Table 1.

Anti-proliferative effects of CDDP, SAHA and VPA administered singly in three lung cancer cell lines (A549, NCIH-1563, NCI-H2170) measured in vitro by the MTT assay

Cell line	Drug	IC50 (μg/ml)	n	CFP	q/p	S.R.	f ratio S.R.	Parallelism*
A549	CDDP	1.184 ± 0.333	64	1.126 (q)	-	-	-	-
A549	SAHA	0.560 ± 0.069	80	2.301 (p1)	0.489	2.265	1.495	NP
A549	VPA	485.6 ± 87.95	64	1.424 (p2)	0.791	1.763	1.523	NP
NCI-H1563	CDDP	2.989 ± 0.577	75	5.237 (q)	-	-	-	-
NCI-H1563	SAHA	0.723 ± 0.169	80	0.626 (p1)	8.366	1.346	1.559	P
NCI-H1563	VPA	847.2 ± 203.0	104	2.104 (p2)	2.489	1.726	1.835	P
NCI-H2170	CDDP	0.350 ± 0.123	80	0.538 (q)	-	-	-	-
NCI-H2170	SAHA	0.460 ± 0.052	80	2.891 (p1)	0.186	4.542	1.607	NP
NCI-H2170	VPA	415.7 ± 51.87	64	2.218 (p2)	0.243	4.567	1.604	NP

Results are presented as median inhibitory concentrations (IC₅₀ values in μg/ml ± S.E.M.) of CDDP, SAHA and VPA administered singly with respect to their anti-proliferative effects in three cancer cell lines (A549, NCI-H1563, NCI-H2170) measured in vitro by the MTT assay. n-total number of items used at concentrations whose expected anti-proliferative effects ranged between 4 and 6 probits (16% and 84%); CFP-(q and p) curve-fitting parameters; q/p-ratio of q and p values; S.R.-slope function ratio (S_CDDP/S_SAHA, S_CDDP/S_VPA); f ratio S.R.-factor for slope function ratio. Test for parallelism of two dose-response relationship curves (DRRCs) was performed according to Litchfield and Wilcoxon (1949). It this case, if the slope function ratio (S.R.) value is higher than the factor for slope function ratio (f ratio S.R.) value, the examined two DRRCs are not parallel to each other. Otherwise, the examined two DRRCs are parallel to one another (Litchfield and Wilcoxon 1949). NP-not parallel; P-parallel;

^*All detailed calculations required to test the parallelism of two DRRCs were presented in the Appendix to the paper by Luszczki and Czuczwar (2006).