RESUMO
Autophagy promotes tumor growth by generating nutrients from the degradation of intracellular structures. Here we establish, using shRNAs, a dominant-negative mutant, and a pharmacologic inhibitor, mefenamic acid (MFA), that the Transient Receptor Potential Melastatin 3 (TRPM3) channel promotes the growth of clear cell renal cell carcinoma (ccRCC) and stimulates MAP1LC3A (LC3A) and MAP1LC3B (LC3B) autophagy. Increased expression of TRPM3 in RCC leads to Ca(2+) influx, activation of CAMKK2, AMPK, and ULK1, and phagophore formation. In addition, TRPM3 Ca(2+) and Zn(2+) fluxes inhibit miR-214, which directly targets LC3A and LC3B. The von Hippel-Lindau tumor suppressor (VHL) represses TRPM3 directly through miR-204 and indirectly through another miR-204 target, Caveolin 1 (CAV1).
Assuntos
Autofagia , Carcinoma de Células Renais/patologia , Neoplasias Renais/patologia , MicroRNAs/fisiologia , Canais de Cátion TRPM/genética , Animais , Carcinoma de Células Renais/genética , Carcinoma de Células Renais/metabolismo , Caveolina 1/metabolismo , Linhagem Celular Tumoral , Regulação Neoplásica da Expressão Gênica , Células HEK293 , Humanos , Neoplasias Renais/genética , Camundongos Nus , Transplante de Neoplasias , Oncogenes , Interferência de RNA , Canais de Cátion TRPM/metabolismo , Carga Tumoral , Proteína Supressora de Tumor Von Hippel-Lindau/metabolismoRESUMO
Von Hippel-Lindau tumor suppressor (VHL) is lost in the majority of clear cell renal cell carcinomas (ccRCC). Folliculin (FLCN) is a tumor suppressor whose function is lost in Birt-Hogg-Dubé syndrome (BHD), a disorder characterized by renal cancer of multiple histological types including clear cell carcinoma, cutaneous fibrofolliculoma, and pneumothorax. Here we explored whether there is connection between VHL and FLCN in clear cell renal carcinoma cell lines and tumors. We demonstrate that VHL regulates expression of FLCN at the mRNA and protein levels in RCC cell lines, and that FLCN protein expression is decreased in human ccRCC tumors with VHL loss, as compared with matched normal kidney tissue. Knockdown of FLCN results in increased formation of tumors by RCC cells with wild-type VHL in orthotopic xenografts in nude mice, an indication that FLCN plays a role in the tumor-suppressing activity of VHL. Interestingly, FLCN, similarly to VHL, is necessary for the activity of LC3C-mediated autophagic program that we have previously characterized as contributing to the tumor suppressing activity of VHL. The results show the existence of functional crosstalk between two major tumor suppressors in renal cancer, VHL and FLCN, converging on regulation of autophagy.
Assuntos
Estrona/metabolismo , Neoplasias Renais/metabolismo , Proteína Supressora de Tumor Von Hippel-Lindau/metabolismo , Animais , Autofagia/genética , Autofagia/fisiologia , Western Blotting , Estrona/genética , Humanos , Técnicas In Vitro , Neoplasias Renais/genética , Camundongos , Camundongos Nus , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Proteína Supressora de Tumor Von Hippel-Lindau/genéticaRESUMO
The von Hippel-Lindau tumor-suppressor gene (VHL) is lost in most clear cell renal cell carcinomas (ccRCC). Here, using human ccRCC specimens, VHL-deficient cells, and xenograft models, we show that miR-204 is a VHL-regulated tumor suppressor acting by inhibiting macroautophagy, with MAP1LC3B (LC3B) as a direct and functional target. Of note, higher tumor grade of human ccRCC was correlated with a concomitant decrease in miR-204 and increase in LC3B levels, indicating that LC3B-mediated macroautophagy is necessary for RCC progression. VHL, in addition to inducing endogenous miR-204, triggered the expression of LC3C, an HIF-regulated LC3B paralog, that suppressed tumor growth. These data reveal a function of VHL as a tumor-suppressing regulator of autophagic programs.