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

In this study the effects of all-trans retinoic acid (ATRA) on cell cycle and apoptosis of MCF-7 human breast cancer cells were investigated to elucidate the mechanisms underlying the antineoplastic potential of this retinoid in breast cancer. The antiproliferative effect of ATRA was evaluated by DNA content measurements and dual-parameter flow cytometry of bromodeoxyuridine (BrdU) incorporation and of the expression of cell cycle-related proteins (Ki-67 as proliferation marker and statin as quiescence marker) vs DNA content. Apoptosis was also studied by flow cytometry of either DNA content or Annexin V labelling. After 10(-6) M ATRA treatment, the fraction of S-phase cells decreased significantly, and cells accumulated in the G0/G1 range of DNA contents. Dual-parameter flow cytograms showed a decrease in the percentage of Ki-67-labelled cells (after 10 days, only 20% of the cells were still positive for Ki-67 compared with 95% in controls), while the fraction of statin-positive cells increased slightly. From 3 days of treatment onwards, apoptosis was found to occur. These results show that ATRA-induced inhibition of MCF-7 cell growth is related to two mechanisms, i.e. the block of cell proliferation, mostly in a pre-S phase, and the induction of apoptosis. These results should be taken into account when attempting to design treatment programmes that associate ATRA with antineoplastic compounds of different cell cycle specificity.
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PMID:All-trans retinoic acid (ATRA)-induced apoptosis is preceded by G1 arrest in human MCF-7 breast cancer cells. 946 Sep 87

High-resolution two-dimensional gel electrophoresis (2-DE) and database analysis was used to establish protein expression patterns for cultured normal human mammary epithelial cells and thirteen breast cancer cell lines. The Human Breast Epithelial Cell database contains the 2-DE protein patterns, including relative protein abundances, for each cell line, plus a composite pattern that contains all the common and specifically expressed proteins from all the cell lines. Significant differences in protein expression, both qualitative and quantitative, were observed not only between normal cells and tumor cells, but also among the tumor cell lines. Eight percent (56/727) of the consistently detected proteins were found in significantly (P< 0.001) variable levels among the cell lines. Eight proteins present in normal cultured breast epithelial cells were not detected in any of the tumor cell lines. We identified a subset of the differentially expressed proteins using a combination of immunostaining, protein sequencing, comigration, and subcellular fractionation. These identified proteins include the intermediate filament components vimentin and cytokeratins. The cell lines can be classified into four distinct groups based on their intermediate filament protein profile. We also identified heat shock proteins; hsp27 and hsp60 varied in abundance and in some cases in the relative phosphorylation levels among the cell lines. Many of the differentially expressed proteins we identified have roles in cellular proliferation and differentiation, including annexin V, elongation initiation factor 5A, Rho GDP dissociation inhibitor, and prohibitin. We identified inosine-5-monophosphate dehydrogenase in each of the cell lines, and found the levels of this enzyme in the tumor cell lines elevated 2- to 20-fold relative to the levels in normal cells. These results expand the human breast epithelial cell protein database (http:// www.anl.gov/CMB/PMG) which is being built to assist researchers with the identification of abnormal patterns of expression and pathways associated with malignancy.
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PMID:Analysis of differential protein expression in normal and neoplastic human breast epithelial cell lines. 954

Tissue factor (TF), the membrane glycoprotein that initiates blood coagulation, is constitutively expressed by many tumor cells and is implicated in peri-tumor fibrin deposition and hypercoagulability in cancer. Upregulation of tumor TF correlates with enhanced metastatic potential. Furthermore, TF has been colocalized with VEGF in breast cancer, specially at sites of early angiogenesis. There are no data on the effect of hypoxia on tumor cell TF expression. Since hypoxia is known to stimulate VEGF production, we studied whether this also induces tumor cell TF expression. Confluent monolayers of A375 melanoma, MCF-7 breast carcinoma and A549 lung carcinoma were cultured in either 95% air, 5% CO2 (normoxic) or 95% N2, 5% CO2 (hypoxic; 25-30 mmHg) for 24 h. Procoagulant activity (PCA) was measured by amidolytic and clotting assays, surface TF antigen by flow cytometry, early apoptosis by annexin V binding and VEGF levels in culture supernatants by ELISA. Hypoxia significantly increased tumor cell PCA in all three cell lines tested and TF antigen on A375 cells was increased four-fold (P <0.05). Pentoxifylline (PTX), a methylxanthine derivative, significantly inhibited the hypoxia-induced increase in PCA as well as VEGF release in all three cell lines tested. In A375 cells, PTX significantly inhibited TF antigen expression by both normoxic and hypoxic cells. Hypoxia induced a slight (5%) but not significant, increase in early apoptosis. Intravenous injection of hypoxic A375 cells into nude rats produced more pronounced thrombocytopenia (n = 5, P <0.01) and more lung metastases (n = 3, P <0.05) compared to normoxic cells. We conclude that hypoxia increases TF expression by malignant cells which enhances tumor cell-platelet binding and hematogenous metastasis. Hypoxia-induced upregulation of TF appears to parallel that of VEGF, although the mechanism remains unclear.
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PMID:Pentoxifylline inhibits hypoxia-induced upregulation of tumor cell tissue factor and vascular endothelial growth factor. 979 77

