Targeting tumor endothelial cells for cancer immunotherapy with cytokines

A plethora of immuno-therapy strategies have been transforming the practice of clinical oncology in recent years, however, only a minority of patients with solid tumors stand to benefit. One major reason for the high failure rate of immuno-therapy is the paucity or complete absence of infiltrating T cells in many tumors. Strategies to enhance T cell trafficking to tumors may therefore boost efficacy of immuno- therapies. A key step in T cell recruitment to tissues is the intravascular adhesion to specialized endothelial cells (ECs) that must present a combination of prerequisite traffic signals to blood-borne T cells. In particular, ECs that line high endothelial venules (HEVs) are singularly efficient at recruiting circulating lymphocytes. HEVs are usually found only in lymph nodes and Peyer's patches but they can also arise at sites of chronic inflammation to enable lymphocyte infiltration and the formation of tertiary lymphoid tissues. Importantly, the inflamed environment in some solid tumors occasionally results in formation of intratumoral HEVs, a phenomenon that has been shown to substantially improve the success of immuno-therapy. However, HEVs are rare or absent in most tumors, a fact that is likely a major contributing factor in the clinical preponderance of 'cold' tumors. Here, we propose to develop a targeted cytokine, PLIg, to selectively convert poorly adhesive solid tumor microvessels into HEVs. PLIg will consist of a nanobody against a newly identified tumor EC-restricted surface antigen, and a cytokine linked to IgG Fc. Preliminary results suggest that the endothelial targeting component enables rapid and selective binding and accumulation of circulating fusion protein on tumor ECs, thereby 'gluing' the cytokine to the EC surface. We will ask whether administration of PLIg to tumor-bearing mice can boost intra-tumoral HEV formation to amplify T cell recruitment and thereby enhance the efficacy of cancer immuno-therapy.

Criteria to determine whether the specific aims have been achieved:

1. Demonstrate specific binding of PLIg to its endothelial target and induction of HEV differentiation in vitro.

2. Show that PLIg promotes HEV formation in tumors, as evaluated by IHC, FACS and RNAseq.

3. Document that PLIg therapy promotes T cell recruitment into murine tumors to counteract tumor progression and enhance host survival, either as a single agent or in combination with immunotherapy.