Cancer cells ‘hibernate like bears’ to dodge chemotherapy: Study

A new study has found that the cancer cells present in the body have the ability to hibernate like “bears in winter” in order to evade chemotherapy treatment.

This finding also buttresses the fact that the disease often returns after staying dormant or disappears for several years after the treatment.

Preclinical research on human colorectal cancer cells revealed that they were able to slow down into a low-maintenance, “drug-tolerant persister” (DTP) state, which would help explain some failures in therapy and tumour relapses.

Researcher and surgeon Catherine O'Brien, from the Princess Margaret Cancer Centre in Canada, said: “The tumour is acting like a whole organism, able to go into a slow-dividing state, conserving energy to help it survive.”

He added: “There are examples of animals entering into a reversible and slow-dividing state to withstand harsh environments. It appears that cancer cells have craftily co-opted this same state for their survival benefit.”

Through their study, the researchers observed that the colorectal cancer cells go into the same hibernation state, in a coordinated way, when chemotherapy drugs were present. The cells stopped expanding, which means they required very little in the way of nutrients to carry on living.

These observations suggest that all cancer cells possess an equipotent capacity to become DTPs, which suggests these survival strategies could be seen in all cancer cells.

For the study, researchers carried out their experiment on mice. They infused colorectal cancer cells on different sets of mice. The researchers then treated the mice with standard chemotherapy regimens.

They observed negligible tumour growth in mice receiving treatments during an eight-week period. When treatment stopped, tumour growth began again.

The regrown cells remained sensitive to treatments, and their growth stopped and started in the same fashion, findings consistent with cancer cells entering a DTP state.

This DTP state closely resembles a hibernation-like state called embryonic diapause that mice embryos fall back on as a sort of emergency survival mode until environmental conditions are more favourable. The cancer cells apply the same trick to dodge the treatments.

Oncologist Aaron Schimmer, from the Princess Margaret Cancer Centre, said: “We never actually knew that cancer cells were like hibernating bears. This study also tells us how to target these sleeping bears so they don’t hibernate and wake up to come back later, unexpectedly.”

“I think this will turn out to be an important cause of drug resistance and will explain something we did not have a good understanding of previously,” he added.

The findings of the research have been published in the journal Cell.