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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of cancer research and clinical oncology 126 (2000), S. 291-297 
    ISSN: 1432-1335
    Keywords: Key words Estrogen receptor ; Exon truncations ; Breast tumors ; African American women
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Several recent reports have shown that the mortality rate with breast cancer is about three times higher in African American women than in other populations. In addition, the available data also indicate that the tumors are very aggressive and poorly differentiated with a very low frequency of hormone receptors. To gain an insight into the factors that may be responsible for their aggressive tumors, we investigated the transcript profiles of the estrogen receptor (ER), the most important prognostic factor in breast cancer, in the tumors derived from African American women. We analyzed 24 immunohistochemically ER+ and 6 ER− malignant tumors for ER mRNA by reverse transcription polymerase chain reaction using a number of primer pairs. For comparative purposes, 20 ER+ malignant tumor issues derived from Caucasian patients were also included. Our results showed that only 15 of the ER+ tumors from African American women patients had full-length wild-type receptor transcripts and the others exhibited alterations/truncations in exon 8. We also found that the majority of tumors that had alterations/truncations in exon 8 did not express the naturally occurring, more abundant exon 7 deletion transcript. Most of the tumors expressed exon 2, exons 2–3, and exon 5 deletion variant transcripts. Unexpectedly, 2 of the 6 immunohistochemically ER− tumors showed full-length wild-type receptor mRNA but none of the variant transcripts.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-7217
    Keywords: breast cancer ; autocrine growth regulation ; estrogen action ; growth factors ; nude mice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Estrogen receptor (ER)-negative MDA-231 human breast cancer cells have been shown to secrete high concentrations of several growth factors including transforming growth factor-alpha and insulin-like growth factor I, which could have important autocrine or paracrine growth regulatory functions and, additionally, could explain the rapid autonomous growth of these cells. In contrast, the hormone-responsive, ER-positive MCF-7 cells secrete low levels of these factors constitutively. Since estrogen treatment increases secretion of these growth factors in MCF-7 cells, it has been postulated that these growth factors mediate estrogen's growth effects through an autocrine mechanism. To test this hypothesis we reasoned that growth factors supplied by MDA-231 cells should support growth of MCF-7 cells in an estrogen-depleted environment. Inoculation of castrated female athymic nude mice with MDA-231 cells resulted in rapid tumor growth. However, MDA-231 tumors did not support growth of MCF-7 cells inoculated on the opposite flank by an endocrine mechanism; MCF-7 tumors required estrogen supplementation for growth. To determine if MDA-231 cells could support MCF-7 growth by a paracrine mechanism, various mixtures of the two cell lines were coinoculated at the same site in castrated or in estrogen-supplemented mice. ER was not detectable in tumors derived from a mixed inoculum, indicating the absence of MCF-7 cell growth. Furthermore, DNA flow cytometry of these tumors revealed only a single G1 peak representative of MDA-231 cells in estrogen-deprived mice. On the other hand, two distinct G1 peaks representing both MDA-231 and MCF-7 cells were detected in tumors grown in estrogen-supplemented mice. These data demonstrate that growth factors from estrogen-independent MDA-231 cells are not capable of replacing estrogen for growth stimulation of MCF-7 cells. Either estrogen-stimulated growth of MCF-7 cells requires other secreted factors not supplied by MDA-231 cells, or it involves a different mechanism.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-7217
    Keywords: estrogen receptor ; breast cancer ; DNA binding domain ; gel-retardation analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We have used in vitro DNA binding assays as a measure of estrogen receptor (ER) function in human breast tumors. We found that the majority of ER+ (25 ER+/progesterone receptor [PgR]+, and 25 ER+/PgR−) tumors we examined were capable of binding consensus estrogen response element (ERE) oligonucleotides in this assay system. We found significant proteolytic activity in many of the tumors such that protease inhibitors were found to be essential during the preparation of tumor extracts. We next applied direct sequence analysis of the ER DNA binding domain of several of these tumors, and determined that the ER+/PgR− breast tumors did not contain mutations within the DNA binding domain which might explain their apparent discordant receptor phenotype. We did identify an alternatively spliced ER variant missing exon 3 of the DNA binding domain. This variant was unable to function as a transcriptional inducer of an estrogen-responsive reporter in a yeast assay system. Furthermore, the exon 3 ER deletion variant was expressed at equivalent levels in all of the ER+ breast tumors, so that it does not appear to be involved in the evolution of the ER+/PgR− breast cancer phenotype.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-7217
