Reactive oxygen species (ROS) are accidentally generated in the human body due to radiation, harmful chemicals, and imbalance in electron transport in mitochondria and so on, thus involved in aging, carcinogenesis and onset of various lifestyle-related diseases. In contrast, several organs and cells in the body possess systems for producing ROS themselves [NADPH oxidases (Noxs)], which is known to play important roles in the human body, such as bacteria-killing ability by phagocytes. Colon cells mainly possess a ROS production system called Nox1, which has been shown to be involved in cell proliferation and response to oxidative stress. Because ROS are highly toxic, the amount, timing and location of their generation are crucial. Interestingly, the colon is an organ constantly exposed to food components and their derivatives that may affect Nox1 activity. Therefore, understanding the modifications of Nox1 activity by these substances is crucial for prevention of colorectal cancer, but unfortunately, knowledge about them remains still poor. In this study, as a first step in investigating the effects of various substances on Nox1 activity in human colon, we used a human colon carcinoma cell line LS513, which constitutively expresses Nox1 and stably produces superoxide anion (O₂^-) without stimulation, and demonstrated the possibility that 1α, 25-dihydroxyvitamin D₃ up-regulates Nox1 activity by up-regulating transcription of Nox1 and NoxA1 genes in LS513 cells. LS513 cell line is expected to be a useful tool for analyzing and evaluating the effects of various substances on the O₂^--generating activity of colon cells.