In order to determine the inhibition rate of cell viability, measured by MTT assay, per dose of gemcitabine and fucoidan, log-probit linear regression analysis was performed according to method described by Litchfield and Wilcoxon [17 (
link),18 (
link)]. Median inhibitory concentrations (IC
50) for gemcitabine and fucoidan in ESS-1, SK-UT-1, and SK-UT-1B cell lines were calculated according to method previously described [19 (
link)]. Due to lack of cells response, the IC
50 was not achievable for fucoidan in MES-SA cell line [10 (
link)]. Parallelism between dose–response curves for gemcitabine and fucoidan in ESS-1, SK-UT-1, and SK-UT-1B cell lines was confirmed by log-probit method, as it was described in detail previously [18 (
link)]. Next, isobolographic analysis of interactions between drugs for the combination of gemcitabine and fucoidan in tested cell lines were performed according to the method presented by i.a. Tallarida et al. [20 (
link)]. The median additive inhibitory concentrations (IC
50 add) for two-drug mixtures were theoretically calculated according to the method described elsewhere [20 (
link)]. The calculated values were used for performing MTT tests on ESS-1, SK-UT-1, and SK-UT-1B cell lines—the assessment of experimentally derived IC
50 mix values for tested drug combinations in a fixed 1:1 ratio. The particular drug concentrations (gemcitabine and fucoidan) in the mixture were calculated by multiplying IC
50 mix values accordingly to proportions in additive mixture. Detailed description of isobolographic method was introduced by Tallarida, Grabovsky and Luszczki [20 (
link),21 (
link),22 (
link)]. The results of MTT test were analyzed by one-way ANOVA test, Tukey’s Multiple Comparison Post-test using GraphPad Prism 5.0 (GraphPad Softwere Inc., San Diego, CA, USA). The
p < 0.05 was considered as statistically significant.
Bobiński M., Okła K., Łuszczki J., Bednarek W., Wawruszak A., Moreno-Bueno G., Dmoszyńska-Graniczka M., Tarkowski R, & Kotarski J. (2019). Isobolographic Analysis Demonstrates the Additive and Synergistic Effects of Gemcitabine Combined with Fucoidan in Uterine Sarcomas and Carcinosarcoma Cells. Cancers, 12(1), 107.