Deficiency of miR-155 in leukemic B-cells results in cell cycle arrest and deregulation of MIR155HG/TP53INP1/CDKN1A/CCND1 network

Abstract

Background. Cell cycle progression and leukemia development are tightly regulated processes in which even a small imbalance in the expression of cell cycle regulatory molecules and microRNAs (miRNAs) can lead to an increased risk of cancer/leukemia development. Here, we focus on the study of a ubiquitous, multifunctional, and oncogenic miRNA-hsa-miR-155-5p (miR-155, MIR155HG), which is overexpressed in malignancies including chronic lymphocytic leukemia (CLL). Nonetheless, the precise mechanism of how miR-155 regulates the cell cycle in leukemic cells remains the subject of extensive research. Methods. We edited the CLL cell line MEC-1 by CRISPR/Cas9 to introduce a short deletion within the MIR155HG gene. To describe changes at the transcriptome and miRNome level in miR-155-deficient cells, we performed mRNA-seq/miRNA-seq and validated changes by qRT-PCR. Flow cytometry was used to measure cell cycle kinetics. A WST-1 assay, hemocytometer, and Annexin V/PI staining assessed cell viability and proliferation. Results. The limited but phenotypically robust miR-155 modification impaired cell proliferation, cell cycle, and cell ploidy. This was accompanied by overexpression of the negative cell cycle regulator p21/CDKN1A and Cyclin D1 ( CCND1 ). We confirmed the overexpression of canonical miR-155 targets such as PU.1, FOS, SHIP-1, TP53INP1 and revealed new potential targets ( FCRL5, ISG15, and MX1). Conclusions. We demonstrate that miR-155 deficiency impairs cell proliferation, cell cycle, transcriptome, and miRNome via deregulation of the MIR155HG/TP53INP1/CDKN1A/CCND1 axis. Our CLL model is valuable for further studies to manipulate miRNA levels to revert highly aggressive leukemic cells to nearly benign or non-leukemic types. (c) 2024 The Authors. Published by Elsevier Inc. on behalf of Instituto Mexicano del Seguro Social (IMSS). This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/)