Atrophy rates in asymptomatic amyloidosis: implications for Alzheimer prevention trials

There is considerable interest in designing therapeutic studies of individuals at risk of Alzheimer disease (AD) to prevent the onset of symptoms. Cortical β-amyloid plaques, the first stage of AD pathology, can be detected in vivo using positron emission tomography (PET), and several studies have shown that ~1/3 of healthy elderly have significant β-amyloid deposition. Here we assessed whether asymptomatic amyloid-PET-positive controls have increased rates of brain atrophy, which could be harnessed as an outcome measure for AD prevention trials. We assessed 66 control subjects (age = 73.5±7.3 yrs; MMSE = 29±1.3) from the Australian Imaging Biomarkers & Lifestyle study who had a baseline Pittsburgh Compound B (PiB) PET scan and two 3T MRI scans ~18-months apart. We calculated PET standard uptake value ratios (SUVR), and classified individuals as amyloid-positive/negative. Baseline and 18-month MRI scans were registered, and brain, hippocampal, and ventricular volumes and annualized volume changes calculated. Increasing baseline PiB-PET measures of β-amyloid load correlated with hippocampal atrophy rate independent of age (p = 0.014). Twenty-two (1/3) were PiB-positive (SUVR>1.40), the remaining 44 PiB-negative (SUVR≤1.31). Compared to PiB-negatives, PiB-positive individuals were older (76.8±7.5 vs. 71.7±7.5, p<0.05) and more were APOE4 positive (63.6% vs. 19.2%, p<0.01) but there were no differences in baseline brain, ventricle or hippocampal volumes, either with or without correction for total intracranial volume, once age and gender were accounted for. The PiB-positive group had greater total hippocampal loss (0.06±0.08 vs. 0.02±0.05 ml/yr, p = 0.02), independent of age and gender, with non-significantly higher rates of whole brain (7.1±9.4 vs. 4.7±5.5 ml/yr) and ventricular (2.0±3.0 vs. 1.1±1.0 ml/yr) change. Based on the observed effect size, recruiting 384 (95%CI 195-1080) amyloid-positive subjects/arm will provide 80% power to detect 25% absolute slowing of hippocampal atrophy rate in an 18-month treatment trial. We conclude that hippocampal atrophy may be a feasible outcome measure for secondary prevention studies in asymptomatic amyloidosis.

Longitudinal neuroimaging and neuropsychological profiles of frontotemporal dementia with C9ORF72 expansions

INTRODUCTION

Frontotemporal dementia (FTD) is a common cause of early-onset dementia with a significant genetic component, as underlined by the recent identification of repeat expansions in the gene C9ORF72 as a major cause of FTD and motor neuron disease. Understanding the neurobiology and clinical phenomenology of this novel mutation is currently a major research focus. However, few data are available concerning the longitudinal evolution of this genetic disease. Here we present longitudinal neuropsychological and neuroimaging data on a cohort of patients with pathological repeat expansions in C9ORF72.

METHODS

Following a review of the University College London FTD DNA database, 20 cases were retrospectively identified with a C9ORF72 expansion. Twelve cases had longitudinal neuropsychology data available and six of these cases also had longitudinal volumetric brain magnetic resonance imaging. Cortical and subcortical volumes were extracted using FreeSurfer. Rates of whole brain, hemispheric, cerebellar and ventricular change were calculated for each subject. Nonlinear fluid registration of follow-up to baseline scan was performed to visualise longitudinal intra-subject patterns of brain atrophy and ventricular expansion.

RESULTS

Patients had low average verbal and performance IQ at baseline that became impaired (< 5th percentile) at follow-up. In particular, visual memory, naming and dominant parietal skills all showed deterioration. Mean rates of whole brain atrophy (1.4%/year) and ventricular expansion (3.2 ml/year) were substantially greater in patients with the C9ORF72 mutation than in healthy controls; atrophy was symmetrical between the cerebral hemispheres within the C9ORF72 mutation group. The thalamus and cerebellum showed significant atrophy whereas no cortical areas were preferentially affected. Longitudinal fluid imaging in individual patients demonstrated heterogeneous patterns of progressive volume loss; however, ventricular expansion and cerebellar volume loss were consistent findings.

