Overexpression Of B-cell Translocation Gene 2 Research Articles

BTG2 suppresses the growth and metastasis of cervical squamous cell carcinoma

BackgroundCervical cancer is the fourth most common malignancy in women, of which cervical squamous cell carcinoma (CESC) is the main pathological type of cervical cancer. B-cell translocation gene 2 (BTG2) protein has been recognized as a tumor suppressor in several cancer types. However, BTG2 expression and molecular function in CESC are unknown. MethodsIn this study, we first assessed the expression of BTG2 in tumor tissue specimens from CESC patients using immunohistochemical staining and real-time quantitative PCR, and explored the relationship between BTG2 expression status and clinical manifestations. Next, we constructed BTG2 knockdown and overexpression CESC cell lines to observe the effects of BTG2 on CESC proliferation and metastasis at the cellular level. Finally, we employed a nude mouse xenograft tumor model in an in vivo experiment to observe the effect of BTG2 on tumorigenesis in vivo. ResultsThe results showed that the expression of BTG2 protein was lower in CESC tissues than in normal tissues, and high BTG2 expression was associated with better survival in CESC patients versus CESC patients. The results of cellular assays confirm that overexpression of BTG2 inhibits the proliferation, migration and metastasis of CESC cells. Nude mouse xenograft tumor model showed that overexpression of BTG2 inhibited tumor growth in vivo, and conversely knockdown of BTG2 promoted tumor growth. ConclusionIn summary, our data suggest that BTG2 acts as a tumor suppressor in CESC and inhibits the growth and metastasis of CESC. BTG2 may serve as a potential prognostic marker in CESC and is expected to provide a therapeutic strategy for patients with CESC.

B-Cell Translocation Gene 2 Upregulation Is Associated with Favorable Prognosis in Lung Adenocarcinoma and Prolonged Patient Survival.

The tumor suppressor protein B-cell translocation gene 2 (BTG2) is downexpressed in lung adenocarcinoma (LUAD); however, its role in LUAD survival remains unknown. This investigation is aimed at exploring the activity of BTG2 in LUAD. We analyzed BTG2 expression in LUAD datasets of the TCGA database and examined that BTG2 was markedly downregulated in comparison with adjacent normal tissues. The prognostic analysis suggested that higher expression of BTG2 protein correlates with prolonged survival in patients. Vectors expressing BTG2 were stably transduced into lung adenocarcinoma A549 cells. The overexpression of BTG2 in A549 cells causes cellular G1 phase arrest but did not affect cell proliferation, accompanied by increased activation of NF-κB. Our data indicate that BTG2 overexpression may trigger an autoregulatory prosurvival NF-κB pathway, which is resistant to environmental intervention owing to an increased level of BTG2.

Elevated BTG2 improves the radiosensitivity of non-small cell lung cancer (NSCLC) through apoptosis.

BackgroundTo identify radio‐responsive genes and explore the biological function of encoded proteins in non‐small cell lung cancer (NSCLC).MethodsRadio‐responsive genes in irradiated H460 cells were screened from microarray data deposited in the Gene Expression Omnibus (GEO) database. A quantitative real time polymerase chain reaction assay was used to detect the expression of candidate radio‐responsive genes in irradiated cells. CCK‐8 assay, EDU assay, clone formation assay, immunofluorescence and flow cytometry were conducted to evaluate the biological function of B cell translocation gene 2 (BTG2) in NSCLC.ResultsBioinformatic analysis using GES20549 showed that BTG2 was a radio‐responsive gene in irradiated H460 cells. The mRNA expression level of BTG2 was lower in H460 cells compared with that in BEAS‐2B normal lung epithelial cells. BTG2 expression was elevated upon IR exposure, in a dose‐dependent but not a time‐dependent manner. CCK‐8 and EDU assays revealed that BTG2 overexpression inhibited the growth rate of irradiated cells. Clone formation showed that elevated BTG2 promoted DNA damage of irradiated H460 cells. The number of γ‐H2AX foci induced by DNA damage was also markedly increased upon BTG2 overexpression. Flow cytometry showed that BTG2 increased IR‐induced cell apoptosis.ConclusionsBTG2 may be a novel radio‐responsive factor and a promising therapeutic target for radiotherapy of NSCLC.

