A Quantitative Imaging-based Biomarker for Assessment of Therapy Response in Soft Tissue Sarcomas by Differential Volume Estimation of Viable and Non-viable Tumor Fractions
In this proposal we will take advantage of immunocompetent sarcoma models we have recently developed using electroporation-based delivery of transposon vectors to the muscle. We will concentrate on two of the models we have characterized and represent sarcomas with varying degree of immune cell infiltration: synovial sarcoma (SS, SS18-SSX1-driven) with low immune cell infiltration, and undifferentiated pleomorphic sarcoma (UPS, driven by KRASG12V and p53 loss) with higher immune cell infiltration. We will use CD276 (B7-H3) as a prototype pan-cancer antigen that can serve as CAR-T cell target across different sarcoma models. We will first characterize the sarcoma tumor microenvironment in these models with and without CAR-T cell treatment, and identify the CAR-T baseline activity that can be achieved in these contexts. In a second aim we will apply loss of function CRISPR/Cas9 screens in CAR-T cells in vivo to identify candidate genes that improve T cell infiltration and activity in immunocompetent hosts. To this end tumor-bearing mice will be treated with a library pool of CAR-T cells and sgRNAs present in tumor-enriched CAR-T cell populations will be identified by next generation sequencing. High confidence candidates can then be validated in mouse and human models such as patient-derived xenografts. The results of this project will potentially lay the experimental basis to refine cell-based immunotherapies for sarcoma and other solid tumors, providing a much needed preclinical rational to develop new and innovative clinical cancer treatment trials in the future.