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

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-gamma and tumor necrosis factor-alpha 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-gamma 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-gamma 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-gamma and/or tumor necrosis factor-alpha, 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-gamma-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.

A new Mad2-interacting domain of Cdc20 is critical for the function of Mad2-Cdc20 complex in the spindle assembly checkpoint.

Interaction between Mad2 and Cdc20 (cell division cycle 20) is a key event during spindle assembly checkpoint activation. In the past, an N-terminal peptide containing amino acid residues 111-150 of Cdc20 was shown to bind Mad2 much better than the full-length Cdc20 protein. Using co-localization, co-immunoprecipitation and peptide inhibition analysis with different deletion mutants of Cdc20, we identified another Mad2-binding domain on Cdc20 from amino acids 342-355 within the WD repeat region. An intervening region between these two domains interferes with its Mad2 binding when present individually with any of these two Mad2-binding sites. We suggest that these three domains together determine the overall strength of Mad2 binding with Cdc20. Functional analysis suggests that an optimum Mad2 binding efficiency of Cdc20 is required during checkpoint arrest and release. Further, we have identified a unique polyhistidine motif with metal binding property adjacent to this second binding domain that may be important for maintaining the overall conformation of Cdc20 for its binding to Mad2.