Biomedical subjects

W Xia

Publications and source records attributed to W Xia.

At least 19 recordsLinked to original sources

PubMed2001

Targeting HER-2/neu-overexpressing breast cancer cells by an antisense iron responsive element-directed gene expression.

Overexpression of HER-2/neu proto-oncogene is found in many human cancers including 20-30% of breast cancer and is a predictor of poor prognosis. To target breast cancer cells that overexpress HER-2/neu mRNA, we previously described a novel strategy that combines the principle of antisense (AS) and translational inhibitory activity conferred by an iron-responsive element (IRE) (AS-IRE). Here, we showed that three potential AS-IREs, i.e. AS-IRE1, 4, and 5, derived from HER-2/neu antisense sequence could bind endogenous iron regulatory protein (IRP) and, when placed in 5' untranslated region (5'UTR) of a reporter gene, the gene expression could be translationally repressed by recombinant IRP in vitro. Using AS-IRE4 as our model, we demonstrated that it is regulated by iron, and importantly, such regulation is impaired in HER-2/neu-overexpressing breast cancer cells. Furthermore, we showed that AS-IRE4 could preferentially direct the expression of a reporter gene in HER-2/neu-overexpressing breast cancer cells. Interestingly, when AS-IRE4 was placed in 5'UTR of Bax gene, a pro-apoptotic protein in the Bcl-2 protein family, we observed a preferential cell killing in breast cancer cells that overexpress HER-2/neu. Taken together, our results suggest that AS-IRE behaves as a functional IRE and it may direct therapeutic gene expression to preferentially target HER-2/neu-overexpressing breast cancer cells.

Antisense Elements (Genetics)↗

PubMed2001

Subcellular localization of presenilin 2 endoproteolytic C-terminal fragments.

Mutations in the genes that encode the presenilin 1 and 2 (PS1 and PS2) proteins cause the majority of familial Alzheimer's disease (FAD). Differential cleavage of the presenilins results in a generation of at least two C-terminal fragments (CTFs). An increase in the smaller of these two CTFs is one of the few changes in presenilin processing associated with FAD mutations in both PS1 and PS2. Interestingly, the phosphorylation of PS2 modulates the production of the smaller, caspase-derived PS2 CTF, which indicates that the generation of this fragment is a regulated, physiologic event. To date, there is no data concerning the subcellular distribution of the caspase-derived PS2 CTF. Because this fragment is normally present at levels that are difficult to detect, we have used cell lines in which the production of wild-type or N141I mutant PS2 is controlled by a tetracycline-regulated promoter in order to assess the subcellular localization of the caspase CTF in relation to the larger, constitutive PS2 CTF and to PS2 holoprotein. We have found that when levels of PS2 are low, the constitutive CTF colocalizes with markers consistent with localization in the early Golgi-ER-Golgi intermediate compartment (ERGIC) while the caspase CTF colocalizes with markers for the endoplasmic reticulum (ER). Following induction of wild-type or mutant PS2, when the levels of PS2 are high, the primary localization of the constitutive CTF appears to shift from the early Golgi-ERGIC in addition to the ER. Interestingly, while the induction of wild-type PS2 resulted in the localization of the caspase CTF primarily in the ER, the induction of mutant PS2 resulted in the localization of the caspase CTF to both the ER and the early Golgi-ERGIC. In summary, these data suggest that the two presenilin 2 CTFs have different patterns of subcellular localization and that the N141I PS2 mutation alters the localization pattern of the PS2 caspase fragment.

Alzheimer Disease↗

PubMed2001

Self-assembly of novel [3]- and [2]rotaxanes with two different ring components: donor-acceptor and hydrogen bonding interactions and molecular-shuttling behavior.

