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Dong-Hua Yang

Publications and source records attributed to Dong-Hua Yang.

10 recordsLinked to original sources
PubMed2006

Disabled-2 heterozygous mice are predisposed to endometrial and ovarian tumorigenesis and exhibit sex-biased embryonic lethality in a p53-null background.

Disabled-2 (Dab2) is a phosphoprotein involved in cellular signal transduction and endocytic trafficking. The expression of Dab2 is frequently lost or suppressed in several epithelial tumors, and studies of its cellular function and growth suppressive activity when re-expressed in cancer cells led to the suggestion that Dab2 is a tumor suppressor. A role for Dab2 in epithelial cell positioning organization was derived from study of knockout mice: homozygous deletion of dab2 results in early embryonic lethality due to the disorganization of the primitive endoderm, the first epithelium in early embryos. We now report that dab2 heterozygous mice develop uterine hyperplasia and ovarian preneoplastic morphological changes at a high frequency. Crossing into a p53(-/-) background unexpectedly produced few female dab2(+/-):p53(-/-) mice, while the male dab2(+/-):p53(-/-) were born at the expected Mendelian frequency. The tumor-prone phenotype of dab2(+/-) mice provides additional support for a role of human Dab2 as a tumor suppressor, and the sex-biased embryonic lethality suggests a genetic interaction between p53 and dab2 genes in female mice.

Adaptor Proteins, Signal Transducing↗
PubMed2004

The relationship between point mutation and abnormal expression of c-fms oncogene in hepatocellular carcinoma.

BACKGROUND: Recent research found abnormal expression of the c-fms oncogene, which encodes the macrophage colony-stimulating factor receptor (CSF-1R), in several human carcinomas including hepatocellular carcinoma (HCC). But the relationship between the point mutation and abnormal expressing of c-fms oncogene in HCC was not clear. This study is to investigate the relationship between point mutation and abnormal expression of c-fms oncogene in hepatocellular carcinoma (HCC) and to clarify the mechanism of HCC. METHODS: The expression of c-fms oncogene at different levels of cell, protein and transcription was observed using immune histological ABC, Western blot and Northern blot. PCR-single strand conformation polymorphism and gene sequencing were used to detect the mutation of c-fms in HCC tissues and their surrounding tissues of 30 patients. RESULTS: The expression of c-fms was significantly higher in HCC tissues than in their surrounding tissues (P<0.01). Point mutation of Leu (TTG)-->Ser (TCG) at codon 301 of c-fms amino acids was observed in 21.4% (3/14) HCC tissues. No mutation of c-fms oncogene was detected in the surrounding cancerous tissues. CONCLUSION: Point mutation at codon 301 of c-fms oncogene is one of the mechanisms of abnormal over-expression in HCC.

Adult↗
PubMed2004

[Relationship between alterations of p16INK4a and p14ARF genes of CDKN2A locus and gastric carcinogenesis].

OBJECTIVE: To investigate the relationship between alterations of p16INK4a and p14ARF genes and gastric carcinogenesis. METHODS: Tumors and gastric tissues neighboring carcinoma from 48 patients with gastric cancer were studied. Homozygous deletion, mutation, methylation of the CpG islands, mRNA expression of p16INK4a and p14ARF genes were assessed by polymerase chain reaction (PCR), PCR-single strand conformation polymorphism (SSCP), PCR based methylation assay, and reverse transcription (RT)-PCR. RESULTS: (1) The overall homozygous deletion rate of p16INK4a and p14ARF was 35.4% (17/48), and no homozygous deletion was examined in all the gastric tissues neighboring tumor. (2) There was no point mutation of p16INK4a and p14ARF in 31 gastric cancers without homozygous deletion and in the matched gastric tissues adjacent to tumor. (3) Methylation of the CpG islands of p16INK4a and p14ARF was detected in 47.9% (23/48) of gastric cancers, while methylation was observed only in 2 of 48 gastric tissues neighboring cancers with a significant difference (P <0.01). (4) The rate of p16INK4a mRNA loss was 47.9% (23/48) in gastric cancer, and the cases of combined methylation of exons 1alpha and 2 had a higher loss rate (100%, 6/6) of p16INK4a mRNA than those of methylation form the other exons (11.8%, 2/17) (P <0.01). The loss rate of p14ARF mRNA was 45.8% (22/48) in gastric cancer, and patients with combined methylation of exons 1beta and 2 had a higher loss rate (100%, 3/3) of p14ARF mRNA than those of the methylation from the other exons (15%, 3/20) (P < 0.05). (5) The combined loss of p16INK4a and p14ARF mRNAs was examined in 1 (5.6%) of 18 cases of well and moderately-differentiated carcinomas, and 11 (36.7%) of 30 cases of poorly and not-differentiated carcinomas with significant difference (P <0.05). CONCLUSION: p16INK4a and p14ARF genes were frequently inactivated by homozygous deletion and methylation of the 5' CpG islands in gastric cancer, which might have played an important role in the development of gastric cancer.

