To determine where in the tumor expanding T-cells are located, we successfully implemented spatial single-cell methods. Recently, we published a single-cell study investigating the mechanisms distinguishing anti-PD-L1+ anti-CTLA4 combination therapy from anti-PD-L1 monotherapy in head and neck squamous cell carcinoma (HNSCC) (Franken et al., Immunity, 2024). Through comprehensive single-cell and spatial analyses of the TME, as well as single-cell profiling of peripheral blood mononuclear cells (PBMCs), we identifed CD4+ T-cell activation as a hallmark of early response to anti-PD-L1 plus anti-CTLA4 in HNSCC.
To identify the tumor antigens to which expanding T-cells react to, we developed a novel high-throughput method, Transcriptome-WIde Screening for T-cell Antigen Research (TWISTAR). TWISTAR successfully identifies tumor antigens, making it a unique platform to identify tumor antigens for the generation of individualized cancer vaccines. Key strengths of TWISTAR include: i) it was developed using on-treatment biopsies collected during ICB, thereby focusing on expanding TCRs likely to be tumor-reactive (and not bystanders), ii) it is a TCR-driven approach, based on TCRs detected in patient tumors, iii) the tumor transcriptome is presented in a tailored human cell line, closely resembles the patient’s antigen representation, and iv) TWISTAR is not limited to tumor mutations, it detects everything embedded in the transcriptome including splicing events and non-coding sequences (which we refer to as ‘dark antigens’).
To explore other tumor antigen sources beyound somatic mutations, we identified several cancer-specific alternative splicing events linked to tumor antigenicity, antitumor immune activity, and ICB response in breast and other cancers.
To enable non-invasive detection of T-cell expansion, we demonstrated that TCR sharing between tumor and blood serves as a marker for response to ICB in hepatocellular carcinoma (HCC) patients (Cappuyns et al., Nature Communications, 2023).
