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Query: UMLS:C0006142 (breast cancer)
 160,383 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Tyrosine phosphorylation is an important regulatory mechanism in response to the action of growth factors and oncogenes. Since many oncogenes code for tyrosine kinases, increased or altered oncogene expression may be reflected in increased tyrosine kinase activity. In a recent study (Hennipman et al., Cancer Res., 49: 516-521, 1989), we found that the tyrosine kinase activity of the cytosolic and membrane fractions of malignant human breast tissue was significantly higher compared to the benign or the normal breast tissue. Moreover, the increase in the cytosolic fractions was found to be of prognostic value. In the present study we determined the protein tyrosine kinase (PTK) activity of another 72 breast cancer specimens, and it could be shown again that the PTK activity in all 72 of these tumors was elevated compared to normal controls. We characterized these cytosolic PTKs by anion exchange chromatography using fast protein liquid chromatography, and it could be shown that at least two different forms of PTK exist. Using antibodies against a number of known oncogene products, we could determine that at least 70% of the PTK activity in the cytosol originated from the presence of the c-src oncogene product. Both of the PTK activity peaks seen in the fast protein liquid chromatography patterns could be precipitated with the anti-Src antibody. Furthermore, using the MCF-7 breast cancer cell line, it could be shown that the antibody against c-src also precipitated a part of the cytosolic PTK activity. In normal human peripheral lymphocytes, no precipitation of the cytosolic and membrane PTK activity could be achieved using the anti-Src antibody. Inasmuch as the cytosolic PTK activity parallels the malignancy in breast tumors (Hennipman et al., Cancer Res., 49: 516-521, 1989), and the majority of this activity is precipitated by anti-Src antibodies, the c-src protooncogene may play a key role in the manifestation of breast cancer.
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PMID:Characterization of protein tyrosine kinases from human breast cancer: involvement of the c-src oncogene product. 138 Aug 91

The protein tyrosine kinase (PTK) of human breast tumors classified as positive (TM+) or negative (TM-) according to their estrogen and progestin receptor levels was partially characterized with regard to its distribution, kinetic parameters, molecular size, and ability to phosphorylate endogenous mammary proteins. For both types of tumors, PTK activity depended upon the presence of Mn++ (2-5 mM) and/or Mg++ (10-20 mM). The activities, total (per g of tissue) and specific (per mg of protein), were similar for both types of tumors, and an average of 60% of activity was located in cytosolic fractions. The autoradiographic detection of alkali-resistant phosphoproteins after SDS-PAGE showed very similar patterns between corresponding fractions from both types of tumors. Upon gel filtration, two peaks of activity of apparent Mr 245 kDa (peak I) and 47 kDa (peak II) were observed. Peak II was found in both cytosols and extracts from particulate fractions, while peak I was present only in the latter fraction for both TM+ and TM- tumors. The apparent Km's for ATP ranged from 4.1 to 6.6 microM, and from 11 to 34 micrograms/ml for the synthetic substrate poly [Glu80, Tyr20], at an optimal pH of 6.5-7.5. When endogenous alkali-resistant phosphorylation of peaks I and II was determined by autoradiography after SDS-PAGE, two major mammary proteins of Mr 60 and 45 kDa were phosphorylated by peak II and three, Mr 145, 74, and 62 kDa, by peak I.(ABSTRACT TRUNCATED AT 250 WORDS)
Breast Cancer Res Treat 1990 Dec
PMID:Protein tyrosine kinases in human breast cancer: kinetic properties and evidence for the presence of two forms of native enzyme. 209 98

