Aromatase and its inhibitors

Inhibitors of aromatase (estrogen synthetase) have been developed as treatment for postmenopausal breast cancer. Both steroidal substrate analogs, type I inhibitors, which inactivate the enzyme and non-steroidal competitive reversible, type II inhibitors, are now available. 4-hydroxyandrostenedione (4-OHA), the first selective aromatase inhibitor, has been shown to reduce serum estrogen concentrations and cause complete and partial responses in approximately 25% of patients with hormone responsive disease who have relapsed from previous endocrine treatment. Letrozole (CGS 20, 269) and anastrozole (ZN 1033) have been recently approved for treatment. Both suppress serum estrogen levels to the limit of assay detection. Letrozole has been shown to be significantly superior to megace in overall response rates and time to treatment failure, whereas anastrozole was found to improve survival in comparison to megace. Both were better tolerated than the latter. The potential of aromatase within the breast as a significant source of estrogen mediating tumor proliferation and which might determine the outcome of inhibitor treatment was explored. Using immunocytochemistry and in situ hybridization, aromatase and mRNAarom was detected mainly in the epithelial cells of the terminal ductal lobular units (TDLU) of the normal breast and also in breast tumor epithelial cells as well as some stromal cells. Increase in proliferation, measured by increased thymidine incorporation into DNA and by PCNA immunostaining in response to testosterone was observed in histocultures of breast cancer samples. This effect could be inhibited by 4-OHA and implies that intratumoral aromatase has functional significance. An intratumoral aromatase model in the ovariectomized nude mouse was developed which simulated the hormone responsive postmenopausal breast cancer patient. This model also allows evaluation of the efficacy of aromatase inhibitors and antiestrogens in tumors of estrogen receptor positive, human breast carcinoma cells transfected with the human aromatase gene. Thus, the cells synthesized estrogen which stimulated tumor formation. Both aromatase inhibitors and antiestrogens were effective in suppressing tumor growth in this model. However, letrozole was more effective than tamoxifen. When the aromatase inhibitors were combined with tamoxifen, tumor growth was suppressed to about the same extent as with the aromatase inhibitors alone. Thus, there was no additive or synergistic effects of combining tamoxifen with aromatase inhibitors. This suggests that sequential treatment with these agents is likely to be more beneficial to the patient in terms of longer response to treatment.

An in vitro comparison of thermoplasticised gutta-percha obturation techniques with cold lateral condensation

This study compared the apical sealing ability, obturation time and extrusion of gutta-percha and sealer when root canals were obturated using either cold lateral condensation or one of the three methods using thermoplasticised gutta-percha (Alpha Seal, Thermafil or JS Quick Fill) in vitro. One hundred and thirty-one root canals from 78 extracted human teeth were used; 116 canals were divided into five groups so that they were balanced with respect to prepared canal anatomy, and the remaining 15 canals were used as positive and negative controls. The canals in the first four groups were prepared with hand files using the step-down technique to a standard apical size and flare. The last group was prepared using engine-driven rotary nickel-titanium files (McSpadden) to a similar apical size and flare. One of the four obturating techniques was used to fill the canals in each of the first four groups. The fifth group was obturated using the Alpha Seal technique. The roots were immersed in india ink, demineralised and rendered transparent to assess the extent of maximum lincar dye penetration. The Alpha Seal groups had the highest number of specimens without any leakage. There was a significant difference in the proportions of specimens that did not leak when the Alpha Seal (P < 0.01) and cold lateral condensation groups (P < 0.05) were compared with JS Quick Fill. Cold lateral condensation had a higher proportion of specimens with leakage in canals with curvature greater than 20 degrees than in canals with curvatures less than 20 degrees (P < 0.05). The curvature of canals had no effect on the sealing ability of the other techniques. The method of canal preparation had no effect on the sealing ability of Alpha Seal. Alpha Seal, Thermafil and JS Quick Fill were significantly quicker to perform than cold lateral condensation.