Three of the first kind of hetero[3]rotaxanes, which comprise one linear component and one neutral and one tetracationic ring component, have been assembled by using the intermolecular hydrogen bonding and donor-acceptor interactions. Three neutral [2]rotaxanes and three tetracationic [2]rotaxanes have also been synthesized as intermediate products or for the sake of property comparison. The linear molecules are incorporated with two glycine subunits, for templating the formation of the neutral tetraamide cyclophane, and one or two hydroquinone subunits, for inducing the formation of the tetracationic cyclophane. Variable-temperature (1)H NMR investigation reveals that the shuttling behavior of the tetracationic ring component along the linear component is substantially influenced by the existence of the neutral ring component. The spatial repelling interaction of the neutral ring on the electron-deficient tetracationic ring simultaneously weakens the latter's "positioning" tendency at both electron-rich hydroquinone sites of the linear component. As a result, the activation energy associated with the shuttling process of the tetracationic ring between the two hydroquinone sites is remarkably reduced in comparison to that of the shuttling process of the corresponding neutral ring-free [2]rotaxanes. For the first time, the rotation of the dipyridinium subunit around the axis formed by the two methylene groups connecting them within the tetracationic cyclophane has been investigated by variable-temperature (1)H NMR spectroscopy and the associated kinetic data have also been successfully obtained. Furthermore, the UV-vis and fluorescent properties of the new [2]- and [3]rotaxanes have been studied. The results demonstrate that [3]rotaxanes with different ring components possess unique kinetic features that are not available in [3]rotaxanes with identical ring components.

Journal Article↗

PubMed2001

DOC-2/hDab-2 inhibits ILK activity and induces anoikis in breast cancer cells through an Akt-independent pathway.

DOC-2/hDab-2 was identified due to the loss of its expression in primary ovarian cancer cells. It is believed that loss of DOC-2/hDab-2 expression is one of the early events of ovarian malignancy. These results suggest a function of DOC-2/hDab-2 as a tumor suppressor. However, it is not clear how DOC-2/hDab-2 negatively regulates cancer cell growth. In this report, we demonstrate that DOC-2/hDab-2 expression in breast cancer cells resulted in sensitivity to suspension-induced cell death (anoikis). This event was associated with the down-regulation of the integrin-linked kinase (ILK) activity. Since ILK is a key factor in regulating the cellular signaling in responding to the extracellular signals through adhesion molecules like integrins, our results indicate that DOC-2/hDab-2 may prevent tumor growth and invasion by modulating the anti-apoptotic ILK pathway.

Adaptor Proteins, Signal Transducing↗

PubMed2001

Cationic liposome-mediated E1A gene transfer to human breast and ovarian cancer cells and its biologic effects: a phase I clinical trial.

PURPOSE: Preclinical studies have demonstrated that the adenovirus type 5 E1A gene is associated with antitumor activities by transcriptional repression of HER-2/neu and induction of apoptosis. Indeed, E1A gene therapy is known to induce regression of HER-2/neu-overexpressing breast and ovarian cancers in nude mice. Therefore, we evaluated the feasibility of intracavitary injection of E1A gene complexed with DC-Chol cationic liposome (DCC-E1A) in patients with both HER-2/neu-overexpressing and low HER-2/neu-expressing breast and ovarian cancers in a phase I clinical trial. PATIENTS AND METHODS: An E1A gene complexed with DCC-E1A cationic liposome was injected once a week into the thoracic or peritoneal cavity of 18 patients with advanced cancer of the breast (n = 6) or ovary (n = 12). RESULTS: E1A gene expression in tumor cells was detected by immunohistochemical staining and reverse transcriptase-polymerase chain reaction. This E1A gene expression was accompanied by HER-2/neu downregulation, increased apoptosis, and reduced proliferation. The most common treatment-related toxicities were fever, nausea, vomiting, and/or discomfort at the injection sites. CONCLUSION: These results argue for the feasibility of intracavitary DCC-E1A administration, provide a clear proof of preclinical concept, and warrant phase II trials to determine the antitumor activity of the E1A gene.

Adenovirus E1A Proteins↗

PubMed2001

The Src-suppressed C kinase substrate, SSeCKS, is a potential metastasis inhibitor in prostate cancer.

