Regional protein expression in human Alzheimer's brain correlates with disease severity

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that currently affects 36 million people worldwide with no effective treatment available. Development of AD follows a distinctive pattern in the brain and is poorly modelled in animals. Therefore, it is vital to widen the spatial scope of the study of AD and prioritise the study of human brains. Here we show that functionally distinct human brain regions display varying and region-specific changes in protein expression. These changes provide insights into the progression of disease, novel AD-related pathways, the presence of a gradient of protein expression change from less to more affected regions and a possibly protective protein expression profile in the cerebellum. This spatial proteomics analysis provides a framework which can underpin current research and open new avenues to enhance molecular understanding of AD pathophysiology, provide new targets for intervention and broaden the conceptual frameworks for future AD research.

Stage and histology influence the relationship between MDM2 promoter polymorphism and esophageal cancer and overall survival (OS)

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Background: A single nucleotide polymorphism in the MDM2 promoter (SNP309) has been found to affect OS of advanced stage gastric adenocarcinoma (AD) and early stage squamous (SQ) cell carcinoma of the lung. The aim of this study was to evaluate the role of this polymorphism in the prognosis of esophageal cancer, another aerodigestive cancer. Methods: 150 early stage (E) and 118 locally advanced stage (LA) esophageal cancers were genotyped for MDM2 SNP309 using Taqman. The primary endpoint was overall survival (OS). Results: E disease: n=23 stage I; n=127 stage II. LA disease: n=93, Stage III; n=25, Stage IVA. AD comprised 215 (81%), while SQ comprised 45 (17%) of cases; 8 (3%) had poorly differentiated tumors. Median follow-up = 32 months. Median OS were 36 and 21 months for E and LA disease, respectively. Both histology and disease stage affected the relationship between SNP309 and esophageal cancer OS (see Table ). The wildtype T/T genotype conferred a worse OS in E patients (log-rank, p=0.03), especially those with AD (log-rank, p=0.003). In Cox proportional hazards interaction analyses, after adjusting for age, gender, stage and PS, there were statistically significant interactions between MDM2 SNP309 and disease stage (interaction p=0.004) and between MDM2 SNP309 and histologic subtype (AD vs. SQ)(interaction p=0.02). Thus, the direction of SNP309 association from our AD and E esophageal cancer patients are opposite to those of our SQ and LA esophageal cancer patients. However, our SQ and LA results are similar to the SQ lung cancer and advanced stage gastric cancers previously reported. This suggests that biologic mechanisms underpinning the prognostic role of SNP309 are dependent on extent of disease and histologic subtype. Conclusion: Histology and disease stage interact with the prognostic role of MDM2 SNP309 polymorphism in esophageal cancer OS.

[Table: see text]

No significant financial relationships to disclose.

A phase I and pharmacological study of the matrix metalloproteinase inhibitor BB-3644 in patients with solid tumours

BB-3644 is an oral, broad-spectrum matrix metalloproteinase inhibitor (MMPI) structurally related to marimastat and BB-94. It is also >10-fold more active than marimastat in inhibiting the processing of cell-bound TNF-alpha. Preclinical studies suggested a favourable toxicity profile when compared to marimastat, and therefore it was selected for clinical evaluation. Patients with advanced solid tumours against which established treatments had failed, or for which no satisfactory treatment exists and of good performance status, were eligible. Treatment consisted of twice daily (bd) oral BB-3644 for 84 days. The initial dose was 5 mg bd, and subsequent cohorts were treated with 10, 20 and 30 mg bd. In all, 22 patients were enrolled. The dose-limiting toxicity (DLT) was musculoskeletal pain. For 28 days of treatment with BB-3644, 20 mg bd was the maximum tolerated dose (MTD), as at 30 mg bd, six of nine patients developed significant musculoskeletal toxicity by day 28. Following chronic oral dosing (>28 days) with BB-3644, three of five patients treated at 10 mg bd developed musculoskeletal DLT by day 84, defining the MTD as 5 mg bd. As dose-limiting musculoskeletal toxicity was encountered at doses of BB-3644 unlikely to provide an advantage over currently available MMPIs, further evaluation is not recommended.

