Analgesic use and sex steroid hormone concentrations in postmenopausal women

Prior epidemiologic studies suggest that regular use of analgesics may decrease risk of breast and ovarian cancer. We explored possible hormone-mediated mechanisms for these associations by examining the relationship between use of aspirin, nonaspirin nonsteroidal anti-inflammatory drugs (NSAID), and acetaminophen and sex steroid hormone concentrations among 740 postmenopausal women in the Nurses' Health Study. All women reported their analgesic use in 1988 or 1990 and provided a blood sample in 1989 to 1990. We calculated adjusted geometric mean estrogen and androgen levels for each category of analgesic use and calculated the P value for trend with increasing frequency of use. There was no association between days of use per month of aspirin, nonaspirin NSAIDs, or acetaminophen in 1990 and hormone levels (all P(trend) > or = 0.09). However, we observed significant inverse trends between the estimated number of aspirin tablets per month in 1988 and concentrations of estrone (P(trend) = 0.04) and estrone sulfate (P(trend) = 0.03). In analyses of total (aspirin and nonaspirin) NSAID use in 1990, women who used NSAIDs at least 15 days per month had significantly lower levels of estradiol compared with women with no NSAID use (P(trend) = 0.03). Frequency of use of all analgesics (aspirin, nonaspirin NSAIDs, and acetaminophen) in 1990 was inversely associated with concentrations of estradiol (P(trend) = 0.001), free estradiol (P(trend) = 0.01), estrone sulfate (P(trend) = 0.03), and the ratio of estradiol to testosterone (P(trend) = 0.04). Among postmenopausal women, regular users of aspirin and other analgesics may have lower estrogen levels than nonusers, which could contribute to a decreased risk of breast or ovarian cancer among analgesic users.

ABO blood group and incidence of epithelial ovarian cancer

Previous studies have observed an association between ABO blood group and risk of certain malignancies, including ovarian cancer; however, no prospective studies of the association with ovarian cancer risk are available. Using data from 49,153 women in the Nurses' Health Study, we examined the association between ABO blood group and incidence of epithelial ovarian cancer. Study participants reported their blood type and Rh factor in 1996, and 234 women were diagnosed with incident ovarian cancer during 10 years of follow-up. We used Cox proportional hazards regression to model the incidence rate ratios (RR) and 95% confidence intervals (CI) of ovarian cancer for each blood group category. Compared to women with blood group O, women with blood group AB or B had a nonsignificant 38% increase in ovarian cancer incidence (95% CI = 0.88-2.16 for blood group AB and 0.96-1.99 for blood group B), whereas blood group A was not associated with risk (RR = 0.95, 95% CI = 0.70-1.30). Combining blood groups AB and B, we observed a statistically significant positive association with presence versus absence of the B antigen overall (RR = 1.41, 95% CI = 1.06-1.88) and for the serous invasive subtype (RR = 1.53, 95% CI = 1.08-2.17). In this large, prospective cohort of women, presence of the B antigen was positively associated with ovarian cancer incidence, whereas blood group A was not associated with risk. Additional studies are needed to confirm this association and to explore the mechanisms through which blood group may influence ovarian cancer risk.

Abstract A126: Risk factors for epithelial ovarian cancer by tumor dominance, a surrogate for cell of origin

Ovarian tumors traditionally are thought to arise from the ovarian surface epithelium (OSE); however recent studies suggest that some tumors may originate in the distal fallopian tube. Differences in the risk factors for tumors of ovarian versus tubal origin may help to explain inconsistent associations observed across studies for some exposures. To determine cell of origin in cancer resections, it is necessary to conduct detailed sectioning of fallopian tubes and ovaries, which is impractical in large epidemiologic studies. However a prior study suggested that tumor dominance, determined from pathology reports, may be an acceptable surrogate for cell of origin, such that tumors arising in the OSE are more likely to involve only one ovary or to show one involved ovary exceeding the other in dimension by more than two-fold (DOM+), while tumors of tubal origin show symmetric ovarian involvement or an even distribution across the peritoneal cavity (DOM−). Therefore, to explore risk factor associations by cell of origin, we prospectively investigated the relationship of both reproductive/hormonal and non-reproductive exposures with risk of DOM+ versus DOM− tumors among 403 incident invasive cases of confirmed epithelial ovarian cancer from the Nurses' Health Study (NHS) and NHSII. Cox proportional hazards regression, stratified by dominance and time period, was used to examine the associations. For each exposure, we calculated the P-value for heterogeneity using a likelihood ratio test comparing models with separate estimates for the two subtypes versus a single estimate across subtypes. There were 281 DOM+ and 122 DOM− cases diagnosed between 1976 and 2006. In analyses of reproductive/hormonal exposures, there was no significant heterogeneity across the two subtypes for the associations with age, age at natural menopause, breastfeeding, parity, oral contraceptive use, estrogen use, and hysterectomy (P-heterogeneity ≥ 0.40). However, the association with tubal ligation was significantly stronger for DOM+ (RR=0.51; 95%CI=0.34–0.75) versus DOM− tumors (RR=0.95; 95%CI=0.58–1.56; P-heterogeneity=0.05). While associations with several non-reproductive exposures (e.g., BMI, physical activity, talc use) did not vary by subtype (P-heterogeneity ≥ 0.11), the association with family history of ovarian cancer was stronger for DOM− (RR=3.32; 95% CI=1.52–7.25) versus DOM+ tumors (RR=0.95; 95%CI=0.39–2.32; P-heterogeneity=0.04). The results were similar when we limited our analysis to 228 cases with serous invasive or poorly differentiated histology. Although limited by small case numbers, our results suggest that tubal ligation may be more strongly associated with tumors of ovarian origin, while family history of ovarian cancer primarily increases risk of tumors of tubal origin. Characterizing risk factor relationships by tumor dominance may elucidate how these exposures alter risk and help to improve prevention efforts.

