A new study from the University of Michigan Rogel Cancer Center has found that dietary changes may be a key to better colon cancer treatment. Cancer cells need nutrients to survive and grow. One of the most important nutrient-sensing molecules in a cell is called mTORC1. Often referred to as a master regulator of cell growth, it allows cells to sense various nutrients and thereby grow and multiply. When nutrients are limited, cells turn off the nutrient-sensing cascade and turn off mTORC1. Researchers found in cells and mice that a low-protein diet blocked the nutritional signaling pathway that triggers a master regulator of cancer growth. The results are published in Gastroenterology. The regulator, mTORC1, controls how cells use nutrient signals to grow and multiply. It is highly active in cancers with certain mutations and is known to cause cancers to become resistant to standard treatments. A low-protein diet, and specifically a reduction in two key amino acids, altered nutritional signals through a complex called GATOR. GATOR1 and GATOR2 work together to keep mTORC1 running. When a cell has enough nutrients, GATOR2 activates mTORC1. When nutrients are low, GATOR1 deactivates mTORC1. Restricting certain amino acids blocks this nutritional signaling. Previous attempts to block mTORC have focused on inhibiting its cancer-causing signals. But these inhibitors cause significant side effects — and when patients stop taking them, cancer returns. The study suggests that blocking the nutritional pathway by restricting amino acids through a low-protein diet is an alternative way to knock out mTORC. Researchers confirmed their findings in cells and mice, where they saw that restrictive amino acids stopped cancer growth and led to increased cell death. They also looked at tissue biopsies from patients with colon cancer, which confirmed that high markers of mTORC correlated with greater resistance to chemotherapy and poorer outcomes. The risk of a low-protein diet is that people with cancer often experience muscle weakness and weight loss, which could irritate a protein restriction.