Figure 4.

Log-probit analysis of dose-response curves of cisplatin (CDDP) and suberoylanilide hydroxamic acid (SAHA), administered alone and in combination at the fixed-ratio of 1:1, illustrating the anti-proliferative effects of the drugs in the RK33 (A) and RK45 (B) larynx cancer cell lines measured in vitro by the MTT assay. Doses of CDDP and SAHA were transformed into logarithms and the anti-proliferative effects produced by the drugs into probits according to Litchfield and Wilcoxon ¹⁹. Linear regression equations of dose-response curves are presented on the graph, where: y - is the probit of response, and x - is the logarithm (to the base 10) of a drug dose, R² - coefficient of determination. According to the test for parallelism, the experimentally determined dose-response curves for CDDP and SAHA were not parallel to one another.