Expression of cellular adhesion molecules on human prostate tumor cell lines

By flow cytometric analysis we have examined the expression of cellular adhesion molecules (CAMs) on the surface of four different human prostate tumor cell lines: DU 145, from a brain metastasis; PC 3, from a bone metastasis; LNCaP.FGC, from a lymph node metastasis; and a primary tumor cell line, ND 1. The corresponding ligands for the expressed CAMs were, by and large, extracellular matrix proteins. We detected high-level expression of ICAM-1 on three of the four prostate cell lines, whereas LNCaP cells were negative. We observed unstable, heterogeneous expression of E-cadherin in the cell lines DU 145, PC 3, and ND 1. Flow cytometric cell sorting enabled us to divide PC 3 cells into negative and bright positive subpopulations but, after several cell divisions in culture, sorted cells returned to the original heterogeneous phenotype. The laminin-specific α₆β₄ integrin was not expressed by LNCaP, and was expressed at a low level and heterogeneously on DU 145 and PC 3 cell lines. In contrast, ND 1 cells, derived from a primary tumor, showed homogeneous and high-level expression of the α₆β₄ integrin. All of the prostate cell lines expressed the RGD-dependent binding of α₃β₁ and α₅β₁ integrins and did not reveal non-RGD-dependent α₄β₁ integrin expression. This finding provides a stimulus to investigate the inhibition capacity of RGD-containing peptides on the metastatic behavior of prostate tumor cells.