Switching from animal proteins to plant proteins was also found to inhibit tumor growth. Lentils and beans are one of the best sources of plant protein.

Dietary Protein Restriction Inhibits Tumor Growth In Human Xenograft Models Of Prostate And Breast Cancer, Oncotarget, December 2013

This is from their introduction, which typically includes a literature review:

Prostate (PCa) and breast (BC) cancers are the most commonly diagnosed cancer in men and women living in Western countries [1]. Studies of populations migrating from low- to high-risk areas have shown a steep rise in PCa and BC rate [2,3]. In addition, in the last three decades the age-standardized PCa and BC incidence and mortality rate has increased dramatically in Japan and Singapore, two developed countries previously considered having a very low prevalence rate [4,5]. These studies strongly suggest that environmental factors play a key role in PCa and BC pathogenesis. It has been hypothesized that this increased prevalence of PCa and BC is partially due to the radical dietary shifts from traditional to Western diet patterns [2,6], which are characterized by high intakes of animal protein and fats, and refined carbohydrates.

Data from epidemiological and experimental studies indicate that protein intake is one of the most important dietary regulators of circulating levels of IGF-1, a powerful growth factor, which activates the Akt/mTOR pathway [7,8]. High circulating levels of IGF-1 are associated with increased risk of PCa and BC [9-11], Moreover, multiple lines of evidence have shown that activation of the PI3K/AKT/mTOR pathway, through insulin/IGF-1 stimulation and/or high levels of essential amino acids, play a crucial role in maintaining the malignant phenotype, and its inhibition antagonizes growth and motility of a range of cancer cells in mouse models [12-17].

They found:

• 70% inhibition of tumor growth in the prostate cancer model.
• 56% inhibition in the breast cancer model.

When fed:

• 7% protein diet when compared to an isocaloric 21% protein diet.

Animal protein was more cancer-promoting than plant protein:

• We observed that modifications of dietary protein quality, independently of protein quantity, decreased tumor growth. A diet containing 20% plant protein inhibited tumor weight by 37% as compared to a 20% animal dairy protein diet.

They concluded:

Our findings suggest that a reduction in dietary protein intake is highly effective in inhibiting tumor growth in human xenograft prostate and breast cancer models, possibly through the inhibition of the IGF/AKT/mTOR pathway and epigenetic modifications.

It’s not genes. It’s diet.