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T T Yip

Publications and source records attributed to T T Yip.

At least 19 recordsLinked to original sources
PubMed2001

Remarkable application of serum EBV EBER-1 in monitoring response of nasopharyngeal cancer patients to salvage chemotherapy.

Nineteen consecutive patients with metastatic or recurrent nasopharyngeal cancer (NPC) receiving combination chemotherapy were monitored for EBV DNA in their serum. EBV DNA (EBER-1) concentration in serum was measured before, during, and after chemotherapy. Thirteen patients had additional multiple prechemotherapy readings. There was a significant lead time from first detection of serum EBER-1 to clinical recurrence in 62% of patients by a mean of 17.4 weeks (range: 8-74.5 weeks; mean = 28.2 weeks if confined to the 8 patients with significant lead time). The median EBER-1 concentration was significantly higher in those with distant metastasis as compared to those with loco-regional recurrence only (17,468 vs. 684 pg/mL serum; p = 0.046, Mann-Whitney U test). Among the 13 patients who responded to chemotherapy, 4 exhibited clinical complete remission (CR) who were only found in the group with EBER-1 DNA drop to background level, while the magnitude of EBER-1 drop did not discriminate partial remission (PR) and stable disease (SD) patients clearly. Subsequent profile of EBER-1 DNA showed concordance with clinical course of either continuous remission or later progression. EBER-1 DNA in serum can become a useful adjunctive surrogate marker to monitor chemotherapeutic response in NPC patients with distant metastasis or advanced local recurrence.

DNA, Viral↗
PubMed1998

Direct evidence of the generation in human stomach of an antimicrobial peptide domain (lactoferricin) from ingested lactoferrin.

The ability to define specific alterations in the structure and function of proteins as they are introduced and processed in vivo remains an important goal. We have evaluated the generation, in vivo, of an antimicrobial peptide (lactoferricin) derived from ingested bovine lactoferrin by surface-enhanced laser desorption/ionization (SELDI). SELDI was used in the affinity mass spectrometry operational mode to detect and quantify lactoferricin directly from unfractionated gastric contents using a chemically defined ligand with a terminal n-butyl group as the lactoferricin affinity capture device. By this method, we were able to detect and quantify lactoferricin directly upon examination of unfractionated gastric contents recovered from an adult subject 10 min after ingestion of bovine lactoferrin (200 ml of 10 mg/ml (1.2 x 10(-4) mol/l) solution). Lactoferricin produced in vivo was directly captured by a surface-enhanced affinity capture (SEAC) device composed of molecules with a terminal n-butyl group and analyzed by laser desorption/ionization time-of-flight mass spectrometry. The recovery of standard lactoferricin or lactoferrin added to an aliquot of the gastric contents was determined to be nearly 100%, confirming the efficiency of this method. The amount of lactoferricin detected in the gastric contents was 16.9+/-2.7 microg/ml (5.4+/-0.8 x 10(-6) mol/l). However, a large proportion of ingested lactoferrin was found to be incompletely hydrolyzed. Lactoferrin fragments containing the lactoferricin region were analyzed by in situ pepsin hydrolysis after being captured on the SEAC device. Partially degraded lactoferrin fragments containing the lactoferricin region, including fragments corresponding to positions 17-43, 17-44, 12-44, 9-58 and 16-79 of the bovine lactoferrin sequence, were found to be present at concentrations as high as 5.7+/-0.7 x 10(-5) mol/l. These results suggest that significant amounts of bovine lactoferricin would be produced in the human stomach following ingestion of food, such as infant formula, supplemented with bovine lactoferrin. We propose that physiologically functional quantities of human lactoferricin could be generated in the stomach of breast-fed infants, and possibly, in the case of adults, from lactoferrin secreted into saliva.

Amino Acid Sequence↗
PubMed1998

Prognostic significance of DNA flow cytometric analysis in patients with nasopharyngeal carcinoma.