The molecular mechanisms leading to prostate cancer remain poorly understood, especially concerning the progression to the metastatic form. SSeCKS, a major protein kinase C substrate with tumor suppressor activity, is likely the rodent orthologue of human Gravin/AKAP12, a scaffolding protein for protein kinases A and C. Gravin was mapped as a single-copy gene to 6q24-25.2, a hotspot for deletion in advanced prostate cancer, and therefore, we investigated the role of SSeCKS/Gravin in prostate oncogenesis. SSeCKS/Gravin protein was detected in untransformed rat and human prostate epithelial cell lines EP12 and PZ-HPV-7, respectively, and in human prostatic epithelium, especially basal epithelial cells. In contrast, SSeCKS/Gravin protein and RNA levels were severely reduced in human (PC-3, PPC-1, LNCaP, DU145, and TSU) and rat Dunning (AT3.1 and MatLyLu) prostate cancer cell lines. The regulated reexpression of SSeCKS in MatLyLu cells induced filopodia-like projections and a decrease in anchorage-independent growth. In nude mice, SSeCKS reexpression slightly decreased primary-site tumor growth but severely decreased the formation of lung metastases. Primary-site tumors that progressed lost regulated SSeCKS reexpression. SSeCKS/Gravin expression was detected in benign human prostatic lesions and well-differentiated carcinomas but not in undifferentiated lesions with Gleason sums > or =6. Our data suggest a role for the loss of SSeCKS/Gravin in the metastatic progression of human prostate cancer.

A Kinase Anchor Proteins↗

PubMed2001

Importance of planar chirality in chiral catalysts with three chiral elements: the role of planar chirality in 2'-substituted 1,1'-P,N-ferrocene ligands on the enantioselectivity in Pd-catalyzed allylic substitution.

A series of novel planar chiral 2'-substituted 1,1'-P,N-ferrocene ligands 9-11, 14, and 16 were prepared with diastereopurity >99:1 and found to be effective in asymmetric allylic alkylation and amination reactions. Ligand 14 furnished the highest enantiomeric excess, 98.5% and 96.5% ee in alkylation and amination reactions, respectively. The role of planar chirality in asymmetric reactions has been examined, and decisive effects on enantioselectivity as well as the control of absolute configuration in palladium-catalyzed allylic alkylation and amination reactions were observed. To clarify why and how the planar chirality governed the stereochemical outcome, X-ray crystallographic structures of eta(3)-diphenylallyl Pd complexes, (1)H NMR, (31)P NMR spectra of palladium dichloride complexes, and eta(3)-diphenylallyl Pd complexes of three 1,1'-P,N-ferrocene ligands were analyzed with the aid of COSY and 2D NOESY experiments. All results led to the conclusion that planar chirality influences the stereochemical outcome by changing or even inverting the ratio of two rotamers because of the steric interaction between a planar chiral group and the coordination site.

Journal Article↗

PubMed2001

Correlation of p27 protein expression with HER-2/neu expression in breast cancer.

Strong expression of human epidermal growth factor receptor 2 (HER-2)/neu in breast cancer has been associated with poor prognosis. Reduced expression of p27(Kip1), a cyclin-dependent kinase inhibitor, correlates with poor clinical outcome in breast cancer. In this study, we provide a correlation between these two important prognostic markers in patients with breast cancer. Breast tumor screening using immunohistochemistry indicated that downregulation of p27 correlated with HER-2/neu overexpression in studying 11 normal breast tissues and 51 primary breast carcinomas. We found HER-2/neu protein overexpression in 20 (41%) of 49 breast cancers and low p27 protein expression in 47 (92%) of 51 breast cancers. All 20 (100%) of the tumors that overexpressed HER-2/neu had low levels of p27 protein product; this correlation was statistically significant (P = 0.035). Decreasing p27 expression correlated with increasing HER-2/neu activity. Our results suggest that one function of the HER-2/neu product is to downregulate p27 expression in breast cancer. This study may be significant in selecting patients for HER-2/neu antibody therapy in the future. Mol. Carcinog. 30:169--175, 2001.

Adult↗

PubMed2001

Amyloid metabolism and secretases in Alzheimer's disease.

