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D T Kiang

Publications and source records attributed to D T Kiang.

At least 37 records · Page 2Linked to original sources
PubMed1991

Variations in amplification and expression of the ornithine decarboxylase gene in human breast cancer cells.

The polyamine biosynthetic pathway plays a critical role in the growth of human breast cancer cells. Ornithine decarboxylase (ODC) is a key enzyme in polyamine biosynthesis. To understand the regulation of ODC activity and polyamine accumulation in breast cancer cells, we studied amplification and expression of the ODC gene in four breast cancer cell lines. ODC gene dosage was analyzed by Southern blot hybridization and was 4- to 12-fold higher in T-47D, MDA-MB-231, and BT-20 cell lines than in the MCF-7 cell line. ODC mRNA level was 2- to 3-fold higher in BT-20 and MDA-MB-231 cell lines than in the other two lines. We also measured ODC activity and polyamine concentration in these cell lines, and determined their sensitivity to an ODC inhibitor, difluoromethylornithine (DFMO). BT-20 cells showed significantly higher ODC activity and polyamine concentrations than the other three cell lines. BT-20 cells were resistant to the growth inhibitory effect of DFMO even at 4 mM concentration, whereas the proliferation of MCF-7, T47D, and MDA-MB-231 cells was inhibited by this drug. These results suggest that different transcriptional and post-transcriptional mechanisms control the regulation of ODC gene expression in breast cancer cell lines.

Adenocarcinoma↗
PubMed1990

Tumor marker kinetics in the monitoring of breast cancer.

Controversy exists in using carcinoembryonic antigen (CEA) for monitoring the clinical course of breast cancer. In this study, the kinetics of two plasma tumor markers, CEA and CA15-3, immediately after the initiation of chemotherapy were assessed in 30 patients with advanced breast cancer. Four distinct kinetic patterns were seen. Two patterns fitted the expected relationship where the plasma marker increased during tumor progression (nine patients), and declined in tumor regression (five patients). The third pattern was paradoxical in that objective tumor regression in eight patients was associated with an acute surge of these markers followed by a steady decline. The doubling times for both CEA and CA15-3 were immediately shortened four-fold after therapy suggesting tumor cytolysis in treatment responders. Equally paradoxical was the fourth pattern where tumor progression in eight patients was associated with a rapid and transient decline of markers followed by rebounds. Such a rapid decline may be due to a suppression of marker release, as demonstrated in an in vitro study. Adequate knowledge of these putative paradoxical patterns will permit their effective use in monitoring the disease course and perhaps in the early prediction of the therapeutic response.

Adult↗
PubMed1989

Regulation of ornithine decarboxylase gene expression in MCF-7 breast cancer cells by antiestrogens.

Ornithine decarboxylase (ODC) is an enzyme intimately related to cell growth regulation. The metabolic products of ODC, the polyamines, are known to play a vital role in the structure and function of biological macromolecules including nucleic acids and proteins. The activity of ODC is stimulated by estrogens in their target cells. In order to gain insight into the molecular mechanism of action of antiestrogens in human breast cancer, we studied the effect of tamoxifen and 4-hydroxytamoxifen on the concentration of ODC mRNA, ODC activity, and the polyamine levels in a hormone-responsive breast cancer cell line, MCF-7. ODC mRNA concentration was reduced to 40% of the controls after 6 h of treatment of the cells with 100 nM 4-hydroxytamoxifen, but tamoxifen had no significant effect on ODC mRNA after treating with even 1 microM concentration for 36 h. ODC activity was, however, reduced to 40 and 75% of the controls after 24 h of treatment with 4-hydroxytamoxifen and tamoxifen, respectively. There was a significant reduction in the concentration of putrescine to 63% of control in tamoxifen-treated cells, but spermidine and spermine levels were not affected. With 4-hydroxytamoxifen, putrescine, spermidine, and spermine levels were reduced to 41, 62, and 79% of the control, respectively. In addition, exogenous putrescine was able to reverse the growth inhibitory effects of 4-hydroxytamoxifen. Overall, these results indicate that ODC and polyamine levels in MCF-7 cells are controlled by antiestrogens, and that suppression of polyamine biosynthesis plays a critical role in the growth inhibitory effects of antiestrogens.