Citation Information: Cancer Prev Res 2010;3(1 Suppl):A126.

Common genetic variation in IGF1, IGFBP1 and IGFBP3 and ovarian cancer risk

Insulin-like growth factor (IGF) 1 and its binding proteins foster cellular proliferation and inhibit apoptosis. In vitro studies show that IGF1 increases ovarian cell growth and invasive potential, suggesting a role for the IGF1 pathway in ovarian cancer etiology. We evaluated genetic variation in the IGF1, IGFBP1 and IGFBP3 genes in relation to ovarian cancer risk by genotyping 29 haplotype-tagging single nucleotide polymorphisms in 1173 cases and 1201 controls from the New England Case-Control (NECC) study and 296 cases and 854 controls from the Nurses' Health Study (NHS). The association of haplotypes and single nucleotide polymorphisms (SNPs) with ovarian cancer was estimated using unconditional (NECC) and conditional (NHS) logistic regression. Additionally, we evaluated the association of SNPs with IGF1, IGF-binding protein (IGFBP) 3 and IGFBP2 plasma levels (n = 380 NHS controls). Our data suggest a decreased risk for women carrying haplotype 2C of the IGF1 gene [odds ratios (ORs) = 0.82, 95% confidence intervals (CIs) = 0.69-0.98] and an increased risk for women carrying haplotype 1D (OR = 1.41, 95% CI = 1.03-1.94) or 2D (OR = 1.20, 95% CI = 1.01-1.41) in the binding proteins. When evaluated individually, three SNPs in the IGFBPs (rs10228265, rs4988515 and rs2270628) were associated with increased ovarian cancer risk, and several IGF1 (rs11111285, rs1996656 and rs1019731) and IGFBP3 (rs2270628, rs2854746 and rs2854744) SNPs were significantly associated with IGF1, IGFBP3 and IGFBP2 plasma levels. Some haplotypes and SNPs in the IGF pathway genes may be associated with ovarian cancer risk; however, these results need to be confirmed. Of particular interest was the IGFBP3 SNP rs2270628, which was associated with both increased IGF1 plasma levels and higher ovarian cancer risk.

Risk factors for epithelial ovarian cancer by histologic subtype

Previous epidemiologic studies suggest that the major histologic subtypes of epithelial ovarian cancer may have different risk factor profiles; however, no known prospective study has systematically examined differences in risk by subtype. The authors used Cox proportional hazards regression, stratified by histologic subtype and time period, to examine the association between ovarian cancer risk factors and incidence of serous invasive, endometrioid, and mucinous ovarian cancers in the US Nurses' Health Study (1976-2006) and Nurses' Health Study II (1989-2005). For each exposure, they calculated P-heterogeneity using a likelihood ratio test comparing models with separate estimates for the 3 subtypes versus a single estimate across subtypes. Analysis included 221,866 women and 721 cases with the histologies of interest (496 serous invasive, 139 endometrioid, 86 mucinous). In analyses of reproductive/hormonal exposures, the associations with age, duration of breastfeeding, age at natural menopause, and duration of estrogen use differed significantly by subtype (all P-heterogeneity < or =0.05). The associations with several nonreproductive exposures also appeared to vary by subtype, but only the association with smoking differed significantly (P-heterogeneity = 0.03). Results suggest that associations with several ovarian cancer risk factors vary by subtype, and these differences are consistent with known similarities between each major histologic subtype and its normal tissue counterpart.

