Increased expression of connective tissue growth factor, epithelial membrane antigen, and fibroblast activation protein in hepatocellular carcinoma with aggressive behavior

Abstract

Tumor behavior is affected by not only malignant tumor cells themselves, but also by stromal cells in the tumor microenvironment, including cancer-associated fibroblasts (CAFs). Hepatocellular carcinoma (HCC) with “stemness” reportedly exhibits fibrous stroma and aggressive behavior suggestive of tumor-stroma interaction. However, the activation mechanism thereof remains unclear.

In the present study, the expressions of connective tissue growth factor (CTGF), epithelial membrane antigen (EMA), fibroblast activation protein (FAP), and keratin 19 (K19) were studied in specimens taken from 314 cases of HCC (cohort 1), 42 cases of HCC with fibrous stroma (cohort 2), and 36 cases of chronic hepatitis/cirrhosis by immunohistochemistry. Clinicopathological parameters in the HCC specimens were analyzed according to the expression status of CTGF, EMA, and FAP, respectively. The topographic expression patterns thereof were further assessed in the HCC specimens with fibrous

stroma of cohort 2.

CTGF and EMA expressions were detected in 15.3% (48/314) and 17.2% (54/314) of the HCCs of cohort 1, respectively. The expressions of CTGF and EMA were well correlated with each other (P = 0.001), and were significantly higher in HCCs with fibrous stroma, compared to those without (P = 0.028 and P = 0.003, respectively). K19 expression rate was significantly higher in HCCs with CTGF expression (17/48, P = 0.018). In HCCs with fibrous stroma, the expressions of CTGF, EMA, and FAP were noted in 40.5% (17/42), 40.5% (17/42), and 66.7% (28/42), respectively, and EMA expression was positively correlated with expressions of CTGF, K19, and FAP (P = 0.046, P = 0.026, and P = 0.020, respectively). EMA expression was found at the periphery of tumor nests in contact with fibrous stroma in 3 of 6 cases that exhibited large tumor nests, whereas it was rather diffuse in all 11 HCCs with small nests or that showed a trabecular pattern. CTGF expression rate was higher in large HCCs (≥ 5 cm), and FAP expression rate was higher in HCCs with vascular invasion (P = 0.030). Analysis of disease-free survival indicated CTGF expression as a worse prognostic factor in both cohort 1 (P = 0.005) and cohort 2 (P = 0.023), and EMA as a worse prognostic factor in HCCs with fibrous stroma (P = 0.048).

Thus, we discerned that the expressions of CTGF, EMA, and FAP are important to the activation of CAFs and gain of “stemness” in HCC, giving rise to aggressive behavior. Frequent coexpression of EMA and FAP and their

topographic expression patterns suggest possible cross-talk between epithelial cells and stromal cells in the tumor microenvironment.