A protein produced by mast cells in the immune system may predict which people infected with dengue virus will develop life-threatening complications, according to researchers at Duke Medicine and Duke-National University of Singapore (Duke-NUS).
Their study also found that in experiments in mice, a class of drugs commonly used to treat asthma by targeting the mast cells could help treat vascular symptoms associated with dengue infections.
Dengue virus is spread by mosquitoes and infects as many as 390 million people worldwide each year, according to new estimates. It is a significant health issue in tropical areas of the world including parts of Latin America and Asia, but Florida residents have reported cases in recent years.
No treatments are available for dengue virus, and serious cases can result in widespread vascular leakage and haemorrhaging.
In 2011, Duke researchers reported that mast cells, which help the body respond to bacteria and other pathogens, play a role in attacking dengue virus and halting its spread. This finding presented new avenues for research, given the existing classes of drugs that target mast cells or the products of mast cells once they are activated.
In one experiment in the current study of dengue virus in mice, the researchers found that certain classes of drugs commonly used to treat asthma are effective in limiting vascular leakage associated with dengue.
‘It may not seem intuitive how asthma and dengue infection would be related and would respond to the same types of drugs, but because both diseases are promoted by mast cells, the cellular targets of the class of drugs is quite effective,’ said lead author Ashley L. St. John, PhD, assistant professor of emerging infectious diseases at Duke-NUS.
The researchers continued to investigate the role of mast cells in attacking dengue virus in humans, and identified a biomarker – a mast cell-derived product – that appeared to predict the illness’ most severe cases in human patients.
Most patients infected by a dengue virus develop a high fever, dubbed dengue fever, and recover on their own. However, a small number of these cases develop into dengue haemorrhage fever, a dangerous condition marked by serious complications, including bleeding, respiratory distress and severe abdominal pain.
Until now, doctors have not been able to predict who will develop dengue haemorrhage fever. When the researchers studied blood serum samples from patients with dengue infection, they found that the levels of a protein produced by mast cells, chymase, were significantly higher in the patients who developed dengue haemorrhagic fever compared to those who recovered after dengue fever.
‘In addition to revealing a potential new way to diagnose and treat dengue infections, these finding may have much broader applicability for other infectious diseases where vascular leakage is a major pathologic outcome,’ said senior study author Soman N. Abraham, PhD, professor of pathology, immunology, and molecular genetics and microbiology at Duke Medicine and professor of emerging infectious diseases at Duke-NUS. Duke Medicine

 In a study researchers from the University of North Carolina Lineberger Comprehensive Cancer Center have developed a new method to visualise ageing and tumour growth in mice using a gene closely linked to these processes.
Researchers have long known that the gene, p16INK4a (p16), plays a role in ageing and cancer suppression by activating an important tumour defence mechanism called ‘cellular senescence’. The UNC team led by Norman Sharpless, MD, Wellcome Distinguished Professor of Cancer Research and Deputy Cancer Center Director, has developed a strain of mice that turns on a gene from fireflies when the normal p16 gene is activated. In cells undergoing senescence, the p16 gene is switched on, activating the firefly gene and causing the affected tissue to glow.
Throughout the entire lifespan of these mice, the researchers followed p16 activation by simply tracking the brightness of each animal. They found that old mice are brighter than young mice, and that sites of cancer formation become extremely bright, allowing for the early identification of developing cancers.
‘With these mice, we can visualise in real-time the activation of cellular senescence, which prevents cancer but causes ageing. We can literally see the earliest molecular stages of cancer and ageing in living mice.’ said Sharpless.
The researchers envision immediate practical uses for these mice. By providing a visual indication of the activation cellular senescence, the mice will allow researchers to test substances and exposures that promote cellular ageing (‘gerontogen testing’) in the same way that other mouse models currently allow toxicologists to identify cancer-causing substances (‘carcinogen testing’). Moreover, these mice are already being used by scientists at UNC and other institutions to identify early cancer development and the response of tumours to anti-cancer treatments.
‘This work builds on previous work by the same group, as well as others, showing intriguing relationships among aging, cancer and cell senescence. It provides a valuable new tool to probe these relationships,’ said Felipe Sierra, Ph.D., director of the Division of Aging Biology, National Institute on Aging, NIH.
The researchers used these mice to make several unexpected discoveries. First, the group was able to track the accumulation of senescent cells in ageing mice by assessing how brightly each mouse glowed. Surprisingly, the brightest animals were no more likely to die from spontaneous cancer than dimmer animals of the same age. That is, the number of senescent cells in the mouse did not predict its risk of dying.
‘The result we, and I think others, predicted is that the animals with the highest number of senescent cells would get more cancers and die sooner, but this was not the case’ said Sharpless.
Another surprise came from the disparities in p16 levels among the mice. The authors studied a large group of genetically identical animals that were all housed in the same way and fed the same diet. However, despite identical genetic and environmental conditions, the brightness of individual mice at any given age was highly variable, suggesting that factors beyond genetics and diet influence ageing.
The glowing mice also provide a window into the formation of cancers. Expression of p16 is activated in the earliest stages of cancer formation to suppress cancer. Usually activation of p16 prevents cancer, but rarely this tumour suppressor mechanism fails and tumours develop, while still activating the p16 gene. As such, all tumours forming in these mice strongly glowed, allowing researchers to monitor early tumour formation in a wide variety of cancer types. In contrast to expectations, the researchers also found that p16 was activated not only in the tumour cells themselves, but also in normal, neighbouring cells.
‘This finding suggests that activation of senescence results from an abnormal milieu within a developing cancer. Somehow, many or all the cells in a would-be tumour know they are in a bad place, and activate this tumour suppressor gene as a defence mechanism, even if they are not the would-be cancer cells themselves. This occurs really early in the cancer; we’re talking about the earliest events of neoplasia that have ever been measured in living animals,’ said Sharpless.
The Sharpless group believes similar approaches to monitoring senescence can be developed in order to study ageing and tumour development in humans. The group is particularly interested in how cancer therapies influence human ageing and patient outcome. Working with UNC oncologists, the Sharpless group has already measured p16 expression in several hundred patients undergoing cancer therapy. These studies, along with efforts employing the glowing mouse, aims to develop more effective and tolerable patient treatment schemes based upon ‘molecular’, as opposed to ‘chronologic’, age. EurekAlert