BTG2 as a tumor target for the treatment of luminal A breast cancer.

As one of the most common breast cancer subtypes, luminal A breast cancer is sensitive to endocrine-based therapy and insensitive to chemotherapy. Patients with luminal A subtype of breast cancer have a relatively good prognosis compared with that of patients with other subtypes of breast cancer. However, with the increased incidence in endocrine resistance and severe side effects, simple endocrine therapy has become unsuitable for the treatment of luminal A breast cancer. Therefore, identifying novel therapeutic targets for luminal A breast cancer may accelerate the development of an effective therapeutic strategy. The bioinformatical analysis of the current study, which included KEGG and GO analyses of the GSE20437 dataset containing 24 healthy and 18 breast cancer tissue samples, identified key target genes associated with breast cancer. Moreover, survival analysis results revealed that a low expression of BTG2 was significantly associated with the low survival rate of patients with breast cancer, indicated that B-cell translocation gene 2 (BTG2) may be a potential target in breast cancer. However, BTG2 may be cancer type-dependent, as overexpression of BTG2 has been demonstrated to suppress the proliferation of pancreatic and lung cancer cells, but promote the proliferation of bladder cancer cells. Since the association between BTG2 and luminal A-subtype breast cancer remains unclear, it is important to understand the biological function of BTG2 in luminal A breast cancer. Based on the expression levels of estrogen receptor, progesterone receptor and human epidermal growth factor receptor, MCF-7 cells were selected in the present study as a luminal A breast cancer cell type. MTT, Transwell invasion and wound healing assays revealed that overexpression of BTG2 suppressed the levels of MCF-7 cell proliferation, migration and invasion. In addition, the downregulation of BTG2 at the mRNA and protein level was also confirmed in luminal A breast tumor tissue, which was consistent with the results in vitro. These results indicated that BTG2 may act as an effective target for the treatment of luminal A breast cancer.

The oncogenic miR-27a/BTG2 axis promotes obesity-associated hepatocellular carcinoma by mediating mitochondrial dysfunction.

Obesity is closely related to the initiation and development of hepatocellular carcinoma (HCC). The regulatory mechanism of obesity-associated HCC remains unclear. HepG2 cells treated with palmitic acid (PA) and diethylnitrosamine (DEN)-induced HCC mice fed a high-fat diet (HFD) were established. The expression of miR-27a and B-cell translocation gene 2 (BTG2) mRNA and protein were detected via qPCR and western blotting. Prediction software and luciferase assays were employed to verify the miR-27a/BTG2 axis. The biological effects of HepG2 cells were evaluated with ORO staining, MTT assays, Transwell assays, Mito-Timer, and Mito-SOX staining. Significantly upregulated miR-27a and downregulated BTG2 mRNA and protein were observed in HepG2 cells and liver tissues of HCC mice. Overexpressing miR-27a (mi-miR-27a) markedly promoted cellular lipid accumulation, proliferation, and invasion, accompanied by aggravated mitochondrial dysfunction (increased fading and ROS products of mitochondria) in HepG2 cells. Additionally, these effects were further reinforced in HepG2 cells treated with mi-miR-27a and PA. BTG2 was identified as a direct target and was negatively regulated by miR-27a. Similarly, BTG2 knockdown (sh-BTG2) had effects identical to those of mi-miR-27a on HepG2 cells. Additionally, PA evidently enhanced these effects of sh-BTG2 in HepG2 cells. Moreover, BTG2 overexpression effectively reversed the effects of miR-27a, including lipotropic and oncogenic effects, and simultaneously promoted mitochondrial imbalance in HepG2 cells. Thus, obesity-associated miR-27a acts as an oncogene to promote lipid accumulation, proliferation, and invasion by negatively regulating BTG2-mediated mitochondrial dysfunction in HCC.