BACKGROUND: Nasopharyngeal carcinoma (NPC) is a prevalent malignant tumor among Southern Chinese. Previously, the authors described the prognostic significance of a serum antibody assay to a recombinant Epstein-Barr virus Bam HI-Z replication activator protein (ZEBRA) in NPC patients with long term follow-up. In this study, the authors further reported the use of DNA flow cytometry (DNA-FCM) as an additional technique for determining the prognosis of NPC patients in the same series. METHODS: One hundred and forty-three archival biopsies from 110 NPC patients were deparaffinized and subjected to DNA-FCM analysis. DNA ploidy state and various proliferative indices (PI) of the tumors were correlated with patient survival and frequency of recurrence. RESULTS: Among the biopsies analyzed, 119 were histologically positive NPC and 24 were negative. Fifty-one tumor biopsies that fulfilled the guideline criteria of the DNA Cytometry Consensus Conference were correlated with the clinical manifestations of the patients. Among them, 43 tumors (84%) were DNA diploid and 8 (16%) were aneuploid. Two PI, S-phase fraction (SPF) and proliferation fraction (PF), appear to be potentially useful prognostic indicators. For example, PF in patients who developed locoregional recurrence (15.1%) and distant recurrence (16.4%) after radiation therapy both were significantly higher than PF in patients who were in complete remission (8.2%) (P = 0.0005 and P = 0.004, respectively). Significant differences in SPF between patients with distant recurrence (10.6%) and those in remission (5.7%) also was found (P = 0.005). Using Kaplan-Meier analysis, patients with high PF, high SPF, and aneuploid tumors had significantly poorer 12-year survival rates (35%, 26%, and 28%, respectively) than those patients with low PF, low SPF, and diploid tumors (77%, 67%, and 59%, respectively) (P < 0.0009, P < 0.004, and P < 0.01, respectively). CONCLUSIONS: Determination of tumor PI and DNA ploidy state by DNA-FCM at diagnosis of NPC can be potentially useful in selecting a poor prognostic subgroup of NPC patients. These parameters may enable oncologists to plan for more stringent treatment strategies such as hyperfractionated and accelerated radiation therapy or concomitant chemoradiotherapy for these patients.

Biopsy↗
PubMed1998

The survival of ingested lactoferrin in the gastrointestinal tract of adult mice.

Lactoferrin is an 80 kDa major protein component of mammalian colostral whey. The antimicrobial active centre of lactoferrin, lactoferricin (Lfcin), may also be an important determinant of the interaction between lactoferrin and specific receptors on lymphocytes. We have documented the survival in vivo of ingested lactoferrin in the gastrointestinal tract of adult mice by surface-enhanced laser desorption/ionization affinity MS. Various kinds of degraded lactoferrin fragments were detected as molecular-ion peaks corresponding to Lfcin after being captured by an affinity capture device, hydrolysis in situ and laser desorption/ionization. No evident molecular-ion peaks of Lfcin were observed upon analysis of faeces from mice fed commercial milk, whereas lactoferrin fragments containing the Lfcin region were detected at concentrations in the order of at least pmol/g in the faeces of mice fed milk enriched with lactoferrin at 40 mg/ml. These results suggest that ingested lactoferrin would survive transit through the gastrointestinal tract as partially degraded forms containing the receptor-binding region(s) as well as the antimicrobial active centre.

Animals↗
PubMed1998

Bactericidal domain of lactoferrin: detection, quantitation, and characterization of lactoferricin in serum by SELDI affinity mass spectrometry.

Lactoferricin is a bioactive peptide fragment (3196 Da) derived from lactoferrin (80 kDa) that contains the bactericidal domain and the lymphocyte receptor-binding domain of lactoferrin. Although lactoferricin has been produced from lactoferrin by proteolytic digestion in vitro, its natural occurrence and distribution in vivo are still not clear, in part because of the absence of a suitable detection means. Surface-enhanced laser desorption/ionization (SELDI) was used to detect and characterize lactoferricin by affinity mass spectrometry. Human, porcine, and bovine lactoferricin in unfractionated serum samples were found to bind specifically to ligands presenting a terminal n-butyl group. SELDI was used to detect and quantify each species of lactoferricin in a manner that was independent of the presence of intact lactoferrin, partially degraded lactoferrin, and lactoferrin peptides containing the lactoferricin peptide sequence. The limit of detection of bovine lactofericin in serum was as low as 200 pg/ml. The FKCRRWQWR-homoserine/-homoserine lactone moiety of bovine lactoferricin, which includes the complete antimicrobial center (i.e., RRWQWR), was shown to be responsible for interaction with the n-butyl group. The SELDI procedure defined here is the only molecular recognition tool known to date that is capable of distinguishing the multi-functional lactoferricin domain located within structurally related but distinct forms of lactoferrin and its metabolic fragments. Enabling the direct quantitation of lactoferricin produced in vivo opens new opportunities to evaluate lactoferrin function.

