Regulation of gap junctions in melanoma and their impact on Melan-A/MART-1-specific CD8 super(+) T lymphocyte emergence

Gap junctions (GJs) enable intercellular communication between adjacent cells through channels of connexins. Using a three-dimensional construct, we previously showed that endothelial and tumor cells formed GJs, allowing melanoma-specific T lymphocytes to recognize and kill melanoma-derived endothelial cells. We demonstrate here on histological sections of melanoma biopsies that GJ formation occurs in vivo between tumor and endothelial cells and between T lymphocytes and target cells. We also show an in vitro increase of GJ formation in melanoma and endothelial cells following dacarbazin and interferon gamma (IFN- gamma ) treatment or hypoxic stress induction. Our data indicate that although connexin 43 (Cx43), the main GJ protein of the immune system, was localized at the immunological synapse between T lymphocyte and autologous melanoma cells, its over-expression or inhibition of GJs does not interfere with cytotoxic T lymphocyte (CTL) clone lytic function. In contrast, we showed that inhibition of GJs by oleamide during stimulation of resting PBMCs with Melan-A natural and analog peptides resulted in a decrease in antigen (Ag) specific CD8 super(+) T lymphocyte induction. These Ag-specific CD8 super(+) cells displayed paradoxically stronger reactivity as revealed by CD107a degranulation and IFN- gamma secretion. These findings indicate that Cx43 does not affect lytic function of differentiated CTL, but reveal a major role for GJs in the regulation of antigen CD8 super(+)-naive T lymphocyte activation. Key message: GJ formation occurs in vivo between T lymphocytes and tumor cellsCx43 localized at the immunological synapse between T and autologous melanoma cellsInhibition of GJs resulted in a decrease in Ag-specific CD8 super(+) T lymphocyte inductionA role for GJs in the regulation of antigen CD8 super(+)-naive T lymphocyte activation