Flavonoid intake and ovarian cancer risk in a population-based case-control study

Several recent studies have evaluated the association between dietary flavonoid intake and ovarian cancer risk, and all reported significant or suggestive inverse associations with certain flavonoids or flavonoid subclasses; however, most of these studies were small to moderate in size. We, therefore, examined this association in a large, population-based case-control study. We calculated intake of 5 common dietary flavonoids (myricetin, kaempferol, quercetin, luteolin, and apigenin), as well as total intake of these flavonoids, for 1,141 cases and 1,183 frequency-matched controls. We used unconditional logistic regression to estimate the relative risk (RR) of ovarian cancer for each quintile of flavonoid intake when compared with the lowest quintile. We did not observe an association between total flavonoid intake and ovarian cancer risk. The multivariable-adjusted RR for the highest versus lowest quintile of total flavonoid intake was 1.06 (95% confidence interval [CI] = 0.78-1.45). In analyses of each individual flavonoid, only intake of apigenin was associated with a borderline significant decrease in risk (RR, highest vs. lowest quintile = 0.79, 95% CI = 0.59-1.06; p-trend = 0.26), and this association was significant after adjustment for intake of the other 4 individual flavonoids (comparable RR = 0.72, 95% CI = 0.53-0.98; p-trend = 0.09). These results provide limited support for an association between flavonoid intake and ovarian cancer risk. However, given the findings of previous studies and the biologic plausibility of this association, additional studies are warranted.

Polymorphisms in the vitamin D receptor and risk of ovarian cancer in four studies

Prior studies have suggested that vitamin D may reduce ovarian cancer risk. Thus, we examined whether three single nucleotide polymorphisms (SNP) in the vitamin D receptor (VDR) gene (Fok1, Bsm1, Cdx2) were associated with risk of epithelial ovarian cancer in a retrospective case-control study (New England Case-Control study, NECC) and a nested case-control study of three prospective cohort studies: the Nurses' Health Study (NHS), NHSII, and the Women's Health Study. Data from the cohort studies were combined and analyzed using conditional logistic regression and pooled with the results from the NECC, which were analyzed using unconditional logistic regression, using a random effects model. We obtained genotype data for 1,473 cases and 2,006 controls. We observed a significant positive association between the number of Fok1 f alleles and ovarian cancer risk in the pooled analysis (P(trend) = 0.03). The odds ratio (OR) for the ff versus FF genotype was 1.26 [95% confidence interval (CI) = 1.01-1.57]. Neither the Bsm1 (P(trend) = 0.96) or Cdx2 (P(trend) = 0.13) SNPs were significantly associated with ovarian cancer risk. Among the prospective studies, the risk of ovarian cancer by plasma vitamin D levels did not clearly vary by any of the genotypes. For example, among women with the Fok1 FF genotype, the OR comparing plasma 25-hydroxyvitamin D >or=32 ng/mL versus <32 ng/mL was 0.66 (95% CI, 0.34-1.28), and among women with the Ff or ff genotype the OR was 0.71 (95% CI, 0.43-1.18). Our results of an association with the Fok1 VDR polymorphism further support a role of the vitamin D pathway in ovarian carcinogenesis.

Validation of tissue microarray technology in ovarian cancer: results from the Nurses' Health Study

BACKGROUND

Tissue microarrays (TMAs) allow high-throughput evaluation of protein expression from archived tissue samples. We identified characteristics specific to ovarian cancer that may influence TMA interpretation.

METHODS

TMAs were constructed using triplicate core samples from 174 epithelial ovarian cancers. Stains for p53, Ki-67, estrogen receptor-alpha, progesterone receptor, Her-2, WT-1, cytokeratin 7, and cytokeratin 20 were evaluated by intraclass correlation coefficients, Spearman correlation coefficients, the effect of sample age, and tumor histology on the ability to score the cores, and inter-rater reliability.

RESULTS

The interclass correlation coefficient and the mean Spearman correlation coefficients among 3 cores were > or = 0.91 and 0.87, respectively. Tissue age and tumor histology were not predictive of an inability to evaluate stains, but borderline tumors had a 2 to 4-fold increase in the risk of having uninterpretable cores over invasive tumors. There was moderate to substantial concordance between the two pathologists for estrogen receptor-alpha [Cohen's Kappa (kappa), 0.79] and Ki-67 (kappa, 0.52). The prevalence of positive staining cells by histologic type was comparable with previous studies.

CONCLUSION

TMA is a valid method for evaluating antigen expression in invasive ovarian cancer but should be used with caution for borderline tumors. We suggest several methods of quality control based on intercore comparisons and show that some antigens may be affected by age of the samples.

Ontogeny of substantia nigra dopamine neurons

Understanding the ontogeny of A9 dopamine (DA) neurons is critical not only to determining basic developmental events that facilitate the emergence of the substantia nigra pars compacta (SNc) but also to the extraction and de novo generation of DA neurons as a potential cell therapy for Parkinson's disease. Recent research has identified a precise window for DA cell birth (differentiation) in the ventral mesencephalon (VM) as well as a number of factors that may facilitate this process. However, application of these factors in vitro has had limited success in specifying a dopaminergic cell fate from undifferentiated cells, suggesting that other cell/molecular signals may as yet remain undiscovered. To resolve this, current work seeks to identify particularly potent and novel DA neuron differentiation factors within the developing VM specifically at the moment of ontogeny. Through such (past and present) studies, a catalog of proteins that play a pivotal role in the generation of nigral DA neurons during normal CNS development has begun to emerge. In the future, it will be crucial to continue to evaluate the critical developmental window where DA neuron ontogeny occurs, not only to facilitate our potential to protect these cells from degeneration in the adult brain but also to mimic the developmental environment in a way that enhances our ability to generate these cells anew either in vitro or in vivo. Here we review our present understanding of factors that are thought to be involved in the emergence of the A9 dopamine neuron group from the ventral mesencephalon.

