Desheng Xiao

EphA2 promotes epithelial–mesenchymal transition through the Wnt/β-catenin pathway in gastric cancer cells

This study aims to investigate the significance of erythropoietin-producing hepatocellular (Eph)A2 expression and the mechanism by which EphA2 is involved in the epithelial–mensenchymal transition (EMT) of gastric cancer cells. EphA2 expression levels were upregulated and positively correlated with metastasis and EMT markers in human gastric cancer specimens. Modulation of EphA2 expression levels had distinct effects on cell proliferation, cell cycle, migration, invasion and morphology in the gastric cancer cell lines SGC7901 and AGS in vitro and in vivo. Overexpression of EphA2 resulted in the upregulation of the EMT molecular markers N-cadherin and Snail, as well as the Wnt/β-catenin targets TCF4, Cyclin-D1 and c-Myc, while silencing EphA2 using short hairpin RNA had the opposite effect. Furthermore, inhibition of the Wnt/β-catenin pathway by XAV939 negated the effect of EphA2 overexpression, whereas activation of the Wnt/β-catenin pathway by LiCl impaired the effect of the EphA2 knockdown on EMT. These observations demonstrate that EphA2 upregulation is a common event in gastric cancer specimens that is closely correlated with cancer metastasis and that EphA2 promotes EMT of gastric cancer cells through activation of Wnt/β-catenin signaling.

Repression of Hox genes by LMP1 in nasopharyngeal carcinoma and modulation of glycolytic pathway genes by HoxC8

Epstein-Barr virus (EBV) causes human lymphoid malignancies, and the EBV product latent membrane protein 1 (LMP1) has been identified as an oncogene in epithelial carcinomas such as nasopharyngeal carcinoma (NPC). EBV can epigenetically reprogram lymphocyte-specific processes and induce cell immortalization. However, the interplay between LMP1 and the NPC host cell remains largely unknown. Here, we report that LMP1 is important to establish the Hox gene expression signature in NPC cell lines and tumor biopsies. LMP1 induces repression of several Hox genes in part via stalling of RNA polymerase II (RNA Pol II). Pol II stalling can be overcome by irradiation involving the epigenetic regulator TET3. Furthermore, we report that HoxC8, one of the genes silenced by LMP1, has a role in tumor growth. Ectopic expression of HoxC8 inhibits NPC cell growth in vitro and in vivo, modulates glycolysis and regulates the expression of tricarboxylic acid (TCA) cycle-related genes. We propose that viral latency products may repress via stalling key mediators that in turn modulate glycolysis.

Chromatin Remodeling Factor LSH Drives Cancer Progression by Suppressing the Activity of Fumarate Hydratase

Chromatin modification is pivotal to the epithelial-mesenchymal transition (EMT), which confers potent metastatic potential to cancer cells. Here, we report a role for the chromatin remodeling factor lymphoid-specific helicase (LSH) in nasopharyngeal carcinoma (NPC), a prevalent cancer in China. LSH expression was increased in NPC, where it was controlled by the Epstein-Barr virus-encoded protein LMP1. In NPC cells in vitro and in vivo, LSH promoted cancer progression in part by regulating expression of fumarate hydratase (FH), a core component of the tricarboxylic acid cycle. LSH bound to the FH promoter, recruiting the epigenetic silencer factor G9a to repress FH transcription. Clinically, we found that the concentration of TCA intermediates in NPC patient sera was deregulated in the presence of LSH. RNAi-mediated silencing of FH mimicked LSH overexpression, establishing FH as downstream mediator of LSH effects. The TCA intermediates α-KG and citrate potentiated the malignant character of NPC cells, in part by altering IKKα-dependent EMT gene expression. In this manner, LSH furthered malignant progression of NPC by modifying cancer cell metabolism to support EMT. Cancer Res; 76(19); 5743-55. ©2016 AACR.

As a novel p53 direct target, bidirectional gene HspB2/αB-crystallin regulates the ROS level and Warburg effect.