CONCLUSION

Disease evolution in C9ORF72-associated FTD is linked neuropsychologically with increasing involvement of parietal and amnestic functions, and neuroanatomically with rather diffuse and variable cortical and central atrophy but more consistent involvement of the cerebellum and thalamus. These longitudinal profiles are consistent with disease spread within a distributed subcortical network and demonstrate the feasibility of longitudinal biomarkers for tracking the evolution of the C9ORF72 mutation phenotype.

Frontotemporal dementia with the C9ORF72 hexanucleotide repeat expansion: clinical, neuroanatomical and neuropathological features

An expanded hexanucleotide repeat in the C9ORF72 gene has recently been identified as a major cause of familial frontotemporal lobar degeneration and motor neuron disease, including cases previously identified as linked to chromosome 9. Here we present a detailed retrospective clinical, neuroimaging and histopathological analysis of a C9ORF72 mutation case series in relation to other forms of genetically determined frontotemporal lobar degeneration ascertained at a specialist centre. Eighteen probands (19 cases in total) were identified, representing 35% of frontotemporal lobar degeneration cases with identified mutations, 36% of cases with clinical evidence of motor neuron disease and 7% of the entire cohort. Thirty-three per cent of these C9ORF72 cases had no identified relevant family history. Families showed wide variation in clinical onset (43-68 years) and duration (1.7-22 years). The most common presenting syndrome (comprising a half of cases) was behavioural variant frontotemporal dementia, however, there was substantial clinical heterogeneity across the C9ORF72 mutation cohort. Sixty per cent of cases developed clinical features consistent with motor neuron disease during the period of follow-up. Anxiety and agitation and memory impairment were prominent features (between a half to two-thirds of cases), and dominant parietal dysfunction was also frequent. Affected individuals showed variable magnetic resonance imaging findings; however, relative to healthy controls, the group as a whole showed extensive thinning of frontal, temporal and parietal cortices, subcortical grey matter atrophy including thalamus and cerebellum and involvement of long intrahemispheric, commissural and corticospinal tracts. The neuroimaging profile of the C9ORF72 expansion was significantly more symmetrical than progranulin mutations with significantly less temporal lobe involvement than microtubule-associated protein tau mutations. Neuropathological examination in six cases with C9ORF72 mutation from the frontotemporal lobar degeneration series identified histomorphological features consistent with either type A or B TAR DNA-binding protein-43 deposition; however, p62-positive (in excess of TAR DNA-binding protein-43 positive) neuronal cytoplasmic inclusions in hippocampus and cerebellum were a consistent feature of these cases, in contrast to the similar frequency of p62 and TAR DNA-binding protein-43 deposition in 53 control cases with frontotemporal lobar degeneration-TAR DNA-binding protein. These findings corroborate the clinical importance of the C9ORF72 mutation in frontotemporal lobar degeneration, delineate phenotypic and neuropathological features that could help to guide genetic testing, and suggest hypotheses for elucidating the neurobiology of a culprit subcortical network.

Amyloid load and cerebral atrophy in Alzheimer's disease: an 11C-PIB positron emission tomography study

To determine the relationship between cerebral amyloid plaque load and rates of cerebral atrophy in Alzheimer's disease. (11)C-PIB((11)C-6-OH benzothiazole)PET (positron emission tomography) findings were correlated with volumetric magnetic resonance imaging (MRI) measurements in nine subjects with mild to moderate AD. Analysis revealed a positive correlation between rates of whole brain atrophy and whole brain (p = 0.019) and regional (11)C-PIB uptake. This provides support for the central role of amyloid deposition in the pathogenesis of AD.

