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Biomedical subjects

C L Meng

Publications and source records attributed to C L Meng.

At least 37 records · Page 2Linked to original sources
PubMed1994

Flow cytometric DNA analysis of colorectal carcinoid.

We analyzed the patterns of DNA ploidy in 31 colorectal carcinoid tumors from paraffin-embedded tissues by DNA flow cytometry and the relationship of the patterns of DNA ploidy to prognosis. Diploid DNA was found in 78% (24 of 31) of carcinoids and tetraploid in 6% (2 of 31). Five (16%) carcinoids were DNA aneuploid, and four of the patients with aneuploidy showing a near-hypertriploid pattern died during the first 5 years of follow-up. The association of aneuploidy with stage, size, and invasion of tumor was significant. However, our data indicated that DNA aneuploidy of a near-hypertriploid pattern was the most precise and reliable parameter for predicting the prognosis of colorectal carcinoid tumors.

Adult↗
PubMed1994

Regulation of PG synthase by EGF and PDGF in human oral, breast, stomach, and fibrosarcoma cancer cell lines.

Prostaglandins may inhibit or promote tumor cell replication, depending on the cell system that is investigated. In our laboratory, we have established and characterized four different specific human cancer cell lines. The objectives of this study were to examine and compare the prostaglandin endoperoxide synthase (PG synthase, EC 1.14.99.1) activity of these cell lines by measuring the conversion of arachidonate to 3H-PGE2 and 3H-PGF2 alpha. We found that the oral epidermal carcinoma cell line (OEC-M1) had a moderate degree of PG synthase activity. Enzyme activity could be partially blocked (statistically significant) by the addition of epidermal growth factor (EGF) at 20 ng/mL and almost completely inhibited by platelet-derived growth factor at (PDGF) 20 mU/mL. By contrast, we discovered that the human breast adenocarcinoma cell line (BC-M1) did not contain significant PG synthase, and enzyme activity could be significantly activated by the addition of epidermal growth factor at 20 ng/mL and platelet-derived growth factor at 20 mU/mL. We also found that the human stomach adenocarcinoma cell line (SCM-1) had a significant amount of PG synthase activity, and these PG synthase activities were not activated or inhibited by EGF at 20 ng/mL or PDGF at 20 mU/mL. Furthermore, the human fibrosarcoma (FS-M1) cell line also contained a moderate degree of PG synthase activity, which could be significantly inhibited by PDGF at 20 mU/mL but was not inhibited by EGF at 20 ng/mL. The results suggest that EGF and PDGF may be involved in the regulation of the PG synthase activities of human oral, breast, stomach, and fibrosarcoma cancer cells.

Adenocarcinoma↗
PubMed1993

Human papillomavirus 16 DNA in NIH3T3 cells transformed by colonic cancer cellular DNA.

Human papillomavirus (HPV) 16 DNA is closely associated with human cancers. It has been identified as an aetiological agent in cervical cancers and, recently, in colonic neoplasms. To further understand the role of HPV 16 DNA in colorectal carcinogenesis, NIH3T3 cells were transformed with high molecular weight DNA from colonic cancer cells and the expression of HPV 16 DNA detected. Both human Alu and HPV 16 DNA sequences were found in the type II foci of CC-M2T cells by Southern blot hybridisation. Additionally, 100% tumorigenicity in nude mice was seen. This study shows the transfection of HPV DNA from colonic cancers into NIH3T3 mouse cells and suggests that HPV type 16 might be associated with the malignant transformation of colonic cells.

3T3 Cells↗
PubMed1993

Stimulation of PGE2 synthesis in a co-culture of periosteal fibroblasts and osteoblast-like cells by parathyroid hormone.

In previous experiments, we demonstrated that hPTH 1-34 activates PGE2 synthesis and calcium mobilization by chick calvaria. In this report, we started to search for the PTH responsible cell population in this bone tissue. When the chick calvariae were subjected to sequential enzyme digestion, we found that the third cell population were the cells that reacted to human PTH 1-34 and bovine PTH 1-34. A subsequent procedure was performed using the cells isolated from enzyme digestion and separated into two distinct populations--periosteal fibroblasts (PF) and osteoblast-like cells (OB)--by a two-step density gradient of Percoll. We found that PF and OB cells alone did not respond to PTH in terms of PGE2 synthesis. However, when these two cell populations were mixed in the proportion of 50:50, the synthesis of PGE2 and PGF2 alpha was increased significantly by the treatment of PTH and calcitonin. No effects were demonstrated in the mixing proportions of 30:70 and 70:30. These results suggest that PTH responsiveness may need a local interaction between periosteal fibroblasts and osteoblast-like cells residing in chick calvaria.

