Biomedical subjects

E C Chew

Publications and source records attributed to E C Chew.

At least 55 records · Page 3Linked to original sources

PubMedDate not supplied

Establishment and characterization of two new cell lines derived from squamous cell carcinoma of the tongue in Chinese patients.

Two new cell lines derived from squamous cell carcinoma of the tongue, T1/CUHK and T2/CUHK, have been established in culture. Analysis of the morphology, ultrastructure, chromosome number, spheroid formation and immunohistochemical properties of the two cell lines demonstrated that they are both well characterized. T1/CUHK cells grew relatively faster than T2/CUHK cells. Both cell lines were tumorigenic after inoculation into made mice and showed positive reactivity with HPV 16 DNA probe. The reactivity of both cell lines with HPV 18 DNA probe was weak.

Animals↗

PubMedDate not supplied

Distribution of a novel nuclear protein in normal and regenerating liver cells.

Monoclonal antibodies to a rat liver nuclear protein (B2, 68 kda, pI: 6.5-8.2) have been established and characterized to localize the distribution of this antigen in nuclear organization. It was demonstrated that this nuclear protein B2 is associated with actively transcribed nucleosomes and the nuclear matrix as revealed by immunogold labelling. In the regenerating liver cell, the immunogold particles are predominantly in the euchromatin as compared to the resting liver cells which are mainly in nuclear matrix and heterochromatin. It was also demonstrated that the incorporation of 32P into the nuclear protein B2 is increased 6-fold in the actively transcribed nucleosomes as compared to the nuclear matrix, as analyzed by two-dimensional polyacrylamide gel electrophoresis. We hypothesize that this nuclear protein may act as an anchorage point either for actively transcribed RNA or for DNA replication. Once this protein is highly phosphorylated, it dissociates from the nuclear envelope and can then dynamically interact with active nucleosomes within the nucleus.

Animals↗

PubMedDate not supplied

Lectin histochemistry of normal and neoplastic nasopharyngeal epithelium.

The cell surface carbohydrate profile of formalin-fixed paraffin-embedded tissue sections of normal and neoplastic epithelium was evaluated using 9 plant lectins. Three lectins, namely Con A, RCA and WGA, showed a similar pattern and staining intensity from normal epithelium to metaplastic squamous epithelium and nasopharyngeal intraepithelial neoplasia (NPIN). However, a decrease in staining reactivity was observed in undifferentiated nasopharyngeal carcinoma. Significant differences in intensity and distribution were seen in UEA and cryptic PNA residue (after neuraminidase pretreatment) from normal nasopharyngeal epithelium to NPIN. Infiltrative undifferentiated carcinomas showed a heterogenous lectin binding pattern and altered intensity of lectin binding in one case of DBA and three cases of PNA (no neuraminidase pretreatment), suggesting a variation in expression of carbohydrate by tumour cells. These results indicate that neoplasia in nasopharyngeal epithelium is associated with alterations in terminal sialic acid, -Fucose residues and -Gal-D-GalNac residues present in the outer parts of glycoconjugates. SBA, VVL and BSL failed to stain any types of epithelia. Desialylation of tissues by preincubation with neuraminidase did not expose DBA, SBA, VVL and BSL binding sites. These findings may be used as a baseline for evaluation of lectin binding in preinvasive and invasive lesions of the nasopharynx.

Biopsy↗

PubMedDate not supplied

Immunogold localization of a nuclear protein at different stages of the cell cycle in normal and tumor cells.

The interaction of immunogold particles with a specific antigen was used to localize this nuclear protein (Mr 68 kd, pI 6.5-8.2) in fetal liver cells and oesophageal carcinoma cells at different stages of the cell cycle. In interphase hepatocytes, the 68 kd antigen was localized exclusively in the nucleus and associated with both heterochromatin and euchromatin. As the chromatin condensed into chromosomes at later stages of the cell cycle, the 68 kd antigen remained closely associated with them. Similar phenomena were observed in the oesophageal carcinoma cells, suggesting that this 68 kd nuclear protein may be involved in anchoring the actively transcribed DNA and in maintaining the chromosomal architecture during the cell cycle.

