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Effect of HIIT on cancer cells proliferation

by P. Debraux | 24 April 2019

science, sport, HIIT, cancer, cell, growth, proliferation, workout, training, physical activity, health, acute, chronic

Many scientific evidences today demonstrate the positive impact of physical activity on health in general and on the growth of cancers in particular. With breast and prostate cancer, colorectal cancer is one of the most common cancers in women and men. The increase in physical activity significantly reduces mortality among survivors of this cancer. It would promote a less carcinogenic metabolic environment. Scientific research shows that immediately after exercise, a reduction in the growth of cancer cells in the breast and prostate is observed. This observation is possible thanks to the collection and in vitro culture of cancer cells and their exposure to serum taken immediately after training. In the long-term, it seems that it is the accumulation of positive effects induced by each training session that would allow protection against cancer cells (and not, a chronic adaptation).

HIIT (High Intensity Interval Training) is a strong stimulus for the body and many studies show that these physiological effects are often equal or greater than those observed in continuous and moderate intensity (at equal work or not). In the end, the main advantage of this training mode lies in the intensity used. So, what about its influence on the growth of cancer colorectal cells ?

The Study

To answer this question, a team of Australian researchers studied the impact of HIIT sessions on the growth of colorectal cancer cells. For this, the researchers recruited 20 people who had survived colorectal cancer, having completed all their treatments for over a month and who were over 40 years old (the average age of participants was over 60 years). They divided the participants into 2 groups :

  • "Acute" group: The people in this group did only one HIIT session.
  • "Chronic" group: The people in this group performed 3 HIIT sessions a week for 4 weeks.

The HIIT session consisted of 4 repetitions of 4 minutes at 85-95 peak heart rate with 3 minutes of active recovery between each repetition, all on cyclo-ergometer.

For the Acute group, a blood sample was taken fasted before the HIIT session, then immediately and 120 minutes after exercise. A liquid meal (consisting of carbohydrates and protein) was given to participants just after the first blood test and 30 minutes before the start of the HIIT session.

For the Chronic group, a blood sample was taken 3 to 7 days before the start of the training program and then after the 4 weeks of training. The effects of HIIT were studied on two tumor cell lines : CaCo2 and LoVo. These cells were incubated for 24, 48 and 72 hours with the serum taken from the participants. Interleukin 6 (IL-6) and 8 (IL-8) and tumor necrosis factor alpha (TNF-α) concentrations (all three cytokines), IGF-1, insulin and glucose were measured.

Results & Analyzes

The main results of this study show that an acute HIIT session allows a significant reduction in the number of cancer cells immediately after training, whether after 24, 48 or 72 hours of incubation (Fig 1). On the other hand, no difference was observed in the number of cancer cells incubated with serum taken before or after the 4 weeks of HIIT (Fig. 2).

Cell number before and after an acute HIIT training

Figure 1. Cell number before and after an acute HIIT training. *Significantly different from before (p<0.05).

At the serology level, just after the single session of HIIT, there was a significant increase in TNF-α (+ 15.2%), IL-6 (+ 44.8%), IL-8 (+ 24.7%) and insulin (+ 38.8%). All these values returned to basal level after 120 minutes, with the exception of insulin, which was significantly lower. No significant difference was observed for the Chronic group.

Cell number before and after 4 weeks of HIIT

Figure 2. Cell number before and after 4 weeks of HIIT.

Based on the rate of apoptosis (programmed cell death) that was not different before or after exercise, the researchers concluded that the cancer cell reduction was due to a reduction in their proliferation. This reduction in proliferation is, moreover, concomitant with the increase of cytokines in the serum, and after 120 minutes, the return to normal of the cytokine blood concentrations has been accompanied by a re-proliferation of the cancer cells. These results are in agreement with the current scientific literature and tend to show that the temporary increase in cytokine concentration following a HIIT session may be an important mechanism contributing to the limitation of cancer cell growth. However, the role of cytokines is quite paradoxical, since a chronic increase in the rate of these cytokines (linked to chronic inflammation) is harmful and an increased risk factor for cancer. The exact in vivo functioning of cytokines in the proliferation of cancer cells remains to be determined.

Practical Applications

Considering the transient nature of the increase in cytokines following a HIIT session and the concomitant decrease in cancer cells, the role of physical activity seems interesting and important. Of course, a single session will not be able to change the metabolic environment sufficiently to improve overall health. But repeated exposure to this stimulus may help improve the health prognosis. This is probably why the researchers in this study found no significant differences after the 4 weeks of HIIT. Because the incubations were made with blood taken at rest before and after the 4 weeks. This implies that the cancer cells have not been routinely exposed to collected blood after each of the 12 sessions.

Regular and sufficiently intense practice (if there are no contraindications) should be encouraged in patients diagnosed with cancer. Even if the effects of sport on the body are multiple and that for the moment no mechanism of action is still sure, the regular practice of a physical activity is a primary aid in the treatment of multiple diseases and allows to effectively complete the necessary medical treatments. In addition, regular practice can lead to a beneficial change in eating behavior, which will greatly contribute to fight against the disease.

References

  1. Devin JL, Hill MM, Mourtzakis M, Quadrilatero J, Jenkins DG and Skinner TL. Acute high intensity interval exercise reduces colon cancer cell growth. J Physiol 597.8 : 2177-2184, 2019.

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