A team led by Massachusetts General Hospital (MGH) researchers has identified a genetic signature that appears to reflect the risk of tumour recurrence or spread in men surgically treated for prostate cancer. If confirmed in future studies, this finding not only may help determine which patients require additional treatment after the cancerous gland has been removed, it also may help address the most challenging problem in prostate cancer treatment – distinguishing tumours that require aggressive treatment from those that can safely be monitored.
‘Radical prostatectomy is the standard of care for men whose cancer is advanced but confined to the prostate gland, but we know that the factors we use to determine which patients need radiation therapy after surgery are inadequate,’ says W. Scott McDougal, MD, of the MGH Department of Urology, corresponding author of the report. ‘The treatments available to our patients can have significant impact on their quality of life, so a better way to know which patients with localised cancer need additional therapy after surgery and which require no additional treatment is a significant unmet need.’
Gene expression signatures indicating patient prognosis and sometimes the most appropriate treatment have been incorporated into care for breast cancer and other tumours. Studies looking for such markers in prostate cancer have had variable results, and their potential usefulness to guide treatment has not been determined. For the current study the research team – led by Chin-Lee Wu, MD, PhD, of the MGH Department of Pathology – examined samples of malignant tissue from around 200 prostate cancer patients who had radical prostatectomies at the MGH between 1993 and 1995, analyzing the expression patterns of more than 1,500 genes associated with prostate cancer in earlier studies. With the results of that analysis, they developed a 32-gene index to reflect the likelihood that a patient’s tumour would recur, signified by detectable levels of prostate-specific antigen (PSA) after the gland had been remove, or spread.
To validate the usefulness of the index, they used it to analyse tissue samples from a different group of almost 300 patients who had their prostates removed in 1996 and 1997, comparing the index with currently used prognostic factors – such as PSA levels, physical examination, and a tumour’s microscopic appearance – to see how accurately each predicted the actual incidence of tumour recurrence or metastasis during the 10 years after surgery. The expression-based index proved to be the most accurate method. Among those it designated as high-risk, the actual incidence of tumor recurrence was 47 percent and of metastasis, 14 percent. Among those classified as intermediate risk, actual recurrence was 22 percent, and metastasis occurred in 2 percent. No recurrence or metastasis were seen in patients classified as low-risk by the gene-expression index.
To get a sense of whether the index could help determine risk at the time of diagnosis, the researchers used it to assess pre-surgical needle biopsy samples from 79 patients in the validation group. The risk assignment based on biopsy results closely matched the assessment based on surgically removed tissue, and the prognostic ability of the index was better than that of other pathological information available at the time a biopsy was taken. Because the current report is based on study of patients treated at a single institution, the authors note, it requires confirmation in larger, multi-institutional studies.
‘A more accurate prognosis at the time of diagnosis could give patients and their physicians much more confidence in choosing a definitive therapy or pursuing active surveillance for those at low risk, which could reduce over-treatment, a critical issue in disease management,’ says lead author Wu, an associate professor of Pathology at Harvard Medical School. McDougal is the the Kerr Professor of Urology, at HMS. Massachusetts General Hospital

