PPM1D and hepatocellular carcinoma: The PPM1D mRNA expression positively associated with the infiltration rates of the CD4+ T cells (r = 0.329, P = 4.06e-10), CD8+ T cells (r = 0.237, P = 9.15e-06), B cells (r = 0.276, P = 2.00e-07), macrophages (r = 0.402, P = 1.16e-14), and DCs (r = 0.385, p = 1.88e-13) in HCC tissues.