Nck1 and Nck2 mRNA expression in human melanocytes and melanoma cells. (A) RT-PCR amplification performed on isolated RNA from human melanocyte and melanoma cells using specific primers for human Nck1, Nck2 and 18S. Shown are PCR products after 20 and 25 cycles of amplification. HEM: human normal melanocytes; WM278: human primary melanoma that rarely metastasis; WM164: human melanoma isolated from metastasis in lymph nodes; 451Lu: lung melanoma metastasis of WM164 injected in mice. 18S is used as control. (B) Ratios of Nck1 and Nck2 mRNA over 18S were calculated from quantification by densitometry of PCR amplification products in the linear range. Asterisk: p ≤ 0.001 compared to HEM, black triangle: p ≤ 0.001 compared to WM278.