New enzyme targets for selective cancer therapies

Thanks to important discoveries in basic and clinical research and technological advances, the fight against cancer has mobilized into a complex offensive spanning multiple fronts.

Work happening in a University of Alberta chemistry lab could help find new and more selective therapies for cancer. Researchers have developed a compound that targets a specific enzyme overexpressed in certain cancers—and they have tested its activity in cells from brain tumours.

Chemistry professor Christopher Cairo and his team synthesized a first-of-its-kind inhibitor that prevents the activity of an enzyme called neuraminidase. Although flu viruses use enzymes with the same mechanism as part of the process of infection, human cells use their own forms of the enzyme in many biological processes.

Cairo’s group collaborated with a group in Milan, Italy, that has shown that neuraminidases are found in excess amounts in glioblastoma cells, a form of brain cancer.

In a new study, a team from the University of Milan tested Cairo’s enzyme inhibitor and found that it turned glioblastoma cancer stem cells—found within a tumour and believed to drive cancer growth—into normal cells. The compound also caused the cells to stop growing, suggesting that this mechanism could be important for therapeutics. Results of their efforts were published Aug. 22 in the Nature journal Cell Death & Disease.

Cairo said these findings establish that an inhibitor of this enzyme could work therapeutically and should open the door for future research.

“This is the first proof-of-concept showing a selective neuraminidase inhibitor can have a real effect in human cancer cells,” he said. “It isn’t a drug yet, but it establishes a new target that we think can be used for creating new, more selective drugs.”

Long road from proof of concept to drug

Proving the compound can successfully inhibit the neuraminidase enzyme in cancer cells is just the first step in determining its potential as a therapy.

In its current form, the compound could not be used as a drug, Cairo explained, largely because it wasn’t designed to breach the blood-brain barrier making it difficult to reach the target cells. The team in Milan had to use the compound in very high concentrations, he added.

The research advances our understanding of how important carbohydrates are to the function of cells. Although most of us think of glucose (blood sugar) as the only important sugar in biology, there is an entire area of research known as glycobiology that seeks to understand the function of complex carbohydrate structures in cells. Carbohydrate structures cover the surface of cells, and affect how cells interact with each other and with pathogens.

Scientists have known for decades that the carbohydrates found on cancer cells are very different from those on normal cells. For example, many cancers have different amounts of specific residues like sialic acid, or may have different arrangements of the same residues.

“The carbohydrates on the cell surface determine how it interacts with other cells, which makes them important in cancer and other diseases. So, if we can design compounds that change these structures in a defined way, we can affect those interactions,” Cairo explained. “Finding new enzyme targets is essential to that process, and our work shows that we can selectively target this neuraminidase enzyme.”

Although there has been a lot of work on targeting viral neuraminidase enzymes, Cairo’s team has found inhibitors of the human enzymes. “The challenge in human cells is that there are four different isoenzymes. While we might want to target one for its role in cancer, hitting the wrong one could have harmful side-effects,” he said.

The U of A team reached out to their colleagues in Milan who were studying the role of a specific neuraminidase isoenzyme in cancer cells isolated from patients. Cairo approached them about testing a compound his team identified last year, which was selective for the same isoenzyme.

“I expected it would do something, but I didn’t know it would be that striking. It came out beautifully,” Cairo said.

The U of A team is already working on improving the compound, and developing and testing new and existing inhibitors using a panel of in vitro assays they developed.

“We’ve been working on these enzymes for about five years. Validation of our strategy­­­—design of a selective neuraminidase inhibitor and application in a cell that overexpresses that enzyme—is an achievement for us.”

Research underway to create pomegranate drug to stem Alzheimer’s and Parkinson’s

The onset of Alzheimer’s disease can be slowed and some of its symptoms curbed by a natural compound that is found in pomegranate. Also, the painful inflammation that accompanies illnesses such as rheumatoid arthritis and Parkinson’s disease could be reduced, according to the findings of a two-year project headed by University of Huddersfield scientist Dr Olumayokun Olajide, who specialises in the anti-inflammatory properties of natural products.

Now, a new phase of research can explore the development of drugs that will stem the development of dementias such as Alzheimer’s, which affects some 800,000 people in the UK, with 163,000 new cases a year being diagnosed. Globally, there are at least 44.4 million dementia sufferers, with the numbers expected to soar.

The key breakthrough by Dr Olajide and his co-researchers is to demonstrate that punicalagin, which is a polyphenol – a form of chemical compound – found in pomegranate fruit, can inhibit inflammation in specialised brain cells known as microglia. This inflammation leads to the destruction of more and more brain cells, making the condition of Alzheimer’s sufferers progressively worse.

There is still no cure for the disease, but the punicalagin in pomegranate could prevent it or slow down its development.

Dr Olajide worked with co-researchers – including four PhD students – in the University of Huddersfield’s Department of Pharmacy and with scientists at the University of Freiburg in Germany. The team used brain cells isolated from rats in order to test their findings. Now the research is published in the latest edition of the journal Molecular Nutrition & Food Research and Dr Olajide will start to disseminate his findings at academic conferences.

He is still working on the amounts of pomegranate that are required, in order to be effective.

"But we do know that regular intake and regular consumption of pomegranate has a lot of health benefits – including prevention of neuro-inflammation related to dementia," he says, recommending juice products that are 100 per cent pomegranate, meaning that approximately 3.4 per cent will be punicalagin, the compound that slows down the progression of dementia.

Dr Olajide states that most of the anti-oxidant compounds are found in the outer skin of the pomegranate, not in the soft part of the fruit. And he adds that although this has yet to be scientifically evaluated, pomegranate will be useful in any condition for which inflammation – not just neuro-inflammation – is a factor, such as rheumatoid arthritis, Parkinson’s and cancer.

