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

Although tumor DNA content and proliferation are usually determined by flow cytometry (FCM), quantitative microscopic image analysis is a viable alternative technique that also provides important histologic correlations. To compare these methods, we measured DNA content and proliferation in 54 consecutive breast cancers and 15 benign breast lesions by FCM and IA. DNA content determination was concordant in 49 of 54 cancers measured by FCM and IA. Four of the discordant cases were aneuploid by IA and diploid by FCM. There was good correlation between the DNA index (DI) measured by FCM and IA (r = 0.89, P less than 0.0001). Proliferation was assessed by IA quantitation of Ki-67 and PCNA/Cyclin antibody staining, as well as by flow cytometric S-phase fraction (SPF). Ki-67 positivity was greater in breast cancer than in benign controls (21.6% +/- 13.1% vs. 7.9% +/- 5.6% [P less than 0.0001]), as was PCNA/Cyclin positivity (10.2 +/- 6.7% vs. 2.7 +/- 2.5% [P less than 0.0001]). S-phase fraction measured by FCM was 7.9% +/- 5.7% for carcinomas and 3.17% +/- 2.1% for benign controls (P less than 0.003). Ki-67 and Cyclin staining, as well as SPF, were significantly increased in aneuploid compared to diploid tumors, and increased staining was associated with worsening nuclear grade. There were significant correlations between SPF and Ki-67 staining (r = 0.48, P less than 0.0001) and SPF and Cyclin staining (r = 0.48, P less than 0.0001). We conclude that FCM and IA provide comparable measurements of DNA content, although occasional discrepancies occur. Image analysis provides a valuable alternative method for assessing tumor cell proliferation and may offer certain advantages over FCM.
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PMID:Comparative assessment of proliferation and DNA content in breast carcinoma by image analysis and flow cytometry. 197

To find early and sensitive indicators of treatment response in breast cancer, we studied the mRNA levels of proliferation-related genes during growth arrest of the human breast cancer cell lines T47D and MCF7. A sensitive reverse transcriptase-PCR (RT-PCR) technique was used in order to monitor gene expression in small samples of cells. Estrogen-depletion and treatment with tamoxifen effectively induced a G1-arrest in both cell lines, accompanied by a decrease of the mRNA levels of histone H4, cyclin A, cyclin D1, and c-myc. Cyclin A expression decreased most strongly: up to 32-fold within 7 days. The expression of c-fos and WAF1 increased during growth arrest. In conclusion, significant changes of the levels of proliferation-related mRNAs, induced by growth arrest, can be measured in small samples of breast carcinoma cells using RT-PCR. Especially the decrease of the cyclin A mRNA level seems a potential early indicator of clinical response to tamoxifen therapy in breast cancer patients.
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PMID:Growth arrest associated changes of mRNA levels in breast cancer cells measured by semi-quantitative RT-PCR: potential early indicators of treatment response. 758 69

Tumor necrosis factor-alpha (TNF-alpha) demonstrated antimitogenic activity in MCF-7 cells (estrogen receptor-positive human breast cancer cells) in a dose- and time-dependent manner (EC-50 of 2.5 ng/ml). This antimitogenic effect of TNF-alpha was accompanied by a decreased number of cells in S phase in a dose- and time-dependent manner. Based on growth arrest experiments using aphidicolin, it is apparent that TNF-alpha acted in early G1 phase. It did not show antimitogenic effects once cells reentered the S phase based on [3H]thymidine incorporation into DNA and cell cycle analysis. Specificity of TNF-alpha was established by using monoclonal anti-human TNF-alpha antibody. On the basis of Western immunoblot analysis of Rb, p53 and cell cycle inhibitory protein (Cip1) (p21) proteins, TNF-alpha decreased Rb protein expression in a dose- and time-dependent manner whereas it increased the expression level of tumor suppressor p53 protein. TNF-alpha also increased the expression level of Cip1 (p21) protein in a dose-dependent manner. This induction of Cip1 (p21) protein was preceded by the induction of p53 protein in MCF-7 cells. Cip1 (p21) protein associated with cyclin D was also increased. Tumor suppressor Rb protein expression was increased during G1 to S phase progression. Cyclin D protein expression levels were not changed in response to TNF-alpha treatment, although serine/threonine kinase inhibitors such as H7 and the protein kinase C inhibitor staurosporine decreased cyclin D expression levels in MCF-7 cells. Based on experiments with staurosporine, it appears that TNF-alpha does not utilize a protein kinase C pathway in MCF-7 cells. Other cell cycle-related proteins such as Cdk2, Cdc2, and Cdk4 did not show any change in response to TNF-alpha. TNF-alpha did not affect complexes between cyclin D and Cdk2, Cdk4, and Rb proteins in MCF-7 cells. Taken together these results suggest that Rb, p53, and Cip1 (p21) proteins mediate TNF-alpha antimitogenic activity, and TNF-alpha induces growth arrest in the G1 phase in MCF-7 cells.
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PMID:Effects of tumor necrosis factor-alpha on antimitogenicity and cell cycle-related proteins in MCF-7 cells. 762 60

