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Biomedical subjects

G C Chamness

Publications and source records attributed to G C Chamness.

At least 19 recordsLinked to original sources
PubMed1992

Prognosis and treatment decisions in patients with breast cancer without axillary node involvement.

BACKGROUND: Every month, treatment decisions must be made for more than 6000 patients with breast cancer without axillary node involvement in the United States. Approximately 70% of these patients will survive more than 10 years after surgery and/or radiation treatment without additional systemic adjuvant therapy. If we had good methods to identify patients who are destined to have a recurrence of their disease, only those patients should receive adjuvant therapy. METHODS: The authors reviewed the literature supporting the use of currently available prognostic factors for patients with node-negative breast cancer, and formulated a framework on which prognostic factor information can be based to help make these treatment decisions. RESULTS: The steps involved in making treatment decisions are: use prognostic factors to determine the recurrence probability; calculate the expected treatment benefit; and weigh the expected benefits against the potential risks. CONCLUSIONS: Prognostic factors can be used to help make treatment decisions for patients with breast cancer without axillary node involvement. However, the final treatment decision must take into account all aspects of the patient and her disease, and the physician must help the patient evaluate her prognostic factors, arrive at an understanding of her particular risk of recurrence, and weigh the potential benefits and risks of adjuvant therapy.

Axilla↗
PubMed1992

Abnormal estrogen receptor in clinical breast cancer.

We have discovered a number of estrogen receptor variants in clinical breast cancer tissues. We have base-pair insertions, transitions, and deletions of exons 3, 5 and 7. Using a transactivation assay we have discovered receptors with outlaw function consisting of both dominant-positive receptors which are transcriptionally active in the absence of estrogen, and dominant-negative receptors which are transcriptionally inactive themselves but prevent normal estrogen receptor function.

Breast Neoplasms↗
PubMed1992

The importance of normal and abnormal oestrogen receptor in breast cancer.

We have used the screening techniques of CMC and SSCP of selected PCR fragments, and also gel retardation assays, to discover a number of ER variants in clinical breast cancer tissues. We have found base pair insertions, transitions, and deletions, and deletions of exons 3, 5 and 7. Using a yeast transactivation assay, we have discovered receptors with outlaw function consisting of both dominant positive receptors that were transcriptionally active in the absence of oestrogen and dominant negative receptors that were transcriptionally inactive themselves but prevented normal ER function. Future efforts should focus in particular on such dominant positive and dominant negative variants. With regard to positive variants, we should like to know whether they stimulate tumour growth and, if so, whether they can be turned off. With regard to dominant negative variants, we should like to determine whether they can inhibit tumour growth and, if so, whether they can be turned on.

Base Sequence↗
PubMed1992

Treatment decisions in axillary node-negative breast cancer patients.

Treatment decisions must be made on 9000 axillary node-negative breast cancer patients each month in the United States. Which of these patients will benefit from adjuvant therapy is a major question. Valid methods are needed to distinguish those patients who are "cured" from those who will suffer a cancer recurrence. A complex network of prognostic variables enters into the treatment decision, together with a risk-versus-benefit assessment. We are using a neural-network-based form of artificial intelligence that, once "trained" with data representing an event and its outcome, can identify subsets of patients with low recurrence risks. Larger data sets are being evaluated with the hope of introducing the neural-network technique to routine clinical practice.

Breast Neoplasms↗
PubMed1991

Progesterone receptor gene restriction fragment length polymorphisms in human breast tumors.

We examined the progesterone receptor (PgR) gene in tissue from both primary human breast tumors and normal placentas, detecting restriction fragment length polymorphisms (RFLPs) with the restriction endonucleases Pst I/Sst I and HindIII. There was a general agreement of the Pst I and Sst I polymorphisms in any individual tumor, suggesting that they define two alleles in the human PgR locus, one being characterized by a deletion of about 300 base pairs with respect to the other. Both primary human breast tumor specimens (n = 36) and human term placentas (n = 48) displayed similar allele frequencies and typical mendelian distribution of these Pst I/Sst I alleles. The previously reported HindIII PgR RFLP was also investigated in 132 breast tumors. The HindIII PgR gene RFLP did not display typical mendelian distribution in the breast tumors; the factors affecting the HindIII allele frequencies are presently unknown. Neither the HindIII RFLP nor the deletion defined by Pst I and Sst I correlated with PgR expression as determined by a ligand-binding assay, suggesting that neither is related to the heterogeneity of PgR expression seen in breast tumors.

