Analysis of the gene expression related to hypoxia (HIF1A, ANGPTL4 –Angiopoietin-like 4, TGFB1 –Transforming Growth Factor Beta 1, VEGFA, ERBB3 –Erb-B2 Receptor Tyrosine Kinase 3, CA9 –Carbonic anhydrase 9) or specific for inflammation in hypoxic sites (CCL2 –C-C motif chemokine 2 precursor, CCL5 –C-C motif chemokine ligand 5) at day 4, 7, 10, 14, 16, and 19 after CT26 cancer cells inoculation showed that the tumor hypoxia at molecular level was relatively high at the early stage of the tumor development (Fig 1). This evidence concerns the gene HIF1A and cancer.