Overcoming drug-resistant cancer by a newly developed copper chelate through host-protective cytokine-mediated apoptosis

Abstract

Purpose: Previously, we have synthesized and characterized a novel Cu(II) complex, copper N-(2-hydroxy acetophenone) glycinate (CuNG). Herein, we have determined the efficacy of CuNG in overcoming multidrug-resistant cancer using drug-resistant murine and human cancer cell lines. Experimental Design: Action of CuNG following single i.m. administration (5 mg/kg body weight) was tested in vivo on doxorubicin-resistant Ehrlich ascites carcinoma (EAC/Dox)–bearing mice and doxorubicin-resistant sarcoma 180–bearing mice. Tumor size, ascitic load, and survival rates were monitored at regular intervals. Apoptosis of cancer cells was determined by cell cycle analysis, confocal microscopy, Annexin V binding, and terminal deoxynucleotidyl transferase–mediated dUTP nick end labeling assay ex vivo. IFN-γ and tumor necrosis factor-α were assayed in the culture supernatants of in vivo and in vitro CuNG-treated splenic mononuclear cells from EAC/Dox-bearing mice and their apoptogenic effect was determined. Source of IFN-γ and changes in number of T regulatory marker-bearing cells in the tumor site following CuNG treatment were investigated by flow cytometry. Supernatants of in vitro CuNG-treated cultures of peripheral blood mononuclear cells from different drug-insensitive cancer patients were tested for presence of the apoptogenic cytokine IFN-γ and its involvement in induction of apoptosis of doxorubicin-resistant CEM/ADR5000 cells. Results: CuNG treatment could resolve drug-resistant cancers through induction of apoptogenic cytokines, such as IFN-γ and/or tumor necrosis factor-α, from splenic mononuclear cells or patient peripheral blood mononuclear cells and reduce the number of T regulatory marker-bearing cells while increase infiltration of IFN-γ-producing T cells in the ascetic tumor site. Conclusion: Our results show the potential usefulness of CuNG in immunotherapy of drug-resistant cancers irrespective of multidrug resistance phenotype.