Association of RAB5 overexpression in pancreatic cancer with cancer progression and poor prognosis via E-cadherin suppression

Abstract

Pancreatic cancer is a common type of cancer with poor prognosis worldwide. Postoperative survival depends on the existence of metastasis. Elucidation of the mechanism underlying cancer progression is important to improve prognosis. The RAS-associated protein RAB5 activates intracellular membrane trafficking, and RAB5 expression is correlated to progression and epithelial mesenchymal transition in various cancers.The expression of RAB5 and E-cadherin in 111 pancreatic cancer samples was investigated by immunohistochemical staining, and the relationship among RAB5 expression, clinicopathological factors, and E-cadherin expression was assessed. Furthermore, RAB5 suppression analysis by siRNA was performed to determine the roles of RAB5 in morphological change, proliferation potency, cell migration ability, and invasiveness of the pancreatic cancer cell line.High RAB5 expression correlated with the presence of lymphatic invasion and venous invasion and low E-cadherin expression. Patients with high RAB5 expression had a poorer prognosis than those with low RAB5 expression. RAB5 suppression in pancreatic cancer cells enhanced E-cadherin expression; changed cell morphology from spindle to round; and inhibited proliferation, invasion, and cell migration.RAB5 contributes to poor prognosis and progression in pancreatic cancer patients. It may be a promising candidate for individualized therapy in refractory pancreatic cancer.

Keywords: E-cadherin; RAB5; cancer progression; epithelial mesenchymal transition; pancreatic cancer.

Figure 1. Immunohistochemical staining of RAB5 and E-cadherin in primary pancreatic cancer samples

A. Examples of high and low RAB5 expression in primary pancreatic cancer specimens (200×). B. An example of high RAB5 expression and low E-cadherin expression in a primary pancreatic cancer specimen (400×). Arrowhead, normal acinar cells; arrow, atypical ducts. C. Fluorescence immunohistochemical analysis of RAB5 and E-cadherin expression in a representative pancreatic cancer tissue (400×).

Figure 2. Relationships between postoperative survival and RAB5 and E-cadherin expression

A, B. Overall survival and cancer-specific survival of pancreatic cancer patients according to RAB5 expression (P = 0.041, P = 0.084).

Figure 3. Functional analysis of RAB5 by small-interfering RNA (siRNA)

A. RAB5 protein levels were measured by western blotting for pancreatic cancer cell lines. B. RAB5 expression in RAB5 siRNA-transfected and untreated SUIT-2 cells assessed by western blotting. C. RAB5, E-cadherin, and N-cadherin mRNA expression in RAB5 siRNA-transfected and untreated SUIT-2 cells assessed by RT–qPCR (*P < 0.05). D. Proliferation assay in RAB5 siRNA-transfected and untreated SUIT-2 cells assessed by the Cell Counting Kit-8 assay (*P < 0.05). Si: siRNA.

Figure 4. Invasion and migration assays of SUIT-2 cells treated by RAB5 siRNA

A. Invasion assay of RAB5 siRNA-transfected and untreated SUIT-2 cells (*P < 0.05). B. Wound healing assay of RAB5 siRNA-transfected and untreated SUIT-2 cells (*P < 0.05). Si: siRNA.