Scientific Method —

Fasting blocks a specific leukemia in mice

Fasting stops development of early stage leukemia, reverses mid-stage disease.

Roheeni Saxena - 12/22/2016, 1:40 PM

Wild rodents spread more than 35 diseases. Pet mice and rats carry much fewer, luckily, but the diseases they do spread include rat bit fever and Leptospirosis.

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A recent study published in Nature Medicine presents striking evidence that fasting alone, with no other treatments, blocks the development and progression of acute lymphoblastic leukemia in mice.

Previous research has demonstrated that caloric restriction has a variety of health benefits, but this is the first study to find such a specific effect. The study also identifies how fasting influences the activity of a specific protein on cancer cells. Unfortunately, the data may be specific to acute lymphoblastic leukemia, so cutting out food may not be a general means of attacking cancer.

Acute lymphoblastic leukemia is the most common form of cancer in children, though it does also occur in adults. Good treatments for this disease are available, but they don't work on all children, and the treatments for adults are not as effective. Over half of adults diagnosed with acute lymphoblastic leukemia succumb to the disease within five years of diagnosis, so new treatments would be welcome.

The study used mice infected with a retrovirus that triggers the development of leukemia. While humans do not get leukemia in this way, these models are widely accepted as a valid way of studying this disease.

The mice were not treated with standard chemotherapy, but were instead subjected to fasting protocols. In the first set of protocols, the mice were made to fast for anywhere from one day up to six days straight. After their fasting period, the mice were given one day of feeding before returning to a fast. In the second set of protocols, the mice were made to fast for one day, two days, three days, or four days. After these fasting periods, the mice were fed for two days before they stopped eating again. These fasting treatments were administered either immediately after the mice were infected with the leukemia-inducing retroviruses, or when the leukemia was at a mid-stage of development.

The study showed that fasting was effective in stopping the development of acute lymphoblastic leukemia in mice that received a regimen of six cycles of one-day fasting followed by one day of feeding, implemented one or two days after their infection with the leukemia-inducing retrovirus.

The researchers wanted to know if different fasting regimens or lengths might be more effective than others. After testing several approaches, they found that a minimum of four fasting cycles was needed to eliminate leukemia. Additionally, they found that with increased numbers of fasting cycles, the survival of mice continued to improve.

Next, the researchers looked at the effectiveness of fasting on mice that had mid-stage leukemia. They found that the fasting regimen significantly reduced the infiltration of leukemic cells into the spleen and lymph nodes of the afflicted mice. More than sixty percent of the fasted mice survived more than 120 days after infection with the leukemia-inducing retrovirus. By comparison, all the control mice were dead within 58 days of infection.

The researchers examined the effect that this fasting might be having on the cells' leptin receptors, since fasting is known to reduce levels of leptin in the blood, and alterations in leptin levels are seen in many types of cancer. (Leptin is a hormone linked to humans' energy balance; it regulates use of fat stores and inhibits feelings of hunger.) Fasting treatments increased leptin receptor signaling, which was linked to the leukemia-reversing effects. The full mechanism connecting this signaling pathway to its anti-cancer effects needs further investigation, but this study presents convincing evidence that leptin signaling plays an important role.

Though many more studies are needed before fasting could become a recommended treatment for acute lymphoblastic leukemia, this looks extremely promising. If it's validated, then fasting would provide a reasonable supplement that could be used in addition to the existing treatments. For now, however, it's worth being cautious, as such a simple and self-controlled solution to a complex and deadly medical problem seems incredible.

Nature Medicine, 2016. DOI: 10.1038/nm.4252 (About DOIs).