Breast cancer in humans, as in mice and rats, is thought to be the result of sequential changes in the epithelial cells of the mammalian glands. This study examines the altered expression or activation of cell cycle related proteins in an in situ system composed of hyperplasia, preneoplasia and neoplasia of mouse mammary glands. The results showed a high level of cdc2/cdk2 kinase activities in tumors compared to hyperplasias which was independent of cdc2/cdk2 protein levels. Some of the cdk-associated proteins which are thought to regulate cdk kinase activity were examined in these tissues. Cyclin A was overexpressed in all hyperplasias irrespective of their tumorigenic potentials. However, a number of alterations in cyclin E protein were associated with cdk2 and its associated kinase activity during mammary tumorigenesis. First, the level of normal cyclin E (p50) expression was positively correlated with the tumorigenic potentials of different hyperplasia lines. Second, several cyclin E isoforms (p48, p43, p35, p34, p32) were detected only in tumor tissues. Third, a 2.3- and 8.3-fold increase in cyclin E-associated cdk2 kinase activity was present in highly tumorigenic hyperplasias and neoplasias respectively compared to the low tumorigenic hyperplasias. Polymorphic cell nuclear antigen (PCNA) protein bound to cdk2 was a better indicator for cell proliferation and cdk2 kinase activity than the PCNA labeling index. These results suggest a sequential pattern of multiple derangements in factors regulating cdk2 protein function during mammary tumorigenesis. High levels of cdk2 kinase activity are observed only in tumors and appear to be closely related to alterations in cyclin E protein expression.
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PMID:Cell cyclins and cyclin-dependent kinase activities in mouse mammary tumor development. 772 62

Cyclin-dependent kinases (Cdk) act to regulate G1- to S-phase transition in mammalian cells. We have studied the effects of estradiol and the steroidal antiestrogen ICI 182, 780 on induction of Cdk activity and the consequent phosphorylation of retinoblastoma protein (Rb) in estrogen-responsive MCF-7 breast cancer cells. Treatment of growth-arrested MCF-7 cells with physiological concentrations of estradiol led to a time-dependent increase in Cdk2-associated and cyclin E-dependent kinase activity, which was accompanied by hyperphosphorylation of Rb and S-phase entry. Induction of both Cdk2 activity and DNA synthesis by estradiol was dose dependent and was inhibited by coadministration of ICI 182,780. Elicitation of Cdk2 activity was found to require prolonged (> 8h) estradiol exposure. Levels of cyclins E and A were unchanged in MCF-7 cells undergoing G1- to S-transit; however, synthesis and steady state levels of cyclin D1 protein were increased by estradiol. Cdk4-associated Rb kinase activity was evident in MCF-7 cells by 6 h after estradiol exposure and was inhibited by antiestrogen. Cdk2 and Cdk4 protein levels were not altered by estrogen treatment; however, faster migrating, phosphorylated Cdk2 forms increased in estradiol-treated MCF-7 cells by 12 after release from growth arrest. Cdtk-inhibitory activities, associated with p27kip-1, were eliminated from growth-arrested MCF-7 cells after treatment with estradiol but were not eliminated from cells cotreated with estradiol and ICI 182,780. These findings suggest that estradiol regulates G1 progression in MCF-7 cells through direct effects upon Cdk activation, Rb phosphorylation, and by inducing elimination of Cdk inhibitors.
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PMID:Estrogen regulates activity of cyclin-dependent kinases and retinoblastoma protein phosphorylation in breast cancer cells. 873 80