A breast tumor hypoxia model used to simulate conditions which may exist within an enlarging tumor was examined using documented methods for identifying mechanisms of cell death and compared to the mitochondrial membrane-specific APO2.7 antigen expression. Hypoxic conditions were induced by holding cell pellets of MDA-MB-175-VII breast carcinoma cells in tightly capped centrifuge tubes for up to 10 days. Cells were harvested at 1.5, 3, 4.5, 6, 12, 18, and 24 h, and each 24 h thereafter to 10 days. APO2.7 was monitored in unprocessed cells (no permeabilization prior to staining) for all time points and processed cells (permeabilized prior to staining) for only the first 24 h. Cell viability probes trypan blue and anti-tubulin antibody showed a rapid increase in staining over the first 24 h, as did the phosphatidylserine-specific annexin V and DNA fragmentation by flow cytometry (range of 60-81% positive staining). Light scatter changes indicative of cell death were also quite remarkable. APO2.7 staining never exceeded 42% of the cell pellet over the 10 days of testing compared to greater than 95% staining for all other methods tested. When APO2.7 antigen expression was examined with respect to depth in the cell pellet, it was apparent that cells deeper in the pellet expressed APO2.7 more rapidly; however, fewer cells stained and cells showed fewer apoptotic features on an ultrastructural level than cells at the cell media interface. The study indicates that the anti-APO2.7 antibody may be able to discern apoptotic and incomplete apoptotic cells from necrotic MDA-MB breast cancer cells, traversing a heterogeneous pathway to cell death induced by hypoxia.
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PMID:APO2.7 defines a shared apoptotic-necrotic pathway in a breast tumor hypoxia model. 982 43

It is known that steroids can induce cell surface receptor aggregation followed by activation of receptor and nonreceptor tyrosine kinases. It has been shown recently that 17beta-estradiol (E2) can stimulate the Src/p21ras/mitogen-activated protein kinase pathway in breast cancer cells, and this effect is supposed to mediate the E2-induced stimulation of breast cancer cell proliferation, possibly via activation of the c-fos and c-jun early genes or of genes involved in cell cycle control. Here we demonstrate the existence of an alternative mechanism of the cancer-promoting effect of E2. Human breast cancer cells (MCF-7) were exposed to the known proapoptotic agent vitamin E succinate (VES), added alone or together with different concentrations of E2. E2 conjugated with bovine serum albumin (E2-BSA), which cannot cross the plasma membrane of living cells, was also used in some experiments to assess whether E2 acted on the cell surface or at intracellular receptors. Apoptosis was analyzed by fluorescence-activated cell sorting after cell staining with propidium iodide and FITC-labeled annexin V. E2 showed a concentration-dependent stimulatory effect on spontaneous apoptosis but inhibited the VES-induced apoptosis. However, effects produced by the same molar concentrations of E2 were different when the hormone was free and when it was used in the form of the E2-BSA conjugate. The effects of E2 and E2-BSA were sensitive to genistein, a tyrosine kinase inhibitor. These data show that E2 modulates apoptosis of breast cancer cells, probably acting both at the cell surface and inside the cells. Tyrosine phosphorylation is involved in the signaling pathways mediating this E2 effect.
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PMID:Estradiol modulates breast cancer cell apoptosis: a novel nongenomic steroid action relevant to carcinogenesis. 1032 69