Amino Acid Sequence↗
PubMed1998

Direct detection and quantitative determination of bovine lactoferricin and lactoferrin fragments in human gastric contents by affinity mass spectrometry.

Lactoferricin (Lfcin) is a bioactive fragment of lactoferrin derived from the bactericidal and putative lymphocyte receptor binding domain(s) located within the N-lobe of lactoferrin. Although known to be liberated from at least three species of lactoferrin, conditions leading to Lfcin generation in vivo and factors affecting its distribution are still not known. Recently, we have developed a method of surface-enhanced laser desorption/ionization (SELDI) affinity mass spectrometry using n-butyl terminal groups for surface-enhanced affinity capture (SEAC) to quantify not only Lfcin generated in vivo but also other lactoferrin fragments. Unlike previous efforts to detect lactoferrin and Lfcin with specific antibodies, the SELDI affinity assay distinguished lactoferrin, lactoferrin fragments, Lfcin and unrelated peptides without their interference with each other. To evaluate Lfcin generation in vivo, the experimental design involved feeding 200 mL of 10 mg/mL (1.22 x 10(-4) mol/L) bovine lactoferrin to an adult. Gastric contents were recovered 10 min after ingestion. Lfcin produced in vivo was directly captured by the SEAC device. The amount of Lfcin in the gastric contents was 16.91 +/- 2.65 micrograms/mL (5.350 +/- 0.838 x 10(-6) mol/L). However, a large proportion of the ingested lactoferrin was not completely digested. Lactoferrin fragments containing the Lfcin region were analyzed by in situ hydrolysis with pepsin after being captured by the SEAC device. As much as 5.740 +/- 0.702 x 10(-5) mol/L of the partially degraded lactoferrin fragments were found to contain the Lfcin region, including peptide domains 17-43, 17-44, 12-44, 9-58, and 16-76 of bovine lactoferrin. These results show that bovine Lfcin can be produced in the human stomach after ingestion of an infant formula supplemented with bovine lactoferrin. It is now important to determine whether Lfcin is generated in the intestinal tract of formula-fed and breast-fed infants, and geriatric patients consuming foods enriched with lactoferrin.

Adult↗
PubMed1997

Phosphorylation of human progesterone receptor by cyclin-dependent kinase 2 on three sites that are authentic basal phosphorylation sites in vivo.

The human progesterone receptor (hPR) in T47D breast cancer cells is phosphorylated on at least nine different serine residues. We have previously reported the identification of five sites; three are hormone inducible (Ser102, Ser294 and Ser345), and their phosphorylation correlates with the timing of the change in receptor mobility on gel electrophoresis in response to hormone treatment. The other two sites, Ser81 and Ser162, along with the remaining sites, are basally phosphorylated and exhibit a general increase in phosphorylation in response to hormone. With the exception of Ser81, all of these sites are in Ser-Pro motifs, suggesting that proline-directed kinases are responsible for their phosphorylation. We now report that cyclin A-cyclin-dependent kinase-2 complexes phosphorylate hPR-B in vitro with a high stoichiometry on three sites that are authentic basal sites in vivo. One of these is Ser162, which has been described previously. The other two sites are identified here as Ser190 and Ser400. The specificity and stoichiometry of the in vitro phosphorylation suggest that hPR phosphorylation may be regulated in a cell cycle-dependent manner in vivo.

Amino Acid Sequence↗
PubMed1996

Cryptic antigenic determinants on the extracellular pyruvate dehydrogenase complex/mimeotope found in primary biliary cirrhosis. A probe by affinity mass spectrometry.