Animals↗

PubMedDate not supplied

Expression of a new surface membrane antigen (SQM1) in tumor cells cultured in media with different calcium ion levels.

Terminal differentiation is usually achieved in normal as well as transformed squamous epithelial cells when cultured. On the other hand, tumor cells at various differentiation stages and with different biological characteristics comprise the heterogeneous properties of tumors which have been one of the barriers to effective treatments. Recently, a surface membrane protein has been reported in squamous cell carcinomas of the head and neck, which is recognized by a murine monoclonal antibody, SQM1. This glycoprotein was further suggested to be related to squamous cell differentiation and intercellular adhesion. In a recent study, the esophageal carcinoma cells of EC/CUHK2 cell line were induced to various differentiation stages as evidenced by the increasing amount of intracellular desmosomes and tonofilaments and greater binding ratios of cytokeratin and involucrin antibodies than in those cells that maintained lower calcium ion concentrations. The expression of SQM1 antigen was found to increase in intensity when the tumor cells were cultured in moderate to high calcium ion levels for 10 to 15 hours when the differentiation patterns were beginning to appear. The intensity declined gradually thereafter. Thus SQM1 protein might be related to the stage when the cells started committing with squamous differentiation.

Antibodies, Monoclonal↗

PubMedDate not supplied

Organization and modulation of a novel nuclear phosphoprotein during rat spermatogenesis.

The localization and distribution of the B2 nuclear phosphoprotein in spermatogenesis in the rat were studied by immuno-gold electron microscopy. In spermiogenesis, the phosphoprotein B2 was shown to have phase-dependent changes in number and distribution. A temporal increase in synthesis of this protein was observed during spermiogenesis. The high quantity of this protein in the mature sperm head suggests its role in maintenance and organization of DNA.

Animals↗

PubMedDate not supplied

Integration of HPV-16 DNA in cervical carcinoma cell line CC3/CUHK3 and its xenografts.

A recently established cell line, designated CC3/CUHK3, derived from a squamous cell carcinoma of the uterine cervix of a Hong Kong Chinese patient was investigated for its association with human papillomavirus (HPV) by Southern blot hybridization studies. A "grafted tumour" or xenograft of CC3/CUHK3 has also been successfully established in athymic mice, which showed similar histology to that of the original biopsy. The epithelial nature of the xenografts, like the original biopsy. The epithelial nature of the xenografts, like the original tumour specimen, was also confirmed by transmission electron microscopy which demonstrated the presence of desmosomes and tonofilaments. Moreover transmission electron microscopic examination revealed no HPV particle in either the tumour biopsy or the xenograft tissues. Analysis of the DNA samples extracted from the cervical cancer cell line and the xenograft tissues derived from it showed the presence of HPV type 16 DNA. No DNA sequence related to HPV type 6, 11, or 18 was demonstrated. The viral DNA was found to be integrated into the cellular genome at multiple sites as single copy or head-to-tail tandem repeats. Deletion or rearrangement of the HPV DNA had probably occurred on or subsequent to integration. Viral sequence deletion has also been observed in the grafted tumours derived from CC3/CUHK3.

Animals↗

PubMedDate not supplied

Characteristics of a cell line established from a Chinese patient with a squamous carcinoma of the uterine cervix.

A new cell line, CC3/CUHK3, was established from a squamous carcinoma of the uterine cervix from a Chinese patient. Light microscopy of the cell line revealed keratin and electron microscopy demonstrated tonofilaments and desmosomes, thereby confirming its epithelial nature. The population doubling time of CC3/CUHK3, estimated from the exponential growth phase of the growth curve established from the cell line was 42 hours. When the tumour cells were inoculated into athymic mouse, a tumour, microscopically diagnosed as a well-differentiated carcinoma, developed. These cells are highly invasive in vitro.

