A paper in Nature Genetics January 2018 shows that fat promotes prostate cancer growth.

As Gina Kolata reported in the New York Times:

Geneticists knew prostate cancers often start when a protective gene, PTEN, shuts down. But the tumors in men that lose only PTEN tend to languish, rarely spreading beyond the prostate and rarely becoming lethal.

The cancers change, though, if a second gene, called PML, also shuts down. Suddenly, indolent cells become cancers that spread and kill. But why?

In the new study, researchers found that when PML was lost, cancerous cells — in petri dishes and in mice — started churning out fat, which may protect the cells from certain toxic molecules. But the fat also may help the cancers spread, the researchers suggested.

PML is also lost in human metastatic prostate cancer, but it has never been clear what the consequences might be. “This is all cool molecular genetics,” said Dr. Pier Paolo Pandolfi, director of the Cancer Center and Cancer Research Institute at Beth Israel Deaconess and lead author of the new study.

Dr. Pandolfi has long tried to study prostate cancer spread in mice, but the rodents were not much help. Few genetic manipulations made prostate cancers spread in the animals as they do in humans.

Then one day, at a meeting with colleagues, Dr. Pandolfi had an idea: “What are the mice eating?” he asked. It was mouse chow, his co-workers said — a low-fat, vegetarian concoction.

“Why don’t we try a simple experiment?” Dr. Pandolfi recalled asking. “Why don’t we put our mice on a high-fat Western diet?”

It was the missing link. Mice with prostate cancers that had lost PTEN and that were fed a high-fat diet quickly developed tumors that grew rapidly and spread. It was as though fat in the diet had an effect similar to the loss of PML, the protective gene.

Then the group asked a bigger question: Could they could protect mice from metastatic cancer by blocking fat production? That led to the experiment with a new obesity drug, fatostatin. It not only halted the cancer’s spread in the animals, but made it regress…

Dr. Pandolfi and his colleagues are planning a clinical trial with fatostatin to treat prostate cancer in humans.

Relevant background: Cancer and Nutrition by Donald Abrams