Abstract
5-azacytidine (5-aza) is a hypomethylating agent approved for the treatment of high-risk myelodysplastic syndrome (MDS). It is assumed to act by demethylating tumor suppressor genes and via direct cytotoxic effects on malignant cells. In vitro treatment with hypomethylating agents has profound effects on the expression of killer-cell immunoglobulin-like (KIR) receptors on natural killer (NK) cells, as these receptors are epigenetically regulated via methylation of the promoters. Here we investigated the influence of 5-aza on the NK-cell repertoire during cytokine-induced proliferation in vitro and homeostatic proliferation in vivo in patients with high-risk MDS. In vitro treatment of NK cells from both healthy donors and MDS patients with low doses of 5-aza led to a significant increase in expression of multiple KIRs, but only in cells that had undergone several rounds of cell division. Proliferating 5-aza exposed NK cells exhibited increased IFN-γ production and degranulation towards tumor target cells. MDS patients had lower proportions of educated KIR-expressing NK cells than healthy controls but after systemic treatment with 5-aza, an increased proportion of Ki-67+ NK cells expressed multiple KIRs suggesting uptake of 5-aza in cycling cells in vivo. Hence, these results suggest that systemic treatment with 5-aza may shape the NK cell repertoire, in particular during homeostatic proliferation, thereby boosting NK cell-mediated recognition of malignant cells.
Highlights
Epigenetic modifications are a common hallmark of all human cancers [1] and can include alterations in methylation patterns where methyl groups are added or removed from CpG sites in DNA
Myelodysplastic syndrome (MDS) is a group of clonal stem cell disorders characterized by ineffective hematopoiesis, a potential for progression to acute myeloid leukemia (AML) and which is connected to deregulation of innate immune and inflammatory signaling [3]
For the last 10 years, 5-aza has been the first-line treatment for patients with high-risk MDS and acute myeloid leukemia (AML) with dysplastic features and 20-29% marrow blasts [6]. 5-aza and decitabine lack methylation sites effectively acting as DNA methyltransferase inhibitors (DNMTs). 5-aza inhibits DNMT1, which is completely depleted after 5-aza exposure due to the formation of an irreversible covalent bond, leading to loss of DNA methylation marks [7, 8]
Summary
Epigenetic modifications are a common hallmark of all human cancers [1] and can include alterations in methylation patterns where methyl groups are added or removed from CpG sites in DNA. 5-aza inhibits DNMT1, which is completely depleted after 5-aza exposure due to the formation of an irreversible covalent bond, leading to loss of DNA methylation marks [7, 8] In this way, methylation-dependent silencing in cancer cell lines is reversed in a dose-dependent manner, where only low doses that do not disturb replication show hypomethylating effects [9]. In addition to synergistic signaling through activating receptors, NK cell cytotoxicity is tightly controlled by the expression of MHC class I binding receptors including CD94/NKG2A and killer cell immunoglobulin-like receptors (KIRs). Our data show that expression of multiple KIRs was rapidly induced on NK cells during in vitro culture with physiologically relevant low doses of 5-aza This effect was tightly linked to IL-2 driven cellular proliferation and most prominent in less differentiated cells with high proliferative capacity. Our data reveal an imprint of 5-aza on NK cells in vivo and support the notion that the therapeutic effects of 5-aza may be partially mediated via epigenetic remodeling of the immune system
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
