Table 1. Icaritin enhances the radiosensitivity of murine 4T1 breast cancer cells.

Icaritin	D0 (Gy)	SF2	ER	CI*	DRI*
0 µM	5.5	0.87
1.5 µM	4.8	0.85	1.30	4.95	0.20
3 µM	4.7	0.83	1.18	0.39	2.51
6 µM	3.7	0.62	1.28	0.19	5.07

D₀, incremental dose required for reducing the fraction of colonies to 37%, indicative of single-event killing; SF2, surviving fraction of exponentially growing cells when irradiated at the clinically relevant dose of 2 Gy; ER, enhancement ratio; CI, combination index; DRI, dose reducing index.

^*CI <1 and DRI >1 indicate a synergistic cytotoxic effect of icaritin and radiation.