186 research outputs found
Isolation and characterization of androgen receptors from male target cells
Androgens exert their action after binding to cytoplasmic
receptors resulting in the formation of androgenreceptor
complexes. This initial event is followed by activation,
translocation to the nucleus and interaction with
chromatin acceptor sites of the androgen-receptor comulexes.
Bound to chromatin, the androgen-receptor complex stimulates
many biochemical events resulting in gene expression and
starting with RNA-synthesis. Further detailed understanding
of the complex processes requires a purified receptor preparation.
Due to the low amount of receptors present ln androgen
target organs, large scale isolation of these receptors
requires a suitable source. Thusfar it seems that androgen
receptors from different sources have similar characteristics.
In this respect seminal vesicles of the ram contain
an androgen receptor comparable to the receptor present in
rat prostate (chapter 4.3 and appendix paper II). Studies
were performed to purify the receptor present ln ram seminal
vesicles, and an almost two thousand fold purified receptor
preparation has been obtained (chapter 4.4 and appendix
paper III). Nuclear localization and acceptor sites of
androgen-receptor complexes on the chromatin in target cells
have hardly been studied. To gain more insight in the mechanism
of interaction of androgen-receptor complexes with
chromatin acceptor sites, the usefulness of purified androgen
receptors was investigated. In preliminary studies high
affinity interaction of androgen-receptor complexes with
isolated chromatin was observed (chapter 5) and the possibilities
for further investigation are discussed (chapters 6.3
and 6.4)
The clinical significance of epidermal growth factor receptor (egf-r) in human breast cancer: A review on 5232 patients
Epidermal growth factor (EGF) is a 53-aminoacid polypeptide (mol wt 6.045 K) that can influence proliferation and differentiation of a wide variety of cells (1–6). EGF as well as transforming growth factor-α (TGF-α), both of which can activate EGF receptor (EGF-R), are probably produced locally in many tissues as local growth factors rather than as systemic hormones. There is evidence that EGF plays a role in carcinogenesis and that the EGF-stimulated growth regulatory system (apart from that of benign cells) is also involved in proliferation of malignant cells (3). Cellular events are induced by EGF via its cell membrane receptor (EGF-R). The EGF-R is a 170 K glycoprotein that can be divided into an extracellular domain binding EGF or TGF-α, a short transmembrane domain, and an intracellular domain carrying tyrosine kinase activity (7). This intracellular domain shows close sequence homology with the c-erbB-2 and with neu (8), the rat homolog of c-erbB-2 oncogene. Increased expression of the EGF-R gene has been found in a variety of tumors, generally indicating a more aggressive behavior of cancers compared to those with low or normal expression (9–10) although this association is not invariant (11). EGF-R has been identified by several methods including radioligand binding assays, autoradiography, immunocytohistochemistry, immunoenzymatic assays, and measurement of EGF-R transcripts
Vitamin D: A modulator of cell proliferation and differentiation
Abstract
1,25-Dihydroxyvitamin D3, [1,25(OH)2D3], the biologically most active metabolite of vitamin D3, is involved in the regulation of calcium homeostasis and bone metabolism. Recently, receptors for 1,25(OH)2D3 have also been shown in cells and tissues not directly related to calcium homeostasis. Experimental data obtained with leukemic and cancer cell lines, both in vitro and in vivo, showed the effects of 1,25(OH)2D3 on cell differentiation and proliferation. However, high doses of the sterol have to be used to observe these effects. Additional studies are needed to establish whether 1,25(OH)2D3 or suitable analogues have a therapeutic potential in malignant diseases without unacceptable toxicity like the development of hypercalcemia
Thymidine kinase and thymidylate synthase in advanced breast cancer: response to tamoxifen and chemotherapy
Thymidylate synthase (TS) is a crucial target for 5-fluorouracil (5-FU) in
the de novo pathway of pyrimidine synthesis, which is necessary for DNA
synthesis. Thymidine kinase (TK) plays a key role in the complementary or
alternative salvage pathway of pyrimidine synthesis in acute or