Progesterone inhibits the proliferation of normal breast epithelial cells in vivo, as well as breast cancer cells in vitro. But the biologic mechanism of this inhibition remains to be determined. We explored the possibility that an antiproliferative activity of progesterone in breast cancer cell lines is due to its ability to induce apoptosis. Since p53, bcl-2 and survivin genetically control the apoptotic process, we investigated whether or not these genes could be involved in the progesterone-induced apoptosis. We found a maximal 90% inhibition of cell proliferation with T47-D breast cancer cells after exposure to 10 microM progesterone for 72 h. Control progesterone receptor negative MDA-231 cancer cells were unresponsive to 10 microM progesterone. The earliest sign of apoptosis is translocation of phosphatidylserine from the inner to the outer leaflet of the plasma membrane and can be monitored by the calcium-dependent binding of annexin V in conjunction with flow cytometry. After 24 h of exposure to 10 microM progesterone, cytofluorometric analysis of T47-D breast cancer cells indicated 43% were annexin V-positive and had undergone apoptosis and no cells showed signs of cellular necrosis (propidium iodide negative). After 72 h of exposure to 10 microM progesterone, 48% of the cells had undergone apoptosis and 40% were annexin V positive/propidium iodide positive indicating signs of necrosis. Control untreated cancer cells did not undergo apoptosis. Evidence proving apoptosis was also demonstrated by fragmentation of nuclear DNA into multiples of oligonucleosomal fragments. After 24 h of exposure of T47-D cells to either 1 or 10 microM progesterone, we observed a marked down-regulation of protooncogene bcl-2 protein and mRNA levels. mRNA levels of survivin and the metastatic variant CD44 v7-v10 were also downregulated. Progesterone increased p53 mRNA levels. These results demonstrate that progesterone at relative high physiological concentrations, but comparable to those seen in plasma during the third trimester of human pregnancy, exhibited a strong antiproliferative effect on breast cancer cells and induced apoptosis.
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PMID:Bcl-2, survivin and variant CD44 v7-v10 are downregulated and p53 is upregulated in breast cancer cells by progesterone: inhibition of cell growth and induction of apoptosis. 1070 95

Annexin V is a Ca2+-dependent phospholipid binding protein. Although it has been shown to inhibit protein kinase C (PKC) in cell-free systems, its role in the intact cell is unclear. A stable MCF-7 human breast cancer cell overexpression system was established to investigate the function of annexin V. In these cells, 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced phosphorylation and kinase activity of ERK1/2 were suppressed. Morphological changes induced by TPA were reduced by annexin V overexpression as well as by the pan-PKC inhibitor, bisindolylmaleimide I, and by the mitogen-activated protein kinase/extracellular signal-regulated kinase kinase (MEK) inhibitor, PD98059. TPA-induced MEK1/2 and Raf-1 phosphorylation were reduced in these cells. The TPA-enhanced active Ras, and its association with Raf-1, were reduced. TPA treatment of MCF-7 cells caused an increased association of Shc with Grb2. However, this increased association was prevented in the annexin V-overexpressors. p21WAF/CIP1 is responsible for inhibition of cell cycle progression in MCF-7 cells. TPA induced the expression of p21WAF/CIP1 to a greater extent in MCF-7 parent and control plasmid cells than in annexin V overexpressors. PD98059 inhibited this increase, suggesting that TPA upregulation of p21WAF/CIP1 occurs via the MEK pathway, and that annexin V overexpression blunts it. This work shows that annexin V overexpression suppresses the TPA-induced Ras/ERK signaling by inhibiting at/or upstream of Shc, possibly through the inhibition of PKCs. Oncogene (2000).
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PMID:Annexin V inhibits the 12-O-tetradecanoylphorbol-13-acetate-induced activation of Ras/extracellular signal-regulated kinase (ERK) signaling pathway upstream of Shc in MCF-7 cells. 1087 41

Disruption of integrin-extracellular matrix interactions in normal epithelial cells induces apoptosis, a process termed anoikis. Reduced sensitivity to anoikis appears to be an important hallmark of oncogenic transformation, particularly in the process of metastasis. Several pathways have been implicated in the suppression of anoikis, however, the events which take place proximal to the integrin receptors remain unclear. Integrin-linked kinase (ILK) is an integrin-interacting protein kinase which has been identified as a potential PDK-2, as it is capable of phosphorylating PKB/Akt on Ser-473, and stimulating its activity. Here, we show that ILK activity is stimulated upon adhesion of SCP2 mouse mammary epithelial cells to fibronectin, and inhibited in suspended cells. Overexpression of ILK in the anoikis-sensitive SCP2 cells results in a profound inhibition of anoikis, as determined by annexin V binding and activation of caspases 8 and 3. This effect is reversible by the transfection and expression of a dominant-negative, kinase deficient ILK (ILK KD), as well as by a dominant negative PKB/Akt (PKB AAA). On the other hand, transfection of a dominant negative form of FAK (FRNK) failed to reverse the suppression of anoikis by ILK. Furthermore, inhibition of ILK activity induced anoikis in two anoikis-resistant human breast cancer cell lines. These findings suggest that ILK plays a major role in the suppression of anoikis.
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PMID:The integrin-linked kinase (ILK) suppresses anoikis. 1094 37

