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New MRI tools cast light on Parkinson’s disease progress A team of scientists from Massachusetts Institute of Technology (MA, USA) have developed new imaging techniques that could have profound implications for the future diagnosis and management of Parkinson’s disease (PD). The research, published recently in Archives of Neurology, involved combining results from different MRI scans to produce composite images. When the investigators applied these techniques to the study of patients with PD, the resultant composite images allowed degeneration within the brain to be viewed in unprecedented detail. Using the composite imagery, the team were able to provide evidence that brain deterioration due to PD occurs within the substantia nigra pars compacta (SNc) prior to occurring within the cholinergic basal forebrain (BF). This is the first time that evidence from living patients
has been gathered to support prominent anatomist Heikio Braak’s hypothesis that brain degeneration originates in deep brain structures before progressing to other parts of the brain. To obtain their results, the scientists scanned the brains of 29 patients at various stages of PD (13 patients at Hoehn and Yahr [H&Y] stage 1 and 16 patients at H&Y stages 2–3) as well as 27 healthy control subjects. The team collected data for each patient by utilizing four different MRI techniques: multiecho proton density, multiecho T1-weighted, T2-weighted and T2-weighted fluid-attenuated inversion recovery. By combining the results of these scans, the researchers were able to construct images in which the SNc and the BF were clearly visible. They were then able to manually calculate the volume of both neural structures in each individual. Older adult
Stage 2 PD
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10.2217/BMM.13.3 © 2013 Future Medicine Ltd
Coronal section through an averaged multispectral image at the level of the midbrain. (A) The SN in a healthy control. Magnified view of the SN in (B) in a healthy female control and (C) in a patient with PD; signal loss in the SN is readily apparent in the PD brain (green arrow). Image courtesy of David Ziegler (University of California, San Francisco, CA, USA) © (2013) David Ziegler. PD: Parkinson’s disease; SN: Substantia nigra.
Biomarkers Med. (2013) 7(1), 83–87
ISSN 1752-0363
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The scientists found that the SNc volume of the 13 patients diagnosed with H&Y stage 1 PD had been significantly decreased when compared with the healthy control subjects. On the other hand, relative to the control subjects, the 16 patients with H&Y stage 2 or 3 PD did not display significant signs of deterioration in this area of the brain, suggesting that the SNc is affected primarily in the earlier stages of PD. The inverse was found when analyzing the relative volumes of the BF between the PD patients and the control group. When compared with the control subjects, patients with H&Y stage 2 or 3 PD displayed a statistically significant decrease in BF volume. However, the volume of the BF in patients
with H&Y stage 1 PD was not significantly different to that of the healthy volunteers, suggesting that BF volume loss occurred later in the progression of the disease. Researcher David Ziegler spoke to Biomarkers in Medicine to explain the significance of the results and to highlight the potential of the new techniques for the future of PD prediction and treatment. He noted that his team had established “the utility of these new MRI tools for measuring and tracking subtle disease-related changes in structures that are notoriously difficult to visualize with conventional MRI.” As a consequence, he claimed the team had “provided much needed biomarkers for characterizing and tracking brain changes associated” with PD that “can now be used to identify and track differences in disease progression” and “will enable clinicians to predict which patients are likely to develop particular symptoms and to tailor therapies to each patient’s needs.”
When asked about the team’s plans for future research in this area, Ziegler explained that they “are currently con ducting additional analyses to correlate brain changes in the SN and BF with clinical and cognitive measures. In the future, we are hoping to conduct a longitudinal study in which we collect these imaging measures multiple times on patients as they progress.” The team will then “follow the patients to track whether the rate of disease progression or the development of specific cognitive impairments or dementia is associated with a particular pattern of brain changes.” – Written by Michael Mansbridge Source: Ziegler D, Wonderlick J, Ashourian P et al. Substantia Nigra volume loss before basal forebrain degeneration in early Parkinson disease. Arch. Neurol. 26, 1–7 (2012).
