br Introduction br Gastric cancer as one of
Gastric cancer, as one of the most common malignancies and the second leading cause of cancer-related deaths worldwide, imposes a considerable global health burden (Van Cutsem et al., 2016; Gores and Lieberman, 2016; Ajani et al., 2017). Although the screening strategies for early detection are continually improved in Japan and South Korea, they are either not implemented or not feasible in most of the world, leading to late diagnosis and poor overall 5-year survival in most pa-tients (Ajani et al., 2017; Siegel et al., 2013; Ferlay et al., 2015; Shridhar et al., 2013). Therefore, it is essential to identify sensitive biomarkers and explore novel therapeutic targets to improve the sur-vival rate of GC patients.
Metabolic reprogramming is considered a hallmark of cancer, and has been an area of accelerated research over the last decade (Hanahan and Weinberg, 2011; Boroughs and DeBerardinis, 2015). Cancer P 22077 acquire characteristic changes in glucose metabolism to support their unrestricted proliferation and metastasis (Jin et al., 2007; Pavlova and Thompson, 2016). Enolase, also known as pyruvate dehydrogenase, is a key glycolytic enzyme that catalyzes the dehydration of 2-phospho-D-
glycerate to phosphoenolpyruvate, which generates ATP during glyco-lysis to support cancer cell proliferation and metastasis (Vander Heiden et al., 2009). ENO1, as one of three enolase subunits, has been shown to play a pivotal role in tumorigenesis and cancer metastasis (Capello et al., 2011). ENO1 is proposed as a candidate oncogene and its over-expression has been detected in several types of cancers (Cappello et al., 2009; Song et al., 2014; Tsai et al., 2010; Shih et al., 2010; Zhan et al., 2017), such as pancreatic cancer, glioma, head and neck cancer, breast cancer and colorectal cancer. However, there are bifunctional roles of ENO1 in endometrial carcinoma, non-small cell lung cancer and clear cell renal cell carcinoma (Zhao et al., 2015; Fu et al., 2015; White-Al Habeeb et al., 2015). Recent studies showed that ENO1 was highly expressed in GC tissues compared to non-tumor tissues and its over-expression enhanced GC cell proliferation and drug resistance to cis-platin (Qian et al., 2017; Qiao et al., 2018; Liu et al., 2015). These data suggest that over-expressed ENO1 contributes to the development and progression of GC, but the precise function and internal mechanisms of ENO1 in GC cell proliferation and metastasis remains to be further explored.
Herein, we first detected the expression of ENO1 in GC tissues and
Correspondence to: Department of General Surgery, the First Aﬃliated Hospital of Soochow University, 188 ShiZi Street, Suzhou 215006, China.
E-mail addresses: [email protected] (X. Zhu), [email protected] (S. He). 1 These authors contributed equally to this work.
paired non-tumor tissues, and then investigated the eﬀects of ENO1 on GC cell proliferation and metastasis in vitro. We also examined its eﬀect on the regulation of AKT signaling pathway, which plays a central role in modulating tumor cell proliferation and metastasis (Liang and Slingerland, 2003; Gonzalez and Medici, 2014). Our studies demon-strate that ENO1 functions as a novel regulator for AKT signaling pathway to mediate GC cell proliferation and metastasis, which reveals a possible implication for new approaches to GC therapy.
2. Materials and methods
2.1. GC tissues and cell lines
Human GC tissues and surrounding normal tissues were collected from patients who were treated from 2016 to 2018 at the Department of General Surgery, the First Aﬃliated Hospital of Soochow University. The study was approved by the First Aﬃliated Hospital of Soochow University Ethics Committee and all of the patients provided informed consent.
The human GC cell lines (AGS and SGC7901) were purchased from the Cell Bank of the Chinese Academy of Sciences (Shanghai, China) and were cultured in Roswell Park Memorial Institute (RPMI) medium (Hyclone) containing 10% Fetal Bovine Serum (Gibco), 100 units/ml penicillin G sodium and 100 µg/ml streptomycin sulfate (Gibco). All GC cells were maintained at 37 °C in a humidified atmosphere containing 5% CO2.
2.2. Immunohistochemistry (IHC)
Briefly, the slides were incubated with the antibody recognizing human ENO1 at 1:200 dilution at 4 °C overnight. A tissue staining kit (Zhongshan Biotechnology, Beijing, China) was used to visualize the protein and the final staining score was determined by color intensity and positive cell rate, which is described in our previous study (Sun et al., 2018a, 2018b; Lu et al., 2018). An average intensity score of 5 or above was taken as high expression and a score below 5 as none or low expression.