The impact of high-intensity interval exercise training on NK-cell function and circulating myokines for breast cancer prevention among women at high risk for breast cancer.

PURPOSE: Preclinical evidence suggests that natural killer cell (NK-cell) function and myokines facilitate the protective effects of exercise for breast cancer prevention. Since higher-intensity exercise acutely promotes greater mobilization and larger changes in NK-cell cytotoxicity than lower-intensity, high-intensity interval training (HIIT) might offer increased immune protection compared to moderate-intensity continuous-training (MICT). This study compared a 12-week HIIT program to a 12-week MICT program and usual care on changes in resting NK-cell function and circulating myokines among women at high risk for breast cancer. METHODS: Thirty-three women were randomized to HIIT, MICT, or usual care, for a supervised exercise intervention. Blood was collected at baseline and end-of-study. The cytotoxic activity of CD3-/CD56+ NK-cells against the K562 target cell line in vitro was determined by flow cytometry. Circulating myokines (IL-15, IL-6, irisin, OSM, osteonectin, IL-7) were assessed with luminex multiplex assays and ELISA. One-way ANOVA and paired sample t-tests assessed between- and within-group differences, respectively. Pearson correlation coefficients determined relationships between baseline fitness and change variables. RESULTS: Significant differences were not observed between groups for change in NK-cell function or circulating myokines (p > 0.05). Significant correlations were only observed for baseline peak aerobic capacity (ml/kg/min) and change in NK-cell-specific lysis (r = - 0.43, p = 0.02) and hemacytotoxicity for the total sample (r = - 0.46, p = 0.01). CONCLUSION: Our findings suggest that exercise intensity may not significantly impact change in resting NK-cell function and circulating myokines among women at high risk for breast cancer. Structured exercise training may have a larger impact on NK-cell function in those with lower levels of cardiorespiratory fitness. CLINICAL TRIAL REGISTRATION: NCT02923401; Registered on October 4, 2016.