Breast cancer susceptibility alleles and ovarian cancer risk in 2 study populations

Recent genome-wide scans identified several novel breast cancer risk alleles, including variants of the FGFR2, MAP3K1 and LSP1 genes, and a study of associations between these alleles and characteristics of breast cancer patients reported a borderline significant correlation between the number of FGFR2 minor alleles and family history of breast/ovarian cancer. Given these results and similarities in the etiology of breast and ovarian cancer, we examined the association between 7 novel breast cancer susceptibility alleles and epithelial ovarian cancer risk in 2 large study populations. Our analysis included 1,173 cases and 1,201 controls from a New England-based Case-Control study and 210 cases and 603 controls from the prospective Nurses' Health Study. We used logistic regression to estimate the odds ratio (OR) for individuals heterozygous or homozygous for the minor allele at each locus, compared to individuals with the wild-type genotype. We examined the associations separately in each population and, after testing for heterogeneity in the results, pooled the estimates using a random effects model. There was no clear association between these polymorphisms and ovarian cancer risk in either population. The pooled per allele OR for FGFR2 was 1.06 (95% confidence interval (CI)=0.95-1.18) for rs1219648 and 1.04 (95% CI=0.93-1.15) for rs2981582. We had more than 80% power to detect a log-additive OR of 1.16-1.18 per allele at the alpha=0.05 level in the pooled analysis. Our results do not provide strong support for an association between these breast cancer susceptibility alleles and epithelial ovarian cancer risk.

Talc use, variants of the GSTM1, GSTT1, and NAT2 genes, and risk of epithelial ovarian cancer

Epidemiologic evidence suggests a possible association between genital use of talcum powder and risk of epithelial ovarian cancer; however, the biological basis for this association is not clear. We analyzed interactions between talc use and genes in detoxification pathways [glutathione S-transferase M1 (GSTM1), glutathione S-transferase T1 (GSTT1), and N-acetyltransferase 2 (NAT2)] to assess whether the talc/ovarian cancer association is modified by variants of genes potentially involved in the response to talc. Our analysis included 1,175 cases and 1,202 controls from a New England-based case-control study and 210 cases and 600 controls from the prospective Nurses' Health Study. We genotyped participants for the GSTM1 and GSTT1 gene deletions and three NAT2 polymorphisms. We used logistic regression to analyze the main effect of talc use, genotype, and gene-talc interactions in each population and pooled the estimates using a random-effects model. Regular talc use was associated with increased ovarian cancer risk in the combined study population (RR, 1.36; 95% CI, 1.14-1.63; P(trend) < 0.001). Independent of talc, the genes examined were not clearly associated with risk. However, the talc/ovarian cancer association varied by GSTT1 genotype and combined GSTM1/GSTT1 genotype. In the pooled analysis, the association with talc was stronger among women with the GSTT1-null genotype (P(interaction) = 0.03), particularly in combination with the GSTM1-present genotype (P(interaction) = 0.03). There was no clear evidence of an interaction with GSTM1 alone or NAT2. These results suggest that women with certain genetic variants may have a higher risk of ovarian cancer associated with genital talc use. Additional research is needed on these interactions and the underlying biological mechanisms.

Caffeine, alcohol, smoking, and the risk of incident epithelial ovarian cancer

BACKGROUND

Smoking, caffeine, and alcohol intake are all potentially modifiable factors that have an unclear association with ovarian cancer risk. Therefore, the associations between these exposures and ovarian cancer risk were prospectively examined among 110,454 women in the Nurses' Health Study (NHS) for the smoking analyses and 80,253 women for the dietary analyses.

METHODS

Women completed biennial questionnaires assessing ovarian cancer risk factors beginning in 1976, with food frequency questionnaires administered every 2 to 4 years starting in 1980. For the smoking analyses, 737 confirmed cases of epithelial ovarian cancer were identified and for the dietary aims, 507 cases were identified through June 1, 2004.

RESULTS

Compared with never-smokers, neither current nor past smoking was associated with ovarian cancer risk overall; however, both were associated with mucinous tumors (n = 69; rate ratio [RR], past = 2.02 [95% confidence interval (CI), 1.15-3.55]; RR, current = 2.22 [95% CI, 1.16-4.24]). A modest inverse association between caffeine intake and ovarian cancer risk was observed (RR, top vs bottom quintile = 0.80; 95% CI, 0.60-1.07 [P = .03]), which was strongest for women who had never used either oral contraceptives (RR = 0.65; 95% CI, 0.46-0.92 [P for heterogeneity = .02]) or postmenopausal hormones (RR = 0.57; 95% CI, 0.36-0.91 [P for heterogeneity = .13]). Alcohol was not associated with ovarian cancer risk.

