstrated preclinical synergism with DNA-damaging agents in solid tumor models. An improved understanding of how CDKs regulate the DNA damage response now provides an opportunity for optimization of combinations of CDK Inhibitors and DNA damaging chemotherapy agents that can be translated to clinical settings. Areas covered in this review: Here, we discuss novel work uncovering multiple roles for CDKs in the DNA-damage-response network. First, they activate DNA damage checkpoint and repair pathways. Later their activity is turned off, resulting in cell cycle arrest, allowing time for DNA repair to occur. Recent clinical data on CDK Inhibitor–DNA-damaging agent combinations are also discussed. What the reader will gain: Readers will learn about novel areas of CDK biology, the co...