COL4A2 and hepatocellular carcinoma: In addition, increasing mRNA levels of genes encoding for collagenase proteins (i.e., COL4A2 and COL4A3) were noticed; these ones are two of the major structural components of the tumor microenvironment in hepatocellular carcinoma (HCC) together with CCND1, a gene overexpressed in multiple malignant tumors, including HCC itself (Liu et al. 2020; Ding et al. 2020).