W183 - Flow Cytometry-based High Throughput Assay Uncovers a TNFα-JAK1-ICAM-1 Cytotoxic Axis Utilized by Double Negative T Cells Against Acute Myeloid Leukemia

Jong Bok Lee – Toronto General Hospital Research Institute – University Health Network; Ismat Khatri – Toronto General Hospital Research Institute – University Health Network; Yoosu Na – Toronto General Hospital Research Institute – University Health Network; Mark Minden – Princess Margaret Cancer Centre – University Health Network; Li Zhang – Toronto General Hospital Research Institute – University Health Network

Abstract Text: Acute myeloid leukemia (AML) remains a challenging disease with high relapse rates and treatment-associated toxicities following induction chemotherapy and allogeneic hematopoietic stem cell transplantation (allo-HSCT). Ex vivo expanded allogeneic CD3+CD4-CD8- double negative T cells (DNTs) from healthy donors effectively target primary and chemotherapy-resistant AML cells, without developing graft-vs-host disease, in preclinical models. Further, the feasibility, safety, and potential efficacy of allogeneic DNT therapy were demonstrated among AML patients who relapsed after allo-HSCT (ChiCTR1900022795). However, some AML cells resist DNT-mediated cytotoxicity and the mechanisms remain largely unclear.
To dissect the underlying mechanisms, a flow cytometry-based high throughput screening (HTS) was conducted to identify surface molecules that were differentially expressed during effector-tumour cell interactions. By comparing cell surface protein expression levels between DNTs co-cultured with DNT-susceptible versus -resistant AML cells, we identified a novel TNFα-dependent DNT anti-leukemic pathway against AML. DNTs secreted TNFα upon interacting with susceptible AML targets, which sensitized AML cells, including those previously resistant to DNTs, to greater DNT-mediated cytotoxicity without inducing direct apoptosis. Mechanistically, TNFα unexpectedly signalled through JAK1 in AML cells to upregulate ICAM-1 (CD54). This allowed DNTs to engage AML cells more effectively through an ICAM-1 receptor, LFA-1 (CD18/CD11a), for increased killing. Altogether, this study highlights the utility of the flow cytometry-based HTS to discover important immune-cancer cell interactions, and the potential to augment the TNFα-JAK1-ICAM-1 axis for enhanced DNT therapy against AML, including DNT-resistant AML populations.