The Effect Of Exercise-conditioned Human Serum On The Viability Of Breast Cancer Cells In Vitro

Exercise training provides significant health benefits among cancer survivors and is associated with lower breast cancer (BCa) mortality and reduced recurrence risk. Exercise-induced factors secreted into circulation, termed exerkines, have been proposed to affect tumor microenvironment and mediate some of the exercise benefits against cancer evolution. PURPOSE: This study investigated the effect of serum of BCa patients, collected after a single exercise bout as well as following exercise training, on the viability of BCa cells, in vitro. METHODS: Seven BCa patients (age: 37.9 ± 2.3 yrs, BMI: 23.7 ± 1.7 kg/m2) participated in a 3-month resistance (30 min) and aerobic (25 min; 40-60%HRreserve) exercise training program during chemotherapy. In the 2nd and 12th week (wk) of training, blood samples were collected immediately before and after an exercise session. The isolated serum was used to treat BCa cells (MCF-7) which were cultured in their regular culture media where the 10% fetal bovine serum was replaced by 10% human serum obtained in the 2nd wk before (PRE EX) and after (POST EX) an exercise session, as well as in the 12th wk (trained-PRE EX; trained-POST EX). The viability of MCF-7 cells was assessed with the ΜΤΤ and LDH assays, after 24- or 8-hours treatment with the human serum, respectively. RESULTS: The metabolic activity (MTT assay) of MCF-7 cells decreased by 44.3 ± 10.4% in the trained-POST EX condition (p < 0.05) compared to the trained-PRE EX. Similarly, cell cytotoxicity (LDH production) exhibited a 0.3-fold increase in the trained-POST EX (p < 0.01) compared to the trained-PRE EX condition. Significant differences were also revealed between POST EX and trained-POST EX conditions in MTT (102.5 ± 5.5% vs 55.7 ± 10.4%; p < 0.01) and LDH (1-fold vs 1.3-fold; p < 0.001) assay. No differences were found in cell metabolic activity and cytotoxicity between PRE EX- and POST EX-treated cells (p > 0.05). CONCLUSIONS: Our findings suggest that exercise triggers the release of biological factors in the circulation that may promote apoptosis of BCa cells, by reducing their metabolic activity and causing cell membrane damage. Interestingly, these exercise-induced anti-carcinogenic effects appear to result from regular exercise training, i.e., after the accumulation of repeated exercise bouts in the patients with BCa.