Chemotherapy treatment forces leukemic cells into senescence in a distinct subset of acute myeloid leukemia cases, exposing them to immune system attacks by increasing antigen presentation, according to research published in Nature Communications on Sept. 4, 2026.
Researchers tested primary blast cells purified from 21 newly diagnosed, chemotherapy-naïve acute myeloid leukemia (AML) patients against cytarabine, also known as AraC. The team added 400 nM of cytarabine at zero and 72 hours, culturing cells for five days. Testing for senescence-associated beta-galactosidase activity separated the patient samples into two groups: 15 classified as Senescence High, showing more than 10 percent positive cells and a positive fold-change over untreated controls, and six classified as Senescence Low.
Antigen presentation
AraC exposure in Senescence High blasts activated inflammatory programs, p53-dependent DNA damage responses, and interferon pathways. Gene expression profiling revealed significant increases in canonical interferon gamma targets, including IRF8, IRF5, and OAS2, alongside the cell cycle inhibitor CDKN1A. These senescent cells also increased transcript levels for peptide cleavage and transport machinery, including CTSB, as well as costimulatory molecules CD40 and CD86.
Flow cytometry confirmed that Senescence High blasts elevated surface levels of human leukocyte antigen (HLA) class I (HLA-ABC) and class II (HLA-DR) molecules. This surface upregulation correlated directly with senescence-associated beta-galactosidase activity across primary biological replicates.
Immunopeptidomic profiling using liquid chromatography-tandem mass spectrometry showed that Senescence High samples expanded their repertoire of HLA class I-presented peptides after AraC treatment. Many of these eluted peptides mapped to leukemia-associated tumor antigens and curated senescence-associated gene sets from the CellAge and SenePy databases. Most of the peptides identified in the leukemic samples were absent from reference atlases of healthy bone marrow and other non-malignant tissues.
Chromatin remodeling
Mechanistically, the investigators traced the induction of senescence and its resulting immunogenicity to diminished Polycomb Repressive Complex 2 (PRC2) activity. Inhibiting the PRC2 catalytic subunit EZH2 restored human leukocyte antigen expression and activated senescence-related transcriptional pathways in Senescence Low AML blasts, permitting T cell activation in non-senescent samples.
In laboratory models, these antigen-presentation changes strengthened autologous CD4+ and CD8+ T cell responses and restored AML sensitivity to immune checkpoint blockade therapy. Single-cell RNA sequencing reference mapping across multiple patient datasets linked the highest senescence signature scores and HLA expression primarily to monocyte-primed blast clusters, while tests on the monocytic leukemia cell line THP-1 confirmed elevated HLA presentation after a 200 nM cytarabine regimen.
