CA9 and neoplasm: Besides, HIF-1α and CAIX immunostaining were performed to evaluate the changes of tumor hypoxia status after different treatments.54 As shown in Fig. 7d, the expressions of HIF-1α and CAIX proteins were down-regulated in the CC5-RuCa and CC5-RuCa plus light treated groups, possibly attributed to the function of YC-1.