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S A Fuqua

Publications and source records attributed to S A Fuqua.

At least 55 records · Page 3Linked to original sources
PubMed1995

Mechanisms of action of antiestrogens.

Investigators from laboratories worldwide have spent nearly 40 years studying the mechanisms by which the diverse class of compounds known as antiestrogens exert their effects. In this review we present an overview of the work to date that has led to a greater understanding of both the classical and the sometimes unexpected actions which an antiestrogenic compound can have on the growth of a cell. In addition, we review work which has begun to explain the means by which some cells can ultimately become resistant to the action of antiestrogens. We conclude with a discussion of the current directions being followed by researchers in this area, as well as with several comments regarding what physiological activities might be desired in an 'ideal' antiestrogenic compound.

Animals↗
PubMed1995

Coexpression of wild-type and variant oestrogen receptor mRNAs in a panel of human breast cancer cell lines.

Wild-type as well as variant oestrogen receptor (ER) mRNAs with exon 5 and 7 deleted were identified in a panel of human breast tumour cell lines by reverse transcriptase-polymerase chain reaction followed by dideoxynucleotide sequence analysis, and then quantitated by ribonuclease protection analysis. All cell lines categorised as ER+ by ligand-binding analysis expressed both wild-type and variant ER transcripts. Most cell lines classified as ER- did not express any ER transcript. However, three ER- cell lines (BT-20, MDA-MB-330 and T47Dco) expressed both wild-type and variant transcripts. A differential pattern of expression of wild type to variant was seen in both ER+ and ER- cell lines, however this pattern was not paralleled by differences in ligand-binding activity. Breast tumour cell lines previously classified as ER- expressed significantly lower levels of ER transcripts than did their ER+ counterparts. In view of these findings, as well as earlier reports that the exon 5 deletion ER variant encodes a dominant-positive receptor, it seems clear that some cell lines are misclassified as ER-, and express both wild-type and variant ER mRNAs, and that the overexpression of this variant may account, in part, for their oestrogen-independent phenotype.

Base Sequence↗
PubMed1995

Genetic aberrations detected by comparative genomic hybridization predict outcome in node-negative breast cancer.

Breast cancer progression is determined by a complex pattern of multiple genetic aberrations the association of which with patient prognosis is unknown. In this study, we have undertaken a genome-wide screening to detect genetic changes associated with clinical outcome in node-negative breast cancer. Comparative genomic hybridization was used to screen for DNA sequence gains and losses across all human chromosomes in 23 tumors from node-negative breast cancer patients with no disease recurrence after at least 5 years of follow-up and in 25 node-negative patients with recurrence during the first 5 years of follow-up. The total number of genetic aberrations (copy number gains and losses) per tumor was significantly greater in the recurrence group (P = 0.019) and in the subgroup of these patients who died as a result of breast cancer (P = 0.0022). When copy number losses and gains were analyzed separately, only losses were significant (P = 0.013 for recurrence and P = 0.002 for overall survival). Of the individual loci involved, a high level gain of the long arm of chromosome 8 was significantly associated with recurrence (P = 0.01, Fisher's exact test). Furthermore, amplification of DNA sequences at chromosome 20q12-13 was found in 7 cases (15%), 6 of which had early recurrence within 32 months of diagnosis. This genome-wide overview by comparative genomic hybridization suggests that genetically advanced node-negative breast cancers having a high overall number of genetic aberrations may have a poor prognosis and that increased copy number of two specific regions, 8q and 20q13, may confer a more aggressive phenotype. Results of this pilot study suggest that determination of the total number of DNA sequence copy number aberrations may help therapeutic decision making. Specific probes should be developed to test the prognostic value of 8q and 20q12-13 amplifications in large numbers of patients.

Aged↗
PubMed1995

Relationship of clone 4 estrogen receptor variant messenger RNA expression to some known prognostic variables in human breast cancer.