The incidence of amplification of neu oncogene-encoded protein tyrosine kinase in human breast cancer strongly supports the concept that protein tyrosine phosphorylation and dephosphorylation are key regulatory mechanisms in the proliferation, differentiation, and neoplastic transformation of breast epithelial cells. We examined the potential regulatory role of protein tyrosine phosphatases (PTPases) in the maintenance of cellular tyrosine phosphorylation by the introduction of leukocyte common-antigen-related PTPase (LAR-PTPase) cDNA into a tumorigenic human breast carcinoma cell line that overexpressed p185neu protein tyrosine kinase. The transfected human breast carcinoma cells expressed elevated levels of LAR-PTPase as assessed by reverse transcription-polymerase chain reaction and by analysis of LAR-PTPase protein. The LAR-PTPase-transfected human breast carcinoma cells had a significantly (P < 0.01) slower proliferation rate in vitro than control-transfected cells. When LAR-PTPase-transfected cells were inoculated into athymic nude mice, a consistent and significant (P < 0.05) suppression of tumor growth was observed. These results provide evidence that a specific PTPase, LAR-PTPase, can play a suppressive regulatory role in the tumor growth of human breast carcinoma cells that overexpress p185neu protein tyrosine kinase.
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PMID:LAR-PTPase cDNA transfection suppression of tumor growth of neu oncogene-transformed human breast carcinoma cells. 757 97

A procedure for an enzyme-linked immunosorbent assay for the determination of protein tyrosine kinase (PTK) activity from cytosolic and solubilized membrane fractions from breast cancers, is described. The general PTK substrate poly(GluNa, Tyr) 4:1 is coated to the wells of a microtiter plate. After incubation with PTK sample and ATP the amount of phosphorylated tyrosyl residues is quantitated with phosphotyrosine specific antibodies and a secondary peroxidase-labeled antibody. The assay is optimized with respect to coating and phosphorylation conditions. The signal is linear with phosphorylation time and with sample protein concentrations in a sufficiently wide range. The assay is standardized by using both internal and external standards. A lyophilized rat spleen extract is used as an external standard. Its PTK activity, determined by established quantitative methods, can be used to calculate the activity of the breast cancer samples. To eliminate day-to-day variations an internal standard, consisting of BSA-coupled phosphotyrosine, is coated to some wells of the microtiter plate. Interassay variation can be minimized by determination of the ratio of optical densities from internal and external controls. Its variation appeared to be less than 18%. Intraassay variation appears to be < 6%. PTK activities measured with this assay correlated well with those of a nonradioactive dot-blot assay and with conventional radioactive assays in which [32P]ATP is used as the substrate. Compared to these assays it appeared to be more sensitive and far more easy to perform.
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PMID:Standardization of an enzyme-linked immunosorbent assay for the determination of protein tyrosine kinase activity. 768 54

Cellular phosphotyrosine levels are regulated by the balance between protein tyrosine kinases (PTKs) and protein tyrosine phosphatases (PTPs). It is supposed that this balance is disturbed in tumour cells, making the increased or altered activity of PTKs and PTPs likely hallmarks of tumour tissues. Indeed it could be shown that the PTK activity was increased in breast cancer in correlation with prognosis (Hennipman et al., Cancer Res. 49, 516-522, 1989). In the present report we measured the PTP activities in breast cancer and normal breast tissues. An increase of approximately three- to four-fold was measured in the cytosolic tumour fractions compared to normal, whereas the solubilized membrane fraction PTP activity showed an increase in tumours of approximately 1.5-fold. Remarkably, the membrane PTP activity correlated with the presence of tumour positive axillary lymph nodes (p = 0.004), whereas the cytosolic PTP activity correlated with the mitotic index, a higher PTP activity occurring when the mitotic index was higher than 10 (p = 0.0004). These results indicate the membrane PTP activity may be considered as an index of metastatic potential, whereas cytosolic PTP activity may be a measure of the growth capacity of the tumour. The increase of PTP activity in breast cancers was confirmed by enzyme-histochemical studies. In frozen sections of tumours a strong to moderate activity was found in both tumour cells and interstitial cells. In the interstitium membrane activity was most pronounced, whereas in the tumour cells diffuse staining of the cytoplasm together with a clear membrane staining was demonstrated. Immunoblotting with anti-phosphotyrosine antibodies also reveals differences between the tumours and normal tissues, confirming the disturbance of the balance between protein tyrosyl phosphorylation and dephosphorylation in the tumour cells.
Breast Cancer Res Treat 1995 Mar
PMID:Protein tyrosine phosphatase activity as a diagnostic parameter in breast cancer. 774 52