Adenocarcinoma↗
PubMed2003

Loss of surface and cyst epithelial basement membranes and preneoplastic morphologic changes in prophylactic oophorectomies.

BACKGROUND: The authors suggested that the loss of collagen IV and laminin-containing basement membrane and the loss of Disabled-2 (Dab2) expression were two critical events associated with morphologic dysplastic changes of the ovarian surface epithelium as a step in tumorigenicity. Both the basement membrane and Dab2, a candidate tumor suppressor of ovarian carcinoma, were involved in epithelial cell surface positioning and organization. The authors speculated that the purging of the basement membrane may be similar to the proteolysis during gonadotropin-stimulated ovulation, a cyclooxygenase 2 (Cox-2)-mediated process. METHODS: Prophylactic oophorectomy is used to prevent breast and ovarian carcinoma in high-risk populations. These ovarian tissue specimens often contain an increased presence of morphologically abnormal lesions that are believed to be preneoplastic. The authors evaluated archived prophylactic oophorectomy specimens to verify whether the loss of Dab2 expression and the removal of the basement membrane that occur at the ovarian surface and inclusion cyst epithelia are molecular markers of preneoplastic lesions. Of the 36 samples containing identifiable ovarian surface epithelial components on slides, immunostaining was employed to evaluate the intactness of the basement membrane (periodic acid-Schiff [PAS], collagen IV, and laminin) and the expression of Dab2 and Cox-2. Expression of Cox-1 and Cox-2 also were evaluated in cultured ovarian surface epithelial cells prepared from ovarian tissue specimens removed from patients who underwent prophylactic surgery. RESULTS: The morphologically normal ovarian surface epithelium typically contained a collagen IV- and laminin-positive basement membrane, which also was detected by PAS staining. Many morphologically altered areas, such as papillomatosis, invaginations, inclusion cysts, stratification, adenomas, and microscopic adenocarcinomas, were found in these specimens. Both the morphologically altered and adjacent morphologically normal epithelia consistently exhibited loss of basement membrane and/or Dab2 expression and an increase in Cox-2 staining. Frequently, an increase in Cox-2 staining was correlated with the loss of epithelial basement membrane in morphologically normal areas. CONCLUSIONS: The loss of Dab2 and basement membrane and the overexpression of Cox-2 were observed in presumptive neoplastic precursor areas of oophorectomy specimens obtained from a population at high risk for ovarian carcinoma. Transient loss of collagen IV and laminin in the basement membrane of the preneoplastic epithelium and the loss of Dab2 expression are common early events associated with morphologic alteration and tumorigenicity of the ovarian surface epithelium. The authors concluded that Cox-2 overexpression may play a role in the purging of basement membrane of the ovarian surface epithelium, mimicking the process of ovulation. Further experiments may be able to test the hypothetical model derived from these histologic observations.

Adaptor Proteins, Signal Transducing↗
PubMed2002

Disabled-2 is essential for endodermal cell positioning and structure formation during mouse embryogenesis.

