Higher autocrine motility factor/glucose-6-phosphate isomerase expression is associated with tumorigenesis and poorer prognosis in gastric cancer

Abstract

Background: Glucose-6-phosphate isomerase (GPI) is a glycolytic-related enzyme that inter-converts glucose-6-phosphate and fructose-6-phosphate in the cytoplasm. This protein is also secreted into the extracellular matrix by cancer cells and is, therefore, also called autocrine motility factor (AMF).

Methods: To clarify the roles of AMF/GPI in gastric cancer (GC), we collected 335 GC tissues and the corresponding adjacent noncancerous tissues, performed immunohistochemical studies, and analyzed the relationship between AMF/GPI expression and the patients' clinicopathologic features.

Results: AMF/GPI expression was found to be significantly higher in the GC group than in the corresponding noncancerous tissue group (P<0.001). Additionally, AMF/GPI expression positively associated with a higher TNM stage and poorer prognosis in patients. Through Kaplan-Meier analysis and according to the Oncomine database, we found that AMF/GPI was overexpressed in GC tissues compared to normal mucosa, and the patients with higher AMF/GPI expression had poorer outcomes. We used AMF/GPI-silenced GC cell lines to observe how changes in AMP/GPI affect cellular phenotypes. AMF/GPI knockdown suppressed proliferation, migration, invasion, and glycolysis, and induced apoptosis in GC cells.

Conclusion: These findings suggest that AMF/GPI overexpression is involved in carcinogenesis and promotes the aggressive phenotypes of GC cells.

Keywords: autocrine motility factor; gastric cancer; glucose-6-phosphate isomerase; metabolism; prognosis; tumorigenesis.

Figure 1

AMF/GPI expression in primary GC tissues and the survival in patients with GC. Notes: (A) Expression of AMF/GPI detected by immunohistochemical staining. (B) Kaplan–Meier survival curves of overall survival in all 335 patients of AMF/GPI negative vs AMF/GPI positive. Abbreviations: AMF, autocrine motility factor; GC, gastric cancer; GPI, glucose-6-phosphate isomerase.

Figure 2

Effects of AMF/GPI knockdown in GC cell growth and proliferation in vitro and in vivo. Notes: (A) AMF/GPI expression confirmed by Western blotting. Lane 1, wild type; lane 2, scrambled shControl; lane 3, shAMF/GPI. (B) Cell proliferation measured by MTT assay. (C) Tumor growth curve of shControl and shAMF/GPI cells. (D) Pictures show tumor formation in nude mice injected with shControl and shAMF/GPI cells. (E) H&E and Ki-67 stainings of xenograft tumor tissues. Magnification: ×100. The data are shown as mean±SD. ^*p<0.05, ^**p<0.01, ^***p<0.001. Abbreviations: AMF, autocrine motility factor; GC, gastric cancer; GPI, glucose-6-phosphate isomerase.

Figure 3

AMF/GPI expression is related to G2/M arrest and apoptosis of GC cells. Notes: (A) GC cell cycle analysis by flow cytometry. (B) Effects of AMF/GPI knockdown in GC cell apoptosis. Bars, mean±SD of three independent experiments.^*p<0.05, ^**p<0.01, ^***p<0.001. Abbreviations: AMF, autocrine motility factor; GC, gastric cancer; GPI, glucose-6-phosphate isomerase; WT, wild type.

Figure 4

Effects of AMF/GPI knockdown in GC cell invasion and migration. Notes: Transwell assay of WT, shControl, and shAMF/GPI GC cells. Magnification: ×200. Abbreviations: AMF, autocrine motility factor; GC, gastric cancer; GPI, glucose-6-phosphate isomerase; WT, wild type.

Figure 5

Effects of AMF/GPI knockdown on metabolism in GC cells. Notes: (A) OCR of shControl and shAMF/GPI cells. (B) ECAR of shControl and shAMF/GPI cells. Abbreviations: AMF, autocrine motility factor; ECAR, extracellular acidification rates; GC, gastric cancer; GPI, glucose-6-phosphate isomerase; OCR, oxygen consumption rates; WT, wild type.