To gain insight into the possible biological role of variant estrogen receptor (ER) expression in human breast cancer, we have undertaken a study to determine if the expression of the clone 4 variant ER mRNA was associated with markers of either reduced endocrine sensitivity [i.e., progesterone receptor (PgR) negativity] or a poor prognosis (node positivity, large tumor size, and high percentage S-phase fraction). mRNA levels of clone 4 variant ER and wild-type (WT) ER were assayed by RNase protection assay in 106 breast cancer specimens. The tumors comprised two major groups: "good" prognosis and "poor" prognosis based on several conventional biological prognostic features. Each group was divided into three subgroups (ER+/PgR+, ER+/PgR-, and ER-/PgR-). WT and clone 4 variant ER mRNAs were undetected in ER-/PgR- tumors. We determined that clone 4 variant ER mRNA levels varied proportionately with WT mRNA levels, and regression analysis was used to determine if the amount of clone 4 variant ER mRNA relative to WT was associated with prognosis or PgR content. Significantly higher levels of clone 4 variant ER mRNA relative to WT were found in tumors with markers of poor prognosis compared to those with markers of good prognosis (P = 0.0004). Significantly higher levels of clone 4 variant ER mRNA relative to WT were found in PgR- tumors compared to PgR+ tumors (P = 0.011). Such data are consistent with an association of clone 4 variant ER mRNA expression with progression of human breast cancer from hormone dependence to independence.

Breast Neoplasms↗
PubMed1994

Estrogen receptor mutagenesis and hormone resistance.

The authors have detected a truncated receptor that is lacking the majority of the hormone-binding domain because of the deletion of exon 5. This variant acts as a dominant-positive receptor in the absence of hormones. The exon 5 estrogen receptor (ER) variant, although originally identified in ER-negative, progesterone receptor-positive tumors, now has been found to be coexpressed at variable levels with the wild-type receptor in a large number of ER-positive tumors. Therefore, to establish the significance of its coexpression with the wild-type receptor, the authors transfected the variant into ER-positive MCF-7 cells. MCF-7 transfected cells that now express equivalent levels of the variant as compared with the wild-type receptor are resistant to the growth-inhibitory effects of tamoxifen. The authors hypothesize that the exon 5 ER deletion variant may be involved in clinical tamoxifen resistance and hormone independence.

Cells, Cultured↗
PubMed1994

p53 protein accumulation detected by five different antibodies: relationship to prognosis and heat shock protein 70 in breast cancer.

Nuclear accumulation of p53 protein is associated with a poorer clinical outcome in breast cancer patients. Heat shock protein 70 (hsp70) is a chaperone that binds to mutant p53 and consequently could regulate its accumulation or localization. The aims of this study were to determine if the prognostic significance of p53 accumulation was dependent on the type of antibody used for detection and whether hsp70 was associated with this accumulation. Node-negative breast tumors (n = 169) were examined by immunohistochemistry for nuclear p53, cytoplasmic or nuclear hsp70, and for p53 gene alteration by single-strand conformation polymorphism analysis. Frozen sections of pulverized breast tumors were stained with five p53 antibodies (240, 1801, 421, BP53-12, and CM1), a cocktail of both 240 and 1801, and the hsp70 antibody C92. Protein level was expressed as the sum of a proportion and intensity score (total 0, 2-8) with > or = 2 defined as positive staining. The cocktail 240/1801 gave the highest rate of positive staining (45%), followed by BP53-12 (35%), 1801 (27%), 240 (25%), CM1 (24%), and 421 (18%), with a high correlation between antibodies. Positive staining with each individual antibody or the cocktail was significantly associated with estrogen receptor and progesterone receptor negativity, age < 50, and high S-phase fraction. Only staining detected by the 240/1801 cocktail was associated with significantly worse overall survival; 85 versus 70% at 5 years for p53-negative compared to p53-positive tumors, respectively (P = 0.02). There was no association between nuclear or cytoplasmic hsp70 staining and accumulation of p53. Patients that were p53-negative/cytoplasmic hsp70-positive had a better overall survival than those that were p53-negative/cytoplasmic hsp70-negative. No other combination of p53 and hsp70 status could further define subsets of patients with a significantly different prognosis compared to p53 status alone. Tumors without a detectable p53 gene alteration by single-strand conformation polymorphism but with accumulated p53 protein did not have relatively increased levels of hsp70. We conclude that in node-negative breast cancer, the cocktail of two antibodies, 240/1801, resulted in the highest rate of positive staining and was most strongly associated with overall survival compared with either antibody alone or with the other individual antibodies. By immunohistochemistry, nuclear accumulation of p53 was not associated with cytoplasmic or nuclear hsp70 levels.

