Liang Yi Hung

Nuclear epidermal growth factor receptor (EGFR) interacts with signal transducer and activator of transcription 5 (STAT5) in activating Aurora-A gene expression

Loss of the maintenance of genetic material is a critical step leading to tumorigenesis. It was reported that overexpression of Aurora-A and the constitutive activation of the epidermal growth factor (EGF) receptor (EGFR) are implicated in chromosome instability. In this study, we examined that when cells treated with EGF result in centrosome amplification and microtubule disorder, which are critical for genetic instability. Interestingly, the expression of Aurora-A was also increased by EGF stimulus. An immunofluorescence assay indicated that EGF can induce the nuclear translocation of EGFR. Chromatin immunoprecipitation (ChIP) and re-ChIP assays showed significant EGF-induced recruitment of nuclear EGFR and signal transducer and activator of transcription 5 (STAT5) to the Aurora-A promoter. A co-immunoprecipitation assay further demonstrated that EGF induces nuclear interaction between EGFR and STAT5. A small interfering (si)RNA knockdown assay also showed that EGFR and STAT5 are indeed involved in EGF-increased Aurora-A gene expression. Altogether, this study proposes that the nuclear EGFR associates with STAT5 to bind and increase Aurora-A gene expression, which ultimately may lead to chromosome instability and tumorigenesis. The results also provide a novel linkage between the EGFR signaling pathway and overexpression of Aurora-A in tumorigenesis and chromosome instability.

Nucleolin regulates c-Jun/Sp1-dependent transcriptional activation of cPLA2α in phorbol ester-treated non-small cell lung cancer A549 cells

The expression of cPLA2 is critical for transformed growth of non-small cell lung cancer (NSCLC). It is known that phorbol 12-myristate 13-acetate (PMA)-activated signal transduction pathway is thought to be involved in the oncogene action in NSCLC and enzymatic activation of cPLA2. However, the transcriptional regulation of cPLA2α in PMA-activated NSCLC is not clear. In this study, we found that PMA induced the mRNA level and protein expression of cPLA2α. In addition, two Sp1-binding sites of cPLA2α promoter were required for response to PMA and c-Jun overexpression. Small interfering RNA (siRNA) of c-Jun and nucleolin inhibited PMA induced the promoter activity and protein expression of cPLA2α. Furthermore, PMA stimulated the formation of c-Jun/Sp1 and c-Jun/nucleolin complexes as well as the binding of these transcription factor complexes to the cPLA2α promoter. Although Sp1-binding sites were required for the bindings of Sp1 and nucleolin to the promoter, the binding of nucleolin or Sp1 to the promoter was independent of each other. Our results revealed that c-Jun/nucleolin and c-Jun/Sp1 complexes play an important role in PMA-regulated cPLA2α gene expression. It is likely that nucleolin binding at place of Sp1 on gene promoter could also mediate the regulation of c-Jun/Sp1-activated genes.

Combined Erdheim-Chester disease and Langerhans cell histiocytosis of skin are both monoclonal: A rare case with human androgen-receptor gene analysis

BACKGROUND Erdheim-Chester disease (ECD) is a rare xanthogranulomatous histiocytic disorder. Langerhans cell histiocytosis (LCH) is a proliferative disorder of histiocytes with a phenotype similar to dendritic Langerhans cells. Both are derived from myeloid stem cells in the bone marrow and, thus, can overlap. OBJECTIVE We report a rare case of hybrid LCH and ECD of the skin with systemic ECD. METHODS Pathologic examinations and human androgen-receptor gene assay were used to study this case. RESULTS A 34-year-old woman presented with recurrent ulcerative skin lesions on both thighs associated with polydipsia and polyuria since childhood. Radiography revealed osteosclerosis of bilateral distal tibias and soft tissue masses of bilateral chest walls and ankles. Pathologically, the chest wall lesions showed dense aggregates of lipid-laden histiocytes, which were CD68(+)/CD163(+)/S100(-)/CD1a(-). Combined with the clinical and radiographic findings, this xanthogranulomatous infiltrate was consistent with ECD. However, thigh skin showed discrete foci of a xanthogranulomatous infiltrate and S100(+)/CD1a(+) Langerhans cells with eosinophils. In addition, Birbeck granules were found. Dissected tissues from both ECD and LCH were monoclonal, supporting their neoplastic nature. LIMITATIONS Single case report is a limitation. CONCLUSION ECD and LCH may have a close association with divergent differentiation from the same stem cells under different microenvironmental conditions.

