RESUMO
N-Myc is a key driver of neuroblastoma and neuroendocrine prostate cancer (NEPC). One potential way to circumvent the challenge of undruggable N-Myc is to target the protein homeostasis (proteostasis) system that maintains N-Myc levels. Here, we identify heat shock protein 70 (HSP70) as a top partner of N-Myc, which binds a conserved "SELILKR" motif and prevents the access of E3 ubiquitin ligase, STIP1 homology and U-box containing protein 1 (STUB1), possibly through steric hindrance. When HSP70's dwell time on N-Myc is increased by treatment with the HSP70 allosteric inhibitor, STUB1 is in close proximity with N-Myc and becomes functional to promote N-Myc ubiquitination on the K416 and K419 sites and forms polyubiquitination chains linked by the K11 and K63 sites. Notably, HSP70 inhibition significantly suppressed NEPC tumor growth, increased the efficacy of aurora kinase A (AURKA) inhibitors, and limited the expression of neuroendocrine-related pathways.
Assuntos
Proteínas de Choque Térmico HSP70 , Neoplasias da Próstata , Proteostase , Ubiquitina-Proteína Ligases , Ubiquitinação , Masculino , Humanos , Neoplasias da Próstata/metabolismo , Neoplasias da Próstata/tratamento farmacológico , Neoplasias da Próstata/patologia , Neoplasias da Próstata/genética , Proteínas de Choque Térmico HSP70/metabolismo , Ubiquitina-Proteína Ligases/metabolismo , Ubiquitina-Proteína Ligases/genética , Ubiquitinação/efeitos dos fármacos , Linhagem Celular Tumoral , Animais , Aurora Quinase A/metabolismo , Aurora Quinase A/genética , Aurora Quinase A/antagonistas & inibidores , Proteína Proto-Oncogênica N-Myc/metabolismo , Proteína Proto-Oncogênica N-Myc/genética , Camundongos , Carcinoma Neuroendócrino/metabolismo , Carcinoma Neuroendócrino/genética , Carcinoma Neuroendócrino/tratamento farmacológico , Carcinoma Neuroendócrino/patologia , Tumores Neuroendócrinos/metabolismo , Tumores Neuroendócrinos/tratamento farmacológico , Tumores Neuroendócrinos/genética , Tumores Neuroendócrinos/patologiaRESUMO
Olaparib is a pioneering PARP inhibitor (PARPi) approved for treating castration-resistant prostate cancer (CRPC) tumors harboring DNA repair defects, but clinical resistance has been documented. To study acquired resistance, we developed Olaparib-resistant (OlapR) cell lines through chronic Olaparib treatment of LNCaP and C4-2B cell lines. Here, we found that IGFBP3 is highly expressed in acquired (OlapR) and intrinsic (Rv1) models of Olaparib resistance. We show that IGFBP3 expression promotes Olaparib resistance by enhancing DNA repair capacity through activation of EGFR and DNA-PKcs. IGFBP3 depletion enhances efficacy of Olaparib by promoting DNA damage accumulation and subsequently, cell death in resistant models. Mechanistically, we show that silencing IGFBP3 or EGFR expression reduces cell viability and resensitizes OlapR cells to Olaparib treatment. Inhibition of EGFR by Gefitinib suppressed growth of OlapR cells and improved Olaparib sensitivity, thereby phenocopying IGFBP3 inhibition. Collectively, our results highlight IGFBP3 and EGFR as critical mediators of Olaparib resistance.