Pingyangmycin downregulates the expression of EGFR and enhances the effects of cetuximab on esophageal cancer cells and the xenograft in athymic mice

As reported, epidermal growth factor receptor (EGFR) is over expressed in a variety of cancers including esophageal squamous cell carcinoma. Therefore, it becomes one of the potential targets for treating esophageal cancer. Pingyangmycin (PYM), a single A5 component of bleomycin, is currently used for the treatment of different types of cancers of epidermal origin, especially for head and neck cancers. In this report, the effect of PYM on EGFR expression in human esophageal cancer cells and the therapeutic efficacy of the combination of PYM and cetuximab on esophageal cancer xenograft were investigated. The effects of PYM, cetuximab and the combination on EGFR signaling, proliferation, cell cycle, apoptosis were evaluated by using MTT, Western blotting, RT-PCR assays and flow cytometry assays, respectively, in vitro and the therapeutic efficacy by a xenograft model in athymic mice. Cell volume and nucleus were enlarged after PYM treatment. PYM showed potent cytotoxicity in both cell lines of Kyse-150 and Eca-109 in time and dosage-depended manner in MTT assay. PYM treatment induced G(2)/M phase arrest and apoptosis. Notably, the expression of EGFR was down-regulated by PYM in EGFR highly expression esophageal cancer cells. PYM plus cetuximab resulted in a potentiation of antiproliferative activity. PYM combined with cetuximab displayed a much higher therapeutic effect than that of the single agent on esophageal cancer xenograft in athymic mice. PYM could down-regulate the expression of EGFR in esophageal cancer cells and potentiate the effects of cetuximab on esophageal cancer xenograft in nude mice. The combination of PYM and cetuximab, the EGFR-targeted combination of a chemotherapeutic agent and an antibody-based drug, might be useful in cancer therapy.