Disulfiram with or without metformin exhibits potent anti-cancer effects toward oesophageal squamous cell carcinoma in vivo.


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Rupal Jivan1,Jade Peres2,Leonard Damelin3,Sharon Prince2,Demetra Mavri-Damelin1
1University of the Witwatersrand,2University of Cape Town,3National Institute for Communicable Diseases

Abstract

Background

Drug repurposing has become an attractive approach for cancer therapy as it takes advantage of established drug tolerance profiles and shorter time to clinic. We investigated disulfiram (DSF), a chronic alcoholism drug, in combination with the anti-diabetic drug, metformin, for the treatment of oesophageal squamous cell carcinoma (OSCC). We previously showed that DSF alone and in combination with metformin exhibited anti-cancer activity in OSCC cell lines via inhibition of protein degradation pathways. In this study, we observed the effects of DSF, with and without metformin, in vivo. 

Method

Nude mice were injected subcutaneously with 1x106 WHCO1 cells. Once tumours reached 200mm3 mice were randomly divided into groups (n=5) and administered 30 mg/kg or 50 mg/kg DSF three times per week, with or without metformin (100µg/ml) in the drinking water. Mice were observed and tumour volumes recorded over three weeks, in comparison to controls. At the end of the study, excised tumours were weighed then divided for snap-freezing and formalin fixation for further analysis, including proteasome and western blot analyses.

Results

DSF exhibited potent anti-cancer effects toward OSCC xenografts. After three weeks, tumour mass in DSF-treated mice was significantly smaller than untreated mice, and similar to control and OSCC treatment choice, cisplatin (Results expressed as percentage of untreated: 30mg/kg DSF, 36±25%; 50mg/kg DSF, 39±13%;  30mg/kg DSF + Metformin, 48±28%; and 50mg/kg DSF + Metformin, 31±22%; Cisplatin, 34±5%). Chymotrypsin-like proteasome activity was significantly lower after treatment (Emission 460nm: Vehicle, 7.39±0.08; 30mg/kg DSF, 5.05±0.28; 50mg/kg DSF, 5.68±0.87;  30mg/kg DSF + Metformin, 4.45±0.78; and 50mg/kg DSF + Metformin, 6.00±1.31) and higher levels of ubiquitinated proteins were observed after DSF treatment. Preliminary findings indicate that there is an increase in LC3B-II and LAMP1 in the presence of DSF or DSF and metformin. 

Conclusion

These findings indicate that DSF inhibits tumour growth in vivo by inhibiting protein degradation pathways.