Synergistic Effects of Simvastatin and Irinotecan against Colon Cancer Cells with or without Irinotecan Resistance

Table 2

Combination index values of simvastatin and irinotecan in HT-29 and HT-29R cells.

Drug combination	Ratio	Combination index of HT-29			Combination index of HT-29R
		IC50	IC75	IC90	IC50	IC75	IC90
Simvastatin : irinotecan	1 : 1	0.70	0.40	0.24	0.72	0.41	0.24
	1 : 2	0.68	0.48	0.34	0.43	0.22	0.01
	2 : 1	0.34	0.21	0.14	0.42	0.08	0.01
	1 : 4	0.83	0.60	0.43	0.46	0.07	0.01
	4 : 1	0.59	0.26	0.12	0.82	0.39	0.31

CI < 1 synergistic effect, CI = 1 additive effect, and CI > 1 antagonistic effect.