Introduction. Prostate cancer (PCa) is the most commonly diagnosed cancer in Australia. The progression of PCa is usually protracted but when metastases occur, disease progression is rapid and resistant to therapeutic intervention. The human cathelicidin-derived antimicrobial peptide, hCAP18/LL-37 is found in prostatic fluid in concentrations approximately 90-fold higher than the level found in blood plasma (90μg/ml vs 1.2μg/ml). LL-37 has been implicated in tumourigenesis and metastasis of lung, breast and ovarian cancer. However, the role of LL-37 in prostate cancer remains largely unexplored
Aims. To characterise the impact of LL-37 on PCa cell migration and the receptors involved.
Methods. The effect of LL-37 on the 2D and 3D migration of PC-3 and DU145 cell lines was assessed using a scrape wound closure assay and a modified Boyden chamber assay. The receptor dependence of the LL-37 effect was probed using agonists and antagonists of the formyl peptide receptor (FPR2), purinoceptors and the epidermal growth factor receptor (EGFR). Proliferation and cytotoxicity of LL-37 was assessed using Reazurin, a fluorescent indicator of mitochondria activity.
Results. LL-37 (0.1nM-10μM) concentration-dependently inhibited serum-induced wound closure by PC-3 cells. Migration of DU-145 cells into the scraped wound was not inhibited by LL-37 except at 10μM, which was cytotoxic. However, LL-37 (0.1 and 1μM) attenuated the migration of DU-145 cells in the Boyden chamber. The purinoceptor agonist, ATP (10-1000μM), but neither adenosine (1nM-10μM) nor UTP (10nM-100μM), inhibited wound closure by PC-3 cells (P<0.01). Furthermore, the relatively non-selective purinoceptor antagonist, suramin (60μM), attenuated the effect of only a high concentration of LL-37 (10μM).
Discussion. Our findings showed a novel anti-migratory effect of LL-37 and ATP. Impairment of PCa cell migration in vivo may engender an anti-metastatic effect of LL-37