Aromatase expression in the human breast

The plasma levels of free estradiol are very low in postmenopausal women. However, concentrations of estrogens within breast tissue have been reported to be higher than in plasma and similar to plasma concentrations in premenopausal women. One mechanism by which this may occur is for breast cells to synthesize estrogens themselves and produce high concentrations locally. Thus, tumor aromatase may be a significant source of estrogen which stimulates tumor growth. To address the question of the importance of this pathway, we have investigated the expression of aromatase within the normal breast and breast cancers. Because conventional biochemical assays for measuring aromatase activity require relatively large amounts of tissue, we developed an immunocytochemical method using a monoclonal antibody to determine the expression of aromatase. The method can be applied to sections of tumors embedded in paraffin blocks as routinely prepared for pathology. Since we have previously shown that mRNA for aromatase (P450 arom) and the protein are expressed in the same cells of the human placenta, we used in situ hybridization of sequence specific probes to P450 arom mRNA in breast tissue as one method to verify the specificity of the immunocytochemical detection of the enzyme. Both immunocytochemistry and in situ hybridization identified aromatase enzyme and mRNA expression in the epithelial cells of the terminal ductal lobula units (TDLU) and surrounding stromal cells of the normal human breast, and in the tumor epithelial cells and stromal cells of breast cancers. In addition, evidence for the functional significance of tumor aromatase was indicated by a correlation between aromatase activity and expression of proliferating cell nuclear antigen (PCNA) in the tumor, and by increased thymidine incorporation into DNA in response to testosterone in tumors in histoculture which had high aromatase activity but not in those with low activity. The findings suggests that estrogen produced locally is important in enhancing proliferation of the tumor.

The effects of aromatase inhibitors and antiestrogens in the nude mouse model

The effects of antiestrogens, tamoxifen and ICI 182,780, and aromatase inhibitors, arimidex (anastrozole ZD1033) and letrozole (CGS 20,267), on the growth of tumors were studied in nude mice. In this model, estrogen dependent MCF-7 human breast cancer cells stably transfected with the aromatase gene were inoculated in four sites per mouse. Sufficient estrogen is produced from aromatization of androstenedione supplement (0.1 mg/mouse/day) by the cells to stimulate their proliferation, tumor formation, and maintain the uterus similar to that of the intact mouse. Once the tumors reached a measurable size, the mice were injected with antiestrogen or inhibitor for 35-56 days. Tumor volumes were measured weekly. At autopsy, the tumors were removed, cleaned, and weighed. Statistical data was determined from tumor weights. Both antiestrogens were effective in reducing tumor growth in these mice. Tamoxifen appears to be more effective than ICI 182,780, although the former stimulated the uterine weight whereas the pure antiestrogen did not. However, both aromatase inhibitors were more effective than the antiestrogens. Tumor regression was observed with letrozole. Thus, after-treatment tumor weights were less than those of a group of mice at the start of treatment. The aromatase inhibitors also reduced the weight of the uterus, suggesting that these compounds, as well as the pure antiestrogen, may not cause endometrial proliferation, unlike tamoxifen. These aromatase inhibitors may not only benefit patients who have relapsed from tamoxifen, but may be more effective in patients as first line agents for suppressing the effects of estrogen.

Preclinical studies using the intratumoral aromatase model for postmenopausal breast cancer

To determine the most effective strategies for the treatment of postmenopausal hormone dependent breast cancer, we recently developed a model system in nude mice. In this model, estrogen receptor-positive human breast cancer cells (MCF-7) stably transfected with the aromatase gene are inoculated into ovariectomized, immunosuppressed (nude) mice. These cells synthesize sufficient estrogen from androgen substrate to stimulate their proliferation and the development of tumors. Moreover, estrogen secreted by the tumor cells maintains uterine weight comparable to that of the intact mouse. In the present study, we employed this model to investigate the effects of the aromatase inhibitor, letrozole (CGS 20267 [Femara]) on mammary tumor growth and on the uterus. We also used this model to predict the effects of combining two aromatase inhibitors, letrozole and anastrozole (Arimidex), with the antiestrogen tamoxifen (Nolvadex). Letrozole was found to be a highly potent inhibitor of tumor proliferation and more effective than tamoxifen. No stimulation of uterine growth was observed with the aromatase inhibitors. However, the combination of letrozole or anastrozole and tamoxifen was no more effective than either aromatase inhibitor alone. The agonistic effect of tamoxifen on the uterus was observed when it was given alone and when combined with the aromatase inhibitors. Furthermore, letrozole had the most potent antitumor activity when compared to other aromatase inhibitors and antiestrogens. No additional benefit was observed by combining these agents with tamoxifen over treatment with aromatase inhibitors alone.

