Inhibitory effect of cucurbitacin E on pancreatic cancer cells growth via STAT3 signaling

Abstract

Purpose: Pancreatic cancer has been a serious disease worldwide for its high mortality. Cucurbitacin E is a member of triterpenoid family isolated from plants showing antiproliferative activity on various cancer cells. In this study, we have explored whether cucurbitacin E also has an anti-tumor effect on pancreatic cancer cells.

Methods: Human pancreatic cancer cells PANC-1 were used to explore the effect and possible mechanisms of cucurbitacin E on cell cycle progression, apoptosis and proliferation.

Results: Cucurbitacin E has inhibited the growth of PANC-1 cells in a dose- and time-dependent manner, and has caused accumulation of cells at the G(2)/M phase as well as apoptosis. Western blotting also showed that cucurbitacin E treatment can inhibit STAT3 phosphorylation while upregulate p53 expression.

Conclusions: Our results suggested that cucurbitacin E may be an effective regimen for the chemotherapy of pancreatic cancer.

Fig. 1

Dose- and time-dependent effect of CuE on the viability of PANC-1 cells. PANC-1 cells at 5 × 10³ cells/well were cultured in RPMI 1640–10% FBS with CuE (0.01, 0.1, 1, 10 and 100 μM) for 24, 48 and 72 h. Cell viability was determined daily with a MTT assay

Fig. 2

Effect of CuE on cell cycle distribution. (a) PANC-1 cells (1 × 10⁶) were treated with 1 μM of CuE and analyzed at (a) 0, (b) 12 and (c) 24 h by DNA flow cytometry. (b) PANC-1 cells (1 × 10⁶) were treated with 0, 0.1, 1 μM of CuE and analyzed at 24 h by DNA flow cytometry. * P<0.05 compared with control

Fig. 3

Apoptosis shown by Hoechst 33258 staining (400×). (a) PANC-1 cells treated with (a) 0, (b) 0.01, (c) 0.1 and (d) 1 μM of CuE for 24 h. (b) PANC-1 cells treated with 1 μM of CuE for (a) 0, (b) 12 and (c) 24 h

Fig. 4

Apoptosis measured by Annexin V-FITC/PI staining. PANC-1 cells were treated with 0, 0.1, 1 and 10 μM of CuE for 24 h, stained with Annexin V-FITC and PI, and analyzed with flow cytometry. The horizontal and vertical axes represent labeling with Annexin V-FITC and PI, respectively. LR represents early apoptotic cells (positive for Annexin V only), UR represents late apoptotic cells (positive for both Annexin V and PI), LL represents live cells

Fig. 5

Western blot analysis of p-STAT3 and p53 proteins. PANC-1 cells were treated with 0, 0.01, 0.1, 1 and 10 μM of CuE for 24 h. Cells were then harvested and processed for western blotting as described in “Material and methods”. β-actin was used as the internal control