Hunger Gains: A new study in mice suggests that fasting might not only protect human cells against damage from chemotherapy--but that it could also make the treatment more deadly for cancer cells. Image: iStockphoto/Silvrshootr
Cancer treatment can be brutal for patients. Many of the tools we have—chemotherapy, radiation—are big, blunt weapons that deal punishing blows to healthy tissues along with cancerous ones. So the hunt has been on for more and more finely targeted therapies that will attack malignant cells yet minimize damage to patients' bodies.
But a new study shows that we might be able to catch cancer cells off guard by using an ancient and body-wide tactic: fasting.
Fasting has long been practiced as part of various cultural traditions and has, more recently, gained favor in alternative and complementary medicine practices. But researchers are still figuring out whether nutritional deprivation can prevent or cure some diseases—and if so, how.
The new study found that in mice with cancer, fasting prior to chemotherapy often led to more tumor shrinkage than chemo alone. And in some cases, the combination apparently eliminated certain kinds of cancer. This fasting–chemo combo, the researchers suggest, "could extend the survival of advanced stage cancer patients by both retarding tumor progression and reducing side effects," they noted in their study, published online Wednesday in Science Translational Medicine. It might be able to help early-stage patients, too, they say.
The new work builds on a 2008 mouse study that found fasting helped to protect healthy cells against chemotherapy's toxic effects. That finding raised flags in the cancer field. "The concern was we were also protecting the cancer cells," says Valter Longo, a professor of biology and gerontology at the University of Southern California Davis School of Gerontology and co-author of the new paper. So he and his colleagues embarked on five years of research to see whether that was the case, testing different fasting and chemotherapy regimens on a variety of cancers—glioma, melanoma, neuroblastoma, breast and ovarian—in mice. "We not only saw that the cancer was not protected but that it was sensitized" to the chemo, he says.
In the new work, fasting mice were allowed to drink water but were not given food for at least two days. When mice with breast cancer, glioma or melanoma were subjected to two rounds of 48-hour fasting before their chemo, their tumors shrunk more than those in mice that received chemotherapy alone.
Mice that had metastasized cancer and were put on the fasting-chemo plan showed a 40 percent greater reduction in their metastases than those that had been fed before receiving chemotherapy. They also seemed to live longer after getting this treatment. With two cycles of fasting and a high dose of chemo, 42 percent of mice with one of two types of metastatic neuroblastoma lived for more than 180 days, whereas all of their well-fed, chemo-treated mice had already died by then. Fasting and chemo together had an even more dramatic effect in a third type of metastatic neuroblastoma: about a quarter of mice lived for more than 300 days, at which point they still seemed to be cancer free.
Fasting appears to protect normal cells from chemotherapy's toxic effects by rerouting energy from growing and reproducing to internal maintenance. But cancer cells do not undergo this switch to self-repair and so continue to be susceptible to drug-induced damage—making for what the researchers call a differential stress resistance. Fasting, then, the authors wrote, should enhance the power of chemotherapies without having to resort to "the more typical strategy of increasing the toxicity of drugs."