Synergistic role of TFEB/TFE3 and mTORC1 in kidney cystogenesis and tumorigenesis.

Birt-Hogg-Dubé (BHD) and Tuberous Sclerosis (TSC) are inherited cancer syndromes associated with kidney cystogenesis and tumorigenesis and caused by mutations of the folliculin (FLCN) and TSC1/2 genes, respectively. We and others previously showed that Transcription Factors EB (TFEB) and E3 (TFE3) are the main drivers of the kidney phenotypes observed in mouse models of these conditions. These transcription factors are also responsible for the feedback hyperactivation of the mechanistic Target of Rapamycin Complex 1 (mTORC1), a known tumorigenic factor. This raises the question of whether TFEB/TFE3 exert their oncogenic activity by inducing mTORC1 or by mTORC1-independent pathways. To address this question, we generated kidney-specific mouse models in which we knocked out factors that differentially control mTORC1 and TFEB/TFE3, thus uncoupling their activities. Specifically, we generated three kidney-specific conditional knockout lines: (1) Depdc5-KO mice in which loss of GATOR1 activity leads to mTORC1 hyperactivation and TFEB/TFE3 inhibition, (2) RagC-KO mice in which TFEB/TFE3 are constitutively active and mTORC1 activity is partially inhibited due to impaired Rag heterodimer formation, and (3) Flcn/RagC double KO mice to test whether mTORC1 inhibition induced by RagC loss ameliorates the aggressive kidney phenotype of FLCN KO mice. Comparison between these models revealed that mTORC1 hyperactivation is a key driver of cystogenesis and tumorigenesis, while TFEB/TFE3 constitutive activation further enhances and accelerates pathology by establishing a transcriptional program that integrates metabolic and stress-response pathways. Together, our findings define an oncogenic mechanism by which both mTORC1 and TFEB/TFE3 hyperactivation cooperate in kidney tumorigenesis.