Retrospective Study
Copyright ©The Author(s) 2015. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Jun 7, 2015; 21(21): 6649-6659
Published online Jun 7, 2015. doi: 10.3748/wjg.v21.i21.6649
Neuron-glial antigen 2 overexpression in hepatocellular carcinoma predicts poor prognosis
Le-Le Lu, Jing Sun, Jie-Juan Lai, Yan Jiang, Lian-Hua Bai, Lei-Da Zhang
Le-Le Lu, Jing Sun, Jie-Juan Lai, Yan Jiang, Lian-Hua Bai, Lei-Da Zhang, Department of Hepatobiliary Surgery, Southwest Hospital, Third Military Medical University, Chongqing 400038, China
Author contributions: Lu LL and Sun J contributed equally to this work; Lu LL and Sun J performed the majority of experiments and wrote the manuscript; Lai JJ and Jiang Y provided vital reagents and analytical tools and were also involved in editing the manuscript; Bai LH and Zhang LD co-ordinated and provided the collection of all the human material in addition to designing the study and providing financial support for this work.
Supported by National Natural Science Foundation of China, No. 81170425 and No. 81071979; Hepatobiliary Surgery Department of the Southwest Hospital (Chongqing, China); and Third Military Medical University (Chongqing, China).
Ethics approval: All tissue samples were collected from hepatocellular carcinoma patients who underwent a hepatectomy at the Department of Hepatobiliary Surgery between January and December 2007, according to protocols approved by the Medical Ethics Committee of the Southwest Hospital and the First Affiliated Hospital of the Third Military Medical University.
Informed consent: All patients provided written informed consent to use tumor tissue for clinical research.
Conflict-of-interest: No conflict of interest exits in the submission of this manuscript, and the manuscript is approved by all authors for publication.
Data sharing: Participants gave informed consent for data sharing.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Lei-Da Zhang, MD, PhD, Department of Hepatobiliary Surgery, Southwest Hospital, Third Military Medical University, Shapingba No. 30 Gaotanyan Street, Chongqing 400038, China. 649624279@qq.com
Telephone: +86-23-68765810 Fax: +86-23-68765810
Received: September 1, 2014
Peer-review started: September 5, 2014
First decision: October 14, 2014
Revised: December 30, 2014
Accepted: January 16, 2015
Article in press: January 16, 2015
Published online: June 7, 2015
Abstract

AIM: To investigate whether neuron-glial antigen 2 (NG2) could be an effective prognostic marker in hepatocellular carcinoma (HCC).

METHODS: NG2 expression was semi-quantitatively scored from the immunohistochemistry (IHC) data based on the number of positive cells and the staining intensity. A total of 132 HCC specimens and 96 adjacent noncancerous tissue samples were analyzed by IHC for NG2 protein expression. To confirm the NG2 expression levels observed by IHC, we measured NG2 expression in 30 randomly selected tumor and adjacent noncancerous tissue samples by quantitative real-time polymerase chain reaction and Western blot. The correlations between NG2 protein expression and the clinicopathological features of HCC patients were analyzed using the χ2 test. To assess the prognostic value of NG2 for HCC, the association between NG2 expression and survival was analyzed using the Kaplan-Meier method with the log-rank test. To further evaluate the prognostic value of NG2 expression, a Cox multivariate proportional hazards regression analysis was performed with all the variables to derive risk estimates related to disease-free and overall survival and to control for confounders.

RESULTS: High NG2 expression was observed in significantly more primary tumor samples (63.6%; 84/132) compared with the adjacent noncancerous tissue samples (28.1%; 27/96) (P < 0.0001). Moreover, high NG2 protein expression was closely associated with tumor differentiation (χ2 = 9.436, P = 0.0089), recurrence (χ2 = 5.769, P = 0.0163), tumor-node-metastasis (TNM) stage (χ2 = 8.976, P = 0.0027), and invasion (χ2 = 5.476, P = 0.0193). However, no significant relationship was observed between NG2 protein expression in HCC and other parameters, such as age, sex, tumor size, serum alpha fetoprotein (AFP), tumor number, or tumor capsule. The log-rank test indicated a significant difference in the overall survival of HCC patients with high NG2 expression compared with those with low NG2 expression (29.2% vs 9.5%, P < 0.001). Moreover, NG2 expression in HCC tissue significantly correlated with disease-free survival (15.2% vs 6.7%, P < 0.001). Multivariate analysis showed that NG2 expression (HR = 2.035, P = 0.002), serum AFP (HR = 1.903, P = 0.003), TNM stage (HR = 2.039, P = 0.001), and portal vein invasion (HR = 1.938, P = 0.002) were independent prognostic indicators for OS in HCC patients. Furthermore, NG2 expression (HR = 1.974, P = 0.003), serum AFP (HR = 1.767, P = 0.008), TNM stage (HR = 2.078, P = 0.001), tumor capsule (HR = 0.652, P = 0.045), and portal vein invasion (HR = 1.941, P = 0.002) were independent prognostic indicators for DFS in HCC patients.

CONCLUSION: The up-regulation of NG2 is associated with poor prognosis in HCC. Therefore, NG2 could be useful as an additional prognostic marker to increase the resolution of traditional approaches.

Keywords: Neuron-glial antigen 2, Hepatocellular carcinoma, Survival analysis, Poor prognosis, Prognostic marker

Core tip: To help predict which patients have an unfavorable prognosis, it is critical to identify a dependable prognostic biomarker that correlates with hepatocellular carcinoma (HCC) progression, invasion, metastasis and recurrence. Despite recent evidence showing that neuron-glial antigen 2 (NG2) is expressed on the surface of differentiated malignant cells, progenitor cells, and cancer stem cells in various tumors and promotes the growth and metastasis of melanoma cells, whether it is associated with HCC progression remains elusive. The results of the present study showed that NG2 is useful as an additional prognostic marker to increase the resolution of current approaches.