Selection and Charaterization of İmmune-Resistant Acute Myeloid Leukemia Cells

Abstract

Resistance to immunity is associated with the selection of cancer cells with superior capacities to survive inflammatory reactions. In the case of AML, immune reactions induce dynamic changes at genetic and epigenetic levels, resulting in unique morphological, phenotypic, and genetic characteristics. To investigate this phenomenon, we developed an ex-vivo immune selection model, isolating residual subpopulations termed "immune-experienced" AML (ieAML) cells. Upon surviving immune reactions, these malignant blasts exhibited reduced proliferation, signs of myeloid differentiation and activation, and decreased immunogenicity. The observed low-pace proliferation, differentiation, and decreased immunogenicity were associated with immune resistance in myeloid leukemia. Furthermore, in the context of immune experience, ieAML cells displayed variations in behavior, including adhesion, migration, and polarization capacities. These immune-experienced AML subpopulations were found to impede T cell responses, resulting in reduced secretion of key anti-tumor immune response mediators. Transcriptomic analyses identified a limited set of commonly altered pathways and differentially expressed genes (DEGs) in all ieAML cells derived from various parental cell lines. Molecular signatures associated with interferon (IFN) and inflammatory cytokine signaling were enriched in AML cells resistant to T cell-mediated immune reactions. Individual ieAML lines exhibited diverse cellular responses upon subjecting them to mixed leukocyte-leukemia cell reactions (MLLRs), highlighting the variation in the regulation of similar pathways across different ieAML cell lines. Notably, distinctive traits of inflammatory pathways, such as IFN-γ, IFN-α, TNF-α, TGF-β, apoptosis, IL-6, and IL-2 signaling, were enriched. Transcription factors c-MYB and KLF6 emerged as potential markers for ieAML cells, with their expression and nuclear localization observed in subpopulations of blasts in AML patients' bone marrow aspirates. The nuclear localization of KLF6 and c-MYB transcription factors served as potential indicators of immune encounter status. Interestingly, the immune modulatory capacities of ieAML cells were transient and waned when immune selection pressure was removed. Despite this, our findings suggest that myeloid leukemia cells harbor subpopulations capable of adapting to the challenging conditions imposed by immune reactions. The prior "immune experience" of these cells may contribute to secondary resistance to immune intervention therapies. This study sheds light on the dynamics of immune interactions in AML and underscores the importance of understanding the adaptive mechanisms that cancer cells employ to escape immune surveillance.