Kim et al. demonstrated also anticancer effects of arsenic hexoxide (As4O6; AS6) used at a small, nontoxic dose of 5 μM. Authors showed a significant attenuation of cell growth by AS6 in MCF-7 cells and assumed that in advanced breast cancer tumor necrosis factor α (TNF-α) is included in cancer progression and metastases [26]. This evidence concerns the gene TNF and breast cancer.