Colorectal cancer(CRC)is the third most frequently diagnosed cancer worldwide,responsible for over 880 000 deaths each year.Growth/differentiation factor 15(GDF-15)is reported to be a promising diagnostic and prognostic factor in CRC.It induces pleiotropic effects in tumor cells:proliferation,stemness,invasion and metastasis.Some studies indicate that GDF-15 may stimulate angiogenesis in malignant neoplasms.However,it has not been investigated in CRC yet.The aim of our study was to determine the level of GDF-15 and the concentrations of hypoxia-inducible factor-1α(HIF-1α),VEGF-A and chemokine-like receptor 1(CMKLR1)in tumor and margin specimens of CRC in relation to histological grade and TNM staging.The study comprised 33 samples of tumor and margin tissues obtained from CRC patients.To assess the concentration of GDF-15,HIF-1α,VEGF-A and CMKLR1,commercially available enzyme-linked immunosorbent assay(ELISA)kits were used.We found significantly increased levels of GDF-15 and CMKLR1 in tumor tissue compared to margin tissue and higher concentrations of HIF-1α and VEGF-A in margin tissue than in tumor tissue.The levels of GDF-15 and HIF-1α were significantly correlated with VEGF-A and CMKLR1 in margin tissue.In CRC,the increased level of GDF-15 might stimulate angiogenesis through upregulation of HIF-1α,VEGF A and CMKLR1 expression.Our study is the first one to reveal the correlation between the levels of GDF-15 and CMKLR1 in CRC.The elevated levels of HIF-1α and VEGF-A in tumor-free margin tissues suggest that noncancer cells in the tumor microenvironment are an important source of proangiogenic factors.