Erbium:YAG laser-assisted cataract surgery

BACKGROUND AND OBJECTIVE

To assess the safety and efficacy of erbium:YAG laser-assisted cataract removal.

PATIENTS AND METHODS

A total of 15 patients underwent cataractous lens removal. All the patients had a visual acuity of 20/50 or worse secondary to senile cataract. The endothelial cell count was calculated preoperatively and at 6 weeks postoperatively. A 2.94-micron-wavelength erbium: YAG laser with a zirconium-fluoride fiber optic and silica tip was used to fracture and emulsify the nucleus. The erbium:YAG laser was chosen due to its high absorption in water, a primary component of a cataractous lens.

RESULTS

The postoperative visual acuity was 20/30 or better in all the eyes that were treated with surgery. The endothelial cell loss at 3 months was 0% to 10%. No laser-related complications were noted. A conversion to an ultrasound surgical technique was utilized in six cases. Vitreous loss occurred in one case due to the posterior extension of an anterior capsulotomy tear.

CONCLUSION

This study demonstrated the ability of an erbium:YAG laser system to safely and effectively emulsify the lens nucleus. Laser-assisted cataract surgery is a promising new clinical procedure.

Acute hospital admission systems: problems experienced by general practitioners

This study was undertaken to examine the existing system of access for general practitioners in arranging acute admissions to three general hospitals in the Southern Health Board (SHB) area. One hundred and twenty eight patients were admitted to the three hospitals over a one week period. General practitioners were surveyed on the process of admission for each patient. Response rate was 118/128 (92.2%). Hospital A had 53 admissions, Hospital B had 41 admissions and Hospital C had 24 admissions. In total, 30/118 (25.4%) admissions took over one hour to arrange, of these 23 (76.7%) were admitted to Hospital A, 4 (13.3%) were admitted to Hospital B and 3 (10.0%) were admitted to Hospital C. The admission sister was responsible for confirming the route of admission in 102 (86.4%) of cases. In Hospital A, 23/53 (43.4%) patients were referred to Accident and Emergency (A&E) for assessment prior to admission, 4/41 (9.8%) were referred in Hospital B, and 2/24 (8.3%) in Hospital C. In the light of current findings, possible alternatives to the current acute admissions system are discussed.

The science of prevention. A conceptual framework and some directions for a national research program

A conceptual framework for studying the prevention of human dysfunction is offered. On the basis of recent advances in research on the development of psychological disorders and methods of preventive intervention, generalizations about the relation of risk and protective factors to disorder are put forward, along with a set of principles for what may be identified as the science of prevention. Emerging themes from the study of human development, in general, need to be incorporated in the models for explaining and preventing serious problems of human adaptation. The article concludes with a set of recommendations for a national prevention research agenda.

The science of prevention. A conceptual framework and some directions for a national research program

A conceptual framework for studying the prevention of human dysfunction is offered. On the basis of recent advances in research on the development of psychological disorders and methods of preventive intervention, generalizations about the relation of risk and protective factors to disorder are put forward, along with a set of principles for what may be identified as the science of prevention. Emerging themes from the study of human development, in general, need to be incorporated in the models for explaining and preventing serious problems of human adaptation. The article concludes with a set of recommendations for a national prevention research agenda.