Many mammalian genes are composed of bidirectional gene pairs with the two genes separated by less than 1.0kb. The transcriptional regulation and function of these bidirectional genes remain largely unclear. Here, we report that bidirectional gene pair HspB2/αB-crystallin, both of which are members of the small heat shock protein gene family, is a novel direct target gene of p53. Two potential binding sites of p53 are present in the intergenic region of HspB2/αB-crystallin. p53 up-regulated the bidirectional promoter activities of HspB2/αB-crystallin. Actinomycin D (ActD), an activator of p53, induces the promoter and protein activities of HspB2/αB-crystallin. p53 binds to two p53 binding sites in the intergenic region of HspB2/αB-crystallin in vitro and in vivo. Moreover, the products of bidirectional gene pair HspB2/αB-crystallin regulate glucose metabolism, intracellular reactive oxygen species (ROS) level and the Warburg effect by affecting metabolic genes, including the synthesis of cytochrome c oxidase 2 (SCO2), hexokinase II (HK2), and TP53-induced glycolysis and apoptosis regulator (TIGAR). The ROS level and the Warburg effect are affected after the depletion of p53, HspB2 and αB-crystallin respectively. Finally, we show that both HspB2 and αB-crystallin are linked with human renal carcinogenesis. These findings provide novel insights into the role of p53 as a regulator of bidirectional gene pair HspB2/αB-crystallin-mediated ROS and the Warburg effect.

Opposed expression of IKKα: loss in keratinizing carcinomas and gain in non-keratinizing carcinomas

The functional role of IKKα in vivo is pretty complicated, largely due to its diverse functions through cell autonomous and non-autonomous manners. In addition, most of the studies on IKKα were derived from animal models, whether these findings hold true in human tumors remain unclear. Here we examined the expression of IKKα in nasopharyngeal carcinoma, which includes non-keratinizing carcinoma and keratinizing squamous cell carcinoma, and lung squamous cell carcinoma with keratinization and non-keratinization. We demonstrated that IKKα expression was almost negative in keratinizing cancer and higher expression of IKKα was found in non-keratinizing cancer, and that IKKα expression correlateed with cellular differentiation of tumors in non-keratinizing nasopharyngeal carcinoma. These findings demonstrate that IKKα is diversely expressed in keratinizing and non-keratinizing carcinomas in the same type of cancer.

Chromatin Remodeling Factor LSH is Upregulated by the LRP6-GSK3β-E2F1 Axis Linking Reversely with Survival in Gliomas.

The signaling pathway-based stratification in chromatin modification could predict clinical outcome more reliably than morphology-alone-based classification schemes in gliomas. Here we reported a role of the chromatin-remodeling factor lymphoid-specific helicase (LSH) in gliomas. Among astrocytomas of grade I to III and glioblastoma of grade IV, LSH were almost completely expressed in all cases, and strongly correlated with astrocytomas progression and poor prognosis of patients with astrocytomas and glioblastoma. Ectopic expression of LSH promoted tumor formation. Up-regulation of transcription factor E2F1 in astrocytomas and glioblastoma was associated with the progression of gliomas and correlated with LSH expression. Chromatin immunoprecipitation (ChIP) analysis showed transcription factor E2F1 were recruited to the promoter region of LSH, and depletion of E2F1 decreased LSH expression and cell growth. Moreover, glycogen synthase kinase-3β (GSK-3β), an intact complex of E2F1, were also highly expressed in astrocytomas and linked with astrocytomas progression and poor prognosis of patients with astrocytomas and glioblastoma. Inhibition of GSK3β increased the enrichment of E2F1 to the LSH promoter, in turn, increased LSH expression. Lipoprotein receptor-related protein 6 (LRP6), an upstream regulator of GSK3β signaling pathway, was highly expressed in gliomas. Knockdown of LRP6 decreased LSH expression through decrease of recruitment of E2F1 to the LSH promoter leading to inhibition of cell growth. Taken together, this study reveals evidence demonstrating a mechanism by which upregulated promoted gliomas. A mechanistic link between LSH expression and activation of the LPR6/ GSK3β/E2F1 axis in gliomas illustrates a novel role of LSH in malignant astrocytomas and glioblastoma.

EGLN1/c-Myc Induced Lymphoid-Specific Helicase Inhibits Ferroptosis through Lipid Metabolic Gene Expression Changes

Ferroptosis is a newly discovered form of non-apoptotic cell death in multiple human diseases. However, the epigenetic mechanisms underlying ferroptosis remain poorly defined. First, we demonstrated that lymphoid-specific helicase (LSH), which is a DNA methylation modifier, interacted with WDR76 to inhibit ferroptosis by activating lipid metabolism-associated genes, including GLUT1, and ferroptosis related genes SCD1 and FADS2, in turn, involved in the Warburg effect. WDR76 targeted these genes expression in dependent manner of LSH and chromatin modification in DNA methylation and histone modification. These effects were dependent on iron and lipid reactive oxygen species. We further demonstrated that EGLN1 and c-Myc directly activated the expression of LSH by inhibiting HIF-1α. Finally, we demonstrated that LSH functioned as an oncogene in lung cancer in vitro and in vivo. Therefore, our study elucidates the molecular basis of the c-Myc/EGLN1-mediated induction of LSH expression that inhibits ferroptosis, which can be exploited for the development of therapeutic strategies targeting ferroptosis for the treatment of cancer.