CONCLUSIONS

The results of the current study suggest that cigarette smoking may only increase the risk for mucinous ovarian tumors, and alcohol intake was not associated with risk. However, an inverse association was observed between caffeine intake and ovarian cancer risk, particularly in women not using hormones; this finding merits further study.

A prospective study of dietary flavonoid intake and incidence of epithelial ovarian cancer

Flavonoids are antioxidant compounds found in plants, including fruits, vegetables and tea. No prior prospective studies have examined the association between intake of flavonoids in the flavonol and flavone subclasses and ovarian cancer risk. We analyzed the association between intake of 5 common dietary flavonoids and incidence of epithelial ovarian cancer among 66,940 women in the Nurses' Health Study. We calculated each participant's intake of myricetin, kaempferol, quercetin, luteolin and apigenin from dietary data collected at multiple time points, and used Cox proportional hazards regression to model the incidence rate ratio (RR) of ovarian cancer for each quintile of intake. Our analysis included 347 cases diagnosed between 1984 and 2002, and 950,347 person-years of follow-up. There was no clear association between total intake of the 5 flavonoids examined and incidence of ovarian cancer (RR = 0.75 for the highest versus lowest quintile, 95% confidence interval [CI] = 0.51-1.09). However, there was a significant 40% decrease in ovarian cancer incidence for the highest versus lowest quintile of kaempferol intake (RR = 0.60, 95% CI = 0.42-0.87; p-trend = 0.002), and a significant 34% decrease in incidence for the highest versus lowest quintile of luteolin intake (RR = 0.66, 95% CI = 0.49-0.91; p-trend = 0.01). There was evidence of an inverse association with consumption of tea (nonherbal) and broccoli, the primary contributors to kaempferol intake in our population. These data suggest that dietary intake of certain flavonoids may reduce ovarian cancer risk, although additional prospective studies are needed to further evaluate this association. If confirmed, these results would provide an important target for ovarian cancer prevention.

Improved survival of young donor age dopamine grafts in a rat model of Parkinson's disease

In an attempt to improve the survival of implanted dopamine cells, we have readdressed the optimal embryonic donor age for dopamine grafts. In a rat model of Parkinson's disease, animals with unilateral 6-hydroxydopamine lesions of the median forebrain bundle received dopamine-rich ventral mesencephalic grafts derived from embryos of crown to rump length 4, 6, 9, or 10.5 mm (estimated embryonic age (E) 11, E12, E13 and E14 days post-coitus, respectively). Grafts derived from 4 mm embryos survived poorly, with less than 1% of the implanted dopamine cells surviving. Grafts derived from 9 mm and 10.5 mm embryos were similar to those seen in previous experiments with survival rates of 8% and 7% respectively. The best survival was seen in the group that received 6 mm grafts, which were significantly larger than all other graft groups. Mean dopamine cell survival in the 6 mm group (E12) was 36%, an extremely high survival rate for primary, untreated ventral mesencephalic grafts applied as a single placement, and more than fivefold larger than the survival rate observed in the 10.5 mm (E14) group. As E12 ventral mesencephalic tissues contain few, if any, differentiated dopamine cells we conclude that the large numbers of dopamine cells seen in the 6 mm grafts must have differentiated post-implantation. We consider the in vivo conditions which allow this differentiation to occur, and the implications for the future of clinical trials based on dopamine cell replacement therapy.

Operating room nursing and lung cancer risk in a cohort of female registered nurses

OBJECTIVES

Smoke generated during laser surgery and electrocautery contains respiratory irritants and human carcinogens. Although laboratory and animal studies have demonstrated that this smoke has inflammatory and mutagenic potential, no population-based studies of the health effects of exposure to surgical smoke have been published. We examined the association between duration of employment as an operating room nurse, a proxy measure for surgical smoke exposure, and subsequent lung cancer risk.

METHODS

This study was conducted among 86 747 women in the Nurses' Health Study. Information on the duration of prior operating room employment was collected in 1984, and the women were followed for incident, confirmed lung cancer. Cox proportional hazards regression was used to model the incidence rate ratio of lung cancer for each exposure category using women with no prior operating room employment for comparison. All of the models were adjusted for age, smoking history, passive smoke exposure, fruit and vegetable consumption, and alpha carotene and lycopene intake.

RESULTS

A history of operating room employment was not associated with an increased rate of lung cancer in multivariable analyses [rate ratio (RR) 0.99, 95% confidence interval (95% CI) 0.86-1.15]. In fact, nurses in the highest exposure category, > or =15 years of operating room employment, had a significantly lower rate of lung cancer than nurses with no prior operating room employment (RR 0.58, 95% CI 0.37-0.91), possibly due to confounding by overall health status or residual confounding by smoking history.

CONCLUSIONS

Long-term exposure to surgical smoke, as measured by the duration of operating room employment, does not appear to increase the risk of lung cancer.