Genes for interleukin 7 are transcribed in leukemic cell subsets of individuals with chronic lymphocytic leukemia

Regulation of expression of interleukin 7 (IL-7) mRNA is aberrant in the leukemic subset of cells of chronic lymphocytic leukemia (CLL) patients. The entire coding sequence for IL-7 as well as an alternatively spliced IL-7 mRNA are transcribed in these leukemic cells. No IL-7 mRNA expression is detected in fresh peripheral blood mononuclear cells from normal individuals. Furthermore, the "normal" nonleukemic subsets of cells isolated from the same CLL patients also do not express IL-7 mRNA. The only subset of cells in which IL-7 mRNA is detected is the one that contains the leukemic cells themselves. The polymerase chain reaction was used to examine cytokine expression, and flow cytometry was used to purify the various subsets of peripheral blood mononuclear cells examined in these studies, as well as to examine IL-7 receptor expression. A proportion of the cells from the CLL patients express receptors that are capable of binding IL-7, whereas T cell-depleted normal cell preparations do not express receptors for IL-7 that are detectable with IL-7 fluorokines. The IL-7 receptor-bearing cells in CLL patients include a portion of leukemic cells and a fraction of the T cells, as well as some non-T, non-B cells. These findings suggest that IL-7 and IL-7 receptor expression in CLL may be relevant not only to growth regulation of the leukemic cells but to the immunological abnormalities that occur in the disease as well, possibly via the induction of inappropriate immune activity of IL-7 receptor-bearing cells.

Phosphor plate computed radiography: response to variation in mAs at fixed kVp in an animal model. Potential role in neonatal imaging

Computed digital radiography offers a number of potential advantages over conventional film-screen imaging. To determine the applicability of these to portable neonatal examinations we performed a controlled prospective study comparing conventional 200 speed film-screen with a computed radiography unit in an animal model. Images acceptable for diagnostic purposes were obtained on the digital system over an exposure range many orders of magnitude greater than was possible on the film-screen system. Digital imaging offers potential for elimination of repeat examinations due to suboptimal exposure factors, and for reduction in radiation dose to the patient. We believe that computed digital radiography should be particularly suited to portable neonatal imaging.

Changes in epidermal growth factor receptor expression and response to ligand associated with acquired tamoxifen resistance or oestrogen independence in the ZR-75-1 human breast cancer cell line

We have examined the expression of receptors for epidermal growth factor (EGFR) by the ZR-75-1 human breast cancer cell line and tamoxifen resistant (ZR-75-9al 8 microM) and oestrogen independent/tamoxifen sensitive (ZR-PR-LT) variants. The parent line expressed a single class of high affinity binding sites (4,340 +/- 460 receptors/cell; Kd 0.23 +/- 0.04 nM). ZR-75-9al 8 microM cells, routinely maintained in medium containing 8 microM tamoxifen, were negative for oestrogen receptor (ER) and progesterone receptor (PGR) and expressed a markedly increased number of EGFR (14,723 +/- 2116 receptors/cell). Receptor affinity was unchanged. Time dependent reversal of the tamoxifen resistant phenotype was accompanied by a return to ER and PGR positivity and a fall in EGFR numbers to parent cell levels. In contrast ZR-PR-LT cells had a greatly reduced EGFR content (803 +/- 161 receptors/cell) accompanying elevated PGR numbers. Pre-treatment of these cells with suramin or mild acid stripping failed to expose receptors which may have been occupied by endogenously produced ligand. Increased proliferation of ZR-75-1 cells treated with EGFR (0.01-10 ng ml-1) was only observed in serum-free medium lacking insulin and oestradiol. Under these conditions untreated cells failed to proliferate. Both variant lines continued to proliferate in serum free medium in the absence or presence of insulin and oestradiol but failed to respond to exogenous EGF.