Adult↗
PubMed1994

The SH2 domain protein GRB-7 is co-amplified, overexpressed and in a tight complex with HER2 in breast cancer.

SH2 domain proteins are important components of the signal transduction pathways activated by growth factor receptor tyrosine kinases. We have been cloning SH2 domain proteins by bacterial expression cloning using the tyrosine phosphorylated C-terminus of the epidermal growth factor receptor as a probe. One of these newly cloned SH2 domain proteins, GRB-7, was mapped on mouse chromosome 11 to a region which also contains the tyrosine kinase receptor, HER2/erbB-2. The analogous chromosomal locus in man is often amplified in human breast cancer leading to overexpression of HER2. We find that GRB-7 is amplified in concert with HER2 in several breast cancer cell lines and that GRB-7 is overexpressed in both cell lines and breast tumors. GRB-7, through its SH2 domain, binds tightly to HER2 such that a large fraction of the tyrosine phosphorylated HER2 in SKBR-3 cells is bound to GRB-7. GRB-7 can also bind tyrosine phosphorylated SHC, albeit at a lower affinity than GRB2 binds SHC. We also find that GRB-7 has a strong similarity over > 300 amino acids to a newly identified gene in Caenorhabditis elegans. This region of similarity, which lies outside the SH2 domain, also contains a pleckstrin homology domain. The presence of evolutionarily conserved domains indicates that GRB-7 is likely to perform a basic signaling function. The fact that GRB-7 and HER2 are both overexpressed and bound tightly together suggests that this basic signaling pathway is greatly amplified in certain breast cancers.

3T3 Cells↗
PubMed1994

Clinical syndromes of hormone receptor mutations: hormone resistance and independence.

Clinical syndromes of hormone resistance or independence have baffled clinicians for decades. These syndromes sometimes result from mutations or deficiencies in enzymes that activate prohormones or from alterations in signal transduction proteins. The majority of these conditions, however, arise from abnormalities of hormone receptors. We describe examples of syndromes that result from genetic mutations or misexpression of steroid/thyroid hormone receptors, with a specific emphasis on thyroid and androgen resistance syndromes, and estrogen independence in breast cancer.

Animals↗
PubMed1994

Constitutive overexpression of the 27,000 dalton heat shock protein in late passage human breast cancer cells.

We present evidence that the mechanisms controlling induction of heat shock transcription factors (HSFs) and mRNA expression of the 27,000 molecular weight heat shock protein, hsp27, are diverse in human breast cancer cells. Heat shock accumulation of hsp27 RNA is associated with the activation of HSF in MDA-MB-231 cells. We have later passage MCF-7 breast cancer cell lines with elevated, constitutive expression of hsp27 mRNA, perhaps due to hsp27 gene amplification. Estradiol and heat shock treatment no longer affect the level of hsp27 mRNA in these cells. Heat induction of HSF is inhibited in cells overexpressing hsp27, although metal ions and amino acid analogs are still capable of activating HSF. These cells will provide a useful system for characterizing alternative pathways in HSF inhibition and activation.

Adenocarcinoma↗
PubMed1994

Immunohistochemical studies of early breast cancer evolution.

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.

Breast Neoplasms↗
PubMed1994

Mechanisms of tamoxifen resistance.

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 be stimulated 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.

Animals↗
PubMed1994

Heat shock proteins and drug resistance.

Heat shock proteins (hsp's) are induced in cells when exposed to different environmental stressful conditions. We have found that breast cancer cells sometimes express high levels of several hsp's, which may both augment the aggressiveness of these tumors and make them more resistant to treatment. We have shown that hsp70 is an ominous prognostic sign as detected by Western blot assays in node-negative breast tumors, and that hsp27 increases specific resistance to doxorubicin in breast cancer cell lines. These findings have direct clinical application, and suggest that modulating hsp expression may be a therapeutic target for reversal of hsp-associated detrimental cellular effects.

