Expression of signaling adaptor proteins predicts poor prognosis in pancreatic ductal adenocarcinoma

Abstract

Background: Adaptor proteins bridge the gap between cell surface receptors and their downstream signaling elements. The clinicopathological and prognostic values of adaptor proteins remain poorly understood. The purpose of the present study was to explore the expression and prognostic value of three adaptor proteins: GRB2-associated binding protein 2 (GAB2), CRK-like protein (CRKL) and fibroblast growth factor receptor substrate 2 (FRS2) in pancreatic ductal adenocarcinoma (PDAC).

Methods: The expression of GAB2, CRKL, and FRS2 in 77 formalin fixed paraffin embedded (FFPE) samples from 77 PDAC patients, along with three paired fresh PDAC and matched normal tissues from 3 PDAC patients was analyzed by immunohistochemistry and western blot, respectively. The association between the expression of the three proteins and the clinicopathological factors of PDAC was assessed by χ ² test. The correlation between the expression levels of the three proteins was analyzed by Spearman rank correlation analyses; Kaplan-Meier survival analyses were also performed.

Results: IHC was successful in 75, 76, and 77 cases for GAB2, CRKL, and FRS2, respectively. Of which, the positive rate of GAB2, CRKL, and FRS2 protein expression was 40.00% (30/75), 53.95% (41/76) and 35.06% (27/77), respectively. The positive rate of GAB2, CRKL and FRS2 co-expression was 16.88% (13/77). Though there was no association between GAB2 expression, CRKL expression, FRS2 expression, GAB2/CRKL/FRS2 co-expression and the clinicopathological parameters of PDAC, positive correlations were observed between the expressions of the three proteins. Further, univariate survival analysis showed that positive expression of GAB2, CRKL and FRS2 and co-expression of GAB2/CRKL/FRS2 of PDAC predicted poor clinical outcomes, and multivariate survival analysis suggested that positive expression of GAB2 and positive co-expression of GAB2/CRKL/FRS2 were independent prognostic factors for disease-free survival (DFS) and overall survival (OS), respectively.

Conclusion: In conclusion, GAB2, CRKL, and FRS2 may be potential prognosticators and therapeutic targets for PDAC patients.

Keywords: CRKL; FRS2; GAB; Pancreatic ductal adenocarcinoma; Prognosis.

Fig. 1

Expression of GAB2, CRKL and FRS2: GAB−/+ expression (a) CRKL−/+ expression (b) FRS2−/+ expression (c). Magnification × 100

Fig. 2

Western blot analyses of GAB2, CRKL and FRS2 expression in PDAC and matched normal tissues. T: PDAC tissue; N: peritumor normal tissue. β-actin was used as a loading control

Fig. 3

Correlations between GAB2 and CRKL expression, GAB2 and FRS2 expression, and CRKL and FRS2 expression in PDAC: GAB2 expression correlated with CRKL (r = 0.3742, P = 0.001) (a) GAB2 expression correlated with FRS2 (r = 0.5241, P < 0.001) (b) CRKL expression correlated with FRS2 (r = 0.2945, P = 0.0098) (c)

Fig. 4

Kaplan-Meier curves of DFS and OS with different expression patterns of GAB2, CRKL, and FRS2. DFS according to GAB2 expression pattern (P = 0.005) (a) CRKL expression pattern (P = 0.036) (b) FRS2 expression pattern (P = 0.037) (c) and GAB2/CRKL/FRS2 co-expression pattern (P = 0.015) (d). OS according to GAB2 expression pattern (P = 0.031) (e) CRKL expression pattern (P = 0.020) (f), FRS2 expression pattern (P = 0.003) (g) and GAB2/CRKL/FRS2 co-expression pattern (P = 0.001) (h)