Exosomal microRNA-15a from ACHN cells aggravates clear cell renal cell carcinoma via the BTG2/PI3K/AKT axis.

Accumulating studies have indicated that exosomal microRNAs (miRNAs/miRs) can mediate clear cell renal cell carcinoma (ccRCC) at the early stage, but the mechanisms remain to be specified. Here, we investigated the mechanism of exosomal miR-15a in ccRCC. After successful isolation of exosomes from RCC cells, we found that miR-15a was upregulated in ccRCC cells. Moreover, upregulation of miR-15a by pre-miR-15a promoted the proliferation, migration, invasion, and epithelial-mesenchymal transition of ccRCC cells. A luciferase assay revealed that B-cell translocation gene 2 (BTG2) was a target gene of miR-15a and negatively correlated with miR-15a expression. BTG2 was poorly expressed in ccRCC, which reduced the proliferation of ccRCC cells. In addition, overexpression of BTG2 could reverse the promotive effects of miR-15a on ccRCC. Furthermore, BTG2 reduced PI3K/AKT pathway activity. Our results collectively indicated that exosomal miR-15a from RCC cells accelerated cell viability by downregulating BTG2 and promoting the activity of the PI3K/AKT signaling pathway. We demonstrated a novel mechanism by which exosomal miR-15a exerted pro-proliferatory effects on ccRCC, highlighting the potential of exosomal miR-15a as a target for ccRCC prognosis.

MiR-365 secreted from M2 Macrophage-derived extracellular vesicles promotes pancreatic ductal adenocarcinoma progression through the BTG2/FAK/AKT axis.

Clinical and experimental evidence indicates that tumour‐associated macrophages support cancer progression. Moreover, macrophage‐derived extracellular vesicles (EVs) are involved in pathogenesis of multiple cancers, yet the functions of molecular determinants in which have not been fully understood. Herein, we aim to understand whether macrophage modulates pancreatic ductal adenocarcinoma (PDAC) progression in an EV‐dependent manner and the underlying mechanisms. microRNA (miR)‐365 was experimentally determined to be enriched in the EVs from M2 macrophages (M2‐EVs), which could be transferred into PDAC cells. Using a co‐culture system, M2‐EVs could enhance the proliferating, migrating and invading potentials of PDAC cells, while inhibition of miR‐365 in M2‐EVs could repress these malignant functions. B‐cell translocation gene 2 (BTG2) was identified to be a direct target of miR‐365, while the focal adhesion kinase (F/ATP)‐dependent tyrosine kinase (AKT) pathway was activated by miR‐365. We further demonstrated that overexpression of BTG2 could delay the progression of PDAC in vitro, whereas by impairing BTG2‐mediated anti‐tumour effect, M2‐EV‐miR‐365 promoted PDAC progression. For validation, a nude mouse model of tumorigenesis was established, in which we found that targeting M2‐EV‐miR‐365 contributed to suppression of tumour growth. Collectively, M2‐EVs carry miR‐365 to suppress BTG2 expression, which activated FAK/AKT pathway, thus promoting PDAC development.

Platelet microparticles-derived miR-25-3p promotes the hepatocyte proliferation and cell autophagy via reducing B-cell translocation gene 2.