Blotting, Northern↗
PubMed1989

Up-regulation of estrogen receptors by nonsteroidal antiestrogens in human breast cancer.

Development of resistance to hormonal therapy in breast cancer is frequently associated with a decline or loss of cellular estrogen receptors. Agents which up-regulate the receptor may reduce the incidence of hormonal resistance. Antiestrogens at concentrations ranging from 0.1 to 1 microM produced a 2- to 4-fold increase of estrogen receptors in MCF-7 and T-47D breast cancer cells. This increase, which occurred as early as 3 h and was sustained throughout the 4 days of continuous exposure to tamoxifen, was primarily due to an enhancement in receptor synthesis.

Breast Neoplasms↗
PubMed1989

Gross cystic disease fluid protein-15 as a marker for breast cancer: immunohistochemical analysis of 690 human neoplasms and comparison with alpha-lactalbumin.

The identification of metastatic carcinoma of the breast may be difficult in the absence of a previous history of breast cancer. Various immunophenotypic markers have been introduced to aid in this process. A monoclonal antibody directed at a 15-kilodalton (kd) gross cystic disease fluid protein (GCDFP-15) was applied immunohistochemically to paraffin sections of 105 breast cancers and 585 nonmammary malignancies in order to assess its value in this context. In addition, GCDFP-15 was compared with another putative mammary epithelial marker, alpha-lactalbumin (ALA), with respect to sensitivity and specificity for a diagnosis of breast carcinoma. Overall, the rates of specificity and sensitivity and the predictive value of a positive result for GCDFP-15 were 95%, 74%, and 74%, respectively. Corresponding statistical parameters for ALA were 50%, 50%, and 23%. A consistent congruency between the reactivity patterns of primary and metastatic breast cancers was noted for GCDFP-15 but not for ALA. Besides mammary carcinomas, the major tumor types that expressed GCDFP-15 were carcinomas of the salivary glands, sweat glands, and prostate. Since the latter three types of lesions are unlikely to be diagnosed as metastatic breast cancer, statistical indices were recalculated after exclusion of these three tumor types. Following this exclusion, the adjusted rate of specificity of GCDFP-15 and the predictive value of a positive result for a diagnosis of metastatic carcinoma of the breast were each 99%. In contrast, predictive parameters for ALA were not altered. These results show that GCDFP-15 is a specific marker for breast cancer and is superior to ALA in this respect.

Adenocarcinoma↗
PubMed1988

Estrogen receptors in bilateral breast cancer.

Estrogen receptor status, tumor histology, and the interval between the development of tumors were assessed in 99 patients with bilateral breast cancer. Tumors were first grouped into those simultaneously detected in both breasts or within 12 months of each other (synchronous bilateral breast cancer, of which there were 64) and second, those detected within more than 12 months of each other (asynchronous bilateral breast cancer, of which there were 35). Nineteen percent of all tumors were lobular carcinomas. Overall, the rate of receptor discordance between the two tumors was not significantly different from that previously reported between biopsies of primary tumor and metastases in patients with unilateral breast cancer. Synchronous receptor-positive tumors occurred significantly more frequently than expected, suggesting that the development of the two tumors was influenced by a common mechanism. In patients with asynchronous bilateral breast cancer there was a significantly longer interval between tumors if both were receptor-positive compared with concordant receptor-negative tumors and tumors with discordant receptor status. There was a significant discordance in the receptor status of asynchronous tumors when the histology also differed, indicating that the tumors in this group were likely to be separate primary tumors.

Breast Neoplasms↗
PubMed1988

A twenty-two-fold increase in the relative affinity of estrogen receptor to poly (dA-dC).poly (dG-dT) in the presence of polyamines.

We studied the relative efficacy of polyamines to facilitate the binding of estrogen receptor to poly(dA-dC).poly(dG-dT). In the absence of polyamines, 1,400 micrograms/ml of this polynucleotide eluted 50% of bound estrogen receptor from DNA-cellulose. In contrast, 50% estrogen receptor was eluted by 65 micrograms/ml of poly(dA-dC).poly(dG-dT) complexed with 150 microM spermidine. Putrescine and spermine also enhanced the ability of poly(dA-dC).poly(dG-dT) to elute estrogen receptor, but the magnitude of the effect was not as high as that of spermidine. Control experiments with calf thymus DNA and poly(dA-dT).poly(dA-dT) showed 6- and 3-fold increase, respectively in their affinity for estrogen receptor in the presence of spermidine. The dramatic increase in the affinity of poly(dA-dC).poly(dG-dT) for estrogen receptor in the presence of polyamines might be a result of the conversion of the polynucleotide to the left-handed Z-DNA form. These results show that polyamines are capable of participating in estrogenic regulation of gene expression by altering the affinity of the receptor for specific DNA sequences.

