M6A-modified lncRNA HULC promotes osteosarcoma progression by stabilizing GLUT1 mRNA through interaction with TAF15.

BACKGROUND

The overexpression of long noncoding RNA (lncRNA) HULC is recognized as an important contributor to osteosarcoma (OS) progression. However, its precise roles and mechanisms in OS remain unclear, necessitating further investigation.

METHODS

The expression levels of HULC, methyltransferase-like 3 (METTL3), TATA-box-binding protein-associated factor 15 (TAF15), and glucose transporter 1 (GLUT1) were measured using quantitative reverse transcription polymerase chain reaction (qRT-PCR). RNA in situ hybridization and subcellular localization analyses were conducted to determine the spatial distribution of HULC. Methylation of HULC by METTL3 was assessed using methylated RNA immunoprecipitation (MeRIP) assays. Functional assays, including CCK8 and transwell assays, were conducted to evaluate cell viability, migration, and invasion. Immunofluorescence staining of E-cadherin and N-cadherin was performed to assess the epithelial-mesenchymal transition (EMT). Glycolysis was evaluated through extracellular acidification rate, oxygen consumption rate, glucose uptake, lactate production, and ATP levels. Protein levels of glycolysis-related markers, TAF15, and GLUT1 were analyzed by Western blotting (WB). Xenograft and lung metastasis models were used to examine the roles of HULC and METTL3 in OS tumorigenesis and metastasis in vivo, and the interactions between TAF15 and HULC or GLUT1 were investigated using RNA immunoprecipitation (RIP) and RNA pull-down assays, while fluorescence in situ hybridization confirmed the co-localization of HULC and TAF15.

RESULTS

Elevated HULC expression was found to be correlated with poor prognosis in OS patients. In addition, METTL3-mediated m6A modification stabilized HULC expression, which promoted OS cell viability, migration, EMT, and glycolysis, and these effects could be reversed upon METTL3 downregulation. In vivo, METTL3 knockdown reduced tumor growth and lung metastasis primarily by decreasing HULC expression. Mechanistically, HULC enhanced GLUT1 mRNA stability by interacting with TAF15. Silencing TAF15 or GLUT1 mitigated the effects of HULC overexpression, suppressing OS cell viability, metastasis, EMT, and glycolysis.

CONCLUSION

M6A modification of HULC promotes OS progression by stabilizing GLUT1 mRNA through interaction with TAF15, highlighting a potential regulatory axis in OS pathogenesis and providing insights into therapeutic strategies targeting METTL3, HULC, or TAF15.