A fasting-like diet combined with chemotherapy may increase the immune system’s ability to recognize and kill breast cancer and melanoma cells, according to a study done on mice.
The study, “Fasting-Mimicking Diet Reduces HO-1 to Promote T Cell-Mediated Tumor Cytotoxicity,” was developed by researchers at the University of Southern California, and was published in Cancer Cell several days after a separate study showing that three-day fasting was safe and feasible in cancer patients on chemotherapy was published in BMC Cancer.
“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, professor and director of the USC Longevity Institute at the USC Leonard Davis School of Gerontology, who led the Cancer Cell study and co-led the BMC Cancer study, 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.”
Previous studies had already demonstrated that fasting for short periods starved cancer cells, enhancing chemotherapy’s effects. Now, researchers have shown that mice fed a fasting-like diet had increased levels of bone marrow progenitor cells that give rise to immune cells.
Researchers also observed that a particular type of T-cell called regulatory T-cells (Tregs), known to impair the function of tumor-killing T-cells, were expelled from the tumor upon fasting. This effect was caused by a decrease in the heme oxygenase (HO-1) enzyme inside Tregs.
“While it’s more of a mechanism to keep the T-cells away, in some ways the heme oxygenase tricks the immune system into thinking that the bad cells should not be killed,” Longo said. “By removing heme oxygenase, these T regulatory cells are also taken from the site of the cancer.”
The researchers found that putting the mice on a low-calorie fasting diet for four days, or on a two-day water-only diet, and administering the chemotherapy drugs cyclophosphamide and doxorubicin, induced a decrease in breast cancer and melanoma growth, while spurring normal healthy cells.
The mice were shown to have lower levels of HO-1, which led to a reduction in the number of infiltrating Tregs. Together with an increase in tumor-killing T-cells, those changes induced a more efficient immune response against cancer cells.