Combination therapy of anti-cancer bioactive peptide with Cisplatin decreases chemotherapy dosing and toxicity to improve the quality of life in xenograft nude mice bearing human gastric cancer

BACKGROUND: A great challenge of cancer chemotherapy is to eliminate cancer cells and concurrently maintain the quality of life (QOL) for cancer patients. Previously, we identified a novel anti-cancer bioactive peptide (ACBP), a peptide induced in goat spleen or liver following immunization with human gastric cancer protein extract. ACBP alone exhibited anti-tumor activity without measurable side effects. Thus, we hypothesize that ACBP and combined chemotherapy could improve the efficacy of treatment and lead to a better QOL. RESULTS: In this study, ACBP was isolated and purified from immunized goat liver, and designated as ACBP-L. The anti-tumor activity was investigated in a previously untested human gastric cancer MGC-803 cell line and tumor model. ACBP-L inhibited cell proliferation in vitro in a dose and time dependent manner, titrated by MTT assay. The effect of ACBP-L on cell morphology was observed through light and scanning electron microscopy. In vivo ACBP-L alone significantly inhibited MGC-803 tumor growth in a xenograft nude mouse model without measurable side effects. Treatment with the full dosage of Cisplatin alone (5 mg/kg every 5 days) strongly suppressed tumor growth. However, the QOL in these mice had been significantly affected when measured by food intakes and body weight. The combinatory regiment of ACBP-L with a fewer doses of Cisplatin (5 mg/kg every 10 days) resulted in a similar anti-tumor activity with improved QOL. (18)F-FDG PET/CT scan was used to examine the biological activity in tumors of live animals and indicated the consistent treatment effects. The tumor tissues were harvested after treatment, and ACBP-L and Cisplatin treatment suppressed Bcl-2, and induced Bax, Caspase 3, and Caspase 8 molecules as detected by RT-PCR and immunohistochemistry. The combinatory regiment induced stronger Bax and Caspase 8 protein expression. CONCLUSION: Our current finding in this gastric cancer xenograft animal model demonstrated that ACBP-L could lower Cisplatin dose to achieve a similar anti-tumor efficacy as the higher dose of Cisplatin alone, through enhanced modulation of apoptotic molecules. This newly developed combination regiment improved QOL in tumor bearing hosts, which could lead to clinical investigation for the new strategy of combination therapy.