Tumor- and Neoantigen-Reactive T-cell Receptors Can Be Identified Based on Their Frequency in Fresh Tumor

Anna Pasetto, Alena Gros, Paul F Robbins, Drew C Deniger, Todd D Prickett, Rodrigo Matus-Nicodemos, Daniel C Douek, Bryan Howie, Harlan Robins, Maria R Parkhurst, Jared Gartner, Katarzyna Trebska-McGowan, Jessica S Crystal, Steven A Rosenberg

Adoptive transfer of T cells with engineered T-cell receptor (TCR) genes that target tumor-specific antigens can mediate cancer regression. Accumulating evidence suggests that the clinical success of many immunotherapies is mediated by T-cells targeting mutated neoantigens unique to the patient. We hypothesized that the most frequent TCR clonotypes infiltrating the tumor were reactive against tumor antigens. To test this, we developed a multi-step strategy that involved TCRB deep sequencing of the CD8+PD-1+ T-cell subset, matching of TCRA-TCRB pairs by pairSEQ and single cell RT-PCR, followed by testing of the TCRs for tumor-antigen specificity. Analysis of 12 fresh metastatic melanomas revealed that in 11 samples, up to 5 tumor-reactive TCRs were present in the 5 most frequently occurring clonotypes, which included reactivity against neoantigens. These data demonstrate the feasibility of developing a rapid, personalized, TCR-gene therapy approach that targets the unique set of antigens presented by the autologous tumor without the need to identify their immunologic reactivity.