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A Y Liu

Publications and source records attributed to A Y Liu.

At least 37 records · Page 2Linked to original sources
PubMed1998

Hevin, an antiadhesive extracellular matrix protein, is down-regulated in metastatic prostate adenocarcinoma.

Hevin, a gene closely related to the extracellular matrix protein SPARC, is an acidic cysteine-rich glycoprotein shown to be important for the adhesion and trafficking of cells through the endothelium. Through the use of differential display and differential EST analysis, we identified Hevin as a gene whose transcription is down-regulated in transformed prostate epithelial cell lines and metastatic prostate adenocarcinoma. These results were confirmed by comparing expression levels between normal and neoplastic human prostate tissues using Northern analysis. In situ hybridization with an 35S-labeled antisense riboprobe demonstrated the loss of Hevin expression in metastatic prostate carcinoma. The expression pattern of Hevin in transformed and metastatic epithelium may provide further insights into the complex cell adhesion events involved in the metastatic progression of prostate carcinoma.

Adenocarcinoma↗
PubMed1998

An expressed-sequence-tag database of the human prostate: sequence analysis of 1168 cDNA clones.

The human prostate is a complex glandular organ with functional development under hormonal regulation. Diseases of the prostate result in significant morbidity and mortality in the form of benign prostatic hypertrophy and prostate adenocarcinoma. The characterization of the molecular framework of the human prostate at the level of expressed genes will facilitate the understanding of normal and pathological prostate biology. The purposes of this study were to acquire an initial assessment of the qualitative and quantitative diversity of gene expression in the normal human prostate and to determine the extent that genes with prostate-restricted expression can be assessed using an expressed sequence tag approach. We have constructed a directional cDNA library from normal adult human prostate tissue and partially sequenced the 5' end of 1168 randomly selected cDNA clones, resulting in more than 400 kb of DNA sequence. Homology searches of the sequenced cDNAs against the GenBank and dbEST databases revealed that 43% of the sequences are identical to human genes whose functions are known, 5% are similar but not identical to known genes in humans or lower organisms, 5% match the mitochondrial genome, 9% are composed of interspersed DNA repeats, 30% are homologous to sequences in the dbEST database without a described function, and 6% are novel sequences. A total of 780 distinct species were identified. In addition to the 74 novel transcripts, 4 genes, prostate-specific antigen (PSA), prostate secretory protein (PSP), prostate acid phosphatase (PAP), and human glandular kallekrein 2 (HK2), have no homologous sequences in the databases that originate from sources other than prostate and thus may represent genes with prostate-restricted expression. Sequences matching PSA, PSP, and PAP each accounted for > 1% of the total ESTs and represent highly abundant transcripts, correlating with the abundance of these proteins in the prostate gland. No novel transcripts were represented by more than one EST and thus are expressed at levels much lower than the known prostate-specific genes.

Adult↗
PubMed1997

The heat-shock transcription factor HSF1 is rapidly activated by either hyper- or hypo-osmotic stress in mammalian cells.

Osmoregulation, the cellular response to environmental changes of osmolarity and ionic strength, is important for the survival of living organisms. We have demonstrated previously that an exposure of mammalian cells to hypo-osmotic stress, either in growth medium (30% growth medium and 70% water) or in binary solution containing sorbitol and water, prominently induced the DNA-binding activity of the heat-shock transcription factor (HSF1) [Huang, Caruccio, Liu and Chen (1995) Biochem. J. 307, 347-352]. Since hyperosmotic and hypo-osmotic stress usually elicit opposite biological responses, we wondered what would be the effect of hyperosmotic stress on HSF activation. In this study we have examined the HSF DNA-binding activity in HeLa cells maintained in the sorbitol/water binary solution over a wide concentration range (0.1-0.9 M) and in Dulbecco's medium supplemented with sorbitol or NaCl. We found that HSF-binding activity could be induced prominently under both hypo-osmotic (0.1-0.25 M) and hyperosmotic conditions (0.50-0.90 M). In both cases, HSF activation was observed within 5 min after changing the osmotic pressure. The activation was accompanied by both HSF trimerization and nuclear translocation, and appeared to be independent of protein synthesis. The effects of hypo- or hyper-osmotic stress on HSF activation could be reversed once the cells were returned to iso-osmotic conditions (0.30M) with a half-life (t12) of 25 min or less. This rapid turnover of the osmotic-stress-induced HSF-binding activity was inhibited by cycloheximide, a potent inhibitor of protein synthesis. Unlike heat shock, activation of HSF by either hypo- or hyper-osmotic stress did not lead to an accumulation of heat-shock protein 70 (HSP70) mRNA in HeLa cells. We propose that HSF activation during osmotic stress may serve physiological functions independent of the synthesis of heat-shock proteins.

