TMEM106B drives lung cancer metastasis by inducing TFEB-dependent lysosome synthesis and secretion of cathepsins

Metastatic lung cancer is the leading cause of cancer-associated mortality worldwide, therefore necessitating novel approaches to identify specific genetic drivers for lung cancer progression and metastasis. We recently performed an in vivo gain-of-function genetic screen to identify driver genes of lung cancer metastasis. In the study reported here, we identify TMEM106B as a primary robust driver of lung cancer metastasis. Ectopic expression of TMEM106B could significantly promote the synthesis of enlarged vesicular lysosomes that are laden with elevated levels of active cathepsins. In a TFEB-dependent manner, TMEM106B could modulate the expression of lysosomal genes of the coordinated lysosomal expression and regulation (CLEAR) pathway in lung cancer cells and patient samples. We also demonstrate that TMEM106B-induced lysosomes undergo calcium-dependent exocytosis, thereby releasing active lysosomal cathepsins necessary for TMEM106B-mediated cancer cell invasion and metastasis in vivo, which could be therapeutically prevented by pharmacological inhibition of cathepsins. Further, in TCGA LUAD data sets, 19% of patients show elevated expression of TMEM106B, which predicts for poor disease-free and overall-survival.