CCN2 and hepatocellular carcinoma: HCC cells play a key role in inducing the differentiation of circulating monocytes in M2 pro-tumor macrophages through the secretion of specific cytokines and growth factors, such as IL-4, IL-13, CSF-1 (Colony Stimulating Factor-1), CTGF (Connective Tissue Growth Factor) [60,99] (Table 1).