Exercise serum promotes DNA damage repair and remodels gene expression in colon cancer cells.

Exercise protects against colon cancer progression, but the underlying biological mechanisms remain unclear. One proposed mechanism is the release of bioactive molecules into the systemic circulation during exercise, which may act directly on tumour cells to suppress DNA damage, inhibit proliferation, and preserve genomic stability. Here, we profiled the serum proteomic response to acute exercise and 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 overweight/obese adults 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 γ-H2AX foci over 24 h. Acute exercise increased the relative abundance of 13 proteins in serum (p < 0.05), including interleukin-6 (IL-6) and its soluble receptor IL-6R, reflecting systemic activation of acute-phase immune and vascular signalling. Compared to pre-exercise serum, post-exercise serum significantly reduced γ-H2AX foci in LoVo cells at 6 h (p = 0.010) and decreased the area under the curve (p = 0.014), indicating accelerated DNA repair. Post-exercise serum also increased expression of the DNA repair gene PNKP, 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.