From the Cover: Population-based screening for breast and ovarian cancer risk due to BRCA1 and BRCA2

In the Ashkenazi Jewish (AJ) population of Israel, 11% of breast cancer and 40% of ovarian cancer are due to three inherited founder mutations in the cancer predisposition genes BRCA1 and BRCA2. For carriers of these mutations, risk-reducing salpingo-oophorectomy significantly reduces morbidity and mortality. Population screening for these mutations among AJ women may be justifiable if accurate estimates of cancer risk for mutation carriers can be obtained. We therefore undertook to determine risks of breast and ovarian cancer for BRCA1 and BRCA2 mutation carriers ascertained irrespective of personal or family history of cancer. Families harboring mutations in BRCA1 or BRCA2 were ascertained by identifying mutation carriers among healthy AJ males recruited from health screening centers and outpatient clinics. Female relatives of the carriers were then enrolled and genotyped. Among the female relatives with BRCA1 or BRCA2 mutations, cumulative risk of developing either breast or ovarian cancer by age 60 and 80, respectively, were 0.60 (± 0.07) and 0.83 (± 0.07) for BRCA1 carriers and 0.33 (± 0.09) and 0.76 (± 0.13) for BRCA2 carriers. Risks were higher in recent vs. earlier birth cohorts (P = 0.006). High cancer risks in BRCA1 or BRCA2 mutation carriers identified through healthy males provide an evidence base for initiating a general screening program in the AJ population. General screening would identify many carriers who are not evaluated by genetic testing based on family history criteria. Such a program could serve as a model to investigate implementation and outcomes of population screening for genetic predisposition to cancer in other populations.Inherited mutations in BRCA1 and BRCA2 predispose to high risks of breast and ovarian cancer. Among female mutation carriers, presymptomatic surgical measures significantly reduce morbidity and mortality (1, 2). In particular, risk-reducing salpingo-oophorectomy (i.e., the removal of ovaries and fallopian tubes from a woman without ovarian cancer) reduces risk both of breast cancer and of ovarian cancer, as well as overall mortality (1). However, for many mutation carriers identified following their first cancer diagnosis, genetic testing was not previously indicated because family history did not suggest inherited cancer predisposition (3–5, 6). From a prevention perspective, it is a missed opportunity to identify a woman as a BRCA1 or BRCA2 mutation carrier only after she develops cancer.Among Ashkenazi (European) Jews (AJ), three mutations, BRCA1 185delAG, BRCA1 5382insC, and BRCA2 6174delT, account for the great majority of inherited cancer risk due to BRCA1 and BRCA2 (7). In the AJ population, 2.5% of persons carry one of these three mutations (8), and the mutations account for 11% of breast cancer (3) and 40% of ovarian cancer (9, 10). These observations suggest that genetic testing in the AJ population for these mutations fulfills WHO criteria for population screening (11, 12): The disease is an important public health burden to the target population; prevalence and attributable risk of disease due to the mutations are known; and effective interventions exist. However, one necessary piece of information remains unknown: What is the disease risk to mutation carriers ascertained from the general population, rather than carriers identified based on family history (13)?Previous studies assessing cancer risks due to mutations in BRCA1 and BRCA2 ascertained carriers through high-incidence families (14), through a single index case with breast or ovarian cancer (3, 15) or through both affected and unaffected carriers (16). In a 1997 study of AJ volunteers, most index cases had no previous cancer diagnosis, but the percentage of index cases with a family history of breast cancer was approximately double that of unselected AJs (17). In principle, these strategies could have yielded risk estimates different from those of carriers ascertained from the local host population, if cancer risk in BRCA1 or BRCA2 carriers were influenced by familial factors other than the BRCA1 or BRCA2 mutation, such as modifier genes or shared environment (18). In addition, in almost all of these studies, risk estimates were based on imputing carrier status, rather than on direct genetic testing of BRCA1 and BRCA2. This year, the Recommendation Statement on BRCA Testing from the US Preventive Services Task Force recommended against population screening for BRCA1 and BRCA2 mutations, because cancer risk to mutation carriers in the general population was not yet known (19). To address this gap, in this study we assessed breast and ovarian cancer risks in confirmed carriers of BRCA1 and BRCA2 mutations ascertained from the general population. The study was undertaken in the AJ population, because screening for only three founder mutations is sufficient to capture nearly all inherited cancer risk in this population due to BRCA1 and BRCA2 (7).     

