THE ROLE AND MECHANISM OF UPREGULATED TYPE I INTERFERON SIGNALING PATHWAY IN THE PATHOGENESIS OF CHRONIC MYELOMONOCYTIC LEUKEMIA

Introduction

Chronic Myelomonocytic Leukemia (CMML) is a rare, malignant hematopoietic system tumour whose pathogenesis remains unclear. This primarily affects elderly males and may transform into acute myeloid leukemia. Elevated innate immune and inflammation-related pathways were found in CMML patients' monocytes. Activation of type I interferon signalling pathway was significant and correlated with prognosis. Strong expression of interferon-regulated genes in patients pointed to type 1 interferon signalling's role in CMML's pathogenesis. TET2 and SRSF2 mutations, affecting gene expression and cellular function, are common in CMML, with a synergistic effect shown in mouse model experiments.

Methods

We studied 14 untreated CMML patients, analysing their peripheral blood monocytes and 13 inflammatory cytokines via transcriptome sequencing and Cytometric Bead Array. SRSF2-P95H/TET2 mutation cell lines were also created.

Results

Exome and transcriptome sequencing in 14 CMML patients revealed frequent TET2, ASXL1, and SRSF2 mutations. Compared to controls, CMML cells displayed activated innate immune and inflammation pathways, including elevated levels of IL-10, IFN-α2, IL-8, IL-12p70, IL-6, and IL-17A. Higher 1-IFN scores, indicating the activation level of the type 1 interferon pathway, were seen in MP-CMML patients, suggesting a link with poor prognosis. In vitro, interferon pathway inhibition induced apoptosis in CMML monocytes and reduced protein P38 phosphorylation, inhibiting cell proliferation in THP-1/U937. TET2 loss-of-function mutations and SRSF2-P95H mutations overexpressed type 1 interferon pathway genes, leading to increased culture supernatant interferon levels in HEK-293T cells.

Conclusions

Study shows TET2 loss-of-function/SRSF2-P95H mutations in CMML trigger type I interferon pathway activation, promoting P38 and PI3K phosphorylation, potentially partly causing CMML.