TSPAN1 is revealed as a protein involved in head and neck squamous cell carcinoma (HNSCC) chemoresistance and proliferation. (A) The proteomic study identified 36 proteins commonly deregulated in CSCs and CDDP-resistant cells compared with parentals (P) cells, TSPAN1 was one of the most highly upregulated protein. (B) Western blot analysis of TSPAN1 expresion in four different HNSCC cells (CCL-138, JHU029, HTB-43 and SCC-25). (C) Western blot analysis confirmed proteomic data verifying increased TSPAN1 expression in CDDP-resistant cells; and CSC G2 and G3 from the HTB-43 cell line. (D) TSPAN1 mRNA levels in parental and CDDP-resistant HNSCC cells upon TSPAN1 depletion. Data were normalized to IPO8 (endogenous control), and relative to NC (negative control or scramble) cells assigned the value of 1. TSPAN1 mRNA level for CSC from HTB-43 and CCL-138 cell lines was also assessed. Unpaired two-tailed Student’s t-test, *** (p < 0.001). (E) Proliferation curves of cells transduced with siTSPAN1 vs. non-targeted siRNA control (NC) are shown. (F) Colony number quantification of HNSCC cell lines transduced with siTSPAN1 compared to the respective NC controls. Unpaired two-tailed Student’s t-test, * (p < 0.05), ** (p < 0.01), *** (p < 0.001). OD: Optical Density measured at 595 nm (Crystal violet).