The flavonoid quercetin inhibits pancreatic cancer growth in vitro and in vivo

Abstract

Objectives: The flavonoid quercetin holds promise as an antitumor agent in several preclinical animal models. However, the efficacy of oral administration of quercetin in a pancreatic cancer mouse model is unknown.

Methods: The antiproliferative effects of quercetin alone or in combination with gemcitabine were tested in 2 human pancreatic cancer cell lines using cell count and MTT assays. Apoptosis was evaluated by flow cytometry. Tumor growth in vivo was investigated in an orthotopic pancreatic cancer animal model using bioluminescence. Quercetin was administered orally in the diet.

Results: Quercetin inhibited the growth of pancreatic cancer cell lines, which was caused by an induction of apoptosis. In addition, dietary supplementation of quercetin attenuated the growth of orthotopically transplanted pancreatic xenografts. The combination of gemcitabine and quercetin had no additional effect compared with quercetin alone. In vivo quercetin caused significant apoptosis and reduced tumor cell proliferation.

Conclusions: Our data provide evidence that oral administration of quercetin was capable of inhibiting growth of orthotopic pancreatic tumors in a nude mouse model. These data suggest a possible benefit of quercetin in patients with pancreatic cancer.

Figure 1

MIA PaCa-2 and BxPC-3 cells were treated with quercetin (10, 30, 50, and 75 μM), gemcitabine (0.001, 0.01, 0.1, 1, and 10 μg/ml), or vehicle for 48 hours. Cell proliferation was assessed by (A) cell count and (B) MTT. *, p<0.01 vs. quercetin 0 μM or gemcitabine 0 μg/ml. The insets (A) show cells treated with 75 μM quercetin or vehicle with or without 500 U/ml catalase for 48 hours. *, p<0.01 vs. control. C) MIA PaCa-2 and BxPC-3 cells were treated with the control vehicle, gemcitabine (G; 0.001 μg/ml), quercetin (Q; 10 μM), or gemcitabine (G; 0.001 μg/ml) and quercetin (Q; 10 μM) for 48 hours. Cell growth was assessed by cell count. Results were normalized to vehicle treated cells. *, p<0.01 vs. control; **, p<0.05 vs. control; n.s. = not significant

Figure 2

MIA PaCa-2 and BxPC-3 cells were treated with quercetin (1, 5, 10, 30, 50, and 75 μM) or control vehicle for 48 hours. Cell death was assessed by flow cytometry after Annexin/PI staining. Apoptotic cells are presented as percentage of total counted cells. *, p<0.01 vs. control; **, p<0.05 vs. control. Representative flow cytometry of MIA PaCa-2 cells treated with 10 μM quercetin or control vehicle. Apoptotic cells cluster in the lower right quadrant.

Figure 3

A) MIA PaCa-2 cells were transduced with a lentiviruses expressing firefly luciferase. Cells were serially diluted and stable light emission was confirmed by in vitro cell culture over 8 passages (passage 3 to 11) by bioluminescence after adding luciferin to the cells. B) The stability of quercetin in the mouse diet was examined by HPLC analysis. Diet was kept at room temperature for 0 to 7 days. Stability of quercetin is presented as the amount of quercetin present at the respective day in percentage of the original amount (day 0). C) Representative real-time bioluminescence imaging over time (days 4–38) of orthotopically grown pancreatic tumors in mice fed the control diet or 1% Quercetin-supplemented diet (left panel). Mean light emission over time (days 4–38) of treatment with control vehicle, quercetin (1%), gemcitabine (120 mg/kg i.p.), or quercetin (1%) and gemcitabine (120 mg/kg i.p.) (right panel). Tumor volume and tumor weight (mean ± SD; n=6 in each group) at harvest after 42 days of treatment with control vehicle, quercetin (1%), gemcitabine (120 mg/kg i.p.), or quercetin (1%) and gemcitabine (120 mg/kg i.p.)

Figure 4

(A) Representative images of BrdU staining of pancreatic tumors in mice treated with control vehicle (left) or 1% quercetin (right). Original magnification: 40x. The right panel shows the quantitative analysis of BrdU staining as number of positive cells per high power field (HPF) of pancreatic cancers in mice treated with control vehicle, gemcitabine (G; 120 mg/kg i.p.), quercetin (Q; 1%), or gemcitabine (G; 120 mg/kg i.p.) and quercetin (Q; 1%). *, p<0.05 vs. control. (B) Representative images of TUNEL staining in pancreatic tumors in mice treated with control vehicle (left) or 1% quercetin (right). Original magnification: 40x. Right panel shows the quantitative analysis of TUNEL staining as number of positive cells per high power field (HPF) of pancreatic cancers in mice treated with control vehicle, gemcitabine (G; 120 mg/kg i.p.), quercetin (Q; 1%), or gemcitabine (G; 120 mg/kg i.p.) and quercetin (Q; 1%). *, p<0.05 vs. control.