    Keywords: p53 gene ; p53 protein ; breast cancer ; prognostic factor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Mutations in the p53 gene can play a role in the transformation of normal to malignant cells. Because these mutations are more frequently reported later in the course of transformation, their presence could reflect a greater malignant potential of the tumor and, thus, an increased probability of metastasis and recurrence after local therapy. In a pilot study using single-stranded conformation polymorphism analysis (SSCP), 200 node-negative breast tumors were examined for mutations in the region encompassing exons 5 through 9 of the p53 gene. Exons 5 through 9 were tested because they contain 80–90% of known p53 gene mutations. The tumors ranged in size from 1 to 3 cm. 28 tumors were found to have an abnormal band pattern on both initial and repeat analysis. 4 of these tumors were sequenced; 3 contained a p53 mutation and the 4th had a rare neutral polymorphism. Disease-free survival (DFS) at 5 years for women with tumors having an abnormal SSCP analysis was 57% (± 10%), compared to a 79% (± 3%) DFS for the group with a normal pattern. By the log rank test, this difference was highly significant, p ≤ 0.01. The relative risk of recurrence for the group with an abnormal SSCP pattern was 2.2. In a multivariate analysis including ER, PgR, ploidy, S-phase, age, and tumor size, an abnormal p53 by SSCP analysis and patient age were the only factors that independently predicted DFS at 5 years. Conclusion: Women with node-negative breast cancer who have tumors with alterations in the p53 gene, as indicated by SSCP analysis, have a significantly poorer prognosis and a higher rate of relapse at 5 years. The prognostic significance is maintained in a multivariate analysis including many established prognostic factors.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-7217
    Keywords: tamoxifen ; estrogen receptor ; progesterone receptor ; ligand binding assay ; immunohistochemical assay ; drug resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Estrogen (ER) and progesterone receptor (PgR) positive breast tumors often respond to tamoxifen, but ultimately progress as they become tamoxifen resistant. An accurate assessment of receptor status in specimens from tamoxifen-resistant patients could help to understand potential mechanisms of resistance and to predict response to second line hormonal therapies. However, since tamoxifen itself can affect ER and PgR determinations, assay results can be misleading. We measured ER and PgR by both ligand binding (LBA) and immunohistochemical (IHC) assays in 34 tumors from patients on tamoxifen, 30 of whom were displaying resistance to the drug. These tumors were classified into several receptor phenotypes. Eleven patients, 8 of whom were clearly progressing, expressed both receptors while on tamoxifen. ER was significantly less often negative when measured by IHC, suggesting that ER status by LBA was falsely negative in this group due to receptor occupancy by tamoxifen. Six patients had no detectable ER by LBA or IHC but still expressed PgR. The presence of PgR suggests that ER could still be functional, though undetectable, in these tumors, or that PgR is constitutively expressed by them. Finally, 12 patients were ER and PgR-negative by both assays, suggesting hormonal independence as the mechanism for resistance in this group. In a subset of patients with receptor assays both prior to tamoxifen and at the time of progression while taking the drug, we found that most ER-positive tumors converted to an apparent ER-negative status when assayed by LBA, while PgR status frequently remained unchanged. The continued expression of ER and/or PgR in many patients with tumor progression on tamoxifen indicates that mechanisms for resistance other than receptor loss are common in breast cancer.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Breast cancer research and treatment 32 (1994), S. 5-12 
    ISSN: 1573-7217
    Keywords: breast cancer evolution ; carcinogenesis ; carcinoma in situ ; clonal progression ; hyperplasia ; metastasis ; loss-of-heterozygosity (LOH) ; premalignant lesions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In the past few years there has been an explosion in the number of patients diagnosed with hyperplastic breast disease andin situ breast cancer. Based on epidemiological data, these morphologically defined lesions may be categorized as those with little malignant potential (e.g. typical hyperplasia or proliferative disease without atypia [PDWA]), those with significant malignant potential which may already be “initiated” (e.g. atypical ductal hyperplasia [ADH]), and early “transformed” lesions which are malignant but not yet invasive (e.g. ductal carcinomain situ [DCIS]). They may represent sequential evolutionary stages in the ontogeny of invasive breast cancer, with each morphologically defined stage resulting from accumulating genetic changes culminating in a transformed clonal lineage capable of invasion and metastasis. Using loss-of-heterozygosity (LOH) analysis, we are studying the genetic changes associated with these lesions in archival tissue samples. 50% (6/12) of the proliferative lesions (PDWA and ADH) and 80% of the DCIS shared their LOH patterns with more advanced lesions from the same breast, strongly supporting a precursor/product relationship between these lesions and the cancers they accompany.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-7217
    Keywords: apoptosis ; breast cancer ; doxorubicin ; hsp27 ; topoisomerase II
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Previously we demonstrated that heat shock protein 27 (hsp27) overexpression confers resistance to the chemotherapeutic agent doxorubicin in MDA–MB–231 breast cancer cells. Since induction of apoptosis is one underlying mechanism of chemotherapeutic drug action, we investigated the effect of hsp27 overexpression on doxorubicin–induced apoptosis, finding that hsp27 protects MDA–MB–231 cells from apoptosis. We also examined expression of the doxorubicin target, topoisomerase II (topo II), in control and hsp27–overexpressing stable transfectants, as topo II expression is important for both drug sensitivity and the initiation of apoptosis by doxorubicin. The relative levels of both topo IIα and β were higher in the controls than the hsp27–overexpressing clones, suggesting that the apoptotic protective effect of hsp27 overexpression in MDA–MB–231 cells is associated with altered topo II expression.abstract
