Transcription Factor E3 Overexpression Research Articles

TFE3/PI3K/Akt/mTOR Axis in Renal Cell Carcinoma Affects Tumor Microenvironment

The role of the phosphatidylinositol 3-kinase (PI3K)/Akt pathway in renal cell carcinoma (RCC) progression, metastasis, and resistance to therapies has not been investigated thoroughly. Transcription factor E3 (TFE3) expression is related to a poorer prognosis and tumor microenvironment in patients with RCC. This study aimed to determine the relationship between TFE3 and the PI3K/Akt pathway. TFE3 down-regulation was achieved by transient transfection of siRNA and shRNA in UOK146 cells. TFE3 overexpression was induced by transient transfection with pcDNA3.1 encoding the constitutively active form of TFE3. The cells were treated with mammalian target of rapamycin (mTOR) and PI3K inhibitors. Western blot was performed to detect TFE3, programmed death-ligand 1, phospho-Akt, and Akt. Phospho-Akt expression increased significantly upon TFE3 down-regulation, and decreased significantly upon up-regulation. When RCC cells were treated with a PI3K inhibitor (LY294002), TFE3 expression increased and phospho-Akt expression decreased. Data from this study indicate that TFE3 plays a role in the PI3K/Akt pathway in RCC. The results of this study suggest that PI3K/Akt inhibitors may aid in the treatment of patients with RCC by affecting the tumor microenvironment.

TFE3-Mediated Autophagy is Involved in Dopaminergic Neurodegeneration in Parkinson's Disease.

Impairment of autophagy has been strongly implicated in the progressive loss of nigral dopaminergic neurons in Parkinson’s disease (PD). Transcription factor E3 (TFE3), an MiTF/TFE family transcription factor, has been identified as a master regulator of the genes that are associated with lysosomal biogenesis and autophagy. However, whether TFE3 is involved in parkinsonian neurodegeneration remains to be determined. In this study, we found decreased TFE3 expression in the nuclei of the dopaminergic neurons of postmortem human PD brains. Next, we demonstrated that TFE3 knockdown led to autophagy dysfunction and neurodegeneration of dopaminergic neurons in mice, implying that reduction of nuclear TFE3 may contribute to autophagy dysfunction-mediated cell death in PD. Further, we showed that enhancement of autophagy by TFE3 overexpression dramatically reversed autophagy downregulation and dopaminergic neurons loss in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) model of PD. Taken together, these findings demonstrate that TFE3 plays an essential role in maintaining autophagy and the survival of dopaminergic neurons, suggesting TFE3 activation may serve as a promising strategy for PD therapy.

GAA deficiency promotes angiogenesis through upregulation of Rac1 induced by autophagy disorder

Angiogenesis, the formation of new blood vessels from pre-existing ones, is vital for vertebrate development and adult homeostasis. Acid α-glucosidase (GAA) is a glycoside hydrolase involved in the lysosomal breakdown of glycogen. Our previous study showed that GAA was highly expressed in mouse pulmonary veins. While whether GAA was involved in angiogenesis remained largely unknown, thus, we performed knockdown experiments both in vivo and in vitro and endothelial cell function experiments to clarify this concern point. We identified that GAA expressed widely at different levels during zebrafish embryonic development and GAA morphants showed excessive angiogenesis of ISV at later stage. In GAA knockdown HUVECs, the migration and tube formation capacity were increased, resulted from the formation of large lamellipodia-like protrusions at the edge of cells. By analyzing autophagic flux, we found that autophagy disorder was the mechanism of GAA knockdown-induced excessive angiogenesis. The block of autophagic flux caused upregulation of Rac1, a small GTPase, and the latter promoted excessive sprouts in zebrafish and enhanced angiogenic behavior in HUVECs. In addition, overexpression of transcription factor E3, a master regulator of autophagy, rescued upregulation of RAC1 and enhanced angiogenic function in GAA-knockdown HUVECs. Also, inhibition of Rac1 partly restored enhanced angiogenic function in GAA-knockdown HUVECs. Taken together, our study firstly reported a novel function of GAA in angiogenesis which is mediated by upregulation of Rac1 induced by autophagy disorder.

