searchers examined the effects of acute exercise on tumour proliferation in established cell lines, and found that acute effects are beneficial as it enables the inhibition of cancer cell growth through modifying levels of endogenous hormones.
Prostate cancer commonly affects men worldwide, with the diagnosis occurring more frequently among developed Western countries. Generally, it is considered to be indolent or slow growing, but specific groups of individuals such as African American men have been previously found to be associated with more aggressive forms with higher risks and incidence rates of prostate cancer. Although it is perceived that prostate-specific antigen (PSA) testing may lead to misdiagnosis and improper treatment for some individuals, it would be beneficial to reconsider for those men at a higher risk.
Among various factors found to be associated with prostate cancer development, physical activity is one that is not thoroughly understood. In an earlier study, it was determined that exercise is associated with a significant decrease in risk of developing prostate cancer. In particular, long-term exercise is known to decrease levels of endogenous hormones such as leptin, insulin, and insulin-like growth factor-1 (IGF-1). Elevations of these hormones in serum are often linked to increased risk of prostate cancer. In contrast to long-term exercise, it had been reported that acute exercise had resulted in increased levels of mitogenic factors, which promote mitosis and cell division to increase cancer cell growth. These factors included growth hormone (GH), cytokines such as interleukin-6 (IL-6), and IGF-1.
To further evaluate the effect of acute exercise on cancer cell growth, a team of researchers designed an exercise intervention involving the participation of 10 healthy males in 60 minutes of bicycle exercise with increasing levels of intensity at certain time periods. Blood samples were taken via femoral catheterization before (resting serum) and after completion of the exercise (exercise serum) for subsequent analysis. An established prostate cancer cell line referred to as LNCaP was incubated with the resting or exercise serum separately in order to compare the effects of each. This cell line is useful as a prostate cancer model because it is modified to allow for direct observation of growth promotion or inhibition. A growth factor protein array approach was then carried out to identify candidate factors involved.
As reported in PLOS ONE, researchers found that exposure of the cell line to the exercise serum had resulted in a significant reduction of growth as compared to the resting serum. It was determined that this effect was attributed to the inhibition of cell growth and not to the stimulation of apoptosis or cell death. More specifically, data from the protein array had allowed researchers to pinpoint two candidate factors that are likely responsible for these results: epidermal growth factor (EGF) and insulin growth factor binding protein 1 (IGFBP-1). EGF is a growth factor that stimulates cellular proliferation and differentiation, and was found to be 18% lower after exercise. On the other hand, IGFBP-1 is a protein that binds insulin-like growth factors, and was observed to be 35% higher after exercise. The bioavailability of IGF-1 depends on levels of its corresponding binding proteins. Together, these findings imply that both EGF and IGF-1 are associated with prostate cancer risk.
Despite elevating mitogenic factors and the ensuing concern for its impact on possible development of malignancy as implied in previous research, it is evident that acute exercise can nonetheless reduce proliferation of cancerous prostate cells. It is useful to acknowledge that the transition of benign characteristics to malignant forms is influenced by the lifestyle choices we make. This study demonstrates that both short and long term factors can play important roles in reducing risk of prostate cancer. Follow-up studies and further analyses are necessary to gain more information on the importance of exercise.
Written By: Michelle Tu, BSc