TABLE 2

Cytotoxicity of C-1305 and other topoisomerase II inhibitors toward DC-3F cells growing in two dimensions as monolayer cultures or in three dimensions as multicellular spheroids Cells were incubated with the indicated compounds for three to four generation times, and the cytotoxicity was determined by cell counting. All values are the average of at least two independent experiments, each done in duplicate.

Compound	IC₅₀^a		Δ^b
Compound	Monolayer	Spheroids	Δ^b
	nM
C-1305	27	91	3.4
C-1533	3217	4090	1.3
mAMSA	6.2	31	5.0
Etoposide	70	297	4.3
Doxorubicin	5.0	14	2.7

↵ a Concentration causing 50% cell growth inhibition
↵ b Ratio between IC₅₀ values of cells growing in multicellular spheroids and cells growing in monolayer cultures