Novel role of Stat1 in the development of docetaxel resistance in prostate tumor cells

A major obstacle for clinicians in the treatment of advanced prostate cancer is the inevitable progression to chemoresistance, especially to docetaxel. It is essential to understand the molecular events that lead to docetaxel resistance in order to identify means to prevent or interfere with chemoresistance. In initial attempts to detect these events, we analysed genomic differences between non-resistant and docetaxel-resistant prostate tumor cells and, of the genes modulated by docetaxel treatment, we observed Stat1 and clusterin gene expression heightened in the resistant phenotype. In this study, we provide biochemical and biological evidence that these two gene products are related. Stat1 and clusterin protein expression was induced upon docetaxel treatment of DU145 cells and highly overexpressed in the docetaxel-resistant DU145 cells (DU145-DR). The increase in total Stat1 corresponded to an increase in phosphorylated Stat1. Interestingly, there was no detectable difference between DU145 and DU145-DR cells expression of total Stat3 and phosphorylated Stat3. Treatment of DU145-DR cells with small interfering RNA targeted for Stat1 not only resulted in the knockdown of Stat1 expression, but it also caused the inhibition of clusterin expression. Thus, Stat1 appears to play a key role in the regulation of clusterin. Remarkably, inhibition of Stat1 or clusterin expression resulted in the re-sensitization of DU145-DR cells to docetaxel. These results offer the first evidence that Stat1, and its subsequent regulation of clusterin, are essential for docetaxel resistance in prostate cancer. Targeting this pathway could be a potential therapeutic means for intervention of docetaxel resistance.

Effects of ischemia on gene expression

Microarray gene expression technology has recently made it feasible to characterize the RNA expression of thousands of genes across numerous tissue samples. We hypothesized that the warm ischemia commonly associated with the surgical extirpation of human tissue would have significant effects on gene expression profiles. To quantitate the effects of warm ischemia on human tissue, we rapidly dissected normal mucosa from a human colon cancer specimen. The specimen was divided and maintained at room temperature until snap-frozen in liquid nitrogen. Aliquots of tissue were frozen at times 5, 10, 15, 20, 40, and 60 min after extirpation. Spotted microarrays composed of 2400 distinct elements were used to assay mRNA derived from each time point in triplicate. Eisen's hierarchical clustering methodology and Bayesean statistical methods were then used to assay the effects of warm ischemia on gene expression. Application of time-course statistical models suggest that three patterns were induced by ischemia, accounting for 68.2, 17.8, and 13.4% of the evaluable genes, respectively. Pattern I corresponds to an average change of 27% over 60 min from 5 min baseline level of expression and 63.8% of the genes with at least 80% probability of membership in this pattern show average increases in expression over 60 min. The remainder decrease on average. Pattern II genes show the least ischemia-related effects, demonstrating an average change of only 12% over 60 min. In contrast to pattern I, we find that 67.5% of the genes with at least 80% probability of membership in this pattern are decreasing in expression on average over time. The remaining 32.5% in this pattern increase an average of 12% over 60 min. Finally, pattern III genes (13.4% of the sample) show the greatest sensitivity to ischemia, changing an average of 50% over 60 min, with about the same number increasing as are decreasing. Fold changes in RNA over- or under-expression were observed up to greater than 20-fold. Warm ischemia associated with the surgical extirpation of human tissues has significant effects on gene expression. These data support the careful monitoring of ischemic time for tissues harvested for the purpose of gene profiling.

Stat3-mediated Myc expression is required for Src transformation and PDGF-induced mitogenesis

