CA9 and familial pancreatic carcinoma: An analysis of the correlation between expression and hypoxic environment revealed that MUC1 and MUC4 expression was correlated with a hypoxic environment, as was expression of CAIX. This is similar to the results of our previous study in which we showed that a hypoxic environment upregulates MUC1 expression in a pancreatic cancer cell line, and hypoxia-inducible MUC1 contributes to hypoxia-driven angiogenesis through the activation of proangiogenic factors in pancreatic cancer [31].