Platelets are critical regulators of liver regeneration, but the mechanisms are still not fully understood. Platelets have been shown to contain a wide variety of microRNAs (miRNAs) and play an important role in many diseases. However, the mechanism that how the platelet microparticles (PMPs)-derived miRNA regulate the hepatocyte proliferation is not very clear. In this study, we have successfully isolated and identified PMPs. We also found that PMPs, which could be well integrated into the HHL-5 cells, could upregulate the level of miR-25-3p in HHL-5 cells. Meanwhile, we found that PMPs-derived miR-25-3p promoted HHL-5 cells proliferation by accelerating cells into the S phase, and enhanced the autophagy by increasing the LC3II expression and reducing the P62 expression. Then, we proved that the miR-25-3p could target the B-cell translocation gene 2 (BTG2) and downregulate the expression levels of the BTG2 gene in HHL-5 cells. In addition, the overexpression of BTG2 significantly inhibited the proliferation and autophagy abilities of HHL-5 cells, while cotransfected miR-25-3p mimics or PMPs could partially rescue HHL-5 cells proliferation and autophagy. Furthermore, we proved that PMPs accelerated hepatocyte proliferation by regulating autophagy pathways. Therefore, PMPs-derived miR-25-3p promoted HHL-5 cell proliferation and autophagy by targeting BTG2, which may be a new therapeutic method for liver regeneration.

MiR-487a performs oncogenic functions in osteosarcoma by targeting BTG2 mRNA.

Aberrant microRNA (miRNA) expression plays a critical role in osteosarcoma (OS) pathogenesis. In this study, we elucidated the involvement of miR-487a in OS and the underlying molecular mechanisms. We found that miR-487a was upregulated in OS clinical samples and cell lines. Knockdown of miR-487a suppressed OS cell growth and invasion and induced apoptosis; however, overexpression of miR-487a promoted OS cell growth and invasion. Accordingly, downregulation of miR-487a significantly suppressed tumor growth of OS xenografts in vivo. Furthermore, B-cell translocation gene 2 (BTG2) mRNA was found to be a novel target of miR-487a. Knockdown of BTG2 using small interfering RNA (siRNA) recapitulated the oncogenic effects of miR-487a, whereas BTG2 overexpression partially reversed these effects. Finally, miR-487a levels were found to be negatively correlated with BTG2 expression in OS clinical samples. Collectively, our data suggest that miR-487a is an oncogenic miRNA in OS and it lowers BTG2 expression.

BTG2 is a tumor suppressor gene upregulated by p53 and PTEN in human bladder carcinoma cells.

Although widely deemed as a tumor suppressor gene, the role of B‐cell translocation gene 2 (BTG2) in bladder cancer is still inconclusive. We investigated the role and regulatory mechanism of BTG2 in bladder cancer. BTG2 expression in human bladder tissues was determined by RT‐qPCR and immunoblotting assays. Expressions of BTG2 and PTEN in bladder carcinoma cells were determined by immunoblotting, RT‐qPCR, or reporter assays. The 3H‐thymidine incorporation assay, flow cytometry, and the xenograft animal model were used to determine the cell growth. BTG2 expression was lower in human bladder cancer tissues than normal bladder tissues. Highly differentiated bladder cancer cells, RT4, expressed higher BTG2 than the less‐differentiated bladder cancer cells, HT1376 and T24. Overexpression of BTG2 in T24 cells inhibited cell growth in vitro and in vivo. Camptothecin and doxorubicin treatments in RT‐4 cells or transient overexpression of p53 into p53‐mutant HT1376 cells induced p53 and BTG2 expression. Further reporter assays with site‐mutation of p53 response element from GGGAAAGTCC to GGAGTCC within BTG2 promoter area showed that p53‐induced BTG2 gene expression was dependent on the p53 response element. Ectopic PTEN overexpression in T24 cells blocked the Akt signal pathway which attenuated cell growth via upregualtion of BTG2 gene expression, while reverse effect was found in PTEN‐knockdown RT‐4 cells. PTEN activity inhibitor (VO‐OHpic) treatment decreased BTG2 expression in RT‐4 and PTEN‐overexpressed T24 cells. Our results suggested that BTG2 functioned as a bladder cancer tumor suppressor gene, and was induced by p53 and PTEN. Modulation of BTG2 expression seems a promising way to treat human bladder cancer.

