METTL3 promotes adriamycin resistance in MCF-7 breast cancer cells by accelerating pri-microRNA-221-3p maturation in a m6A-dependent manner

• DOI: 10.1038/s12276-020-00510-w
• Publication Date: 2021-01-08T07:09:58Z
• Authors: Xiaoping Pan; Xiaolv Hong; Sumei Li; Ping Meng; Feng Xiao
• Keywords: Mice, Inbred BALB C; 0303 health sciences; ATP Binding Cassette Transporter, Subfamily B; Adenosine; Antibiotics, Antineoplastic; Mammary Neoplasms, Experimental; Methyltransferases; Article; Neoplasm Proteins; 3. Good health; Repressor Proteins; Mice; MicroRNAs; 03 medical and health sciences; HEK293 Cells; Doxorubicin; Drug Resistance, Neoplasm; MCF-7 Cells; ATP Binding Cassette Transporter, Subfamily G, Member 2; Animals; Humans; Female; RNA Processing, Post-Transcriptional; Apoptosis Regulatory Proteins

AbstractBreast cancer (BC) is the most prevalent malignant neoplasm among women and is the fifth most common cause of cancer-associated death worldwide. Acquired chemoresistance driven by genetic and epigenetic alterations is a significant clinical challenge in treating BC. However, the mechanism of BC cell resistance to adriamycin (ADR) remains to be elucidated. In this study, we identified the methyltransferase-like 3/microRNA-221-3p/homeodomain-interacting protein kinase 2/Che-1 (METTL3/miR-221-3p/HIPK2/Che-1) axis as a novel signaling event that may be responsible for resistance of BC cells to ADR. A dual-luciferase reporter gene assay was employed to test the presence of miR-221-3p binding sites in the 3′UTR of HIPK2. Drug resistance was evaluated by immunoblotting multidrug resistance protein 1 (MDR1) and breast cancer resistance protein (BCRP). Cultured ADR-resistant MCF-7 cells were assayed for their half maximal inhibitory concentration (IC50) values and apoptosis using an MTT assay and Annexin V-FITC/PI-labeled flow cytometry, and the cells were then xenografted into nude mice. METTL3 knockdown was shown to reduce the expression of miR-221-3p by reducing pri-miR-221-3p m6A mRNA methylation, thereby reducing the IC50 value of ADR-resistant MCF-7 cells, reducing the expression of MDR1 and BCRP, and inducing apoptosis. Mechanistically, miR-221-3p was demonstrated to negatively regulate HIPK2 and upregulate its direct target Che-1, thus leading to enhanced drug resistance in ADR-resistant MCF-7 cells. In vitro results were reproduced in nude mice xenografted with ADR-resistant MCF-7 cells. Our work elucidates an epigenetic mechanism of acquired chemoresistance in BC, in support of the METTL3/miR-221-3p/HIPK2/Che-1 axis as a therapeutic target for the improvement of chemotherapy.