Monoclonality and cytogenetic abnormalities in hyaline vascular Castleman disease

Hyaline vascular Castleman disease is traditionally regarded as a reactive hyperplastic process. Occasional cases, however, have been reported with cytogenetic anomalies bringing this concept into question. In this study, we used conventional and methylation-specific polymerase chain reaction methods to assess the human androgen receptor α (HUMARA) gene in 29 female patients with hyaline vascular Castleman disease and compared the results with three cases of plasma cell Castleman disease and 20 cases of age-matched lymphoid hyperplasia. We also assessed for immunoglobulin gene and T-cell receptor gene rearrangements, and conventional cytogenetic analysis was performed in three cases of hyaline vascular Castleman disease. In cases with informative results, conventional and methylation-specific human androgen receptor α gene analyses yielded a monoclonal pattern in 10 of 19 (53%) and 17 of 23 (74%) cases of hyaline vascular Castleman disease, respectively. A monoclonal pattern was also detected in three cases of plasma cell Castleman disease but not in cases of lymphoid hyperplasia. The frequency of monoclonality was higher for lesions >5 cm in size (100%) and for the stromal-rich variant (91%). Cytogenetic abnormalities in stromal cells were revealed in two cases of hyaline vascular Castleman disease and no cases showed monoclonal immunoglobulin or T-cell receptor gene rearrangements. Follow-up data showed persistent disease in 4 of 23 (17%) patients. We conclude that hyaline vascular Castleman disease is often a monoclonal proliferation, most likely of lymph node stromal cells.

58-kDa Microspherule Protein (MSP58) Is Novel Brahma-related Gene 1 (BRG1)-associated Protein That Modulates p53/p21 Senescence Pathway

Background: The nucleolar MSP58 protein is a candidate oncogene implicated in cellular transformation. Results: MSP58 is associated with BRG1 and induces cellular senescence through the p53/p21 pathway. Conclusion: MSP58 has both tumor-suppressing and -promoting functions. Significance: This work reveals a novel role for MSP58 in cellular senescence and suggests that MSP58 may have further prognostic and therapeutic implications. The nucleolar 58-kDa microspherule protein (MSP58) protein is a candidate oncogene implicated in modulating cellular proliferation and malignant transformation. In this study, we show that knocking down MSP58 expression caused aneuploidy and led to apoptosis, whereas ectopic expression of MSP58 regulated cell proliferation in a context-dependent manner. Specifically, ectopic expression of MSP58 in normal human IMR90 and Hs68 diploid fibroblasts, the H184B5F5/M10 mammary epithelial cell line, HT1080 fibrosarcoma cells, primary mouse embryonic fibroblasts, and immortalized NIH3T3 fibroblasts resulted in induction of premature senescence, an enlarged and flattened cellular morphology, and increased senescence-associated β-galactosidase activity. MSP58-driven senescence was strictly dependent on the presence of functional p53 as revealed by the fact that normal cells with p53 knockdown by specific shRNA or cells with a mutated or functionally impaired p53 pathway were effective in bypassing MSP58-induced senescence. At least two senescence mechanisms are induced by MSP58. First, MSP58 activates the DNA damage response and p53/p21 signaling pathways. Second, MSP58, p53, and the SWI/SNF chromatin-remodeling subunit Brahma-related gene 1 (BRG1) form a ternary complex on the p21 promoter and collaborate to activate p21. Additionally, MSP58 protein levels increased in cells undergoing replicative senescence and stress-induced senescence. Notably, the results of analyzing expression levels of MSP58 between tumors and matched normal tissues showed significant changes (both up- and down-regulation) in its expression in various types of tumors. Our findings highlight new aspects of MSP58 in modulating cellular senescence and suggest that MSP58 has both oncogenic and tumor-suppressive properties.