Alzheimer's disease (AD) is characterized by the progressive accumulation of amyloid fibrils composed of the amyloid beta-protein (A beta) in senile plaques. A beta is derived from the beta-amyloid precursor protein (APP) after beta- and gamma-secretase cleavages. beta-secretase was recently identified to be a membrane-anchored aspartyl protease that is widely distributed in subcellular compartments, including Golgi, trans-Golgi network, and endosomes. Although definitive identification of gamma-secretase will require reconstituting its activity in vitro, mounting evidence suggests that gamma-secretase is an unusual intramembrane-cleaving aspartyl protease. Two intramembranous aspartate residues in presenilin (PS) are absolutely required for A beta generation. Three classes of gamma-secretase inhibitors can directly bind to PS, strongly supporting the hypothesis of PSI as gamma-secretase. These results provide the molecular basis for therapeutic interventions that reduce A beta accumulation in AD patients by inhibiting beta- or gamma-secretase.

Alzheimer Disease↗

PubMed2001

Cytoplasmic localization of p21Cip1/WAF1 by Akt-induced phosphorylation in HER-2/neu-overexpressing cells.

Amplification or overexpression of HER-2/neu in cancer cells confers resistance to apoptosis and promotes cell growth. The cellular localization of p21Cip1/WAF1 has been proposed to be critical either in promoting cell survival or in inhibiting cell growth. Here we show that HER-2/neu-mediated cell growth requires the activation of Akt, which associates with p21Cip1/WAF1 and phosphorylates it at threonine 145, resulting in cytoplasmic localization of p21Cip1/WAF1. Furthermore, blocking the Akt pathway with a dominant-negative Akt mutant restores the nuclear localization and cell-growth-inhibiting activity of p21Cip1/WAF1. Our results indicate that HER-2/neu induces cytoplasmic localization of p21Cip1/WAF1 through activation of Akt to promote cell growth, which may have implications for the oncogenic activity of HER-2/neu and Akt.

3T3 Cells↗

PubMed2001

Nuclear localization of EGF receptor and its potential new role as a transcription factor.

Epidermal growth factor receptor (EGFR) has been detected in the nucleus in many tissues and cell lines. However, the potential functions of nuclear EGFR have largely been overlooked. Here we demonstrate that nuclear EGFR is strongly correlated with highly proliferating activities of tissues. When EGFR was fused to the GAL4 DNA-binding domain, we found that the carboxy terminus of EGFR contained a strong transactivation domain. Moreover, the receptor complex bound and activated AT-rich consensus-sequence-dependent transcription, including the consensus site in cyclin D1 promoter. By using chromatin immunoprecipitation assays, we further demonstrated that nuclear EGFR associated with promoter region of cyclin D1 in vivo. EGFR might therefore function as a transcription factor to activate genes required for highly proliferating activities.

Animals↗

PubMed2001

HER-2/neu induces p53 ubiquitination via Akt-mediated MDM2 phosphorylation.

HER-2/neu amplification or overexpression can make cancer cells resistant to apoptosis and promotes their growth. p53 is crucial in regulating cell growth and apoptosis, and is often mutated or deleted in many types of tumour. Moreover, many tumours with a wild-type gene for p53 do not have normal p53 function, suggesting that some oncogenic signals suppress the function of p53. In this study, we show that HER-2/neu-mediated resistance to DNA-damaging agents requires the activation of Akt, which enhances MDM2-mediated ubiquitination and degradation of p53. Akt physically associates with MDM2 and phosphorylates it at Ser166 and Ser186. Phosphorylation of MDM2 enhances its nuclear localization and its interaction with p300, and inhibits its interaction with p19ARF, thus increasing p53 degradation. Our study indicates that blocking the Akt pathway mediated by HER-2/neu would increase the cytotoxic effect of DNA-damaging drugs in tumour cells with wild-type p53.

3T3 Cells↗

PubMed2001

[Establishment and application of experimental animal model for hypertrophic scar].

