Background: Interactions of cancer cells with endothelium are a crucial step in metastatic invasion. RGD-recognizing integrins play a definitive role in these interactions.
Methods: Fluorescence-activated cell sorting (FACS) analysis of RGD-sensitive integrins in prostate epithelial cells was performed. Attachment inhibition assay was used to characterize functionality of particular integrins. Potential partners for RGD-binding integrins in human umbilical vein endothelial cells (HUVEC) were identified by Western blotting and attachment inhibition assay. To determine the RGD-flanking amino acids optimal for interactions with prostate cell integrins, these cells were biopanned with a phage library.
Results: Different expressions of RGD-recognizing integrins and distinctions in RGD-dependent adhesion of nonmalignant and cancer cells were observed. Cancer but not control cells were detached from culture plastic by incubation with RGD peptide. Adhesion of carcinoma cells to HUVEC was RGD-sensitive, in contrast to nonmalignant cells. Antibodies against alpha3, alpha5, beta1, and alpha(v)beta3 inhibited interactions of carcinoma cells with HUVEC. Potential ligands for alpha5beta1, alpha3beta1, and alphaVbeta3 integrins, fibronectin, and vitronectin, were detected on the HUVEC surface. Several phages which preferentially bound to the surface of particular prostate cells were selected.
Conclusions: Interactions of prostate carcinoma with endothelium are mediated in part via alpha5beta1, alpha3beta1, and alpha(v)beta3 integrins. Because these interactions are RGD-sensitive, synthetic RGD peptides with optimized flanking amino acids can potentially be used as antimetastatic agents.