Cumulative lifetime incidence of extracolonic cancers in Lynch syndrome: a report of 121 families with proven mutations

Lynch syndrome or hereditary non-polyposis colorectal cancer is caused by mutations of DNA mismatch repair (MMR) genes. The extracolonic tumour spectrum includes endometrial, ovarian, gastric, small bowel, pancreatic, hepatobiliary, brain, and urothelial neoplasms. Families were referred on the basis of clinical criteria. Tumour immunohistochemistry and microsatellite testing were performed. Appropriate patients underwent sequencing of relevant exons of the MMR genes. Proven and obligate mutation carriers and first-degree relatives (FDRs) with a Lynch syndrome spectrum cancer were considered mutation carriers, as were a proportion of untested, unaffected FDRs based on the proportion of unaffected relatives testing positive in each age group. Kaplan–Meier analysis of risk to 70 years was calculated. One hundred and eighty-four Lynch syndrome spectrum extracolonic cancers in 839 proven, obligate, or assumed mutation carriers were analysed. Cumulative risk for females of an extracolonic tumour is 47.4% (95% CI 43.9–50.8). The risk to males is 26.5% (95% CI 22.6–30.4). There was no reduction in gynaecological malignancies due to gynaecological screening (examination, transvaginal ultrasound scan, hysteroscopy and endometrial biopsy). Males have a higher risk of gastric cancer than females (p = 0.0003). Gastric cancer risk in those born after 1935 does not justify surveillance. These penetrance estimates have been corrected for ascertainment bias and are appropriate for those referred to a high-risk clinic.     

Brain Cancer Risk and Electromagnetic Fields (EMFs): Assessing the Geomagnetic Component

Cancer cluster studies in North Carolina identified several communities in which there existed an elevated risk of brain cancer. These findings prompted a series of case-control studies. The current article, which originated from the results of the 3rd of such studies, is focused on inclusion of the earth's own geomagnetic fields that interact with electromagnetic fields generated from distribution power lines. This article also contains an assessment of the contribution of confounding by residential (e.g., urban, rural) and case characteristics (e.g., age, race, gender). Newly diagnosed brain cancer cases were identified for a 4-county region of central North Carolina, which the authors chose on the basis of the results of earlier observations. A 3:1 matched series of cancer cases from the same hospitals in which the cases were diagnosed served as the comparison group. Extensive geographic information was collected and was based on an exact place of residence at the time of cancer diagnosis, thus providing several strategic geophysical elements for assessment. The model for this assessment was based on the effects of these two sources of electromagnetic fields for an ion cyclotron resonance mechanism of disease risk. The authors used logistic regression models that contained the predicted value for the parallel component of the earth's magnetic field; these models were somewhat erratic, and the elements were not merged productively into a single statistical model. Interpretation of these values was difficult; therefore, the modeled values for the model elements, at progressive distances from the nearest power-line segments, are provided. The results of this study demonstrate the merits of using large, population-based databases, as well as using rigorous Geographic Information System techniques, for the assessment of ecologic environmental risks. The results also suggest promise for exposure classification that is compatible with the theoretical biological mechanisms posited for electromagnetic fields.     

Preliminary findings in the treatment of obstructive sleep apnea with transtracheal oxygen

The effects of continuous low flow oxygen via transtracheal oxygen delivery (TTOD) were assessed in four patients with obstructive sleep apnea (OSA) and daytime hypersomnolence who were unable to tolerate continuous positive nasal airway pressure (CPAP). The overall quality of sleep, sleep fragmentation, pattern of respiration, and nocturnal oxygen saturations were evaluated with the patients receiving 2 to 3 L/min of oxygen by TTOD, and the results were compared to polysomnograms with and without nasal cannula oxygen. The mean respiratory disturbance index (apneas plus hypopneas/hour of sleep) was improved by TTOD compared to no therapy or nasal cannula oxygen, and improvement in sleep disturbance was associated with improvement in overall nocturnal oxygen saturation. The mean apnea duration was not increased by TTOD and the duration of the longest apneic spells was decreased by 33 to 85% with this therapy. These improvements in respiratory status were accompanied by symptomatic improvement in daytime sleepiness, and there were no significant side effects. These findings suggest that TTOD may be a safe and effective alternative treatment of OSA for some patients who are unable to tolerate nasal CPAP therapy.     

Surgical management of traumatic intracerebral hematomas

Intraparenchymal lesions continue to contribute significantly to poor outcome in patients with head injury. This article elucidates the problems that must be dealt with in the management of these patients and develops guidelines that may be useful in making surgical decisions.     

