Elevated expression of RAB3B plays important roles in chemoresistance and metastatic potential of hepatoma cells

<jats:title>Abstract</jats:title><jats:sec> <jats:title>Background</jats:title> <jats:p>Cancer stem cells (CSCs) are thought to play important roles in carcinogenesis, recurrence, metastasis, and therapy-resistance. We have successfully induced cancer stem-like sphere cells (CSLCs) which possess enhanced chemoresistance and metastatic potential. To enable the development of targeted therapy against CSLCs, we identified a gene responsible for this phenotype in CSLC.</jats:p> </jats:sec><jats:sec> <jats:title>Methods</jats:title> <jats:p>Human hepatoma cell line SK-HEP-1 was used for CSLC induction with a unique sphere inducing medium, and HuH-7 cells were used as non-sphere forming cells in the same condition. RNA-sequencing was performed followed by validation with quantitative RT-PCR and western blotting. Knockdown experiments were done by using CRISPR-Cas9 genome-editing, and the rescue experiments were performed using the expressing plasmid vector. Chemoresistance and liver metastasis of the cells, was studied following the splenic injection of cells to severely immune deficient mice and evaluated using the MTS assay. Quantification of exosomes in the medium was done using ELISA.</jats:p> </jats:sec><jats:sec> <jats:title>Results</jats:title> <jats:p><jats:italic>RAB3B</jats:italic> was identified as an up-regulated gene in both CSLCs and prognostically poor hepatocellular carcinoma (HCC) by RNA-sequencing. <jats:italic>RAB3B</jats:italic>-KD cells showed altered CSLC phenotypes such as sphere formation, chemoresistance, and metastatic potentials, and those were rescued by <jats:italic>RAB3B</jats:italic> complementation. Increased exosome secretion was observed in CSLCs, and it was not observed in the <jats:italic>RAB3B</jats:italic>-KD cells. In addition, the <jats:italic>RAB3B</jats:italic> expression correlated with the expression of <jats:italic>ABCG2</jats:italic>, <jats:italic>APOE</jats:italic>, <jats:italic>LEPR</jats:italic>, <jats:italic>LXN</jats:italic>, and <jats:italic>TSPAN13</jats:italic>.</jats:p> </jats:sec><jats:sec> <jats:title>Conclusion</jats:title> <jats:p>The up regulation of <jats:italic>RAB3B</jats:italic> may play an important role in the chemoresistance and metastatic potential of CSLCs.</jats:p> </jats:sec>