Signal transducer and activator of transcription (STAT) proteins perform key roles in mediating signaling by cytokines and growth factors, including platelet-derived growth factor (PDGF). In addition, Src family kinases activate STAT signaling and are required for PDGF-induced mitogenesis in normal cells. One STAT family member, Stat3, has been shown to have an essential role in cell transformation by the Src oncoprotein. However, the mechanisms by which STAT-signaling pathways contribute to mitogenesis and transformation are not fully defined. We show here that disruption of Stat3 signaling by using dominant-negative Stat3beta protein in NIH 3T3 fibroblasts suppresses c-Myc expression concomitant with inhibition of v-Src-induced transformation. Ectopic expression of c-Myc is able to partially reverse this inhibition, suggesting that c-Myc is a downstream effector of Stat3 signaling in v-Src transformation. Furthermore, c-myc gene knockout fibroblasts are refractory to transformation by v-Src, consistent with a requirement for c-Myc protein in v-Src transformation. In normal NIH 3T3 cells, disruption of Stat3 signaling with dominant-negative Stat3beta protein inhibits PDGF-induced mitogenesis in a manner that is reversed by ectopic c-Myc expression. Moreover, inhibition of Src family kinases with the pharmacologic agent, SU6656, blocks Stat3 activation by PDGF. These findings, combined together, delineate the signaling pathway, PDGF --> Src --> Stat3 --> Myc, that is important in normal PDGF-induced mitogenesis and subverted in Src transformation.

Lymphatic mapping in the treatment of breast cancer

Developed initially for the treatment of malignant melanoma, lymphatic mapping and sentinel lymph node biopsy have recently been introduced into the treatment of early breast cancer. In breast cancer patients, harvested sentinel lymph nodes are evaluated more thoroughly by detailed pathologic examination using serial sectioning, immunohistochemistry, and reverse transcriptase-polymerase chain reaction (RT-PCR) techniques. This allows for the detection of smaller tumor volumes and leads to more accurate staging. Lymphatic mapping has a 68% to 98% success rate in identifying the sentinel lymph node. The false-negative rate (defined as a negative sentinel lymph node while a higher node or nodes in the axilla are positive) is between 0% and 2%. The morbidity associated with this procedure is minimal. We believe that lymphatic mapping and sentinel lymph node biopsy will ultimately lead to more conservative treatment of patients with breast cancer. This article describes the historical background and technical aspects of the procedure. This is followed by updated, prospectively collected outcomes data from 466 consecutive breast cancer patients who underwent lymphatic mapping at the H. Lee Moffitt Cancer Center, as well as an up-to-date review of the literature.

Guidelines for sentinel node biopsy and lymphatic mapping of patients with breast cancer

OBJECTIVE

To define preliminary guidelines for the use of lymphatic mapping techniques in patients with breast cancer.

SUMMARY BACKGROUND DATA

Lymphatic mapping techniques have the potential of changing the standard of surgical care of patients with breast cancer.

METHODS

Four hundred sixty-six consecutive patients with newly diagnosed breast cancer underwent a prospective trial of intraoperative lymphatic mapping using a combination of vital blue dye and filtered technetium-labeled sulfur colloid. A sentinel lymph node (SLN) was defined as a blue node and/or a hot node with a 10:1 ex vivo gamma probe ratio of SLN to non-SLN. All SLNs were bivalved, step-sectioned, and examined with routine hematoxylin and eosin (H&E) stains and immunohistochemical stains for cytokeratin. A cytokeratin-positive SLN was defined as any SLN with a defined cluster of positive-staining cells that could be confirmed histologically on H&E sections.

RESULTS

Fine-needle aspiration (FNA) or stereotactic core biopsy was used to diagnose 195 of the 422 patients (46.2%) with breast cancer; 227 of 422 patients (53.8%) were diagnosed by excisional biopsy. The SLN was successfully identified in 440 of 466 patients (94.4%). Failure to identify an SLN to the axilla intraoperatively occurred in 26 of 466 patients (5.6%). In all patients who failed lymphatic mappings, a complete axillary dissection was performed, and metastatic disease was documented in 4 of 26 (15.4%) of these patients. Of the 26 patients who failed lymphatic mapping, 11 of 227 (4.8%) were diagnosed by excisional biopsy and 15 of 195 (7.7%) were diagnosed by FNA or stereotactic core biopsy. Of interest, there was only one skip metastasis (defined as a negative SLN with higher nodes in the chain being positive) in a patient with prior excisional biopsy. A mean of 1.92 SLNs were harvested per patient. Twenty percent of the SLNs removed were positive for metastatic disease in 105 of 440 (23.8%) of the patients. Descriptive information on 844 SLNs was evaluated: 339 of 844 (40.2%) were hot, 272 of 844 (32.2%) were blue, and 233 of 844 (27.6%) were both hot and blue. At least one positive SLN was found in 4 of 87 patients (4.6%) with noninvasive (ductal carcinoma in situ) tumors. A greater incidence of positive SLNs was found in patients who had invasive tumors of increasing size: 18 of 112 patients (16%) with tumor size between 0.1 mm and 1 cm had positive SLNs. However, a significantly greater percentage of patients (43 of 131 [32.8%] with tumor size between 1 and 2 cm and 31 of 76 [40.8%] with tumor size between 2 and 5 cm) had positive SLNs. The highest incidence of positive SLNs was seen with patients of tumor size greater than 5 cm; in this group, 9 of 12 (75%) had a positive SLN (p < 0.001).

