Combination nitazoxanide and auranofin treatment has synergistic anticancer activity in anaplastic thyroid cancer through enhanced activation of oxidative stress that leads to apoptosis.

Anaplastic thyroid cancer (ATC) has one of the highest mortality rates of all human malignancies and has no cure. We used combination drug matrix screening of highly active compounds and identified that combination of nitazoxanide and auranofin was one of those with the highest synergistic anticancer activity. We investigated its synergistic anticancer activity and mechanism of action in preclinical ATC models. We performed in vitro, ex vivo, and in vivo ATC models to evaluate the synergistic anticancer activity and the mechanism of action of this combination. Combination nitazoxanide and auranofin treatment synergistically inhibited cellular proliferation, colony formation, and cellular migration compared to control and single agents. Combination treatment also significantly reduced ATC cell line and patient-derived ATC spheroid size. Nitazoxanide alone and in combination with auranofin caused ER stress and apoptosis. Auranofin alone and in combination with nitazoxanide induced activation of the ROS generating pathway. This led to enhanced increase in ROS and MDA levels with combination treatment associated with upregulation of HMOX-1 and cell death that was reversed by N-acetyl cysteine (NAC). The combination significantly inhibited tumor growth in vivo in 8505C ATC cells, and C643 ATC cells, without significant treatment-related toxicity. Combination nitazoxanide and auranofin treatment has synergistic anticancer activity in vitro, ex vivo, and in vivo in ATC, which is due to enhanced oxidative stress and induction of apoptosis compared to single-drug treatment. Both drugs are FDA approved; their combination is a potential candidate for evaluation in a clinical trial for ATC therapy.