Animals↗
PubMed1988

Modulation of the binding of progesterone receptor to DNA by polyamines.

Putrescine, spermidine, and spermine are a group of small organic cations, collectively known as polyamines. They are present in all living cells, and their levels are generally increased in tumor cells. Progesterone receptor is a gene-regulatory protein that plays a major role in gestation and in hormonal responsiveness of breast cancer. We studied the effects of putrescine, spermidine, 2 lower homologues of spermidine, N1- and N8-acetyl spermidines, spermine, and N1-acetyl spermine on the sedimentation profile and DNA binding of progesterone receptor from rabbit uterus. Progesterone receptor, prepared in hypotonic buffer, sedimented at the 7S region of sucrose gradients. In the presence of 1 mM putrescine, a part of the receptor was converted to a 5S form. In the presence of 1 mM spermidine or 0.25 mM spermine, the receptor was completely transformed to the 5S form. The DNA binding of the 7S form of progesterone receptor was 7 +/- 3%. After incubating this receptor with 1 mM putrescine, 1 mM spermidine, or 0.25 mM spermine, its DNA binding increased to 16 +/- 4, 37 +/- 3, and 44 +/- 5%, respectively. The structural specificity of polyamines in facilitating the DNA binding of progesterone receptor was examined by using two spermidine homologues. The first homologue with one methylene group less than that of spermidine was as effective as spermidine in transforming progesterone receptor. Removal of two methylene groups, however, had a dramatic effect in reducing the efficacy of the resulting molecule to the level of putrescine. Taken together, our results show that natural polyamines are capable of modulating the binding of progesterone receptor to DNA. Since progesterone receptor is associated with the hormonal responsiveness of human breast cancer, polyamine levels in tumor cells might play an important role in the gene-regulatory function of progesterone receptor.

Acetylation↗
PubMed1987

Additive growth-inhibitory effects of DL-alpha-difluoromethylornithine and antiestrogens on MCF-7 breast cancer cell line.

We studied the growth inhibitory effects of DL-alpha-difluoromethylornithine, and antiestrogens (tamoxifen, 4-hydroxytamoxifen, trioxifene, keoxifene, and LY117018) as single agents and in combinations on the proliferation of a breast cancer cell line, MCF-7. At 0.1 mM difluoromethylornithine, the proliferation of MCF-7 cells was inhibited to 75 +/- 6% of the controls. Treatment of the cells with 0.1 microM 4-hydroxytamoxifen reduced cell growth to 72 +/- 4%. Combination of 0.1 mM difluoromethylornithine and 0.1 microM 4-hydroxytamoxifen reduced cell growth to 38 +/- 5%, indicating additive growth inhibitory effects. Similar additive effects were observed with all 5 antiestrogens in combination with difluoromethylornithine.

Breast Neoplasms↗
PubMed1987

Structural alterations and stabilization of rabbit uterine estrogen receptors by natural polyamines.

Estrogenic regulation of gene expression involves interaction of the hormone with its receptors, which undergo structural and conformational changes to interact with specific DNA sequences. Putrescine, spermidine, and spermine, are ubiquitous cellular components. We studied the effects of these polyamines on rabbit uterine estrogen receptors by sucrose gradient centrifugation and ligand dissociation kinetics. The native 7S receptor converted to a 9S-10S form in the presence of 100 microM spermidine or spermine. Higher concentrations caused precipitation of the receptor. This precipitation was reduced by RNase treatment of the receptor. RNase-treated receptors sedimented at 4S and 7S regions of sucrose gradient. The dissociation rate constant (k) of the 4S receptor is 2.8 X 10(-3) min-1 in the presence of 1 mM spermidine, compared to a control value of 7.7 X 10(-3) min-1. Similar effects were observed with putrescine and spermine. The dissociation of the RNase-treated 7S receptor was biphasic, with about 50% of the receptors dissociating at a faster rate (k1 = 40 X 10(-3) min-1) than the other half (k2 = 7.4 X 10(-3) min-1). Spermidine (1 mM) caused a 2-fold reduction in k2, whereas k1 was not affected. This study shows that polyamines affect the structural organization and ligand dissociation kinetics of estrogen-receptor complexes.

