New dietary regime found to slow progression of colorectal cancer

Colorectal (colon) cancer is the third most common cancer in both men and women, and typically occurs after the age of 50. The disease often starts in the colon or rectum as precancerous polyps, which are abnormal tissue growths (usually taking the form of small flat bumps). Screening technology allows early detection of polyps, so they can be monitored and treated if necessary. However, roughly 30% of adults in the United States between 50 and 75 years of age are not up to date on colonoscopy screenings.

Scientists from the University of Southern California, working in conjunction with the Firc Institute of Molecular Oncology (IFOM) in Milan, Italy, have discovered a diet that may treat certain types of cancer when combined with vitamin C. The diet focuses on the principle of fasting, or abstaining from consumption of food or drinks for a certain period of time. The idea behind a fasting-mimicking diet is that it not only starves cancerous cells of nutrients, but also activates the immune system to better detect and respond to the cancer.

Fasting is a challenging option for cancer patients, especially those who are already in a weakened state due to cancer progression or chemotherapy. A safer option is a low-calorie, plant-based diet supplemented with vitamin C; this delivers nutrients while still causing cells to react as if the body were fasting. While previous studies on the cancer-fighting efficacy of vitamin C have been mixed, more recent studies support the nutrient’s promise, especially when used in combination with chemotherapy. In the USC study, the researchers hypothesized that the diet would enhance the hyperdosed vitamin C’s effect by creating an environment within the body that would be unsustainable for cancerous cells, while still being safe for normal cells.

“For the first time, we have demonstrated how a completely non-toxic intervention can effectively treat an aggressive cancer… Our first in vitro experiment showed remarkable effects. When used alone, fasting-mimicking diet or vitamin C alone reduced cancer cell growth and caused a minor increase in cancer cell death. But when used together, they had a dramatic effect, killing almost all cancerous cells.

Valter Longo, Senior Study Author and Director of the Longevity Institute at the USC Leonard Davis School of Gerontology

One of the most promising aspects of this treatment is its effect on KRAS-mutated cells. The KRAS gene provides instructions to make the K-Ras protein, which is part of the pathway signalling cells to grow, mature, and divide. It is classified as an oncogene, which is a gene that, when mutated, has the potential to cause normal cells to become cancerous. KRAS mutations signal that the body is resisting cancer-fighting treatment, and they reduce survival rate. These mutations occur in about a quarter of all human cancers, but up to half of colorectal cancers. The strong effect of the study’s treatment was shown to occur in cells with this gene mutation, which has been regarded as one of the most challenging targets to tackle in cancer research.

Studying the KRAS gene also may provide clues as to why some past studies showed a limited effect of vitamin C on cancerous cells. When administered alone, vitamin C appears to trigger KRAS-mutated cells to protect cancer cells by releasing an iron-binding protein known as ferritin. However, by reducing bodily levels of ferritin, vitamin C’s toxicity to cancer cells was increased. It was also noted that colorectal cancer patients with high bodily levels of ferritin have a lower chance of survival.

The study’s researchers spoke of their hope that treatments such as theirs will someday replace more toxic methods. With their method looking promising to move toward human trials, they are investigating the effects of the fasting-mimicking diet in combination with other cancer-fighting drugs. They also plan to test similar diets on breast and prostate cancer patients.

Original story and interview by Jenesse Miller.

References

1. Di Tano M, Raucci F, Vernieri C, Caffa I, Buono R, Fanti M, Brandhorst S, Curigliano G, Nencioni A, de Braud F, Longo VD. 2020. Synergistic effect of fasting-mimicking diet and vitamin C against KRAS mutated cancers. Nature Communications 11.
2. Miller J. 2020. A combo of fasting plus vitamin C is effective for hard-to-treat cancers, USC study shows. USC Press Room. University of Southern California.
3. CDC. 2020. Colorectal (Colon) Cancer. Centers for Disease Control and Prevention. U.S. Department of Health & Human Services.
4. NIH. National Cancer Institute SEER Training Modules. Types of Colorectal Cancer. National Institutes of Health.
5. NIH. 2017. KRAS Gene. Genetics Home Reference. National Institutes of Health.