Quercetin synergizes with 2-methoxyestradiol inhibiting cell growth and inducing apoptosis in human prostate cancer cells

Quercetin synergizes with 2-methoxyestradiol inhibiting cell growth and inducing apoptosis in human prostate cancer cells.

Lack of effective treatment options for castration-resistant prostate cancer reinforces the great need to develop novel drug therapies. Quercetin is a plant-derived flavonoid that can induce apoptosis in prostate cancer cells. 2-Methoxyestradiol (2-ME) is an endogenous estrogenic metabolite that also has antineoplastic activity. However, these two agents have limited bioavailability. Herein, we explored the antiproliferative and proapoptotic activities of quercetin combined with 2-ME in both androgen-dependent LNCaP and androgen-independent PC-3 human prostate cancer cell lines. Compared to quercetin and 2-ME alone, combining quercetin with 2-ME at appropriate concentrations i) showed synergistic antiproliferative and proapoptotic activities; ii) increased G2/M phase population of cells; iii) decreased the ratio of Bcl-2/Bax significantly. The combination of quercetin and 2-ME is a new clinically relevant treatment regimen which has the potential of enhancing the antitumor effect on prostate cancer and lessening the side effect of either quercetin or 2-ME alone.

Dietary flavonoid fisetin: a novel dual inhibitor of PI3K/Akt and mTOR for prostate cancer management.

Epidemiologic and case control population based studies over the past few decades have identified diet as an important determinant of cancer risk. This evidence has kindled interest into research on bioactive food components and has till date resulted in the identification of many compounds with cancer preventive and therapeutic potential. Among such compounds has been fisetin (3,7,3',4'-tetrahydroxyflavone), a flavonol and a member of the flavonoid polyphenols that also include quercetin, myricetin and kaempferol. Fisetin is commonly found in many fruits and vegetables such as apples, persimmons, grapes, kiwis, strawberries, onions and cucumbers. We evaluated the effects of fisetin against melanoma and cancers of the prostate, pancreas and the lungs. Using prostate and lung adenocarcinoma cells, we demonstrated that fisetin acts as a dual inhibitor of the PI3K/Akt and the mTOR pathways. This is a significant finding considering the fact that mTOR is phosphorylated and its activation is more frequent in tumors with overexpression of PI3K/Akt. Dual inhibitors of PI3K/Akt and mTOR signaling have been suggested as valuable agents for treating such cancers. Here, we summarize our findings on the dietary flavonoid fisetin and its effects on cancer with particular focus on prostate cancer. Our observations and findings from other laboratories suggest that fisetin could be a useful chemotherapeutic agent that could be used either alone or as an adjuvant with conventional chemotherapeutic drugs for the management of prostate and other cancers.