Blotting, Southern↗
PubMed1991

Variant human breast tumor estrogen receptor with constitutive transcriptional activity.

Since progesterone receptor (PgR) is normally induced by estrogen, breast cancer lacking estrogen receptor (ER) would also be expected to lack PgR. However, a small percentage of breast cancers are ER- yet PgR+. These tumors might possess an ER which is defective in estrogen binding but is still functional in stimulating estrogen-responsive genes such as PgR. We have now detected such a variant, lacking exon 5 of the hormone-binding domain, using complementary DNA amplified by the polymerase chain reaction. This variant was the predominate ER RNA expressed in three ER-/PgR+ tumors. Furthermore, the variant ER constitutively activates transcription of a normally estrogen-dependent gene construct in yeast cells. The variant ER could explain the expression of PgR in certain tumors and have therapeutic implications.

Base Sequence↗
PubMed1991

17 alpha-substituted analogs of estradiol for the development of fluorescent estrogen receptor ligands.

For the successful development of a high-affinity fluorophore-estradiol conjugate, the fluorophore must be attached to the estradiol molecule at a position that interferes least with its binding to the receptor. We have concentrated on 17 alpha substituents as models for fluorophore attachment, based on literature precedent and on our earlier work with small 17 alpha side chains. In this report, we describe syntheses and estrogen receptor binding affinities of 19 analogs of estradiol substituted in the 17 alpha position with larger side chains (of six to 11 carbons), some of which may be synthetically modified to link a fluorophore. These analogs were synthesized either by nucleophilic cleavage of estrone-17 beta-oxirane 3-benzyl ether and subsequent debenzylation (4 to 18), by cross-coupling of alkynes (21 to 24), by alkylation of 17 alpha-ethynylestradiol 3,17-bis(tetrahydropyranyl ether) and subsequent acidic hydrolysis (25 to 28), or by reacting estrone either with appropriate aryl/alkynyllithium reagents (29, 30, and 32) or with benzylmagnesium bromide (31). Relative binding affinities of these newly synthesized analogs were determined for estrogen receptor (rat uterus) using a standard competition assay. The results suggest that analogs with reduced mobility and/or more polarizable electron density in the side chain generally bind more strongly to the receptor. The relative affinities of several selected compounds were also determined in the presence of 4% dimethylformamide; some compounds bearing larger, nonpolar 17 alpha substituents showed dramatically improved affinities, while affinities for compounds with shorter nonpolar side chains remained largely unchanged. These binding affinity results should be useful in designing new high-affinity fluorescent ligands for the estrogen receptor.

Fluorescence↗
PubMed1991

A potential radioiodinated ligand for androgen receptor: 7 alpha-methyl-17 alpha-(2'-(E)-iodovinyl)-19-nortestosterone.

The presence of androgen receptor (AR) in prostate cancer has been linked to the androgen-dependent nature of the tumor and has also been shown to have prognostic significance; it also appears to be a positive prognostic indicator in breast cancer. However, due to the relatively low AR concentrations in most tumors and the inherently low specific activity of tritium, the assay of AR based on available 3H-ligands is not sensitive enough to measure accurately the amount of receptor in small specimens. A 125I-ligand like those available for the estrogen and progesterone receptors would be helpful, but development of such a ligand for AR has not been very successful. Although several androgen analogues containing iodine, bromine, or selenium have been synthesized specifically as potential probes for AR, none have shown any significant affinity or specificity for the receptor. We therefore undertook the synthesis of new potential AR ligands which could be radioiodinated, and determined their affinities for AR (from rat uterus and MCF-7 human breast cancer cells) by using a competition assay. We have examined both 5 alpha-dihydrotestosterone (5 alpha-DHT) and 19-nortestosterone analogues and have identified two such compounds which showed high AR affinity: (17 alpha,20E)-17 beta-hydroxy-21-iodo-5 alpha-pregn-20-en-3-one (17 alpha-[E)-iodovinyl)-5 alpha-DHT, 9) and 17 beta-hydroxy-7 alpha-methyl-(17 alpha,20E)-21-iodo-19-norpregna-4,20-dien-3- one (7 alpha-methyl-17 alpha-[E)-iodovinyl)-19-nortestosterone, 11). In fact, the affinity of the latter for human AR was found to be superior to that of 5 alpha-DHT itself. These iodovinyl analogues could be easily prepared in the radioiodinated form, and should prove to be extremely useful in assaying low levels of AR in small specimens.