Functional MRI could predict onset of bipolar disorder in at-risk individuals A recent functional MRI (fMRI) study from Australian researchers has revealed that individuals with an increased genetic risk of bipolar disorder actually have clear and quantifiable differences in brain activity compared with controls before clinical signs of the condition are detectable. Dysfunctional neural mechanisms involved in cognitive control of emotion have been previously associated with genetic risk of bipolar disorder but the triggers are not yet understood. Bipolar disorder has the highest suicide rate of all psychiatric disorders. “This study is important for two reasons. First, any differences (such as those we identified in our recent study) may indicate endophenotypes (trait abnormalities) that are indicative of a vulnerability to bipolar disorder and not a consequence of developing this condition,” explained study leader Philip Mitchell from the Black Dog Institute (Sydney, Australia) and University of New South Wales (Sydney, Australia), two institutions involved in this recent 84
study, when speaking to Biomarkers in Medicine. “Second, demonstration of biological differences in those at increased risk will be important in the development of prevention and early intervention programs for those at heightened risk for this condition.”
“...functional MRI could be used in the
future as a tool for improving the lives of young people at risk of [bipolar disorder] in the future by allowing early detection, leading to improved outcomes and even prevention of onset.” In this recent study, fMRI was used to monitor functional brain activity during a facial-emotion go/no-go task, in which participants were shown images of happy, fearful or calm (neutral) human faces. Study participants were 47 18–30 year olds with a high genetic risk of developing bipolar disorder and 47 control subjects of the same age without a family history of bipolar or other severe mental illness. Biomarkers Med. (2013) 7(1)
Whole-brain corrected fMRI analyses revealed significantly reduced brain activity in response to the facial emotions in individuals with a high risk of bipolar disorder compared with the control group. Researchers observed an impaired inhibitory function of the inferior frontal cortex in response to fearful faces in at-risk individuals. This brain area is known to regulate emotional responses and the study authors suggest that this may be a trait marker of bipolar vulnerability. “A number of our subjects (at-risk or controls) were either currently depressed or on psychotropic medications, both of which could potentially confound our findings,” explained Mitchell when discussing the challenges faced in this recent study. “After we removed those subjects from the analyses, the results persisted, giving us increased confidence in the validity of the findings.” In addition to providing evidence that those at a high risk of bipolar disorder could have pre-existing functional future science group
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disturbances, the study also suggests that fMRI could be used in the future as a tool for improving the lives of young people at risk of the condition by allowing early detection, leading to improved outcomes and even prevention of onset. The researchers are also analyzing other imaging data on this same clinical population and are following participants up annually to determine predictors (neuroimaging, genetic, neuropsychological and clinical) of which subjects eventually go on to develop bipolar disorder. Mitchell explained to Biomarkers in Medicine that his group has a long-standing interest in identifying biological and psychological mechanisms in bipolar disorder: “We commenced the current study over 3 years ago and will be commencing
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our fourth year of follow-up of this clinical sample later this year. We have found the families very interested in this study, as they are all concerned with the risk of their children developing the illness, and wish to assist research that aims to eventually reduce this.” – Written by Sarah Miller Sources: UNSW news release: http://newsroom. unsw.edu.au /news /health / brain-imagingidentifies-bipolar-risk; Roberts G, Green MJ, Breakspear M et al. Reduced inferior frontal gyrus activation during response inhibition to emotional stimuli in youth at high risk of bipolar disorder. Biol. Psychiatry doi:10.1016/j. biopsych.2012.11.004 (2012) (Epub ahead of print).
Blood test developed for lymphedema holds promising potential Researchers from Stanford University School of Medicine (CA, USA) have recently developed a multianalyte biomarker panel they report could diagnose patients with lymphedema. The group also hopes the panel will be useful for risk stratification, quantitation of disease burden and prediction of disease response. Currently lymphedema, a condition often arising following radiation therapy for cancer or following infection from some parasites, is only diagnosed from physical symptoms that usually only arise once the condition has progressed to a point where it is difficult to treat. Combined with the fact that there are currently no drugs to treat the condition, this means research is in the area is a priority. The group initially sought to identify study candidates by performing transcriptional microarray analysis on paired diseased and normal skin specimens. Genes that appeared more active in lymphadematous tissue and had corresponding secreted protein products were then analyzed, with the secreted protein products that already have commercial blood future science group
tests available being studied further. This research resulted in a six-protein panel that was validated in blood samples from a cohort of 36 lymphedematous and 15 normal patients, giving an accuracy of 90%.
“This research resulted in a six-protein panel that was validated in blood samples from a cohort of 36 lymphedematous and 15 normal patients, giving an accuracy of 90%.”
