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Biomedical subjects

A K Tandon

Publications and source records attributed to A K Tandon.

At least 37 records · Page 2Linked to original sources
PubMed1990

HER-2/neu amplification predicts poor survival in node-positive breast cancer.

HER-2/neu protooncogene amplification and protein expression were analyzed with slot blot and Western blot techniques, respectively, in more than 300 invasive primary breast tumors of all stages. Amplification (2- greater than 30 copies) was found in 17% of these tumors and high expression was seen in 19%. There was a striking coincidence between gene amplification and high expression. Tumors associated with many involved axillary lymph nodes or with Stage IV disease were more often HER-2/neu amplified or overexpressed. Furthermore, gene alteration was strongly correlated with the absence of steroid receptors and with larger tumor size. High expression without gene amplification was seen in a minor subset of tumors of less aggressive character. Neither amplification nor overexpression was correlated with disease outcome for patients with negative axillary lymph nodes. For node-positive patients, however, HER-2/neu amplification was a significant predictor of early relapse and death (median follow-up = 45 months), and a similar trend, although not significant, existed for high gene expression. Multivariate analyses indicated that HER-2/neu alterations were not independent predictors of patient outcome.

Amino Acid Sequence↗
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↗
PubMed1990

Isolation and characterization of an adriamycin-resistant breast tumor cell line.

An adriamycin-resistant human breast tumor cell line MDA-A1R was generated by step-wise selection in increasing concentrations of drug from the parent cell line MDA-MB-231. MDA-A1R cells grow as loosely attached cell aggregates with a doubling time of 28-32 h; the MDA-MB-231 parent cell line grows as a standard monolayer culture with a 20-h doubling time. The MDA-A1R cell line is highly resistant to adriamycin compared to the parent cell line, and is cross-resistant to velban and colchicine suggestive of a multidrug resistance (MDR) phenotype. MDA-A1R cells exhibit reduced net adriamycin content as compared to the parent cell line. The MDR-associated P-glycoprotein gene is amplified approximately 10- to 30-fold in MDA-A1R cells. P-glycoprotein sequences are overexpressed in the resistant cells and are stable for up to 13 wk after drug removal. Moreover, MDA-A1R cells show the presence of very high levels of P-glycoprotein. MDA-A1R is thus an in vitro model system to study the mechanism of MDR in human breast cancer.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
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↗
PubMed1989

Electrophoretic analysis of 248 clinical breast cancer specimens for P-glycoprotein overexpression or gene amplification.

Multiple drug resistance (MDR), consisting of acquired cross resistance to anthracyclines, vinca alkyloids, and other antineoplastic antibiotics, has been described in a variety of cell lines. This MDR phenotype is associated with overexpression and sometimes amplification of a gene coding for a 170 kDa glycoprotein, termed P-glycoprotein. To understand the role of this mechanism in clinical breast cancer, 248 breast cancer specimens representing both untreated primary and refractory relapsing disease were probed for evidence of P-glycoprotein gene amplification or overexpression using Southern, Northern, or Western blot techniques. In no case was an increase in P-glycoprotein gene copy number or expression detected. Though these findings do not necessarily rule out a role for P-glycoprotein in mediating drug resistance in breast cancer, electrophoretic analysis of clinical specimens is unlikely to provide useful predictive information. More sensitive assays must be developed to overcome the difficulties inherent in analyzing heterogenous tissue samples.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1989

Dermatitis artefacta.

Dermatitis artefacta is an uncommonly encountered condition. This paper presents a case report of two such rare patients. The symptomatology and history of fourteen and sixteen year old males with dermatitis artefacta are described. Possible psychophysiological aetiology of the cases is discussed.

Adolescent↗
PubMed1988

Transforming growth factor beta: potential autocrine growth inhibitor of estrogen receptor-negative human breast cancer cells.

