The M6A Methyltransferase METTL14 Promotes Myelodysplastic Syndromes Development Via PI3K/Akt Signaling Pathway

Background: RNA N6-methyladenosine (m⁶A) plays a critical role in normal and malignant hematopoiesis. The m⁶A methyltransferases METTL3 and METTL14 were reported as oncogenes in acute myeloid leukemia. Epigenetic dysregulation is a prominent biological feature of myelodysplastic syndromes (MDS), however, whether RNA methylation dysregulation exists in MDS, and what's the functions of m6A methyltransferases are largely unknown.

Methods: The global m⁶A modification level of RNA in bone marrow was detected in MDS patients by colorimetric method, and the expression level of METTL14 in bone marrow of MDS patients was detected by q-PCR. Both gain- and loss-of-function experiments were performed to study the role of METTL14 in MDS. M⁶A sequencing and RNA sequencing were examined to explore the potential signaling pathways and target genes that mediated METTL14 function in MDS.

Results: We detected obvious RNA m⁶A dysregulation in bone marrow of MDS patients compared with normal controls, and found that the up-regulation of the global m⁶A modification is closely related to higher-risk category and worse survival of MDS patients. By analyzing the MDS public database (GSE_58831) and q-PCR data of MDS patients in our center, we found that among 23 classical m⁶A related genes, m⁶A methyltransferase METTL14 was the key factor causing the m⁶A dysregulation in MDS: high expression of METTL14 was associated with higher disease risk stratification, more bone marrow blasts, poorer prognosis, and higher response rates to hypomethylating agents (HMAs).

In order to explore the functions of METTL14 in MDS, we performed gain- and loss-of-function experiments in MDS cell line MDSL in vitro. It was observed that the expression of METTL14 promoted the cell proliferation and clone formation ability of MDS cells by inducing cell apoptosis and differentiation. More interestingly, we found that HMAs down-regulated the level of global m6A modification by inhibiting METTL14 expression, and the expression of METTL14 could increase the sensitivity of MDS cells to HMAs in MDS cells.

To search for upstream regulatory genes of METTL14, we analyzed the ChIPBase online database and identified ELF1 might be the potential upstream transcription factor. The relationship between ELF1 and METTL14 was further confirmed by ELF1-overexpressed and ELF1-knowndowned MDSL cell lines.

To explore the relationship between gene mutations and METTL14, we analyzed the correlations between next generation sequencing (NGS) data and METTL14 expression level in MDS patients in our center, and found that the METTL14 expression level was significantly increased in MDS patients carrying TP53 gene mutations (P<0.05). The increased METTL14 and ELF1 expression were all observed in MDS cell lines with introduction of TP53 missense mutations (M237I and Y220C) or TP53 knockdown.

Mechanistically, m⁶A sequencing and RNA-seq sequencing revealed METTL14 promoted MDS development via PI3K/Akt signaling pathway, and the potential target genes involved in PI3K/Akt signaling pathway were ANGPT1, CDK6, FGFR2, GNG11, IGF1R et al.

Conclusion：

Herein, we reported RNA m⁶A methylation dysregulation did exist in MDS, and m⁶A methyltransferase METTL14 was an important regulatory factor. Higher METTL14 expression was associated with higher-risk stratification, poorer survival, and better response to HMAs in MDS patients. METTL14 was required for the cell growth and response to HMAs in MDS cells. TP53 mutations were significantly correlated with the up-regulation of METTL14 expression level, and TP53 mutations could induce METTL14 overexpression by regulating transcription factor ELF1. Mechanistically, METTL14 exerts its oncogenic role via PI3K/Akt signaling pathway. Our findings highlighted that METTL14 could potentially be a novel therapeutic target in MDS especially those with TP53 mutations.

No relevant conflicts of interest to declare.