Table 1. Cross-resistance between arsenic trioxide and other arsenic compounds in the NCI cell line panel.

	free As2O3	formulated As2O3
formulated As2O3	4.14×10−14*	N/A
potassium arsenite (KAsO2)	1.76×10−12*	2.51×10−9*
dihydro-1,3,2-dithiarsenol-2-ylmercapto-acetic acid	0.04565*	n.s.

Log₁₀ IC₅₀ values obtained from SRB assays have been subjected to Pearson’s correlation test.

N/A, not applicable; N.S. not significant (P>0.05). * denotes significant correlation.