Animals↗
PubMed1987

Breast cancers negative for estrogen receptor but positive for progesterone receptor, a true entity?

By the conventional steroid-binding assay method for receptor, 3% of 1,095 primary breast cancers (or 10.6% of 263 premenopausal tumors) were classified as negative for estrogen receptor (ER), but positive for progesterone receptor (PR). The true ER status in this rare group of tumors was further investigated by the enzyme-immunoassay (EIA) or immunocytochemical (ICA) staining method using monoclonal antibodies H222 and D547. Immunoreactive ER was present in nine ER-/PR+ tumors studied, whereas it was not detectable in nine age-matched ER-/PR- tumors. Immunoreactive ER was also present in 24 ER+ breast cancers studied, and was particularly higher in tumors that were PR+. Measurement of immunoreactive ER by monoclonal antibody method provides certain advantages over the conventional dextran-coated charcoal (DCC) method, especially in ER-/PR+ tumors.

Adult↗
PubMed1986

Peanut lectin binding in breast carcinoma. Lack of correlation with estrogen receptor content.

Previous reports have shown binding of peanut agglutinin (PNA) by immunoperoxidase techniques in normal, benign proliferative, and malignant breast epithelia. Correlation of binding with maturity, secretory activity, hormonal milieu, and tissue hormone receptor content has been described. To investigate the relationship between PNA staining by the avidin-biotin complex technique and estrogen receptor (ER) content, 79 breast tumors of different types and known tissue ER content were studied. Thirty-eight of 50 ER-positive cases were PNA-positive. Twenty of 29 ER-negative cases were PNA-positive. Statistical analysis shows the two factors to be independent (0.5 less than P less than 0.9). The literature on blood group antigens in breast carcinoma and histochemical applications of PNA is reviewed.

Arachis↗
PubMed1986

Ribonuclease-induced transformation of progesterone receptor from rabbit uterus.

The effect of RNase on the transformation of progesterone receptor from rabbit uterus was studied by density-gradient centrifugation and DNA-cellulose binding assay. The 7S form of the receptor in crude cytosol was RNase sensitive, and converted to the 4S form after RNase treatment. This reaction was prevented by an RNase inhibitor and reversed by the addition of ribosomal RNA. RNase treatment also caused a two-fold increase in the DNA binding of cytosolic receptor, and reduced the time required for heat-induced transformation. However, sucrose-gradient-purified progesterone receptor (7S) did not undergo transformation by warming unless exogenous RNase was added, thereby suggesting that a cytosolic factor, which might be endogenous RNase, is necessary for the heat-induced transformation of progesterone receptor. Furthermore, degradation of the receptors which occurred after prolonged warming at 25 degrees C in the presence of RNase could be prevented by the addition of DNA-cellulose to the reaction mixture. These results indicate that RNA is associated with the 7S form of progesterone receptor, and that its hydrolysis by RNase might be involved in the transformation of this receptor.

Animals↗
PubMed1985

A randomized trial of chemotherapy and hormonal therapy in advanced breast cancer.

We randomized 81 postmenopausal women with advanced breast cancer, whose tumors were rich in estrogen receptors or of unknown estrogen-receptor status, to receive either estrogen therapy alone or estrogen therapy combined with chemotherapy. An additional 31 patients, whose tumors were poor in estrogen receptors, were randomized to receive either chemotherapy alone or estrogen combined with chemotherapy. The median duration of follow-up was 87 months. In the receptor-rich group, the survival of the 21 patients receiving combined therapy was significantly longer than that of 19 patients receiving estrogen as initial therapy (followed by chemotherapy after failure or relapse). The median survivals were 72 and 29 months, respectively (P = 0.05 by the generalized Wilcoxon method). Among 41 patients with tumors of unknown receptor status, a survival advantage from combined therapy over chemotherapy was seen in the first two years and then disappeared. The survival in 31 patients with receptor-poor tumors was uniformly short regardless of the therapeutic method. We conclude that combined therapy offers a survival advantage in postmenopausal patients with receptor-rich tumors.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1985

Effect of ribonuclease on the physico-chemical properties of estrogen receptor.

