Non-Amyloid Approaches to Disease Modification for Alzheimer's Disease: An EU/US CTAD Task Force Report

While amyloid-targeting therapies continue to predominate in the Alzheimer’s disease (AD) drug development pipeline, there is increasing recognition that to effectively treat the disease it may be necessary to target other mechanisms and pathways as well. In December 2019, The EU/US CTAD Task Force discussed these alternative approaches to disease modification in AD, focusing on tau-targeting therapies, neurotrophin receptor modulation, anti-microbial strategies, and the innate immune response; as well as vascular approaches, aging, and non-pharmacological approaches such as lifestyle intervention strategies, photobiomodulation and neurostimulation. The Task Force proposed a general strategy to accelerate the development of alternative treatment approaches, which would include increased partnerships and collaborations, improved trial designs, and further exploration of combination therapy strategies.

Abstract 1552: Image-based microchip sorting of pure, immuno-phenotypically defined subpopulations of tumor cells from tiny formalin-fixed paraffin embedded (FFPE) samples reveals their distinct genetic features

Background: We provide a solution of pressing needs in preparation of FFPE samples for genomic analysis: small sample size, unwanted admixture of normal cells, analysis of tumor rare-cell subpopulations present at low percentages in the tumor fraction.

Methods: We disaggregated into cell suspensions archival FFPE samples from 12 ovarian, pancreatic and lung cancer patients, staining for Vimentin, Keratin and DNA. We sorted by DEPArray™ precise numbers (mean = 107, median 58, range = 5-600) of pure homogenous cells from the major population of tumor cells, the contaminant diploid stromal cells, and other minority tumor cell types indicative of epithelial-to-mesenchymal transition (EMT). Using IonTorrent AmpliSeq CHPv2, we generated sequencing libraries, after lysis of the pure cells recovered by DEPArray™ (n = 54), or unsorted samples (either QIAmp DNA columns or disaggregated cells). Libraries were sequenced with IonTorrent PGM (mean depth>2,000x), and analyzed using IonTorrent software.

Results: On several loci, we detected somatic mutations with 100% variant frequency, only observable as heterozygous in the unsorted samples and as wild-type in stromal cells of same patient, confirming 100% purity of sorted cells. Moreover, in the EMT-phenotype subpopulations we identified clear somatic mutations, different from tumor cells majority and undetectable in unsorted samples. Frequently, for loci harboring germ-line heterozygous SNPs with variant frequency around 50% for pure stromal cells, we readily detected loss-of-heterozygosis in tumor cells subpopulations as binary (0%/100%) variants. Quantitative traits such as copy number gains and losses were also reproducibly identified in tumor cell replicates as deviations from the 50% variant frequency of germline SNPs of pure stromal cells. Furthermore, we observed an excellent coverage uniformity (mean = 96%) for recoveries (n = 27) in the range of 81-600 cells, even higher than the uniformity obtained with (n = 2) QIAmp-purified DNA (92%). Mean uniformity gradually decreased to 89% for cell recoveries (n = 13) in the range 21-80, and further decreased to 70% for lower cell numbers (n = 14).

Highlights: Sorting tumor rare-cell subpopulations reveals their genetic characteristics, undetectable in unsorted samples. Analyzing homogenous cell subpopulations boosts signal-to-noise ratio working around inherent sensitivity/specifitiy trade-offs of rare-variant calls. The proposed workflow further enables reliable detection of quantitative traits such as CNVs. Sorting pure stromal cells yields internal controls for archival samples.

Citation Format: Chiara Bolognesi, Anna Doffini, Genny Buson, Rossana Lanzellotto, Giulio Signorini, Valeria Sero, Alex Calanca, Francesca Fontana, Rita Romano, Stefano Gianni, Giulia Bregola, Gianni Medoro, Raimo Tanzi, Giuseppe Giorgini, Hans Morreau, Massimo Barberis, Willem E. Corver, Nicolo Manaresi. Image-based microchip sorting of pure, immuno-phenotypically defined subpopulations of tumor cells from tiny formalin-fixed paraffin embedded (FFPE) samples reveals their distinct genetic features. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1552. doi:10.1158/1538-7445.AM2015-1552

MRI measures of entorhinal cortex vs hippocampus in preclinical AD

BACKGROUND

MRI measures of the entorhinal cortex and the hippocampus have been used to predict which nondemented individuals with memory problems will progress to meet criteria for AD on follow-up, but their relative accuracy remains controversial.