Animals↗
PubMed1991

Estrogen receptor variants in clinical breast cancer.

We have used the screening techniques of chemical mismatch cleavage, single stranded conformational polymorphism, and gel retardation to discover a number of estrogen receptor RNA variants in clinical breast cancer tissues. We have found basepair insertions, transitions, and deletions as well as alternative splicing, yielding deletions of exon 3, 5, or 7. Using a yeast transactivation assay we have discovered receptors with outlaw function, including both a dominant-positive receptor, which is transcriptionally active in the absence of estrogen, and a dominant-negative receptor, which is itself transcriptionally inactive, but prevents the action of normal estrogen receptor. These variants could have clinical significance, helping to explain breast tumor behavior and patient outcome.

Amino Acid Sequence↗
PubMed1990

Estrogen receptor gene methylation in human breast tumors.

DNA methylation is known to be involved in eukaryotic gene control; it may thus exert effects during development and tumorigenesis. We have examined the methylation status of the estrogen receptor (ER) gene in different human tissues. The ER gene was found to be methylated in placental tissues, but normal breast tissues exhibited a different methylation pattern. In addition, specific sites in the hormone-binding domain of the ER gene were observed to be differently methylated in different human breast tumor specimens. We did not detect, however, any association between the ER status of a tumor and ER gene methylation at these sites. Interestingly, a difference in the methylation status between normal and adjacent breast tumor tissues was observed. Thus, DNA methylation may be considered an additional molecular measure of the genetic heterogeneity in breast cancer.

Blotting, Southern↗
PubMed1990

Association of the 323/A3 surface glycoprotein with tumor characteristics and behavior in human breast cancer.

We have earlier described a monoclonal antibody (323/A3) against a Mr 43,000 surface glycoprotein of MCF-7 human breast cancer cells which shows considerable specificity for primary and metastatic breast tumors (Cancer Res., 46: 1306-1317, 1986). Here we report the occurrence of the 323/A3 antigen in a large cohort of primary breast tumors (m = 384) and its interrelationship with several clinically important variables. Frozen, stored tumor tissues were examined by a Western blot procedure, and the level of 323/A3 protein in individual tumors was calculated in arbitrary units based on the integrated Mr 43,000 signal in tumors compared with an MCF-7 internal standard. Thirty-six % (139 of 384) of tumors were found to be positive for 323/A3. Higher frequencies of 323/A3 protein were found in tumors larger than 2 cm (P = 0.03), tumors with infiltrated lymph nodes (P = 0.01), and tumors without estrogen receptor (P = 0.006). No significant relationship was found with patient age, menopausal status, or progesterone receptor status. Of the newer clinical determinants proliferative rate (% S phase), DNA ploidy, and the lysosomal protease cathepsin D, but not the HER-2/neu oncogene protein, were significantly correlated with 323/A3. The presence of 323/A3 protein was also related to increased recurrence (P = 0.003) and mortality (P = 0.036) after primary treatment. As an exposed surface antigen, this glycoprotein might be a useful target in radioimaging and immunotherapy of some human breast tumors, especially those having large size, infiltrated lymph nodes, deficient estrogen receptor, high proliferative rate, abnormal DNA content, and high levels of cathepsin D, all of which are ominous indicators of tumor behavior.

Adult↗
PubMed1990

Cathepsin D and prognosis in breast cancer.

We investigated the possibility that cathepsin D, an estrogen-induced lysosomal protease, might have value as a prognostic factor in breast cancer by studying frozen tissue specimens from 397 patients. We measured the 34-kd mature form of the enzyme by Western blot assay and densitometry. Among 199 patients with node-negative disease, but not among 198 with node-positive disease, high levels of cathepsin D proved to be a significant predictor of reduced disease-free survival (median follow-up, 64 months), either as a continuous variable (log cathepsin D; P = 0.018) or as a dichotomous variable with an optimized cutoff point (P = 0.0001). Results were similar for overall survival (P = 0.009 and 0.0001, respectively). Relating the level of cathepsin D to other prognostic factors in the patients with node-negative disease, we found an association with aneuploidy but none with estrogen or progesterone receptors, tumor size, or the age of the patient. In multivariate analyses, a high level of cathepsin D was the most important independent factor in predicting shorter disease-free and overall survival in patients with node-negative disease. As compared with the risk in women with low levels of cathepsin D, the relative risk of tumor recurrence was 2.6 (95 percent confidence interval, 1.6 to 4.4) and the relative risk of death was 3.9 (95 percent confidence interval, 2.1 to 7.3) among those with high levels of cathepsin D. For disease-free survival, cathepsin D status was predictive of outcome primarily among those with aneuploid tumors; the actuarial five-year recurrence rates of aneuploid tumors were 60 percent among women with high levels of cathepsin D and 29 percent among those with low levels, as compared with 22 percent for all diploid tumors. We conclude that cathepsin D may be an independent predictor of early recurrence and death in node-negative breast cancer.

