Milk protein, casein, may promote the proliferation of prostate cancer cells, such as PC3 and LNCaP.

This study investigated the effect of the milk protein, casein, on the proliferation of prostate cancer cells. Different concentrations (0.1 and 1 mg/mL) of α-casein and total casein obtained from bovine milk were used to treat prostate cancer cells (LNCaP and PC3), lung cancer cells (A459), stomach cancer cells (SNU484), breast cancer cells (MCF7), immortalized human embryonic kidney cells (HEK293), and immortalized normal prostate cells (RWPE1) in a serum free media for 72 hours. Using an MTT assay, researchers examined the proliferation of each line.

Researchers discovered that α-casein and total casein increased the number of prostate cancer cells, but they had no effect on the proliferations of lung, breast, stomach, immortalized normal prostate, and immortalized human embryonic kidney cancerous  cells. This study provides strong evidence that high consumption of milk may lead to increase in cancerous cells in prostate cancer patients.