The influence of astrocytes on the development, regeneration and reconstruction of the nigrostriatal dopamine system

Over the past few decades astrocytes have emerged from being considered simple packing tissue in the brain to become major players in the development, survival and functioning of central nervous system (CNS) neurons. As the influence that astrocytes (and the various molecules they produce) have on the development of CNS neurons becomes more evident, it will be important to consider how this information can be exploited to bring about better protection, recovery and/or regeneration of circuits which are destroyed in the adult CNS due to trauma or com-mon neurodegenerative episodes. Although the characterisation of astrocytic responses to brain injuries, neurodegenerative disease, and cell transplantation are becoming more common, we still known little about how astrocytes influence the (re)growth or reconstruction of neural circuitry after the development period is ended, or indeed what is the overall impact of an astrocytic presence on the growth of neurons in the adult CNS. With the major hurdle of recognition of the importance astrocytes in the function and recovery of the adult CNS now cleared, a new chapter in the development of powerful new treatments for CNS disorders and injuries is now open. The following is a brief review of what we know about how astrocytes influence the growth and connectivity of the nigrostriatal circuit during development, and how these cells may affect efforts to reform this circuit after it s destruction/degeneration in the adult CNS (as commonly happens in Parkinson s disease). As we obtain more information on the specific influence of these cells in various developmental, traumatic and disease events we can expect to find better ways toward combating major disorders of the human CNS.

The homeobox genesvoxandventare redundant repressors of dorsal fates in zebrafish

Ventralizing transcriptional repressors in the Vox/Vent family have been proposed to be important regulators of dorsoventral patterning in the early embryo. While the zebrafish genes vox (vega1) and vent (vega2) both have ventralizing activity in overexpression assays, loss-of-function studies are needed to determine whether these genes have distinct or redundant functions in dorsoventral patterning and to provide critical tests of the proposed regulatory interactions among vox, vent and other genes that act to establish the dorsoventral axis. We show that vox and vent are redundant repressors of dorsal fates in zebrafish. Mutants that lack vox function have little or no dorsoventral patterning defect, and inactivation of either vox or vent by injection of antisense morpholino oligonucleotides has little or no effect on the embryo. In contrast, embryos that lack both vox and vent function have a dorsalized phenotype. Expression of dorsal mesodermal genes, including chordin, goosecoid and bozozok, is strongly expanded in embryos that lack vox and vent function, indicating that the redundant action of vox and vent is required to restrict dorsal genes to their appropriate territories. Our genetic analysis indicates that the dorsalizing transcription factor Bozozok promotes dorsal fates indirectly, by antagonizing the expression of vox and vent. In turn, vox and vent repress chordin expression, restricting its function as an antagonist of ventral fates to the dorsal side of the embryo. Our results support a model in which BMP signaling induces the expression of ventral genes, while vox and vent act redundantly to prevent the expression of chordin, goosecoid and other dorsal genes in the lateral and ventral mesendoderm.

Fast1 is required for the development of dorsal axial structures in zebrafish

Nodal-related signals comprise a subclass of the transforming growth factor-beta (TGF-beta) superfamily and regulate key events in vertebrate embryogenesis, including mesoderm formation, establishment of left-right asymmetry and neural patterning [1-8]. Nodal ligands are thought to act with EGF-CFC protein co-factors to activate activin type I and II or related receptors, which phosphorylate Smad2 and trigger nuclear translocation of a Smad2/4 complex [8-12]. The winged-helix transcription factor forkhead activin signal transducer-1 (Fast-1) acts as a co-factor for Smad2 [12-20]. Xenopus Fast-1 is thought to function as a transcriptional effector of Nodal signals during mesoderm formation [17], but no mutations in the Fast-1 gene have been identified. We report the identification of the zebrafish fast1 gene and show that it is disrupted in schmalspur (sur) mutants, which have defects in the development of dorsal midline cell types and establishment of left-right asymmetry [21-25]. We find that prechordal plate and notochord are strongly reduced in maternal-zygotic sur mutants, whereas other mesendodermal structures are present - a less severe phenotype than that caused by complete loss of Nodal signaling. These results show that fast1 is required for development of dorsal axial structures and left-right asymmetry, and suggest that Nodal signals act through Fast1-dependent and independent pathways.