OBJECTIVES

To compare MRI measures of the entorhinal cortex and the hippocampus for predicting who will develop AD.

METHODS

MRI volumes of the entorhinal cortex and the hippocampus were obtained in 137 individuals comprising four groups: 1) individuals with normal cognition both at baseline and after 3 years of follow-up (n = 28), 2) subjects with memory difficulty but not dementia both at baseline and after 3 years of follow-up (n = 73), 3) subjects with memory difficulty at baseline who were diagnosed with probable AD within 3 years of follow-up (n = 21), and 4) patients with mild AD at baseline (n = 16).

RESULTS

Measures of both the entorhinal cortex and the hippocampus were different for each of the pairwise comparisons between the groups (p < 0.001) and were correlated with tests of memory (p < 0.01). However, the volume of the entorhinal cortex differentiated the subjects from those destined to develop dementia with considerable accuracy (84%), whereas the measure of the hippocampus did not.

CONCLUSION

These findings are consistent with neuropathologic data showing substantial involvement of the entorhinal cortex in the preclinical phase of AD and suggest that, as the disease spreads, atrophic change develops within the hippocampus, which is measurable on MRI.

Preclinical prediction of AD using neuropsychological tests

Normals (N = 42) and patients with mild memory difficulty (N = 123) were given a neuropsychological test battery, and then followed annually for 3 years to determine which individuals developed sufficient functional change that they met clinical criteria for AD. Twenty-three of the 123 participants with mild memory difficulty converted to a diagnosis of probable Alzheimer's disease (AD) within 3 years of follow-up. Four of the 20 neuropsychological measures obtained at baseline, were useful in discriminating the groups on the basis of their status 3 years after the tests were given. The 4 discriminating tests pertained to assessments of memory and executive function. When the controls were compared to the individuals with memory impairments who ultimately developed AD (the converters), the accuracy of discrimination was 89%, based on the neuropsychological measures at baseline. The discrimination of the controls from the individuals with mild memory problems who did not progress to the point where they met clinical criteria for probable AD over the 3 years of follow-up (the Questionables) was 74% and the discrimination of the questionables from the converters was 80%. The specific tests that contributed to these discriminations, in conjunction with recent neuropathological and neuroimaging data from preclinical cases, have implications for which brain regions may be affected during the prodromal phase of AD.

No evidence for genetic association or linkage of the cathepsin D (CTSD) exon 2 polymorphism and Alzheimer disease

Two recent case-control studies have suggested a strong association of a missense polymorphism in exon 2 of the cathepsin D gene (CTSD) and Alzheimer disease (AD). However, these findings were not confirmed in another independent study. We analyzed this polymorphism in two large and independent AD study populations and did not detect an association between CTSD and AD. The first sample was family-based and included 436 subjects from 134 sibships discordant for AD that were analyzed using the sibship disequilibrium test (SDT, p = 0.68) and the sib transmission/disequilibrium test (Sib-TDT, p = 0.81). The second sample of 200 AD cases and 182 cognitively normal controls also failed to show significant differences in the allele or genotype distribution in cases versus controls (chi2, p = 0.91 and p = 0.88, respectively). In addition, two-point linkage analyses in an enlarged family sample (n = 670) did not show evidence for linkage of the chromosomal region around CTSD. Thus, our analyses on more than 800 subjects suggest that if an association between the CTSD exon 2 polymorphism and AD exists, it is likely to be smaller than previously reported.

Candidate genes showing no evidence for association or linkage with Alzheimer's disease using family-based methodologies

Alzheimer's disease (AD) is a genetically complex and heterogeneous disorder. To date, a large number of candidate genes have been associated with the disease, however none of these findings has been consistently replicated in independent datasets. In this study we report the results of family-based analyses for polymorphisms of five such candidates on chromosomes 2 (interleukin-1beta, IL-1B), 3 (butyrylcholinesterase, BCHE), 11 (cathepsin D, CTSD; Fe65, APBB1) and 12 (lipoprotein receptor-related protein-1, LRP1) that were all suggested to be associated with AD in recent case-control studies. To minimize the possibility of spurious findings due to population admixture, we used a family-based design applying the sibship disequilibrium test (SDT) as well as two-point parametric linkage analyses on families from the National Institute of Mental Health (NIMH) Genetics Initiative. Contrary to the initial reports, none of the polymorphisms that were analyzed showed evidence for association or linkage with AD in our families. Our results suggest that the previously reported associations from case-control studies are either (a) false positive results, e.g. due to type I error or population admixture, (b) smaller than initially proposed, or (c) due to linkage disequilibrium with an as yet unidentified polymorphism nearby.

