RNA-binding protein hnRNPD induces epithelial-mesenchymal transition in Wilms' tumor via facilitating MAP4K4 mRNA stability.

Wilms' tumor (WT) is one of the most common pediatric abdominal malignancies. The RNA-binding protein heterogeneous nuclear ribonucleoprotein D (hnRNPD) is related to cancer progression through regulating target mRNA stability. Nonetheless, its expression profile and value for WT are largely unexplored. Human renal proximal tubular epithelial cells (RPTEC) and WT cells (17.94, HFWT) were employed as experimental models for exploring hnRNPD's effect on WT progression. Subsequently, potential downstream targets of hnRNPD were identified through bioinformatics analysis. Functional validation was performed in vitro by modulating hnRNPD and its candidate targets via gene silencing and overexpression methods. Alterations in gene expression was analyzed through qRT-PCR as well as Western blot. Besides, CCK-8 was conducted to evaluate cell proliferation, whereas scratch and Transwell assays to determine cell migration alongside invasion separately. Additionally, critical epithelial-mesenchymal transition (EMT)-associated protein expression, namely E-cadherin, N-cadherin, alongside vimentin, was detected to assess regulatory impact of hnRNPD on the EMT process. hnRNPD mRNA and protein expression significantly elevated within 17.94 and HFWT cells than in RPTEC cells. Silencing of hnRNPD in 17.94 cells inhibited cell proliferation, migration, and invasion. Concurrently, N-cadherin and Vimentin protein levels declined, and E-cadherin protein level increased. Conversely, overexpression of hnRNPD in HFWT cells markedly enhanced their malignant phenotypes and promoted EMT. Bioinformatics analysis identified mitogen-activated protein kinase kinase kinase kinase 4 (MAP4K4) as a potential downstream target of hnRNPD in WT. Mechanistically, hnRNPD overexpression extended the half-life of MAP4K4 mRNA, and a specific physical interaction between hnRNPD protein and MAP4K4 mRNA was observed. Functional rescue experiments further demonstrated that silencing MAP4K4 inhibited tumor malignant progression, while overexpression of MAP4K4 reversed the tumor-suppressive effects induced by hnRNPD silencing. hnRNPD may promote EMT in WT cells by stabilizing MAP4K4 mRNA, suggesting a critical role for the hnRNPD-MAP4K4 axis in driving tumor progression.