Table 5. Effects of various drug combinations on proliferation of myeloma cell lines.

Drug combinations	Drug interactions produced in
	MM.1S	NCI-H929	OPM-2	RPMI-8226	U-266
17AAG and BI2536	s	an	s	s	s
17AAG and BEZ235	s	an	s	s	s
17AAG and obatoclax	s	s	s	s	an
BI2536 and BEZ235	s	s	s	s	an
BI2536 and obatoclax	s	an	s	s	an
BEZ235 and obatoclax	s	ad	an	s	an

To determine potential additive or synergistic drug effects, MM cell lines were exposed to 17AAG, BI2536, BEZ235, and obatoclax, alone or in combination at a fixed ratio of drug concentrations at 37°C for 48 hours. Proliferation was measured by analyzing ³H-thymidine uptake. Drug interactions (synergistic = s, additive = ad, and antagonistic = an) were calculated by CalcuSyn software. A combination index (CI) of <1 indicates synergism, CI values of 1 indicate additive effects, and CI values >1 indicate antagonistic drug effects.