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Two-dimensional (2D) monolayer cell culture models are the most common method used to investigate tumor cells in vitro. In the few last decades, a multicellular spheroid model has gained attention due to its adjacency to tumors in vivo. The aim of the present study was to investigate immunohistochemical differences between these two cell culture systems. The FaDu, CAL27 and SCC25 head and neck squamous cell carcinoma (HNSCC) cell lines were seeded out in monolayer and multicellular spheroids. The FaDu and SCC25 cells were treated with increasing doses of cisplatin and irradiation. CAL27 cells were not used in theproliferation experiments, since the spheroids of CAL27 cells were not able to process the reagent in CCK-8 assays. Furthermore, they were stained to present alterations of the following antigens: Ki-67, vascular endothelial growth factor receptor, epithelial growth factor and survivin. Differences in growth rates and expression patterns were detected in certain HNSCC cell lines. The proliferation rates showed a significant divergence of cells grown in the three-dimensional model compared with cells grown in the 2D model. Overall, multicellular spheroids are a promising method to reproduce the immunohistochemical aspects and characteristics of tumor cells, and may show different response rates to therapeutic options.

Arsenic trioxide (ATO) has been approved for the treatment of relapsed acute promyelocytic leukaemia. The aim of this study was to determine whether ATO would lead to cell death in head and neck squamous cell carcinoma (HNSCC) cell lines and whether it was able to enhance the cytotoxicity of cisplatin, a standard chemotherapeutic agent. The four HNSCC cell lines SCC9, SCC25, CAL27 and FADU were treated with ATO or cisplatin alone or with ATO and cisplatin in combination. Cytotoxicity assays, immunohistochemistry, western blot analysis and flow cytometry were carried out. Possible interactions between the two drugs were calculated using the Chou-Talalay equation. Ther results demonstrated a synergistic cytotoxic effect of the combination of ATO and cisplatin at high doses. The two agents induced apoptosis in all four HNSCC cell lines. In conclusion, this study showed that ATO is a promising therapeutic drug with cytotoxic effects in HNSCC. We demonstrated a synergistic effect in the combined treatment with cisplatin at high doses.

Although head and neck cancer is a common malignancy, investigations have not yet improved the poor prognosis of patients. Therefore, it is important to find new cancer treatment modalities. Recent studies showed that cyclooxygenase, especially its isoform cyclooxygenase-2, is involved in tumorigenesis, tumor growth and metastasis. Inhibition of this enzyme by cyclooxygenase inhibitors has been shown to be antiproliferative in numerous cancer cell lines. The aim of this study was to investigate if the selective cyclooxygenase-2 inhibitor nimesulide could enhance cytotoxicity of the standard chemotherapeutic agent cisplatin. Head and neck squamous cell cancer cells were incubated with nimesulide and/or cisplatin, and counted after 24, 48 and 72 h treatment. Visualization of apoptotic cells was done by immunohistochemistry. We demonstrated that nimesulide inhibits the cytotoxic effect of cisplatin in HNSCC cells. Therefore, COX-2 inhibitor nimesulide may not be a good partner for cisplatin in combination therapy for cancer.