Chemopreventive effects of the aromatase inhibitor vorozole (R 83842) in the methylnitrosourea-induced mammary cancer model

The chemopreventive activity of the highly specific nonsteroidal aromatase inhibitor, vorozole, was examined in the methylnitrosourea (MNU)-induced rat model of mammary carcinogenesis. Various doses of vorozole (0.08-1.25 mg/kg body wt/day) were administered daily (by gavage) to female Sprague-Dawley rats starting at 43 days of age. Seven days later, the rats were given a single i.v. dose of MNU (50 mg/kg body wt). Rats were continually treated with vorozole until the end of the experiment (120 days post-MNU). Vorozole caused a dose dependent inhibition of mammary cancer multiplicity. The highest dose of vorozole (1.25 mg/kg body wt/day) decreased cancer multiplicity by approximately 90%, and simultaneously decreased cancer incidence from 100 to 44%. The next two highest doses of vorozole (0.63 and 0.31 mg/kg body wt/day) inhibited MNU-induced mammary cancer multiplicity by 70-80%. Even the two lowest doses of vorozole (0.16 and 0.08 mg/kg body wt/ day) decreased cancer multiplicity -50%. Serum level determinations were performed on a variety of endpoints at either 4 or 24 h following the last dose of vorozole. Insulin-like growth factor (IGF)-1 levels were slightly, but significantly, increased by vorozole treatment. Vorozole induced striking increases in serum testosterone levels at 4 h at all the dose levels employed. Testosterone levels were significantly elevated over controls at 24 h in rats given the lower doses of vorozole (0.08-0.31 mg/kg body wt/day), but were significantly lower than in rats administered the higher doses of vorozole (0.63 or 1.25 mg/kg body wt/ day). This result presumably reflects the limited half- life of vorozole in rats. In a second series of experiments, the effects of limited duration of dosing with vorozole (2.5 mg/kg body wt/day) or intermittent dosing with vorozole were determined. Treatment of rats with vorozole for limited time periods, from 3 days post-MNU administration until 30 or 60 days post-MNU treatment, resulted in significant delays in the time to appearance of palpable cancers. However, these limited treatments did not greatly affect the overall incidence or multiplicity of mammary cancers when compared with the MNU controls at the end of the study (150 days post-MNU). Finally, the effects of intermittent dosing with vorozole (2.5 mg/kg body wt/day) were examined. Rats were administered cycles of vorozole daily for a period of 3 weeks followed by treatment with the vorozole vehicle for the next 3 weeks (total of four cycles). Although this intermittent treatment did inhibit the appearance of new tumors during each of the periods that vorozole was administered, it did not cause regression of palpable cancers.      

Ataxia telangiectasia mutated is essential during adult neurogenesis

Ataxia telangiectasia (A-T) is an autosomal recessive disease characterized by normal brain development followed by progressive neurodegeneration. The gene mutated in A-T (ATM) is a serine protein kinase implicated in cell cycle regulation and DNA repair. The role of ATM in the brain and the consequences of its loss on neuronal survival remain unclear. We studied the role of ATM in adult neural progenitor cells in vivo and in vitro to define the role of ATM in dividing and postmitotic neural cells from Atm-deficient (Atm(-/-)) mice in a physiologic context. We demonstrate that ATM is an abundant protein in dividing neural progenitor cells but is markedly down-regulated as cells differentiate. In the absence of ATM, neural progenitor cells of the dentate gyrus show abnormally high rates of proliferation and genomic instability. Atm(-/-) cells in vivo, and in cell culture, show a blunted response to environmental stimuli that promote neural progenitor cell proliferation, survival, and differentiation along a neuronal lineage. This study defines a role for ATM during the process of neurogenesis, demonstrates that ATM is required for normal cell fate determination and neuronal survival both in vitro and in vivo, and points to a mechanism for neuronal cell loss in progressive neurodegenerative diseases.     

