Engineered T cells for improved migration into solid tumor sites

Adoptive transfer T cell-based immunotherapies and checkpoint inhibitor immunotherapy have shown significant promise in the treatment of cancers. However, checkpoint inhibitor therapy still fails in a majority of patients and chimeric antigen receptor (CAR)-T cells are ineffective against most solid tumors. In large part, these failures are due to the fact that frequently tumors are mostly devoid of T cells or that T cells are present only in the tumor-surrounding stroma but largely excluded from the tumor mass. Tumors are often surrounded by extensive collagen-rich extracellular matrix (ECM) structures, which impede the entry of T cells into the tumor mass. T cell paucity or exclusion from the tumor site correlate with poor prognosis, limited efficacy of checkpoint inhibitor immunotherapies, and ineffectiveness of CAR-T cell therapy against solid tumors. Most cellular tumor immunotherapy approaches to date have focused on reversing T cell exhaustion and increasing persistence of tumor-specific T cells and CAR-T cells. However, these approaches generally do not solve the issue of recruitment and infiltration of therapeutic T cells into the tumor. The overall goal of this proposal is to engineer T cells to enhance their migration into tumors to increase their anti-tumor activity in ‘cold’ tumors and tumors that exclude T cells from the tumor mass. Our exploratory R21 proposal specifically addresses the unmet need to improve migration of T cells into tumors by creating T cells with increased capacity to migrate through restrictive environments. We have found that Formin-like-1 (FMNL1) promotes efficient T cell extravasation, motility through confined environments, and interstitial migration in vivo. Furthermore, our preliminary data using a melanoma model show that overexpression of FMNL1 significantly increases the number of tumor-specific T cells present at the tumor site. Thus, we hypothesize that T cells engineered to overexpress FMNL1, or its active mutants, will have increased trafficking to the tumor site, deeper infiltration into the tumor mass, and enhanced anti-tumor activity. We will test our hypothesis with the following Aims: Aim 1. Determine if overexpression of FMNL1 or its active mutants enhances tumor-specific T cell migration and accumulation within tumors. Aim 2. Determine if T cells engineered to overexpress FMNL1 have increased anti-tumor activity and improve the efficacy of checkpoint inhibitor therapy. Overall, we will establish and validate a platform for T cell bioengineering to improve T cell migration into tumor sites that can be applied to tumor-infiltrating lymphocyte (TIL) transfer therapy and CAR-T cell therapy for solid tumors. Our novel approach can both improve the ability of T cells to extravasate at the tumor site, and enhance the capacity of T cells to migrate through restrictive tissue barriers to infiltrate the tumor mass. From a future translational standpoint, an additional advantage of this system is that the T cell infiltration enhancement provided by FMNL1 is not limited to a particular tumor antigen and is not MHC restricted. Overall, our work has the potential to significantly improve the treatment of solid tumors using adoptive T cell transfer therapies.