Over-expression of BCAT1, a c-Myc target gene, induces cell proliferation, migration and invasion in nasopharyngeal carcinoma

Molecular Cancer, Jun 2013

Background Nasopharyngeal carcinoma (NPC) is a common malignant tumor in southern China and Southeast Asia, but its molecular mechanisms of pathogenesis are poorly understood. Our previous work has demonstrated that BCAT1 mRNA is over expressed in NPC and knocking down its expression in 5-8F NPC cell line can potently inhibit cell cycle progression and cell proliferation. However, the mechanism of BCAT1 up-regulation and its functional role in NPC development remain to be elucidated yet. Methods Immunohistochemistry (IHC) method was utilized to detect the expression of BCAT1 protein in NPC at different pathological stages. The roles of gene mutation, DNA amplification and transcription factor c-Myc in regulating BCAT1 expression were analyzed using PCR-sequencing, quantitative polymerase chain reaction (qPCR), IHC, ChIP and luciferase reporter system, respectively. The functions of BCAT1 in colony formation, cell migration and invasion properties were evaluated by RNA interference (RNAi). Results The positive rates of BCAT1 protein expression in normal epithelia, low-to-moderate grade atypical hyperplasia tissues, high-grade atypical hyperplasia tissues and NPC tissues were 23.6% (17/72), 75% (18/24 ), 88.9% (8/9) and 88.8% (71/80), respectively. Only one SNP site in exon1 was detected, and 42.4% (12/28) of the NPC tissues displayed the amplification of microsatellite loci in BCAT1. C-Myc could directly bind to the c-Myc binding site in promoter region of BCAT1 and up-regulate its expression. The mRNA and protein of c-Myc and BCAT1 were co-expressed in 53.6% (15/28) and 59.1% (13/22) of NPC tissues, respectively, and BCAT1 mRNA expression was also down-regulated in c-Myc knockdown cell lines. In addition, BCAT1 knockdown cells demonstrated reduced proliferation and decreased cell migration and invasion abilities. Conclusions Our study indicates that gene amplification and c-Myc up-regulation are responsible for BCAT1 overexpression in primary NPC, and overexpression of BCAT1 induces cell proliferation, migration and invasion. The results suggest that BCAT1 may be a novel molecular target for the diagnosis and treatment of NPC.

A PDF file should load here. If you do not see its contents the file may be temporarily unavailable at the journal website or you do not have a PDF plug-in installed and enabled in your browser.

Alternatively, you can download the file locally and open with any standalone PDF reader:

http://www.molecular-cancer.com/content/pdf/1476-4598-12-53.pdf

Over-expression of BCAT1, a c-Myc target gene, induces cell proliferation, migration and invasion in nasopharyngeal carcinoma

