OBJECTIVETo study the relationship and clinicopathological significance of Numb,MDM2 and p53 expression in human pancreatic cancer.

METHODSThe expression of Numb,MDM2 and p53 proteins in 65 cases of paired paraffin embedded pancreatic ductal adenocarcinoma (PDAC) specimens and adjacent non-cancerous pancreas was detected by immunohistochemistry (IHC). The relationship among their expression and clinicopathological characters was analyzed.Westem blot was used to examine their expression in 16 paired fresh PDAC specimens and adjacent non-cancerous pancreatic tissues. Meanwhile,Numb expression in Capan-2, PANC-1 and AsPC-1 pancreatic cancer cells with different differentiation were detected by immunofluorescence (IF) , Westem blot and quantitative real-time (qRT) -PCR, respectively. Paired sample t-test, χ(2) test, Kaplan-Meier and Cox regression were used to analyze the results of our experiments, respectively.

RESULTSIHC showed that there was no differential expression of Numb in PDAC and adjacent pancreas (t = 1.746, P = 0.086) , while the expression of MDM2 and p53 was significantly increased in PDAC, compared to that in paired normal pancreas (t = 3.294, P = 0.002; t = 3.152, P = 0.002, respectively) .Numb expression was negatively associated with tumor size (χ² = 5.206, P = 0.023), differentiation (χ² = 7.802, P = 0.005) and UICC stage (χ² = 4.770, P = 0.029), while expression of MDM2 and p53 was positively associated with tumor T and TNM stage, respectively (χ² = 5.182, P = 0.023; χ² = 6.448, P = 0.011) . Correlation analysis showed a negative association between Numb and MDM2 (r = -0.283, P = 0.023) , but there was no relationship of them with p53 (P > 0.05) .Univariate and multivariate analysis revealed that Numb was a protective prognostic indicator for patients with PDAC (χ² = 5.408, P = 0.020). Moreover, patients with Numb positive and MDM2 negative expression had a significantly better overall survival (χ² = 5.868, P = 0.015). Western blot showed that Numb expression was much higher in well differentiated PDAC than that in paired normal pancreas (t = 1.092, P = 0.020) , while the expression of MDM2 and p53 was significantly increased in 16 cases of PDAC (t = 3.263, P = 0.005; t = 3.607, P = 0.003, respectively). Numb expression was gradually increased in pancreatic cancer cells with the increasing degree of cell differentiation detected by IF, Westem blot and qRT-PCR.

CONCLUSIONSNumb acts as a tumor suppressor gene in the development of PDAC. Numb, MDM2 and p53 might coordinately participate in the development of PDAC.