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March 31, 2008 -- Fasting prior to cancer chemotherapy treatment may significantly enhance the cancer-killing effects of the drugswhile protecting healthy cells from damage.
A new study suggests starvation induces a protective shield around healthy cells, allowing them to tolerate a much higher dose of chemotherapy.
The results showed starving laboratory mice for two days prior to chemotherapy treatment protected them from potentially toxic high doses of the drug, and they gained back the weight they lost after treatment.
Researchers say cancer chemotherapy can kill as many healthy cells as cancerous ones, but inducing temporary starvation increases the cells' resistance to stress, which may allow doctors to use higher doses of current cancer chemotherapy treatments to make them more effective.
In the study, published in the Proceedings of the National Academy of Sciences, researchers studied the effects of starvation on cancerous and normal cells.
First, they induced a starvation-related response in yeast cells, which made them 1,000 times more protected than untreated cells.
Then, they tested the effects of fasting on human and cancer cells in a test tube and in mice. The results showed starvation produced between a twofold and fivefold difference in stress resistance between the normal, starvation-treated cells and normal cells. In tests with live mice, of 28 mice starved for 48-60 hours before chemotherapy, only 1 died. Of 37 mice that were not starved prior to treatment, 20 mice died from chemotherapy toxicity.
"More importantly, we consistently showed that mice were highly protected while cancer cells remained sensitive," researcher Valter Longo, PhD, of the University of Southern California, says in news release. "If we get to just a 10- to 20-fold differential toxicity with human metastatic cancers, all of a sudden it's a completely different game against cancer."
Researchers say genetic cues prompt starved healthy cells to go into a hibernation-like mode that produces extreme resistance to stress. But cancerous cells don't obey those cues and remain stuck in growth mode.
By using the starvation response to differentiate normal and cancerous cells, researchers say healthy cells may be able to withstand higher doses of existing cancer chemotherapy drugs, but further studies in humans are needed to confirm these effects.