Biomarkers, Tumor↗
PubMed1989

Estrogen receptor expression in human breast cancer associated with an estrogen receptor gene restriction fragment length polymorphism.

Estrogen receptor (ER) content is a well-known predictor of clinical outcome in human breast cancer. The recent cloning of a human ER complementary DNA has made possible the characterization of the ER gene on a molecular level. We have examined in human breast cancers a single, two-allele restriction fragment length polymorphism using the restriction enzyme PvuII. Initial studies in human breast cancer cell lines suggested a possible association between the absence of one allele and the absence of ER expression; subsequent analysis of allele distribution and frequency in 188 primary human breast tumor biopsies did indeed show a significant but not complete correlation between the absence of one allele and the failure to express ER. Preliminary data suggest that this restriction fragment length polymorphism is located within gene sequences coding for the putative DNA or hormone-binding domains of the ER.

Alleles↗
PubMed1989

125I-ligand for progesterone receptor: 17 alpha-(6'-iodohex-1'-ynyl)-19-nortestosterone.

Progesterone receptor (PgR) is known to be a significant indicator of hormone dependency of a breast tumor and also an important prognostic factor for recurrence and survival. Relatively low specific activity of tritium-labeled ligands makes it difficult to detect the presence of PgR in very small specimens and in specimens with low PgR content. We therefore undertook the synthesis of a radioiodinated progestin. We have synthesized unlabeled 17 alpha-(omega-haloalk-1'-ynyl)-19-nortestosterones with 4, 6, and 8 carbon side chains; these have high affinity for PgR and clear potential for conversion to a 125I form. Since the six-carbon side chain analogue had the highest relative PgR affinity (38% of the affinity of R5020, using PgR from T47D human breast cancer cells), it was selected for preparation of the 125I form by radiohalogen exchange of a omega-bromoalkynyl precursor with carrier-free Na125I. This new ligand was found by Scatchard analysis to have a Kd of 0.47 nM, as compared with [3H]R5020 at 0.22 nM and [3H]progesterone at 2.0 nM. (For affinity studies, all ligands were diluted in dimethylformamide and added to PgR-containing T47D cytosol to give a final DMF concentration of 4%, in order to prevent R5020 and the test compounds from binding nonspecifically to proteins and glass/plasticware.) The new 125I-ligand showed very little instability when stored in ethanol at approximately 10 degrees C even for several months. Thus, 17 alpha-(6'-[125I]iodohex-1'-ynyl)-19-nortestosterone should prove to be a useful ligand for high sensitivity PgR assays.

Binding, Competitive↗
PubMed1989

HER-2/neu oncogene protein and prognosis in breast cancer.

Amplification of the HER-2/neu oncogene was recently reported to predict poor clinical outcome in node-positive breast cancer patients. Since expression of the oncogene as its protein product might be even more closely related than gene amplification to disease progression, we have now examined levels of the HER-2/neu oncogene protein for its prognostic potential in both node-positive and node-negative breast cancer. Using Western blot analysis, levels of this protein were determined in 728 primary human breast tumor specimens. We examined relationships between this protein and other established markers of prognosis, as well as clinical outcome. In node-negative patients (n = 378), the HER-2/neu protein failed to predict disease outcome. However, in node-positive patients (n = 350), those patients with higher HER-2/neu protein had statistically shorter disease-free (P = .0014) and overall survival (P less than .0001) than patients with lower levels of the protein. Higher HER-2/neu protein was found in tumors without estrogen receptor (ER) (P = .02) or progesterone receptor (PgR) (P = .0003), and in patients with more than three positive lymph nodes (P = .04). A significant correlation between levels of the HER-2/neu gene protein and amplification of the gene itself was also found (n = 48, P less than .001). Multivariate analyses in these patients showed that the HER-2/neu protein is a significant independent predictor of both the disease-free and the overall survival in node-positive breast cancer, even when other prognostic factors are considered.

Antibody Specificity↗