Retinoid signaling via retinoic acid (RA) and retinoid X receptors (RARs and RXRs) regulates mammary epithelial cell growth and differentiation. Loss of RAR-beta might represent an early event during breast carcinogenesis. Higher differentiated, estrogen-dependent, estrogen receptor (ER)-positive (ER+) mammary carcinoma cells have been found to contain relatively high levels of RAR-alpha and to be responsive to retinoids, whereas most undifferentiated, estrogen-independent, ER-negative (ER-) cells are characterized by low RAR-alpha expression and by retinoid resistance. In contrast, RAR-gamma is detectable at equal levels in both ER+ and ER- cells. In the present investigation, we directly examined the relative contribution of the distinct retinoid receptors to the retinoid response of breast cancer cells by comparing the effects of low concentrations of specific retinoids, which selectively activate individual receptor subtypes, on growth, cell cycle distribution, apoptosis, and on the autoregulation of RAR-alpha and RAR-gamma in ER- SK-BR-3 and ER+ T47D breast cancer cells. In vitro growth activity was determined by using a colorimetric cell viability assay and analysis of cell cycle distribution, and apoptosis was performed by flow cytometry of propidium iodide-stained or fluorescent Annexin V-labeled cells, respectively, whereas expression of RAR-alpha and RAR-gamma was determined by Northern blotting. Both cell lines are retinoid sensitive and express high amounts of RAR-alpha, RAR-gamma, and RXR-alpha. RAR-alpha-selective compounds (AM80 and AM580) inhibit cell growth, induce G1 arrest, stimulate apoptosis, and up-regulate RAR-alpha and RAR-gamma mRNA as efficiently as RAR/RXR-pan-reactive (9-cis RA) and RAR-pan-reactive retinoids (all-trans RA, TTNPB). Remarkably, an RAR-alpha antagonist (Ro 41-5253) not only blocks the RAR-alpha-selective agonists but also the pan-reactive compounds. In contrast, RAR-13-selective (CD417), RAR-gamma-selective (CD437/AHPN), and RXR-alpha-selective (Ro 25-7386) retinoids exert no effects on the examined parameters. Thus, our results support the idea that RAR-alpha is the crucial receptor mediating the biological effects during retinoid signaling in both ER- SK-BR-3 and ER+ T47D human breast cancer cells.
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PMID:Activation of retinoic acid receptor alpha is sufficient for full induction of retinoid responses in SK-BR-3 and T47D human breast cancer cells. 1103 91

Peroxisome proliferator-activated receptor (PPAR) gamma is expressed in human colon cancer, prostate cancer and breast cancer cells, and PPARgamma activation induces growth inhibition in these cells. PPARgamma expression in human gastric cancer cells, however, has not been fully investigated. We report the PPARgamma expression in human gastric cancer, and the effect of PPARgamma ligands on proliferation of gastric carcinoma cell lines. Immunohistochemistry was used to demonstrate the presence of PPARgamma protein in surgically resected specimens from well differentiated, moderately differentiated and poorly differentiated adenocarcinoma. We used reverse transcription-polymerase chain reaction and Northern and Western blot analyses to demonstrate PPARgamma expression in four human gastric cancer cell lines. PPARgamma agonists (troglitazone and 15-deoxy-Delta(12,14)-prostaglandin J2) showed dose-dependent inhibitory effects on the proliferation of the gastric cancer cells, and their effect was augmented by the simultaneous addition of 9- cis retinoic acid, a ligand of RXRalpha. Flow cytometry demonstrated G1 cell cycle arrest and a significant increase of annexin V-positive cells after treatment with troglitazone. These results suggest that induction of apoptosis together with G1 cell cycle arrest may be one of the mechanisms of the antiproliferative effect of PPARgamma activation in human gastric cancer cells.
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PMID:Expression of peroxisome proliferator-activated receptor (PPAR)gamma in gastric cancer and inhibitory effects of PPARgamma agonists. 1104 67


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