Considering that Pf4 stimulates CT26 tumor growth in vivo42, has a critical role in the complement processes pathway, and exhibits altered protein expression in plasma due to exercise43, and given that CT26 represents the cancer model with the most significant splenomegaly and well-defined responses to our exercise training protocols, we investigated whether Pf4 mRNA expression might be correlated with tumor growth and whether exercise training could influence Pf4 expression in the spleen and tumor. This evidence concerns the gene PF4 and cancer.