Hypoxic Melanoma Cells Deliver microRNAs to Dendritic Cells and Cytotoxic T Lymphocytes through Connexin-43 Channels

Abstract

Alterations in microRNA (miRNA) profiles, induced by tumor microenvironment stressors, like hypoxia, allow cancer cells to acquire immune-resistance phenotypes. Indeed, hypoxia-induced miRNAs have been implicated in cancer progression through numerous cancer cell non-autonomous mechanisms, including the direct transfer of hypoxia-responsive miRNA from cancer to immune cells via extracellular vesicles. Connexin-43 (Cx43)-constituted gap junctions (GJs) have also been involved in miRNA intercellular mobilization, in other biological processes. In this report, we aimed to evaluate the involvement of Cx43-GJs in the shift of miRNAs induced by hypoxia, from hypoxic melanoma cells to dendritic cells and melanoma-specific cytotoxic T lymphocytes (CTLs). Using qRT-PCR arrays, we identified that miR-192-5p was strongly induced in hypoxic melanoma cells. Immune cells acquired this miRNA after co-culture with hypoxic melanoma cells. The transfer of miR-192-5p was inhibited when hypoxic melanoma cells expressed a dominant negative Cx43 mutant or when Cx43 expression was silenced using specific short-hairpin RNAs. Interestingly, miR-192-5p levels on CTLs after co-culture with hypoxic melanoma cells were inversely correlated with the cytotoxic activity of T cells and with ZEB2 mRNA expression, a validated immune-related target of miR-192-5p, which is also observed in vivo. Altogether, our data suggest that hypoxic melanoma cells may suppress CTLs cytotoxic activity by transferring hypoxia-induced miR-192-5p through a Cx43-GJs driven mechanism, constituting a resistance strategy for immunological tumor escape.

Anti-Tumor Effect of IDF-11774, an Inhibitor of Hypoxia-Inducible Factor-1, on Melanoma

“…In contrast, tumor cell proliferation can be inhibited by anti-tumor effect of CD8-positive T cells and their activities (Mahmoud et al, 2017;Pio et al, 2019). The role of hypoxia in immune escape has been identified (Barsoum et al, 2014;Li et al, 2018;Zou et al, 2018;Liu and Curran, 2020;Tittarelli et al, 2020;Van Duijn et al, 2022). For metastasis, melanoma needs to adapt to microenvironmental changes.…”

miRNA as a Modulator of Immunotherapy and Immune Response in Melanoma

“…Additionally, miR-9 overexpression in DCs reduced tumor progression in a melanoma mouse model. miR-192-5p- and miR-148a-3p-derived hypoxic melanoma cells were transferred into DCs by the Cx43 channel and miR-192-5p was delivered to both DCs and T cells to inhibit their functions [ 85 ].…”

“…A previous study demonstrated that miR-498 and miR-3187-3p in melanoma-derived exosomes reduces the functions of CD8+ T cells by targeting IFN-α and protein tyrosine phosphatase receptor type C (PTPRC), the coding gene for CD45, respectively [ 105 ]. Hypoxic melanoma cells deliver miR-192-5p to cytotoxic T cells via Connexin-43 (Cx43)-constituted gap junctions to reduce the T cell functioning [ 85 ].…”

Connexins in melanoma: Potential role of Cx46 in its aggressiveness

“…Melanoma cells can form GJCs with themselves and with fibroblasts, but do not with keratinocytes (Hsu et al, 2000), supporting the idea that Cx deregulation has a huge impact on the homeostatic control that keratinocytes exert over melanocytes. Moreover, melanoma cells establish GJIC with immune cells, such as natural killer (NK) cells, T cells, and dendritic cells (DCs), indicating that the immune system also controls melanoma progression by Cx-mediated mechanisms (Saccheri et al, 2010;Tittarelli et al, 2014;Gleisner et al, 2017;Hofmann et al, 2019;Tittarelli et al, 2020;Navarrete et al, 2020). Several proteins that allow cellto-cell communication have been described as key factors in tumor cell transformation.…”