Table 3. Combination index values (CI) values calculated from cellular proliferation assays of SK-ES-1R chemoresistant cells treated with K252a, VCR, VP-16, and Doxo alone or in combination.

Drugs (concentrations)	CI	Interpretation
VCR (1 nM) + K252a (1 nM)	0.218	Strong synergism
VCR (2 nM) + K252a (1 nM)	0.573	Synergism
VCR (1 nM) + K252a (100 nM)	0.381	Synergism
VCR (2 nM) + K252a (100 nM)	0.588	Synergism
VP-16 (0.01 μM) + K252a (1 nM)	0.094	Very strong synergism
VP-16 (0.1 μM) + K252a (1 nM)	0.697	Synergism
VP-16 (0.01 μM) + K252a (100 nM)	0.229	Strong synergism
VP-16 (0.1 μM) + k252a (100 nM)	0.798	Moderate synergism
Doxo (10 nM) + K252a (1 nM)	0.344	Synergism
Doxo (20 nM) + K252a (1 nM)	0.605	Synergism
Doxo (10 nM) + K252a (100 nM)	0.995	Nearly additive
Doxo (20 nM) + K252a (100 nM)	0.749	Moderate synergism