The human vault RNA enhances tumorigenesis and chemoresistance through the lysosome
The small non-coding vault RNA (vtRNA) 1-1 has been shown to confer apoptosis resistance in several malignant cell lines and also to modulate the autophagic flux in hepatocytes, thus highlighting its pro-survival role. Here we describe a new function of vtRNA1-1 in regulating in vitro and in vivo tumor cell proliferation, tumorigenesis and chemoresistance. By activating extracellular signal-regulated kinases (ERK 1/2), vtRNA1-1 knock-out (KO) inhibits transcription factor EB (TFEB), leading to a downregulation of the coordinated lysosomal expression and regulation (CLEAR) network genes and lysosomal compartment dysfunction. Pro-tumorigenic pathways dysregulation and decreased lysosome functionality potentiate the anticancer effect of conventional targeted cancer drugs in the absence of vtRNA1-1. Finally, vtRNA1-1 KO-reduced lysosomotropism, together with a higher intracellular compound availability, significantly reduced tumor cell proliferation in vitro and in vivo. These findings reveal the role of vtRNA1-1 in ensuring intracellular catabolic compartment stability and functionality, suggesting its importance in lysosome-mediated chemotherapy resistance.