Affinity mass spectrometry (AMS) was used to evaluate the structural diversity of the E2 component of pyruvate dehydrogenase complex (PDC) in normal and diseased liver cells, including those from patients with the autoimmune disease primary biliary cirrhosis (PBC). Two different antibodies to PDC-E2, the immunodominant mitochondrial autoantigen in patients with PBC, were used. AMS was performed directly on frozen liver sections and purified bile duct epithelial cells. Mass spectrometric signals associated with the molecular recognition of PBC-specific antigenic determinants were enhanced by an in situ enzyme-linked signal amplification process. Samples from patients with PBC gave strong positive signals for the antigen(s) recognized by the monoclonal antibody C355.1. Conversely, tissues from normal and disease controls showed only a minimal signal. AMS was used to identify specific antigenic determinants within the E2 component of PDC for comparison with unknown antigenic determinants observed by affinity capture with C355.1 monoclonal antibody from PBC samples. PDC components bound to C355.1 were mapped and identified by mass before dissociation from the E2 component. A similar approach was used to identify unknown antigenic determinants associated with PBC. We believe AMS may be an important new approach with wide application to the identification of molecules associated with a number of disease states.

Antibodies, Monoclonal↗
PubMed1996

Quantitative analysis of oligonucleotides by matrix-assisted laser desorption/ionization mass spectrometry.

Quantitative aspects of oligonucleotide analysis by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry remain largely unexplored relative to the efforts that have been devoted to quantitative peptide and protein analysis. The successful quantitation of these other biopolymers coupled with the potential of rapid nucleic acid analysis by desorption/ionization techniques prompted the present investigation into quantifying mixed base oligonucleotides of intermediate molecular weights. This report describes the concentration-dependent desorption/ionization of a 21-base oligonucleotide (MW 6361) using a 36-base oligonucleotide (MW 11 131) as an internal standard. Peak height and peak area ratios (analyte to internal standard) varied linearly as a function of oligonucleotide concentration (R2 = 0.966 and 0.991, respectively). The linearity of response extended over nearly three orders of magnitude, from 0.125 to 100 pmol of analyte applied. The use of an internal standard improved the linearity of the calibration curve and reduced relative standard deviations. These results demonstrate for the first time the quantitation of medium size oligonucleotides using MALDI.

Calibration↗
PubMed1995

Basaloid-squamous carcinoma of the nasopharynx. An Epstein-Barr virus-associated neoplasm compared with morphologically identical tumors occurring in other sites.

BACKGROUND: Basaloid-squamous carcinoma is a newly characterized, highly aggressive neoplasm occurring mostly in the base of tongue, hypopharynx, larynx, and esophagus. Its occurrence in the nasopharynx is rare. METHODS: The clinicopathologic features of three cases of basaloid-squamous carcinoma of the nasopharynx are described and were studied for the presence of Epstein-Barr virus (EBV) by in situ hybridization for EBV-encoded small nuclear RNA (EBER). For comparison, basaloid-squamous carcinomas occurring in other sites also were studied for the presence of EBV. RESULTS: EBER was detected in all 3 cases of basaloid-squamous carcinoma occurring in the nasopharynx, but in none of the 13 cases from other sites including the esophagus, larynx, pharynx, hypopharynx, and nasal cavity. The nasopharyngeal basaloid-squamous carcinomas occurred in two male and one female patients with an age range of 48-70 years. The serum immunoglobulin A against the EBV-viral capsid antigen was elevated in all three cases. Two patients developed cervical lymph node involvement during the course of the disease. All three patients were treated by radiotherapy and survived for longer than 34 months compared with the average reported median survival of approximately 2 years for basaloid-squamous carcinomas occurring in the usual sites. CONCLUSION: Based on this limited study, basaloid-squamous carcinoma occurring in the nasopharynx appears to be an EBV-associated neoplasm, whereas the same tumor occurring in other sites is not. The prognosis is potentially better for patients with nasopharyngeal basaloid-squamous carcinoma, which appears to be pathogenetically and biologically more related to the much more common nasopharyngeal undifferentiated carcinoma.

Aged↗
PubMed1995

Primary lymphoepithelioma-like carcinoma of the lung. A clinicopathologic study of 11 cases.