BTG2 Is Down-Regulated and Inhibits Cancer Stem Cell-Like Features of Side Population Cells in Hepatocellular Carcinoma.

Our previous study found that B cell translocation gene 2 (BTG2) was hyper-methylated and down-regulated in side population (SP) cells of hepatocellular carcinoma (HCC) cell line. However, its clinical significances and biological impacts on HCC SP cells remained unclear. To investigate the prognostic value of BTG2 gene in HCC and its influences on cancer stem cells (CSCs)-like traits of HCC cell line SP cells. BTG2 expression in human HCC and adjacent non-cancerous tissues was detected by immunohistochemical staining and quantitative real-time PCR, and also obtained from GEO and TCGA data. Its prognostic values were assessed. Its biological influences on HCC cell line SP cells were evaluated using cell viability, cell cycle, plate clone-forming assay, and chemoresistance in vitro and tumorigenicity in vivo. BTG2 expression was significantly suppressed in human HCC compared to adjacent non-cancerous tissues. BTG2 expression was correlated with TNM stage, tumor size and vascular invasion. Lower expression of BTG2 was associated with poorer overall survival and disease-free survival. In vitro, overexpression of BTG2 substantially suppressed cell proliferation and accumulation of HCC cell line SP cells in G0/G1 phase. Colony formation ability was markedly suppressed by BTG2 overexpression. Moreover, sensitivity of HCC cell line SP cells to 5-fluorouracil was substantially increased by overexpression of BTG2. Furthermore, tumorigenicity of HCC cell line SP cells transfected with BTG2 plasmids was significantly reduced in vivo. BTG2 gene could regulate the CSC-like traits of HCC cell line SP cells, and it represented as a molecular prognostic marker for HCC.

Expression of B-cell translocation gene 2 is associated with favorable prognosis in hepatocellular carcinoma patients and sensitizes irradiation-induced hepatocellular carcinoma cell apoptosis in vitro and in nude mice.

B-cell translocation gene 2 (BTG2) proteins have been reported to be putative tumor suppressors in various cancer types. The present study first assessed BTG2 expression in 44 human liver cancer tissue specimens, then investigated BTG2 expression in the regulation of hepatocellular carcinoma (HCC) cell apoptosis with or without radiotherapy in vitro and in vivo. The results revealed that BTG2 protein expression was significantly reduced in HCC tissues, and associated with better survival for HCC patients (P=0.05). BTG2 overexpression also sensitized Huh7 cells to radiation-induced apoptosis in vitro and in a nude mouse model, although restoration of BTG2 expression per se did not affect the viability and apoptosis of HCC cells. Future studies would confirm the role of BTG2 in hepatoma, and further develop BTG2 as a therapeutic strategy for controlling HCC.

Inhibitory effects of B‑cell translocation gene2 on skin cancer cells via the Wnt/β‑catenin signaling pathway.

B-cell translocation gene2 (BTG2), a tumor suppressor gene, is downregulated in several types of human cancer cell. However, its function in skin cancer cells has not been fully elucidated. Therefore, the present study investigated the expression and function of BTG2 in skin cancer cells, and investigated the underlying molecular mechanism. The results indicated that BTG2 expression was downregulated in skin cancer cell lines. Overexpression of BTG2 significantly inhibited cell proliferation, cell cycle progression, and the invasion and migration of skin cancer cells. Furthermore, it was determined that overexpression of BTG2 significantly decreased the protein expression levels of β‑catenin, cyclinD1 and v‑myc avian myelocytomatosis viral oncogene homolog in skin cancer cells. This suggests that BTG2 may function as a tumor suppressor by interfering with the Wnt/β‑catenin signaling pathway in skin cancer cells. Thus, novel therapeutic strategies and agents targeting BTG2 may be potential treatments for skin cancer.

