mart-1-antigen and Hypoxia

We have previously reported a model for melanoma progression in which oscillation between melanoma cell phenotypes characterized by invasion or proliferation is fundamental to tumor heterogeneity and disease progression. In this study we examine the possible role of hypoxia as one of the microenvironmental influences driving metastatic progression by promoting a switch from a proliferative to an invasive phenotype. Immunohistochemistry on primary human cutaneous melanoma biopsies showed intratumoral heterogeneity for cells expressing melanocytic markers, and a loss of these markers correlated with hypoxic regions. Furthermore, we show that the downregulation of melanocytic markers is dependent on hypoxia inducible factor 1α (HIF1α), a known regulator of the hypoxic response. In vitro invasion assays showed that a hypoxic environment increases the invasiveness of proliferative melanoma cell cultures in a HIF1α-dependent manner. In contrast, invasive phenotype melanoma cells showed no increase in invasive potential upon exposure to hypoxia. Thus, exposure of proliferative melanoma cells to hypoxic microenvironments is sufficient, in a HIF1α-dependent manner, to downregulate melanocytic marker expression and increase their invasive potential.

Topics: Biomarkers, Tumor; Cell Proliferation; Disease Progression; Gene Expression Regulation, Neoplastic; Genetic Heterogeneity; Humans; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; MART-1 Antigen; Melanoma; Neoplasm Invasiveness; Phenotype; Skin Neoplasms; Tumor Cells, Cultured; Tumor Microenvironment

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-γ) 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(+) T lymphocyte induction. These Ag-specific CD8(+) cells displayed paradoxically stronger reactivity as revealed by CD107a degranulation and IFN-γ 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(+)-naïve T lymphocyte activation.. GJ formation occurs in vivo between T lymphocytes and tumor cells Cx43 localized at the immunological synapse between T and autologous melanoma cells Inhibition of GJs resulted in a decrease in Ag-specific CD8(+) T lymphocyte induction A role for GJs in the regulation of antigen CD8(+)-naïve T lymphocyte activation.

Topics: Antineoplastic Agents, Alkylating; Apoptosis; CD8-Positive T-Lymphocytes; Cell Line, Tumor; Connexin 43; Cytotoxicity, Immunologic; Dacarbazine; Gap Junctions; Gene Expression; Humans; Hypoxia; Immunological Synapses; Interferon-gamma; MART-1 Antigen; Melanoma; Oxidative Stress; Protein Transport; T-Lymphocytes, Cytotoxic