MiRNA-125b inhibits proliferation and migration by targeting SphK1 in bladder cancer

MicroRNAs (miRNAs) are small, non-coding RNAs (18-25 nucleotides) that post-transcriptionally modulate gene expression by negatively regulating the stability or translational efficiency of their target mRNAs.The purpose of this study was to investigate the expression levels of miR-125b in human bladder cancer and its potential role in disease pathogenesis.

The expression level of miR-125b was measured in 40 bladder cancer specimens and adjacent normal breast tissues by quantitative polymerase chain reaction (qPCR). MTT and colony formation assays, transwell, cell cycle assays were conducted to explore the potential function of miR-125b in human T24 bladder cancer cells. Luciferase reporter assays were performed to analyze the regulation of putative target of miR-125b. The effects of modulating miR-125b on endogenous levels of this target were subsequently confirmed via qRT-PCR and Western blot.

The expression of miR-125b in bladder cancer specimens was lower than adjacent normal tissues (P < 0.05). Overexpression of miR-125b inhibited cellular growth, suppressed cellular migration and caused an accumulation of cells in the G1 phase of the cell cycle, Luciferase assays revealed that miR-125b directly targeted the 3'UTR of SphK1. Overexpression of miR-125b led to the downregulation of SphK1 and protein level as assessed by qRT-PCR and Western blot. Targeted knockdown of SphK1 by siRNA significantly inhibited the proliferation of T24 bladder cancer cells.

These findings suggest that miR-125b may act as a tumor suppressor gene in bladder cancer and that, in the future, targeting of this miRNA may provide a novel strategy for the diagnosis and treatment of patients with this lethal disease.