We have all heard about the importance of exercise in overall health. Depending on the type, exercise helps to increase strength and flexibility and to control weight, and offers feelings of well-being. Of course it takes time and effort, but the results are very much worthwhile.
After a breast cancer diagnosis however and aggressive chemotherapy, things may change dramatically. Besides the ever-present threat of death and resultant depression, the chemotherapy (especially taxol derivatives) may bring on an extreme fatigue, that is at its worst on days 5-9 after each cycle. You may be barely able to turn around in bed, just go to the bathroom and back. Who wants to hear about exercise? And yet, once you are back on your feet, it is even more important to keep going…
It has been demonstrated since many years that physically active women are at a significantly lower risk for breast cancer. If they do get breast cancer, active women have a lower risk of relapse, and mortality. This body of published evidence was the basis for the development of breast cancer-specific guidelines and the recommendation of 150 minutes of moderate exercise a week.
Against this backdrop, several mechanisms have been proposed to explain the beneficial effects of exercise. Weight loss which reduces the levels of insulin, sex and other hormones in the blood that favor tumor formation, was the prevailing theory. However, another study that recently appeared in the Journal Cancer Research points to another dimension of the effect of exercise:
The division of cells in the body is controlled by a number of “pathways” ie cascades of enzymes where one activates another and this one another and so on. There are pathways that increase cell division and if they are hyperactive then cancer occurs; the cell divides out of control till a tumor is formed. The so-called “targeted therapy” drugs act by inhibiting such molecules (called “oncogenes”). However, there are also pathways of the “good kind” that inhibit cell division, and they are called “tumor suppressor” pathways. These make tumors regress and disappear…
One tumor suppressor pathway that has been discovered recently is called “Hippo” after a molecule that plays a key role in it. Interestingly, it was recently demonstrated that the adrenaline produced in the blood during exercise inhibits the growth of breast cancer cells in a petri dish, by inhibiting the function of Hippo pathway components. When the cancer cells were implanted under the skin of mice, the cells formed smaller tumors if they were treated with blood-serum from women that had been exercising. To top it off, when the mice with the implants themselves were allowed to exercise on a wheel placed in their cage (ie produce adrenaline), then the tumors formed by the implanted cells were half in size, than when the mice did not have a wheel to run on for fun…
That is, the adrenaline produced naturally during exercise is able to act as an anti-cancer drug, by activating a pathway (Hippo) that stops the growth of cancer cells!
We-humans do not run on exercise wheels in cages, but we can exercise in various ways to help with lymphedema too (eg swimming) or with osteoporosis (weight-bearing exercises) at the same time, skipping rope etc. Whichever type of exercise, it would suppress the growth of whatever breast cancer cells we-survivors have lurking in dark corners. I still have to hear of a drug that suppresses the growth of the cancer and with essentially no side effects apart from a
feeling of well-being! This makes the exercise classes offered by BCAK and others even more valuable. So, on we go!
Dethlefsen et al, Exercise-induced catecholamines activate the Hippo tumor suppressor pathway to reduce risks of breast cancer development. Cancer Research 77:4894-4904, September 2017.