pathological tissue stress. In the present study, the activity levels of
TS and TK were determined in 257 primary breast tumors of patients who
received tamoxifen as first-line systemic therapy after diagnosis of
advanced disease. In 155 (60%) responding patients, the median response
duration was 23 months for tumors with low TK activity, 15 months for
tumors with intermediate TK activity, and 13 months for tumors with high
TK activity (P = 0.003). In Cox multivariate analysis corrected for
classical predictive factors including estrogen receptor and progesterone
receptor, patients with intermediate and high levels of TK activity in
their tumors showed a rapid disease progression (P = 0.0002) and an early
death (P = 0.002) after start of tamoxifen treatment. Tumor TS activity
levels were not significantly associated with the efficacy of tamoxifen
treatment. In 121 patients who became resistant to tamoxifen or additional
endocrine treatments and who received 5-FU-containing polychemotherapy,
tumor TK activity was not significantly related to the efficacy of
chemotherapy. Of the 13 patients with low tumor TS activity, only 1 (8%)
responded favorably, whereas 46% (43 of 93) of those with intermediate and
73% (11 of 15) of those with high TS activity responded (P = 0.001). In
Cox multivariate regression analysis in which TS was the only significant
variable, intermediate and high TS activities were associated with a slow
disease progression (P = 0.005) and prolonged survival (P = 0.016) on
chemotherapy. In conclusion, for patients with recurrent breast cancer,
high tumor TK activity is a significant marker of poor clinical outcome on
tamoxifen therapy. Elevated tumor TS activity predicts a favorable outcome
for 5-FU-containing polychemotherapy when applied after tumor progression
on endocrine therapy
The prognostic value of polymorphonuclear leukocyte elastase in patients with primary breast cancer
A variety of serine proteases, including urokinase-type plasminogen
activator (uPA), plasmin,and polymorphonuclear leukocyte elastase (PMN-E),
have been implicated in the processes of tumor cell invasion and
metastasis. Besides degrading of matrix proteins, PMN-E has been shown to
be able to cleave and inactivate plasminogen activator inhibitor-1
(PAI-1), the main inhibitor of uPA, and alpha2-antiplasmin, the natural
inhibitor of plasmin, thus enabling an uncontrolled matrix degradation by
the fibrinolytic enzymes. Because only limited data are available on a
relationship between the tumor level of PMN-E and prognosis in primary
breast cancer patients, in the present study we have measured with an
ELISA the levels of PMN-E (in complex with alpha1-proteinase inhibitor) in
cytosolic extracts of 1143 primary breast tumors. Levels of complexed
PMN-E have been correlated with the lengths of metastasis-free survival
(MFS), relapse-free survival, and overall survival, and a comparison was
made with data previously obtained for uPA and PAI-1. Our results show
that patients with a high PMN-E level in their primary tumor had a rapid
relapse and an early death compared with patients with a low tumor level
of PMN-E. This held true for node-negative and node-positive subgroups of
patients as well. The relationship of PMN-E with a poor prognosis was
especially obvious during short-term follow-up (0-60 months). In Cox
multivariate regression analysis, corrected for the traditional prognostic
factors, PMN-E was an independent prognostic factor, and high levels of
PMN-E were associated with a poor MFS [hazard ratio (HR), 1.63; 95%
confidence interval (CI), 1.23-2.16; P < 0.001], relapse-free survival
(HR, 1.45; 95% CI, 1.10-1.89; P = 0.01), and overall survival (HR, 1.64;
95% CI, 1.20-2.23; P = 0.003). Furthermore, in all three multivariate
models, PMN-E still added significantly to the model after the additional
inclusion of the uPA. PMN-E was an independent prognostic factor for MFS
even in the multivariate analysis including the traditional clinical
prognostic factors and the strong established biochemical prognostic
factors uPA and PAI-1. Our present study suggests that PMN-E is associated
with breast cancer metastasis, and knowledge of the tumor PMN-E status
might be helpful in selecting the appropriate individualized (adjuvant)
treatment for patients with breast cancer
Pleiotropic actions of suramin on the proliferation of human breast-cancer cells in vitro