Animals↗
PubMed1992

Kinetic mechanism of the cytosolic malic enzyme from human breast cancer cell line.

The kinetic mechanism of the cytosolic NADP(+)-dependent malic enzyme from cultured human breast cancer cell line was studied by steady-state kinetics. In the direction of oxidative decarboxylation, the initial-velocity and product-inhibition studies indicate that the enzyme reaction follows a sequential ordered Bi-Ter kinetic mechanism with NADP+ as the leading substrate followed by L-malate. The products are released in the order of CO2, pyruvate, and NADPH. The enzyme is unstable at high salt concentration and elevated temperature. However, it is stable for at least 20 min under the assay conditions. Tartronate (2-hydroxymalonate) was found to be a noncompetitive inhibitor for the enzyme with respect to L-malate. The kinetic mechanism of the cytosolic tumor malic enzyme is similar to that for the pigeon liver cytosolic malic enzyme but different from those for the mitochondrial enzyme from various sources.

Animals↗
PubMed1992

A study of bond strength between light- and self-cured orthodontic resin.

Light-cured orthodontic composite resin has been widely advertised recently for use in bonding. However, the curability of light-cured resin when light waves are diffused through metal, ceramic, or resin brackets is doubtful and questionable. This study evaluated the effectiveness of a visible light source in curing the resin under a solid metal bracket, compared the tensile bond strength at different exposures, and analyzed the broken interface distribution between light-cured resin with various light exposure times and self-cured resin. The bond strength results revealed that the difference between light-cured resin (Transbond) with 60, 40, and 20 seconds of light exposure, respectively, and self-cured resin (Concise) was 1.05, 0.92, 0.61, and 0.71 kg/mm2, respectively. The bond strength of Transbond with 60 and 40 seconds of light exposure was greater than both the bond strength of Transbond with 20 seconds of light exposure and the strength of the self-cured resin of Concise, with statistical significance (p less than 0.01). There were also no statistical differences between Transbond with 60 and 40 seconds of light exposure or Transbond with 20 seconds of light exposure and Concise. The bond failure interfaces were located between the bracket and the resin, within the resin itself, or between the resin and the enamel. Tooth fragmentation was rarely found. There were no statistical differences (p greater than 0.05) among broken interfaces. This indicates that visible light is powerful in curing the visible light-activated composite resin under solid metal brackets.(ABSTRACT TRUNCATED AT 250 WORDS)

Acrylic Resins↗
PubMed1992

Epithelial neoplasm of the colorectum: correlation of histopathological features with cytogenetic studies.

Seven cases of primary rectosigmoid epithelial neoplasm, including a tubular adenoma, a villous adenoma with malignant change and five adenocarcinomas, were cytogenetically studied with short-term cultivation and GTG-banding. The tubular adenoma showed karyotypic normality. The other six malignant tumors were hyperdiploid in chromosomal modal number and showed multiple aberrations. The complexity of chromosomal aberrations increased proportionally to the pathologic stage. No common chromosome change to all of the tumors was found. The most common recurrent chromosome changes were extra gains of chromosomes #7 and #8q, which were found respectively in four of the six malignant tumors. Two recurrent structurally abnormal chromosomes were i(8q) and der(10)t(10;?)(p15;?). No case showed sex chromosome change, except one tumor from a male patient who obtained an extra X chromosome. All these chromosome changes found were consistent with the results reported by other investigators. Deletions of #5q and #17 were nevertheless only found in one and two of our six malignant cases, respectively. No cases showed a deletion of #18q. The possible molecular mechanisms of these recurrent chromosome aberrations were also discussed.

Adenocarcinoma↗
PubMed1992

Identification of endogenous 5S,12S-dihydroxy-6,8,10,14-(E,Z,E,Z)-eicosatetraenoic acid (5S,12S-diHETE) in chick osteoblasts and epiphyseal cartilage.