Aberrantly expressed AURKC enhances the transformation and tumourigenicity of epithelial cells

Over‐expression of AURKC has been detected in human colorectal cancers, thyroid carcinoma and several cancer cell lines. However, the regulation and clinical implications of over‐expressed AURKC in cancer cells are unclear. Here we show that elevated AURKC increases the proliferation, transformation and migration of cancer cells. Importantly, the kinase activity of AURKC is required for these tumour‐associated properties. Analysis of human cancer specimens shows that the expression of AURKC is increased in cervical cancer, and is highly correlated with staging in colorectal cancer. Over‐expressed AURKC‐GFP localizes to the centromeric regions of mitotic chromosomes and results in a decreased level of AURKB, a key regulator of spindle checkpoint. Expression of AURKC is down‐regulated by PLZF, a transcriptional repressor, through recruitment to its promoter region. The expression levels of PLZF and AURKC mRNA display opposite patterns in human cervical and colorectal cancers. Taken together, our results provide important insights into human cancers with AURKC expression, which may serve as a potential target for cancer therapy in the future. Copyright

Translational up-regulation of Aurora-A in EGFR-overexpressed cancer.

Abnormal expression of Aurora‐A and epidermal growth factor receptor (EGFR) is observed in different kinds of cancer and associated with poor prognosis in cancer patients. However, the relationship between Aurora‐A and EGFR in tumour development was not clear. In previous reports, we found that EGFR translocates to nucleus to activate Aurora‐A expression after EGF treatment in EGFR‐overexpressed cells. However, we also observed that not all the EGFR‐overexpressed cells have the nuclear EGFR pathway to mediate the Aurora‐A expression. In this study, we demonstrated that EGF signalling increased the Aurora‐A protein expression in EGFR‐overexpressed colorectal cancer cell lines via increasing the translational efficiency. In addition, the overexpression of EGFR was also associated with higher expression of Aurora‐A in clinical colorectal samples. Activation of the PI3K/Akt/mTOR and MEK/ERK pathways mediated the effect of EGF‐induced translational up‐regulation. Besides, only the splicing variants containing exon 2 of Aurora‐A mRNA showed increased interaction with the translational complex to synthesize Aurora‐A protein under EGF stimulus. Besides, the exon 2 containing splicing variants were the major Aurora‐A splicing forms expressed in human colorectal cancers. Taken together, our results propose a novel regulatory mechanism for the abnormal expression of Aurora‐A in EGFR‐overexpressed cancers, and highlight the importance of alternative 5′‐UTR splicing variants in regulating Aurora‐A expression. Furthermore, the specific expression of exon 2 containing splicing variants in cancer tissues may serve as a potential target for cancer therapy in the future.

CCAAT/Enhancer-binding Protein δ Mediates Tumor Necrosis Factor α-induced Aurora Kinase C Transcription and Promotes Genomic Instability

Epidemiologic and clinical research indicates that chronic inflammation increases the risk of certain cancers, possibly through chromosomal instability. However, the mechanism of inflammation-dependent chromosomal instability associated with tumorigenesis is not well characterized. The transcription factor CCAAT/enhancer-binding protein δ (C/EBPδ, CEBPD) is induced by tumor necrosis factor α (TNFα) and expressed in chronically inflamed tissue. In this study, we show that TNFα promotes aneuploidy. Loss of CEBPD attenuated TNFα-induced aneuploidy, and CEBPD caused centromere abnormality. Additionally, TNFα-induced CEBPD expression augmented anchorage-independent growth. We found that TNFα induced expression of aurora kinase C (AURKC) through CEBPD, and that AURKC also causes aneuploidy. Furthermore, high CEBPD expression correlated with AURKC expression in inflamed cervical tissue specimens. These data provide insight into a novel function for CEBPD in inducing genomic instability through the activation of AURKC expression in response to inflammatory signals.