Animals↗
PubMed1997

Cell-cell interaction in prostate gene regulation and cytodifferentiation.

To examine the role of intercellular interaction on cell differentiation and gene expression in human prostate, we separated the two major epithelial cell populations and studied them in isolation and in combination with stromal cells. The epithelial cells were separated by flow cytometry using antibodies against differentially expressed cell-surface markers CD44 and CD57. Basal epithelial cells express CD44, and luminal epithelial cells express CD57. The CD57+ luminal cells are the terminally differentiated secretory cells of the gland that synthesize prostate-specific antigen (PSA). Expression of PSA is regulated by androgen, and PSA mRNA is one of the abundant messages in these cells. We show that PSA expression by the CD57+ cells is abolished after prostate tissue is dispersed by collagenase into single cells. Expression is restored when CD57+ cells are reconstituted with stromal cells. The CD44+ basal cells possess characteristics of stem cells and are the candidate progenitors of luminal cells. Differentiation, as reflected by PSA production, can be detected when CD44+ cells are cocultured with stromal cells. Our studies show that cell-cell interaction plays an important role in prostatic cytodifferentiation and the maintenance of the differentiated state.

Androgens↗
PubMed1997

Relationship between the size and margin status of ductal carcinoma in situ of the breast and residual disease.

BACKGROUND: For women with ductal carcinoma in situ (DCIS) of the breast who have been treated with breastconserving surgery, the usefulness of size and surgical margin status (i.e., presence or absence of disease at the point of excision) as prognostic factors for predicting residual disease has not been well established. This study was conducted to determine more clearly the relationship between size and margin status of mammary DCIS to residual disease. METHODS: The pathology records of 232 consecutive patients with mammary DCIS who had been initially treated with lumpectomy at the University Hospitals of Cleveland were retrospectively reviewed. The size of the DCIS and the surgical margins of lumpectomy were analyzed. Residual disease was defined as the persistence of DCIS in the re-excision and/or mastectomy specimens. RESULTS: Residual disease was found in 15 of 101 patients with DCIS of less than 1.0 cm in longest dimension, in 27 of 96 patients with DCIS of 1.0-2.4 cm in size, and in 24 of 35 patients with DCIS of greater than or equal to 2.5 cm in size (P<.001). Residual disease was found in 30 of 77 patients with DCIS and positive margins, in 11 of 59 patients with DCIS and close margins (< or =1mm), and in 10 of 73 patients with DCIS and negative margins (>1 mm) (P =.001). In multivariate analysis, the occurrence of residual disease was associated with large tumor size (i.e., > or =2.5 cm) (odds ratio [OR] = 7.7; 95% confidence interval [CI] = 3.13-20.00; two-sided P = .0001) and with positive margin status (OR = 2.2; 95% CI = 1.02-4.55; two-sided P = .04). CONCLUSIONS: The size and margin status of DCIS each were found to be independent predictors of residual disease.

Adult↗
PubMed1997

The results of intraoperative consultations in 181 ductal carcinomas in situ of the breast.

BACKGROUND: The utility of frozen section (FS) examination in the intraoperative management of breast lesions is well established. The accuracy of FS in the diagnosis of borderline noninvasive or preinvasive breast lesions is uncertain. METHODS: The authors retrospectively reviewed the results of intraoperative consultations/frozen section examinations of 181 ductal carcinomas in situ (DCIS) of the breast. Various clinical and pathologic factors were analyzed and correlated with FS diagnosis. RESULTS: FS examination was performed on 153 cases (85%) and only macroscopic examination on 28 cases (15%). FS diagnoses were as follows: DCIS in 76 cases (50%), atypical ductal hyperplasia/suspicious for DCIS in 8 cases (5%), benign in 55 cases (36%), deferred in 13 cases (8%), and invasive carcinoma in 1 case. FS accuracy, false-negative rate, and false-positive rate were 55%, 36%, and 0.6%, respectively. Sampling error was the main reason for the low detection rate, and technical inadequacy was a major factor contributing to interpretive problems. In multivariate regression analysis, FS accuracy was significantly associated with the clinical presentation of a palpable mass (odds ratio [OR] = 4.16, 95% confidence interval [CI]: 2.04-8.45), the macroscopic finding of a mass (OR = 3.03, 95% CI: 1.45-6.67), and necrosis (OR = 3.13, 95% CI: 1.4-6.67). CONCLUSIONS: The authors concluded that the accuracy of FS diagnosis of DCIS was low, mainly due to sampling error. In general, FS examination should not be performed when no lesion/mass is identified by macroscopic examination.

