Cancer Cells Use Bear-Like Hibernation to Survive Chemotherapy, Says Study

Cancer cells can weather chemotherapy via hibernating 'like a bear,' and resume growth afterwards.
Brad Bergan

Cancer cells can hibernate — just "like bears" in winter — when threats to their survival like chemotherapy treatment are present, according to recent research published in the journal Cell.

This is essentially the same tactic some animals use to survive long periods without resources.


Cancer cells can hibernate 'like bears' during chemotherapy

This latest study is relevant because it shows us how cancers can evade and resist drug treatments, aiding scientists in the pursuit of a way to defeat cancer once and for all. Grasping this hibernation behavior might play a major role in future research — since cancers typically return to active status after remaining dormant or appearing to disappear for multiple years after chemo treatment, Science Alert reports.

Preclinical research on colorectal cancer cells in humans shows how the cells slowed down processes into a low-maintenance, "drug-tolerant persister (DTP) state, which could help account for failures in therapy, and subsequent tumor relapse events.

Cancer cells 'co-opted' bear-like hibernation tactic

"The tumor is acting like a whole organism, able to go into a slow-dividing state, conserving energy to help it survive," said Catherine O'Brien, a researcher at the Princess Margaret Cancer Centre, Canada, in a blog post.

"There are examples of animals entering into a reversible and slow-dividing state to withstand harsh environments," added O'Brien. "It appears that cancer cells have craftily co-opted this same state for their survival benefit."

All cancer cells likely use the same hibernation tactic

Gathering the colorectal cancer cells of humans in a petri dish — and then exposing them to radiation via chemotherapy — the researchers saw the colorectal cancer cells enter the same hibernation state in a cohesive, coordinated manner.

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The cells ceased their expansion, which reduced the amount of nutrients necessary to survive.

These witnessed developments also "fit a mathematical model where all cancer cells, and not a small subpopulation, possess an equipotent capacity to become DTPs," which implies all cancer cells would show the same strategies for survival.

Cancer cells moved between mice bodies still used hibernation

Additionally, the researchers used xenografts of the colorectal cancer cells on varying sizes of mice. After the mice developed tumors of specific sizes, the researchers gave them standard regimens of chemotherapy.

There were negligible signs of tumor growth in mice receiving chemotherapy treatment throughout an eight-week time span. Tumor growth resumed as soon as treatment ceased.

Cancer cells removed from tumors after a regrowth period were subsequently grafted into other mice, and treated once more. The regrown cells were still sensitive to treatments, and their growth ceased and resumed in the same fashion — behavior consistent with cancer cells upon entering a DTP state.

Study may help target 'sleeping' cancer cells, prevent regrowth

The DTP state is much like a hibernation-state — technically called embryonic diapause — which mice embryos enter when the situation calls for a sort of "emergency survival" mode. Embryonic diapause helps numerous animals — including mice — to put the development of embryos "on hold" until the surrounding environment is more friendly to life.

And this latest study shows cancer cells have found the same thing works for them. "We never actually knew that cancer cells were like hibernating bears," said Aaron Schimmer, an oncologist at the Princess Margaret Cancer Centre, in the blog post. "This study also tells us how to target these sleeping bears so they don't hibernate and wake up to come back later, unexpectedly."

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