The Barrier Molecules Junction Plakoglobin, Filaggrin, and Dystonin Play Roles in Melanoma Growth and Angiogenesis.

Abstract

MINI: We identified a set of genes, filaggrin (FLG), dystonin (DST), junction plakoglobin (JUP), and plakophilin-3 (PKP3), which are involved in cell-cell adhesions and associated with poor survival in melanomas. FLG, DST, and JUP support melanoma cell growth. The growth-promoting effects of JUP may be due to enhanced angiogenesis.\n\n\nOBJECTIVE\nTo understand role of barrier molecules in melanomas.\n\n\nBACKGROUND\nWe have reported poor patient survival and low immune infiltration of melanomas that overexpress a set of genes that include filaggrin (FLG), dystonin (DST), junction plakoglobin (JUP), and plakophilin-3 (PKP3), and are involved in cell-cell adhesions. We hypothesized that these associations are causal, either by interfering with immune cell infiltration or by enhancing melanoma cell growth.\n\n\nMETHODS\nFLG and DST were knocked out by CRISPR/Cas9 in human DM93 and murine B16-F1 melanoma cells. PKP3 and JUP were overexpressed in murine B16-AAD and human VMM39 melanoma cells by lentiviral transduction. These cell lines were evaluated in vitro for cell proliferation and in vivo for tumor burden, immune composition, cytokine expression, and vascularity.\n\n\nRESULTS\nImmune infiltrates were not altered by these genes. FLG/DST knockout reduced proliferation of human DM93 melanoma in vitro, and decreased B16-F1 tumor burden in vivo. Overexpression of JUP, but not PKP3, in B16-AAD significantly increased tumor burden, increased VEGF-A, reduced IL-33, and enhanced vascularity.\n\n\nCONCLUSIONS\nFLG and DST support melanoma cell growth in vitro and in vivo. Growth effects of JUP were only evident in vivo, and may be mediated, in part, by enhancing angiogenesis. In addition, growth-promoting effects of FLG and DST in vitro suggest that these genes may also support melanoma cell proliferation through angiogenesis-independent pathways. These findings identify FLG, DST, and JUP as novel therapeutic targets whose down-regulation may provide clinical benefit to patients with melanoma.