Abstract
Quercetin and 2-Methoxyestradiol (2-ME) are promising anti-cancer substances. Our previous in vitro study showed that quercetin synergized with 2-Methoxyestradiol exhibiting increased antiproliferative and proapoptotic activity in both androgen-dependent LNCaP and androgen-independent PC-3 human prostate cancer cell lines. In the present study, we determined whether their combination could inhibit LNCaP and PC-3 xenograft tumor growth in vivo and explored the underlying mechanism. Human prostate cancer LNCaP and PC-3 cells were inoculated subcutaneously in male BALB/c nude mice. When xenograft tumors reached about 100 mm3, mice were randomly allocated to vehicle control, quercetin or 2-Methoxyestradiol singly treated and combination treatment groups. After therapeutic intervention for 4 weeks, combination treatment of quercetin and 2-ME i) significantly inhibited prostate cancer xenograft tumor growth by 46.8% for LNCaP and 51.3% for PC-3 as compared to vehicle control group, more effective than quercetin (28.4% for LNCaP, 24.8% for PC3) or 2-ME (32.1% for LNCaP, 28.9% for PC3) alone; ii) was well tolerated by BALB/c mice and no obvious toxic reactions were observed; iii) led to higher Bax/Bcl-2 ratio, cleaved caspase-3 protein expression and apoptosis rate; and iv) resulted in lower phosphorylated AKT (pAKT) protein level, vascular endothelial growth factor protein and mRNA expression, microvascular density and proliferation rate than single drug treatment. These effects were more remarkable compared to vehicle group. Therefore, combination of quercetin and 2-ME can serve as a novel clinical treatment regimen owning the potential of enhancing antitumor effect on prostate cancer in vivo and lessening the dose and side effects of either quercetin or 2-ME alone. These in vivo results will lay a further solid basis for subsequent researches on this novel therapeutic regimen in human prostate cancer.
Highlights
Prostate cancer is the second leading cause of cancer mortality in males, with an estimated 233,000 new cases and 29,480 deaths in United States in 2014 [1]
Male BALB/c nude mice with PC-3 and LNCaP cells xenograft tumors were treated with vehicle, Que or 2-ME and their combination and the procedure lasted for 4 weeks
Following our previous in vitro research [14], we conducted a study of combining quercetin with 2-ME to act on human prostate cancer LNCaP and PC-3 xenograft tumor in male BALB/c nude mouse and found that combined use enhanced inhibition of xenograft tumor growth which was attributed to induction of apoptosis, inhibition of phosphatidylinositol 3-kinase (PI3K)/Akt signal pathway and angiogenesis
Summary
Prostate cancer is the second leading cause of cancer mortality in males, with an estimated 233,000 new cases and 29,480 deaths in United States in 2014 [1] It can be cured by radical prostatectomy or radiation at early stage, most patients will suffer from local recurrence and distant metastasis later [2]. Combination of docetaxel and prednisone, the standard first-line systemic chemotherapy for CRPC, is not curative and only prolongs overall survival time for a short period. It makes patients suffer from severe side effects [4].
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