SMAD4 and cholangiocarcinoma: As depicted in Figure 2, STING1 expression positively correlated with SMAD4 expression in intrahepatic CCA (iCCA; r2 = 0.377, p < 0.001), perihilar CCA (pCCA; r2 = 0.355, p < 0.001) and distal CCA (dCCA; r2 = 0.236, p < 0.001).