MAPK1 and hepatocellular carcinoma: The results displayed a linear regression between Syncytin-1 and p-MEK1/2 (r = 0.720, p < 0.001) or p-ERK1/2 in HCC patients (r = 0.627, p < 0.001, Fig. 4d), suggesting that the expression of Syncytin-1 was positively related to the level of p-MEK/p-ERK.