RESUMEN
Intrahepatic cholangiocarcinoma (ICC) is an aggressive bile duct malignancy that frequently exhibits isocitrate dehydrogenase (IDH1/IDH2) mutations. Mutant IDH (IDHm) ICC is dependent on SRC kinase for growth and survival and is hypersensitive to inhibition by dasatinib, but the molecular mechanism underlying this sensitivity is unclear. We found that dasatinib reduced p70 S6 kinase (S6K) and ribosomal protein S6 (S6), leading to substantial reductions in cell size and de novo protein synthesis. Using an unbiased phosphoproteomic screen, we identified membrane-associated guanylate kinase, WW, and PDZ domain containing 1 (MAGI1) as an SRC substrate in IDHm ICC. Biochemical and functional assays further showed that SRC inhibits a latent tumor-suppressing function of the MAGI1-protein phosphatase 2A (PP2A) complex to activate S6K/S6 signaling in IDHm ICC. Inhibiting SRC led to activation and increased access of PP2A to dephosphorylate S6K, resulting in cell death. Evidence from patient tissue and cell line models revealed that both intrinsic and extrinsic resistance to dasatinib is due to increased phospho-S6 (pS6). To block pS6, we paired dasatinib with the S6K/AKT inhibitor M2698, which led to a marked reduction in pS6 in IDHm ICC cell lines and patient-derived organoids in vitro and substantial growth inhibition in ICC patient-derived xenografts in vivo. Together, these results elucidated the mechanism of action of dasatinib in IDHm ICC, revealed a signaling complex regulating S6K phosphorylation independent of mTOR, suggested markers for dasatinib sensitivity, and described a combination therapy for IDHm ICC that may be actionable in the clinic.
Asunto(s)
Proteínas Adaptadoras Transductoras de Señales , Colangiocarcinoma , Dasatinib , Isocitrato Deshidrogenasa , Mutación , Familia-src Quinasas , Animales , Humanos , Ratones , Proteínas Adaptadoras Transductoras de Señales/metabolismo , Neoplasias de los Conductos Biliares/patología , Neoplasias de los Conductos Biliares/metabolismo , Neoplasias de los Conductos Biliares/genética , Neoplasias de los Conductos Biliares/tratamiento farmacológico , Moléculas de Adhesión Celular/metabolismo , Línea Celular Tumoral , Proliferación Celular/efectos de los fármacos , Colangiocarcinoma/tratamiento farmacológico , Colangiocarcinoma/patología , Colangiocarcinoma/metabolismo , Colangiocarcinoma/genética , Dasatinib/farmacología , Isocitrato Deshidrogenasa/metabolismo , Isocitrato Deshidrogenasa/genética , Mutación/genética , Fosforilación/efectos de los fármacos , Proteínas Quinasas S6 Ribosómicas 70-kDa/metabolismo , Transducción de Señal/efectos de los fármacos , Familia-src Quinasas/metabolismo , Familia-src Quinasas/antagonistas & inhibidores , Guanilato-Quinasas/genética , Guanilato-Quinasas/metabolismo , Proteína Fosfatasa 2/genética , Proteína Fosfatasa 2/metabolismoRESUMEN
BACKGROUND: BIRC6 is a member of the Inhibitors of Apoptosis Protein (IAP) family which is thought to protect a variety of cancer cells from apoptosis. The main objective of the present study was to investigate whether BIRC6 plays a role in prostate cancer and could be useful as a novel therapeutic target. METHODS: BIRC6 expression in cell lines was assessed using Western blot analysis and in clinical samples using immunohistochemistry of tissue microarrays. The biological significance of BIRC6 was determined by siRNA-induced reduction of BIRC6 expression in LNCaP cells followed by functional assays. RESULTS: Elevated BIRC6 protein expression was found in prostate cancer cell lines and clinical specimens as distinct from their benign counterparts. Increased BIRC6 expression was associated with Gleason 6-8 cancers and castration resistance. Reduction of BIRC6 expression in LNCaP cells led to a marked reduction in cell proliferation which was associated with an increase in apoptosis and a decrease in autophagosome formation. Doxorubicin-induced apoptosis was found to be coupled to a reduction in BIRC6 protein expression. CONCLUSION: The data suggest a role for BIRC6 in prostate cancer progression and treatment resistance, and indicate for the first time that the BIRC6 gene and its product are potentially valuable targets for treatment of prostate cancers.