Hippocampus-specific deficiency in RNA editing of GluA2 in Alzheimer's disease

Adenosine to inosine (A-to-I) RNA editing is a base recoding process within precursor messenger RNA, catalyzed by members of the adenosine deaminase acting on RNA (ADAR) family. A notable example occurs at the Q/R site of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid glutamate receptor subunit GluA2. Abnormally, low editing at this site leads to excessive calcium influx and cell death. We studied hippocampus and caudate samples from Alzheimer's disease (AD) patients and age-matched healthy controls, using direct sequencing and a high accuracy primer-extension technique to assess RNA editing at the Q/R GluA2 site. Both techniques revealed lower, more variable RNA editing in AD, specific to the hippocampus and the GluA2 site. Deficient editing also characterized the hippocampus of apolipoprotein ε4 allele carriers, regardless of clinical diagnosis. In AD, messenger RNA expression of neuronal markers was decreased in the hippocampus, and expression of the Q/R-site editing enzyme ADAR2 was decreased in caudate. These findings provide a link between neurodegenerative processes and deficient RNA editing of the GluA2 Q/R site, and may contribute to both diagnosis and treatment of AD.     

Reduced incidence and severity of collagen-induced arthritis in interleukin-12-deficient mice

Collagen-induced arthritis (CIA) is an animal model for rheumatoid arthritis. The disease is elicited by immunization of genetically susceptible DBA/1 mice with type II collagen, resulting in a debilitating arthritis characterized by inflammation and involvement of multiple joints. We investigated the role of endogenous interleukin (IL)-12 in the pathogenesis of this disease by undertaking an analysis of IL-12-deficient mice on the DBA/1 genetic background after immunization with type II collagen. Both the incidence and severity of disease were significantly reduced in mice unable to produce biologically active IL-12. Concomitant decreases were observed in serum levels of pathogenic, collagen-specific IgG2a antibodies and collagen-induced secretion of interferon-γ by immune splenocytes in vitro, consistent with an impaired T helper-1 response. There were, however, a few animals which developed severe disease in a single paw in spite of this highly diminished Th1 response. Taken together, these results demonstrate an important role for IL-12 in the pathogenesis of CIA, although it is not absolutely required for disease development.     

Biome boundary maintained by intense belowground resource competition in world’s thinnest-rooted plant community

Recent findings point to plant root traits as potentially important for shaping the boundaries of biomes and for maintaining the plant communities within. We examined two hypotheses: 1) Thin-rooted plant strategies might be favored in biomes with low soil resources; and 2) these strategies may act, along with fire, to maintain the sharp boundary between the Fynbos and Afrotemperate Forest biomes in South Africa. These biomes differ in biodiversity, plant traits, and physiognomy, yet exist as alternative stable states on the same geological substrate and in the same climate conditions. We conducted a 4-y field experiment to examine the ability of Forest species to invade the Fynbos as a function of growth-limiting nutrients and belowground plant–plant competition. Our results support both hypotheses: First, we found marked biome differences in root traits, with Fynbos species exhibiting the thinnest roots reported from any biome worldwide. Second, our field manipulation demonstrated that intense belowground competition inhibits the ability of Forest species to invade Fynbos. Nitrogen was unexpectedly the resource that determined competitive outcome, despite the long-standing expectation that Fynbos is severely phosphorus constrained. These findings identify a trait-by-resource feedback mechanism, in which most species possess adaptive traits that modify soil resources in favor of their own survival while deterring invading species. Our findings challenge the long-held notion that biome boundaries depend primarily on external abiotic constraints and, instead, identify an internal biotic mechanism—a selective feedback among traits, plant–plant competition, and ecosystem conditions—that, along with contrasting fire regime, can act to maintain biome boundaries.