OBJECTIVE: To establish a real animal model for hypertrophic scar. METHODS: 388 wounds on the ears of 47 rabbits were created including rounds 6 mm in diamiter on ventrol or dorsal side and 1.5 cm x 4.5 cm rectangular wounds. Histological and histochemical analyses, in situ hybridization and cell apoptosis were tested. RESULTS: 70 percent of the wounds can from excess dermal scarring which is similar to human hypertrophic scar. The hight of excess dermal scarring is as 3-4 times high as original ventol skin. The excess scarring can last 150 days at the most. while 80 percent appears on rectangular wounds and it lasts more than 262 days. Large amount of fibroblasts, nodular and spiral structures exist in excessive dermal scarring. Local injection of TGF-beta 1 and IFN-r can promote and inhibit the formation of excessive dermal scarring respectively. SDS-PAGE shows that type III collagen content increased in excessive dermal scarring. In situ hybridization shows long-lasting expression of type I and III precollagen mRNA in excessive dermal scarrint. TGF-beta 1 mRNA also cope with that of precollagen. Fibroblast apoptosis in excessive dermal scarring of this model indicate that fibroblast apoptosis plays an important role in the process of occurrance, development of abnormal scar. CONCLUSION: After wounding, rabbit ears can produce excessive dermal scarring which is similar to human hypertrophic scar. This can be used as an experimental model for the study of cicatrix.

Animals↗

PubMed2001

[An experimental study of tissue engineered autologous cartilage by using an injectable polymer].

OBJECTIVE: To investigate the proper cell density of tissue engineered autologous cartilage to indicate the clinical application. METHODS: The chondrocytes, isolated from mini swines' ears, were mixed with an injectable biocompatible matrix(Pluronic F127) to make the cell suspensions with the densities of 10,20, 30,40,50,60,70 x 10(6)/ml. The chondrocyte-polymer complex was injected into the subcutaneous tissue of the swines' abdomens. Each specimen was harvested and evaluated with body-mass, histological examination, and glycosaminoglycan content and type II collagen tests after 6 weeks in vivo. RESULTS: The histological examination had showed that the neo-cartilage was solid, homogenous cartilage when using 50 million chondrocytess/cc for 6 weeks. The samples with the 10 and 30 million chondrocytes/cc showed that the area of the cartilage was incomplete and separated by the remnant polymer. The mass of the samples was ranged from 30-110 mg after 6 weeks. The glycosaminoglycan content was lower from 5.8 to 9.0 percent, compared to the 9.2 percent of the normal auricular cartilage. Western-Blot had presented the type II collagen in all samples. CONCLUSION: This study has demonstrated that the qutologous cartilage could be generated by using tissue engineering technique, with the histological characteristics similar to natural cartilage. Fifty million chondrocytes per cc could yield the best quality cartilage in 6 weeks.

Animals↗

PubMed2001

[Clinical study on treatment of oviduct obstruction by integrative traditional Chinese and Western medicine].

OBJECTIVE: To find an effective and practical treatment of oviduct obstruction (OvO). METHODS: One hundred and twenty OvO patients were randomly divided into three groups, the TCM-WM group, treated with integrative traditional Chinese and western medicine, the TCM group treated with Chinese herbal medicine alone and the WM group treated with western medicine alone. The therapeutic effect as well as the effect of treatment on serum C-reactive protein (CRP) and interleukin-1 beta (IL-1 beta) were observed. RESULTS: After treatment, the fallopian tube patency rate was 86.7% and the pregnant rate 85.0% in the TCM-WM group, while in the TCM group was 66.7% and 63.3% respectively, and in the WM group 53.3% and 50.0% respectively. Comparison among the three groups showed that the effect in the TCM-WM group was significantly superior to that in the other two groups (P < 0.01). The levels of CRP and IL-1 beta were all lowered after 3 courses of treatment, and the effect was more evident in the TCM-WM group (P < 0.01). CONCLUSION: TCM-WM treatment is a good and practical method in treating oviduct obstruction.

Adult↗

PubMed2000

The human ARHI tumor suppressor gene inhibits lactation and growth in transgenic mice.