CONCLUSIONS

This study demonstrates that accurate SLN identification was obtained when all blue and hot lymph nodes were harvested as SLNs. Therefore, lymphatic mapping and SLN biopsy is most effective when a combination of vital blue dye and radiolabeled sulfur colloid is used. Furthermore, these data demonstrate that patients with ductal carcinoma in situ or small tumors exhibit a low but significant incidence of metastatic disease to the axillary lymph nodes and may benefit most from selective lymphadenectomy, avoiding the unnecessary complications of a complete axillary lymph node dissection.

Elevated c-Src protein expression is an early event in colonic neoplasia

The molecular events regulating the development and progression of colonic neoplasia are currently being delineated. Recent studies have implicated c-Src protein kinase activation as an early event in the malignant transformation of colonic epithelial cells. However, increased c-Src activity has also been reported in colon carcinomas as well as in metastatic hepatic and extrahepatic colon carcinomas. To further investigate the potential role of c-Src in the progression of colonic neoplasia, we analyzed c-Src levels by immunohistochemistry in 27 colorectal resection specimens. Mouse monoclonal antibody to c-Src protein was applied to 3-micron sections from formalin-fixed, paraffin-embedded tissues using the avidin-biotin-peroxidase method. The combination of adenomatous (AD) and adjacent carcinomatous mucosa (CA) specimens were present in 20 of 27 patients. In 15 cases, synchronous metastatic (MT) lesions were available for evaluation. Strong c-Src expression was evident in 95% of AD (n = 20), in contradistinction to 32% of MT (n = 19) and 14% of CA (n = 22). Weak-to-moderate c-Src expression was seen in adjacent normal colonic mucosa (NM) in 96% of cases. Signed rank test univariate analysis revealed a statistically significant difference in c-Src expression between NM/AD (p = 0.0001), NM/CA (p = 0.0001), NM/MT (p = 0.0006), AD/CA (p = 0.0001), and AD/MT (p = 0.0002). No significant correlation between levels of c-Src expression and patient survival, tumor size, histologic grade, or tumor configuration was observed using the Cox's Regression Model. Similar results were obtained by analysis of c-Src protein levels and c-Src kinase activity as measured by Western blot and in vitro kinase assays of representative cases. Our results indicate that: (a) elevated c-Src expression is an important early event during colorectal carcinogenesis; (b) its activation may be involved in tumor progression in a subset of colonic carcinomas; and (c) additional molecular events are necessary for invasion to occur.

The Role of Selective Lymphadenectomy in Breast Cancer

BACKGROUND: Axillary node dissection is considered a standard staging procedure in patients with breast cancer. The procedure is associated with significant morbidity and provides pathologists with many lymph nodes to evaluate. METHODS: A total of 174 women participated in a trial that included preoperative lymphoscintigraphy and intraoperative lymphatic mapping using a combination of a vital blue dye and radiocolloid mapping. RESULTS: The intraoperative lymphatic mapping correctly identified a sentinel lymph node (SLN) in 160 (92%) of 174 patients. One skip metastasis (0.7%) occurred in 136 women who had a subsequent complete node dissection. CONCLUSIONS: Lymphatic mapping and SLN biopsy using a combination of mapping techniques provide accurate nodal staging for women with breast cancer. With this technique, approximately 70% to 80% of women with no axillary metastases could be spared the morbidity of a complete node dissection.