Decrease in Lymphoid Specific Helicase and 5-hydroxymethylcytosine Is Associated with Metastasis and Genome Instability

DNA methylation is an important epigenetic modification as a hallmark in cancer. Conversion of 5-methylcytosine (5-mC) to 5-hydroxymethylcytosine (5-hmC) by ten-eleven translocation (TET) family enzymes plays an important biological role in embryonic stem cells, development, aging and disease. Lymphoid specific helicase (LSH), a chromatin remodeling factor, is regarded as a reader of 5-hmC. Recent reports show that the level of 5-hmC is altered in various types of cancers. However, the change in 5-hmC levels in cancer and associated metastasis is not well defined. We report that the level of 5-hmC was decreased in metastatic tissues of nasopharyngeal carcinoma, breast cancer, and colon cancer relative to that in non-metastasis tumor tissues. Furthermore, our data show that TET2, but not TET3, interacted with LSH, whereas LSH increased TET2 expression through silencing miR-26b-5p and miR-29c-5p. Finally, LSH promoted genome stability by silencing satellite expression by affecting 5-hmC levels in pericentromeric satellite repeats, and LSH was resistant to cisplatin-induced DNA damage. Our data indicate that 5-hmC might serve as a metastasis marker for cancer and that the decreased expression of LSH is likely one of the mechanisms of genome instability underlying 5-hmC loss in cancer.

Nuclear EGFR-PKM2 axis induces cancer stem cell-like characteristics in irradiation-resistant cells

Radiation therapy has become an important tool in the treatment of cancer patients, but most patients relapse within 5 years. Relapse is due to the presence of cancer stem cells (CSCs), but the molecular mechanism of radioresistance in CSCs remains largely elusive. Here, we found that irradiation-resistant (IR) cells exhibited increased stem cell-like properties together with elevated anchorage-independent growth and metastasis ability. EGFR not only leads to increased acquisition of endometrial cancer stem cell markers in radioresistant sublines but is critical for the cancer stem-cell phenotype and tumorigenicity. Moreover, PKM2 functions as an interacting partner of EGFR, which induces the EMT phenotype and stem cell-like properties in IR cells. Finally, we found that the regulatory function of the EGFR-PKM2 axis is dependent on nuclear EGFR. In sum, our study indicated that EGFR and PKM2 directly interact and bind with each other to regulate the transcription of stemness-related genes and promote the stem-like phenotype, thus promoting invasion and metastasis.

The value of detecting immunoglobulin gene rearrangements in the diagnosis of B-cell lymphoma

Objective To discuss the clinical value of immunoglobulin gene rearrangements in the diagnosis of B-cell lymphoma. Methods A total of 209 cases of B-cell lymphomas and 35 cases of reactive lymphoid hyperplasia were selected for DNA extraction and PCR amplification using the BIOMED-2 primer system. Gel electrophoresis of heteroduplexes was used to analyze immunoglobulin gene rearrangements. Results A total of 209 cases of B-cell lymphoma, including 69 extranodal marginal zone B-cell lymphomas of mucosa-associated lymphoid tissue, 63 diffuse large B-cell lymphomas, 39 follicular lymphomas, 15 small lymphocytic lymphomas, 6 plasmacytomas, 6 mantle cell lymphomas, 7 nodal marginal zone B-cell lymphomas, and 4 lymphoplasmacytoid lymphomas, were examined. Immunoglobulin gene rearrangements were found in all 209 cases, with 93 IGHA, 122 IGHB, 98 IGHC, 167 IGK, 100 IGL, 167 IGHA/B/C, 204 IGH/IGK, 209 IGH/IGK/IGL, 129 IGH+IGK, 81 IGH+IGL, 83 IGK+IGL and 68 IGH+IGK+IGL gene rearrangements. Immunoglobulin gene rearrangements were not found in the 35 cases of reactive lymphoid hyperplasia. IGH and IGK gene rearrangements were mainly found in mantle cell lymphomas, small lymphocytic lymphomas, extranodal marginal zone B-cell lymphomas of mucosa-associated lymphoid tissue and diffuse large B-cell lymphomas. The IGH gene rearrangement was mainly found in lymphoplasmacytoid lymphomas and follicular lymphomas. IGK and IGL gene rearrangements were mainly found in plasmocytoma, and the IGK gene rearrangement was mainly found in nodal marginal zone B-cell lymphomas. Conclusions The BIOMED-2 standardized immunoglobulin gene rearrangement detection system is an important tool in B-cell lymphoma diagnosis. Analysis of IGH, IGK and IGL gene rearrangements is valuable in confirming the classification of B-cell NHL.