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PARP and CDK4/6 Inhibitor Combination Therapy Induces Apoptosis and Suppresses Neuroendocrine Differentiation in Prostate Cancer.

ABSTRACT: We analyzed the efficacy and mechanistic interactions of PARP inhibition (PARPi; olaparib) and CDK4/6 inhibition (CDK4/6i; palbociclib or abemaciclib) combination therapy in castration-resistant prostate cancer (CRPC) and neuroendocrine prostate cancer (NEPC) models. We demonstrated that combined olaparib and palbociblib or abemaciclib treatment resulted in synergistic suppression of the p-Rb1-E2F1 signaling axis at the transcriptional and posttranslational levels, leading to disruption of cell-cycle progression and inhibition of E2F1 gene targets, including genes involved in DDR signaling/damage repair, antiapoptotic BCL-2 family members (BCL-2 and MCL-1), CDK1, and neuroendocrine differentiation (NED) markers in vitro and in vivo In addition, olaparib + palbociclib or olaparib + abemaciclib combination treatment resulted in significantly greater growth inhibition and apoptosis than either single agent alone. We further showed that PARPi and CDK4/6i combination treatment-induced CDK1 inhibition suppressed p-S70-BCL-2 and increased caspase cleavage, while CDK1 overexpression effectively prevented the downregulation of p-S70-BCL-2 and largely rescued the combination treatment-induced cytotoxicity. Our study defines a novel combination treatment strategy for CRPC and NEPC and demonstrates that combination PARPi and CDK4/6i synergistically promotes suppression of the p-Rb1-E2F1 axis and E2F1 target genes, including CDK1 and NED proteins, leading to growth inhibition and increased apoptosis in vitro and in vivo Taken together, our results provide a molecular rationale for PARPi and CDK4/6i combination therapy and reveal mechanism-based clinical trial opportunities for men with NEPC.

SUBMITTER: Wu C

PROVIDER: S-EPMC8456452 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Cyclooxygenase-2 (COX-2) is an inducible enzyme involved in the conversion of arachadonic acid to prostaglandins and other eicosaniods. Persistent COX-2 expression is associated with multiple forms of cancer.Therefore, there is much interest in COX-2 specific, non-steroidal anti-inflammatory drug use for cancer chemotherapy. The mechanism by which these drugs inhibit tumor growth and progression is unclear, and our knowledge about their potential to prevent or treat prostate cancer is inadequate.The effects of NS-398, a selective COX-2 inhibitor, on human prostate carcinoma cell line LNCaP and the LNCaP subline C4-2b were investigated in this study. NS-398 effects on apoptosis were examined by caspase-3 activity increase, as well as internucleosomal cleavage. ELISA and PCR were used to determine inhibitor effects on macrophage migration inhibitory factor (MIF) and COX-2 production.At 10 microM, NS-398 treatment resulted in increased production of COX-2 and the pro-inflammatory cytokine, MIF by the C4-2b LNCaP subline. NS-398 (10 microM) induces apoptosis in LNCaP cells, but not in the more aggressive, androgen-unresponsive C4-2b cells. The C4-2b cells were observed to continue to proliferate when treated with NS-398 and continued to retain malignant phenotype characteristics. NS-398 treatment resulted in C4-2b cell differentiation into an unusual neuroendocrine-like cell. These neuroendocrine-like cells produced both epithelial (cytokeratin 18 and prostate specific antigen) and neuronal (neuron-specific enolase and chromogranin A) proteins. Furthermore, this C4-2b cellular response to NS-398 was mediated by NF-kappa beta transcription factor activation.These data suggest that COX-2 inhibition induces NF-kappa beta transcription factor activation, which subsequently induces pro-inflammatory protein expression (COX-2 and MIF) and neuroendocrine differentiation in the LNCaP C4-2b subline. These data provide further evidence that pro-inflammatory protein expression may play an important role in prostate cancer progression.

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PARP and CDK4/6 Inhibitor Combination Therapy Induces Apoptosis and Suppresses Neuroendocrine Differentiation in Prostate Cancer.

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