Table 2.

Synergistic indexes of combination treatment with gefitinib and vorinostat in vivo

Xenografts	Gefitinib			Vorinostat			Gefitinib + vorinostat			Indexd
	Conc (mg/kg)	MGIa	P-valuee	Conc (mg/kg)	MGI	P-valuee	Expectedb	Observedc	P-valuee
H358	5	0.87	ns	100	0.80	ns	0.69	0.34	<0.01	2.02
PLC/PRF5	50	0.65	0.0193	100	1.02	ns	0.67	0.46	0.0002	1.46

Notes: Growth inhibition rate were calculated at the end of the experiment on established subcutaneous H358 or PLC/PRF5 tumor nodules in athymic nude mice treated with indicated concentrations of gefitinib, vorinostat, or their combination.

^aMean growth inhibition rate = growth rate of treated group/growth rate of untreated group

^bGrowth inhibition rate of gefitinib × growth rate of vorinostat.

^cGrowth inhibition rate of combined treatment on gefitinib and vorinostat treatments.

^dCalculated by dividing the expected growth inhibition rate by the observed growth inhibition rate. An index >1.1 indicates synergistic effect, between 0.9 and 1.1 indicates additive effect, and <0.9 indicated less than additive effect.

^eP-value was calculated by bilateral t-test compared to control treatment or to gefitinib or vorinostat alone (P>0.5).

Abbreviations: MGI, mean growth inhibition; ns, nonsignificant.