Use of structural magnetic resonance imaging to predict who will get Alzheimer's disease

We used magnetic resonance imaging (MRI) measurements to determine whether persons in the prodromal phase of Alzheimer's disease (AD) could be accurately identified before they developed clinically diagnosed dementia. Normal subjects (n = 24) and those with mild memory difficulty (n = 79) received an MRI scan at baseline and were then followed annually for 3 years to determine which individuals subsequently met clinical criteria for AD. Patients with mild AD at baseline were also evaluated (n = 16). Nineteen of the 79 subjects with mild memory difficulty "converted" to a diagnosis of probable AD after 3 years of follow-up. Baseline MRI measures of the entorhinal cortex, the banks of the superior temporal sulcus, and the anterior cingulate were most useful in discriminating the status of the subjects on follow-up examination. The accuracy of discrimination was related to the clinical similarity between groups. One hundred percent (100%) of normal subjects and patients with mild AD could be discriminated from one another based on these MRI measures. When the normals were compared with the individuals with memory impairments who ultimately developed AD (the converters), the accuracy of discrimination was 93%, based on the MRI measures at baseline (sensitivity = 0.95; specificity = 0.90). The discrimination of the normal subjects and the individuals with mild memory problems who did not progress to the point where they met clinical criteria for probable AD over the 3 years of follow-up (the "questionables") was 85% and the discrimination of the questionables and converters was 75%. The apolipoprotein E genotype did not improve the accuracy of discrimination. The specific regions selected for each of these discriminations provides information concerning the hierarchical fashion in which the pathology of AD may affect the brain during its prodromal phase.

Focal malakoplakia in chronic periapical periodontitis

AIMS

Three cases of chronic periapical periodontitis including focal areas with malakoplakia changes are reported.

METHODS AND RESULTS

These areas included both von Hansemann-type macrophages and periodic acid-Schiff-positive, iron- and calcium-containing concretions. Some concretions corresponded to spherules with a targetoid configuration, thus fitting the morphological criteria for classical Michaelis-Gutmann bodies.

CONCLUSION

The vast majority of the cases of malakoplakia that have been reported in the literature corresponded to a characteristic, fairly homogeneous lesion, but a few instances of focal malakoplakia have been described in various chronic conditions. These considerations support the opinion that the local conditions for the production of Michaelis-Gutmann bodies may occur focally in diseases characterized by macrophage accumulation.

G-cell density in the antral mucosa: a feasibility study

In this work a new method for gastrin-secreting cell (G-cell) density measurement was employed in order to test the hypothesis that G-cell density of the antral mucosa can be estimated with an acceptable degree of error. The zone of antral mucosa where most G-cells are located was demarcated, its area was measured and the G-cells within this area were counted. The variation in the e error of the estimate according to normal distribution theory, and the size of the sampling expected to yield G-cell density values with a given error were assessed. Our data indicate that a very large surface of the G-cell zone should be explored in order to estimate G-cell density with an acceptable degree of error. G-cell density measurement appears not to be feasible on biopsy specimens or, for routine diagnosis, on gastrectomy specimens.

ApoE-4 and age at onset of Alzheimer's disease: the NIMH genetics initiative

OBJECTIVE

To explore the impact of apoE-4 on Alzheimer's disease (AD) and its age at onset.

DESIGN

A genetic linkage study using affected relative pairs, predominantly siblings.

SETTING

Three academic medical centers ascertained subjects from memory disorder clinics, nursing homes, and the local community.

SUBJECTS

310 families including 679 subjects with AD by NINCDS/ADRDA and/or Khachaturian criteria and 231 unaffected subjects.

OUTCOME MEASURE

ApoE genotype. ANALYTIC METHODS: Association, affected pedigree member, sibling pair, and lod score analyses.

RESULTS

ApoE-4 was strongly associated with AD in this sample (allele frequency = 0.46 vs. 0.14 in controls, p < 0.000001). Results of lod score, affected pedigree member analysis, and sib-pair analysis also supported apoE-4 as a risk factor for AD. When the sample was stratified on family mean age at onset, the risk conferred by apoE-4 was most marked in the 61 to 65 age group. Individuals with two copies of apoE-4 had a significantly lower age at onset than those with one or no copies (66.4 vs. 72.0, p < 0.001), but individuals with one copy did not differ from those with none. Within families, the individual with the earliest age at onset had, on average, significantly more apoE-4 alleles (p < 0.0001) than the individual with the latest onset.

