CST4 and neoplasm: It is thus not surprising that the microarray analyses we performed demonstrated that NOX1 knockdown in both cells and xenografts was associated with the up-regulation of members of the cystatin family of protease inhibitors (such as CST1; Table 4) that could decrease tumor cell invasiveness (67) and down-regulation of the c-MYB proto-oncogene (Table 4), which under constitutive circumstances is responsible for blocking differentiation in colon cancer (68).