Biomedical subjects

T T Wu

Publications and source records attributed to T T Wu.

At least 73 records · Page 4Linked to original sources

PubMed1998

Tyrosine phosphorylation of selected secretory carrier membrane proteins, SCAMP1 and SCAMP3, and association with the EGF receptor.

Secretory carrier membrane proteins (SCAMPs) are ubiquitously expressed proteins of post-Golgi vesicles. In the presence of the tyrosine phosphatase inhibitor vanadate, or after overexpression in Chinese hamster ovary (CHO) cells, SCAMP1 and SCAMP3 are phosphorylated selectively on tyrosine residue(s). Phosphorylation is reversible after vanadate washout in situ or when isolated SCAMP3 is incubated with the recombinant tyrosine phosphatase PTP1B. Vanadate also causes the partial accumulation of SCAMP3, but not SCAMP1, in "patches" at or near the cell surface. A search for SCAMP kinase activities has shown that SCAMPs 1 and 3, but not SCAMP2, are tyrosine phosphorylated in EGF-stimulated murine fibroblasts overexpressing the EGF receptor (EGFR). EGF catalyzes the progressive phosphorylation of the SCAMPs up to 1 h poststimulation and may enhance colocalization of the EGFR and SCAMP3 within the cell interior. EGF also induces SCAMP-EGFR association, as detected by coimmunoprecipitation, and phosphorylation of SCAMP3 is stimulated by the EGFR in vitro. These results suggest that phosphorylation of SCAMPs, either directly or indirectly, may be functionally linked to the internalization/down-regulation of the EGFR.

Amino Acid Sequence↗

PubMed1998

Possible assortment of a1 and a2 region gene segments in human MHC class I molecules.

Using pair-wise comparison of aligned nucleotide sequences of distinct and complete human MHC class I molecules, we have constructed triangular tables to study the similarities and differences of various a1 (exon 2) and a2 (exon 3) region sequences. There are two HLA-A (A*6901 and A*6601) and 13 HLA-B (B*4201, B*8101, B*4102, B*4801, B*4007, B*4001, B*4802, Dw53, B*4406, B*4402, B*3901, B*1514 and B*3702) sequences that have identical a1 sequences with other known MHC class I molecules, while their a2 sequences are the same as those of different ones. Of these 15, A*6901, B*4001 and B*4802 have previously been suggested as the results of recombination between A*6801 and A*0201, B*4101 and B*8101, and B*4801 and B*3501, respectively. However, many other sequences can also be used to generate them by recombination. Furthermore, their reciprocal products have never been identified. Thus, gene conversion has subsequently been suggested as an alternative. Another possible genetic mechanism for generating these nucleotide sequence similarities can be assortment, or that some gene segments can be duplicated or multiplicated to be used in different human MHC class I molecules. Interestingly, this genetic mechanism is probably absent for the generation of different mouse MHC class I molecules.

Alleles↗

PubMed1998

Preferred CDRH3 lengths for antibodies with defined specificities.

The third complementarity determining regions of heavy chain variable regions (CDRH3) confer the fine specificities of antibodies. The CDRH3 length distribution of all human or all mouse antibodies appears to be more or less random, with the human distribution having a wider spread. Since the Kabat database of aligned amino and nucleotide sequences of proteins of immunological interest has grown at least 4 times during the past 7 years, we attempt to study CDRH3 length distributions of human and mouse antibodies with defined specificities, where enough complete and distinct CDRH3 sequences are available. For mouse antibodies against small haptens or carbohydrates, a preferred length usually dominates for a given specificity. There are not enough human sequences of small hapten or carbohydrate antibodies for a similar study. Both human and mouse anti-protein antibodies have wider ranges of CDRH3 length distributions, probably due to the presence of different antigenic epitopes on the protein molecules, and thus many different antibodies. For anti-DNA antibodies, both humans and mice exhibit even wider length distributions, since DNA can be double stranded, single stranded, supercoiled, etc.