Conserved properties of individual Ca2+-binding sites in calmodulin

Calmodulin (CaM) is a Ca²⁺-sensing protein that is highly conserved and ubiquitous in eukaryotes. In humans it is a locus of life-threatening cardiomyopathies. The primary function of CaM is to transduce Ca²⁺ concentration into cellular signals by binding to a wide range of target proteins in a Ca²⁺-dependent manner. We do not fully understand how CaM performs its role as a high-fidelity signal transducer for more than 300 target proteins, but diversity among its four Ca²⁺-binding sites, called EF-hands, may contribute to CaM’s functional versatility. We therefore looked at the conservation of CaM sequences over deep evolutionary time, focusing primarily on the four EF-hand motifs. Expanding on previous work, we found that CaM evolves slowly but that its evolutionary rate is substantially faster in fungi. We also found that the four EF-hands have distinguishing biophysical and structural properties that span eukaryotes. These results suggest that all eukaryotes require CaM to decode Ca²⁺ signals using four specialized EF-hands, each with specific, conserved traits. In addition, we provide an extensive map of sites associated with target proteins and with human disease and correlate these with evolutionary sequence diversity. Our comprehensive evolutionary analysis provides a basis for understanding the sequence space associated with CaM function and should help guide future work on the relationship between structure, function, and disease.Eukaryotes use Ca²⁺ in numerous intracellular signaling pathways. Calmodulin (CaM) is a highly versatile Ca²⁺ signaling protein that is essential for at least dozens of cellular processes in eukaryotic cells. In humans it binds to more than 300 targets (1–3). Humans have three genes that encode identical CaM proteins, but mutations in just one of the three copies can cause disease (4–8), as can altered gene expression (9). Although CaM has been extensively studied, many details about its function are still poorly understood. The high evolutionary conservation along with the wide range of targets brings up the question of how a single Ca²⁺-binding protein displays both selectivity and flexibility in the context of its various signaling pathways.CaM binds Ca²⁺ at four, nonidentical sites that contain the structural motif called an EF-hand (10, 11), each of which contains an acidic Ca²⁺-coordinating loop, or “EF-loop” (Fig. 1A). The EF-loop spans 12 amino acids and provides at least six oxygen atoms for coordinating Ca²⁺ (12). The coordinating oxygen atoms are provided by the side chains at the first, third, fifth, and 12th positions of the EF-loop, and an oxygen from a main chain carbonyl group is provided at the seventh position (10). Water molecules participate in the Ca² coordination geometry (13). CaM functions as a sensor over a broad range of Ca²⁺ signals that vary in amplitude, duration, and location. Although biophysical and evolutionary sequence studies have resulted in a general understanding of the bulk properties of EF-hand–binding sites, the implications of differences in Ca²⁺ affinity among the four EF-hands deserves a thorough investigation.Open in a separate windowFig. 1.(A) Example of a Ca²⁺-bound EF-hand structure from PDBID 1CLL. A cartoon of an EF-hand peptide chain threads through a semitransparent representation of its molecular surface. The surface is the interface between molecular atoms and solvent rendered in PyMOL. Only atoms nearest the Ca²⁺ are shown and are depicted as spheres—green for Ca²⁺ and red for oxygens. A Ca²⁺-coordinating water is depicted as a semitransparent red sphere. Helices are gray, and the EF-loop is tan. (B) Maximum likelihood branch lengths of CaM and tubulin constrained to match the species tree in Torruella et al. (40). This tree covers much of eukaryotic diversity. Holozoa and Holomycota include animals and fungi, respectively, and their closely related protist lineages. SARPAE is described in the text. Both proteins are highly constrained, but whereas tubulin’s rate has been fairly consistent across eukaryotes, CaM underwent a dramatic speed-up in Ascomycete fungi, which include the model system S. cerevisiae.Previous reports showed that the large family of EF-hand proteins likely arose from a founder protein with a single EF-hand in the most recent common ancestor of all extant eukaryotes (11, 14–18). Different EF-hand–containing proteins bind Ca²⁺ with different affinities, suggesting that a protein with multiple EF-hands, such as CaM, may bind Ca²⁺ with a different affinity at each site (19–28). It has therefore been suggested that CaM’s four sites display different affinities and perhaps cooperativity (29, 30). We therefore hypothesized that CaM’s four, nonidentical loops may generate some of their functional flexibility by binding Ca²⁺ using different physical properties and explored whether such differences could be discerned in the evolutionary record.Evolutionary analyses can provide mechanistic insight into how CaM is used as a Ca²⁺ sensor across eukaryotes. Prior work showed that the protein sequence of CaM is evolving at a faster pace in fungal species (11, 31–33), reflecting the fact that although CaM is essential in Saccharomyces cerevisiae, the cells can survive with all four EF-hands ablated (34). However, previous evolutionary studies focused on a small subset of eukaryotes, either because few sequences were available at the time of publication or because the study was focused on a particular lineage. The vast expansion of taxonomic coverage in sequence databases, and the recent availability of new NMR and X-ray crystal structures of CaM, therefore demands a more comprehensive analysis. Unfortunately, CaM is a small, ancient, and highly conserved protein and therefore does not contain enough information to infer phylogenetic tree topologies. Kretsinger and Nakayama and coworkers (11, 16, 17, 35), for instance, found little correspondence between phylogenies inferred from protein, DNA, or intron–exon structure.To overcome this hurdle, we used a variety of techniques to explore sequence and structural conservation in CaM across eukaryotes. Our approach allows us to address several key questions: (i) How fast is CaM diverging in different phyla? (ii) How does the function of a site, or its association with disease, correlate with sequence conservation? (iii) What properties of the EF-hands are conserved over deep evolutionary time, and how might this correspond to functional plasticity?     

