Abnormal expression of paxillin correlates with tumor progression and poor survival in patients with gastric cancer

Abstract

Background: Paxillin (PXN) has been found to be aberrantly regulated in various malignancies and involved in tumor growth and invasion. The clinicopathological and prognostic significance of PXN in gastric cancer is still unclear.

Methods: The expression of PXN was determined in paired gastric cancer tissues and adjacent normal tissues by Western blotting and real-time PCR. Immunohistochemistry was performed to detect the expression of PXN in 239 gastric cancer patients. Statistical analysis was applied to investigate the correlation between PXN expression and clinicopathological characteristics and prognosis in patients. Additionally, the effects of PXN on gastric cancer cell proliferation and migration were also evaluated.

Results: PXN was up-regulated in gastric cancer tissues and cell lines as compared with adjacent normal tissues and normal gastric epithelial cell line GES-1. Overexpression of PXN was correlated with distant metastasis (P=0.001) and advanced tumor stage (P=0.021) in gastric cancer patients. Patients with high PXN expression tended to have poor prognosis compared with patients with low PXN expression (P<0.001). Multivariate analysis demonstrated that PXN expression was an independent prognostic factor (P=0.020). Moreover, ectopic expression of PXN promotes cell proliferation and migration in AGS cells whereas knockdown of PXN inhibits cell proliferation and migration in SGC7901 cells.

Conclusions: PXN plays an important role in tumor progression and may be used as a potential prognostic indicator in gastric cancer.

Figure 1

PXN is up-regulated in gastric cancer tissues and cell lines. A, PXN protein expression levels in paired gastric cancer tissues and adjacent nontumorous tissues (n = 8). B, PXN mRNA expression levels in 30 paired gastric cancer tissues and adjacent nontumorous tissue, (P < 0.001). C, PXN protein levels in five gastric cancer cell lines and a normal gastric epithelial cell GES-1. D, PXN mRNA expression levels in gastric cancer cell lines and a normal gastric mucosa cell line GES-1.

Figure 2

IHC analyses of PXN expression in gastric cancer tissues, the representative ones are shown. A, negative staining of PXN in normal gastric mucosa; B, weak staining of PXN in well differentiated gastric cancer tissues; C, moderate staining of PXN in gastric cancer tissues; D, strong staining of PXN in gastric cancer tissues, amplification (×200)

Figure 3

The prognostic role of PXN in gastric cancer patients. Kaplan-Meier analysis of overall survival based on PXN expression in all 239 patients, patients with high PXN expression (n = 87) possessed with significantly poor overall survival compared with that of patients with low PXN expression (n = 152) (P < 0.001).

Figure 4

PXN promotes cell proliferation and colony formation in gastric cancer cells. A, PXN protein level is elevated after over-expression of PXN in AGS cells and reduced after knockdown of PXN in SGC7901 cells. B and C, Ectopic expression of PXN promotes cell proliferation in AGS cells (P = 0.017) whereas knockdown of PXN inhibits cell proliferation in SGC7901 cells as determined by MTT assays (P = 0.019). D and E, Ectopic expression of PXN stimulates colony formation in AGS cells (P = 0.026). F and G, Knockdown of PXN expression inhibits colony formation in SGC7901 cells (P = 0.011).

Figure 5

PXN promotes gastric cancer cell migration in vitro. A and B, Ectopic expression of PXN promotes cell migration in AGS cells as demonstrated by transwell assays (P = 0.013). C and D, Knockdown of PXN expression inhibits cell migration in SGC7901 cells (P = 0.032), amplification (×100).