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-7217
    Keywords: breast cancer cells ; estrogen-regulated proteins ; messenger RNA ; regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We have previously demonstrated an estradiol-regulated 24 kDa (24K) protein in human breast cancer tissue culture cells and human tumor biopsies. The presence of 24K correlates well with the presence of steroid hormone receptors. In order to further study the hormonal regulation of the 24K protein and gene, we have isolated cDNA clones corresponding to the 24K mRNA. Poly(A)+ RNA isolated from the MCF-7 human breast cancer cell line was translated in a cell-free translation system containing [35S]-methionine. The translation products were immunoprecipitated with a 24K monoclonal antibody, and thein vitro synthesis of 24K protein was confirmed by sodium dodecylsulfate (SDS) polyacrylamide gel electrophoresis. The same poly(A)+ RNA was used to construct an oligo(dT)-primed cDNA library in theλgt11 expression vector system. The library was screened with a highly specific polyclonal antibody raised against 24K protein purified by immunoaffinity chromatography. Four recombinant clones reacting with the antibody by virtue of antigen expression were isolated and three were used in hybridization-selected translation. Three clones were able to hybridize specifically to a messenger RNA (mRNA) that yielded a Mr 24,000 protein when translatedin vitro and analyzed by SDS/polyacrylamide gel electrophoresis. This protein was also immunoprecipitable by the 24K monoclonal antibody. MCF-7 mRNA size fractionated by formaldehyde-agarose gel electrophoresis was transferred to nitrocellulose paper and hybridized to a nick-translated 24K cDNA clone. A single band of hybridization corresponding to a mRNA size of approximately 0.9–1.0 kilobase (kb) was observed. Using this same technique, 24K cDNA was hybridized to mRNA extracted from MCF-7 cells that had been treated for varying periods with either estradiol, nafoxidine, or tamoxifen. The 24K mRNA was elevated by the addition of estradiol, and clearly diminished by nafoxidine and tamoxifen. These results demonstrate that we have isolated cDNA clones for the study of the hormonal regulation of the 24K gene in breast cancer cells, and have shown that the mRNA is regulated by estradiol.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Breast cancer research and treatment 32 (1994), S. 13-18 
    ISSN: 1573-7217
    Keywords: benign breast disease ; breast cancer evolution ; carcinogenesis ; ductal carcinoma in situ ; hyperplasia ; immunohistochemistry ; premalignant breast disease ; prognostic factors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Despite modern therapy, one third to one half of patients who get breast cancer will eventually die from it. This disconcerting circumstance has focused attention on prevention, and preventing breast cancer will require a much better understanding of the biological abnormalities underlying its development and progression. Many studies into the mechanisms of invasive breast cancer evolution have evaluated presumed precursor lesions (e.g. proliferative disease without atypia, atypical ductal hyperplasia, and ductal carcinoma in-situ) for genetic alterations known to occur in fully developed invasive carcinomas. This approach has shed some light on events which may be important in early malignant transformation, including the observations that overexpression of the c-erbB-2 oncogene and mutations of the p53 tumor suppressor gene are present in significant subsets of DCIS, but not PDWA or ADH. Although this approach is limited by our incomplete knowledge of cancer genetics, there is still a great deal to learn about breast cancer evolution by evaluating cancer-associated genes in potential precursor lesions using established techniques such as immunohistochemistry and in situ hybridization.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Breast cancer research and treatment 32 (1994), S. 49-55 
    ISSN: 1573-7217
    Keywords: animal models ; antiestrogens ; estrogen receptor variants ; ICI 182,780 ; pure steroidal antiestrogens ; tamoxifen resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Though the antiestrogen tamoxifen prolongs disease-free and overall survival in the adjuvant setting, and induces remissions in over half of the patients with estrogen receptor positive metastatic disease, all patients eventually acquire tamoxifen resistance. Furthermore, many of the resistant tumors actually appear to bestimulated by tamoxifen just as they are by estrogens. In both animal models and clinical specimens, we have found lower tamoxifen uptake and somewhat altered tamoxifen metabolism in resistant tumors, but neither appears to explain tamoxifen stimulation of the resistant tumors. Nor do estrogen receptor losses or mutations appear to explain this phenomenon, although altered expression of transcriptional variant forms of the receptor may well contribute. Pure steroidal antiestrogens such as ICI 182,780 are capable of reversing tamoxifen-stimulated as well as estrogen-stimulated growth of these resistant tumors, and are now in clinical trials for this purpose.
    Type of Medium: Electronic Resource
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