BACKGROUND : Integrins are highly attractive targets in oncology due to their involvement in angiogenesis in a wide spectrum of cancer entities. Among several integrin inhibitors, cilengitide is suggested to be one of the most promising inhibitors. However, little is known about the cellular processes induced during cilengitide chemotherapy in head and neck squamous cell carcinoma (HNSCC). METHODS : For the current study, 3 HNSCC cell lines, SCC4, SCC15 and SCC25; and 3 primary culture cells, TU53, TU57, and TU63 were used. CD90, cytokeratin, and vimentin were stained immunohistochemically to identify the biological characteristics of these cell lines and primary culture cells and the cytostatic effect of cilengitide was evaluated. Quantitative polymerase chain reaction (qPCR) arrays were applied to evaluate target protein genes ITGAV, ITGB3, and ITGB5 of integrin αvβ3 and αvβ5 at respective concentrations of 50 and 100 μM cilengitide for 72 h. RESULTS : Cilengitide has significantly inhibited the proliferation of HNSCC cells in a dose-dependent way. At the same concentration, cilengitide suppressed the proliferation of primary culture cells even more strongly than it did that of cell lines, suggesting that primary culture cells retain more of their internal biological characteristics than do cell lines. qPCR assay detected downregulation of ITGAV, ITGB3, and ITGB5 gene expression after exposure to 50 μM of cilengitide. However, after exposure to 100-μM cilengitide, expression of these genes significantly increased both in cell lines and primary culture cells. CONCLUSIONS : RGD-containing small-molecule synthetic peptides might be considered in tumor chemotherapy in the near future. The different reactions of primary culture cells and cell lines demonstrated that individualized chemotherapy plans may be a feasible option. However, research on the role of cilengitide in HNSCC therapy is still in its early stages, and further investigations are required.