Adolescent↗
PubMed1997

Identification of differentially expressed prostate genes: increased expression of transcription factor ETS-2 in prostate cancer.

BACKGROUND: Little is known about the genetic events in the malignant transformation of prostatic cells. This is due in large measure to the cellular heterogeneity of the prostate. METHODS: An amplification method was devised to synthesize cDNA from small samples of cancer and benign tissues of the same resected glands. Differential gene expression of candidate informative markers between cancer and benign was screened by the polymerase chain reaction with gene-specific oligonucleotide primers. RESULTS: The expression of a transcription factor, ETS-2, was shown to be elevated in some cancer specimens. Elevated expression was also noted for neuron-specific enolase (NSE) and another transcription factor, SEF2. CONCLUSIONS: Our method can be used to identify quickly genes that are differentially expressed between benign and cancerous prostate cells. Transcription factors, such as ETS-2, may play a significant role in cancer progression.

Cell Transformation, Neoplastic↗
PubMed1997

The human NTT gene: identification of a novel 17-kb noncoding nuclear RNA expressed in activated CD4+ T cells.

We describe the cloning and characterization of the NTT gene (noncoding transcript in T cells), identified by differential display RT-PCR based on the differential presence of its transcript in a subset of activated, human CD4+ T-cell clones. The full-length cDNA and genomic sequences were cloned and found to produce a 17-kb transcript that is polyadenylated, but is not spliced. Consistent with the transcript's nuclear predominance, NTT has no open reading frame larger than 270 bp. It is transcribed in a select subset of CD4+ T-cell clones propagated in vitro. Its transcription can also be induced in freshly isolated T cells by in vitro activation with PHA or with PMA and ionomycin. In vivo, NTT transcripts are found only in activated, but not resting, T cells. Transcripts were absent in a variety of lymphoid cell lines and transformed lines from other tissues. NTT is a new member of the small group of genes including XIST (X-specific transcript), H19, and IPW (imprinted gene in the Prader-Willi syndrome region), which are transcribed but not translated, and may have a role in the regulation of neighboring genes. XIST, H19, and IPW exhibit monoallelic expression, but both NTT alleles are expressed in CD4+ T-cell clones. Southern blot and fluorescence in situ hybridization analyses show that NTT is a single-copy gene residing in chromosome 6q23-q24, near the interferon-gamma receptor gene (IFN-gamma R). Their proximity and shared expression pattern suggest a possible functional relationship.

Alleles↗
PubMed1997

Improved reverse transcriptase-polymerase chain reaction protocol with exogenous internal competitive control for prostate-specific antigen mRNA in blood and bone marrow.

The possibility of improving diagnosis of micrometastases from prostate cancer by further enhancing the detection of prostate-specific antigen-producing cells in circulation is being evaluated. We have developed a reverse transcriptase-PCR protocol with the desirable characteristics of low limit of detection, high specificity, reproducibility of response, and ease of performance. Among the procedural alterations that have contributed to these improvements are longer PCR primers, a two-step amplification cycle, and hot-start PCR. We have lowered the limit of detection to one LNCaP prostate-cancer cell in 10(8) peripheral blood mononuclear cells, and samples of blood and bone marrow from healthy donors have yielded no false positives. Because PCR procedures frequently exhibit tube-to-tube variability, we have incorporated a set of internal and external controls into the protocol-a significant advance in assuring assay reliability.

Bone Marrow↗
PubMed1997

[Analysis of sedative effect of chloral hydrate and diazepam on children during CT examination].

Before CT examination, make those non-cooperation children take chloral hydrate or diazepam according to their ages can go beyond the limit to reduce the repeation and dose of taking medicine and shorten the waiting time. The author collected 204 samples and divided them into three groups of baby, infant and preschool children. Among them, there were 94 samples of taking orally chloral hydrate and 110 ones having intravenous injection with diazepam according to doctor's order. The author also compared the effect of sedation and the chi 2 test showed that chloral hydrate and diazepam had similar effect on babies (P > 0.05), while the sedative effect of diazepam on infants and preschool children was superior to that of chloral hydrate on them (P < 0.05, P < 0.01).

Administration, Oral↗
PubMed1996

Prostatic cell lineage markers: emergence of BCL2+ cells of human prostate cancer xenograft LuCaP 23 following castration.

