NFKB1 and central nervous system cancer: However, in cancer cells, two scenarios have been shown: A pro-oxidant activity in which melatonin induces the increase of intracellular levels of ROS, leading to cell death, as was shown in the present study and by others [26,46,47,48,49,50,51,52,53,54]; and melatonin reducing intracellular levels of ROS and inducing cell death by different mechanisms, such as, for example, inhibiting the nuclear transcription factor kappa B (NF-κB) nuclear activity, as reported in human glioma cells (T98 and U251) by Wang and colleagues [55], and in rat glioma cells (C6) by Martín and colleagues [56].