W58 - Transcriptomic Comparison of Pediatric Acute Myeloid Leukemia Cells Sensitive or Resistant to Engineered Tr1-like Cell Mediated Killing

Type 1 regulatory T (Tr1) cells are pivotal players in maintaining peripheral tolerance. These IL-10 secreting, FOXP3^- regulatory T cells develop in the periphery and exert their suppressive function via secretion of IL-10 and granzyme B-mediated killing of myeloid cells. The suppressive properties of Tr1 cells make them a unique immunotherapy option for autoimmune, inflammatory and transplant-related disorders. Additionally, due to their myeloid-killing capability, they could be a cancer immunotherapy tool. However, Tr1 cells are low in frequency in peripheral blood and hard to expand in vitro, thus limiting their use as cell therapeutics. To overcome this, our lab generated a cell therapy product by engineering human CD4⁺ T cells to overexpress IL10 (CD4^IL-10). CD4^IL-10 are functionally similar to Tr1 cells, with high suppressive capacity and cytotoxic properties against myeloid cells. We tested the killing of CD4^IL-10 against a set of 40 primary pediatric AML blasts and grouped these blasts as sensitive, intermediate-resistant or resistant to killing. We performed bulk RNA sequencing and selected 2 sensitive and 2 resistant blasts as well as CD4^IL-10 cells from two donors to compare the transcriptional changes in both cell types before and after in vitro co-culture. Our analysis revealed differentially expressed markers specific to resistant blasts that could be predictive of CD4^IL-10-mediated killing resistance. In conclusion, CD4^IL-10 are cytotoxic cells that can kill majority of AML blasts. Sensitive and resistant pediatric AML blasts have distinct transcriptional profiles which can be used to further predict the sensitivity vs resistance to immunotherapy in the future.