Poster Presentation Asia-Pacific Vaccine and Immunotherapy Congress 2023

Harnessing the Stress Response for Immunity in Acute Myeloid Leukaemia  (#176)

Basit Salik 1 2 , Carol Lee 1 , Jasmin Straube 1 , Steven Lane 1 2 , Kyohei Nakamura 1
  1. Cancer Program, QIMR Berghofer Medical Research Institute, Brisbane, QLD, Australia
  2. School of Medicine, University of Queensland, Brisbane, QLD, Australia

Acute Myeloid Leukaemia (AML) is an aggressive cancer of the blood notoriously difficult to treat with dismal 5-year survival outcomes at <30%. The curative potential of the allogeneic transplant to control AML progression through the graft-versus-leukaemia (GVL) effect is well-recognized and highlights the importance of immune-mediated control in AML. However, the importance of natural immune surveillance against AML remains to be fully characterized. Cancer cells including leukaemia can adapt to oncogenic/environmental stress through a process called the integrated stress response (ISR). Using a murine model of a poor prognosis AML subset driven by the t(9;11)(p22;q23) translocation (MLL-AF9 hereafter referred to as MA9), we have identified GADD34 as a key component of the ISR protecting AML from anti-tumour immunity. MA9 AML represents a poorly immunogenic and an aggressive AML patient group. Strikingly, while both control and GADD34-/- MA9 AML progressively grew in immunodeficient hosts (Rag2-/-Il2r-/- mice), GADD34-/- MA9 AML, but not control MA9 was effectively controlled in immunocompetent wild type or natural killer (NK) cell-competent hosts (Rag2-/- mice). Similarly, antibody-mediated depletion of NK and CD8+ T cells exacerbated GADD34-/- AML development but mice with intact immunity remained tumour free. To gain further mechanistic insight, we performed RNA-sequencing on enriched leukemic hematopoietic stem and progenitor cells (HSPCs). Gene set enrichment analyses showed GADD34-/- AML is metabolically distinct, and this metabolic reprogramming was also evident in the proteome and metabolome profile. Our ex-vivo data suggest that GADD34-mediated modulation of the ISR drives metabolic regulation that critically contributes to cellular redox control where elevated intracellular reactive oxygen species were observed in both GADD34-deficient murine and human AML model systems. Indeed, ROS accumulation potentiates the apoptotic cascade and immune-derived cytokines are potent inducers of ROS. In this light, GADD34 deficient murine and human AML cells were susceptible to immune-mediated toxicity either by T-cell conditioned medium or by co-culture with NK cells. Our data establish a novel link between tumour ISR and anti-tumour immunity and suggest that targeting this pathway may sensitize AML to cancer immunotherapy.