Background:Triple-negative breast cancer (TNBC) has significantly worse prognosis. Acquired chemoresistance remains the major cause of therapeutic failure of TNBC. In clinic, the relapsed TNBC is commonly pan-resistant to various drugs with completely different resistant mechanisms. Investigation of the mechanisms and development of new drugs to target pan-chemoresistance will potentially improve the therapeutic outcomes of TNBC patients.Methods:In this study, 1-(4,5-Dimethylthiazol-2-yl)-3,5-diphenylformazan (MTT), combination index (CI)–isobologram, western blot, ALDEFLUOR analysis, clonogenic assay and immunocytochemistry were used.Results:The chemoresistant MDA-MB-231PAC10 cells are highly cross-resistant to paclitaxel (PAC), cisplatin (CDDP), docetaxel and doxorubicin. The MDA-MB-231PAC10 cells are quiescent with significantly longer doubling time (64.9 vs 31.7 h). This may be caused by high expression of p21Waf1. The MDA-MB-231PAC10 cells express high aldehyde dehydrogenase (ALDH) activity and a panel of embryonic stem cell-related proteins, for example, Oct4, Sox2, Nanog and nuclealisation of HIF2α and NF-κBp65. We have previously reported that disulfiram (DS), an antialcoholism drug, targets cancer stem cells (CSCs) and enhances cytotoxicity of anticancer drugs. Disulfiram abolished CSC characters and completely reversed PAC and CDDP resistance in MDA-MB-231PAC10 cells.Conclusion:Cancer stem cells may be responsible for acquired pan-chemoresistance. As a drug used in clinic, DS may be repurposed as a CSC inhibitor to reverse the acquired pan-chemoresistance.

Breast cancer stem cells (BCSCs) are pan-resistant to different anticancer agents and responsible for cancer relapse. Disulfiram (DS), an antialcoholism drug, targets CSCs and reverses pan-chemoresistance. The anticancer application of DS is limited by its very short half-life in the bloodstream. This prompted us to develop a liposome-encapsulated DS (Lipo-DS) and examine its anticancer effect and mechanisms in vitro and in vivo.The relationship between hypoxia and CSCs was examined by in vitro comparison of BC cells cultured in spheroid and hypoxic conditions. To determine the importance of NFκB activation in bridging hypoxia and CSC-related pan-resistance, the CSC characters and drug sensitivity in BC cell lines were observed in NFκB p65 transfected cell lines. The effect of Lipo-DS on the NFκB pathway, CSCs and chemosensitivity was investigated in vitro and in vivo.The spheroid cultured BC cells manifested CSC characteristics and pan-resistance to anticancer drugs. This was related to the hypoxic condition in the spheres. Hypoxia induced activation of NFκB and chemoresistance. Transfection of BC cells with NFκB p65 also induced CSC characters and pan-resistance. Lipo-DS blocked NFκB activation and specifically targeted CSCs in vitro. Lipo-DS also targeted the CSC population in vivo and showed very strong anticancer efficacy. Mice tolerated the treatment very well and no significant in vivo nonspecific toxicity was observed.Hypoxia induced NFκB activation is responsible for stemness and chemoresistance in BCSCs. Lipo-DS targets NFκB pathway and CSCs. Further study may translate DS into cancer therapeutics.

The anticancer activity of disulfiram (DS) is copper(ii) (Cu)-dependent.

Disulfiram (DS), an anti-alcoholism drug, shows very strong cytotoxicity in many cancer types. However its clinical application in cancer treatment is limited by the very short half-life in the bloodstream. In this study, we developed a poly lactic-co-glycolic acid (PLGA)-encapsulated DS protecting DS from the degradation in the bloodstream. The newly developed DS-PLGA was characterized. The DS-PLGA has very satisfactory encapsulation efficiency, drug-loading content and controlled release rate in vitro. PLGA encapsulation extended the half-life of DS from shorter than 2 minutes to 7 hours in serum. In combination with copper, DS-PLGA significantly inhibited the liver cancer stem cell population. CI-isobologram showed a remarkable synergistic cytotoxicity between DS-PLGA and 5-FU or sorafenib. It also demonstrated very promising anticancer efficacy and antimetastatic effect in liver cancer mouse model. Both DS and PLGA are FDA approved products for clinical application. Our study may lead to repositioning of DS into liver cancer treatment.