m6A-dependent up-regulation of DRG1 by METTL3 and ELAVL1 promotes growth, migration, and colony formation in osteosarcoma.

Osteosarcoma (OS) is a malignant tumor commonly observed in children and adolescents. Developmentally regulated GTP-binding protein (DRG) 1 plays an important role in embryonic development; aberrantly expressed DRG1 has been associated with pathological processes in cancer. The present study aimed to explore the role of DRG1 in OS and the mechanisms underlying DRG1 overexpression in OS. Clinical studies were performed to evaluate Drg1 expression in OS tissues and to identify a correlation between Drg1 expression and the clinicopathological features in patients with OS. Drg1 was knocked down in OS cells to determine its effects on cell viability, cell cycle distribution, apoptosis, migration, invasion, and colony formation rate. METTL3 and ELAVL1 were also silenced to determine their effects on the levels of N6-methyladenosine (m6A), RNA stability, and Drg1 expression. Higher levels of Drg1 mRNA and protein were observed in OS tissues than those in paracancerous tissues. High expression of DRG1 was associated with large tumor size and advanced clinical stages in OS. Silencing of Drg1 resulted in decreased viability and inhibition of the migration and colony formation abilities of OS cells; it also resulted in cell cycle arrest in the G2/M stage and induced apoptosis. Knockdown of METTL3 led to decreased m6A and Drg1 mRNA levels. ELAVL1 knockdown impaired the stability of DRG1 mRNA, thereby reducing both the mRNA and protein levels of DRG1. In all, DRG1 exerted tumorigenic effects in OS, and the up-regulation of DRG1 in OS was induced by METTL3 and ELAVL1 in an m6A-dependent manner.

Ling Z ，Chen L ，Zhao J 《-》

The m6A methyltransferase METTL3 promotes osteosarcoma progression by regulating the m6A level of LEF1.

Osteosarcoma(OS) is the most common and aggressive malignant bone sarcoma,which occurs in rapidly growing bones in children and adolescents. However, the underlying molecular mechanisms of OS development have not been fully illustrated. N6-Methyladenosine (m6A) is the most prevalent internal chemical modification of mRNAs, which is involved in many pathological processes in cancer development. However, its role and regulatory mechanism in OS remain unknown. In this study, we aimed to investigate the roles of m6A and its methyltransferase METTL3 in OS development. The results showed that m6A level for RNA methylation and the expression level of METTL3 were up-regulated in human OS tissues and OS cell lines. Functionally, lentivirus-mediated METTL3 silence in HOS and SAOS-2 cells inhibited the cell proliferation, migration and invasion ability. Further mechanism analysis suggested that METTL3 silence decreased the m6A methylation and total mRNA level of lymphoid enhancer-binding factor 1 (LEF1), followed by inhibited the activity of Wnt/β-catenin signaling pathway. Moreover, LEF1 over-expression abrogates the repressive effects of METTL3 silence on the proliferation, migration and invasion abilities of OS cells. Together, these results revealed that the m6A methyltransferase METTL3 promotes osteosarcoma cell progression by regulating the m6A level of LEF1 and activating Wnt/β-catenin signaling pathway.

Miao W ，Chen J ，Jia L ，Ma J ，Song D ... -  《-》

METTL3 promotes the progression of osteosarcoma through the N6-methyladenosine modification of MCAM via IGF2BP1.

The molecular mechanisms of osteosarcoma (OS) are complex. In this study, we focused on the functions of melanoma cell adhesion molecule (MCAM), methyltransferase 3 (METTL3) and insulin like growth factor 2 mRNA binding protein 1 (IGF2BP1) in OS development. qRT-PCR assay and western blot assay were performed to determine mRNA and protein expression of MCAM, METTL3, IGF2BP1 and YY1. MTT assay and colony formation assay were conducted to assess cell proliferation. Cell apoptosis, invasion and migration were evaluated by flow cytometry analysis, transwell assay and wound-healing assay, respectively. Methylated RNA Immunoprecipitation (MeRIP), dual-luciferase reporter, Co-IP, RIP and ChIP assays were performed to analyze the relationships of MCAM, METTL3, IGF2BP1 and YY1. The functions of METTL3 and MCAM in tumor growth were explored through in vivo experiments. MCAM was upregulated in OS, and MCAM overexpression promoted OS cell growth, invasion and migration and inhibited apoptosis. METTL3 and IGF2BP1 were demonstrated to mediate the m6A methylation of MCAM. Functionally, METTL3 or IGF2BP1 silencing inhibited OS cell progression, while MCAM overexpression ameliorated the effects. Transcription factor YY1 promoted the transcription level of METTL3 and regulated METTL3 expression in OS cells. Additionally, METTL3 deficiency suppressed tumor growth in vivo, while MCAM overexpression abated the effect. YY1/METTL3/IGF2BP1/MCAM axis aggravated OS development, which might provide novel therapy targets for OS.

Song D ，Wang Q ，Yan Z ，Su M ，Zhang H ，Shi L ，Fan Y ，Zhang Q ，Yang H ，Zhang D ，Liu Q ... -  《Biology Direct》

Methylation recognition protein YTH N6-methyladenosine RNA binding protein 1 (YTHDF1) regulates the proliferation, migration and invasion of osteosarcoma by regulating m6A level of CCR4-NOT transcription complex subunit 7 (CNOT7).

Wei K ，Gao Y ，Wang B ，Qu YX ... -  《-》

Silencing METTL3 inhibits the proliferation and invasion of osteosarcoma by regulating ATAD2.

Osteosarcoma is the most common primary malignant bone tumor in children and young adults. RNA N6-methyladenosine (m6A) is the most abundant internal modification in mammalian mRNA, which is involved in tumorigenesis and tumor progression. It has been reported that methyltransferase-like 3 (METTL3), the first reported m6A "writer", plays critical roles in cancer progression. However, its role and molecular mechanism in osteosarcoma is poor studied. In this study, we aimed to investigate the functional role and underlying mechanism of METTL3 in the progression of osteosarcoma. We detected the mRNA expression of METTL3 in osteosarcoma cell lines, and immunofluorescence assay was performed to observe the location of METTL3. Cell lines with METTL3 gene overexpression or knockdown were established by pcDNA3.1-METTL3 or siRNA interferences in order to determine the function of METTL3 in osteosarcoma in vitro. Transcriptomic RNA sequencing (RNA-seq) were used to screen the target genes of METTL3 in osteosarcoma. We found that METTL3 localized in cytoplasm and nucleus of osteosarcoma cells. Silencing METTL3 in SAOS-2 and MG63 cells significantly inhibited the m6A methylation level, proliferation, migration, and invasion abilities, as well as promoted cell apoptosis. However, up-regulation of METTL3 had no significant effect on the biological behaviors of U2OS cells. Further mechanism analysis suggested that METTL3 knockdown inhibited the expression of ATPase family AAA domain containing 2 (ATAD2). Moreover, ATAD2 knockdown inhibited the proliferation and invasion of SAOS-2 and MG63 cells, while its overexpression showed a significant increase in cell proliferation and invasion. Furthermore, METTL3 knockdown abrogated the promoting effects of ATAD2 overexpression on osteosarcoma cells proliferation and invasion. Overall, our study revealed that METTL3 functions as an oncogene in the growth and invasion of osteosarcoma by regulating ATAD2, suggesting a potential therapeutic target for osteosarcoma treatment.

Zhou L ，Yang C ，Zhang N ，Zhang X ，Zhao T ，Yu J ... -  《-》