Project description:Activated SUMOylation is a hallmark of aggressive cancers. Starting from a targeted screening for SUMO-regulated immune evasion mechanisms, we identified an evolutionary conserved function of activated SUMOylation, which attenuates the immunogenicity of tumor cells. Activated SUMOylation allows cancer cells to evade CD8+ T-cell immunosurveillance by repressing the MHC-I antigen processing and presentation machinery (APM). While loss of the MHC-I APM is a frequent cause of resistance to cancer immunotherapies, the pharmacological inhibition of SUMOylation (SUMOi) restored the expression of the MHC-I APM and enhanced the susceptibility of tumor cells to CD8+ T-cell mediated killing. Importantly, SUMOi also triggered the activation of CD8+ T-cells itself and thereby drives a feed-forward loop amplifying the specific anti-tumor immune response. In summary, we show that activated SUMOylation converts tumor cells into a state of immune evasion, and identify SUMOi as rational therapeutic strategy for enhancing the efficacy of cancer immunotherapies.
Project description:Activated SUMOylation is a hallmark of cancer. Starting from a targeted screening for SUMO-regulated immune evasion mechanisms, we identified an evolutionarily conserved function of activated SUMOylation, which attenuated the immunogenicity of tumor cells. Activated SUMOylation allowed cancer cells to evade CD8+ T cell-mediated immunosurveillance by suppressing the MHC class I (MHC-I) antigen-processing and presentation machinery (APM). Loss of the MHC-I APM is a frequent cause of resistance to cancer immunotherapies, and the pharmacological inhibition of SUMOylation (SUMOi) resulted in reduced activity of the transcriptional repressor scaffold attachment factor B (SAFB) and induction of the MHC-I APM. Consequently, SUMOi enhanced the presentation of antigens and the susceptibility of tumor cells to CD8+ T cell-mediated killing. Importantly, SUMOi also triggered the activation of CD8+ T cells and thereby drove a feed-forward loop amplifying the specific antitumor immune response. In summary, we showed that activated SUMOylation allowed tumor cells to evade antitumor immunosurveillance, and we have expanded the understanding of SUMOi as a rational therapeutic strategy for enhancing the efficacy of cancer immunotherapies.
Project description:Melanoma is the deadliest form of skin cancer showing rising incidence over the past years. New insights into the mechanisms of melanoma progression contributed to the development of novel treatment options, such as immunotherapies. However, acquiring resistance to treatment poses a big problem to therapy success. Therefore, understanding the mechanisms underlying resistance could improve therapy efficacy. By conducting transcriptional analysis between SCG2-overexpressing (OE) and control melanoma cells, we detected a downregulation of components of the antigen presenting machinery (APM), which is important for the assembly of the MHC class I complex.
Project description:Loss of MHC class I (MHC-I) antigen presentation in cancer cells can lead to immunotherapy resistance. Using a genome-wide CRISPR/Cas9 screen we identify a critical role for polycomb repressive complex 2 (PRC2) in the coordinated transcriptional silencing of the MHC-I antigen processing pathway (MHC-I APP). This evolutionarily conserved function of PRC2 promotes evasion of T-cell mediated immunity, enabling tumour transmission to non-histocompatible recipients in small cell lung cancer (SCLC) and Tasmanian Devil Facial Tumour. MHC-I APP gene promoters in MHC-I low cancers harbour bivalent activating H3K4me3 and repressive H3K27me3 histone modifications, silencing basal MHC-I expression and restricting cytokine induced MHC-I APP gene upregulation. Bivalent chromatin at MHC-I APP genes is a normal developmental process active in embryonic stem cells and maintained during neural progenitor differentiation. This physiological silencing of MHC-I expression highlights a conserved mechanism by which cancers arising from these primitive tissues coopt PRC2 activity to enable immune evasion.
Project description:Loss of MHC class I (MHC-I) antigen presentation in cancer cells can lead to immunotherapy resistance. Using a genome-wide CRISPR/Cas9 screen we identify a critical role for polycomb repressive complex 2 (PRC2) in the coordinated transcriptional silencing of the MHC-I antigen processing pathway (MHC-I APP). This evolutionarily conserved function of PRC2 promotes evasion of T-cell mediated immunity, enabling tumor transmission to non-histocompatible recipients in small cell lung cancer (SCLC) and Tasmanian Devil Facial Tumor. MHC-I APP gene promoters in MHC-I low cancers harbour bivalent activating H3K4me3 and repressive H3K27me3 histone modifications, silencing basal MHC-I expression and restricting cytokine induced MHC-I APP gene upregulation. Bivalent chromatin at MHC-I APP genes is a normal developmental process active in embryonic stem cells and maintained during neural progenitor differentiation. This physiological silencing of MHC-I expression highlights a conserved mechanism by which cancers arising from these primitive tissues coopt PRC2 activity to enable immune evasion.
Project description:Oligodendrocytes and their progenitors upregulate MHC pathways in response to inflammation, but the frequency of this phenotypic change is unknown and the features of these immune oligodendroglia are poorly defined. We generated MHC class I and II transgenic reporter mice to define their dynamics in response to inflammatory demyelination, providing a means to monitor MHC activation in diverse cell types in living mice and define their roles in aging, injury and disease.
Project description:CD8+ T cells contribute to protective immunity to Mycobacterium tuberculosis (Mtb), but the principles that govern presentation of Mtb peptides on MHC class I (MHC-I) on the surface of infected macrophages for CD8+ T cell recognition are incompletely understood. Here, we use internal standard parallel reaction monitoring (IS-PRM, also known as SureQuant) to rigorously validate identifications of Mtb-derived MHC-I peptides obtained in data-dependent MS analyses. We further use SureQuant to quantify presentation of Mtb peptides derived from the secreted effector proteins EsxA and EsxJ across multiple experimental conditions. We show that presentation of both EsxA- and EsxJ-derived peptides requires the activity of the mycobacterial ESX-1 type VII secretion system, possibly indicating that ESX-1-mediated phagosome membrane damage allows Mtb proteins to access MHC-I antigen processing pathways. We show that this requirement is independent of type I interferon signaling that occurs downstream of phagosome damage. Treatment with inhibitors of conventional proteolytic pathways involved in MHC-I antigen processing inhibits presentation of self peptides as expected, but does not inhibit presentation of Mtb peptides, implying an alternative or redundant mechanism of processing.