Glycochenodeoxycholic acid impairs transcription factor E3 -dependent autophagy-lysosome machinery by disrupting reactive oxygen species homeostasis in L02 cells

Cholestasis represents pathophysiologic syndromes defined as impaired bile flow from the liver. As an outcome, bile acids accumulate and promote hepatocyte injury, followed by liver cirrhosis and liver failure. Glycochenodeoxycholic acid (GCDCA) is relatively toxic and highly concentrated in bile and serum after cholestasis. However, the mechanism underlying GCDCA-induced hepatotoxicity remains unclear. In this study, we found that GCDCA inhibits autophagosome formation and impairs lysosomal function by inhibiting lysosomal proteolysis and increasing lysosomal pH, contributing to defects in autophagic clearance and subsequently leading to the death of L02 human hepatocyte cells. Notably, through tandem mass tag (TMT)-based quantitative proteomic analysis and database searches, 313 differentially expressed proteins were identified, of which 71 were increased and 242 were decreased in the GCDCA group compared with those in the control group. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed that GCDCA suppressed the signaling pathway of transcription factor E3 (TFE3), which was the most closely associated with autophagic flux impairment. In contrast, GCDCA-inhibited lysosomal function and autophagic flux were efficiently attenuated by TFE3 overexpression. Specifically, the decreased expression of TFE3 was closely related to the disruption of reactive oxygen species (ROS) homeostasis, which could be prevented by inhibiting intracellular ROS with N-acetyl cysteine (NAC). In summary, our study is the first to demonstrate that manipulation of ROS/TFE3 signaling may be a therapeutic approach for antagonizing GCDCA-induced hepatotoxicity.

Granular cell tumors overexpress TFE3 without gene rearrangement: Evaluation of immunohistochemistry and break-apart FISH in 45 cases.

Transcription factor E3 (TFE3) is a useful marker for tumors with Xp11.2 translocation, including alveolar soft part sarcoma and renal cell carcinoma. Recently, TFE3 overexpression was also found in granular cell tumors (GrCTs). However, the case cohorts of these two studies were limited to only 11 and 6 cases. Whether aberrant TFE3 expression is a common feature of Asian patients with GrCT requires further investigation. In the present study, immunohistochemical staining and TFE3 break-apart fluorescence in situ hybridization (FISH) assay were performed in 45 samples of GrCTs obtained from Chinese patients recruited from three medical centers in northeast China. Diffusive and marked nuclear staining for TFE3 was identified in 11/45 (24%) cases, which was lower than previously reported. Focal or weak TFE3 staining was identified in 13/45 (29%) cases. The remaining 21 cases were negative stained. In addition, GrCTs in subcutaneous tissue exhibited a relatively higher ratio (8/45, 18%) for TFE3 expression, compared with those in other sites. Furthermore, according to FISH data, no rearrangement or amplification of TFE3 was identified in these cases, whether they were positively or negatively stained for TFE3. The results from the present study demonstrated that part of patients GrCTs exhibited TFE3 overexpression, which suggested that this may not be derived from gene rearrangement.

TFE3 regulates renal adenocarcinoma cell proliferation via activation of the mTOR pathway.

