The human vault RNA enhances tumorigenesis and chemoresistance through the lysosome in hepatocellular carcinoma.

The small non-coding VTRNA1-1 (vault RNA 1-1) is known to confer resistance to apoptosis in several malignant cell lines and to also modulate the macroautophagic/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. Knockout (KO) of VTRNA1-1 in human hepatocellular carcinoma cells reduced nuclear localization of TFEB (transcription factor EB), leading to a downregulation of the coordinated lysosomal expression and regulation (CLEAR) network genes and lysosomal compartment dysfunction. We demonstrate further that impaired lysosome function due to loss of VTRNA1-1 potentiates the anticancer effect of conventional chemotherapeutic drugs. Finally, loss of VTRNA1-1 reduced drug lysosomotropism allowing higher intracellular compound availability and thereby significantly reducing tumor cell proliferation in vitro and in vivo. These findings reveal a so far unknown role of VTRNA1-1 in the intracellular catabolic compartment and describe its contribution to lysosome-mediated chemotherapy resistance.