Molecular Cancer Over-expression of BCAT1, a c-Myc target gene, induces cell proliferation, migration and invasion in nasopharyngeal carcinoma Wen Zhou 0 Xiangling Feng 0 Caiping Ren 0 Xingjun Jiang Weidong Liu 0 Wei Huang 0 Zhihong Liu Zan Li Liang Zeng Lei Wang 0 Bin Zhu 0 Jia Shi 0 Jie Liu 0 Chang Zhang 0 Yanyu Liu 0 Kaitai Yao 0 0 Cancer Research Institute, Xiang-Ya School of Medicine, Key Laboratory for Carcinogenesis of Chinese Ministry of Health, Key Laboratory for Carcinogenesis & Cancer Invasion of Chinese Ministry of Education, Central South University , Xiangya Road 110, 410078, Changsha, Hunan , P. R. China Background: Nasopharyngeal carcinoma (NPC) is a common malignant tumor in southern China and Southeast Asia, but its molecular mechanisms of pathogenesis are poorly understood. Our previous work has demonstrated that BCAT1 mRNA is over expressed in NPC and knocking down its expression in 5-8F NPC cell line can potently inhibit cell cycle progression and cell proliferation. However, the mechanism of BCAT1 up-regulation and its functional role in NPC development remain to be elucidated yet. Methods: Immunohistochemistry (IHC) method was utilized to detect the expression of BCAT1 protein in NPC at different pathological stages. The roles of gene mutation, DNA amplification and transcription factor c-Myc in regulating BCAT1 expression were analyzed using PCR-sequencing, quantitative polymerase chain reaction (qPCR), IHC, ChIP and luciferase reporter system, respectively. The functions of BCAT1 in colony formation, cell migration and invasion properties were evaluated by RNA interference (RNAi). Results: The positive rates of BCAT1 protein expression in normal epithelia, low-to-moderate grade atypical hyperplasia tissues, high-grade atypical hyperplasia tissues and NPC tissues were 23.6% (17/72), 75% (18/24 ), 88.9% (8/9) and 88.8% (71/80), respectively. Only one SNP site in exon1 was detected, and 42.4% (12/28) of the NPC tissues displayed the amplification of microsatellite loci in BCAT1. C-Myc could directly bind to the c-Myc binding site in promoter region of BCAT1 and up-regulate its expression. The mRNA and protein of c-Myc and BCAT1 were co-expressed in 53.6% (15/28) and 59.1% (13/22) of NPC tissues, respectively, and BCAT1 mRNA expression was also down-regulated in c-Myc knockdown cell lines. In addition, BCAT1 knockdown cells demonstrated reduced proliferation and decreased cell migration and invasion abilities. Conclusions: Our study indicates that gene amplification and c-Myc up-regulation are responsible for BCAT1 overexpression in primary NPC, and overexpression of BCAT1 induces cell proliferation, migration and invasion. The results suggest that BCAT1 may be a novel molecular target for the diagnosis and treatment of NPC. Nasopharyngeal carcinoma; BCAT1; c-Myc; Proliferation; Migration; Invasion; Gene amplification; Gene regulation - Background Nasopharyngeal carcinoma (NPC) is a squamous cell carcinoma that develops from the epithelium of the nasopharynx with a high incidence in Southeast Asia and southern China and causes a serious healthcare problem in these regions [1]. More than 95% of NPC in southern China is undifferentiated carcinoma with a high incidence of early metastasis which is the main cause of death in NPC patients. Currently, radiation therapy is the first choice for NPC treatment. Although the radiotherapy equipments and techniques have been improved tremendously, the five-year survival rate of NPC patients has not radically changed yet and remains around 50-60%. Therefore, it is of great importance to comprehensively explore the new approaches for NPC treatment. The molecular mechanisms of nasopharyngeal carcinogenesis have not been elucidated clearly yet. Previous studies have shown that proto-oncogenes (e.g. HRAS, NRAS2 [2], cyclin D1 [3], MDM2 [4], EVI1 [5], EGFR [6]) and tumor suppressor genes (TSGs) (e.g. p53 [7], p16 [8], RASSF1A [9], DLC-1 [10], LTF [11,12], DLEC1 [13], TSLC1 [14]) are aberrantly expressed in NPC. However, none of them has been confirmed as an NPC-specific oncogene or TSG. Using comparative genomic hybridization (CGH) data from 170 primary NPC cases, we have developed a tree model indicating the pathogenetic mechanisms of NPC [15]. According to the tree model, +12p11-12 may represent an early event in the carcinogenesis of NPC [15]. We further identified that BCAT1, KCNJ8, PTX1 and KRAS2, four genes located at 12p11-12, were significantly up-regulated in NPC tissues compared to the normal controls [16]. BCAT1 (branched chain aminotransferase 1 gene, also known as ECA39) is also significantly up-regulated in Burkitts lymphoma and breast cancer [17]. Therefore, we selected BCAT1 as a target gene for further study to explore its relationship with NPC development. In our previous work, we found that BCAT1 mRNA expression was over expressed in NPC tissues, and BCAT1 knockdown in 5-8F NPC cell line inhibited cell cycle progression and cel (...truncated)


This is a preview of a remote PDF: http://www.molecular-cancer.com/content/pdf/1476-4598-12-53.pdf

Wen Zhou, Xiangling Feng, Caiping Ren, Xingjun Jiang, Weidong Liu, Wei Huang, Zhihong Liu, Zan Li, Liang Zeng, Lei Wang, Bin Zhu, Jia Shi, Jie Liu, Chang Zhang, Yanyu Liu, Kaitai Yao. Over-expression of BCAT1, a c-Myc target gene, induces cell proliferation, migration and invasion in nasopharyngeal carcinoma, Molecular Cancer, 2013, pp. 53, 12, DOI: 10.1186/1476-4598-12-53