Melanoma is a type of skin cancer that develops from cells called melanocytes, is one of the fastest-growing and deadliest cancer in the world. It usually caused by DNA damage resulting from exposure to ultraviolet (UV) light from the sun.
P. acnes is a ubiquitous gram-positive anaerobic bacterium present in the healthy skin flora among the multiple commensal microorganisms. P. acnes is critical in the regulation of skin homeostasis and prevents colonisation from other harmful pathogens but it can also act as an opportunistic pathogen in acne vulgaris.
Di Nardo et al show P. acnes inhibits DNA damage melanocytes survival and proliferation after UVB radiation in vitro by increasing apoptosis, producing coproporphyrin and upregulating TNF-α. This study also suggest that the balance achieved by different skin commensal may protect normal human melanocytes from the risk of becoming tumor cells and highlight on prevention and treatment of melanoma and other UV related cancer.
Source : Skin commensal bacteria S. epidermidis promote survival of melanocytes bearing UVB‐induced DNA damage, while bacteria P. acnes inhibit survival of melanocytes by increasing apoptosis https://onlinelibrary.wiley.com/doi/abs/10.1111/phpp.12411