Exogenous IL-8 regulates the expression of carcinogenesis-associated genes in HeLa cells. (A) Expression of IL-8RA, IL-8RB, ERK and NUMB was analyzed using RT-PCR. (B) Exogenous IL-8 (40 and 60 ng/ml) is able to significantly upregulate the expression of IL-RA, IL-RB and ERK genes, whereas 60 ng/ml of exogenous IL-8 downregulates the level of NUMB (*P<0.01). IL, interleukin; ERK, extracellular-signal-regulated kinase; RT-PCR, reverse transcription-polymerase chain reaction; IL-8R, IL-8 receptor; NUMB, endocytic adaptor protein.