Animals↗

PubMed1998

Dysplasia and dysregulation of proliferation in foveolar and surface epithelia of fundic gland polyps from patients with familial adenomatous polyposis.

Fundic gland polyps (FGPs) of the stomach are regarded as hamartomatous or hyperplastic/functional polyps that occur sporadically but at increased frequency in patients with familial adenomatous polyposis syndrome (FAP). There is controversy about the histopathology of FGPs, including occurrence of dysplasia. We, therefore, studied dysplasia in 270 sporadic FGPs from 216 patients and 49 FGPs from 24 patients with FAP. We evaluated dysregulation of epithelial proliferation manifested by loss of the normal inverse topographic distribution of Ki-67 proliferation marker and the cyclin-dependent kinase inhibitor p21(WAF1/CIP1) using immunohistochemistry in 27 sporadic FGPs and in 22 FGPs from patients with FAP. Dysplasia in foveolar and surface epithelia occurred in 12 of 49 (25%) FGPs in patients with FAP but in only 3 of 270 (1%) of sporadic FGPs (p < 0.000001). Fourteen of 49 (29%) of FGPs from patients with FAP were indefinite for dysplasia, as contrasted with 8 of 270 (3%) sporadic FGPs (p < 0.00001). The normal inverse topographic distribution of Ki-67 and p21(WAF1/CIP1) was maintained in 20 of 22 (91%) of FGPs negative for dysplasia but was lost in all (8 of 8) FGPs with dysplasia and in 11 of 19 (58%) FGPs that were indefinite for dysplasia (p = 0.00001). The results indicate that dysplasia can occur in foveolar and surface epithelia of FGPs, especially in patients with FAP, and often is preceded by dysregulation of epithelial proliferation when the morphologic abnormalities are indefinite for dysplasia.

Adenomatous Polyposis Coli↗

PubMed1998

Ocular metastases from breast carcinoma: a report of two cases.

Breast carcinoma metastases to the eye occur more frequently than is clinically recognized. The prevalence of this lesion is not appreciated because of the dominant clinical picture of metastases occurring in other organs or because a number of eye lesions are small and asymptomatic. With the increasing length of survival, more breast cancer patients will require care for ocular metastases. A thorough ophthalmic evaluation, aided by computed tomography or magnetic resonance imaging, usually confirms the diagnosis. Rapid progression of a lesion demands emergency therapy since the dysfunction produced by progressive disease may not otherwise be corrected. Early diagnosis of ocular metastases in patients with breast cancer is important because timely treatment may improve vision and quality of life in the time remaining to patients. Experience with two cases of metastases to the eye from breast cancer are presented, with a review of the literature.

Adult↗

PubMed1997

Profile of numbers of sequence differences among V-genes coding for the variable regions of T cell receptor for antigen alpha and beta chains.

When human T cell receptor for antigen (TCR) alpha chain V-genes were compared pair-wise, the numbers of nucleotide differences showed a characteristic distribution; most were in the range of 100 to 200 differences out of a total of about 300 bases. The same distribution was observed for mouse TCR alpha chains. Even more interesting was that comparing human alpha chains and mouse alpha chains gave essentially the same nucleotide difference pattern. It is inferred from the large number of differences and from the nonspecificity of trans-species (human and mouse) nucleotide sequence differences of TCR V-genes that TCR alpha chains probably diverged early during evolution. The same feature was also observed for human and mouse TCR beta chains, although the alpha and beta chain V-genes were distinct. This evolutionary preservation could be of vital importance to the fidelity of the complicated trimolecular interactions among TCR alpha and beta chains, the processed peptide, and the major histocompatibility complex (MHC) class I or II molecules.

Animals↗

PubMed1997

Extracellular matrix expression in metastasizing and nonmetastasizing adenocarcinomas of the lung.

