Investigation of the anti-cancer effect of quercetin on HepG2 cells in vivo

<div><p>Quercetin, a natural polyphenolic flavonoid compound, can inhibit the growth of several malignant cancers. However, the mechanism still remains unclear. Our previous findings have suggested that quercetin can significantly inhibit HepG2 cell proliferation and induce cell apoptosis <i>in vitro</i>. It can also affect cell cycle distribution and significantly decrease cyclin D1 expression. In this study, we investigated the anti-cancer effect of quercetin on HepG2 tumor-bearing nude mice and its effect on cyclin D1 expression in the tumor tissue. First, the nude murine tumor model was established by subcutaneous inoculation of HepG2 cells, then quercetin was administered intraperitoneally, and the mice injected with saline solution were used as controls. The daily behavior of the tumor-bearing mice was observed and differences in tumor growth and survival rate were monitored. The expression of cyclin D1 in isolated tumor sections was evaluated by immunohistochemistry. We found that HepG2 tumor became palpable in the mice one-week post-inoculation. Tumors in the control group grew rapidly and the daily behavior of the mice changed significantly, including listlessness, poor feeding and ataxia. The mice in quercetin-treated group showed delayed tumor growth, no significant changes in daily behavior, and the survival rate was significantly improved. Finally, we observed increased tumor necrosis and a lighter cyclin D1 staining with reduced staining areas. Our findings thus suggest that quercetin can significantly inhibit HepG2 cell proliferation, and this effect may be achieved through the regulation of cyclin D1 expression.</p></div

Tumor growth curves of the subcutaneous HepG2 tumor-bearing mice.

<p>Compared to the control group, the mice in the quercetin-treated group showed delayed tumor growth and a smaller tumor volume (p < 0.05).</p

Comparison of the immunohistochemistry scoring of cyclin D1 expression in HepG2 tumor tissues between the quercetin-treated and control groups (control vs quercetin, *<i>p</i>< 0.05).

<p>Comparison of the immunohistochemistry scoring of cyclin D1 expression in HepG2 tumor tissues between the quercetin-treated and control groups (control vs quercetin, *<i>p</i>< 0.05).</p

Survival curves of the subcutaneous HepG2 tumor-bearing mice.

<p>Compared to the control group, mice in the quercetin-treated group showed prolonged survival rate.</p

Immunohistochemistry analysis of cyclin D1 expression in subcutaneous tumor tissues.

<p>A: Immunohistochemistry images of cyclin D1 expression in subcutaneous tumor tissues; B: Comparison of the cyclin D1 positive areas between the quercetin-treated and control groups (*p < 0.05).</p