Targeting the tumor microenvironment with engineered CD4+ T cells

Abstract Novel immune therapies are needed to help the majority of patients with melanoma and other solid tumors who fail to benefit or stop responding to immune checkpoint inhibitors, and adoptive transfer of tumor specific T cells is one method that con overcome resistance to other immune therapies. Most research has focused on

engineering CD8 T cells that directly target and kill cancer cells, but this proposal will focus on the “helper” CD4 T cells that work by orchestrating the function of other immune cells. The goal of this proposal is to develop a therapeutic strategy using CD4 T cells to overcome treatment resistance in solid tumors.

Correlative studies from patients with cancer show that having greater numbers of tumor specific CD4 T cells are associated with activation of other immune cells in tumors and better outcomes. Work in mouse cancer models show that CD4 T cells can work through support of CD8 T cells and through innate immune cell killing

of tumors even when other T cells are not present. The most effective CD4 therapies in the mouse cancer models have combined CD4 T cells with other signals that activate innate immune cells in tumors, but these signals are toxic when given throughout the whole body. We have found that two potent innate immune

signals, IL-12 and IL-18 can be engineered into CD4 T cells that can target these signals specifically to tumors. We find that CD4 T cells engineered in this way can destroy tumors, activate CD8 T cells, and activate immune cells in mouse cancer models. In our first aim we will identify which molecules made by T cells are important in

this process, which immune cells in tumors are the targets, and which immune cells are responsible for tumor cell death. Use of this approach in patients with melanoma will require ways to produce large populations of CD4 T cells that are specific to the patients’ cancer, and we will obtain these cells from surgically removed tumors from

patients. Existing methods to grow tumor specific T cells from tumors have had some benefit, but the CD4 T cells are mostly lost during the standard process. We have identified a way to identify the tumor specific CD4 T cells within a tumor and will use this information to isolate these cells away from other T cells so that we can

grow them. In our second aim we will develop a reliable process to isolate and expand these cells that maintains their function, as well as engineer them with human versions of the IL-12 and IL-18 signals we explored in mice. We will then use a humanized mouse model to test whether CD4 T cells grown from human

tumors can effectively target human tumor and immune cells. The goal of this work is to develop a new type of treatment for cancer using CD4 T cells engineered with innate immune signals that can be used in clinical trials of patients with treatment resistant melanoma and other solid tumors.