The present study aimed to investigate the role of transcription factor E3 (TFE3) in the regulation of proliferation in renal adenocarcinoma cells. The LV-TFE3 overexpression (OE) lentivirus and negative control CON195 (NC) lentivirus were transfected into the ACHN cell line. Protein expression of FLAG-tag TFE3 was determined using western blot analysis. Differences in cell proliferation, plate clone formation and cell cycle distribution between OE and NC groups were compared using MTT, plate colony formation and flow cytometry assays, respectively. The levels of mammalian target of rapamycin (mTOR) and phosphorylated ribosomal protein S6 (p-rpS6) were analyzed by western blotting. Cell proliferation and colony formation increased significantly in the OE group compared with the NC group. The % of cells in the G1 and G2 phases of the cell cycle decreased, while the % of cells in the S phase of the cell cycle increased in the OE group compared with the NC group. In addition, mTOR and p-rpS6 levels were increased in the OE group compared with the NC group. The results of the present study demonstrated that TFE3 overexpression resulted in increased ACHN cell proliferation and plate clone formation. TFE3 may promote renal tumor growth by regulating cell cycle progression and activating the phosphatidylinositol 3-kinase/AKT serine/threonine kinase 1/mTOR signaling pathway.

TFE3 Alleviates Hepatic Steatosis through Autophagy-Induced Lipophagy and PGC1α-Mediated Fatty Acid β-Oxidation.

Autophagy flux deficiency is closely related to the development of hepatic steatosis. Transcription factor E3 (TFE3) is reported to be a crucial gene that regulates autophagy flux and lysosome function. Therefore, we investigated the role of TFE3 in a cell model of hepatic steatosis. We constructed L02 hepatocyte lines that stably over-expressed or knocked down the expression of TFE3. Subsequently, the effects of TFE3 on hepatocellular lipid metabolism were determined by autophagy flux assay, lipid oil red O (ORO) staining, immunofluorescence staining, and mitochondrial β-oxidation assessment. Finally, we analyzed whether peroxisome proliferative activated receptor gamma coactivator 1α (PGC1α) was the potential target gene of TFE3 in the regulation of hepatic steatosis using a chromatin immunoprecipitation (CHIP) assay and a luciferase reporter system. We found that overexpression of TFE3 markedly alleviated hepatocellular steatosis. On the contrary, downregulation of TFE3 resulted in an aggravated steatosis. The mechanistic studies revealed that the TFE3-manipulated regulatory effects on hepatocellular steatosis are dependent on autophagy-induced lipophagy and PGC1α-mediated fatty acid β-oxidation because blocking these pathways with an Atg5 small interfering RNA (siRNA) or PGC1α siRNA dramatically blunted the TFE3-mediated regulation of steatosis. In conclusion, TFE3 gene provides a novel insight into the treatment of hepatic steatosis and other metabolic disease.

TFE3 inhibits myoblast differentiation in C2C12 cells via down-regulating gene expression of myogenin

Transcription factor E3 (TFE3) belongs to a basic helix–loop–helix family, and is involved in the biology of osteoclasts, melanocytes and their malignancies. We previously reported the metabolic effects of TFE3 on insulin in the liver and skeletal muscles in animal models. In the present study, we explored a novel role for TFE3 in a skeletal muscle cell line. When TFE3 was overexpressed in C2C12 myoblasts by adenovirus before induction of differentiation, myogenic differentiation of C2C12 cells was significantly inhibited. Adenovirus-mediated TFE3 overexpression also suppressed the gene expression of muscle regulatory factors (MRFs), such as MyoD and myogenin, during C2C12 differentiation. In contrast, knockdown of TFE3 using adenovirus encoding short-hairpin RNAi specific for TFE3 dramatically promoted myoblast differentiation associated with significantly increased expression of MRFs. Consistent with these findings, promoter analyses via luciferase reporter assay and electrophoretic mobility shift assay suggested that TFE3 negatively regulated myogenin promoter activity by direct binding to an E-box, E2, in the myogenin promoter. These findings indicated that TFE3 has a regulatory role in myoblast differentiation, and that transcriptional suppression of myogenin expression may be part of the mechanism of action.

