A very low-calorie, fasting-like diet starves breast cancer cells, rendering them more sensitive to chemotherapy and strengthening the immune system’s ability to fight the tumor, according to results of a study, “Fasting-Mimicking Diet Reduces HO-1 to Promote T Cell-Mediated Tumor Cytotoxicity,” published this month in the journal Cancer Cell.
Current treatments for cancer, including radiotherapy and chemotherapy, normally hamper immune cells’ efforts to kill a cancer. Short-term starvation has been shown to sensitize cancer cells to chemotherapeutics, while protecting normal cells from these drugs’ side effects.
Researchers in this study developed a fasting-mimicking diet — low in calories, protein, and sugar — and fed it to mice models of breast cancer. On average, animals fed a normal diet consumed 14.9 kcal per day. Animals under a fasting diet had that caloric total reduced by 50 percent on the first day, and were given only 9.7 percent on the following three days. These mice ate all the supplied food each day, and showed no signs of food aversion. After four days, the mice were fed normally for 10 days before starting another fasting-diet cycle.
Interestingly, this diet plan was seen to reduce breast cancer cell growth in the absence of chemotherapy. Moreover, it sensitized cancer cells to the chemotherapy drugs doxorubicin (DXR) and cyclophosphamide (CP). Similar effects of the fasting-like diet were observed in a melanoma model, where a strict diet combined with those two chemo drugs resulted in a three-fold reduction in tumor volume compared with mice on a normal diet.
“The mouse study on skin and breast cancers is the first study to show that a diet that mimics fasting may activate the immune system and expose the cancer cells to the immune system,” Valter Longo, who led the University of Southern California team, said in a press release. “This could be a very inexpensive way to make a wide range of cancer cells more vulnerable to an attack by the immune cells while also making the cancer more sensitive to the chemotherapy.”
Investigating the immune system’s response, the researchers found that cancer-killing cells were also more effective at attacking and shrinking the tumors. Repeating three cycles of the fasting diet, combined with doxorubicin, led to a 33 percent increase in the levels of cancer-fighting white blood cells.
While this study was done in mice, a pilot trial in 18 cancer patients of a three-day, fasting-like diet was found “safe and feasible” for the patients, undergoing chemotherapy at the time. The researchers recommend that a doctor-monitored, fasting-like diet could be an option to increase the effectiveness of immunotherapy in a range of cancers.
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