RhoA activity increases due to hypermethylation of ARHGAP28 in a highly liver-metastatic colon cancer cell line.

Certain cell lines exhibit metastatic ability (highly metastatic cell lines) while their parent cell lines have no metastatic ability. Differences in methylation, which are not derived from differences in the gene sequence between cell lines, were extensively analyzed. Using an established highly metastatic cell line, KM12SM, and its parent cell line, KM12C, differences in the frequency of methylation were analyzed in the promoter regions of ~480,000 gene sites using Infinium HumanMethylation450. The promoter region of the Rho GTPase-activating protein 28 (ARHGAP28) gene was the most markedly methylated region in KM12SM compared with KM12C. ARHGAP28 is a GTPase-activating protein (GAP), and it converts activated RhoA to inactivated RhoA via GTPase. RhoA activity was compared between these two cell lines. The activated RhoA level was compared using western blot analysis and G-LISA. The activated RhoA level was higher in KM12SM compared to KM12C for western blot analysis and G-LISA analysis. RhoA is a protein involved in cytoskeleton formation and cell motility. RhoA, for which ARHGAP28 acts as a GAP, is possibly a factor involved in the metastatic ability of cancer.