Linkage of a familial platelet disorder with a propensity to develop myeloid malignancies to human chromosome 21q22.1-22.2

Linkage analysis was performed on a large pedigree with an autosomal dominant platelet disorder and a striking propensity in affected family members to develop hematologic malignancy, predominantly acute myelogenous leukemia. We report the linkage of the autosomal dominant platelet disorder to markers on chromosome 21q22. Four genetic markers completely cosegregate with the trait and yield maximum logarithm of difference scores ranging from 4.9 to 10.5 (theta = .001). Two flanking markers, D21S1265 and D21S167, define a critical region for the disease locus of 15.2 centimorgan. Further analysis of this locus may identify a gene product that affects platelet production and function and contributes to the molecular evolution of hematologic malignancy.     

Splenic lymphoma with villous lymphocytes involves B cells with extensively mutated Ig heavy chain variable region genes

Splenic lymphoma with villous lymphocytes (SLVL) is a recently defined subgroup of chronic B-cell lymphoproliferative diseases. The characteristic morphology of the tumor cells, together with phenotypic and cytogenetic findings, indicate that it is a distinct entity, but the nature of the cell or origin and its relationship to other low- grade lymphomas is unclear. For B-cell tumors, analysis of the variable region heavy chain (VH) genes used to encode the clonal Ig has shown marked differences between histologic categories, both in gene usage and extent of somatic mutation. An investigation of VH genes used in five typical cases of SLVL has shown somatic hypermutation from germline sequences in all cases, indicating that the cell of origin has been exposed to the hypermutation mechanism. However, no clonal heterogeneity was detectable, demonstrating that the tumor cell does not accumulate further mutations. These characteristics are similar to those found in mature postfollicular B cells, such as plasma cells. The distribution of mutations leading to replacement amino acids differed among the cases, with three of five cases showing clear evidence for antigen selection.     

Elevation of serum cystathionine levels in patients with cobalamin and folate deficiency

Homocysteine can be methylated to form methionine by the cobalamin- (Cbl) and folate-dependent enzyme, methionine synthase; serum levels of total homocysteine are elevated in greater than 95% of patients with either Cbl or folate deficiency. Homocysteine can also condense with serine to form cystathionine in a pyridoxal phosphate-dependent reaction catalyzed by cystathionine beta-synthase. Cystathionine is subsequently cleaved to cysteine and alpha-ketobutyrate by the pyridoxal phosphate-dependent enzyme gamma-cystathionase. To assess levels of cystathionine in Cbl and folate deficiency, we developed a new capillary gas chromatographic-mass spectrometric assay and measured cystathionine in the serum of normal subjects and patients with clinically confirmed deficiencies of these vitamins. The normal range for serum cystathionine was 65 to 301 nmol/L (median = 126 nmol/L) for 50 normal blood donors. In 30 patients with clinically confirmed Cbl deficiency, values for cystathionine ranged from 208 nmol/L to 2,920 nmol/L (median = 816 nmol/L) and 26 (87%) had levels above the normal range. In 20 patients with clinically confirmed folate deficiency, cystathionine concentrations ranged from 138 nmol/L to 4,150 nmol/L (median = 1,560 nmol/L) and 19 (95%) had values above the normal range. Five homozygotes for cystathionine beta-synthase deficiency had high values for serum-total homocysteine and low or low-normal values for serum cystathionine that ranged from 30 nmol/L to 114 nmol/L even though they were on treatment with pyridoxine and had partially responded. One patient with a defect in the synthesis of 5-CH3- tetrahydrofolate and five patients with defects in the synthesis of CH3- Cbl had high values for serum-total homocysteine and high values for cystathionine that ranged from 311 nmol/L to 1,500 nmol/L even though they were on treatment with folic acid and Cbl, respectively, and had partially responded. We conclude that levels of cystathionine are evaluated in the serum of most patients with Cbl and folate deficiency and that they are useful in the differential diagnosis of an elevated serum-total homocysteine level.