ARHI is a novel imprinted tumor suppressor gene. To study its function in vivo, we have developed transgenic mice that overexpress ARHI. Offspring bearing the transgene had significantly lower body weights than did nontransgenic littermates. In addition, strong expression of the ARHI transgene was associated with greatly impaired mammary gland development and lactation, failure of ovarian folliculogenesis resulting in decreased fertility, loss of neurons in the cerebellar cortex, and impaired development of the thymus. Decrease in body size and defects in the mammary glands correlated with the level of transgene expression. Immunohistochemical analysis indicated that expression of prolactin (PRL), but not growth hormone, was lower in the pituitary glands of mice with defective mammary gland development. The defect in pregnancy-associated mammary tissue proliferation was associated with decreased serum PRL and progesterone levels. Moreover, lower levels of estrogen receptor and progesterone receptor were observed in postpartum mammary glands and in the ovaries of mice that overexpressed ARHI. Our data suggest that ARHI can inhibit PRL secretion and act as a negative regulator in murine growth and development.

Animals↗

PubMed2000

Presenilin complexes with the C-terminal fragments of amyloid precursor protein at the sites of amyloid beta-protein generation.

An unusual intramembranous cleavage of the beta-amyloid precursor protein (APP) by gamma-secretase is the final step in the generation of amyloid beta-peptide (Abeta). Two conserved aspartates in transmembrane (TM) domains 6 and 7 of presenilin (PS) 1 are required for Abeta production by gamma-secretase. Here we report that the APP C-terminal fragments, C83 and C99, which are the direct substrates of gamma-secretase, can be coimmunoprecipitated with both PS1 and PS2. PS/C83 complexes were detected in cells expressing endogenous levels of PS. The complexes accumulate when gamma-secretase is inactivated either pharmacologically or by mutating the PS aspartates. PS1/C83 and PS1/C99 complexes were detected in Golgi-rich and trans-Golgi network-rich vesicle fractions. In contrast, complexes of PS1 with APP holoprotein, which is not the immediate substrate of gamma-secretase, occurred earlier in endoplasmic reticulum-rich vesicles. The major portion of intracellular Abeta at steady state was found in the same Golgi/trans-Golgi network-rich vesicles, and Abeta levels in these fractions were markedly reduced when either PS1 TM aspartate was mutated to alanine. Furthermore, de novo generation of Abeta in a cell-free microsomal reaction occurred specifically in these same vesicle fractions and was markedly inhibited by mutating either TM aspartate. Thus, PSs are complexed with the gamma-secretase substrates C83 and C99 in the subcellular locations where Abeta is generated, indicating that PSs are directly involved in the pathogenically critical intramembranous proteolysis of APP.

Amyloid Precursor Protein Secretases↗

PubMed2000

Tumor selective G2/M cell cycle arrest and apoptosis of epithelial and hematological malignancies by BBL22, a benzazepine.

Two distinct benzodiazepine binding sites have been identified, (i) a central site restricted to brain and (ii) a ubiquitously expressed mitochondrial binding site, the so-called peripheral-type benzodiazepine receptor (PBR). In this paper, we show that a benzazepine referred to as BBL22 (2-amino 9-chloro-7-(2-fluorophenyl)-5H-pyrimidol[5,4-d][2]benzazepine), which is classified as a PBR ligand based on structure, induces arrest in G(2)/M phase of the cell cycle in human tumor cell lines of both epithelial and hematopoietic cellular origin. After G(2)/M arrest, several tumor types, notably prostate and certain breast cancer lines exhibited significant apoptosis. Ideally, cancer therapies should selectively target tumor cells while sparing normal cell counterparts. BBL22 exhibited such selectivity, as it did not affect the growth and survival of nonmalignant breast and prostate epithelial lines. Moreover, BBL22 demonstrated structural requirements for this selective antitumor activity as 11 structurally related PBR ligands, including high-affinity ligands Ro5-4864 and PK11195, failed to induce tumor cell growth arrest or apoptosis. The in vivo antitumor activity of BBL22 was examined in a human xenograft model of androgen-independent prostate cancer where BBL22 significantly reduced the growth of PC3 prostate tumors without eliciting overt toxicity. Identification of BBL22 represents a tumor selective therapeutic strategy for a variety of human tumors.

Antineoplastic Agents↗