Overexpression of human stanniocalcin affects growth and reproduction in transgenic mice

In mammals stanniocalcin (STC) is widely expressed, and in the kidney and gut it regulates serum calcium levels by promoting phosphate reabsorption. To shed further light on its functional significance in mammals we have created several lines of mice that express a human STC (hSTC) transgene. Three lines expressed the hSTC transgene, but only two lines exhibited high expression and contained circulating hSTC, and in these animals there was a reduction in postnatal growth (30-50%) that persisted after weaning. Moreover, even wild-type pups exhibited a growth retardation phenotype when nursed by a transgenic foster mother, and this implies that hSTC overexpression deleteriously affects maternal behavior and/or lactation. The reproductive potential of female transgenic mice was also compromised, as evidenced by significantly smaller litter sizes, but transgenic male fertility was unchanged even though the transgene was most highly expressed in testes. Interestingly, transgene-derived serum hSTC increased significantly after puberty and was severalfold higher in females than in males, suggesting a gender-specific mechanism for maintaining elevated circulating levels of STC. Blood analysis revealed that both transgenic lines had elevated phosphate and decreased alkaline phosphatase levels, indicative of altered kidney and bone metabolism. These studies provide the first evidence that STC is involved in growth and reproduction and reaffirm its role in mineral homeostasis.     

Renal activation of extracellular signal-regulated kinase in rats with autosomal-dominant polycystic kidney disease

BACKGROUND: Abnormal proliferation of renal tubule epithelial cells is a central factor in the biogenesis and sustained expansion of cysts in autosomal-dominant polycystic kidney disease (ADPKD). Recent evidence from in vitro studies of human cyst wall epithelial cells has implicated a role for the mitogen-activated protein (MAP) kinase pathway in this aberrant proliferation. To determine the extent to which this signaling pathway is involved in cyst pathogenesis in vivo, we measured the expression of select components of the MAP kinase cascade in Han:SPRD rats with ADPKD at an early stage of the disease. METHODS: Kidneys of 8-week-old normal Han:SPRD rats (+/+) or rats heterozygous (Cy/+) for ADPKD were examined by Western blot analysis and immunohistochemistry to determine the expression of extracellular-regulated kinase (ERK), phosphorylated ERK (P-ERK), Raf-1 (MAPKKK), phosphorylated Raf-1 (P-Raf-1), B-Raf, Rap-1 and phosphorylated protein kinase A (P-PKA). RESULTS: P-ERK was expressed to a greater extent in Cy/+ kidneys (3.74 +/- 1.07 fold) than in normal kidneys, whereas ERK abundance was not different. P-Raf-1 levels were higher in Cy/+ than in +/+ kidneys (1.53 +/- 0.08 fold) consistent with upstream stimulation of receptor tyrosine kinase. B-Raf and Raf-1 abundances were greater in Cy/+ than in +/+ (1.74 +/- 0.25 and 1.27 +/- 0.08 fold, respectively). In Cy/+, immunohistochemistry showed increased P-ERK and B-Raf expression in the abnormal mural epithelial cells within cysts. These findings, together with the detection of P-PKA and the small G protein, Rap-1, in cyst epithelial cells, implicate a potential role for cyclic adenosine monophosphate (AMP) in the activation of ERK in ADPKD cells. CONCLUSIONS: We conclude that the MAP kinase pathway is activated to the level of ERK in the abnormal mural epithelial cells lining cysts in animals with a dominantly inherited type of polycystic kidney disease. We suggest that cAMP, acting through PKA, Rap-1 and B-Raf, may contribute to the activation of ERK in a way that complements receptor tyrosine kinase-mediated agonists in the promotion of cyst enlargement.     

Chemoprevention of prostate cancer. Focus on key opportunities and clinical trials

By 2004-2005, the final results of the Prostate Cancer Prevention Trial should be available. Within several years thereafter, results of the SELECT should be available. The growing list of potential agents for prostate cancer prevention continues to grow and includes COX-2 inhibitors, vitamin D, dietary interventions (soy, isoflavenoids, low-fat diet), and many others. As prospective trials are completed and molecular genetic correlations are developed, it is almost certain that specific recommendations, tailored to the individual patient, will be developed. Ultimately, through these efforts, it can be anticipated that the primary focus for control of prostate cancer will shift from early detection and treatment to prevention.     

