Comparative gene expression analysis of putative oncogenes and tumor suppressor genes. A: Comparative gene expression analysis utilizing qPCR data of putative tumor suppressor genes (CST6, DSC3, PITX1, POU2F3) and oncogenes (GDF15, SPP-1) in PCM (n = 7) and MM (n = 13) samples. Relative quantitation of target gene expression for each sample was determined using the equation 2-ΔΔCt, where GAPDH was used as the internal reference and normal skin as the calibrator. Values were Log base 10 transformed (y-axis) so that all values below zero represent a down-regulation in gene expression and values above zero represent an up-regulation in gene expression, compared to normal skin. B: Correlative microarray analysis of gene expression levels in primary and metastatic melanoma samples compared with normal skin. The statistical differences of gene expression between primary (PCM) and metastatic melanoma (MM) samples were analyzed by Wilcoxon's signed rank test; two-tailed significance level was set at α = 0.05. Compared to PCM samples (n = 7), the expression levels of 4 putative tumor suppressor genes (CST6, p < 0.0001; DSC3, p < 0.0001; PITX1, p = 0.0043, POU2F3, p < 0.0001) were significantly decreased in MM samples (n = 40), while the expression of putative oncogenes (GDF15, p = 0.0027; SPP1, p < 0.0001) were significantly increased in MM samples.