Integrins are heterodimeric membrane receptors composed of the α and β subunits. Integrins αvβ3 and αvβ5 are recognized as targets for tumor therapy, initially after it has been found to have increased expression in endothelial cells in angiogenesis and later because of increased expression in tumor cells. One of the available integrin inhibitors is cilengitide, a cyclic Arg-Gly-Asp peptide. Integrins do not have kinase activity, the signal in the cell is transmitted via protein kinases, and one of the most important is focal adhesion kinase (FAK). The aim of this graduation thesis was to investigate the combined effect of a specific inhibitor of integrins αvβ3 and αvβ5 cilengitide and antitumor drug paclitaxel in triple negative breast cancer and melanoma cell lines and to clarify the role of focal adhesion kinase in the signal pathway of αvβ3 and αvβ5 integrins. We have shown that cilengitide increased sensitivity of triple negative breast cancer cell lines MDA-MB-231 and MDA-MB-436 and melanoma cell lines A375, RPMI-7951 and MDA-MB-435S to paclitaxel, while in triple negative breast cancer cell line MDA-MB-468 and melanoma cell line MeWo we observed the opposite effect. We demonstrated a correlation between increased paclitaxel sensitivity and pFAK(Y397) inhibition in the melanoma cells, while similar correlation was not observed in the triple negative breast cancer cell lines. Given the unpublished results of the group in which this work was performed, in which silencing of integrin αv increased the sensitivity of five cell lines but did not decreased the sensitivity of any of them to paclitaxel, we conclude that silencing of integrin αv in combination with paclitaxel is a better combination that could provide better effect in therapy of these tumors.