A model of prostate cancer progression based on the expression pattern of informative genes in the human prostate cancer xenograft LuCaP 23.1 is presented. Apparently, there are at least 2 tumor cell populations of LuCaP 23.1, representing 2 different phenotypes. One is NSE (neuron-specific enolase)-positive and the other NSE-negative. NSE-positive tumors were recovered after hormone-independent growth in castrated mice. These hormone-independent tumors also expressed BCL2, a gene product shown to inhibit apoptosis. With NSE, BCL2 and PSA (prostate-specific antigen) as identifying markers, the model specifies a putative progression sequence of the prostate cancer cell types. We also show a proposed lineage relationship among the 3 principal normal cell types found in the prostatic epithelium.

Animals↗
PubMed1996

Attenuated heat shock transcriptional response in aging: molecular mechanism and implication in the biology of aging.

A characteristic feature of aging is a progressive impairment in the ability to adapt to environmental challenges. The purpose of this review is to present the experimental evidence of an attenuated heat shock transcriptional response to heat and physiological stresses in a number of aging mammalian model systems. These include the human diploid fibroblasts in culture, whole animals and animal derived cells and cell cultures, as well as peripheral blood mononuclear cells obtained from human donors. The possibility that age-dependent changes in cellular redox status, as exemplified by the increased production of reactive oxygen inter-mediates and accumulation of oxidatively-modified proteins, affects the regulation and function of the heat shock factor 1 (HSF1) and contributes to the attenuated heat shock transcriptional response in aging cells and organisms is discussed. Given the fundamentally important role of HSPs in many aspects of protein homeostasis and signal transduction, it seems likely that the inability, or compromised ability, of aging cells and organisms to produce HSPs in response to stress would contribute to the well known increase in morbidity and mortality of the aged when challenged.

Aging↗
PubMed1995

Rapid activation of the heat shock transcription factor, HSF1, by hypo-osmotic stress in mammalian cells.

Osmoregulation is important to living organisms for survival in responding to environmental changes of water and ionic strength. We demonstrated here for the first time that exposure of HeLa cells to a hypotonic medium (30% growth medium and 70% water) prominently induced the binding activity of the heat shock transcription factor (HSF). Pretreatment of cells with cycloheximide did not inhibit the induction of HSF-binding activity, indicating that the mechanisms of induction are independent of new protein synthesis. The magnitude of hypo-osmotic stress-induced HSF-binding activity was comparable with that induced by heat shock. The induction, as monitored by gel-mobility-shift assay, occurred within 5 min of hypo-osmotic stress and persisted at least up to 4 h in HeLa cells under the hypotonic conditions. Addition of sorbitol to the hypotonic medium abolished HSF activation. Hypo-osmotic stress-induced HSF binding could also be demonstrated in HeLa cells maintained in simple sorbitol solution by decreasing the sorbitol concentration from 300 mM to 200 mM or less. Competition analysis suggests that the effects of hypo-osmotic stress on HSF-binding activity was specific. Cross-linking experiments and Western-blot analysis demonstrated that hypo-osmotic stress induced trimerization of human heat shock factor 1 (HSF1) in intact HeLa cells, suggesting that trimer formation of HSF1 was responsible for inducing HSF-binding activity in hypo-osmotically stressed cells. However, unlike heat shock response, the activation of HSF by hypo-osmotic stress did not lead to accumulation of hsp70 mRNA in HeLa cells.

Base Sequence↗
PubMed1994

Thiol reducing reagents inhibit the heat shock response. Involvement of a redox mechanism in the heat shock signal transduction pathway.

We evaluated the effects of thiol-reducing agents on the heat shock response in human and rodent cells in culture. Using HeLa cells as an example, we demonstrated that dithiothreitol (DTT,2mM) inhibited the heat (42 degrees C) induced increase in the synthesis of heat shock proteins (HSPs), abundance of mRNA of hsp 70, hsp 70 gene promoter activity, and the heat shock factor (HSF) DNA binding activity. This effect of DTT was specific and attributable to its reducing activity; oxidized DTT was ineffective, and other thiol reducing compounds had the same effect as DTT. Time course and dose-response studies showed that DTT significantly inhibited the heat shock induction of heat shock element binding activity with no preincubation and that 0.6 and 1-2 mM DTT gave half-maximal and maximal inhibition, respectively. The effect of DTT was reversible; removal of the DTT-containing medium prior to heat shock rendered the cells fully responsive. Analysis of the effects of DTT on the regulation and function of HSF suggests that DTT blocked an early and important step in the activation process without having a direct effect on the HSF protein. Thus, DTT inhibited the heat-induced trimerization, phosphorylation, and nuclear translocation of HSF and was also effective against a number of other reagents that are known to activate HSF. On the other hand, DTT did not block the response induced by heat shock at 45 degrees C, and in vitro addition of DTT failed to modulate the DNA binding activity of activated HSF present in cell extracts, suggesting that the HSF protein itself is unlikely to be a direct target of action of DTT. These results, together with the observation that activation of HSF DNA binding activity was attenuated under an anoxic condition and that hydrogen peroxide mimicked the effects of heat shock, suggest the involvement of a redox mechanism as an early and important step in the heat shock signal transduction pathway.

