Exercise serum promotes DNA damage repair and upregulates DNA repair gene PNKP in colon cancer cells
Exercise protects against colon cancer progression, but the underlying biological mechanisms remain incompletely understood. One proposed mechanism is the release of bioactive molecules into the interstitium and systemic circulation during exercise, which may act directly on precancerous or tumour cells to suppress DNA damage, inhibit proliferation, and preserve genomic stability. Here, we evaluated the effects of exercise-conditioned human serum on DNA damage kinetics and transcriptomic signatures in colon cancer cells. Blood samples were collected from 30 participants (age 50-78 years, body mass index [≥]25 kg/m2) before and immediately after a maximal incremental cycling test. LoVo cells were exposed to pre- or post-exercise serum, treated with 2 Gy irradiation, and assessed for {gamma}-H2AX foci over 24 hours. Compared to pre-exercise serum, post-exercise serum significantly reduced {gamma}-H2AX foci at 6 hours (p=0.024) and decreased the area under the curve (AUC, p=0.014), indicating accelerated DNA repair. Post-exercise serum also increased expression of the DNA repair protein PNKP in LoVo cells, both with and without irradiation (p=0.007 and p=0.029, respectively). Transcriptomic analysis revealed upregulation of mitochondrial energy metabolism and downregulation of cell cycle and proteasome-related pathways. These findings suggest that acute exercise elicits systemic responses that enhance DNA repair and shift colon cancer cells towards a less proliferative transcriptomic state under sublethal genotoxic stress, offering a potential mechanistic explanation for the protective effects of exercise against colorectal carcinogenesis.