The six protein biomarkers are each associated with one of the hallmark biological features of lymphadema: lymphangiogenesis, inf lammation, fibrosis and lipid metabolism. The authors explained that: “the observation that these genes are differentially expressed in diseased and normal tissues within the same individual, and that the secreted protein products of these genes are incrementally detected in lymphedema sera when compared with those of healthy controls, suggests that these proteins are directly related to the pathogenesis of the tissue pathology in lymphedema.” However, they do not exclude that the www.futuremedicine.com
panel may have included different proteins had they carried out more individual studies. “Further studies are warranted to determine whether this newly-identified biomarker panel will possess utility as an instrument for in vitro diagnosis of early and latent disease; the ultimate applicability to risk stratification, quantitation of disease burden, and resp onse to therapy can easily be envisioned,” the authors explained. Stanley Rockson, senior author of the study, noted: “a standardized, accurate bioassay for lymphedema could help to pave the road for future human clinical trials of drugs to treat it.” He is currently involved in clinical trials looking to find pharmaceutical agents for lymphedema, and is hoping to use the biomarker panel to aid those trials. – Written by Francesca Lake Source: Lin S, Kim J, Lee M-J et al. Prospective transcriptomic pathway analysis of human lymphatic vascular insufficiency: identification and validation of a circulating biomarker panel. PLoS One 7(12), e52021 (2012).
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Circulating cancer cells not such softies: hardiness might have potential as a biomarker While studying cancer cells that had been subjected to fluid forces similar to those found in the bloodstream, a group from the University of Iowa (IA, USA) recently observed that cancer cells are more likely to survive in this environment than normal epithelial cells. This feature, which they call ‘hardiness’, could be used as a biomarker for detecting cancer cells in the blood and may prove useful in monitoring cancer progression and detecting recurrence. The team, using mathematical calculations of fluid dynamics, created a system to mimic the flow experienced by a cell in the blood. They then subjected prostate cancer, breast cancer and melanoma cells to ten rounds of millisecond pulses of high fluid shear stress. The reported results
exposed that approximately 50% of the cancer cells survived, compared with very few normal epithelial cells. Exposure to stress also seemed to increase the ability of cancer cells to resist the stress. The team subsequently discovered that the hardiness had a genetic basis, with blocking of a signaling pathway associated with the affected genes reducing the hardiness of the cells. “For many years, it’s been assumed that these circulating cancer cells are quite fragile, and they essentially get ‘blended’ by the fluid forces in the blood, but there was no real direct evidence for how fluid forces in the blood affect cancer cells,” explained Michael Henry, lead author of the study. “By adding this really simple physical test to the isolation of circulating tumor cells,
this technique might let us sort out malignant cells from benign cells. Being able to quantify the numbers of ‘dangerous’ cells might be a more accurate prognostic marker for the patient than simply counting the total number of circulating tumor cells.” The team is now moving on to studying the technique in prostate cancer patients. “A next step for us is to translate these findings into patient specimens and determine whether this can be useful in a context that is clinically meaningful,” noted Henry. – Written by Francesca Lake Source: Barnes JM, Nauseef JT, Henry MD. Resistance to fluid shear stress is a conserved Biophysical property of malignant cells. PLoS One 7(12), e50973 (2012).
Tumor-homing nanoparticles developed to amplify biomarker signals In our efforts toward detecting cancer earlier, a new technology has been developed at the Massachusetts Institute of Technology (MA, USA) that aims to increase the concentration of cancerspecific markers in the blood or urine to a measurable level to enable us to detect the disease earlier. The technology could also be used to monitor tumor progression and response to treatment. Sangeeta Bhatia, lead author of the study, explained that cancer cells are always making biomarkers, but have limited production capacity; “that’s when we had this ‘aha’ moment: what if you could deliver something that could amplify that signal?” It has previously been shown that using the best biomarkers for ovarian cancer and the best detection technology, it 86
would not be possible to detect an ovarian tumor until 8–10 years after it had formed without amplification of the signal. Thus, such a technology could have large implications for early detection of tumors.
“...such a technology could have large implications for early detection of tumors.”