Cell homogenates were obtained from chick osteoblast-like cells and epiphyseal growth plates. The lipid fraction was extracted with ethyl acetate and separated by RP-phase HPLC. Reverse-phase HPLC analysis of this fraction showed a major peak displayed a conjugated tetraene structure and this endogenous synthetic compound could be partially blocked by heat treatment at 100 degrees C for 5 min. After methylation, this peak was further purified by SP-HPLC and a major peak was identified by an U.V. absorption at lambda max of 271 nm and shoulders at 261 and 281 nm. The compound was hypothetically proposed by gas chromatography and mass spectrometry (GC/MS) as the cyclohexadiene derivative of 5S,12S-dihydroxy-6,8,10,14-(E,Z,E,Z)-eicosatetraenoic acid (5S,12S-diHETE) with a ring closure at C6 and C11. These results demonstrated that the 5S,12S-diHETE is an endogenous eicosanoid in both intramembranous and endochondral skeletal tissues.

Animals↗
PubMed1992

[An animal model for colon cancer metastases to the lung and establishment of metastatic cancer cell line].

Death, in most colon cancer patients, is not caused by their primary tumors. Instead, metastasis is the major cause of morbidity and death. There are few appropriate animal models to investigate the complexity of the metastatic process. Therefore, the pathogenesis of the metastasis process is not clearly understood. We injected SW480 cells into the cecal wall of athymic nude mice to develop an animal model for colon cancer metastasis and to produce a metastasizing tumor. After metastatic foci formed in the murine lung, we established a metastatic cancer cell line, named CC-ML1, by in vitro primary culture. The characteristics of CC-ML1 were (1) a shorter doubling time; (2) a slightly higher metastatic rate and number of colonies; and (3) less morphological variation than those of SW480. Our research suggests that a higher metastatic potential may be found in CC-ML1 than in SW480 after the advanced cycles of the metastatic process. Thus, the primary animal model in this study may be useful in future studies of cells with a high metastatic potential in the pathogenesis of colon cancer metastases.

Animals↗
PubMed1991

Purification and characterization of the cytosolic NADP(+)-dependent malic enzyme from human breast cancer cell line.

Cytosolic NADP(+)-dependent malic enzyme from a cultured human breast cancer cell line was purified to near homogeneity by two highly efficient chromatography systems: Pharmacia-LKB Q-Sepharose anion-exchange chromatography and adenosine-2',5'-bisphosphate-agarose affinity chromatography. The overall yield was 27%. The enzyme is presumably a tetramer composed of four probably identical subunits of Mr 65,000, which is similar to the enzyme from other sources. The pI and optimum reaction pH values for the tumor malic enzyme are 5.5 and 7.2, respectively. At pH 6.9, most of the enzyme exists as monomers. Activation energy for the enzyme-catalyzed oxidative-decarboxylation reaction is 57.4 kJ/mol. The enzyme is strictly NADP+ dependent, as NAD+ cannot support the oxidative-decarboxylation reaction. ATP at low concentration inhibits the enzyme activity. Fumarate at concentrations up to 5 mM does not affect the enzymatic reaction rate. Therefore the tumor cytosolic malic enzyme, unlike the mitochondrial malic enzyme, is not an allosteric regulatory enzyme.

Breast Neoplasms↗
PubMed1991

An animal model for colon cancer metastatic cell line with enhanced metastasizing ability. Establishment and characterization.

We have developed an animal model for colon cancer metastasis and produced a metastasizing tumor after using a microinjection technique to inject SW480 cells into the cecal wall of athymic nude mice during "minilaparotomy." After the metastatic foci formed in murine lung, an in vitro primary culture was performed and a new metastatic cancer cell line, which was designated as CC-ML3, was established. The studies included: 1) the comparison between SW 480 and CC-ML3 in morphology, growth kinetics, seeding and plating efficiency, and karyotype; and 2) carcino-embryonic antigen determination, origination, and metastatic ability of CC-ML3. The results showed that CC-ML3 was significantly different from SW480 in vitro and possessed a high metastatic potential in vivo. This newly developed animal model may thus be useful for studying the biology and pathogenesis of metastasis of human colonic cancer.