Evidence of the involvement of cyclin genes in genetic alterations in human cancer is growing. In the present study, we investigated the amplification, in human breast and ovarian cancer, of 5 cyclin genes; cyclin A, cyclin D1, cyclin D2, cyclin D3 and cyclin E. For this purpose, a series of 1,171 breast and 237 ovarian tumors tested for DNA amplification by Southern blotting and a subset of 132 breast and 22 ovarian cancers were analyzed for RNA expression levels by slot-blot and Northern blotting. In breast tumors, only cyclin D1 was found to be activated in a sizeable fraction of the tumors (amplification 12.6%, overexpression 19%). Cyclin A, D2, D3, and E genes never, or only on rare occasions, showed increased DNA copy numbers and were never found overexpressed at the RNA level. Amplification of cyclin D1 correlated with ER+ breast cancer and the presence of lymph-node metastasis. Interestingly, we were also able to determine an association with invasive lobular carcinoma. Our data suggest that cyclin D1 activation determines the evolution of a particular subset of estrogen-responsive tumors. Data obtained in ovarian tumors contrasted with observations in breast cancer. Cyclin D1 DNA amplification was much less frequent in ovarian than in breast tumors (3.3% vs. 12.6%), whereas cyclin E amplification and overexpression were observed in a significant number of cases (12.5% and 18.0% respectively). Cyclin A, cyclin D2 and D3 rarely showed anomalies at the DNA level and were never overexpressed. No clear correlation could be observed between amplification of the cyclin E gene and tumor type, stage or grade in ovarian cancer. Data presented here suggest distinct pathways of cyclin activation in human breast and ovarian cancer.
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PMID:Cyclin gene amplification and overexpression in breast and ovarian cancers: evidence for the selection of cyclin D1 in breast and cyclin E in ovarian tumors. 879 62

p21WAF1/Cip1 is an inhibitor of cdk/cyclin complexes, and thus regulates the cell cycle. p21 is also related to cell differentiation and is regulated by wild-type p53, although p53-independent regulatory pathways have been proposed. In order to analyse p21 expression as well as its relationship with p53 in human breast cancer, an immunohistochemical analysis was undertaken of 77 breast carcinomas, 16 of them with an in situ component; 30 adjacent normal tissue samples; and five non-neoplastic specimens. Forty-four infiltrating carcinomas (57 per cent) were p21-positive. Expression of p21 was also observed in pre-invasive lesions, whereas normal ducts were negative or focally and weakly positive. p21 expression was associated with high histological grade (II + III) (P = 0.017) and poor tubule formation (P = 0.002), and was significantly less frequent in lobular carcinomas (P = 0.0001). p21 positivity also correlated with increased proliferation, but this seemed to be dependent on the histological grade. Twenty carcinomas (26 per cent) showed p53 overexpression, but this was not associated with p21 negativity, suggesting the existence of p53-independent mechanisms for p21 regulation in vivo. Cyclin D1CCND1 expression was analysed in the same series and an association between p21 and cyclin D1 expression was found, since 23 of 26 cyclin D1-positive carcinomas were p21-positive (P < 0.001 ...). In conclusion, p21 is frequently overexpressed in breast carcinomas and this occurs in the early stages of neoplastic progression. This overexpression seems to be independent of p53 status and might be involved in cyclin D1 modulation.
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PMID:p21WAF1/Cip1 is associated with cyclin D1CCND1 expression and tubular differentiation but is independent of p53 overexpression in human breast carcinoma. 961 78