BACKGROUND: Lymphoepithelioma-like carcinoma (LELC), best known to occur in the nasopharynx, can arise in a variety of sites, such as the salivary gland, thymus, lung, stomach, and skin. Primary LELC of the lung is very rare, with only limited information in the literature. METHODS: The clinicopathologic features of 11 patients with pulmonary LELC collected from two regional hospitals in Hong Kong are described. RESULTS: The patients, all Chinese, were aged 38 to 73 years (median, 54 years), with equal sex incidence. Two of the 8 patients were smokers. Four presented with coin lesions incidentally discovered on chest X-ray, five with cough and blood-stained sputum, and two with pleural effusion. The tumor formed a discrete (9 patients) or an ill-defined (1 patient) nodule in the lung, or, rarely, showed extensive bilateral pulmonary involvement (1 patient). The major bronchi were not involved except in 1 patient. Three patients had lymph node metastasis at presentation; two of them had bone metastasis, one at presentation and one after 9 months. The tumors had pushing margins, and grew in the form of anastomosing islands and sheets, comprising syncytial-appearing large cells with vesicular nuclei and prominent nucleoli. They were infiltrated by an appreciable number of small lymphocytes and plasma cells. Intratumoral amyloid globules were found in one tumor. In five patients, the tumor showed intraepithelial growth within the small bronchi; this could represent either the in-situ phase of the tumor or pagetoid spread into the bronchial epithelium. The neoplastic cells of all patients harbored Epstein-Barr virus (EBV) as demonstrated by in situ hybridization for EBV-encoded small nuclear RNAs. All eight Asian patients with pulmonary LELC previously reported in the literature similarly have been EBV-positive, whereas the four reported Caucasian patients all have been EBV-negative. CONCLUSION: Lymphoepithelioma-like carcinoma of lung occurring in Asians is an EBV-associated neoplasm; it also appears to occur at a higher frequency in Asians than Caucasians. It usually presents as a solitary subpleural nodule, and there is no strong association with cigarette smoking. Most patients have early stage disease at presentation. From the limited available data, the behavior of LELC of lung is highly variable, ranging from apparent curability by excision (particularly for localized disease) to highly aggressive, extensive disease at presentation.

Adult↗
PubMed1995

Detection of Epstein-Barr virus in Hodgkin's disease occurring in an Oriental population.

Like Burkitt's lymphoma, the strength of association of Epstein-Barr virus (EBV) with Hodgkin's disease occurring in different populations and clinical settings is highly variable, being 30% to 50% in Western countries, nearly 100% in Third World countries like Peru and Honduras, and nearly 100% in patients seropositive for human immunodeficiency virus. Data on the Oriental populations are very limited. Therefore, the current study was performed on the Chinese population of Hong Kong, where the incidence of Hodgkin's disease is low and EBV seroconversion occurs early in life. Twenty-three consecutive samples of Hodgkin's disease collected from 18 male and five female patients over a 12-year period were studied. The first age peak occurred in the second decade of life, and the second peak in the seventh decade. Using the sensitive and specific EBV-encoded RNAs (EBERs) in situ localization technique, positive labeling of the Reed-Sternberg cells and their variants was detected in five of five samples (100%) of mixed cellularity, nine of 16 samples (56%) of nodular sclerosing, one of one sample (100%) of lymphocyte depleted, and none of one sample (0%) of nodular lymphocyte predominant Hodgkin's disease. Further analysis of the data by age group yielded the following results: four of five (80%) for age younger than 15 years, three of nine (33%) for age 15 to 49, and eight of nine (89%) for age 50 or higher, confirming the reported strong association of EBV with Hodgkin's disease at the extremes of life. The overall positivity rate was 65%, which was intermediate between that reported in the Western populations and that in the Third World countries. These findings can be explained by the epidemiological pattern of Hodgkin's disease in Hong Kong, in which the first age peak is left-shifted to a younger age compared with that of Western populations (but not as early as that observed in Third World countries), moving the peak toward an age bracket in which Hodgkin's disease shows stronger association with EBV.

Adolescent↗
PubMed1994

A possible prognostic role of immunoglobulin-G antibody against recombinant Epstein-Barr virus BZLF-1 transactivator protein ZEBRA in patients with nasopharyngeal carcinoma.