Animals↗
PubMed1991

Human papillomavirus type-related DNA and c-myc oncogene alterations in colon cancer cell lines.

Although squamous-cell epithelium is the most frequent target site of human papillomavirus (HPV) infection, a similar infection is demonstrated in columnar epithelial cells in this paper. The papillomavirus expression in three cell lines was detected in colorectal adenocarcinoma of Chinese patients. The HPV-16 and HPV-18 DNA sequences were found in colorectal cancer cell lines, which might suggest the correlation of HPV to the etiology of colorectal cancers. In addition, c-myc oncogene was identified by amplification in all three colorectal cancer cell lines, but only normal germ-line fragments were found in control tissue. The correlation between HPV and c-myc, and the implications of these findings in colorectal cancers are also discussed.

Adenocarcinoma↗
PubMed1991

Cytogenetic studies of gastric adenocarcinoma.

Cytogenetic analyses were performed on a short-term culture of a primary tumor and an established cell line of gastric adenocarcinoma (SC-M1). The former case was near-diploid, and the latter was near-triploid. No common numerical and structural change or breakpoint was found in these cells. Review of the 13 cases of gastric carcinomas so far reported showed that only trisomies 8 and 9 were consistent findings. The Y chromosome, although lost in all the near-triploid cases, was preserved in all of the near-diploid cases. No consistent structural abnormality and breakpoint were identified in this and other studies.

Adenocarcinoma↗
PubMed1991

[Primary culture of human gingival tissue cells in vitro].

In order to establish and understand the in vitro human gingival cell culture system, this study presents newly developed and characterized primary culture cell types derived from human gingival tissues. Cell cultures were established from human gingival tissues by means of the explant technique and monolayer culture. Cells were studied under stable growth conditions and were characterized in terms of their morphology, Giemsa staining, anti-epithelial cytoskeletal staining, and proliferative parameters. At confluence, disoriented fibroblast cells formed the multilayered culture. The epithelial nature of the epithelioid cells was confirmed by staining for cytoplasmic keratin which is an exclusive epithelial cell protein. The growth curve and cell doubling time of the fibroblasts were evaluated. The results indicate that both epithelial cells and fibroblasts can be cultured from human gingival tissue. This technique provides us with a stable source of normal cells for further in-depth in vitro studies.

Cell Division↗
PubMed1991

[Production and characterization of monoclonal antibody against colon cancer associated antigen in Chinese].

Although many monoclonal antibodies have been made in human colon cancer, none of them are from the Chinese species. Recently, a colon cancer cell line CC-M2 established from a Chinese patient has been completely characterized and used as immunogen to produce monoclonal antibodies. Monoclonal antibodies were produced by standard hybridoma technique. The fusion rate was 95.8%. An isotype IgG1 of high proliferation named as Sam-2 was used in this study. The titers were measured around 10(4). Further studies on MoAb Sam-2 through indirect immunofluorescent and immunoperoxidase tests revealed its good specificity and sensitivity in colorectal cancer tissue. In CEA study, the result indicated that Sam-2 may react on a non-CEA related antigen. For further clinical application, the antigen was identified as a glycoprotein by chemical resistant test. In preliminary studies using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting techniques, Sam-2 could recognize two closed antigens or a dimer antigen with molecular weight 25.2 and 27 Kd respectively.

Animals↗
PubMed1990

Characterization of four newly established human colorectal adenocarcinoma cell lines from Chinese patients.

Four colon adenocarcinoma cell lines, CC-M2, CC-M3, CC-M4, and CC-M2NM, have been established from surgical specimens of 18 unselected patients without the use of "feeder" cells and additional growth factors (e.g., insulin, hydrocortisone, etc.) in the culture medium. The methods of primary cultivation of tissue explants are described. Studies of determination of morphology, growth curve, plating efficiency, chromosomal analysis, CEA and beta-HCG synthesis, and tumorigenicity, were done to characterize the cell lines. Significant variations have been found in one of the four cell lines, both in vitro and in vivo studies. There are distinct phenotypes in the established cell lines which may be useful in studying the cell differentiation and progression of colorectal cancer.

Adenocarcinoma↗