Recent findings (1) have demonstrated striking differences in plant rooting strategies across biomes worldwide, spawning the hypothesis that belowground competition for soil resources may be critical for maintaining biome boundaries (1, 2). This idea differs fundamentally from the historical notion that biomes primarily are delineated by extrinsic abiotic factors such as climate, geological parent material, or topography (3–8), or the more recent recognition that aboveground plant adaptations can promote fire-determined plant communities (9, 10).Belowground competition introduces a biotic mechanism that is intrinsic to the plant community, emerges from plant–plant contest for resources, and may help explain the puzzling observation that biome boundaries can persist independent of climate–geological factors (4, 10).Of central importance is Ma et al.’s (1) recent observation that root traits that are associated with resource uptake appear to differ across biomes with differing soil resource dynamics. Specifically, Ma et al. hypothesized that thin-rooted plant strategies may be favored in biomes with permanently or seasonally low soil resources. They reasoned that, in those conditions, natural selection would favor absorptive roots [i.e., first-order roots (1, 11)] with low diameter and high specific root length (i.e., root length per unit photosynthetic carbon invested), which, in turn, are traits that allow high root surface area and efficient exploration of resource-poor soils. Conversely, thick roots and low specific root length may remain competitive traits in biomes with abundant soil resources, despite reduced root surface area and less efficient soil exploration.Here we test Ma et al.’s hypothesis (1) using a unique study of root traits and plant–plant resource competition across the boundary of two distinct biomes within the Cape Floristic Region of South Africa: Fynbos and Afrotemperate Forest. We show in Fig. 1 and 12, 13), by slow decomposition and nutrient recycling (14), and by low stores of soil organic matter (15). In contrast, the Afrotemperate Forest biome is defined by a substantial accumulation of soil organic matter and organic-bound nutrients, which, in turn, supports high rates of plant–soil–nutrient recycling. Based on Ma et al.’s hypothesis, we would expect that these sharp differences in soil resource conditions would result in divergent belowground root traits across the biome boundary.Open in a separate windowFig. 1.Sharp differences in biodiversity, aboveground plant traits, and ecosystem properties across the South African Fynbos–Forest boundary. (A) Two neighboring biomes of the Cape Floristic Region—the Fynbos (62) and the Afrotemperate Forest (63)—form a sharp boundary despite perching on the same geological parent material (39). (B) Biodiversity: The hyperdiverse Fynbos harbors >7,000 plant species, of which the majority are endemic to South Africa (64). The Afrotemperate Forest, on the other hand, contains >450 species with less endemism (63). (C) Aboveground plant traits: Fynbos species generally possess thick and small leaves with a high carbon-to-nitrogen (C:N) ratio while Afrotemperate Forest species display thinner and larger leaves with a lower C:N ratio. In addition, Fynbos plant species possess traits that either enhance (e.g., waxes) or resist (e.g., thick bark) fire. For example, Fynbos vegetation contains high concentrations of flammable organic compounds (e.g., crude fat content) that can facilitate very hot fires (65). In contrast, Afrotemperate Forest species tend to be sensitive to fire and possess traits that suppress fire (e.g., high water content). (D) Ecosystem properties: Fynbos soils are exceedingly poor in soil carbon, nitrogen, and phosphorus contents. In contrast, the Afrotemperate Forest soil is characterized by a developed layer rich in carbon, nitrogen, and phosphorus, which facilitates active cycling of nutrients between plant and soil pools (66, 67).Table 1.Comparison of neighboring Fynbos and Afrotemperate Forest

Reversal of hyperglycemia in mice by using human expandable insulin-producing cells differentiated from fetal liver progenitor cells

Beta-cell replacement is considered to be the most promising approach for treatment of type 1 diabetes. Its application on a large scale is hindered by a shortage of cells for transplantation. Activation of insulin expression, storage, and regulated secretion in stem/progenitor cells offers novel ways to overcome this shortage. We explored whether fetal human progenitor liver cells (FH) could be induced to differentiate into insulin-producing cells after expression of the pancreatic duodenal homeobox 1 (Pdx1) gene, which is a key regulator of pancreatic development and insulin expression in beta cells. FH cells possess a considerable replication capacity, and this was further extended by introduction of the gene for the catalytic subunit of human telomerase. Immortalized FH cells expressing Pdx1 activated multiple beta-cell genes, produced and stored considerable amounts of insulin, and released insulin in a regulated manner in response to glucose. When transplanted into hyperglycemic immunodeficient mice, the cells restored and maintained euglycemia for prolonged periods. Quantitation of human C-peptide in the mouse serum confirmed that the glycemia was normalized by the transplanted human cells. This approach offers the potential of a novel source of cells for transplantation into patients with type 1 diabetes.     

