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Biomedical subjects

Y Gong

Publications and source records attributed to Y Gong.

195 records · Page 11Linked to original sources
PubMed1992

Regulation of transforming growth factor gene expression in human endometrial adenocarcinoma cells.

We have examined the effects of medroxyprogesterone acetate (MPA) and 4-hydroxytamoxifen (OH-TAM) on the cell proliferation and the expression of TGF-alpha and TGF-beta genes in Ishikawa cells and HEC-50 human endometrial adenocarcinoma cells. The effects of exogenous TGF-alpha, TGF-beta and anti-EGF receptor monoclonal antibody on cell proliferation were also determined. Antisense oligonucleotides were used to determine the effects of endogenous expression of TGF-alpha and TGF-beta. In both cell lines, MPA resulted in a time and dose-dependent inhibition of cell proliferation whereas OH-TAM had no effect on HEC-50 cell proliferation. The relative abundance of TGF-alpha mRNA was significantly reduced by MPA in Ishikawa cells but not in HEC-50 cells. In Ishikawa cells, a reduction in TGF-alpha mRNA abundance was observed with OH-TAM under conditions where both inhibition and stimulation of cell proliferation were demonstrated. Anti-EGF receptor monoclonal antibody inhibited Ishikawa cell growth but had little effect on HEC-50 cell proliferation. Exogenous TGF-alpha stimulated proliferation of both cell lines whereas exogenous TGF-beta inhibited proliferation of Ishikawa cells but stimulated proliferation of HEC-50 cells. Antisense oligonucleotides to TGF-beta inhibited proliferation of HEC-50 cells. From these data we conclude that the antiproliferative effects of progestins and OH-TAM on endometrial cancer cells appear to be mediated by different mechanisms.

Adenocarcinoma↗
PubMed1992

Phorbol esters differentially regulate the expression of insulin-like growth factor-binding proteins in endometrial carcinoma cells.

We have examined the effects of protein kinase-C (PKC) activation on expression of the six known insulin-like growth factor-binding proteins (IGFBPs) by human endometrial carcinoma cells. Each of six known IGFBPs was expressed in one or more of the three cell lines examined. The addition of 10(-7) M 4 beta-phorbol 12-myristate 13-acetate (PMA) to HEC-50 and HEC-1B cells resulted in changes in cell morphology, growth inhibition, activation of PKC, and an increase in expression of IGFBP-1. PMA had no effect on these parameters in the Ishikawa cell line, which did not express IGFBP-1. In HEC-50 cells, the effect of PMA was blocked by the concomitant addition of the PKC inhibitor staurosporin and the simultaneous addition of cycloheximide. PMA also resulted in an increase in IGFBP-3 in HEC-50 cells and an increase in IGFBP-6 expression in HEC-1B cells. In contrast, IGFBP-3 expression was down-regulated by PMA in HEC-1B and Ishikawa cells. The abundance of IGFBP-2 and IGFBP-5 mRNAs was also reduced in HEC-1B and Ishikawa cells, respectively. IGFBP-4 was expressed only in HEC-50 cells and was not affected by PMA treatment. These data establish a role for the PKC pathway in regulation of expression of IGFBP-1, -2, -3, and -5 in endometrial adenocarcinoma cells and illustrate the complexity of cell type-specific expression of the IGFBPs.

Adenocarcinoma↗
PubMed1992

Effect of 60Co gamma-irradiation on the nonspecific cytotoxicity of alveolar macrophages in vitro.

This paper reports on the effect of radiation on the nonspecific cytotoxicity of rat alveolar macrophages (AM). AM (effector cells) of bacille Calmette-Guerin-activated Wistar rats were irradiated with 60Co gamma rays in vitro to give doses of 0, 100, 300, and 500 Gy. Three hours after irradiation, the AM were cultured with human lung adenocarcinoma AGZY83-a and HeLa target cells in 125I-deoxyuridine-containing media for 6 hr and the cytotoxicity indexes determined. The results indicated that the cytotoxicity indexes of AM against human lung adenocarcinoma cells and HeLa cells were 94.3 +/- 0.3% and 81.3 +/- 1.9%, respectively. The cytotoxicity indexes using an effector/target cell ratio (E/T) of 10 seemed to be greater than with ratios of 20 and 30. The cytotoxicity indexes of AM (7 rats), irradiated to give doses of 0, 100, 300, and 500 Gy, against adenocarcinoma cells at an E/T ratio of 10 were 87.9 +/- 8.4%, 65.4 +/- 14.1%, 47.5 +/- 17.5%, and 36.7 +/- 9.7%, respectively. The significance of the nonspecific cytotoxicity of AM in the immunological elimination of tumors and the inhibitory effect of radiation on AM cytotoxicity are discussed.

