NOX1 and colonic neoplasm: Because presence of NOX1 mRNA and protein are not sufficient for NOX1 catalytic activity, we next examined the expression of the 2 known isoforms of NOX1—full-length functional NOX1-L and the inactive shorter splice-variant NOX1-S (also termed NOX1-Lv) that lacks exon 11 within the NADPH binding domain [28, 38]—in a subset of 9 cell lines: 8 colon cancer cell lines and the HEK293-NOX1 clone using two distinct PCR primers.