CXCR2 and neoplasm: If we analyzed associations between serum concentrations of the analyzed proteins and the depth of tumor invasion (T-factor) in PC, we found that serum levels of CXCR4, CXCR2 and CEA were higher in the T4 subgroup in comparison to T1 + T2 + T3 subgroup, however these differences were not statistically significant (Table 4).