Suppression of microRNA-125a-5p upregulates the TAZ-EGFR signaling pathway and promotes retinoblastoma proliferation.

Retinoblastoma is the most common intraocular malignancy that occurs during childhood; however, the mechanism underlying retinoblastoma proliferation and progression remains unclear. MicroRNAs (miRNAs) play an important role in the regulation of a myriad of biological processes in various types of cancer. In this study, we performed microarray analysis followed by qRT-PCR using four classes of retinoblastoma tissues with increasing cTNM classification stages to identify crucial miRNAs whose expression was correlated with retinoblastoma progression. miR-125a-5p was downregulated, and its expression levels were inversely correlated with cell proliferation in retinoblastoma compared with adjacent non-tumor retinal tissues. The overexpression of miR-125a-5p significantly suppressed cell proliferation and tumor formation in retinoblastoma. We further identified the transcriptional co-activator with PDZ binding motif (TAZ) as a direct target of miR-125a-5p. Importantly, TAZ levels were inversely correlated with miRNA-125a-5p expression, and TAZ promoted retinoblastoma cell proliferation. Moreover, the overexpression of miR-125a-5p led to a decrease in TAZ expression and downstream EGFR signaling pathway activation both in vitro and vivo. Finally, TAZ overexpression in retinoblastoma cells overexpressing miR-125a-5p restored retinoblastoma cell proliferation and EGFR pathway activation. Taken together, our data demonstrated that miR-125a-5p functions as an important tumor suppressor that suppresses the EGFR pathway by targeting TAZ to inhibit tumor progression in retinoblastoma. Thus, the miR-125a-5p/TAZ/EGFR axis may be a potential therapeutic target for retinoblastoma.