DISCUSSION

This work supports previous reports of an association between apoE-4 and the development of AD and demonstrates that apoE-4 exerts its maximal effect before age 70. These findings have important implications for the potential use of apoE genotyping for diagnosis and prediction of disease. They also underscore the need to identify additional genetic factors involved in AD with onset beyond age 70 years.

Secreted amyloid beta-protein similar to that in the senile plaques of Alzheimer's disease is increased in vivo by the presenilin 1 and 2 and APP mutations linked to familial Alzheimer's disease

To determine whether the presenilin 1 (PS1), presenilin 2 (PS2) and amyloid beta-protein precursor (APP) mutations linked to familial Alzheimer's disease (FAD) increase the extracellular concentration of amyloid beta-protein (A beta) ending at A beta 42(43) in vivo, we performed a blinded comparison of plasma A beta levels in carriers of these mutations and controls. A beta 1-42(43) was elevated in plasma from subjects with FAD-linked PS1 (P < 0.0001), PS2N1411 (P = 0.009), APPK670N,M671L (P < 0.0001), and APPV7171 (one subject) mutations. A beta ending at A beta 42(43) was also significantly elevated in fibroblast media from subjects with PS1 (P < 0.0001) or PS2 (P = 0.03) mutations. These findings indicate that the FAD-linked mutations may all cause Alzhelmer's disease by increasing the extracellular concentration of A beta 42(43), thereby fostering cerebral deposition of this highly amyloidogenic peptide.

Analysis of the c-FOS gene on chromosome 14 and the promoter of the amyloid precursor protein gene in familial Alzheimer's disease

The c-FOS gene product, a putative transacting transcriptional regulator of the amyloid precursor protein (APP) gene, is a candidate locus for the familial Alzheimer's disease (FAD) mutation on chromosome 14 (FAD14). In light of this functional relationship, we investigated the nucleotide sequence and segregation of c-FOS and the nucleotide sequence of the 5' APP promoter. Single-stranded conformational polymorphisms (SSCPs) in the c-FOS gene revealed that c-FOS closely cosegregates with the FAD14 gene but does not show allelic association with FAD. A conservative third-position T-->C mutation was demonstrated in exon 2 (codon 84) of c-FOS, and a C-->G substitution was detected at -209 bp in the 5' promoter of APP. Neither were unique to FAD and are unlikely to be pathogenic or secondary modifiers of the FAD phenotype. We conclude that the c-FOS open reading frame is probably not the site of the FAD14 locus, but we cannot exclude the existence of modifier loci on chromosome 21.

Genetic heterogeneity of gene defects responsible for familial Alzheimer disease

Inherited Alzheimer's disease is a genetically heterogeneous disorder that involves gene defects on at least five chromosomal loci. Three of these loci have been found by genetic linkage studies to reside on chromosomes 21, 19, and 14. On chromosomes 21, the gene encoding the precursor protein of Alzheimer-associated amyloid (APP) has been shown to contain several mutations in exons 16 and 17 which account for roughly 2-3% of familial Alzheimer's disease (FAD). The other loci include what appears to be a susceptibility gene on chromosome 19 associated with late-onset (> 65 years) FAD, and a major early-onset FAD gene defect on the long arm of chromosome 14. In other early- and late-onset FAD kindreds, the gene defects involved do not appear to be linked to any of these three loci, indicating the existence of additional and as of yet unlocalized FAD genes. This review provides a historical perspective of the search for FAD gene defects and summarizes the progress made in world-wide attempts to isolate and characterize the genes responsible for this disorder.

Genetic evidence for a novel familial Alzheimer's disease locus on chromosome 14

Familial Alzheimer's disease (FAD) has been shown to be genetically heterogeneous, with a very small proportion of early onset pedigrees being associated with mutations in the amyloid precursor protein (APP) gene on chromosome 21, and some late onset pedigrees showing associations with markers on chromosome 19. We now provide evidence for a major early onset FAD locus on the long arm of chromosome 14 near the markers D14S43 and D14S53 (multipoint lod score z = 23.4) and suggest that the inheritance of FAD may be more complex than had initially been suspected.

