Qualitative RT-PCR analysis of Hh pathway gene expression in precursor B-ALL cell lines. HFB, human fetal brain, used as positive control for all experiments. For each cell line, positive and negative control reactions were run with B-actin primers with (to demonstrate equal amounts of cDNA template across each cell line) and without (to rule out contamination with genomic DNA) reverse transcriptase. B-ACTIN- denotes PCR results from mock cDNA synthesis reactions lacking RT. Precursor B-ALL cell lines: HB 1119 (t11;19), Nalm6 (t2;6), REH (t12;21), RS4;11 (MLL gene rearrangement); SEM-K2 (MLL gene rearrangement), TOM-1 (Ph+). Electrophoresis was performed with each gene separately across the panel of cell lines. The separate gels are shown together for the purpose of clarity across cell lines in the figure.