Alterations in extracellular matrix, cell-cell and cell-matrix adhesion, and oncogenes are thought to be important in tumor progression and metastasis. Adenocarcinomas of the lung from 31 patients were studied for immunohistochemical expression of basement membrane molecule type IV collagen, type IV collagenase, and integrins alpha2,3,v adhesion molecules to assess their diagnostic and prognostic importance in pathological stage T2 tumors. The results indicate that with decreasing tumor differentiation, there is a progressive loss of type IV basement membrane collagen (P = .06) and decreased integrin alpha2 expression (P = .03). Type IV collagenase expression was significantly associated with the presence of lymph node metastases, with moderate to strong expression present in 53% T2N1 tumors compared with none (0%) of the T2N0 tumors (P = .008). Integrin alpha(v) was increased in tumors with nodal metastases compared with those without (P = .08). Loss of alpha2 and alpha3 integrins was associated with increased alpha v expression (P = .03). Median survival was 48 months for T2N0 and 20 months for T2N1 (P = .07). In correlating expression of the immunohistochemical markers and survival, type IV collagenase expression was found to be a predictor of survival at a level of P = .07. Measurable alterations in integrins and extracellular matrix, and in particular, expression of matrix-degrading enzyme type IV collagenase may be of prognostic importance in resectable adenocarcinoma of the lung.

Adenocarcinoma↗

PubMed1997

A method of estimating the numbers of human and mouse T cell receptors for antigen alpha and beta chain V-genes.

T cell receptors for antigen (TCR) V-genes are under a very restrictive evolutionary pressure in order to maintain their biological activities of interacting with MHC class I or II molecules and processed peptides at the protein level. This is in contrast to immunoglobulin V-genes which can mutate more freely. As we have discussed before, 17 or less nucleotide differences between any two mouse lambda light chain V-genes can be due to somatic mutations induced by antigens, allelic variations, and the combination of these two mechanisms. Thus, a cut-off of 17 nucleotide differences has been used to estimate the numbers of the other human and mouse immunoglobulin chain V-genes. Except for mouse heavy chains where experimental study is not yet available, our estimated numbers are in good agreement with experimental findings. For TCR V-genes, however, this cut-off value should be modified as illustrated in the present analysis. Our estimation of the number of human TCR beta chain V-genes is also in good agreement with the recent experimental study of sequencing 685 kb of that gene locus. Estimations for the numbers of human alpha, mouse alpha and beta chain V-genes will wait for future experimental verification.

Animals↗

PubMed1997

Less death in the dying.

Diseases associated with aging are now the primary causes of death in developed countries. This is in part due to the long recognized exponential association of cancer with age and perhaps to a deterioration of the immune system with advanced age. Both prevention of tumorigenesis and immune function are critically dependent on apoptosis. In this study we examined apoptosis in mice of various age following gamma irradiation. We found a striking age-dependent decrease in radiation-induced apoptosis in splenic lymphocytes but not in colorectal epithelial cells. These observations may therefore provide a clue to the decline of immune function with age.

Journal Article↗

PubMed1997

A method of estimating the numbers of human and mouse immunoglobulin V-genes.

Mutations in immunoglobulin V-genes can be due to gene multiplication, allelic variations, mutations induced by antigens or somatic mutations, etc., and various combinations of these. Since the number of different mouse lambda light V-gene nucleotide sequences is relatively small, a pairwise comparison between these sequences can provide a rough idea as to the contributions of the above mechanisms to the number of nucleotide differences between sequences. A plot of occurrences against the number of differences suggests that differences between one to five can be attributed to somatic mutations. Six to 12 differences can be allelic. Thirteen to 17 may be due to allelic variations together with somatic mutations. Differences > 17 appear to be derived from gene multiplication. Although these numbers are most likely somewhat different in humans, they can nevertheless provide a rough guide to sort out the effect of gene multiplication. Estimations of human heavy, kappa and lambda light chain immunoglobulin V-genes are in reasonably good agreement with recent experimental studies. For mouse kappa light and heavy chains, our estimations can provide some insight to future analyses by direct sequencing of these gene segments.

