Oxidative Stress in Human Gastric Tumors: molecular interactions between ErbB Receptors and BER pathways

Background: Deregulation and crosstalk of the intracellular signals play a key role in many human cancers. We speculate the presence of a crosstalk between ErbB and BER pathways in gastric cancer and its potential role in tumor progression. Thus, we evaluated the role of ErbB and BER systems in a gastric cancer cell line in an oxidative stress condition and their possible impact as prognostic factors, comparing their expression in tumoral and peritumoral mucosa Methods: ErbB and BER genes and proteins were evaluated by qRT-PCR and Western Blot in a human cell line model of gastric cancer (AGS) and in primary gastric carcinoma tissues. AGS cells were treated with H2O2, EGF, LY294002, PD98059 and Gefitinib alone and combined with each other. Morphology was assessed by toluidine blue staining. Effects on cell viability was tested by MTT assay Results: MTT assay showed a time-dependent reduction of viability after H2O2 co-treatments with inhibitors of ErbB signal compared to each inhibitor alone. Cell morphology showed 3 different populations strongly stressed after H2O2 treatment alone and combined. Vacuolization and a plenty microparticles release were observed. Interestingly, proteins analysis showed a strongly increased activation of EGFR and MAPKs after H2O2 treatments (alone and combined) compared to control cells, while in the same conditions, phospho-Akt was reduced. PARP-1 and OGG1 expressions were decreased after H2O2 treatment alone and combined. Gene analysis showed a time-dependent reduction of EGFR expression after H2O2 co-treatments with inhibitors of ErbB signal while ErbB2 gene expression showed an opposite behavior. BER system molecules like MUTYH, OGG1, HO-1 and APE1, showed a similar increase in the H2O2 co-treatments compared to single treatments, while NRF2 expression was reduced after H2O2/LY co-treatment. Data on gastric tissues showed the lack of EGFR activation but AKT and MAPK seemed to be more activated in tumor tissues compared to their normal counterparts, as well as OGG1. The level of ErbB2 and Mutyh gene expression is higher in intestinal than in diffuse‐type carcinomas, while ErbB4 showed an opposite behavior Conclusions: These preliminary data showed that oxidative stress modifies the EGFR and BER signaling, suggesting an integrated role between these pathways