Anti-cancer activity of anti-p185HER-2 ricin A chain immunotoxin on gastric cancer cells

Background and Aim: Overexpression of the human epidermal growth factor receptor 2 (HER-2) protein has been detected in gastric cancer and has been associated with an unfavorable prognosis. We investigated the anti-cancer effects of anti-p185HER-2 ricin A chain (RTA) immunotoxin, alone or in combination with 5-flurouracil on SGC7901-HER-2+ cells. Methods: SGC7901-HER-2+ cells were obtained by transfecting SGC7901 cells with HER-2-pcDNA3.1. Anti-p185HER-2-RTA was prepared by chemical conjugation of anti-HER-2 monoclonal antibody (mAb) and RTA. The SGC7901-HER-2+ cells were incubated with RTA, anti-p185HER-2-RTA, and/or 5-flurouracil. The effects of drugs on cells were evaluated by MTT assay and Annexin V-fluorescein isothiocyanate and propidium iodide double staining flow cytometry. The expression of caspase-3, caspase-9, cyclooxygenase-2, and nuclear factor-kappa B/p65 were assayed by western blot. SGC7901-HER-2+ cells were transplanted into BALB/c nude mice to produce solid tumors in an attempt to study the immunotoxin activity in vivo. Results: In vitro, anti-p185HER-2-RTA inhibited cell growth and induced apoptosis in SGC7901-HER-2+ cells. Anti-p185HER-2-RTA enhanced caspase-3 and caspase-9 activity, while downregulating the expression of cyclooxygenase-2 and nuclear factor-kappa B/p65. Its combination with 5-flurouracil further inhibited the growth of SGC7901-HER-2+ cells. In vivo, our data showed that anti-p185HER-2-RTA significantly inhibited the growth of SGC7901-HER-2+ cells-transplanted tumors. Conclusions: Anti-p185HER-2-RTA inhibits the growth of SGC7901-HER-2+ cells. The effect may be related to the activation of caspase-3 and caspase-9 and inhibition of cyclooxygenase-2 and nuclear factor-kappa B/p65. Anti-p185HER-2-RTA plus 5-FU enhance anti-cancer activity, suggesting useful clues for further study for the treatment of HER-2 positive gastric cancers.