Animals↗

PubMedDate not supplied

Ultrastructural localization of a new surface membrane antigen (SQM1) related to squamous differentiation.

Normal squamous epithelial cells readily undergo terminal differentiation in culture and are commonly used in differentiation studies. Several intracellular markers of squamous differentiation such as keratin, involucrin, transglutaminase and cholesterol sulfate have been well-studied and described by other workers. We have recently reported a surface membrane antigen in squamous carcinoma of the head and neck antigen in squamous carcinoma of the head and neck which is recognized by a murine monoclonal antibody SQMI. In this paper, we present our studies on the ultrastructural localization of SQMI antigen in cultured squamous epithelial cells using gold-labelled antibody. The cells studied included both normal and cancer cells at different degrees of differentiation. Under both transmission and scanning electron microscopy examination, the SQMI antigen was localized at the membrane surface of cultured cells, particularly at sites of cell-cell interdigitation. No association with desmosomal structure was observed in any of the specimens examined. There was however an association of SQMI antigen with microvilli of cell membrane. No non-specific cytoplasmic localization of SQMI antigen was observed. The intensity of SQM1 antigen revealed by gold-labelling appeared to have a positive correlation with the degree of differentiation of the cells in culture.

Antibodies, Monoclonal↗

PubMedDate not supplied

Ultrastructural studies on interactions of choriocarcinoma cells with stromal cells in monolayers.

Choriocarcinoma is a common cancer in the tropical and subtropical areas including Taiwan, Hong Kong and Japan. An experimental model consisting of monolayer of decidual or smooth muscle cells growing on collagen gels was established to study the invasiveness of choriocarcinoma cells in vitro. It was found that tumour cells induced retraction of stromal cells in the process of invasion.

Animals↗

PubMedDate not supplied

In vitro studies on the invasion of blood vessel wall by choriocarcinoma cells.

The development of metastases represents the lethal event in the clinical course of most neoplastic diseases. The complex mechanism responsible for the spread of cancer are governed by interactions between tumour cells and the host tissues. Choriocarcinoma cells and cultured blood vessels were used to study the interaction between tumour and endothelial cells. Seeding of tumour cells onto blood vessel wall caused retraction of endothelial cells leading to the exposure of underlying tissue. Subsequently, the tumour cells penetrated the sub-endothelial connective tissue and the internal elastic lamina.

Animals↗

PubMedDate not supplied

Scanning electron microscopic study of invasiveness between normal and neoplastic cells and fibroblasts in monolayer culture.

Normal cells are non-invasive except for a few cell types such as leukocytes and macrophages, while neoplastic cells are active in both migration and invasion. In the present investigation, the confrontations of normal rat hepatocytes, lung macrophages and B16 melanoma cells with monolayers of fibroblasts grown on collagen gel have been studied. When monolayers of fibroblasts were confronted with melanoma cells, there was obvious retraction of the fibroblasts. When hepatocytes or macrophages were seeded onto monolayers of fibroblasts, infiltration always occurred at intercellular contacts and no retraction of fibroblasts was seen. Therefore it would appear that normal and neoplastic cells penetrate into monolayers of fibroblasts by different mechanisms.

Animals↗

PubMedDate not supplied

Ultrastructural study on the invasion of the basal lamina of retinal inner limiting membrane by esophageal carcinoma cells.

Esophageal carcinoma cells EC/CUHK1 were allowed to interact with the basal lamina of the inner limiting membrane of the retina in vitro. Both scanning and transmission electron microscopy revealed that tumour cells first attached to the basal lamina with filopodia and subsequently invaded into the ganglion cell layer of the retina. In addition, transmission electron microscopic studies demonstrated that tumour cells induced mechanical distortion as well as dissolution of the basal lamina.

