Table 2. Interaction ratios in the GFP assay of drug and radiation combinations in HCT116 GFP cells cultured as spheroids for 7 days then incubated with drugs for 7 days with irradiation (6 Gy) at 4–6 h after addition of drug.

SIo/SIe	5-FU	Oxaliplatin	Deferoxamine	Ciclopirox	Salinomycin	Tirapazamine	VLX50	VLX60	VLX600
Highest conc.	0.97	1.02	0.96	N/A	N/A	1.09	0.92	N/A	1.05
	1.01	0.98	1.02	N/A	N/A	1.04	0.84*	N/A	1.00
	0.97	1.02	0.94	N/A	N/A	1.09	0.89*	N/A	0.94
	1.02	1.00	0.99	1.01	N/A	1.03	1.04	N/A	0.89*
	0.98	0.99	1.01	1.02	N/A	1.02	0.95	1.05	0.85*
	0.99	0.97	1.01	1.00	N/A	1.08*	0.98	1.02	0.85*
	1.01	0.99	0.98	1.02	1.33	1.03	1.00	0.98	0.86*
	1.01	1.01	1.00	0.98	1.04	1.04	0.98	0.99	0.93
Lowest conc.	1.04	0.99	1.02	1.01	1.08	1.01	1.00	0.94*	1.02

One-sample t-test. Mean interaction ratios (SI_o/SI_e) significantly different than 1.0 (two-tailed p-value <0.05) are shown with an asterisk. Mean interaction ratios (SI_o/SI_e) less than 1 indicates synergy and are shown in bold. Mean values are based on 3–8 independent experiments, with duplicate wells for each drug concentration. For drug concentrations, see Table 1. N/A, SI_d ≤25%.