Effect of sulfasalazine on human neuroblastoma: analysis of sepiapterin reductase (SPR) as a new therapeutic target

Table 3 Combination treatment of SSZ and DFMO in SK-N-Be(2)c and LAN-5 cells for 48 h

	Concentration, IC₅₀ Equivalent
NB Cell Line	SSZ	DFMO	Combination Index at 50 % Effect Level	Evaluation at 50 % Effect Level	SSZ IC₅₀ (μM)	DFMO (mM)
SK-N-Be(2)c	*0.408*	*0.425*	*0.834*	*slight synergism*	*54.360*	*1.800*
	*0.223*	*0.614*	*0.837*	*slight synergism*	*29.640*	*2.600*
	0.314	0.803	1.117	moderate antagonism	41.740	3.400
	0.140	0.992	1.132	moderate antagonism	18.700	4.200
	0.415	1.181	1.595	antagonism	55.180	5.000
LAN-5	*0.004*	*0.207*	*0.211*	*strong synergism*	*1.207*	*1.200*
	*0.173*	*0.311*	*0.484*	*synergism*	*58.250*	*1.800*
	*0.015*	*0.466*	*0.482*	*synergism*	*5.152*	*2.700*
	0.439	0.691	1.130	moderate antagonism	147.900	4.000
	0.003	1.037	1.039	additive	0.893	6.000

Legend: The concentration in IC₅₀ equivalent of SSZ was calculated by dividing the IC₅₀ of SSZ with DFMO combination from its corresponding single-agent IC₅₀ value (IC₅₀ of SSZ w/ DFMO comb/SSZ IC₅₀). For DFMO, the concentration in IC₅₀ equivalent was calculated by dividing its actual concentration used in the combination treatment from its corresponding single-agent IC₅₀ value (DFMO/ DFMO IC₅₀). Combination index (CI) at 50 % effect level is calculated by adding the IC₅₀ equivalent concentration of SSZ and DFMO. CI >1.3 is antagonism; CI = 1.1-1.3 is moderate antagonism; CI = 0.9-1.1 is additive; CI = 0.8-0.9 is slight synergism; CI = 0.6-0.8 is moderate synergism; CI = 0.4-0.6 is synergism; CI = 0.2-0.4 is strong synergism. Synergism was detected at two different combinations of DFMO and SSZ in SK-N-Be(2)c cells and three different combinations in LAN-5 cells (bold italics). The data present the average of three independent experiments performed in duplicate (n = 6)

ISSN: 1471-2407