Oral Presentation 9th Australasian Vaccines & Immunotherapeutics Development Meeting 2022

Overexpression of memory associated transcription factors promotes chimeric antigen receptor (CAR) T cell stemness and anti-tumour efficacy (#24)

Jack D Chan 1 2 , Junyun Lai 1 2 , Clare Y Slaney 1 2 , Paul A Beavis 1 2 , Phil K Darcy 1 2 3 4
  1. Peter MacCallum Cancer Centre, 3056, VIC, Australia
  2. Sir Peter MacCallum Department of Oncology, University of Melbourne, Melbourne, Victoria, Australia
  3. Department of Pathology, University of Melbourne, Melbourne, Victoria, Australia
  4. Department of Immunology, Monash University, Clayton, Victoria, Australia

Chimeric antigen receptor (CAR) T cell therapy is a specialised immunotherapy that involves the genetic engineering of autologous patient T cells to target defined cancer antigens. CAR T cells are effective against some haematological cancers but challenges remain for the treatment of solid tumours due to CAR T cell exhaustion and immunosuppression. Clinical data indicates that less differentiated CAR T cells have improved persistence and therapeutic efficacy. These cells have unique transcriptional profiles regulated by numerous pro-memory transcription factors (TFs). However, the relative contribution of each TF to the desired CAR T cell phenotype is not fully understood. In this study, the capability of several TFs to promote CAR T cell persistence and anti-tumour efficacy were investigated. Retroviral vectors were generated to transduce human epidermal growth factor receptor 2 (HER2) directed CAR T cells overexpressing pro-memory TFs and CAR T cell function was assessed through in vitro tumour co-culture assays and in vivo utilising syngeneic mouse tumour models. CAR T cells overexpressing TFs exhibited improved stem-like phenotypes relative to control CAR T cells in vitro. TF overexpression enhanced CAR T cell polyfunctionality through improved inflammatory cytokine production and survival. In mice, adoptively transferred TF-overexpressing CAR T cells significantly inhibited the growth of orthotopic HER2+ breast tumours relative to control CAR T cells. Analysis of TF-overexpressing CAR T cells revealed improved persistence, reduced exhaustion and increased cytotoxicity. Our study suggests that overexpression of pro-memory TFs can enhance CAR T cell stemness and multipotency, leading to improved persistence without impeding their polyfunctionality and cytotoxicity against tumours in vivo. Therefore, overexpression of pro-memory TFs in CAR T cells may represent a promising strategy to overcome the hurdle of limited CAR T cell persistence, particularly within the clinical setting of solid cancers, and to improve long-term treatment outcomes in patients.