Taxol is an antineoplastic agent with significant activity against ovarian as well as breast cancer. To investigate mechanisms by which taxol exerts its cytotoxic action, taxol-induced apoptosis, characterized by morphologic changes and internucleosomal DNA fragmentation, was examined in a human ovarian tumor cell line. Time-dependent morphologic changes, characteristic of apoptosis, were observed over the same time as the appearance of internucleosomal DNA fragmentation. The specific protein tyrosine kinase inhibitors genistein and herbimycin A, and the ATP depletion agent sodium azide, interfered with taxol-induced DNA fragmentation and clonal cell death. Based on a quantitative reverse transcription-polymerase chain reaction technique, bcl-2 alpha oncogene expression was decreased in conjunction with taxol-induced DNA fragmentation, and this decrease could be blocked by genistein. These results strongly implicate protein tyrosine phosphorylation as an event that mediates apoptosis and, thus, the antitumor activity of taxol in ovarian cancer.
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PMID:Evidence for involvement of tyrosine phosphorylation in taxol-induced apoptosis in a human ovarian tumor cell line. 794 20

The basis for the differential sensitivity of cultured normal human mammary epithelial (HME) cells and a transformed human breast cancer MCF-7 cell line to growth inhibition by the isoflavone genistein and its 4'-methyl ether derivative, biochanin A, was examined. In HME cells genistein is 5-fold more potent as a growth inhibitor than biochanin A, whereas in MCF-7 cells biochanin A and genistein are equally potent as growth inhibitors. Based on its properties as an in vitro protein tyrosine kinase (PTK) inhibitor, biochanin A would be expected to be a less potent growth inhibitor than genistein. To determine whether isoflavone metabolism could account for the observed differences in growth inhibition, metabolism experiments were conducted with HME and MCF-7 cells using [4-14C]genistein and [4-14C]biochanin A. MCF-7 cells extensively metabolized both isoflavones, producing two genistein metabolites with molecular weights of 350 and 380 and three biochanin A metabolites with molecular weights of 270, 350 and 380. In contrast, significant genistein or biochanin A metabolism was not observed in HME cells. Using mass spectrometry and nuclear magnetic resonance analysis, metabolite 350 from genistein and biochanin A experiments was identified as genistein 7-sulfate; biochanin A metabolite 270 was identified as genistein. Metabolite 380 was not unequivocally identified, but appeared to be a hydroxylated and methylated form of genistein sulfate. In MCF-7 cells, genistein 7-sulfate and metabolite 380 were detected primarily in the cell media fraction, suggesting that once formed these polar metabolites were excreted from the cells. These data show that isoflavone metabolism by transformed breast epithelial cells modulates the growth inhibitory effects of genistein and biochanin A. In MCF-7 cells, genistein metabolism was correlated with a decrease in growth inhibition, whereas biochanin A metabolism was associated with an increase in growth inhibition.
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PMID:The role of metabolism in mammary epithelial cell growth inhibition by the isoflavones genistein and biochanin A. 882 7

