We found that the mean mRNA expression ratios of NOX1 or its accessory genes in HT-29 cells (normalized to β-actin) were ≈15,000 (×10−6) for NOX1; ≈20,000 (×10−6) for NOXO1; and 1100 (×10−6) for NOXA1 (Table 1); these experiments, in conjunction with our previous study (40), strongly suggest that among human tumor cells lines, NOX1 is most frequently expressed in those originating from the colon (31). This evidence concerns the gene ACTB and neoplasm.