Yoav Chemla, Orit Itzhaki, Stav Melamed, Chen Weller, Yuval Sade, Paulee Manich, Keren Reshef, Nicolas Xenidis, Avishai Maliah, Gilad Levy, Roma Parikh, Osnat Bartok, Opal Levy, Ilana Tal, Gal Aziel, Abraham Nissani, Sharon Yunger, Daniela Likonen, Vitaly Kliminsky, Tamar Golan, Coralie Capron, Valentina Ace, Ronen Levy, Diana Rasoulouniriana, Zohar Eyal, Yuval Barzilay, R. S. Balaban, Aseel Khateeb, Rami Khosravi, Amir Grau, Tamar Ziv, Polina Greenberg, Dvir Netanely, Hilla Vaknin, Xunwei Wu, Yael Amitay, Ronen Brenner, Julia María Martínez Gómez, Dov Hershkovitz, Tal Yardeni, Valentina Zemser‐Werner, Oren Kobiler, Yael Friedmann, David Bassan, Ron Shamir, Lea Eisenbach, Nadine Santana-Magal, Michael Milyavsky, Galit Eisenberg, Leeat Keren, Merav Cohen, Dvir Gur, Boaz Barak, Michal Lotem, David Sprinzak, Shoshana Greenberger, David E. Fisher, Michal J. Besser, Mehdi Khaled, Pierre Close, Ronnie Shapira, Sébastien Apcher, Asaf Madi, Mitchell P. Levesque, Francesca Rapino, Yaron Carmi, Shivang Parikh, Yardena Samuels, Carmit Levy
While melanoma cells often express a high burden of mutated proteins, the infiltration of reactive T cells rarely results in tumor-eradicating immunity. We discovered that large extracellular vesicles, known as melanosomes, secreted by melanoma cells are decorated with major histocompatibility complex (MHC) molecules that stimulate CD8 + T cells through their T cell receptor (TCR), causing T cell dysfunction and apoptosis. Immunopeptidomic and T cell receptor sequencing (TCR-seq) analyses revealed that these melanosomes carry MHC-bound tumor-associated antigens with higher affinity and immunogenicity, which compete with their tumor cell of origin for direct TCR-MHC interactions. Analysis of biopsies from melanoma patients confirmed that melanosomes trap infiltrating lymphocytes, induce partial activation, and decrease CD8 + T cell cytotoxicity. Inhibition of melanosome secretion in vivo significantly reduced tumor immune evasion. These findings suggest that MHC export protects melanoma from the cytotoxic effects of T cells. Our study highlights a novel immune evasion mechanism and proposes a therapeutic avenue to enhance tumor immunity.