To determine whether this known ccRCC cell surface marker could be used to select ccRCC cells present in mixtures of cancer and normal cells, we purified CA9+ and CA9− cells from cryopreserved primary single cell suspensions or early passage 10 % FBS cultures using fluorescence-activated cell sorting, and (re)cultured them in 10 % FBS (Fig. 1c, d). This evidence concerns the gene CA9 and cancer.