CA9 and breast carcinoma: Stable depletion of CAIX expression or inhibition of its activity with small molecule inhibitors (discussed in detail below) in the context of hypoxia results in the inhibition of tumor growth across multiple models, including breast cancer (Lou et al., 2011), colorectal cancer (Chiche et al., 2009; McIntyre et al., 2012) and glioblastoma (McIntyre et al., 2012), and demonstrates a critical role for CAIX in cancer cell survival in vivo.