. 2011 Nov 24;13(6):R120. doi: 10.1186/bcr3063

Table 1.

Combination index of apoptosisa

	α-TEA:TAM	CI^c
	Ratio^b	ED₅₀	ED₇₅	ED₉₀	Mean + SD^d
MCF-7/TAMR	20:1	0.59	0.59	0.59	0.59 ± 0.00	Synergism^a
MCF-7/HER-2	20:1	0.68	0.80	0.94	0.81 ± 0.13	Synergism^a

^aMCF-7/TAMR and MCF-7/HER-2 human breast cancer cells were treated with different concentrations of α-TEA and TAM alone and in combinations for 24 hours. Apoptosis was determined as described in Material and Methods. ^bThe ratio for concentrations used in combination treatments were determined from data in Figure 3b and c. ^cFor each combination treatment, a combination index (CI) was calculated by using methods as described previously and by using the commercially available software (CalcuSyn; Biosoft, Manchester, United Kingdom). ^dThe mean ± standard deviation (SD) is calculated from the CI values of effective dosages (EDs) that produced 50%, 75%, and 90% apoptosis. ^eCI values <1.0 indicate synergism; CI values of 1.0 indicate additive effect; and CI values >1.0 indicate antagonism. α-TEA, RRR-α-tocopherol ether-linked acetic acid analogue; MCF-7/HER-2, clone 18 MCF-7 cells overexpressing HER-2; MCF-7/TAMR, acquired tamoxifen-resistant MCF-7; mER, membrane estrogen receptor; TAM, tamoxifen.