I found an article that discusses the possible benefit that metformin may have on prostate cancer. It seems that it doesn't prevent prostate cancer, but may curtail the growth of cancer cells. I am going to go ahead and cut paste the pertinent part of the article that discusses WHY it may slow the development of prostate cancer, and provide the link to the article that I read this morning. I am always interested in the 'how' and 'why' stuff
Link: https://www.harvardprostateknowledge.org/diabetes-drug-showing-promise-for-prostate-cancer-treatment
The cut and paste portion:
Why would metformin have anti–prostate cancer effects?
Still, hopes that metformin will be useful in prostate cancer treatment are very much alive and kicking. And even if you were to ignore the epidemiological evidence, there are reasons to believe that metformin might have some treatment benefit.
The effect may be indirect. Metformin lowers the amount of insulin circulating in the blood by lowering blood sugar levels and by making tissue more sensitive to insulin, which is a hormone that pulls blood sugar out of the blood and into cells. Insulin and related factors tend to rev up some cancers, including prostate cancer, making them more likely to proliferate and spread. So by lowering circulating insulin levels, metformin may be taking away some of the stimulus for prostate cancer cell growth.
Metformin may also have more direct effects. Metformin lowers the blood sugar output of liver cells by hampering energy-generating processes within their mitochondria. It may do the same to cancer cells and their mitochondria—and cancer cells, which are growing and dividing with the brakes off, need those energy-generating processes going full tilt.
Other research suggests that metformin’s direct effects may be the result of its interactions with complicated chains of chemical reactions called signaling pathways that can nudge dangerous cancer cells into programmed cell death (apoptosis).