Estrogen receptors (ER) from rat and rabbit uterine cytosol were examined for their sensitivity to ribonuclease (RNase). After RNase treatment, a major part of rabbit uterine ER was converted from the 7S to 3-4S form, and its binding to DNA-cellulose was increased by 40%. Similar treatment on rat uterine ER showed a shift from 7S to 4.5S, and the DNA-cellulose binding was stimulated by 20%. Measurement of endogenous RNase levels showed that lower RNase concentration in rabbit uterine cytosol coincided with larger stimulation of DNA-cellulose binding by exogenous RNase. These results indicate that a major part of 7S ER is susceptible to RNase, and cleavage of bound RNA seems to uncover additional binding sites for DNA. In contrast to the general thinking that 4S to 5S transformation is essential for nuclear binding, we have observed that RNase-treated rat uterine ER did not undergo such a transformation by warming at 25 degrees C, while DNA-cellulose binding of the receptors increased. Thus, temperature activation could occur independent of 4S to 5S transformation.

Animals↗
PubMed1985

Cytoplasmic estrogen and progesterone receptors in canine endometrium during the estrous cycle.

Estradiol and progesterone receptors (ER, PR) were characterized and measured in cytosols from canine endometrium, using saturation and sucrose-gradient centrifugation radioassays. Both receptors were demonstrated to be steroid- and tissue-specific saturable proteins, which bound the respective steroids with high affinity (dissociation constant [Kd] approximately 10(-9)M). Serum estradiol, progesterone, and endometrial cytosol receptor concentrations and receptor-binding affinity were measured for 25 bitches from which samples were obtained at 5 stages of the estrous cycle (5 bitches each): anestrus (A), the 3rd day of proestrus (P3), the 3rd day of estrus (E3), the 12th day after onset of estrus (E12), and the 28th day after onset of estrus (E28). Mean (+/- SEM) serum estradiol concentrations were 17.0 +/- 2.2 (A), 55.4 +/- 5.0 (P3), 89.4 +/- 24.9 (E3), 41.0 +/- 5.9 (E12), and 50.6 +/- 3.9 (E28) pg/ml. Mean (+/- SEM) serum progesterone concentrations were 0.4 +/- 0.1 (A), 1.5 +/- 0.2 (P3), 17.3 +/- 7.5 (E3), 41.6 +/- 9.5 (E12), and 25.8 +/- 3.2 (E28) ng/ml. Concentrations of ER increased significantly from 1.06 pmol/g of uterus during stage A to a peak concentration of 6.18 pmol/g of uterus at E12, followed by a gradual decrease to 0.69 pmol/g of uterus by E28. The PR concentrations increased from 3.01 pmol/g of uterus in stage A to 17.32 pmol/g of uterus at P3; PR concentrations, thereafter, decreased gradually to 1.85 pmol/g of uterus by E28. Dissociation constants were significantly higher at E12 for the ER (Kd = 2.6645 X 10(-9)M) and at P3 for the PR (Kd = 5.8282 X 10(-9)M) than at the other stages examined, indicating a decrease in receptor affinity during the periods of high receptor concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Thymidine kinase as a predictor of response to chemotherapy in advanced breast cancer.

Cytosols from breast cancers were measured for estrogen receptor (ER) and thymidine kinase (TK) activity. There was no correlation between ER and TK in 137 primary breast cancers studied. The results of TK from 57 metastatic breast cancers were correlated with the response or failure to subsequent hormonal therapy or chemotherapy. TK did not predict the responses to hormonal therapy in 12 patients. Of the 45 patients treated with chemotherapies, 13 of 15 tumors with TK over 80 pmol/mg/min responded (86%), while only 4 of the 30 tumors (13%) with TK below 80 pmol/mg/min responded (p less than 0.001). TK appears to be useful in predicting the responses to chemotherapy.

Antineoplastic Combined Chemotherapy Protocols↗