The signal transduction adapter protein Disabled-2 (Dab2) is one of the two mammalian orthologs of the Drosophila Disabled. The brain-specific Disabled-1 (Dab1) functions in positional organization of brain cells during development. Dab2 is widely distributed and is highly expressed in many epithelial cell types. The dab2 gene was interrupted by in-frame insertion of beta-galactosidase (LacZ) in embryonic stem cells and transgenic mice were produced. Dab2 expression was first observed in the primitive endoderm at E4.5, immediately following implantation. The homozygous Dab2-deficient mutant is embryonic lethal (earlier than E6.5) due to defective cell positioning and structure formation of the visceral endoderm. In E5.5 dab2 (-/-) conceptus, visceral endoderm-like cells are present in the deformed primitive egg cylinder; however, the visceral endoderm cells are not organized, the cells of the epiblast have not expanded, and the proamniotic cavity fails to form. Disorganization of the visceral endodermal layer is evident, as cells with positive visceral endoderm markers are scattered throughout the dab2 (-/-) conceptus. Only degenerated remains were observed at E6.5 for dab2 (-/-) embryos, and by E7.5, the defective embryos were completely reabsorbed. In blastocyst in vitro culture, initially cells with characteristics of endoderm, trophectoderm, and inner cell mass were observed in the outgrowth of the hatched dab2 (-/-) blastocysts. However, the dab2 (-/-) endodermal cells are much more dispersed and disorganized than those from wild-type blastocysts, the inner cell mass fails to expand, and the outgrowth degenerates by day 7. Thus, Dab2 is required for visceral endodermal cell organization during early mouse development. The absence of an organized visceral endoderm in Dab2-deficient conceptus leads to the growth failure of the inner cell mass. We suggest that Dab2 functions in a signal pathway to regulate endodermal cell organization using endocytosis of ligands from the blastocoel cavity as a positioning cue.

Adaptor Proteins, Signal Transducing↗
PubMed2002

Dynamic alterations of the extracellular environment of ovarian surface epithelial cells in premalignant transformation, tumorigenicity, and metastasis.

BACKGROUND: Ovarian surface epithelial cells are positionally organized as a single cell layer by a sheet of basement membrane. It is believed that the contact of the ovarian surface epithelial cells with the basement membrane regulates cell growth and ensures the organization of the epithelium. Disabled-2 (Dab2), a signal transduction protein and a candidate tumor suppressor of ovarian carcinoma, functions in positional organization of ovarian surface epithelial cells. In ovarian carcinomas, genetic and epigenetic changes enable the tumor cells to escape positional control and proliferate in a disorganized fashion. Alterations in the extracellular environment may also be critical for tumor initiation and progression. METHODS: We analyzed and compared the presence of collagen IV and laminin, the scaffold proteins of the basement membrane, and Dab2 in 50 ovarian tumors that are restricted to the ovaries and in 50 metastases of ovarian tumors by immunohistochemistry. Expression of collagen IV, laminin, and Dab2 was also analyzed by Northern blotting in a panel of human ovarian surface epithelial and cancer cell lines. RESULTS: The basement membrane is often absent in morphologically benign ovarian surface and cyst epithelium and low-grade tumors and collagen IV and laminin are absent in the extracellular matrix of most of the primary tumors tested. Of the 50 ovarian tumors confined to the ovaries, 6% (3 of 50) were collagen IV positive and 24% (12 of 50) were laminin positive tumors. Of the 50 metastatic tumors, 16% (8 of 50) are collagen IV positive and 86% (43 of 50) are laminin positive. In addition, even in the metastatic ovarian tumors that are largely collagen IV negative, there are pockets of local areas in which the tumor cells are surrounded by collagen IV-positive staining. Dab2 is absent in the majority of ovarian tumors found in both ovaries and metastatic sites. In both nontumorigenic human ovarian surface epithelial and cancer cell lines, collagen IV, laminin, and Dab2 are expressed aberrantly. CONCLUSIONS: Loss of the basement membrane may be an early event in the preneoplastic transformation of ovarian surface epithelium and in the early stages of tumorigenesis before tumor invasion and metastasis. The majority of primary ovarian tumors examined lack collagen IV and laminin in their extracellular matrix. However, expression of laminin is restored in the majority of metastatic tumors. Reexpression of collagen IV may also contribute to tumor metastasis. The ability of tumor cells to dynamically alter the expression of collagen IV and laminin may facilitate the shedding of cancer cells into the peritoneal spaces and subsequent attachment to the metastatic sites. We propose that loss of collagen IV and laminin may be an initial event in ovarian tumorigenicity and that restoration of collagen IV and laminin expression in the later stages of tumor development may promote metastasis of ovarian tumors.

Adaptor Proteins, Signal Transducing↗
PubMed2002

Ras/MAPK pathway confers basement membrane dependence upon endoderm differentiation of embryonic carcinoma cells.