At the time, the group was looking at using nanoparticles that interact with proteases for tumor imaging, and was able to coat the nanoparticles with peptides targeted by MMP proteases, which are produced by cancer cells. The nanoparticles subsequently accumulated at the tumor site, where the MMP proteases from the cancer cell were expected to cleave the Biomarkers Med. (2013) 7(1)
nanoparticle-bound peptides, releasing them into the bloodstream. The peptides would then accumulate in the kidneys and be excreted in the urine, which could then be analyzed using mass spectrometry. To increase precision of the nanoparticles, they were engineered to express ten different peptides, each with a specific corresponding MMP protease and a size making them distinguishable by mass spectrometry. As the authors explained: “These protease-sensitive agents perform three functions in vivo: they target sites of disease, sample dysregulated protease activities and emit mass-encoded reporters into host urine for multiplexed detection by mass spectrometry.” The group tested the nanoparticles in mice, detecting early stages of colorectal carcinoma and liver fibrosis. For the future science group
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former, the nanoparticles are reported to have provided improved detection over current biomarkers, and for the latter, the researchers found the nanoparticles gave more rapid feedback than the standard, invasive liver biopsy. The team explained that “this approach of engineering synthetic biomarkers for multiplexed urinary monitoring should be broadly amenable to additional pathophysiological processes and point-of-care
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diagnostics.” They are currently studying whether the nanoparticles are able to detect metastasis and measure tumor response to chemotherapy. – Written by Francesca Lake Source: Kwong GA, von Maltzahn G, Murugappan G et al. Mass-encoded synthetic biomarkers for multiplexed urinary monitoring of disease. Nature 31(1), 63–70 (2012).
Novel genetic test shows promise for lung cancer patients Researchers from Seoul National University Hospital (South Korea) and Pfizer Oncology (CA, USA) have published the results of a new test for the ALK mutation in a recent issue of The Journal of Molecular Diagnostics. ALK fusions produce a constantly active tyrosine kinase that is responsible for approximately 5% of patients with non-small-cell lung carcinoma (NSCLC). Patients can be tested for fusion mutations in the ALK gene using FISH, immunohistochemistry or reverse transcription PCR. NSCLC patients have much better treatment options once they have been identified as having an ALK gene fusion, such as the drug crizotinib (XALKORI®; Pfizer) which is currently going through Phase III trials to specifically treat NSCLC patients that are ALK-positive. A number of ALK fusion detection tests have been clinically certified including a FISH-based test that was approved by the US FDA for the crizotinib clinical trials. Although the FISH test has received authorization,
it has a number of limitations includ ing its complexity, cost and level of throughput. “The FISH assay has undergone extensive validation in the clinical setting and is currently the gold standard for ALK fusion detection” said the lead investigators of this study, Dong-Wan Kim from the Seoul National University Hospital and Mao Mao from Pfizer Oncology. They continued: “A disadvantage of this diagnostic assay, however, lies in the fact that the signal can be subtle and consequently hard to interpret, requiring specialized technical expertise. It is also considerably more expensive compared with immunohistochemistry and reverse transcriptase PCR. An optimal assay should therefore not only be sensitive and specific, but also be economical, easy to perform, preferably automated, and readily adaptable to workflows of clinical service laboratories.” The group developed a novel test detecting ALK fusions by multiplexed transcript profiling using a gene expression platform
from NanoString ® Technologies (WA, USA). The assay was tested on 66 NSCLC samples and showed encouraging results in being able to detect low-level ALK fusions. In addition, the samples that were found to be ALK-positive by the assay responded well to crizotinib. The investigators concluded “While further testing on a larger sample size is needed for this assay to be considered in clinical practice, we have demonstrated that it offers a cost-effective, easy to perform, high-throughput and FFPEcompatible screening alternative for detecting ALK fusions.” – Written by Theo Bond Sources: Lira ME, Kim TM, Huang D et al. Multiplexed gene expression and fusion transcript analysis to detect ALK fusions in lung cancer. J. Mol. Diagn. 15(1), 51–61 (2013); Elsevier press release: www.elsevier.com/about/ press-releases/research-and-journals/novel-testidentifies-patients-most-likely-to-benefit-fromalk-inhibition-therapy
About the News The News highlights some of the most important events and research in the field of biomarkers. If you have newsworthy information, please contact: Francesca Lake, Commissioning Editor, Biomarkers in Medicine; Future Medicine Ltd, Unitec House, 2 Albert Place, London N3 1QB, UK Tel.: +44 (0)20 8371 6090; Fax: +44 (0)20 8371 6099;
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