Animals↗

PubMedDate not supplied

Biological characteristics of a newly established human oesophageal carcinoma cell line.

An epithelial cell line, EC/CUHKI was established from a human squamous cell carcinoma of the oesophagus. The cells were polygonal in shape with numerous microvilli. Transmission electron microscopy (TEM) revealed the presence of desmosomes and tonofilaments. Karyotypic analysis of cells from the cell line demonstrated an aneuploid human type with a modal chromosome number of 85. Epstein-Barr viral nuclear antigen (EBNA) has not been demonstrated in the cells from the primary culture or subcultures. The tumour cells form colonies in agar and have a plating efficiency of 20%. The cells are highly invasive in vitro and are tumorigenic in nude mouse.

Aged↗

PubMedDate not supplied

Ultrastructural studies of interactions of B16 melanoma cells and normal mouse skin fibroblasts in the three-dimensional collagen gels in vitro.

In the in vivo system, cancer metastasis is a complex multi-step process. We have utilized an in vitro three-dimensional system to study the initial stages of tumour cell invasion. In this communication, the sequence of events in interactions between B16 melanoma cells and normal mouse skin fibroblasts are described. It is proposed that tumour cells produce a "retractive factor" which induces the underlying fibroblasts to retract so as to facilitate invasion and metastasis.

Animals↗

PubMedDate not supplied

Biological characteristics of a newly established human cervical carcinoma cell line.

A new cell line, designated CC2/CUHK2, was established from a squamous carcinoma of the uterine cervix from a Chinese patient. The cell line grew well without interruption for over 12 months and over 90 passages. The doubling time of CC2/CUHK2 was 72 hours at passage 57. When seeded at a density of 1.5 x 10(3) cells per 25 cm2 tissues culture flask, the plating efficiency was 2.15%. Chromosome analysis showed a range of 30 to 130 with a modal number of 75. Immunoperoxidase staining of keratin showed positive reaction. Most of the CC2/CUHK2 cells showed weak nuclear staining of HPV capsid antigens with the ABC detection system. Analysis of the DNA samples extracted from the cervical cancer cells showed the presence of HPV type 16 DNA.

Capsid↗

PubMedDate not supplied

An immuno-electron microscopic study on the relationship between nuclear matrix and DNA in rat spermatocytes.

The nucleus of the mammalian spermatid undergoes a series of changes in its chromatin and nucleoprotein composition during transport from testis to epididymis. The sperm DNA is very tightly packaged by protamines instead of histones in somatic cells. However, the nuclear matrix and its association with DNA have not yet been definitively scrutinized with the electron microscope. The present study reveals that the protamine-depleted sperm nuclear matrix appears as a network of thick and thin filaments with glodular structures attached the these fibers. Monoclonal antibody to single- and doublestranded DNA was used to localize remnant DNA after extraction. By immunofluorescence microscopy, monoclonal antibody against DNA was localized outside the nucleus as a halo. Immuno-electron microscopy showed that gold particles were mainly associated with nuclear matrix surrounding the sperm head. Our results suggest a specific structural organization of sperm DNA with its matrix.

Animals↗

PubMedDate not supplied

Ultrastructural study on the development of the rat [correction of mouse] spermatocyte nuclear matrix during epididymal maturation.

The rat sperm nucleus, after sequential extraction with detergents, nuclease and ammonium sulfate, consists of a skeletal structure that resembles the original nuclear shape. This chromatin-depleted skeleton is formed by thick and thin fibers as well as globular structures of different sizes. These fibers form anastomosis. The sperm nuclei obtained from testis and caput epididymis exhibits a loose fibrous network with thin fibers at the center. The entire nucleus of the sperm in the caudal epididymis is formed by a dense network of thick and thin fibers. These highly branched matrix fibers had diameters of 35 and 12 nm. It is concluded that the increase in density of the matrix fibers is related to the condensation of the chromatin in the maturation of the spermatozoa.

Animals↗