Suramin, a non‐specific growth factor antagonist, is currently under investigation for treatment of cancer patients. We studied its action on 6 different human breast‐cancer cell lines in vitro. In complete growth medium, pleiotropic effects were observed with respect to cell proliferation, i.e. suramin is stimulatory at low concentrations and inhibitory at higher concentrations, for 4 of the 6 cell lines studied. The various cell lines showed marked differences with respect to the antiproliferative action of suramin, the Evsa‐T cells being by far the most sensitive ones. A suramin concentration of 100 μg/ml brought about a 100% stimulation of the proliferation of ZR/HERc cells, ZR 75.1 cells ectopically expressing a human epidermal growth factor receptor (EGF‐R) cDNA. Although less pronounced (10 to 60% stimulation), a similar response was observed for the parent ZR 75.1 cells, as well as for T‐47D and MDA‐MB‐231 cells. The non‐specificity of the action of suramin was established by the observation that suramin‐induced inhibition of cell proliferation could be abolished by insulin‐like growth factor‐1 (IGF‐I) or basic fibroblast growth factor (bFGF), and even by estradiol, both in complete growth medium and under defined serum‐free conditions. Our data indicate that suramin exerts pleiotropic effects on the proliferation of human breast cancer cells in vitro, and confirm the non‐specific nature of its action. The stimulatory effect of low concentrations of suramin on the proliferation of breast cancer cells may have important consequences for breast cancer patients treated with suramin. Copyrigh
The effects of a plant proteinase inhibitor from Enterolobium contortisiliquum on human tumor cell lines
Supplementary to the efficient inhibition of trypsin, chymotrypsin, plasma kallikrein, and plasmin already described by the EcTI inhibitor from Enterolobium contortisiliquum, it also blocks human neutrophil elastase (K(iapp)=4.3 nM) and prevents phorbol ester (PMA)-stimulated activation of matrix metalloproteinase (MMP)-2 probably via interference with membrane-type 1 (MT1)-MMP. Moreover, plasminogen-induced activation of proMMP-9 and processing of active MMP-2 was also inhibited. Furthermore, the effect of EcTI on the human cancer cell lines HCT116 and HT29 (colorectal), SkBr-3 and MCF-7 (breast), K562 and THP-1 (leukemia), as well as on human primary fibroblasts and human mesenchymal stem cells (hMSCs) was studied. EcTI inhibited in a concentration range of 1.0-2.5 mu M rather specifically tumor cell viability without targeting primary fibroblasts and hMSCs. Taken together, our data indicate that the polyspecific proteinase inhibitor EcTI prevents proMMP activation and is cytotoxic against tumor cells without affecting normal tissue remodeling fibroblasts or regenerative hMSCs being an important tool in the studies of tumor cell development and dissemination
Treatment of breast cancer with different antiprogestins: Preclinical and clinical studies
Abstract
Treatment with antiprogestins in a new treatment modality for breast cancer. Previously, in rats with DMBA-induced mammary tumors we observed significant growth inhibitory effects of chronic treatment with the antiprogestin mifepristone (RU486). In addition, in 11 postmenopausal breast cancer patients, we observed one objective response, six instances of short-term stable disease, and four instances of progressive disease. Side-effects appeared mainly due to antiglucocorticoid properties of the drug. Increased plasma estradiol levels were observed which probably resulted from ovarian (rat) and adrenal (patients) steroidogenesis.
Combined treatment with an antiestrogen in the rat model caused additive growth inhibitory effects. Tumor inhibition after single treatment with mifepristone or tamoxifen was 90 and 75%, respectively. In contrast, when combined, tumor remission similar to that caused by LHRH-agonist treatment (50%) was observed. Even higher tumor remission was found after combined treatment with mifepristone plus LHRH-agonist (75%). In first studies in the rat model we observed significant tumor growth inhibitory effects with two new antiprogestins of seemingly greater potency which cause less unfavorable endocrine side-effects.
In conclusion: combined treatment (antiprogestin plus antiestrogen or LHRH-agonist) may be of value in endocrine therapy of breast cancer
Receptors for hormones and growth factors and (onco)-gene amplification in human ovarian cancer
- …