The influence of dietary sodium restriction on renal and ovarian renin and prorenin production during ovarian stimulation

In a prospective study, the effect of dietary sodium restrictionon plasma and follicular fluid renin and prorenin concentrationsand on fertilization measures was investigated during ovarianstimulation. In all, 18 women undergoing ovarian stimulationfor in-vitro fertilization and embryo transfer were randomlydivided into groups with and without sodium restriction. Plasmarenin and prorenin concentrations were higher in the low sodiumthan in the normal sodium group. Plasma renin concentrationsshowed a mid-luteal rise. Plasma prorenin concentrations increased4-fold on the day of oocyte retrieval, followed by a gradualdecline to basal values. The low sodium group had more folliclesthan the normal sodium group. Neither follicular fluid reninand prorenin concentrations, nor the total amount of follicularfluid renin and prorenin per ovary differed significantly betweenthe two groups. Oocyte yield and fertilization rates were similarin both groups. These rates were correlated with neither reninnor prorenin concentrations in follicular fluid. We concludethat sodium restriction did not influence cyclic plasma variationsof renin or prorenin or follicular fluid renin and proreninconcentrations. In addition, fertilization rates were not affectedby sodium restriction.     

Gonadotrophin heterogeneity and biopotency: implications for assisted reproduction

The extensive heterogeneity of the gonadotrophin hormones, follicle stimulating hormone (FSH) and luteinizing hormone (LH), is due primarily to the heterogeneous nature of their carbohydrate side- chains, in particular sialic acid residues. In this review, we discuss the role of carbohydrate chains in receptor binding and activation, biological activity, and metabolic half-life. The synthesis and secretion of the various glycoforms of both FSH and LH appear to be under endocrine control with gonadotrophin-releasing hormone (GnRH), oestradiol and testosterone playing important roles. Evidence for different glycoforms having variable biopotency or different encoded functions is increasing, and the production and secretion of more or less acidic gonadotrophin species in different physiological states may represent an important mechanism whereby the pituitary regulates gonadal cell and organ function. This has potential importance for the development of new pharmaceutical reagents and new therapeutic regimens in assisted reproduction. It is envisaged that the use of existing and new forms of FSH/LH will allow patients to be treated in a more controlled and physiological manner, with treatment regimens individualized to the needs of the patient.      

p14ARF expression in invasive breast cancers and ductal carcinoma in situ – relationships to p53 and Hdm2

Introduction  

p14^ARF stabilises nuclear p53, with a variable expression of p14^ARF mRNA in breast cancers. In vitro, nuclear p14^ARF binds Hdm2 to block Hdm2-dependent nucleocytoplasmic shuttling of p53, which is required before cytoplasmic degradation of p53. p14^ARF is negatively regulated by p53 and through p53-independent pathways. No studies have yet examined levels of p14^ARF protein expression in breast cancer and their relationship to Hdm2/p53 immunoreactivity or subcellular localisation. Previously, immunohistochemical expression of cytoplasmic p14^ARF, p53 and Hdm2 has been described. HER-2 (c-erbB2/neu) predicts prognosis and interacts with the p14^ARF/Hdm2 pathway to inactivate p14^ARF and to influence Hdm2 activity and localisation. This study examined p14^ARF and p53/Hdm2 expression and subcellular localisation by using immunohistochemistry in a series of invasive ductal breast cancers (IDCs) with concomitant ductal carcinoma in situ (DCIS), to evaluate whether findings in vitro were related to clinicopathological parameters such as HER-2 and their effect on patient outcome.     

The transcription factors hypoxia‐inducible factor 1α and Ets‐1 colocalize in the hypoxic synovium of inflamed joints in adjuvant‐induced arthritis

Objective

To determine the relationship between hypoxia and the expression of Ets‐1 and hypoxia‐inducible factor 1α (HIF‐1α) in both normal and inflamed joints. Adjuvant‐induced arthritis (AIA) was used as the model system, since it mirrors many aspects of the pathology of rheumatoid arthritis.

Methods

Adjuvant arthritis was induced in a group of 10 female Lewis rats. A second group of 10 uninjected female Lewis rats served as naive controls. When a maximum clinical joint score was achieved in the AIA group, all 20 rats were injected with the specific hypoxic cell marker Hypoxyprobe‐1 and subsequently killed. Hypoxyprobe‐1 adducts, Ets‐1, and HIF‐1α were localized in the joints of the hind feet from these groups using immunohistochemistry.

Results

Compared with the joints from control rats, inflamed joints contained markedly more cells with Hypoxyprobe‐1 adduct immunoreactivity, Ets‐1–immunoreactive nuclei, and nuclear immunoreactivity for both Ets‐1 and HIF‐1α.

Conclusion

Our results demonstrate the presence of hypoxia in inflamed joints in this experimental model of arthritis. The colocalization of Ets‐1 and HIF‐1α in these hypoxic areas suggests that hypoxia may induce Ets‐1 and HIF‐1α expression during joint inflammation.