Adenocarcinoma↗
PubMed1992

Differential effects of phorbol esters on proliferation and calcyclin expression in human endometrial carcinoma cells.

Calcyclin is a member of the S-100 family of calcium-binding proteins, whose expression is enhanced when quiescent cells are exposed to mitogenic signals. The function of calcyclin is unknown, but it is thought to be involved in modulating the intracellular calcium concentration following mitogenic stimuli. Since activation of protein kinase C (PKC) also occurs following stimulation of quiescent cells by a variety of mitogens, we have investigated the relationship between calcyclin expression and PKC activation in three human endometrial adenocarcinoma cell lines. The addition of 10(-7) M 4 beta-phorbol 12-myristate 13-acetate (PMA) to HEC-50 and HEC-1B cell cultures resulted in a change in cell morphology, an inhibition of proliferation, an increase in calcyclin transcription rate, and an increase in calcyclin mRNA and calcyclin protein levels. In contrast, PMA had no effect on cell morphology or cell proliferation in the Ishikawa adenocarcinoma cell line but enhanced calcyclin expression. Another bioactive phorbol ester had the same effect, whereas the calcium ionophore A23187 and the non-phorbol-ester-type tumor promoter thapsigargin had no effect on calcyclin expression. The effect of PMA on calcyclin expression was blocked by the simultaneous addition of the PKC inhibitor staurosporine and by protein synthesis inhibition with cycloheximide. RNase protection assays and primer extension analysis demonstrated that PMA enhanced transcription from all three of the previously identified transcription start sites in the calcyclin gene. These data clearly demonstrate a dissociation between calcyclin expression and cellular proliferation and suggest that the enhanced calcyclin expression which is seen in quiescent cells following mitogenic stimuli may result from activation of the PKC system.

Adenocarcinoma↗
PubMed1991

Transforming growth factor gene expression in human endometrial adenocarcinoma cells: regulation by progestins.

In an attempt to understand the antiproliferative effects of progestins in endometrial cancer, we have examined the effects of the potent progestin, medroxyprogesterone acetate (MPA), on the cell proliferation and the expression of transforming growth factor (TGF) alpha and beta genes in human endometrial adenocarcinoma cell lines. The two cell lines used were Ishikawa, var 1, and HEC-50. In addition, the effects of exogenous TGF-alpha and anti-epidermal growth factor (EGF) receptor monoclonal antibody on cell proliferation were determined. Incubation of both cell lines with MPA resulted in a time- and dose-dependent inhibition of cell proliferation. Half-maximal growth inhibition was observed at 0.6 nM. In Ishikawa cells, the relative abundance of TGF-alpha was significantly reduced by MPA. A significant decrease in TGF-alpha mRNA was apparent 6 h after exposure to MPA and a further decrease was seen 12-24 h after addition of the progestin. The concentration of TGF-alpha immunoreactivity in conditioned medium of MPA-treated cells was also significantly reduced compared to control cultures. MPA had no effect on TGF-alpha expression by HEC-50 cells. EGF mRNA was not detected by Northern blot analysis in either cell type. MPA had no significant effect on EGF receptor mRNA abundance but resulted in a small increase in EGF receptor number in Ishikawa cells. Anti-EGF receptor monoclonal antibody (0.6-6 nM) inhibited Ishikawa cell growth but had no effect on HEC-50 cell proliferation. Exogenous TGF-alpha stimulated proliferation of both cell lines, but Ishikawa cells were significantly more sensitive to exogenous TGF-alpha than HEC-50 cells. Furthermore, TGF-alpha could reverse the growth inhibitory effects of MPA on Ishikawa cells. A decrease in TGF-beta mRNA abundance was also observed in MPA-treated Ishikawa and HEC-50 cells. This effect was of small magnitude, variable, and only observed after prolonged exposure to MPA. These observations are consistent with the hypothesis that the antiproliferative effects of progestins on Ishikawa cells are mediated by decreased expression and autocrine action of TGF-alpha. Since similar growth inhibition is also seen in the HEC-50 cells in which progestins have no effect on TGF-alpha expression, additional mechanisms are likely to be involved in the antiproliferative effects of progestins in human endometrial cancer.

