Choosing the right T cell for CAR therapy approaches

Supervisors: A/Prof Andreas Behren, A/Prof Paul Beavis (PMCC), Dr Fern Koay (PDI)

Laboratories: Tumour Immunology Laboratory

Chimeric Antigen Receptor (CAR) T cells have shown clinical success in hematological cancers with multiple therapies approved around the world. However, no similar success can be reported for the treatment of human solid tumours. Multiple strategies have been suggested to overcome the issues related to treatment failure in this setting including poor T cell infiltration and a suppressive tumour microenvironment (TME) affecting CAR T cell efficacy.

T cell subset heterogeneity has been characterized in depth over the last decade, however direct head-to-head comparisons between vastly distinct classes of T cells and their utility for CAR T cell approaches have not been performed. Critically, beyond CD4 and CD8 classical T cells, non-conventional T cell subsets such as MAIT and gd T cells have higher organ-homing capacity and migrate preferentially to nonlymphoid tissue, where they can react rapidly to stimulus. Here, we hypothesise that MAIT cells and gd T cells may have several advantages over conventional T cells including their potential to be utilized in a third-party manner when generated from healthy donors and their increased cytotoxic capacity relative to conventional CD4 and CD8 T cells. Thus, we aim to holistically explore these T cell subsets and their propensity to act as CAR T cell therapeutics in the setting of solid tumours.

For this we will generate CD4, CD8, MAIT and gd T cell subsets expressing CARs of the same specificity and test their ability in parallel for in vitro cytotoxicity and cytokine secretion against tumour cells utilizing 2D and 3D cell culture models .We will identify the best layout of CAR constructs for armoured CAR approaches (activation domains and cytokine secretion) for the various T cell subsets and compare their in vivo ability to infiltrate and target solid tumours in mouse models. Within in vivo experiments, we will also exploit the amenability of unconventional CAR T cells as they can be selectively activated and expanded with TCR agonists such as antigens to enhance cell numbers or overall therapy persistence. In addition, we will utilize CRISPR-Cas9 technology to specifically override candidate molecules contributing to the immune-suppressive state of our generated CAR T cells (e.g. PD-1KO T cells) via approaches that have already been optimized within the host laboratories (Ref Giuffrida et al. 2021, Nature Communications).

The project will take place across 3 of Melbourne’s leading cancer and immunology institutes (PeterMac/PDI/ONJCRI) with lab rotations amongst these, leveraging the developed methodologies and expertise in these laboratories in unconventional T cell biology, cancer immunology, and CAR T cell development.