A novel but non-pathogenic mutation in exon 4 of the human amyloid precursor protein (APP) gene

Mutations in the beta-amyloid precursor protein (APP) gene have been associated with both familial Alzheimer disease (FAD) and with hereditary cerebral haemorrhage. The polymerase chain reaction was used to both amplify and sequence exon 4 of the APP gene from genomic DNA of subjects with FAD and normal control subjects. A novel, rare, conservative DNA sequence variant was discovered at nucleotide 459 of codon 153 (valine) in exon 4 of the APP gene in an affected member of a large FAD pedigree. Segregation studies indicate that this mutation is likely to be non-pathogenic, but must be recognized and discriminated from pathogenic mutations during sequencing studies of the APP gene in patients with FAD.

Screening for mutations in the open reading frame and promoter of the beta-amyloid precursor protein gene in familial Alzheimer's disease: identification of a further family with APP717 Val-->Ile

Following the identification of mutations in the beta-amyloid precursor protein (APP) gene in familial, early onset Alzheimer's disease (AD), we have developed a screening protocol using single strand conformation analysis (SSCA) to screen exon 17 for the known mutations within APP. In addition, we used this protocol to screen the other seventeen exons of APP and a three hundred and thirty base pair regulatory region of the promoter for new mutations in 9 families with early onset AD. Exons 16 and 17, which encode the deposited beta-amyloid peptide, were screened in a further 10 families. Our screening procedure identifies all the reported mutations within APP. While we have identified a further family with APP717 Val-->Ile, we did not find any previously undescribed mutations. Screening of other exons of APP in 2 families in which we have previously reported mutations at APP717, failed to reveal other sequence abnormalities supporting the hypothesis that the mutations at APP717 cause the disease in these families. These data suggest that mutations in APP are a rare cause of familial early onset AD (3/21 families tested) and that within APP most, possibly all, mutations which cause AD are in exon 17.

Prognostic value of the immunocytochemical detection of extramural venous invasion in Dukes' C colorectal adenocarcinomas. A preliminary study

In postsurgical staging of colorectal adenocarcinomas, it is sometimes difficult to determine the range of possible venous spread. Distinguishing between the extramural veins (especially when the neoplastic embolus takes up the whole lumen and the endothelium cannot be identified) and the smallest extramural lymph nodes (when they are completely replaced by metastatic carcinoma, leaving the capsule alone) is also difficult. This work proposes a more precise definition of true venous invasion to improve histopathologic staging. Immunohistochemical techniques employing commercial antibodies against Factor VIII RAG, with and without enzymatic digestion, and UEA I lectin for residual endothelium detection, were applied, as well as antibodies against vimentin, desmin, and alpha sm-1 actin to detect wall components. The immunohistochemical evaluation of colorectal adenocarcinomas, in particular by anti-alpha sm-1 actin antibodies, permitted a reliable morphologic distinction of the true venous invasion. This factor proved to be relevant for survival rate prediction.

Irradiation-reduced human chromosome 21 hybrids

Rodent-human somatic cell hybrids have been constructed which contain fragments of human chromosome 21 as their only human material. This was done by irradiating rodent-human somatic cell hybrids containing a complete chromosome 21 to fragment the genome and then rescuing human GAR synthetase and various amounts of flanking chromosome 21 DNA by fusing with GAR synthetase-deficient hamster cells and selecting for growth in purine-free medium. Four irradiation-reduction hybrids were produced by this method and contain the distal, proximal, and central portions of the long arm of human chromosome 21, all centered about GAR synthetase. These irradiation-reduction hybrids were used as a panel to regionally map single-copy and individual copies of repetitive sequences. Using these hybrids along with another independently constructed hybrid, the GAR synthetase gene was mapped distal to SOD-1 and proximal to CP21G1(D21S60). Of special interest is the regional mapping of the gene for the amyloid beta-protein distal to pPW236B(D21S11) and proximal to SOD-1.

Trisomy 21 (Down syndrome): studying nondisjunction and meiotic recombination by using cytogenetic and molecular polymorphisms that span chromosome 21

By combining molecular and cytogenetic techniques, we demonstrated the feasibility and desirability of a comprehensive approach to analysis of nondisjunction for chromosome 21. We analyzed the parental origin and stage of meiotic errors resulting in trisomy 21 in each of five families by successfully using cytogenetic heteromorphisms and DNA polymorphisms. The 16 DNA fragments used to detect polymorphisms spanned the length of the long arm and detected recombinational events on nondisjoined chromosomes in both maternal meiosis I and maternal meiosis II errors. The meiotic stage at which errors occurred was determined by sandwiching the centromere between cytogenetic heteromorphisms on 21p and an informative haplotype constructed using two polymorphic DNA probes that map to 21q just below the centromere. This study illustrates the necessity of combining cytogenetic polymorphisms on 21p with DNA polymorphisms spanning 21q to determine (1) the source and stage of meiotic errors that lead to trisomy 21 and (2) whether an association exists between nondisjunction and meiotic recombination.

