Chemoresistance is a major hallmark driving the progression and poor prognosis of
hepatocellular carcinoma (HCC). Limited chemoresponse of HCC was demonstrated to be mediated by
mitogen-activated protein kinase 14 (
MAPK14) and
activating transcription factor 2 (ATF2). Recently, we have demonstrated loss of control of RAS-RAF-ERK-signaling as a consequence of miR-622 downregulation in HCC. However, the majority of target genes of this potent tumorsuppressive
microRNA had remained elusive. The MAPK14-ATF2-axis represents a collateral pathway ensuring persisting ERK-activation in the presence of
sorafenib-mediated RAF-inhibition. In contrast to the function of the MAPK14-ATF2-axis, both the expression and regulation of
MAPK14 and ATF2 in human HCC remained to be clarified. We found combined overexpression of
MAPK14 and ATF2 in human HCC cells, tissues and in
sorafenib resistant cell lines. High expression of
MAPK14 and ATF2 was associated with reduced overall survival in HCC patients. Deciphering the molecular mechanism promoting combined upregulation of
MAPK14 and ATF2 in HCC, we revealed that miR-622 directly targets both genes, resulting in combined de-repression of the MAPK14-ATF2-axis. Together, miR-622 represents a superior regulator of both RAS-RAF-ERK as well as MAPK14-ATF2-signaling pathways in
liver cancer.