Reprogramming tumour infiltrating Foxp3+ regulatory T cells into immune effectors using cell permeable Runx antagonists

Nature of proposed research: Tumour infiltrating regulatory T cells prevent the immune system attacking cancer cells. We propose to change the function of regulatory T cells by using novel factors that control regulatory T cells. The goal is to improve the effectiveness of immunotherapy in cancer treatments.

The prospective outcomes: Recent work in the host laboratory has identified factors that control regulatory T cells. The host laboratory has made and tested novel factors that we hope will allow tumour associated Treg cells to become immune effector cells which will attack cancer cells in patients.

The expected benefits in improving human health: Reprogramming the function of regulatory T cells has the potential to greatly improve the effectiveness of existing cancer vaccines and immunotherapy treatments for cancer.

Aims

To develop cell permeable Runt proteins that enter and reprogram T regulatory (Treg) cells, to characterise the resulting Foxp3low 'exTreg' cells and to assess their anti tumour potential.

Objectives

To construct novel cell permeable Runt domains.
To characterise and evaluate the ability of cell permeable Runt domains to reprogram normal and tumour associated Treg cells into immune effector cells.

Design

Treg cells are important in cancer because they restrict tumour immune responses and are associated with an adverse prognosis in ovarian, breast and renal carcinoma. The transcription factor Foxp3 controls the development and function of Treg cells. Recent work within the host laboratory has shown that Runx proteins maintain the expression of Foxp3 in mouse Treg cells and that Foxp3 expression is downregulated by retroviral expression of dominant negative versions of Runx (Runt).

Since Foxp3 expression maintains the regulatory functions in Treg cells, Runt expression may reprogram Treg cells into immune effectors that can target cancer cells in vitro and in vivo. In contrast to strategies based on depleting Treg cells, reprogramming Treg cells using cell permeable Runt domains, offers the potential for harnessing their unique T cell receptor specificities for anti tumour responses.

Methodology

Cell permeable Runt domains will be constructed using recombinant protein techniques. This will include ligation of the Runt domain to a suitable protein transduction domain and tagging to facilitate purification and visualisation in transduced cells. We will then reprogram mouse Treg cells using cell permeable Runt proteins and characterise gene expression, lymphokine production and regulatory activity of Foxp3low 'exTreg' cells both in vitro and in mouse tumour models. If protein transfer is less efficient than retroviral gene transfer, then we will re-engineer the transduction domain to increase intracellular protein concentrations and the Runt domain itself to increase DNA binding and protein stability. If Foxp3 expression can be successfully extinguished using cell permeable Runt domains and the resulting exTreg cells become immune effectors, then the approach will be extended to normal and tumour associated human Treg cells.

Scientific and Medical Opportunities

Reprogramming the function of regulatory T cells has the potential to greatly improve the effectiveness of existing cancer vaccines and immunotherapy treatments for cancer.