ErbB and BER pathways in human gastric carcinoma cell line AGS: implication for a molecular cross-talk

OBJECTIVE: In many human cancers deregulation of the intracellular signals are the driving forces of the disease. We hypothesize the presence of a cross-talk between ErbB and BER pathways in pathological gastric tissue and its potential role as a molecular signature for progression of the disease, altering the tumor microenvironment. For this purpose, we evaluated the role of EGF/ErbB and BER systems in AGS human gastric cancer cell line. MATERIALS AND METHODS: ErbB receptors, BER and Nrf2/ARE gene and protein expressions were evaluated by qRT-PCR and Western Blot. Effects of treatment on cell cycle was analyzed by flow cytometry, while the viability was tested by MTT assay. In particular, the AGS cells, cultured in serum-free basal medium, were treated with H2O2, EGF, LY294002 and PD98059 alone and combined with each other. RESULTS: In AGS cells H2O2 induced changes in cell morphology associated with an elongation phenotype and formation of microparticles. The combined treatments with H2O2 significantly reduced cell viability, and in particular the co-treatment with LY294002. In the presence of H2O2 a reduction of the population in S-phase after 48 hours compared to 24 hours of treatment was observed. An up-regulation of ErbB2 gene expression was observed after EGF treatment, while ErbB3 and ErbB4 increased in the single treatment with LY294002 and H2O2. The expression level of the BER system molecules, specifically MUTYH, OGG1 and APE1, increased in the combined treatment of H2O2 with EGF and LY294002 (H2O2+EGF; H2O2+LY294002) compared to single treatment (EGF; LY294002); while NRF2 gene expression was reduced after H2O2 plus LY294002 treatment. Although no significant change of EGFR expression was shown, an increase of phospho-EGFR after treatments with H2O2 alone or combined with EGF, LY294002 or PD98059 was demonstrated. Interestingly, an increased activation of MAPK was detected with H2O2 (alone and in co-treatment with EGF and LY294002), while in the same conditions, phospho-Akt was downregulated. CONCLUSION: These preliminary data suggest that a pronounced stress with H2O2 may induce a mutual regulation of BER system and ErbB receptors. Further studies are necessary to know whether the expression of BER system molecules is MAPKdependent.