A common binding site on the microsomal triglyceride transfer protein for apolipoprotein B and protein disulfide isomerase

The assembly of triglyceride-rich lipoproteins requires the formation in the endoplasmic reticulum of a complex between apolipoprotein B (apoB), a microsomal triglyceride transfer protein (MTP), and protein disulfide isomerase (PDI). In the MTP complex, the amino-terminal region of MTP (residues 22-303) interacts with the amino-terminal region of apoB (residues 1-264). Here, we report the identification and characterization of a site on apoB between residues 512 and 721, which interacts with residues 517-603 of MTP. PDI binds in close proximity to this apoB binding site on MTP. The proximity of these binding sites on MTP for PDI and amino acids 512-721 of apoB was evident from studies carried out in a yeast two-hybrid system and by co-immunoprecipitation. The expression of PDI with MTP and apoB16 (residues 1-721) in the baculovirus expression system reduced the amount of MTP co-immunoprecipitated with apoB by 73%. The interaction of residues 512-721 of apoB with MTP facilitates lipoprotein production. Mutations of apoB that markedly reduced this interaction also reduced the level of apoB-containing lipoprotein secretion.

The structure of vitellogenin provides a molecular model for the assembly and secretion of atherogenic lipoproteins

The assembly of atherogenic lipoproteins requires the formation in the endoplasmic reticulum of a complex between apolipoprotein (apo)B, a microsomal triglyceride transfer protein (MTP) and protein disulphide isomerase (PDI). Here we show by molecular modelling and mutagenesis that the globular amino-terminal regions of apoB and MTP are closely related in structure to the ancient egg yolk storage protein, vitellogenin (VTG). In the MTP complex, conserved structural motifs that form the reciprocal homodimerization interfaces in VTG are re-utilized by MTP to form a stable heterodimer with PDI, which anchors MTP at the site of apoB translocation, and to associate with apoB and initiate lipid transfer. The structural and functional evolution of the VTGs provides a unifying scheme for the invertebrate origins of the major vertebrate lipid transport system.

[Nonhistone chromosome proteins HMG1 and HMG2 stabilize one of the sequence-specific complexes, formed on the promotor of human retroposons of the ALU-family of other nuclear proteins]

Human retroposons of the Alu family have an internal promoter for RNA polymerase III also present in tRNA genes, but Alu are poorly transcribed by this polymerase in somatic cells in vivo, which is probably due to an efficient system of repression of the Alu transcription. The key control promoter element of the tRNA genes, known as B-box, binds basal transcription factor TFIIIC2, which initiates assembly of the full transcription complex. Previously we identified several human nuclear factors which bind to Alu Subregion covering B-box and the adjacent sequences, which can be involved in repression of Alu transcription. In this study we identified one factor, F1, as HMF1/2 and another factor, F2, as TFIIIC2-like protein reacting with B-box. Both the factors are not alu-specific, whereas the third identified Alu-binding factor, F3, seems to be specific for the Alu-specific subsequence located just downstream from B-box and can discriminate evolutionary "young" and "old" Alu subfamilies producing different numbers of transcripts in vivo. Although HMG1/2 binds to Alu in a sequence-unspecific manner, the proteins are capable of stabilizing the sequence-specific complex F3 which can be functionally significant. We believe that the factors binding to Alu B-box subregion interfere somehow with the functions of the basal factor TFIIIC2 and, hence, can be co-repressors of Alu transcription by RNA polymerase III.

Acquired Brown's syndrome: an unusual cause

A 62-year-old man with acquired Brown's syndrome is presented. This was due to an orbital metastatic deposit, a cause not previously reported. Other causes of this disorder and its treatment are discussed.