Background and purpose: Interleukin-6 (IL-6) causes the progression of prostate cancer through pSTAT3, pERK1/2, and pAKT cell signaling proteins. Quercetin, an herbal antioxidant, has anti-tumor effect. The aim of this study was to evaluate the effects of quercetin on IL-6 gene expression, and the above cellular signaling proteins in PC3 prostate cancer cells.

Materials and methods: In this experimental study, PC3 cells were treated with different concentrations of quercetin at 0, 10, 50, and 100 μM.  Then, IL-6 concentration was determined in cell culture media. Also, total RNA and the cellular signaling proteins aforementioned were extracted from PC3 and used for determining IL-6 gene expression by quantitative real-time RT-PCR and western blot analysis, respectively.

Results: The quercetin IC₅₀ for PC3 prostate cancer cells was 100 μM. Elevation of quercetin concentration in cell culture media increased the IL-6 gene expression and protein synthesis. At 50 and 100 μM of quercetin, IL-6 protein synthesis increased significantly (P<0.05) to 13.36% and 36.86%, respectively, compared to those in control. Furthermore, quercetin suppressed pSTAT3, pERK1/2, and pAKT cell signaling proteins at dose concentrations more than 150 μM.

Conclusion: The effects of quercetin on PC3 cells could have resulted from reduction of pSTAT3, pERK1/2, pAKT, induction of the oxidative stress and generation of reactive oxygen species. Therefore, quercetin can be considered as a useful therapeutic agent in treatment of prostate cancer.