BACKGROUND: Epstein-Barr virus BZLF-1 replication activator (ZEBRA) is involved in the switch from viral latency to a productive cycle. Previous immunofluorescent study has shown that patients with nasopharyngeal carcinoma (NPC) have elevated immunoglobulin-G (IgG) antibody titres against recombinant ZEBRA protein (ZEBRA/IgG). METHODS: The prognostic role of ZEBRA/IgG was further investigated by enzyme-linked immunosorbent assay (ELISA) in 110 NPC patients under long period of clinical follow-up. RESULTS: Ninety-seven percent (85 of 88) of the patients with NPC had significantly higher ZEBRA/IgG titres (geometrical mean titre, i.e., GMT = 8397) than normal Chinese individuals (GMT = 233 and P < 0.0001). Based on Kaplan-Meier analysis, the actuarial survival in patients with high ZEBRA/IgG titres (25%) after radiotherapy was significantly lower than that of those with low (76%; P = 0.0008) or intermediate titres (62%; P = 0.0036), although the titres taken before treatment did not bear such a relationship. Subdividing the patients into either individual UICC or Ho's stages, those with late-stage disease (UICC Stage 4 and Ho's Stages 3 and 4) and with high ZEBRA/IgG titres also had poorer prognosis than those with disease of the same stages but who had low titres. Poor prognosis in those with high titres could be associated with a high risk of distant metastasis because consistent titre increase was found in the majority of patients who later developed distant metastasis either in the lung or liver. Only a minimal increase was found in patients with recurrence in the cervical lymph nodes. No consistent increase was observed, however, in patients whose disease was in remission or the majority of those with bone metastasis or local recurrence in the nasopharynx. CONCLUSION: The postradiotherapy ZEBRA/IgG titre could be a potentially useful marker for differentiating NPC patients with poor prognosis from those at high risk for the development of distant metastasis to the lung or liver.

Biomarkers, Tumor↗
PubMed1994

Immobilized metal ion affinity chromatography.

This article describes the technique of immobilized metal ion affinity chromatography (IMAC). The IMAC stationary phases are designed to chelate certain metal ions that have selectivity for specific groups in peptides and on protein surfaces. The number of stationary phases that can be synthesized for efficient chelation of metal ions is unlimited, but the critical consideration is that there is enough exposure of the metal ion to interact with the proteins, preferably in a biospecific manner. The versatility of IMAC is one of its greatest assets. An important contribution to the correct use of IMAC for protein purification is a simplified presentation of the various sample elution procedures.

Amino Acid Sequence↗
PubMed1994

In situ localization of Epstein-Barr virus encoded RNA in non-nasal/nasopharyngeal CD56-positive and CD56-negative T-cell lymphomas.

We recently reported a group of non-nasal/nasopharyngeal hematolymphoid malignancies expressing the natural killer cell marker CD56, characterized by frequent extranodal localization, angiocentricity, and aggressive clinical course (HUM PATHOL 23:798-804, 1992). Because we have shown a very strong association of Epstein-Barr virus (EBV) with CD56-positive T-cell lymphomas of the nose nasopharynx, we asked whether a similar association also occurs with the non-nasal CD56-positive T-cell lymphomas. In situ localization of EBV encoded RNA (EBER) was performed on paraffin sections of 15 such cases, including the nine previously reported cases and six new cases (three showing prominent hepatosplenic involvement and three showing involvement of one or more extranodal sites, such as the parotid gland, tonsils, gastrointestinal tract, skeletal muscle, and testis). A case was considered positive when the majority of the tumor cells showed nuclear signal. Ten cases showed EBER positivity, and all but one of them were negative for CD3 and other T-cell markers, except CD2. Only one of four cases showing a CD3-positive phenotype was EBER positive. Of the remaining two CD3-negative EBER-negative cases, one showed a histiocytic phenotype and the other was positive for multiple T-cell markers. Among 15 cases of CD56-negative non-nasal peripheral T-cell lymphoma studied for comparison, six were CD3-negative, among which three showed EBER positivity. All nine CD3-positive cases were EBER negative. Five cases (three CD3 positive and two CD3 negative) showed rare isolated (< 1%) EBER-positive tumor cells. We conclude that among non-nasal T-cell lymphomas, EBV is strongly correlated with CD56 positivity (66.7% v 20%), and the positive cases almost always show an immunophenotype identical to that commonly observed in nasal lymphomas (CD2 positive, CD3 negative, and CD56 positive). Thus, EBV may play an etiologic role in these CD56-positive lymphomas. There is also a correlation between EBER positivity and CD3 negativity, irrespective of the CD56 status. The presence of isolated EBER-positive cells in CD56-negative T-cell lymphomas, occurring at a frequency similar to that reported in the European population, probably represents secondary infection of tumor cells.

Adult↗