Calu-6 tumors showed extensive plasma membrane staining for CA9 in contiguous tumor cells bordering regions of necrosis (Fig. 2A), with 12.1% ± 0.9% of cells in Calu-6 tumors positively stained with CA9 (Fig. 2E), demonstrating that Calu-6 tumors contain significant areas of hypoxia. This evidence concerns the gene CA9 and neoplasm.