PROJECT 3: Tools for Capturing Immune Cell/Cancer Cell Interactions in Cancer Immunotherapies and Combination Immunotherapies. ABSTRACT: Cancer Immunotherapy was Science Breakthrough of the Year 2013[1], with tremendous promise and excitement surrounding two immunotherapy classes. Class 1 is comprised of immune checkpoint inhibitors[2, 3], such as for Programmed Death (PD)-1/L1 blockade. These drugs can increase the susceptibility of cancer cells to immune system attack. The clinical testing of PD-1/L1 blockade in multiple cancers, but led by work in melanoma[4], has demonstrated a new era in cancer treatment[5, 6]. Therapy Class 2 is Adoptive Cell Transfer (ACT)[7, 8], which seeks to strengthen the anti-tumor immune system function. Technologies to support these cancer immunotherapies have been an NSBCC theme [9-13], and our immune monitoring tools are used in several trials and patient studies. Recent immunotherapy successes have raised patient expectations. We propose technologies to advance the science to bring this promise to more patients. We will interrogate how tumor models and patients with cancer respond or become resistant to single and combination immunotherapies, with anticipated implications for all cancer patients receiving immunotherapies. We focus on measuring, in vivo and in vitro, the interactions between the cancer cells and tumor infiltrating lymphocytes (TILs). Such interactions can yield tumor cell killing, but can also promote the activation of tumor cell resistance to such killing. This theme is central for improving both ACT and checkpoint inhibitor therapies.