Analysis of the interaction between Zinc finger protein 179 (Znf179) and promyelocytic leukemia zinc finger (Plzf)

BackgroundZinc finger protein 179 (Znf179), also known as ring finger protein 112 (Rnf112), is a member of the RING finger protein family and plays an important role in neuronal differentiation. To investigate novel mechanisms of Znf179 regulation and function, we performed a yeast two-hybrid screen to identify Znf179-interacting proteins.ResultsUsing a yeast two-hybrid screen, we have identified promyelocytic leukemia zinc finger (Plzf) as a specific interacting protein of Znf179. Further analysis showed that the region containing the first two zinc fingers of Plzf is critical for its interaction with Znf179. Although the transcriptional regulatory activity of Plzf was not affected by Znf179 in the Gal4-dependent transcription assay system, the cellular localization of Znf179 was changed from cytoplasm to nucleus when Plzf was co-expressed. We also found that Znf179 interacted with Plzf and regulated Plzf protein expression.ConclusionsOur results showed that Znf179 interacted with Plzf, resulting in its translocation from cytoplasm to the nucleus and increase of Plzf protein abundance. Although the precise nature and role of the Znf179-Plzf interaction remain to be elucidated, both of these two genes are involved in the regulation of neurogenesis. Our finding provides further research direction for studying the molecular functions of Znf179.

Ran GTPase-Activating Protein 1 Is a Therapeutic Target in Diffuse Large B-Cell Lymphoma

Lymphoma-specific biomarkers contribute to therapeutic strategies and the study of tumorigenesis. Diffuse large B-cell lymphoma (DLBCL) is the most common type of malignant lymphoma. However, only 50% of patients experience long-term survival after current treatment; therefore, developing novel therapeutic strategies is warranted. Comparative proteomic analysis of two DLBCL lines with a B-lymphoblastoid cell line (LCL) showed differential expression of Ran GTPase-activating protein 1 (RanGAP1) between them, which was confirmed using immunoblotting. Immunostaining showed that the majority of DLBCLs (92%, 46/50) were RanGAP1+, while reactive lymphoid hyperplasia (n = 12) was RanGAP1+ predominantly in germinal centers. RanGAP1 was also highly expressed in other B-cell lymphomas (BCL, n = 180) with brisk mitotic activity (B-lymphoblastic lymphoma/leukemia: 93%, and Burkitt lymphoma: 95%) or cell-cycle dysregulation (mantle cell lymphoma: 83%, and Hodgkin’s lymphoma 91%). Interestingly, serum RanGAP1 level was higher in patients with high-grade BCL (1.71 ± 2.28 ng/mL, n = 62) than in low-grade BCL (0.75 ± 2.12 ng/mL, n = 52) and healthy controls (0.55 ± 1.58 ng/mL, n = 75) (high-grade BCL vs. low-grade BCL, p = 0.002; high-grade BCL vs. control, p < 0.001, Mann-Whitney U test). In vitro, RNA interference of RanGAP1 showed no effect on LCL but enhanced DLBCL cell death (41% vs. 60%; p = 0.035) and cell-cycle arrest (G0/G1: 39% vs. 49%, G2/M: 19.0% vs. 7.5%; p = 0.030) along with decreased expression of TPX2 and Aurora kinases, the central regulators of mitotic cell division. Furthermore, ON 01910.Na (Estybon), a multikinase inhibitor induced cell death, mitotic cell arrest, and hyperphosphorylation of RanGAP1 in DLBCL cell lines but no effects in normal B and T cells. Therefore, RanGAP1 is a promising marker and therapeutic target for aggressive B-cell lymphoma, especially DLBCL.