Inactivation of the PBRM1 tumor suppressor gene amplifies the HIF-response in VHL−/− clear cell renal carcinoma

Menée in vitro et in vivo sur des modèles de carcinome rénal à cellules claires n'exprimant pas le gène VHL, cette étude met en évidence des mécanismes par lesquels des mutations inactivant le gène suppresseur de tumeurs PBRM1 favorisent le développement de la maladie

Résumé en anglais

Most clear cell renal carcinomas (ccRCCs) are initiated by somatic inactivation of the VHL tumor suppressor gene. The VHL gene product, pVHL, is the substrate recognition unit of an ubiquitin ligase that targets the HIF transcription factor for proteasomal degradation; inappropriate expression of HIF target genes drives renal carcinogenesis. Loss of pVHL is not sufficient, however, to cause ccRCC. Additional cooperating genetic events, including intragenic mutations and copy number alterations, are required. Common examples of the former are loss-of-function mutations of the PBRM1 and BAP1 tumor suppressor genes, which occur in a mutually exclusive manner in ccRCC and define biologically distinct subsets of ccRCC. PBRM1 encodes the Polybromo- and BRG1-associated factors-containing complex (PBAF) chromatin remodeling complex component BRG1-associated factor 180 (BAF180). Here we identified ccRCC lines whose ability to proliferate in vitro and in vivo is sensitive to wild-type BAF180, but not a tumor-associated BAF180 mutant. Biochemical and functional studies linked growth suppression by BAF180 to its ability to form a canonical PBAF complex containing BRG1 that dampens the HIF transcriptional signature.