ROS-lowering doses of vitamins C and A accelerate malignant melanoma metastasis

Oxidative stress is a barrier of migration and metastasis for malignant melanoma cells. Consequently, reducing oxidative stress with the antioxidant N-acetylcysteine (NAC) stimulates melanoma cell migration in vitro and metastasis in vivo. However, it is not yet known whether the NAC effect is shared with other antioxidants. Here, we screened 104 redox-active compounds and identify 27 that increase migration of human malignant melanoma cells in two doses. Validation experiments in four cell lines and four drug doses resulted in a list of 18 compounds which were ranked based on their ability to increase migration and reduce ROS levels; vitamin C (VitC) ranked as number one, followed by the vitamin E analogue Trolox and several carotenoids and Vitamin A-related compounds. Four diet-relevant compounds from this list-VitC, β-carotene, retinyl palmitate, and canthaxanthin-were selected and found to accelerate metastasis in mice with BRAF^V600E-driven malignant melanoma. Genomics analyses revealed that the transcription factor BACH1 is activated following antioxidant administration and knockout of Bach1 in mouse melanoma cells reduced lymph node and liver metastasis in xenograft mouse models. We conclude that a broad range of antioxidants accelerate melanoma migration and metastasis and that BACH1 is functionally linked to melanoma metastasis in vivo.