Identification of ANXA1 as a Lymphatic Metastasis and Poor Prognostic Factor in Pancreatic Ductal Adenocarcinoma

Objective: The aim of this study was to investigate the clinical significance of annexin a1 (ANXA1) andprovide molecular evidence to support that decreased ANXA1 expression could enhance cancer migration andinvasion in pancreatic ductal adenocarcinoma (PDAC). Materials and
Methods: Immunohistochemistry of atissue microarray with 162 surgically resected PDAC specimens was performed to examine the expression ofANXA1. We also investigated the relationship between ANXA1 expression and clinicopathological factors andprognosis of PDAC patients. We further studied the role of ANXA1 in PDAC cell proliferation, migration andinvasion by cell proliferation assay, migration assay and matrigel invasion assay with reduced ANXA1 expressionby RNAi. Western blotting was used to detect matrix metalloproteinase-9 (MMP-9), and tissue inhibitor ofmetalloproteinase-1 (TIMP-1) expression. We also detected MMP-9 enzyme activity by gelatin zymography.
Results: Decreased expression of ANXA1 was significantly associated with poor differentiation, lymph nodemetastasis and advanced TNM stage of PDAC patients (p<0.05). Moreover, decreased expression of ANXA1was correlated with poor survival (p<0.05). Furthermore, we found that ANXA1 knockdown inhibited cellproliferation, induced G1 phase cell cycle arrest, increased PDAC cell migration and invasion capacity comparedwith controls. In addition, Western blotting showed that ANXA1 knockdown increased the MMP-9 proteinlevel and decreased TIMP-1 expression. Gelatin zymography showed that MMP-9 enzyme activity was alsoelevated.
Conclusions: Negative ANXA1 expression is a most unfavorable prognostic factor for PDAC patients.ANXA1 knockdown inhibits cell proliferation by inducing G1 phase cell cycle arrest and increases migrationand invasion of PDAC cells through up-regulating MMP-9 expression and activity, implying that ANXA1 mayserve as a promising prognostic biomarker and therapeutic target for PDAC.