MiR-27a-3p functions as an oncogene in gastric cancer by targeting BTG2.

microRNA-27a (miR-27a) is frequently dysregulated in human carcinoma, including gastric cancer. The B-cell translocation gene 2 (BTG2) has been implicated in gastric carcinogenesis. However, till now, the link between miR-27a and BTG2 in gastric cancer has not been reported. Here, we found that two isoforms of mature miR-27a, miR-27a-5p and miR-27-3p, were both frequently overexpressed in gastric cancer tissues and cell lines, whereas the expression level of miR-27-3p in gastric cancer was significantly higher than that of miR-27a-5p. And overexpression of miR-27a-3p, but not miR-27a-5p, markedly promoted gastric cancer cell proliferation in vitro as well as tumor growth in vivo. Further experiments revealed that BTG2 was a direct and functional target of miR-27a-3p in gastric cancer and miR-27a-3p inhibition obviously up-regulated the expression of BTG2. In turn, overexpression of BTG2 triggered G1/S cell cycle arrest, induced subsequent apoptosis, and inhibited C-myc activation following Ras/MEK/ERK signaling pathway, which involved in the biological effects of miR-27a-3p/BTG2 axis on gastric carcinogenesis and cancer progression. Overall, these results suggested that the miR-27a-3p/BTG2 axis might represent a promising diagnostic biomarker for gastric cancer patients and could be a potential therapeutic target in the management of gastric cancer.

B-cell translocation gene 2 promotes hepatic hepcidin production via induction of Yin Yang 1

Hepcidin is a peptide hormone secreted in the liver and plays a key role in maintaining iron homeostasis. Here, we demonstrate that B-cell translocation gene 2 (BTG2) is a key player in hepatic hepcidin regulation via induction of Yin Yang 1 (YY1). Hepatic hepcidin gene expression significantly enhanced by fasting states and glucagon exposure led to induction of gluconeogenic gene expression, and elevated serum hepcidin production in mice. Notably, overexpression of BTG2 using adenoviral system (Ad-BTG2) significantly elevated serum hepcidin levels via a significant induction of YY1 gene transcription. Immunoprecipitation studies demonstrated that BTG2 physically interacted with YY1 and recruited on the hepcidin gene promoter. Finally, ablation of hepatic BTG2 gene by gene silencing markedly attenuated the elevation of serum hepcidin production along with YY1 and hepcidin mRNA expression in fasting state. Likewise, forskolin (FSK)-stimulated hepcidin promoter activity was dramatically disrupted by endogenous BTG2 knockdown. Overall, our current study provides a novel molecular mechanism of BTG2-mediated induction of hepcidin gene expression, thereby contributing to a better understanding of the hepatic hepcidin production involved in iron homeostasis.

Upregulation of B-cell translocation gene 2 by epigallocatechin-3-gallate via p38 and ERK signaling blocks cell proliferation in human oral squamous cell carcinoma cells

Oral squamous cell carcinoma (OSCC) is a well-known malignancy that accounts for the majority of oral cancers. B-cell translocation gene 2 (BTG2) is an important regulator of cell cycle dynamics in cancer cells. However, the role of BTG2 in OSCC cells and the influences of epigallocatechin-3-gallate (EGCG) on BTG2 gene expressions have not been well evaluated. The objectives of this study were to examine the effect of EGCG-induced BTG2 expression and the potential signal pathways involved. The 3H-thymidine incorporation and Western-blot assays revealed cell proliferation was attenuated by EGCG via upregulation of BTG2 expression causing cell cycle G1 phase arrest in OSCC cells. BTG2 overexpression decreased tumor cell growth, while BTG2 knockdown illuminated the opposite effect in xenograft animal studies. Overexpressed BTG2 arrested the cell cycle at the G1 phase and downregulated protein expressions of cyclin A, cyclin D, and cyclin E. Western-blot assays indicated that EGCG induced phosphorylation of p38, JNK, and ERK. However, pretreatments with selective mitogen-activated protein kinase (MAPK) inhibitors, SB203580 (p38 inhibitor) and PD0325901 (ERK1/2 inhibitor), significantly suppressed the activation of EGCG on BTG2 expression. Our results indicate that EGCG attenuates cell proliferation of OSCC cells by upregulating BTG2 expression via p38 and ERK pathways.