Comparison of computerized digital and film-screen radiography: response to variation in imaging kVp

A controlled prospective study, in an animal model chosen to simulate portable neonatal radiography, was performed to compare the response of the Philips Computed Radiography (CR) system and conventional 200 speed film-screen (FS) to variation in imaging kVp. Acceptable images were obtained on the CR system over a very wide kVp range. In contrast the FS system produced acceptable images over a narrow kVp range. This ability suggests that the CR system should eliminate the need for repeat examinations in cases where a suboptimal kVp setting would have resulted in an unacceptable FS image. CR technology should therefore be ideally suited to portable radiography especially in situations where selection of correct exposure factors is difficult as in the neonatal nursery.

Digital imaging with a photostimulable phosphor in the chest of newborns

To evaluate use of a digital photostimulable phosphor imaging system in the neonatal nursery, 150 newborns were divided into three groups of 50. In the first two groups, screen-film and computed radiographs of the chest were obtained at the same radiation exposure; in the third group, computed radiographs were obtained with a 50% dose reduction (half-exposure computed radiographs). All images were blindly evaluated by three readers who scored the quality of visualization of the mediastinum, lung, bone, soft tissues, and endotracheal and nasogastric tubes, and also image density. No statistical differences in visualization of tubes existed among the three groups. Visualization of the mediastinum, lung, bones, and soft tissues was statistically significantly better on computed radiographs than on half-exposure computed radiographs; visualization of the lungs, bones, and soft tissues was statistically significantly better on screen-film radiographs than half-exposure computed radiographs. Image density was statistically better on computed and half-exposure computed radiographs than on screen-film radiographs.

Percutaneous feeding tube method for use in children

Surgical gastrostomy has been a widely accepted method for introducing a percutaneous feeding tube for many years. However, complications are frequent, and many children who need them are not good surgical candidates. This study examines imaging guided percutaneous placement of feeding gastrostomy catheters as a safe and effective alternative to surgery.

Digital imaging of the newborn chest

The study reports initial experience on utilising an area plate digital imaging system to obtain portable radiographic images on newborn infants. Initial results suggest that the system is a practical alternative to conventional portable radiography with potential advantages of decreasing the number of retake films and also of decreasing radiation dose.

Heterogeneity of human colon carcinoma

In order to better understand colon cancer, a model system reflecting the heterogenous nature of this disease was developed and used in the development of new cytotoxic and non-cytotoxic therapeutic approaches. A large bank of colon carcinoma cell lines was established from primary human colon carcinomas and grouped based on their tumorigenicity in athymic mice, their growth rates in soft agarose and in tissue culture, and their secreted levels of carcinoembryonic antigen. These cell lines were later characterized based on cell surface proteins and antigens detected with antisera raised against a differentiated colon carcinoma cell line. Although these biochemical markers correlated with the biological classification of these cell lines, there was still extensive heterogeneity within each group in all properties examined. This colon carcinoma cell system was used to study natural vs. selected resistance to the anticancer drug mitomycin C (MMC). The differing IC50 values in vitro were reflected in the inhibition by MMC of xenograft growth in athymic mice. A new, more readily bioactivatable analogue of MMC was tried and shown to be more active in vitro and in vivo, suggesting that rapid efflux of the drug before activation may be important in examining causes of resistance to MMC. Another approach to the treatment of colon cancer is the use of non-cytotoxic agents such as growth factors and differentiation agents to restore normal growth to the malignant cells. We have isolated and characterized two types of polypeptides from colon carcinoma cells and conditioned medium from these cells. The first, transforming growth factors (TGF's) confer a transformed phenotype on non-transformed fibroblasts while the second, tumor inhibitory factors (TIF's), inhibits the anchorage independent growth of transformed cells. The fact that extracts of colon carcinoma cells contain both activities suggests that the heterogeneity of the cell lines could be due to different levels of TGF's and TIF's produced. The effectiveness of differentiation agents to restore normal growth control using a transformed mouse embryo cell line was examined. Treatment of these cells with differentiation agents restored normal growth control to these cells. An increased synthesis of TGF's resulted from these treatments. Therefore, differentiation agents may be useful in non-cytotoxic treatment. The use of this model system for human colon carcinoma will hopefully lead to more effective drugs for the treatment of colon cancer in man.