Animals↗

PubMed1997

Effects of nucleotide changes on the ability of hepatitis delta virus to transcribe, process, and accumulate unit-length, circular RNA.

The circular RNA genome of hepatitis delta virus (HDV) can fold into an unbranched rodlike structure. We mutagenized the two ends of this structure and assayed the effects on the ability of the genomes to replicate and accumulate processed RNA transcripts in transfected cells. The top end, defined as that nearest to the 5' end of the putative mRNA for delta antigen, was much more sensitive than the other end, defined as the bottom. Most of the 22 mutants made at the bottom were able to accumulate RNA as well as the wild type. For deletions extending as close as 2 nucleotides (nt) from the predicted domains needed for the two ribozymes, the accumulation levels dropped to <0.1%. In one mutant, 13 nt of HDV was replaced with 57 nt of non-HDV sequences, and accumulation was at 20% of the wild-type level, consistent with the potential of HDV to act as a vector. However, after replacement with a second sequence, accumulation dropped to 1%. For most of the 14 mutants made at the top of the rod, we observed dramatic inhibitory effects. For example, after removal of 3 bp from the stem adjacent to the terminal loop, accumulation dropped to <0.06% of the wild-type genome level. The top region that we considered was adjacent to both the 5' end of the putative mRNA and the domain that has been proposed to contain a promoter for RNA-directed RNA synthesis. The RNA accumulation abilities of certain mutants were tested under additional different experimental conditions. It was found that after longer times, some mutants began to catch up with the wild type. Also, it was found that certain top mutants gave much greater levels of accumulation when transfected into cells containing the small delta antigen. One interpretation of these data is that certain features at the top of the rod are needed for the accumulation of essential delta antigen mRNA species.

Animals↗

PubMed1997

Evidence for colocalization and interaction between 37 and 39 kDa isoforms of secretory carrier membrane proteins (SCAMPs).

Secretory carrier membrane proteins (SCAMPs) are proteins of post-Golgi recycling carriers, including regulated secretory organelles. The two major size variants, SCAMP1 (37 kDa) and SCAMP2 (39 kDa), extensively colocalize in membranes of fibroblasts and parotid acinar cells based on immunocytochemistry and velocity centrifugation, although the relative amounts of each variant may differ in selected organelles. SCAMP1, and to a lesser extent, SCAMP2, are substrates for chemical crosslinking in situ, and the recognizable crosslinking products of SCAMP1 suggest potential formation of homomultimers. SCAMP1 and SCAMP2 can be co-immunoprecipitated following detergent solubilization, using antibodies that specifically react with only one of the variants. Both the localization and interactions of SCAMPs are reiterated using transfected SCAMP1 that is epitope tagged (myc) at either the NH2 or COOH terminus and an anti-myc antibody. Like other transport vesicle membrane proteins, SCAMPs form complexes that apparently include homomultimers. Furthermore, these studies suggest that both SCAMP1 and SCAMP2 may function together in a single protein complex.

Animals↗

PubMed1997

Three mammalian SCAMPs (secretory carrier membrane proteins) are highly related products of distinct genes having similar subcellular distributions.