Transforming growth factor beta (TGF beta), a two-subunit Mr 25,000 polypeptide, inhibits growth of several epithelial human cancer cell lines and has been proposed as an autocrine growth inhibitor. TGF beta activity has been found in conditioned media from some breast cancer cell lines, and TGF beta mRNA has been detected in breast cancer cell lines and human breast cancer specimens. In the present study we attempted to characterize the interaction of TGF beta with breast cancer cells by examining the biological activity, receptor binding, and secretion of this polypeptide by a panel of estrogen receptor (ER)-positive and ER-negative human breast cancer cell lines. Growth of the four ER-negative lines, MDA231, MDA330, HS578T, and BT20, was exquisitely sensitive to TGF beta. Dose-dependent inhibition of monolayer growth, anchorage-independent growth, and of [3H]thymidine incorporation was observed with TGF beta concentrations ranging from 1 to 100 pM. Growth of the four ER-positive lines, T47D, ZR75-1, and two MCF7 lines from different laboratories, was unaffected by similar concentrations of TGF beta. In receptor-binding studies using 125I-TGF beta, the four ER-negative lines exhibited specific high affinity TGF beta receptors. Binding was a time- and temperature-dependent process. Scatchard analysis of the binding data showed between 2800 and 12900 receptor sites per cell and a Kd between 29 and 160 pM. Epidermal growth factor, insulin, insulin-like growth factors I and II, and transforming growth factor alpha did not compete for 125I-TGF beta binding. Chemical cross-linking studies with ER-negative breast cancer cells revealed three specific TGF beta receptors with molecular weights approximating 400,000, 92,000, and 69,000. The four ER-positive lines had no detectable TGF beta binding. Using a radioreceptor assay with A549 cells and a NRK bioassay, TGF beta activity was detectable in the conditioned media from the four ER-negative cell lines; media from the ER-positive lines had low levels of TGF beta activity. In summary, ER-negative, estrogen-independent cultured human breast cancer cells have receptors for, are inhibited by, and secrete TGF beta activity, suggesting the possibility that this polypeptide may function as an autocrine growth inhibitor or as a paracrine growth factor for tumor stromal cells.

Affinity Labels↗
PubMed1986

Direct counting of tritium by dissolving Microelisa wells in scintillation fluid.

Radioassays with low-energy beta-emitting nuclides (e.g., 3H, 14C, 35S) in 96-well plastic plates are tedious and frequently inaccurate because of the necessity of quantitatively removing and transferring the contents of each well to scintillation fluid. We therefore investigated the possibility of counting these nuclides by directly placing the entire break-apart well (Microelisa) along with the sample into one of four scintillation counting fluids: toluene-PPO-POPOP with or without Protosol, ACSR, and EcoLite. Although some of these scintillation fluids fully dissolved the plastic wells and other did not, we found that the presence of the wells did not appreciably interfere with the efficiency of tritium counting. This technique saves considerable time and reduces possible errors in liquid scintillation counting of samples from plastic microtitration plates.

Beta Particles↗
PubMed1986

Progesterone receptor assays in low-protein cytosols: a modified charcoal-gelatin procedure.

Quantitative measurement of steroid receptors including progesterone receptor (PgR) is usually accomplished by the dextran-coated charcoal (DCC) assay. At protein concentrations below about 1 mg/ml, however, serious underestimation of receptor content by DCC occurs, presumably because of adsorption of receptor to the charcoal and possibly to assay tubes, etc. We have therefore developed a modified charcoal-gelatin (MCG) procedure which largely avoids receptor losses even in samples with extremely low protein concentrations. In this MCG procedure, 0.1% gelatin is added to both sample and charcoal suspension, the charcoal content is increased to 1%, and dextran is no longer necessary. Comparison of the MCG procedure with the standard DCC and several other methods at decreasing protein concentrations shows that MCG retains acceptable efficiency for PgR at much lower protein than the others, even as low as 10 micrograms/ml. This MCG procedure will be useful in determining receptors for prognosis in very small human breast cancer biopsies, as shown here, but also for receptor determination in very small tissues such as specific brain regions, and for receptor assay during purification.

Breast Neoplasms↗
PubMed1986

Estrogen receptor in very small breast tumor specimens: a modified charcoal-gelatin assay.

We described recently a modified charcoal-gelatin (MCG) assay for measuring progesterone receptor activity in low-protein cytosols. We showed that pre-mixing of gelatin with sample cytosols (final gelatin concentration 0.1%) and removal of unbound steroid by a 1% charcoal suspension with 0.1% gelatin but without dextran preserves the progesterone receptor activity in dilute cytosol. For estrogen receptor (ER), as for progesterone receptor, the efficiency of the standard dextran-coated charcoal (DCC) assay drops rapidly as samples are diluted much below 1 mg protein per ml. We have therefore applied the MCG procedure to the assay of ER in breast tumor cytosols. We find that MCG is far more efficient for ER at low protein concentrations than either the DCC method or three other methods recommended previously for dilute samples, retaining at least 60% efficiency even at 0.01 mg protein per ml. The measured Kd of the receptor for estradiol is the same by MCG as by DCC. A series of human breast tumor biopsies assayed by MCG at 0.1 mg protein per ml gave about the same ER values (fmol/mg) as at 1 mg/ml, while the DCC efficiency for ER at the lower concentration averaged only 32%. In combination with 125I-labeled estradiol, this MCG method should allow accurate ER assays of extremely small breast cancer specimens.

Biopsy↗