Extracellular annexin VI expression is associated with divalent cation-dependent endothelial cell adhesion of metastatic RAW117 large-cell lymphoma cells

We previously found that cell surface molecules of approximately 70, approximately 35, approximately 32, approximately 22, and approximately 14 kDa from liver-metastatic murine RAW117 large-cell lymphoma cells bound to target liver microvessel endothelial cells. Isolation and sequencing of the approximately 35-kDa component revealed it to be annexin II, a Ca(2+)-binding molecule involved in cytoskeletal and membrane interactions. Annexin II antibodies inhibited the adhesion of RAW117 tumor cells to live or fixed liver endothelial cells, and purified tumor cell surface fractions containing the approximately 35-kDa component inhibited partially RAW117 cell-endothelial cell adhesion, suggesting a role for annexins in tumor cell-endothelial cell adhesion. In the present study we identified the 70-kDa cell surface component that binds to hepatic sinusoidal endothelial cells in a Ca(2+)-dependent manner as annexin VI. Cytofluorographic analysis indicated that annexin VI was expressed on the cell surface in slightly higher amounts on highly metastatic RAW117 cells, and it was not removable by EDTA treatment. Anti-annexin VI antibodies inhibited the adhesion of RAW117 cells to fixed or unfixed murine hepatic sinusoidal endothelial cells by approximately 40%, indicating a role for annexin VI in mediating a portion of the Ca(2+)-dependent RAW117 cell adhesion to target liver microvessel endothelial cells.

Extracellular annexin II is associated with divalent cation-dependent tumor cell-endothelial cell adhesion of metastatic RAW117 large-cell lymphoma cells

Using fixed microvessel endothelial cell monolayers the molecules involved in the adhesion of liver-preferring murine RAW117 large cell lymphoma cells to murine liver-derived microvessel endothelial cells were identified by affinity isolation. Detergent lysates obtained from poorly (P) or highly (H10) liver-metastatic cells inhibited RAW117-H10 cell adhesion to hepatic sinusoidal endothelial (HSE) cell monolayers. Allowing detergent lysates of cell surface-labeled RAW117 cells to bind to fixed HSE cell monolayers and eluting the bound components indicated that several tumor cell surface molecules (approximately 70, approximately 35, approximately 32, approximately 22, and approximately 14 kDa) might be involved in RAW117 cell-HSE cell adhesion. The approximately 35 kDa component was cation dependent in its binding to target HSE cells. Increasing detergent concentration had no effect on binding of the approximately 35 kDa component to HSE cell monolayers, whereas treatment with 0.5 M NaCl resulted in its selective elution from HSE cells. Incubation of the HSE cell monolayers with detergent lysates from cell surface-labeled RAW117-H10 cells resulted in selective depletion of the approximately 35 kDa component, suggesting that the binding is saturable. This divalent cation-dependent molecule is one of the major tumor cell surface components bound by several types of endothelial cells and murine hepatocytes, whereas there was poor binding of this component to unfixed or fixed human red blood cells. The purified, partially (approximately 40%) sequenced molecule had amino acid sequence identity with murine but not bovine annexin II, indicating that it was not bound from the bovine serum used to grow RAW117 cells. Using antibodies specific for annexin II flow cytometry indicated equivalent amounts of annexin II are expressed on RAW117 cell surfaces in the absence or presence of excess EDTA, whereas annexin I was only found in low amounts on the surfaces of RAW117 cells. Annexin II antibodies inhibited by approximately 40-50% the adhesion of RAW117 tumor cells to live or fixed endothelial cells, and purified tumor cell surface fractions containing the approximately 35 kDa component partially inhibited (approximately 35%) RAW117 cell-HSE cell adhesion. The data indicate that annexin II is expressed on the extracellular surface of RAW117 cells, and cell surface-annexin II mediates a portion of the Ca(2+)-dependent RAW117 cell adhesion to liver microvessel endothelial cells.