Antineoplastic Agents↗
PubMed1994

Hormone-nuclear receptor interactions in health and disease. The oestrogen receptor.

During the past 30 years, we have learned a great deal about the molecular details whereby the ovarian hormone elicits the feminizing effects that Knauer described in his experiments over a century ago. The ER plays a pivotal role in this process, and potentially in many other physiological processes. The roles of variant receptors, the details of ER-mediated transactivation and the regulation of ER expression and activation are just a few of the important unresolved issues in this field. These are not trivial problems, and their solutions are likely to require much more investigation. This information will provide important clinical insight into breast cancer, lipid metabolism, bone metabolism, prostatic hyperplasia and other diseases. Armed with this basic knowledge, scientists will be better equipped to design rational therapeutic and preventive strategies to combat these major clinical problems.

Animals↗
PubMed1994

Cathepsin D by western blotting and immunohistochemistry: failure to confirm correlations with prognosis in node-negative breast cancer.

PURPOSE: We attempted to replicate and improve on our previous study (N Engl J Med 322:297-302, 1990) that showed that 34-kd cathepsin D levels as determined by Western blotting strongly correlated with disease-free survival (DFS) and overall survival (OS) of axillary node-negative (N-) breast cancer patients. We also examined the prognostic significance of cathepsin D measured by immunohistochemistry (IHC) in these patients. PATIENTS AND METHODS: Western blotting was performed on cytosols from frozen tumor specimens of 927 N- breast cancer patients in the San Antonio Breast Tumor Bank. The monoclonal antibody M1G8 was used to detect cathepsin D (in previous study, a polyclonal antiserum had been used). The same monoclonal antibody was also used for frozen-section IHC staining of tumor specimens from 562 N- patients from the same tumor bank. Levels of cathepsin D expression were then correlated with DFS and OS. RESULTS: Although the levels of cathepsin D expression as measured by Western blotting and IHC correlated with each other and with levels of cathepsin D measured in previous work using Western blotting with the polyclonal antiserum, in this present study, using the monoclonal antibody M1G8, we were unable to demonstrate that cathepsin D expression (measured by either Western blotting or by IHC) correlates with DFS or OS. CONCLUSION: In this study, cathepsin D expression as determined by either Western blotting or IHC using the monoclonal antibody M1G8 failed to improve the prognostic evaluation of N- breast cancer patients. The role of cathepsin D expression as a prognostic factor is still not precisely defined, raising questions about its use in the routine evaluation of N- breast cancer patients.

Analysis of Variance↗
PubMed1993

An exon 5 deletion variant of the estrogen receptor frequently coexpressed with wild-type estrogen receptor in human breast cancer.

Recent evidence suggests that the expression of estrogen receptor (ER) variants in breast cancer may interfere with wild-type (wt) ER function and be related to tumor progression and resistance to hormone treatment. One of these variants, ER delta E5, lacking that part of the hormone-binding domain encoded by exon 5, has previously been identified in breast tumors with the unusual estrogen receptor negative (ER-) and progesterone receptor positive (PgR+) phenotype and found to possess constitutive and hormone-independent transcriptional activity. Using a ribonuclease protection assay, we analyzed 27 breast tumors and 4 breast cell lines for the presence of this variant. We found the ER delta E5 variant to be expressed, not only in all of three ER-/PgR+ tumors but also in 19 of 20 ER+/PgR+ or ER+/PgR- tumors. Moreover, the variant was always coexpressed with and often in excess of wtER. ER delta E5 was also found in three breast cancer cell lines (MCF7, T47D, and ZR75-1), although to a lesser extent than wtER. A complete absence of both ER delta E5 and wtER was noted in four ER-/PgR- tumors and one normal breast cell line (HBL-100). Thus, our data suggest that the occurrence of ER delta E5 in breast cancer may represent a critical stage in tumor progression to autonomy.

Breast Neoplasms↗