Proteomics-based identification of the tumor suppressor role of aminoacylase 1 in hepatocellular carcinoma
Introduction
Hepatocellular carcinoma (HCC) is the sixth most common neoplasm and the third most common cause of cancer mortality worldwide [1]. The major risk factors for developing HCC are infection with hepatitis B and C viruses and the intake of aflatoxin and alcohol [2]. The early diagnosis of HCC is very difficult because its signs and symptoms are not apparent until the disease advances. Surgical resection is the preferred treatment strategy for patients with HCC. Other treatments, such as transarterial chemoembolization, radiofrequency ablation, radiation therapy, and liver transplantation, have also been used in patients when excision is difficult [3]. However, the prognosis of patients with HCC is generally poor because of extensive liver metastasis and recurrence. Therefore, further understanding the molecular mechanisms of HCC development is extremely important to prevent the disease and design better treatments.
Proteomics, a powerful tool to help the diagnosis and treatment of diseases, has played an important role in cancer research in recent decades [4]. A proteomic approach revealed that talin-1 was significantly associated with the dedifferentiation of HCC and tumor recurrence after resection [5]. Other biomarkers identified using proteomic analysis, such as heat shock protein 27 (HSP27), mortalin, and apolipoprotein E, were useful in the prediction of HCC prognosis [6], [7], [8]. Their analysis revealed a different profile of new biomarkers associated with HCC development, progression, recurrence, and metastasis via comparative proteomic analysis.
The present study aimed to investigate the expression of aminoacylase 1 (ACY1) in hepatocellular carcinoma (HCC) tissues via a proteomic profile analysis. A quantitative proteomic study that focused on HCC and matched paracarcinoma tissues using two-dimensional difference gel electrophoresis (2D-DIGE) was performed. Interestingly, ACY1, which was expressed at lower levels in HCC with portal vein tumor thrombus (PVTT) than HCC without PVTT in our previous proteomic study [9], was found to be expressed at lower levels in HCC tissues than paracarcinoma tissues. The expression of ACY1 was further verified with additional samples. The relationship between the ACY1 expression level in HCC and clinical pathological features was also evaluated. Furthermore, the role of ACY1 in HCC progression was explored using cell proliferation, apoptosis, cell cycle, and invasion assays in vitro using the HCC cell lines SMMC7721 and BEL7402.
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Clinical materials and sample preparation
All clinical samples used in this study were obtained from patients with HCC who underwent a hepatectomy at the first affiliated hospital, College of Medicine, Zhejiang University between the years 2010 and 2012. Among the 131 pairs of HCC tissues and paracarcinoma tissues, 3 pairs were used for proteomic profiling, and the other 128 pairs of HCC tissues and paracarcinoma tissues were used for further verification. This study was performed per the protocols approved by the Ethical Committee at
2D-DIGE and mass spectrometry
Six spots were found to be upregulated in the HCC tissues, while 24 spots were found to be upregulated in the matched paracarcinoma tissues (Fig. 1A). Of these spots, 11 protein spots with expression changes greater than 2.5-fold were isolated and analyzed (Table 1). ACY1 changed 4.1-fold, which was the largest change among the proteins.
ACY1 expression was significantly decreased in HCC tissues
The mRNA expression of ACY1 was lower in HCC tissues than in paracarcinoma tissues (p < 0.05, Fig. 1B). Western-blot analysis confirmed that the ACY1 protein
Discussion
Currently, the pathogenesis of HCC remains unclear. In this study, 11 differentially expressed proteins were identified via the comparative proteomic profiling of HCC tissues and matched paracarcinoma tissues. Some of these differentially expressed proteins play key roles in tumorigenesis and progression [11], and understanding these roles could provide more information on HCC. For instance, the modulation of keratin 8 expression can influence the phenotype of epithelial cancer cells and
Conflict of Interest
None.
Acknowledgments
This work was supported by the “Program for New Century Excellent Talents in University” of the Ministry of Education, National High-tech R&D Program of China (863 Program) (No. 2012AA020204), the National Science and Technology Major Projects (No. 2012ZX10002010-001-005), and the National Natural Science Foundation of China (Grant No. 81372625).
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