The Wnt/β-catenin signaling pathway mechanism for pancreatic cancer chemoresistance in a three-dimensional cancer microenvironment

Abstract

β-catenin is a key protein that is encoded by the CTNNB1 gene in the Wnt signaling pathway. This study investigated the associations between β-catenin expression and implications for the efficacy of gemcitabine on pancreatic cancer cells in a three-dimensional (3-D) cancer microenvironment. For low β-catenin expression pancreatic carcinoma cells, the inhibition rates (IRs) for low, middle, and high doses of gemcitabine were 0.615 ± 0.079, 0.691 ± 0.093, and 0.765 ± 0.061, respectively. For the high β-catenin expression pancreatic carcinoma cells, the IRs for the same doses were 0.325 ± 0.072, 0.453 ± 0.075, and 0.537 ± 0.056, respectively. Additionally, the evaluation of β-catenin immunoreactivity in 31 pancreatic cancer patients revealed that the low β-catenin protein expression group had significantly longer overall survival (OS) and disease free survival (DFS) than the high β-catenin protein group (P < 0.05). Overall, β-catenin protein expression levels were significantly correlated to gemcitabine sensitivity in seven pancreatic carcinoma cell lines in the 3-D cancer microenvironment. These data suggest that large-scale clinical studies are warranted to assess the role of the Wnt/β-catenin signaling pathway on β-catenin protein expression and chemosensitivity to gemcitabine in pancreatic cancer.

Keywords: Wnt signaling pathway; chemoresistance; pancreatic carcinoma.

Figure 1

Multicellular spheroids (MCS) model designed to mimic the in-vivo microenvironment. (bars 50 um, original magnification 400 ×). A: Pancreatic cancer cell PANC-1 cultured in traditional 2-D monolayers. B: MCS model of PANC-1 cultured in 3-D culture after 7 days.

Figure 2

β-catenin protein expression in seven cell lines. β-actin was used as a loading control.

Figure 3

Optical density ratio analysis showed that β-catenin protein expression was significantly lower in cells in the Low Expression group than in cells in the High Expression group.

Figure 4

Sensitivity to three concentrations of gemcitabine in seven pancreatic cancer cell lines, showing broad variation in IRs to gemcitabine among the cell lines in the MCS model.

Figure 5

Effect of protein expression on in-vitro sensitivity to gemcitabine. The IRs at each concentration of gemcitabine tested were significantly lower in cells in the High Expression group than in cells in the Low Expression group (P < 0.05).

Figure 6

β-catenin protein immunostaining of formalin-fixed, paraffin-embedded human pancreatic cancer. Illustrative cases are shown: A: Low β-catenin Expression; B: High β-catenin Expression.

Figure 7

Kaplan-Meier analysis of OS and DFS found that the Low Expression group had longer OS and DFS than the High Expression group.