Vitamin C improves resistance but not conduit artery endothelial function in patients with chronic renal failure

BACKGROUND: Chronic renal failure is associated with impaired endothelium-dependent vasodilation and accelerated atherogenesis. To examine whether endogenous reactive oxygen species (ROS) modify endothelial function in renal failure, we evaluated the effect of the antioxidant vitamin C on endothelium-dependent responses in both the conduit and resistance vasculature of subjects with severe renal impairment. METHODS: Endothelial function of the forearm resistance vasculature was assessed using plethysmography to measure the dilator response to intra-arterial acetylcholine (Ach) (25 to 100 nmol/min). Endothelial function of radial and brachial arteries was assessed using vascular ultrasound to measure the dilator response to flow during reactive hyperemia [flow-mediated dilatation (FMD)]. Studies were performed before and after administration of vitamin C by intra-arterial infusion (25 mg/min) in 33 predialysis patients or by intravenous infusion (3 g) in 17 hemodialysis patients. RESULTS: Parenteral administration of vitamin C resulted in a 100-fold increase (intra-arterial studies) and a 4.5-fold increase (intravenous studies) in serum antioxidant activity. Vitamin C administration increased the dilator response to ACh in resistance vessels (P = 0.01), but did not alter the dilator response to flow in conduit vessels of either dialysis (P = 0.3) or predialysis subjects (P = 0.8). In the presence of the nitric oxide (NO) synthase inhibitor NGmonomethyl-L-arginine (L-NMMA), there was no effect of vitamin C on resistance vessel endothelial function. In all cases the dilator response to the endothelium-independent dilators was unaffected by vitamin C. CONCLUSION: Acute administration of vitamin C reduces oxidant stress in renal failure and improves NO-mediated resistance vessel dilatation.     

Multiple measures of carcinoma extent versus perineural invasion in prostate needle biopsy tissue in prediction of pathologic stage in a screening population

The capacity of perineural invasion by carcinoma in prostate needle biopsy tissue to independently predict pathologic stage in radical prostatectomy tissues remains uncertain. We sought to determine, in a prostate specific antigen-based screening population, the ability of needle biopsy histologic grade, tumor extent, and perineural invasion to independently predict pathologic stage and margin status in the whole prostate gland. Perineural invasion, Gleason grade, percentage Gleason pattern 4/5 carcinoma, and multiple measures of needle biopsy tumor extent, including number of positive cores, percentage of positive cores, total percentage of carcinoma, greatest percentage of carcinoma in a single core, and total carcinoma length in millimeters, were captured for 215 men from a prostate specific antigen-based screening program diagnosed with prostate cancer in a median of six procured needle biopsy cores. Pathologic stage and surgical margin status were evaluated in corresponding completely embedded radical prostatectomy specimens. A logistic regression model was used to relate the endpoints of extraprostatic extension by carcinoma and/or positive margins to needle biopsy tissue findings. In univariate analyses, total percentage of carcinoma (p = 0.003), greatest percentage of carcinoma in a single core (p = 0.004), total tumor length in millimeters (p = 0.009), and fraction of positive cores (p = 0.02) were all significantly associated with extraprostatic (pT3) carcinoma, whereas all five measures of carcinoma extent in needle biopsy tissue were related to positive margins. Correlation coefficient determinations showed that all five measures of needle biopsy carcinoma extent were highly interrelated. In multivariate analyses, total percentage of carcinoma was significantly related to pathologic T stage (p = 0.003) and positive margins (p = 0.0002). In a multivariate model with the radical prostatectomy whole gland endpoint of either pT3 disease or positive margins, fraction of positive cores (p = 0.00001) was the only variable with significant predictive value. Perineural invasion by carcinoma in needle biopsy tissue was detected in 11% of cases. Neither presence nor absence of perineural carcinoma nor number nor percentage of positive nerves related to pathologic stage in univariate or multivariate analyses. Amount of carcinoma in prostate needle biopsy tissue, using multiple measurements but not perineural invasion, is a significant histologic attribute predictive of pathologic stage and margin status for men with prostate specific antigen screening detected prostatic carcinoma. Reporting of several measures of carcinoma extent in needle biopsy tissue is recommended.