CXCR4 and CXCL12 (SDF-1) in prostate cancer: inhibitory effects of human single chain Fv antibodies.

PURPOSE Metastasis is a major cause of morbidity in prostate cancer (PCa). Several studies have shown that the chemokine receptor CXCR4 and its ligand, CXCL12 (stromal cell-derived factor-1), regulate tumor cell metastasis to specific organs. Recently, it was demonstrated that CXCL12 enhances PCa cell adhesion, migration, and invasion, implicating CXCR4 in PCa metastasis. In this study, we examined the inhibitory effects of anti-CXCR4 antibodies on CXCL12-mediated PCa cell activities. EXPERIMENTAL DESIGN We developed fully human single chain Fv antibodies (scFv), Ab124 and Ab125, against CXCR4 using the yeast two-hybrid system. We performed immunofluorescent staining, flow cytometry, and ELISA-binding assays to measure scFv binding to PCa cells. We also examined the effects of scFv on CXCL12-mediated calcium mobilization, cell migration, and invasion. RESULTS Our results confirmed that PCa cell lines express cell-surface CXCR4. Real-time quantitative reverse transcription-PCR and immunohistochemical staining also verified that CXCR4 is expressed in primary cultures of prostate epithelial cells from adenocarcinomas and in human prostate tissues. Ab124 and Ab125 demonstrated specific binding to PCa cell lines by flow cytometry and in binding assays. Preincubation with scFv resulted in significant reduction of CXCL12-induced calcium mobilization in PC-3 and LNCaP cells. Ab124 and Ab125 also inhibited PCa cell migration toward CXCL12, as well as invasion through extracellular matrix gels. CONCLUSIONS Ab124 and Ab125 inhibit CXCL12-mediated cellular activities by binding the receptor CXCR4. Recombinant scFv are an efficient mode of targeting tumor antigens. Considering the high incidence of PCa, the development of fully human scFv may be a useful therapeutic approach in the prevention and treatment of PCa metastasis.