Ethnic ancestry and increased paternal age are risk factors for breast cancer before the age of 40 years.

To study the risk factors associated with breast cancer in women younger than 40 years, a cohort study (The Jerusalem Perinatal Study) of 42 822 female offspring born in hospitals in West Jerusalem during 1964-1976 was carried out. Hazard ratios of potential parental and perinatal risk factors for early breast cancer were measured. The overall incidence of breast cancer was 5.2/100 000 person-years. The highest incidence was found among Jewish women of West Asian ancestry (8.6/100 000 person-years), specifically those whose maternal grandfathers were born in Iraq, Iran or Afghanistan (9.5/100 000 person-years). Using Cox models we found independent risk factors for early breast cancer to be paternal age (relative risk/year=1.06, 95% confidence interval=1.02-1.10, P=0.005), and ancestry from Iraq/Iran/Afghanistan (relative risk=3.1, 95% confidence interval=1.50-6.52, P=0.002). The study confirms a previously observed effect of advanced paternal age on the occurrence of early breast cancer and identifies a novel population group at increased risk for the disease. The excess risk of early breast cancer associated with ancestry from Iraq, Iran and Afghanistan suggests involvement of genetic determinants, environmental exposures and/or lifestyle factors and mandates further investigation.     

Improved method of ultrasonic diagnosis of maxillary sinus diseases in children

A modified technique of ultrasonic diagnosis of accessory nasal sinus diseases based on an analysis of the profile of echograms has been developed. A correlation between the profile and pathological changes in the Highmore antrum has been found. It has been shown that the cystic fluid has a characteristic difference between the intensity of the start and echo impulses. Echograms of a cyst and its capsule reveal that they are significantly heterogeneous. Pus is characterized by a pronounced ultrasound absorption, fluid pus and thick pus showing different response. Plasma and blood are characterized by a significant ultrasound absorption and sufficient homogeneity. An interpretation of an echogram obtained under clinical conditions is presented.     

N-acetylglutamate synthase deficiency and the treatment of hyperammonemic encephalopathy

Carbamylphosphate synthase is the first enzymatic reaction of the urea cycle. Its activator, N-acetylglutamate, is synthesized from acetyl-CoA and glutamate in a reaction catalyzed by N-acetylglutamate synthase (NAGS). We have identified the putative human NAGS gene and report the first mutation in this gene in a family with carbamylglutamate responsive hyperammonemia and normal activity of the urea cycle enzymes. Mutation analysis has a higher diagnostic specificity than the enzymatic assay in NAGS deficiency. A therapeutic trial with carbamylglutamate is recommended whenever hyperammonemia without an organic aciduria, increased orotate excretion, or diagnostic amino acidemia/uria is detected.     

Minimax two-stage-designs with applications to tissue banking case-control studies

'Tissue banks' are created, at least in part, to help medical scientists learn about disease biology on the basis of samples provided by patients on treatment protocols that were competed years earlier.The bank inventory consists of precious non-renewable patient material (such as frozen diagnostic blood or bone marrow), which can be linked to both clinical data and long term follow-up information. Case-control studies, where cases represent clinical failures and controls clinical successes, are ideal for rapidly learning if a laboratory marker might have prognostic significance. While group sequential (multi-stage) methods are widely used in clinical trials, they have rarely been applied in case-control studies. Further, unlike clinical trials where safety and efficiency may actually be in conflict, case-control studies can focus on efficiency. Hence, minimizing the expected sample size is a desirable goal in such a setting. Since the true effect size is never known, and since no prior distribution can be postulated for the effect size, we have opted for the minimax solution. A strategy is developed to determine amongst all two-stage designs with given type I and type II errors, the one for which the maximum expected sample size is minimized. The user is provided with simple tables, whereby one can determine everything necessary to conduct the study from the corresponding calculation for a single-stage design. A matched pair example is given where the suggested design can be modified, to obtain a superior 'two-plus' stage design. The basic idea is to conduct the first stage as planned, but use the estimate of variance to redesign the study, without using the estimate of effect size in the redesign.