Quercetin suppresses retinoblastoma cell proliferation and invasion and facilitates oxidative stress-induced apoptosis through the miR-137/FNDC5 axis.

Retinoblastoma (RB) constitutes a prevalent malignancy in clinic and usually occurs in children under the age of 5 years old. The increased frequency of malignant tumor metastases and the delayed diagnosis and treatment caused unsatisfactory therapeutic efficiency. Quercetin was formerly identified to impede tumor growth in certain malignancies. Our study attempted to investigate the effects and mechanisms of quercetin in Rb development, in order to provide an effective clinical therapeutic approach. Rb cell lines (WER1-RB1 and Y79) were incubated with different concentrations of quercetin, and then cell proliferation, invasion, apoptosis, and oxidative stress were determined. It was showed that quercetin restrained Rb cell proliferation and invasion, and induced cell apoptosis and oxidative stress in a dose dependent manner. Moreover, we found that quercetin incubation upregulated miR-137 expression in Rb cells. MiR-137 inhibition abrogated quercetin-mediated inhibition of Rb cell progression. Furthermore, dual-luciferase reporter gene assay validated that fibronectin type III domain-containing protein 5 (FNDC5) was a target for miR-137. MiR-137 overexpression restrained proliferation and invasion, and enhanced apoptosis and oxidative stress in Rb cells, whereas FNDC5 overexpression abrogated these effects. Additionally, nude mice were injected with WER1-RB1 cells to establish a xenograft tumor model, and then treated with 50 or 100 mg/kg quercetin. Quercetin treatment mitigated xenograft tumor growth in nude mice. In conclusion, quercetin restrained proliferation and invasion, and induced apoptosis and oxidative stress in Rb cells through regulating the miR-137/FNDC5 pathway. We expected that our study could provide an effective approach for Rb treatment. However, quercetin and miR-137 may have off-target effects in Rb cells, and our study still has certain limitations. Therefore, we will investigate the effects of quercetin on other signaling pathways in Rb cells and explore the application of combination therapy in follow-up experiments, in order to provide a rigorous research basis for the treatment of Rb with quercetin.