RESUMEN
UNLABELLED: The signaling mechanisms between prostate cancer cells and infiltrating immune cells may illuminate novel therapeutic approaches. Here, utilizing a prostate adenocarcinoma model driven by loss of Pten and Smad4, we identify polymorphonuclear myeloid-derived suppressor cells (MDSC) as the major infiltrating immune cell type, and depletion of MDSCs blocks progression. Employing a novel dual reporter prostate cancer model, epithelial and stromal transcriptomic profiling identified CXCL5 as a cancer-secreted chemokine to attract CXCR2-expressing MDSCs, and, correspondingly, pharmacologic inhibition of CXCR2 impeded tumor progression. Integrated analyses identified hyperactivated Hippo-YAP signaling in driving CXCL5 upregulation in cancer cells through the YAP-TEAD complex and promoting MDSC recruitment. Clinicopathologic studies reveal upregulation and activation of YAP1 in a subset of human prostate tumors, and the YAP1 signature is enriched in primary prostate tumor samples with stronger expression of MDSC-relevant genes. Together, YAP-driven MDSC recruitment via heterotypic CXCL5-CXCR2 signaling reveals an effective therapeutic strategy for advanced prostate cancer. SIGNIFICANCE: We demonstrate a critical role of MDSCs in prostate tumor progression and discover a cancer cell nonautonomous function of the Hippo-YAP pathway in regulation of CXCL5, a ligand for CXCR2-expressing MDSCs. Pharmacologic elimination of MDSCs or blocking the heterotypic CXCL5-CXCR2 signaling circuit elicits robust antitumor responses and prolongs survival.
Asunto(s)
Quimiocina CXCL5/genética , Células Mieloides/inmunología , Fosfohidrolasa PTEN/deficiencia , Neoplasias de la Próstata/inmunología , Proteína Smad4/deficiencia , Proteínas Adaptadoras Transductoras de Señales/genética , Proteínas Adaptadoras Transductoras de Señales/metabolismo , Animales , Línea Celular Tumoral , Quimiocina CXCL5/metabolismo , Progresión de la Enfermedad , Vía de Señalización Hippo , Humanos , Masculino , Ratones , Fosfoproteínas/genética , Fosfoproteínas/metabolismo , Neoplasias de la Próstata/genética , Neoplasias de la Próstata/patología , Proteínas Serina-Treonina Quinasas/genética , Proteínas Serina-Treonina Quinasas/metabolismo , Receptores de Interleucina-8B/genética , Receptores de Interleucina-8B/metabolismo , Transducción de Señal , Factores de Transcripción , Proteínas Señalizadoras YAPRESUMEN
Following mutations in BRAF and NRAS, the RAC1 c.85C>T single-nucleotide variant (SNV) encoding P29S amino acid change represents the next most frequently observed protein-coding hotspot mutation in melanoma. However, the biologic and clinical significance of the RAC1 P29S somatic mutation in approximately 4% to 9% of patients remains unclear. Here, we demonstrate that melanoma cell lines possessing the RAC1 hotspot variant are resistant to RAF inhibitors (vemurafenib and dabrafenib). Enforced expression of RAC1 P29S in sensitive BRAF-mutant melanoma cell lines confers resistance manifested by increased viability, decreased apoptosis, and enhanced tumor growth in vivo upon treatment with RAF inhibitors. Conversely, RNAi-mediated silencing of endogenous RAC1 P29S in a melanoma cell line with a co-occurring BRAF V600 mutation increased sensitivity to vemurafenib and dabrafenib. Our results suggest RAC1 P29S status may offer a predictive biomarker for RAF inhibitor resistance in melanoma patients, where it should be evaluated clinically.