A morphometric study of cystadenolymphoma (Warthin's tumor)

This work is concerned with a morphometric analysis of cystadenolymphoma (CAL, Warthin's tumor), a growth generally found in the parotid gland. CAL is composed of various amounts of epithelium-lined cysts and of lymphoid stroma. Our results support the notion that the epithelium is the proliferating component in CAL. They also challenge the idea that CAL is a tumor, because its growth is slow and self-limiting, and occurs in a restricted space.

O-acetylated sialic acid variants in intestinal glandular metaplasia of the urinary tract

Two cases of chronic cystitis, two of chronic ureteritis, one of chronic pyelitis and two transitional cell carcinomas of the urinary tract showed glandular metaplasia or focal mucin production. Positive staining for O-acetylated sialic acid variants (sites 7 and 8) detected by the PB-KOH-PAS method was found in the two cases of cystitis, in one of chronic ureteritis and in one of chronic pyelitis. Positive staining was observed only in areas showing an intestinal type of metaplasia and in which goblet cells and argyrophil cells were also identified. These findings taken together with earlier studies on ovarian cystadenomas lead the authors to believe that O-acetylated variants are markers of an intestinal type of epithelium. Evaluation of O-acetylated sialomucins may be useful in further studies on the histogenesis of primary adenocarcinomas of the bladder.

Linkage analysis in a family with dominantly inherited torsion dystonia: exclusion of the pro-opiomelanocortin and glutamic acid decarboxylase genes and other chromosomal regions using DNA polymorphisms

A search for the defective gene causing torsion dystonia has been carried out in a family manifesting an autosomal dominant mode of inheritance of this movement disorder. Complete neurologic examination and establishment of lymphoblast lines have been carried out for over 50 members. Linkage analysis, using cloned DNA sequences and restriction fragment length polymorphisms, was evaluated by the LOD score method with requisite assumptions for mode of inheritance, age-of-onset and incomplete gene penetrance. Genes for pro-opiomelanocortin and glutamic acid decarboxylase, which have been implicated in the etiology of the disease in rat models, were excluded as being responsible for the disease state in this family. Other regions of the genome were also excluded using DNA probes for other genes and random "unique" sequences.

Primary signet-ring carcinoma of the large bowel. Report of nine cases

Nine cases of signet-ring carcinoma have been observed from among 800 consecutive histologic cases diagnosed as adenocarcinoma of the colon during a period of 10 years (0.9%). This group of nine patients (Group A) has been matched for sex, age, and stage with a group of 45 patients affected by ordinary carcinoma of the colon (Group B). Clinical and histologic parameters, including symptoms, primary tumor site, free interval from primary surgery, histochemical investigation of intracytoplasmic mucins, and survival, were evaluated. The results of this investigation showed no clinical differences between signet-ring carcinoma and ordinary carcinoma, and no statistically significant results were observed regarding the frequency of local recurrence and actuarial survival.

Primary signet-ring carcinoma of the large bowel. Report of nine cases

Nine cases of signet-ring carcinoma have been observed from among 800 consecutive histologic cases diagnosed as adenocarcinoma of the colon during a period of 10 years (0.9%). This group of nine patients (Group A) has been matched for sex, age, and stage with a group of 45 patients affected by ordinary carcinoma of the colon (Group B). Clinical and histologic parameters, including symptoms, primary tumor site, free interval from primary surgery, histochemical investigation of intracytoplasmic mucins, and survival, were evaluated. The results of this investigation showed no clinical differences between signet-ring carcinoma and ordinary carcinoma, and no statistically significant results were observed regarding the frequency of local recurrence and actuarial survival.

Genetic linkage between Huntington's disease and the DNA polymorphism G8 in South Wales families

Analysis of the polymorphism shown by the DNA probe G8 in eight South Wales families with Huntington's disease has confirmed close genetic linkage between this marker and the disorder, the most likely genetic distance being two centimorgans (cM). The closeness of the linkage suggests that G8 may have clinical applications in genetic prediction for this condition.