Did you know your body contains 10 times as many bacterial cells as it does human cells? In fact, there is around one million bacteria living on each square centimetre of your skin! Some bacteria that normally live on human skin has been discovered to produce a substance that can prevent growth of abnormal or cancerous cells. The substance was discovered to prevent growth of some forms of melanoma without damaging systemic effects in early trials. It also found that mice which had this bacteria present normally on their skin had a reduced chance of developing ultra-violet light induced cancers (i.e. skin cancers).
Link article to read more. https://advances.sciencemag.org/content/4/2/eaao4502