An enzyme-linked immunosorbent assay is described for the determination of protein tyrosine kinase activity originating from the presence of src-like tyrosine kinases in biological samples. In this assay a peptide derived from p34cdc2, cdc2(6-20)NH2, is coupled to the wells of a maleic anhydride-activated microtiter plate. This particular peptide has been described as an efficient and specific substrate for protein tyrosine kinases belonging to the src family kinases (Cheng et al., J.Biol.Chem. 267 (1992) 9248-9256). After incubation of the coated substrate with sample and ATP, the amount of phosphorylated tyrosyl residues is determined with phosphotyrosine specific antibodies and a secondary peroxidase-labeled antibody. The assay appears to be very sensitive and is linear with sample protein concentration and phosphorylation time. Intra-assay variation is < 5%, whereas day-to-day variation is < 10%. The results of the assay have been compared with an ELISA in which the broad-specificity tyrosine kinase substrate poly(GluNa,Tyr)4:1 was coated. The results of both assays in 27 cytosolic breast cancer samples correlated very well (r = 0.94), in accordance with the predominant expression of src kinase activity in breast cancers (Ottenhoff-Kalff et al., Cancer Res. 52 (1992), 4773-4778). The present assay provides an easy, reproducible, and quick alternative for the usual radioactive methods used for the determination of src-kinase activities including immunecomplex kinase assay and TCA-precipitation assays. It allows the determination of src-like activities in human tumors for routine diagnostic purposes.
Breast Cancer Res Treat 1996
PMID:An enzyme-linked immunosorbent assay for the determination of src-family tyrosine kinase activity in breast cancer. 887 22

Genistein is a naturally occurring dietary protein tyrosine kinase (PTK) inhibitor that is hypothesized to be responsible for the lower rate of breast cancer observed in Asian women consuming soy. Although genistein is a potent in vitro PTK inhibitor, its mechanism of action in vivo is not known. In vivo, breast cancer growth is regulated by estrogens and peptide growth factors, such as epidermal growth factor (EGF), the receptor of which has intrinsic PTK activity. Therefore, genistein may block mammary epithelial cell growth by interfering with signal transduction events stimulated by estradiol or growth factors. The effect of genistein, related isoflavones, and other tyrosine kinase inhibitors on fetal bovine serum-, estradiol-, and EGF-stimulated cell growth and signal transduction pathways was examined in five human breast cancer cell lines. Genistein inhibited the growth of these cells by each of the growth stimuli with IC50 values ranging from 2.6 to over 20 micrograms/ml. Growth inhibition by genistein was cytostatic and reversible at IC50 concentrations. Related isoflavones were less potent growth inhibitors than genistein, whereas the synthetic PTK inhibitor tyrphostin A25 was an equally potent growth inhibitor. The mechanism of genistein growth inhibition in human breast cancer cells did not depend on the presence of functional estrogen receptor signaling pathways or on inhibition of EGF-receptor PTK activity. Furthermore, genistein (< or = 20 micrograms/ml) did not decrease constitutive or EGF-induced tyrosine phosphorylation as determined by Western blotting with antiphosphotyrosine antibodies. These data suggest that although genistein inhibits the growth of breast cancer cells in culture, it does so without gross inhibition of PTK activity.
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PMID:Genistein inhibits both estrogen and growth factor-stimulated proliferation of human breast cancer cells. 889 38

Tyrosine kinase dependent oncogenes and growth factor receptors are of prognostic importance in breast cancer, but the relation of cytosolic protein tyrosine kinase (PTK) activity to traditional prognostic indicators is poorly defined. We determined cytosolic PTK activity in tumor extracts of 61 women with invasive breast cancer, including 51 primary specimens and 12 nodal or metastatic specimens, 7 women with in situ breast cancer, and 8 control breast specimens. PTK activity (pmol/min/mg) was measured in a dot blot assay using phosphotyrosine antibodies to detect phosphorylated tyrosyl residues in the tissue extracts. Compared with control specimens (mean PTK = 20.5), tyrosine kinase activity was significantly greater in invasive primary cancers (mean PTK = 298.1; p = 0.0008), and nodal/metastatic specimens (mean PTK = 491.5; p = 0.0009). PTK levels of invasive cancers did not correlate with age (p = 0.36), tumor size (p = 0.83), nodal status (p = 0.37), estrogen receptor status (p = 0.66), or progesterone receptor status (p = 0.09). Thus, while tyrosine kinase activity is increased in breast cancer, correlations with traditional prognostic indicators were not found.
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PMID:Protein tyrosine kinase activity in breast cancer and its relation to prognostic indicators. 892 Jul 63


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