Translocation renal cell carcinomas: An evolving entity.

e15078 Background: Translocation renal cell carcinomas (tRCCs) are a novel, rare and distinct clinicopathological entity. The term refers to RCCs with overexpression of transcription factor E3 (TFE3) due to translocation involving the Xp11 locus or less commonly with overexpression of transcription factor EB (TFEB) due to a t(6:11) translocation. In children it is estimated that these tumours account for 40% of RCCs but in adults this proportion is estimated to be 1-4%. These neoplasms are only recently recognised and outcome data are premature. We report 2 cases of tRCC in an Irish regional cancer centre and describe clinicopathological characteristics and early outcome. Methods: : Approximately 70 new cases of RCC are referred to our centre annually. Recently, 2 renal cell carcinomas were suspected to be tRCCs on morphology and immunohistochemical(IHC) features (RCC+/CK7-/EMA-). Using IHC we tested for expression of TFE3 and TFEB. Results: : Both tumours were tRCCs. The first case was a 74 year old lady who presented with right upper quadrant pain and had a 9cm right renal mass with no metastatic disease on CT imaging. Radical nephrectomy was performed and histology revealed a pT3aN2, Fuhrman grade 4 RCC with mixed clear cell and papillary architecture. IHC for TFE3 showed focal nuclear positivity consistent with an Xp11 translocation RCC. She relapsed 9 months later with local recurrence, retroperitoneal adenopathy and lung metastases. She commenced sunitinib and response assessment is pending. The 2nd case was a 46 year old man with an incidental finding of a right renal mass on ultrasound abdomen. Staging CT revealed no metastatic disease and he underwent laparoscopic nephrectomy. Histology revealed a pT1aNx, Fuhrman grade 3 renal cell carcinoma with predominantly alveolar architecture and focal papillary and microcystic areas. IHC for TFEB was positive consistent with a t6:11 translocation RCC. He remains disease free 9 months post surgery. Conclusions: We report 2 new cases of this rare subset of RCC. The therapeutic implications for patients with these mutations are as yet unclear. We plan to update with ongoing follow-up and will also report 3 further cases suspected to be tRCCs based on morphology and IHC. Confirmatory TFE3/TFEB IHC is awaited.

Translocation renal cell carcinomas: An evolving entity.

472 Background: Translocation renal cell carcinomas (RCCs) are a novel, rare and distinct clinicopathological entity. The term refers to RCCs with overexpression of transcription factor E3 (TFE3) due to translocation involving the Xp11 locus or less commonly with overexpression of transcription factor EB (TFEB) due to a t(6:11) translocation. In children it is estimated that these tumours account for 40% of RCCs but in adults this proportion is estimated to be 1-4%. As these neoplasms are only recently recognised, outcome data are premature. We report 2 cases of translocation RCC in an Irish regional cancer centre and describe clinicopathological characteristics and early outcome. Methods: In our recent practice, 2 renal cell carcinomas were suspected to be translocation tumours based on morphology and immunohistochemical features (RCC+/CK7-/EMA-). Using immunohistochemistry we tested for expression of TFE3 and TFEB. Results: Both tumours were translocation RCCs. The first case was a 74 year old lady who presented with right upper quadrant pain and had a 9cm right renal mass with no metastatic disease on CT imaging. Radical nephrectomy was performed and histology revealed a pT3aN2, Fuhrman grade 4 renal cell carcinoma with papillary architecture and eosinophillic hyaline nodules within many of the papillae. Staining for TFE3 showed focal nuclear positivity consistent with an Xp11 translocation RCC. She remains disease free 6 months post surgery. The second case was a 46 year old man with an incidental finding of a right renal mass on ultrasound abdomen performed after a new diagnosis of haemochromatosis. Staging CT imaging revealed no metastatic disease and he underwent laparoscopic nephrectomy. Histology revealed a pT1aNx, Fuhrman grade 3 renal cell carcinoma with predominantly alveolar architecture and focal papillary and microcystic areas. Staining for TFEB was positive consistent with a t6:11 translocation RCC. He remains disease free 5 months post surgery. Conclusions: We report 2 new cases of this rare subset of RCC. The therapeutic implications for patients with these mutations are as yet unclear. We plan to update with ongoing follow-up and identification of new cases to determine the clinical behaviour of these rare cancers in the Irish setting.