Neocortical neurons lacking the protein-tyrosine kinase B receptor display abnormal differentiation and process elongation in vitro and in vivo

The spatial and temporal expression of the protein-tyrosine kinase B (TrkB) receptor and its ligands has been correlated with the development of the neocortex. Activation of the receptor has been associated with neocortical neuronal survival, differentiation, connectivity and neurotransmitter release. Although such findings suggest an important role for TrkB signaling in corticogenesis, conclusive evidence from targeted gene deletion ("knockout"; TrkB -/-) mice has been limited, due in part to the neonatal lethality of most of these mutant mice and the confounding variables associated with the poor health of those few surviving slightly longer postnatally. In the present study, the effects of TrkB signaling on the survival, differentiation and integration of neocortical neurons was directly investigated in vitro and in vivo. First, we conducted a neuron-specific immunocytochemical analysis of TrkB -/- mice to determine whether early cortical structure and patterns of histogenesis were normal or perturbed. We then employed in vitro and in vivo approaches to extend the life of TrkB -/- neocortical neurons beyond the period possible in TrkB -/- mutant mice themselves: (i) dissociated cell culture to directly compare the developmental potential of TrkB -/-, +/- and +/+ neurons; and (ii) neural transplantation into homochronic wild-type recipients to investigate the cell-autonomous effects of the receptor knockout on the differentiation, growth and integration of neocortical neurons. These latter experiments allowed, for the first time, study of the survival and differentiation potential of TrkB -/- neocortical neurons beyond the initial stages of corticogenesis. Direct comparison of brains of TrkB -/-, +/- and +/+ littermates immunocytochemically labeled with antibodies to microtubule-associated protein-2, neurofilament and beta-tubulin III revealed subtle anatomical anomalies in the mutant mice. These anomalies include abnormally diffuse microtubule-associated protein-2 positive neurons just dorsal to the corpus callosum, and heterotopic aggregations of postmitotic neurons in the subventricular zones of the ganglionic eminences, both suggesting delayed neuronal migration and differentiation. Cell culture experiments revealed substantially reduced survival by TrkB -/- neocortical neurons, and a significant reduction in neurite outgrowth by surviving TrkB -/- neurons. In experiments where prelabeled embryonic or neonatal TrkB -/- neocortical neurons were transplanted into the cerebral cortices of neonatal wild-type recipients, a similar quantitatively significant defect in the formation of dendrites, as well as reduced integration of TrkB -/- neocortical neurons, was also evident. These findings demonstrate cell-autonomous abnormalities in the development of neocortical neurons from TrkB -/- mice, and the subtle, but potentially critical, role of protein-tyrosine kinase B signaling in neocortical neuronal survival, differentiation and connectivity.

Long-term, EGF-stimulated cultures of attached GFAP-positive cells derived from the embryonic mouse lateral ganglionic eminence: in vitro and transplantation studies

Long-term attached cultures, prepared from mouse embryonic days 15-17 lateral ganglionic eminence, were grown in a medium including epidermal growth factor and serum, and the survival, differentiation, and migration of cells from either early or late passages were analyzed following transplantation. The cultured cells had the morphology of type I astroglial cells, with the vast majority of the cells immunoreactive for glial fibrillary acidic protein (around 90%), the intermediate filament marker nestin, and also the mouse-specific neural markers M2 and M6. The cultures were kept over 25 passages (7 months). During the first 8 passages, the growth rate gradually declined, but it increased again after passage 9 and thereafter stabilized at values similar to those observed during the initial culture period. After passages 4-6 and 18, cell suspensions were implanted cross-species into the intact or lesioned striatum of adult (passages 4-5 only) or intact striatum of neonatal rats (passages 4-6 or 18). Both early and late passage cells formed M2 (and M6)-positive transplants. In the neonatal recipients, widespread migration was seen from the needle tract throughout most of the striatum, along the internal capsule, and into the globus pallidus. In the adult striatum, the cells remained mostly around the injection tract, or within 0.4-0.6 mm from the graft core. These long-term attached cultures are interesting to compare to nonattached neurosphere cultures, and might also offer a means of propagating relatively pure populations of astroglia-like cells for basic transplantation studies or for use in experimental trials with ex vivo gene transfer.

A radiation hybrid map of the zebrafish genome

Recent large-scale mutagenesis screens have made the zebrafish the first vertebrate organism to allow a forward genetic approach to the discovery of developmental control genes. Mutations can be cloned positionally, or placed on a simple sequence length polymorphism (SSLP) map to match them with mapped candidate genes and expressed sequence tags (ESTs). To facilitate the mapping of candidate genes and to increase the density of markers available for positional cloning, we have created a radiation hybrid (RH) map of the zebrafish genome. This technique is based on somatic cell hybrid lines produced by fusion of lethally irradiated cells of the species of interest with a rodent cell line. Random fragments of the donor chromosomes are integrated into recipient chromosomes or retained as separate minichromosomes. The radiation-induced breakpoints can be used for mapping in a manner analogous to genetic mapping, but at higher resolution and without a need for polymorphism. Genome-wide maps exist for the human, based on three RH panels of different resolutions, as well as for the dog, rat and mouse. For our map of the zebrafish genome, we used an existing RH panel and 1,451 sequence tagged site (STS) markers, including SSLPs, cloned candidate genes and ESTs. Of these, 1,275 (87.9%) have significant linkage to at least one other marker. The fraction of ESTs with significant linkage, which can be used as an estimate of map coverage, is 81.9%. We found the average marker retention frequency to be 18.4%. One cR3000 is equivalent to 61 kb, resulting in a potential resolution of approximately 350 kb.

