China did a huge study on cancer. T. Colin Campbell wrote about this in his book The China Study. It looks like the more animal protein you eat, the more likely you are to get cancer.

Taking a cursory glance at the cancer rates in different countries, it does seem to correlate with the amount of animal protein eaten:

http://www.wcrf.org/int/cancer-facts-figures/data-cancer-fre...

https://data.oecd.org/healthstat/deaths-from-cancer.htm

https://en.wikipedia.org/wiki/List_of_countries_by_meat_cons...

https://en.wikipedia.org/wiki/List_of_countries_by_milk_cons...

The only country that looks kinda odd is South Korea...

There also have been several studies on protein and IGF-1 (a growth hormone). The more protein you eat, the higher levels of IGF-1 you get:

http://cebp.aacrjournals.org/content/11/11/1441.long

https://www.ncbi.nlm.nih.gov/pubmed/10883675?dopt=Abstract

https://www.ncbi.nlm.nih.gov/pubmed/1596498

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2673798/

Just mentioning a few here, but there are even more studies on this.

Also, there are the people with the Laron syndrome. They have some error in their IGF-1 receptors, and have very low rates of cancer.

https://en.wikipedia.org/wiki/Laron_syndrome