Treatment of HNSC and pulmonary metastasis using the anti-helminthic drug niclosamide to modulate Stat3 signaling activity.

Head and neck squamous cell carcinoma (HNSC) is a dangerous cancer that represents an important threat to human health. Niclosamide is an anti-helminthic drug that has received FDA approval. In drug repurposing screens, niclosamide was found to inhibit proliferative activity for a range of tumor types. Its functional effects in HNSC, however, have yet to be established. MTT and colony formation assays were used to explore the impact of niclosamide on the proliferation of HNSC cells, while wound healing and Transwell assays were employed to assess migration and invasivity. Flow cytometry and Western immunoblotting were respectively used to assess cellular apoptosis and protein expression patterns. An HNSC xenograft tumor model system was used to evaluate the antitumor activity of niclosamide, and immunofluorescent staining was employed to assess cleaved Caspase3 and Ki67 expression. The ability of niclosamide to prevent metastatic progression was assessed with a model of pulmonary metastasis. These analyses revealed the ability of niclosamide to suppress HNSC cell migration, proliferation, and invasivity while promoting apoptotic death. From a mechanistic perspective, this drug suppressed Stat3 phosphorylation and β-catenin expression, while increasing cleaved Caspase3 levels in HNSC cells and reducing Bcl-2 levels. Importantly, this drug was able to suppress tumor growth and pulmonary metastasis formation, with immunofluorescent staining confirming that it reduced Ki67 levels and increased cleaved Caspase3 content. In conclusion, these analyses highlight the ability of niclosamide to inhibit HNSC cell migration and proliferative activity while provoking apoptotic death mediated via p-Stat3 and β-catenin pathway inactivation. Niclosamide thus holds promise for repurposing as a candidate drug for the more effective clinical management of HNSC.