Cyclin G, a recent addition to the cyclin family, was initially identified in screens for new src kinase family members and soon thereafter by differential screening for transcriptional targets of the tumor suppressor gene, p53. We have identified cyclin G as being overexpressed in breast and prostate cancer cells using differential display polymerase chain reaction screening. We demonstrate here that cyclin G is overexpressed in human breast and prostate cancer cells and in cancer cells in situ from tumor specimens. Cyclin G expression was tightly regulated throughout the cell cycle in normal breast cells, peaking at the S and G2/M phases of the cell cycle with lower levels in G1. The cell cycle-dependent expression was absent in breast cancer cells. Following DNA damage in normal p53+/+ cells, cyclin G is triggered to cluster in discrete nuclear DNA replication foci that contain replication-associated proteins such as proliferating cell nuclear antigen (PCNA). While p53-/- cells displayed a faint cyclin G nuclear staining pattern, there was no increased expression and no change in distribution of the staining pattern after DNA damage. The specific subcellular localization of cyclin G at DNA replication foci provides an additional link between p53-mediated growth arrest and cell cycle regulation and suggests that cyclin G may act as an effector of p53-mediated events by functional association with replication foci protein(s).
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PMID:Altered regulation of cyclin G in human breast cancer and its specific localization at replication foci in response to DNA damage in p53+/+ cells. 1019 84

The cancer chemopreventive synthetic retinoid N-(4-hydroxyphenyl)retinamide (HPR) can inhibit the growth and induce apoptosis of tumor cells. In this study we analysed the growth suppressive effect of HPR on human breast cancer cell lines in vitro and the role of the retinoblastoma protein (pRb) in this response. Treatment of MCF7, T47D and SKBR3 for 24 - 48 h with 3 microM HPR, a concentration attainable in vivo, resulted in growth inhibition and marked dephosphorylation of pRb involving Ser612, Thr821, Ser795 and Ser780, target residues for cyclin-dependent kinase 2 (Cdk2) the former two, and Cdk4 the latter two. Interestingly, this dephosphorylation of pRb occurred in S-G2-M phase cells, as revealed by experiments on cells fractionated by FACS according to the cell cycle phase, hence suggesting that the retinoid interferes with the regulation of pRb phosphorylation. The in vitro phosphorylation of a GST-pRb recombinant substrate by Cdk2 immunocomplexes from MCF7, T47D and SKBR3 was markedly suppressed after HPR treatment, whereas that by Cdk4 complexes was suppressed in T47D and SKBR3 but not in MCF7. The steady-state levels of Cdk2, Cdk4 and Cyclin A proteins were unaffected by HPR, while those of Cyclin D1 were significantly reduced in all three cell lines. Interestingly, Cyclin D1 downregulation by HPR correlated with transcriptional repression, but not with enhanced proteolysis of Cyclin D1 typically elicited by other retinoids. Collectively, our data suggest that the antiproliferative activity of HPR arises from its capacity to maintain pRb in a de-phosphorylated growth-suppressive status in S-G2/M, possibly through Cyclin D1 downregulation and inhibition of pRb-targeting Cdks. Oncogene (2000) 19, 4035 - 41.
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PMID:pRb and Cdk regulation by N-(4-hydroxyphenyl)retinamide. 1096 60

In this report, we describe the mechanism of TGF-beta receptor type I (RI) repression in the GEO human colon carcinoma cells. Treatment of GEO cells with the DNA methyltransferase inhibitor, 5 azacytidine induced RI expression and restored TGF-beta response. A stably transfected RI promoter-reporter construct (RI-Luc) expressed higher activity in the 5 aza C treated GEO cells, suggesting the activation of a transactivator for RI transcription. Gel shift analysis indicated enhanced binding of proteins from the 5 aza C treated nuclear extracts to radiolabeled Sp1 oligonucleotides specifically contained in the RI promoter. Protein stability studies after cyclohexamide treatment suggested an increase in the Sp1 protein stability from the 5 aza C treated GEO cells. Further, transfection of Sp1 cDNA into untreated GEO control cells increased RI promoter activity and thus induced RI expression. 5 aza C mediated Sp1 expression in Sp1 deficient GEO colon and MCF-7 breast cancer cells also enhanced the activity of several other Sp1 dependent promoters such as TGF-beta receptor type II (RII), Cyclin A and p21/waf1/cip1. These results indicate that restoration of Sp1 in several different types of Sp1 deficient cells leads to enhanced activation of a wide range of Sp1 dependent promoters.
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PMID:Repression of transforming growth factor-beta receptor type I promoter expression by Sp1 deficiency. 1103 Jan 55


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