Cell Nucleus↗
PubMed1994

Studies of the mechanism of cytolysis by HIV-1-specific CD4+ human CTL clones induced by candidate AIDS vaccines.

Vaccine-induced, virus-specific CTLs may rapidly eliminate the host cells that first become infected after virus exposure, thereby preventing disseminated infection. Thus, there is much interest in the ability of candidate AIDS vaccines to elicit CTLs. All HIV-1 envelope (env) protein-based vaccines tested to date in seronegative humans induce CTLs from the CD4+ subset. Because the mechanism of cytolysis by CD4+ CTLs is controversial, a detailed study of the cytolytic reactions mediated by vaccine-induced, HIV-1-specific human CD4+ CTL clones was conducted. CD4+ CTL clones induced rapid destruction of Ag-pulsed target cells. Lysis was readily detectable within 15 min. Lysis was not a result of syncytium formation between CD4+ effector cells and env-expressing targets. Target cell destruction was not dependent upon de novo RNA or protein synthesis in either the effector or the target cell. Expression of perforin mRNA was detected by Northern blotting and reverse-transcriptase-PCR in CD4+ CTL clones but not in autologous B lymphoblastoid cell lines. Immunohistochemical studies demonstrated perforin protein in cytoplasmic granules in CD4+ CTL clones. Lysis by CD4+ CTLs was strictly dependent upon extracellular Ca2+ and was highly specific, with no lysis of innocent bystander cells. DNA fragmentation was detectable in target cells, but did not precede 51Cr release. Taken together, these results provide a dramatically different view of cytolysis by human CD4+ CTLs. Target cells are lysed by a rapid and efficient mechanism that involves a preformed mediator and that is functionally similar to the mechanism used by CD8+ CTLs.

AIDS Vaccines↗
PubMed1994

Transient cold shock induces the heat shock response upon recovery at 37 degrees C in human cells.

We evaluated the effects of a transient cold shock followed by recovery and incubation at 37 degrees C on the regulation of heat shock gene expression in the IMR-90 human diploid fibroblasts and HeLa cells in tissue culture. We showed that preincubation of cells at 4 degrees C induced the synthesis and accumulation of the heat shock proteins (HSPs) upon recovery at 37 degrees C, and the degree of this induction was directly related to the time that the cells spent at 4 degrees C. Assays on the abundance of the hsp 70 transcript, the hsp 70 gene promoter activity, and the trimerization and activation of heat shock factor (HSF) to bind to its consensus heat shock element (HSE) provided evidence that this induction of the heat shock response in cells recovering from a transient cold shock is attributable to a transcriptional event mediated by the activation of HSF. Further, the induction was a response to the temperature upshift from 4 to 37 degrees C as opposed to the 4 degrees C treatment itself; quantitation of the HSE-binding activity of cells incubated at 4 degrees C without recovery and incubation at 37 degrees C gave no evidence of an activated response. Analysis of the effects of protein synthesis inhibitors demonstrated that neither cycloheximide nor puromycin was effective in blocking the induction of HSE-binding activity in cells recovering from a transient cold shock. Experiments on the time course and temperature dependence of this induction of HSE-binding activity showed that the onset, magnitude, and duration of this induction were directly proportional to the severity of the cold stress (measured by time and temperature). We discuss the possible mechanism(s) involved in this induction of the heat shock genes at 37 degrees C by a transient cold shock and the biological implications of this observation.

Base Sequence↗
PubMed1994

Expression of CD44 in prostate cancer cells.

Expression of CD44, the cellular hyaluronate receptor, was examined in human prostate cell lines. CD44 mRNA was detected in cell lines PC3 and DU145, both established from organ metastases of prostate adenocarcinoma, but not in cell line LNCaP, established from a lymph node metastasis. PC3 and DU145, but not LNCaP, are tumorigenic and metastatic in nude mice. Of the CD44 mRNA species identified, the standard CD44s as well as variant isoforms CD44v7, CD44v10, CD44v14, CD44v13-v14, CD44v12-v14 and CD44v7-v14 are represented.

Adenocarcinoma↗