The primary structures of three human forms of secretory carrier membrane proteins (SCAMPs) have been deduced from full-length clones isolated from a HeLa cell cDNA library and confirmed by a combination of comparison to expressed sequence tags, microsequencing of purified protein, and in vitro transcription and translation. The structures indicated that SCAMPs are highly related products of distinct genes, and that the sequence identity of an individual SCAMP between different mammalian species is almost complete. Analysis of the distribution of SCAMPs among different mammalian tissues and cells indicates parallel expression of polypeptides and cognate mRNAs, and indicates that the three SCAMPs are usually but not always expressed together. The apparent M(r)s of two SCAMPs (1 and 2) do not vary appreciably among species, while that of the third (SCAMP3) is approximately 2 kDa larger in rodent cells than in humans. Examination of the codistribution of the three forms within individual cells using double label immunofluorescence indicates extensive colocalization of SCAMP2 and SCAMP3 with endogenous SCAMP1, however, subcellular regions enriched for a particular SCAMP are readily visible. These findings suggest that the SCAMPs may largely function at the same sites during vesicular transport rather than in separate post-Golgi recycling pathways.

Animals↗

PubMed1997

Genetic alterations and epithelial dysplasia in juvenile polyposis syndrome and sporadic juvenile polyps.

Juvenile polyps are regarded as hamartomatous polyps and occur in sporadic and familial syndromic settings. There is increased risk of gastrointestinal neoplasia in patients with juvenile polyposis syndrome, but the molecular mechanisms are not known. We therefore studied 78 colorectal juvenile polyposis from 12 patients with juvenile polyps syndrome and 34 sporadic juvenile polyps for epithelial dysplasia and genetic changes associated with colorectal neoplasia. Dysplasia occurred in 31% of syndromic juvenile polyps but not in sporadic juvenile polyps (P < 0.0001). Topographic control of proliferation and expression of the cyclin-dependent kinase inhibitor p21(WAFI/CIP1) seen in native colorectal epithelium was lost in 79% of dysplastic juvenile polyps and in 8% of nondysplastic juvenile polyps (P < 0.000001). Somatic mutations in the adenomatous polyposis coli (APC) gene were demonstrated in 50% of dysplastic juvenile polyps (3 of 6) but not in any of 16 juvenile polyps without dysplasia (P = 0.01). Both sporadic and syndromic juvenile polyps had K-ras mutations (14%) and there was no relationship to dysplasia. p53 gene product overexpression identified by immunohistochemical staining occurred rarely in dysplastic juvenile polyps (2 of 24, 8%). Our results indicate that the multiple genetic alterations involved in usual colorectal neoplasia also play a role in neoplastic transformation of juvenile polyps, predominantly in juvenile polyposis syndrome.

Adenomatous Polyposis Coli↗

PubMed1997

Malignant epithelial neoplasm consistent with primitive cystic hepatic neoplasm with mesothelial differentiation: a case report.

Mesothelioma are primary tumors of the celiomic cavity and are seen more often in adults than in children: only an estimated 2-5% of all cases present within the first two decades of life. To best knowledge of the reviewing world literature reported to date, no more than 80 proved cases of this tumor have occurred in children. One-third of mesothelioma originate in the peritoneum and two-thirds arise in the pleural cavity. Mesothelioma of the liver are extremely rare; a review of the English literature shows only three adult cases that have been reported as fibrous mesothelioma of the liver; experience with these cases suggests a high potential for recurrence, but no progression to malignancy. Cystic mesothelioma occur mainly in adults and are considered to be benign and curable. We describe a case of malignant epithelial neoplasm consistent with primitive cystic hepatic neoplasm with mesothelial differentiation arising in a 3-year-old boy, a condition which has never before been reported in childhood. Malignant primitive cystic mesothelioma is possible that some cases of intraabdominal mesenchymoma or hamartoma with malignant differentiation may have been misdiagnosed in the past; future cases should be fully evaluated, to establish the true incidence of mesothelioma disease in children.

Child, Preschool↗

PubMed1997

Development of human prostate cancer models for chemoprevention and experimental therapeutics studies.

