RESUMEN
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.
Asunto(s)
Proteínas HSP70 de Choque Térmico , Neoplasias de la Próstata , Proteostasis , Ubiquitina-Proteína Ligasas , Ubiquitinación , Masculino , Humanos , Neoplasias de la Próstata/metabolismo , Neoplasias de la Próstata/tratamiento farmacológico , Neoplasias de la Próstata/patología , Neoplasias de la Próstata/genética , Proteínas HSP70 de Choque Térmico/metabolismo , Ubiquitina-Proteína Ligasas/metabolismo , Ubiquitina-Proteína Ligasas/genética , Ubiquitinación/efectos de los fármacos , Línea Celular Tumoral , Animales , Aurora Quinasa A/metabolismo , Aurora Quinasa A/genética , Aurora Quinasa A/antagonistas & inhibidores , Proteína Proto-Oncogénica N-Myc/metabolismo , Proteína Proto-Oncogénica N-Myc/genética , Ratones , Carcinoma Neuroendocrino/metabolismo , Carcinoma Neuroendocrino/genética , Carcinoma Neuroendocrino/tratamiento farmacológico , Carcinoma Neuroendocrino/patología , Tumores Neuroendocrinos/metabolismo , Tumores Neuroendocrinos/tratamiento farmacológico , Tumores Neuroendocrinos/genética , Tumores Neuroendocrinos/patologíaRESUMEN
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.
