Project description:Cancer-specific coding mutations can create neoantigens that can be presented on the cell surface of tumors to trigger immunogenic clearance1–4. However, current cancer vaccine approaches have not been universally effective5; this is especially true in tumors with a low mutational burden which, in turn, carry a low conventional neoantigen load6. Transposable elements (TEs) make up approximately 50% of the human genome and have been discovered to provide cryptic promoters, which can be reactivated with epigenetic manipulations to generate TE-gene chimeric transcripts that can be translated into noncanonical peptides7. Here, we focus on glioblastoma, an aggressive brain cancer with low mutation burden, to explore whether epigenetic therapy can induce TE-chimeric antigens (TEAs) to appreciably increase the antigen repertoire that can be targeted with immunotherapy. We perform comprehensive epigenetic and transcriptomic profiling of three patient-derived glioblastoma stem cell lines (GSCs) and, more importantly, astrocyte and fibroblast primary cell lines that are either proliferating or quiescent, treated with epigenetic therapy drugs to identify treatment-induced TEA (TI-TEA) candidates that are preferentially expressed in cancer cells. Although we verify TI-TEAs are indeed presented on HLA molecules in GSCs thus are promising cancer vaccine candidates, many TEs were also transcriptionally activated in proliferating primary cell lines after epigenetic therapy. This work presents a cautionary but optimistic tale for future efforts in harnessing TI-TEAs for targeted immunotherapy approaches.
Project description:Chromatin accessibility discriminates stem from mature cell populations, enabling the identification of primitive stem-like cells in primary tumors, such as Glioblastoma (GBM) where self-renewing cells driving cancer progression and recurrence are prime targets for therapeutic intervention. We show, using single-cell chromatin accessibility, that primary GBMs harbor a heterogeneous self-renewing population whose diversity is captured in patient-derived glioblastoma stem cells (GSCs). In depth characterization of chromatin accessibility in GSCs identifies three GSC states: Reactive, Constructive, and Invasive, each governed by uniquely essential transcription factors and present within GBMs in varying proportions. Orthotopic xenografts reveal that GSC states associate with survival, and identify an invasive GSC signature predictive of low patient survival. Our chromatin-driven characterization of GSC states improves prognostic precision and identifies dependencies to guide combination therapies.
Project description:We over-expressed an epigenetic regulator in a glioblastoma (GBM) primary culture from an adult patient. These GBM cells have cancer stem cell phenotypes, as they have self-renewal properties and tumor initiation potential when transplanted in immunocompromised mice. ATAC-seq was performed on cells over-expressing the epigenetic regulator and control cells expressing EGFP. ATAC-Seq on glioblastoma cells that over-express EGFP or an epigenetic regulator.
Project description:Glioblastoma is one of the most malignant brain tumors with poor prognosis and their development and progression are known to be driven by glioblastoma stem cells. Although glioblastoma stem cells lose their cancer stemness properties during cultivation in serum-containing medium, little is known about the molecular mechanisms regulating signaling alteration in relation to reduction of stemness. In order to elucidate the global phosphorylation-related signaling events, we performed a SILAC-based quantitative phosphoproteome analysis of serum-induced dynamics in glioblastoma stem cells established from the tumor tissues of the patient. Among a total of 2,876 phosphorylation sites on 1,584 proteins identified in our analysis, 732 phosphorylation sites on 419 proteins were regulated through the alteration of stem cell characteristics.