The formation of extraembryonic endoderm is one of the earliest steps in the differentiation of pluripotent cells of the inner cell mass during the early stages of embryonic development. The primitive endoderm cells and the derived parietal and visceral endoderm cells gain the capacity to produce collagen IV and laminin. The deposition of these components results in the formation of basement membrane and epithelium of the endoderm, with polarized cells covering the inner surface of the blastocoels. We used retinoic acid-induced endoderm differentiation of stem cell-like F9 embryonic carcinoma cells to study the role of the Ras pathway and its regulation in the formation of the visceral endoderm. Upon endoderm differentiation of F9 cells induced by retinoic acid, c-Fos expression, the downstream target of the Ras pathway, is suppressed by uncoupling Elk-1 phosphorylation/activation to MAPK activity. However, attachment to matrix gel greatly enhances the activation of MAPK in endoderm cells but not in undifferentiated F9 cells. Enhanced MAPK activation as a result of contact with basement membrane is able to compensate for reduced Elk-1 phosphorylation and c-Fos expression. We conclude that endoderm differentiation renders the activation of the Ras pathway basement membrane dependent, contributing to the epithelial organization of the visceral endoderm.

Animals↗
PubMed2002

Molecular events associated with dysplastic morphologic transformation and initiation of ovarian tumorigenicity.

BACKGROUND: Disabled-2 (Dab2), a candidate tumor suppressor of ovarian carcinoma, frequently (around 80%) loses its expression in ovarian tumors. Expression of exogenous Dab2 in tumor cell lines negatively regulates growth and suppresses the downstream signal of the Ras/mitogen activated protein kinase mitogenic pathway. The inactivation of Dab2 is believed to be an early event in ovarian tumorigenicity. METHODS: The authors analyzed the correlation among expression of Dab2, presence of basement membrane (collagen IV and laminin), morphologic alteration of the surface epithelial cells, and expression of the mitotic index marker Mib-1 in 50 archived ovarian tumors by an immunohistochemical approach. The stainings of Dab2, Mib-1, collagen IV, and laminin in premalignant lesions bordering both normal and neoplastic ovarian surface epithelium from adjacent slides were analyzed in 50 ovarian tumors. RESULTS: In these 50 ovarian tumors, the percentage of Mib-1 positive tumor cells distributed in a wide range, from 1% to 75%, and there has no strong correlation with the expression of Dab2. However, in the premalignant regions bordering tumor and normal ovarian surface epithelium, the loss of Dab2 expression closely correlated with the dysplastic morphologic transition and Mib-1 expression of the ovarian surface epithelial cells. In 20 foci in 12 out of the 50 tumors, a transition from normal to neoplastic morphology within a contiguous epithelium was observed, and in all cases the morphologic change correlated with the loss of Dab2 staining. In addition, the collagen and laminin staining of the basement membrane were absent or weakened in pre-malignant epithelium prior to loss of Dab2 expression in all these 20 cases. Nevertheless, collagen IV and laminin were detectable in established adenomas on the same tumor slides. CONCLUSIONS: The loss of Dab2 is closely associated with the transition of ovarian surface epithelial cells to premalignant states and is likely involved in the initiation of ovarian tumorigenicity. Transient loss of collagen IV and laminin in the basement membrane of the premalignant epithelium and subsequent inactivation of Dab2 are common early events associated with tumorigenicity of the ovarian surface epithelium.

Adaptor Proteins, Signal Transducing↗
PubMed2001

Construction of single-chain Fv library against hepatocellular carcinoma.

OBJECTIVE: To construct a phage display single-chain Fv (ScFv) library against hepatocellular carcinoma (HCC). METHODS: The mRNA extracted from the spleen cells of immunized BALB/C mice was purified and reverse transcriptase-polymerase chain reaction (RT-PCR) was employed for the seperate amplification of the gene fragments encoding the heavy- and light-chain variable regions respectively, which were subsequently assembled into ScFv gene. Amplification of the resultant ScFv gene was performed before it was introduced in to E.coli TG1 via a phagemid vector pCANTAB5E. A proportion of the transformed cells was loaded onto SOBAG plates and incubated and the number of bacterial colonies counted. PCR, nucleotides sequence analysis and enzyme-linked immunosorbent assay (ELISA) were performed to evaluate the constructed ScFV library. RESULT: The phage display ScFv library had a capacity of approximately 2.14x106, with 90% of the phagemids containing ScFv gene insertion as demonstrated by PCR. The nucleotides sequence of ScFv gene was approved, and ELISA showed that the ScFv library could specifically conjugate with HCC antigen. CONCLUSION: The phage display ScFv library against HCC is successfully constructed, which may facilitate the acquisition of special antibodies and may be instrumental in the research and clinical management of HCC.

Journal Article↗