Site-specific migration and neuronal differentiation of human neural progenitor cells after transplantation in the adult rat brain

Neural progenitor cells obtained from the embryonic human forebrain were expanded up to 10(7)-fold in culture in the presence of epidermal growth factor, basic fibroblast growth factor, and leukemia inhibitory growth factor. When transplanted into neurogenic regions in the adult rat brain, the subventricular zone, and hippocampus, the in vitro propagated cells migrated specifically along the routes normally taken by the endogenous neuronal precursors: along the rostral migratory stream to the olfactory bulb and within the subgranular zone in the dentate gyrus, and exhibited site-specific neuronal differentiation in the granular and periglomerular layers of the bulb and in the dentate granular cell layer. The cells exhibited substantial migration also within the non-neurogenic region, the striatum, in a seemingly nondirected manner up to approximately 1-1.5 mm from the graft core, and showed differentiation into both neuronal and glial phenotypes. Only cells with glial-like features migrated over longer distances within the mature striatum, whereas the cells expressing neuronal phenotypes remained close to the implantation site. The ability of the human neural progenitors to respond in vivo to guidance cues and signals that can direct their differentiation along multiple phenotypic pathways suggests that they can provide a powerful and virtually unlimited source of cells for experimental and clinical transplantation.

Serial MR imaging of experimental autoimmune encephalomyelitis induced by human white matter or by chimeric myelin-basic and proteolipid protein in the common marmoset

BACKGROUND AND PURPOSE

Experimental autoimmune encephalomyelitis (EAE) in the marmoset was monitored by serial MR imaging to determine correlates to the natural-history MR studies in multiple sclerosis (MS). The relationships of MR-revealed lesions to clinical status and histopathologic findings were also explored.

METHODS

We induced EAE by subcutaneous inoculation in two marmosets by human white matter (HWM) and in seven marmosets by MP4 (a chimeric recombinant fusion protein of myelin-basic and proteolipid protein) in adjuvant along with intravenous inactivated pertussis vaccine to facilitate the disease process. The HWM-inoculated animals were induced with Freund's adjuvant as the established model of marmoset EAE. The MP4-inoculated animals were induced with either Freund's incomplete adjuvant or TiterMax as part of a preclinical treatment trial. MR imaging was performed at 1.5 T at baseline, and repeated at 1- to 2-week intervals for a period of up to 16 weeks in six EAE-induced marmosets, and intermittently for up to 70 weeks in three EAE-induced and two control marmosets. Proton density- (PD-) and T2-weighted, pre- and postgadopentetate dimeglumine enhancement, T1-weighted, and magnetization transfer (MT) images were obtained. The brains were prepared for histologic evaluation of lesion distribution and counts, characterization of lesions as demyelinating or inflammatory, and histopathologic scoring. The clinical, MR, and pathologic scoring were done on grading systems, and correlated for evaluation.

RESULTS

White matter (WM) changes after EAE induction were observed first at 9 days in the HWM-induced animals and at 2.5 weeks in the MP4-induced animals, with subsequent week-to-week fluctuations on PD- and T2-weighted images. Contrast-enhancing lesions were not observed in all animals. MR-revealed WM lesions correlated to histopathologic analysis of EAE lesions, measuring from 0.5 mm to 1.5 mm. The lesion count and extent of demyelination was greater in the HWM-induced animals than in the MP4-induced animals. Some MR-revealed lesions correlated directly to clinical symptoms, but the majority of lesions were clinically silent.

CONCLUSION

On MR images, lesions in the EAE marmoset model were confined to the WM, and their development, resolution, distribution, and enhancing characteristics fluctuated over the duration of the study. The dynamic presentation of MR-revealed lesions confirms the parallels between EAE in the marmoset and relapsing-remitting MS. Clinical symptoms alone were not representative of ongoing pathologic brain lesions. Therefore, serial MR imaging serves as a very important adjunct to clinical and histologic surveillance of the development of new and the persistence of existing brain lesions in this animal model of MS.

A genetic linkage map for zebrafish: comparative analysis and localization of genes and expressed sequences

Genetic screens in zebrafish (Danio rerio) have isolated mutations in hundreds of genes with essential functions. To facilitate the identification of candidate genes for these mutations, we have genetically mapped 104 genes and expressed sequence tags by scoring single-strand conformational polymorphisms in a panel of haploid siblings. To integrate this map with existing genetic maps, we also scored 275 previously mapped genes, microsatellites, and sequence-tagged sites in the same haploid panel. Systematic phylogenetic analysis defined likely mammalian orthologs of mapped zebrafish genes, and comparison of map positions in zebrafish and mammals identified significant conservation of synteny. This comparative analysis also identified pairs of zebrafish genes that appear to be orthologous to single mammalian genes, suggesting that these genes arose in a genome duplication that occurred in the teleost lineage after the divergence of fish and mammal ancestors. This comparative map analysis will be useful in predicting the locations of zebrafish genes from mammalian gene maps and in understanding the evolution of the vertebrate genome.