B-cell translocation gene 2 positively regulates GLP-1-stimulated insulin secretion via induction of PDX-1 in pancreatic β-cells

Glucagon-like peptide-1 (GLP-1) is a potent glucoincretin hormone and an important agent for the treatment of type 2 diabetes. Here we demonstrate that B-cell translocation gene 2 (BTG2) is a crucial regulator in GLP-1-induced insulin gene expression and insulin secretion via upregulation of pancreatic duodenal homeobox-1 (PDX-1) in pancreatic β-cells. GLP-1 treatment significantly increased BTG2, PDX-1 and insulin gene expression in pancreatic β-cells. Notably, adenovirus-mediated overexpression of BTG2 significantly elevated insulin secretion, as well as insulin and PDX-1 gene expression. Physical interaction studies showed that BTG2 is associated with increased PDX-1 occupancy on the insulin gene promoter via a direct interaction with PDX-1. Exendin-4 (Ex-4), a GLP-1 agonist, and GLP-1 in pancreatic β-cells increased insulin secretion through the BTG2–PDX-1–insulin pathway, which was blocked by endogenous BTG2 knockdown using a BTG2 small interfering RNA knockdown system. Finally, we revealed that Ex-4 and GLP-1 significantly elevated insulin secretion via upregulation of the BTG2–PDX-1 axis in pancreatic islets, and this phenomenon was abolished by endogenous BTG2 knockdown. Collectively, our current study provides a novel molecular mechanism by which GLP-1 positively regulates insulin gene expression via BTG2, suggesting that BTG2 has a key function in insulin secretion in pancreatic β-cells.

B-cell translocation gene-2 increases hepatic gluconeogenesis via induction of CREB

Hepatic gluconeogenesis is mediated by the network of transcriptional factors and cofactors. Here, we show that B-cell translocation gene-2 (BTG2) plays a crucial cofactor in hepatic gluconeogenesis via upregulation of the cyclic AMP (cAMP) response element binding (CREB) in hepatocytes. cAMP/dexamethasone (Dex) significantly increased BTG2 and other gluconeogenic genes such as Nur77, phosphoenolpyruvate carboxykinase (PEPCK), and glucose-6-phosphatase (G6Pase) in hepatocytes. In contrast, insulin treatment completely blocks their expressions. Interestingly, overexpression of BTG2 using adenoviral system (Ad-BTG2) significantly elevated hepatic glucose production via the increase of transcriptional activity and gene expression of CREB, PEPCK, and G6Pase in hepatocytes, suggesting that BTG2 is the key player on hepatic glucose production. Physiological interaction studies demonstrated that BTG2 correlated CREB recruitment on the PEPCK gene promoter via a direct interaction. Finally, knockdown of endogenous BTG2 expression markedly inhibits the cAMP/Dex-induced transcriptional activity of gluconeogenic genes and glucose production in hepatocytes. Overall, the present study provides us with a novel molecular mechanism of BTG2-mediated induction of hepatic gluconeogenesis and suggests that BTG2 plays an important role in hepatic glucose metabolism.

Effects of BTG2 on proliferation inhibition and anti-invasion in human lung cancer cells