The Journal of the American Heart Association published results from a study directed by Dr. Éric Thorin of the Montreal Heart Institute (MHI), which suggests for the first time that a blood protein contributes to the early development of atherosclerosis.
Dr. Thorin, his team and his collaborators discovered that the blood levels of angiopoietin-like protein 2 (angptl2) are six times higher in subjects with coronary heart disease than in healthy subjects of the same age. Their basic research study also revealed that angptl2, which is undetectable in young mice, increases with age in healthy subjects and increases prematurely in subjects who have high cholesterol and pre-atherosclerotic lesions. Entitled ‘Angiopoietin-like 2 promotes atherogenesis in mice,’ this study was conducted using an animal model consisting of three to twelve-month-old mice. These results represent a major advance in the prevention and treatment of atherosclerosis. ‘Although much work remains to be done to broaden our knowledge of this protein’s mechanisms of action, angiopoietin-like protein 2 may represent an early biomarker not only to prevent vascular damage but also to predict atherosclerotic disease,’ explained Dr. Thorin. For 15 years, Dr. Thorin, a researcher at the MHI Research Centre and full professor at Université de Montréal, has been interested in the evolution of artery function during the ageing process and in the underlying mechanisms of atherosclerosis.
More specifically over the past five years, he has looked at the role of this particular protein. Thanks to his work, we now know that angptl2 causes a high degree of vascular inflammation. Blood levels of this protein increase in patients with cardiovascular disease as well as in people with complications related to diabetes, obesity and cancer in which the small blood vessels are damaged, as all of these diseases are associated with chronic inflammation.
According to Dr. Anil Nigam, a cardiologist and specialist in cardiovascular disease prevention at the MHI and co-author of the study, ‘Prevention is the ideal solution to delay the onset of atherosclerosis, and an early blood marker such as angptl2—if future clinical studies confirm this finding—will serve as an important tool to identify at-risk subjects who do not present with any symptoms of atherosclerotic disease.’ Montreal Heart Institute

Diagnosed in toddlers, X-linked hypophosphatemia (XLH) is the most common form of heritable rickets, in which soft bones bend and deform, and tooth abscesses develop because infections penetrate soft teeth that are not properly calcified. Researchers at McGill University and the Federal University of Sao Paulo have identified that osteopontin, a major bone and tooth substrate protein, plays a role in XLH. Their discovery may pave the way to effectively treating this rare disease.
The findings were made by the laboratories of Marc McKee, a professor in the Faculty of Dentistry and the Department of Anatomy and Cell Biology at McGill University, and of Nilana M.T. Barros, a professor at the Federal University of Sao Paulo. The team built upon previous research that had shown that mutations in the single gene PHEX are responsible for causing XLH.
‘XLH is caused in part by renal phosphate wasting, which is the urinary loss from the body of phosphate, an important building block of bones and teeth, along with calcium.’ says Prof. McKee. ‘In pursuing other factors that might contribute to XLH, we used a variety of research methods to show that PHEX enzymatic activity leads to an essentially complete degradation of osteopontin in bones.’
This loss of osteopontin, a known potent inhibitor of mineralisation (or calcification) in the skeleton and dentition, normally allows bones and teeth to mineralise and thus harden to meet the biomechanical demands placed on them. In XLH patients lacking functional PHEX enzyme, osteopontin and some of its smaller potent inhibitory peptides are retained and accumulate within the bone. This prevents their hardening and leads to soft deformed bones such as bowed legs (or knock-knees) seen in toddlers.

While not life-threatening, this decreased mineralisation of the skeleton (osteomalacia), along with the soft teeth, soon leads to a waddling gait, short stature, bone and muscle pain, weakness and spontaneous tooth abscesses.

The fact that these symptoms are only partially improved by the standard treatment with phosphate – which improves circulating phosphate levels – prompted the researchers to look for local factors within the bone that might be blocking mineralisation in these patients.

‘With this new identification of osteopontin as a substrate protein for PHEX,’ says Professor Barros, ‘we can begin to develop an enzyme-replacement therapy to treat XLH patients who have non-functional PHEX, much as has been done using a different enzyme to treat another rare bone disease called hypophosphatasia.’ McGill University