The progression of human prostate cancer from histomorphologic to clinical expression often requires several decades. This study emphasizes the importance of developing relevant human prostate cancer models to study the molecular events leading to prostate cancer progression. These models will provide a rational basis for chemopreventive and treatment strategies to retard the progression of human prostate cancer from its localized to its metastatic state. In our laboratory, we have established the LNCaP progression and ARCaP models and the in vitro three-dimensional growth models involving prostate cancer and bone stroma to study the progression of prostate cancer. We propose that prostate cancer may progress from an androgen-dependent to an androgen-independent state. While existing as androgen-independent tumors (defined as tumors capable of growing in castrated hosts and secreting PSA in serum), prostate cancer may assume three different phenotypes as it progresses: androgen-independent while remaining androgen-responsive; androgen-independent and unresponsive to androgen stimulation; and androgen-independent but suppressed by androgen. It is conceivable that any androgen-independent human prostate cancer may contain variable proportions of cells that exhibit these three phenotypes. This concept may have important implications in determining strategies for chemopreventive and therapeutic trials. We have established three-dimensional growth models of prostate cancer cells either in collagen gel or microgravity-simulated growth conditions to form viable and functional organoids which contain prostate cancer epithelial cells admixed with prostate or bone stromal cells. These in vitro models combined with the in vivo models described above will enhance our understanding of the regulatory mechanism of prostate cancer growth and progression, and hence could improve efficiency in screening chemopreventive and therapeutic agents which alter the biologic behaviors of human prostate cancer.

Androgens↗

PubMed1996

Prognostic value of TP53 and K-ras-2 mutational analysis in stage III carcinoma of the colon.

BACKGROUND: Genetic mutations involving oncogenes and tumor-suppressor genes occur in carcinogenesis, and may affect biologic behavior of neoplasms. In this study, we analyzed the prognostic value of mutational analysis in colon carcinoma. PATIENTS AND METHODS: Archival pathology specimens from 70 consecutive patients, resected for stage III colon carcinoma, were analyzed for point mutations by amplification and direct sequencing of exons from the K-ras-2 and the TP53 genes (topographic genotyping). Mutations were compared with adverse histopathologic features (poor differentiation, vascular and lymphatic invasion, mucin production) as prognostic markers. RESULTS: Five-year survival was 75% in patients with nonmutated lesions, significantly lower (21%) with TP53 mutations (P = 0.01), and intermediate with K-ras-2 only (45%) or both K-ras-2 and TP53 mutations (36%). A TP53 mutation carried the highest relative risk of death (2.39; 95% confidence interval, 1.29 to 4.42; P = 0.006). There was an additive effect on the risk of death between TP53 mutations and adverse histopathologic features. CONCLUSIONS: The information derived from mutational analysis is creating new prognostic variables that may play a role in the choice of therapy for colorectal carcinoma.

Aged↗

PubMed1996

Recurrent Epstein-Barr virus-associated lesions in organ transplant recipients.

Posttransplant lymphoproliferative disorders (PTLD) are related to Epstein-Barr virus (EBV) and range from lymphoid hyperplasias to lymphomas. The authors report 11 transplant recipients with recurrent EBV-associated lesions. Four patients presented with EBV-positive mononucleosis-like lymphadenitis. One had recurrence of a similar lesion and the other three developed polymorphic PTLDs. Matched clonal studies in one patient showed clonal lymphoid and EB viral populations in the recurrent lesion, but not in the initial lesion. Six patients presented with polymorphic PTLDs. Five later developed histologically dissimilar tumors that resembled non-Hodgkin's lymphoma (two B-cell and one T-cell origin), Hodgkin's disease (one patient), or smooth muscle tumor (one patient). Matched clonal studies were available from one patient and showed that the primary and recurrent lesions were clonally distinct. The sixth patient had recurrence of histologically and clonally identical polymorphic PTLD. One patient presented with monomorphic PTLD and developed recurrence of a clonally identical tumor after a 6-month remission. This study shows that a few patients with EBV-associated lesions have clinical recurrence, which may be either a relapse of the original process or a new EBV-associated lesion. In some patients, the new lesion appeared to represent a more fully developed malignancy that did the antecedent lesion.

Adolescent↗