Considering our results in relation to the fact that most cancer cells exhibit high levels of ROS, we suggest another mechanism by which cancer cells, such as the types studied herein, taking advantage of their intrinsic ROS levels would favor cell proliferation and malignant features, altering p27Kip1 subcellular localization through an increase in the levels of p27pS10 and p27pT198. The gene discussed is CDKN1B; the disease is cancer.