The objective of the study was to investigate the impact of the B cell translocation gene 2 (BTG2) on lung cancer cell growth, proliferation, metastasis, and other biological characteristics and to provide experimental evidence for the biological treatment of human lung cancer. A pcDNA3.1-BTG2 eukaryotic expression vector was constructed and transfected into the human lung cancer cell line A549. The biological changes in the BTG2-expressing cells were analyzed using growth curves, the MTT (tetrazolium) assay, propidium iodide (PI) staining, and the Transwell invasion chamber. Additionally, Western blotting was used to determine the impact of BTG2 on the protein expression of cyclin D1, MMP-1, and MMP-2. Compared to the empty vector-transfected A549 cells or the mock-transfected A549 cells, the pcDNA3.1-BTG2-transfected A549 cells grew significantly slower. No significant differences were detected between the empty vector-transfected group and the mock-transfected A549 cells. The growth curve analysis and the PI staining showed that the pcDNA3.1-BTG2-transfected cells grew significantly slower than the empty vector-transfected A549 cells (P < 0.05). The cell invasion assay results suggested that the invasion rate of the pcDNA3.1-BTG2-transfected A549 cells was significantly slower than the invasion rate of the empty vector-transfected group and the mock-transfected group (P < 0.05). The overexpression of BTG2 may inhibit the protein expression of cyclin D1, MMP-1, and MMP-2 in A549 cells. The overexpression of BTG2 may inhibit the growth, proliferation, and invasiveness of the A549 human lung cancer cell line.

Abstract P2-09-09: Loss of BTG2 Expression in Breast Cancer Predicts Tamoxifen Resistance

Abstract Background: The B-cell translocation gene-2 (BTG2) belongs to a class of proteins known as the Tob and BTG anti-proliferative protein family. It was shown that estrogen and progesterone suppress BTG2 mRNA for the development of mammary gland. (Kawakubo et al., Oncogene 2004) Expression analysis of BTG2 protein in estrogen receptor (ER) positive human breast cancer was revealed the loss of nuclear expression in 46% of tumors and showed a significant inverse correlation with cyclinD1 expression. (Kawakubo, Hayashida et al., Cancer Res 2006) According to the Oncomine database online, loss of BTG2 expression significantly correlated with increased recurrence rate after tamoxifen monotherapy. Based on these results, we hypothesized that BTG2 expression might be a novel biomarker for predicting the clinical outcome in tamoxifen treatment and analyzed if BTG2 expression affects the sensitivity against tamoxifen both in vitro and in vivo. Method and Results: The cohort of 60 patients treated with adjuvant tamoxifen monotherapy was available online. (Ma et al., Cancer Cell 2004) Comparison of disease-free survival (DFS) of patients whose laser-captured tumors showed positive BTG2 expression versus patients with loss of BTG2 expression revealed an univariate association in the dataset. (log-rank probability, p=0.029) Multivariate analysis indicated that BTG2 resulted independent prognostic factor for DFS (HR, 0.69; 95% CI, 0.495 to 0.963; p=0.029). In vitro cellular proliferation assay to evaluate the cytotoxicity induced by tamoxifen against ER positive cell lines revealed that endogenous BTG2 positive cell line, MCF7 and T47D, showed drug sensitivity, whereas MDA-MB468 expressing loss of BTG2 showed tamoxifen resistance. (MCF7; IC50=7.35uM, T47D; =3.79uM, MDA-MB468; &amp;gt;25.0uM) Tetracycline-inducible BTG2 expression model in MCF7 was developed to assess the cytotoxicity by tamoxifen treatment under the condition of BTG2 overexpression in vitro and in vivo. The cellular proliferation was strongly inhibited by the concomitant administration of tetracyclin and tamoxifen in vitro. The cell line was injected into the mammary fad pad of immunodeficient mice and these were administered water including tetracyclin and/or tamoxifen pellet at the time when the xenografted tumor grew to be over 125mm3 for 3 weeks. The transgene expression was confirmed by both RT-PCR and immunohistochemistry. Tumor growth ratio was significantly suppressed in the concomitant administration of tetracyclin and tamoxifen in comparison with single treatment of tamoxifen or of tetracyclin. Consistently, tumor weight and Ki67 expression were also significantly suppressed in the mice administered both tamoxifen and tetracyclin. Conclusion: Despite further validation studies need to be conducted, BTG2 expression may be useful biomarker to identify patients appropriate for tamoxifen treatment. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P2-09-09.