Antineoplastic Agents↗
PubMed1991

[Overexpression of an extracellular Bacteroides nodosus protease in E. coli and isolation and characterization of its promoter].

Bacteroides nodosus is the essential causative agent of ovine footrot. It produces extracellular proteases which involved in pathogenesis of footrot. In this paper, we report the subcloning of Bacteroides nodosus protease, its overexpression in E. coli and its N-terminal polypeptide sequence. The subclone library was constructed in E. coli using SphI digested original clone (15 kb) and plasmid PTZ18R and screened using immunological assay. The expression was observed using SDS-PAGE. The subcloned DNA fragment was then cut with Sau3AI, cloned into pKK232-8 vector to perform promoter isolation and analysis. The promoter strength was determined using spectrophotometric assay.

Bacteroides↗
PubMed1991

[Trace elements in the aqueous extract of twenty Chinese drugs before and after charring].

Our study on the variation of trace element contents in the aqueous extract of 20 Chinese drugs before and after charring has shown that after charring Ca ions increase noticeably in the extract of 6 drugs, increase slightly in another 6 and decrease in varying degrees in the remaining 8. In all the charred drugs no rise has been observed in the contents of trace elements, but instead, in most of them the contents tend to drop.

Calcium↗
PubMed1990

Epidermal growth factor: receptor and ligand expression in human breast cancer.

The epidermal growth factor (EGF) gene is expressed by most human breast cancer cell lines as well as 83% of human breast cancers in vivo. Furthermore, EGF mRNA is detectable in normal human breast tissue. These data suggest that EGF may have a functional role in both normal and neoplastic human breast tissue. Expression of EGF was generally highest in steroid receptor positive human breast tumor biopsies and cell lines. EGF expression was increased by progestins in T-47D and ZR 75 human breast cancer cells. Furthermore, progestins specifically increased the level of TGF-alpha and EGF-receptor mRNA in T-47D cells. Under these same conditions progestins inhibit growth of the cells. Regulation of expression of EGF, TGF-alpha and the EGF-receptor is unlikely to be directly related to the mechanism of progestin induced growth inhibition in T47-D cells. T-47D-5 cells are more sensitive than T-47D cells to progestin and antiestrogen induced growth inhibition. T-47D-5 cells do not express EGF and contain very low levels of TGF-alpha mRNA. The higher level of EGF and TGF-alpha expression in T-47D cells may be one mechanism by which these cells decrease their sensitivity to growth inhibition by progestins and antiestrogens.

Breast Neoplasms↗
PubMed1990

[An identification method for mineral drugs].

This paper is a report on a method for chemical identification of 58 mineral drugs. Combined with the Chinese traditional identification, the method can differentiate the sham and genuine drugs in a few minutes.

Drug Contamination↗
PubMed1987

The expression of integrated plasmid DNA depends on copy number.

The effect of copy number, integration site, and enhancers on the expression of stably integrated exogenous DNA was examined in Chinese hamster cells. Three similar plasmids were constructed with the mouse beta maj-globin promoter fused to the galK gene either with no enhancer or with the SV40 or Harvey sarcoma virus (HaSV) enhancer. Eighteen stable cell lines were obtained and characterized with respect to plasmid copy number and galactokinase activity. At copy numbers of four or less, the enhancers showed detectable activity and a DNase I hypersensitive site was present. Above four copies, gene activity decreased as the copy number increased, the enhancer sequences were apparently inactive, and the DNase I hypersensitive site disappeared. These data suggest that, at least in this model system, when exogenous DNA is integrated as multiple head-to-tail copies, the entire multigene unit expresses poorly and inappropriately. When the same exogenous DNA integrates as a single (or low number) copy, expression appears to be relatively normal as judged by enhancer stimulation and DNase I hypersensitivity.

Animals↗