Expression of Antimicrobial Peptides by Uveal and Cutaneous Melanoma Cells and Investigation of Their Role in Tumor Cell Migration and Vasculogenic Mimicry

Aims: Antimicrobial peptides (AMPs) have been implicated in the pathogenesis of several cancers, although there is also evidence suggesting potential for novel, AMP-based antitumor therapies. Discerning potential roles of AMPs in tumor pathogenesis may provide valuable insight into the mechanisms of novel AMP-based antitumor therapy.

Methods: mRNA expression of the AMPs α defensin (HNP-1); cathelicidin (LL-37); and β defensins (hBD-1, hBD-2, hBD-3, hBD-4) in human uveal and cutaneous melanoma cell lines, primary human uveal melanocytes, and primary human uveal melanoma cells was determined by reverse transcriptase polymerase chain reaction. An in vitro scratch assay and custom Matlab analysis were used to determine the AMP effects on melanoma cell migration. Last, the effect of specific AMPs on vasculogenic mimicry was determined by three-dimensional (3D) culture and light and fluorescence microscopy.

Results: Low-to-moderate AMP transcript levels were detected, and these varied across the cells tested. Overall, LL-37 expression was increased while hBD-4 was decreased in most melanoma cell lines, compared to primary cultured uveal melanocytes. There was no observable influence of HNP-1 and LL-37 on tumor cell migration. Additionally, aggressive cutaneous melanoma cells grown in 3D cultures exhibited vasculogenic mimicry, although AMP exposure did not alter this process.

Conclusions: Collectively, our data show that although AMP mRNA expression is variable between uveal and cutaneous melanoma cells, these peptides have little influence on major characteristics that contribute to tumor aggressiveness and progression.