In support of this interpretation, we reported that when NOX1 activity is decreased by exposure to diphenyleneiodonium in another NOX1-expressing human colon cancer cell line (LS-174), cell cycle blockade at the G1 interface was observed in association with a significant decrease in the expression of cyclins D1 and A, results that are very similar to our observations with HT-29 NOX1 knockdown cells (64). Here, NOX1 is linked to malignant colon neoplasm.