The research continues and now Dr Olajide is collaborating with his University of Huddersfield colleague, the organic chemist Dr Karl Hemming. They will attempt to produce compound derivatives of punicalagin that could the basis of new, orally administered drugs that would treat neuro-inflammation.

Dr Olajide has been a Senior Lecturer at the University of Huddersfield for four years. His academic career includes a post as a Humboldt Postdoctoral Research Fellow at the Centre for Drug Research at the University of Munich. His PhD was awarded from the University of Ibadan in his native Nigeria, after an investigation of the anti-inflammatory properties of natural products.

He attributes this area of research to his upbringing. “African mothers normally treat sick children with natural substances such as herbs. My mum certainly used a lot of those substances. And then I went on to study pharmacology!”

Are Three Brain Imaging Techniques Better than One?

Many recent imaging studies have shown that in children with autism, different parts of the brain do not connect with each other in typical ways. Initially, most researchers thought that the autistic brain has fewer connections between key regions. The most recent studies, however, point to an opposite conclusion: The brains of people with autism exhibit overconnectivity.

To date, almost all studies of autism in children have used a single imaging technique to explore connectivity. None has been able to capture a robust picture of the brain abnormalities associated with autism—until now.

Two new grants from the National Institute of Mental Health (NIMH) will allow San Diego State University Psychology Professor Ralph-Axel Müller to combine three imaging techniques and harness the best of each one in his study of autism.

Techniques in tandem

Although the term “brain imaging” gets thrown around a lot when describing the latest advances in neuroscience and psychology, there are dozens of different brain imaging techniques. Each gives scientists a different view of the inner workings of the brain, and each comes with its own strengths and limitations.

For example, the frequently cited technique of fMRI, or functional magnetic resonance imaging, measures blood flow in different areas of the brain at specific snapshots in time, based on the knowledge that increased blood flow indicates increased activity of nerve cells in that area of the brain. The technique is powerful, but has limitations when it comes to detecting dynamic changes in brain activity that occur very fast, within milliseconds.

EEG (electroencephalography), a much older technique, is actually better at detecting such dynamic changes, although it cannot pinpoint exactly where in the brain the activity occurs. A powerful and more recent technique is MEG, or magnetoencephalography, which can detect dynamic changes in brain activity that happen within a few milliseconds.

Müller looks for disorganized patterns of brain activity that could be responsible for some of the telltale characteristics of autism spectrum disorder, such as inattention to social cues and repetitive and obsessive behaviors. For example, last year, Müller and his colleagues discovered that in children with autism, connectivity was impaired between the cerebral cortex and the thalamus, a deep brain structure that is important for sensorimotor functions and attention.

With $4.2 million in new funding from NIH, Müller—together with collaborators Ksenija Marinkovic at SDSU and Thomas Liu at the University of California, San Diego—will apply fMRI, EEG, and MEG to study both autistic and non-autistic, or typically-developing, children and adolescents during a variety of tests, including language tests designed to tease out activity in various parts of the brain.

Defining the differences

One component of the project will concern the visual system. Previous research has shown that people with autism rely on their visual cortex more than typically- developing people during thought processes, for example, when making a semantic distinction, such as deciding whether a truck is a vehicle. Using the one-two punch of fMRI and MEG together, Müller and his team will be able to determine the dynamic processes in how brain regions work together to come up with a response, and how these processes differ in autism.

The study will also examine brain function during its resting state in order to identify abnormalities in brain network organization. The combined use of EEG and MEG, together with fMRI techniques that reveal brain anatomy, will produce a much more complete picture of abnormal brain organization in autism.

Ultimately, Müller and his colleagues hope to identify biomarkers in the brain that can reliably indicate whether the participant falls on the autism spectrum.

“Autism is a brain-based disorder, but its diagnosis is still based entirely on behavioral observation,” Müller said. “This is inadequate. We need to find brain biomarkers for autism.”

Another goal of the researchers is to find brain biomarkers that can distinguish different subtypes of autism. It is generally suspected that the term “autism” actually covers several different disorders, each of which may be caused by different genetic and environmental risk factors. Eventually, brain biomarkers might be tied to genetic data, giving scientists a better understanding of the origins of autism, as well as new leads for treatment.

“For decades, research teams studying autism have specialized in one or another scientific technique, often without understanding well what other techniques can reveal. Our study combining several of the major imaging techniques will be one step toward a more comprehensive account of how the autistic brain differs from the typically developing one – and what may be done about it,” Müller said.

The striatum acts as hub for multisensory integration

A new study from Karolinska Institutet provides insight on how the brain processes external input such as touch, vision or sound from different sources and sides of the body, in order to select and generate adequate movements. The findings, which are presented in the journal Neuron, show that the striatum acts as a sensory ‘hub’ integrating various types of sensory information, with specialised functional roles for the different neuron types.

“The striatum is the main input structure in the basal ganglia, and is typically associated with motor function”, says Principal Investigator Gilad Silberberg at the Department of Neuroscience. “Our study focuses on its role in processing sensory input. This is important knowledge, since the striatum is implicated in numerous diseases and disorders, including Parkinson’s disease, Huntington’s disease, ADHD and Tourette syndrome.”

The striatum is the largest structure in a collection of brain nuclei called the basal ganglia, which are located at the base of the forebrain. It is involved in motor learning, planning and execution as well as selecting our actions out of all possible choices, based on the expected reward by the dopamine system. Most research performed in the striatum is focused on the motor aspects of its function, largely due to the devastating motor symptoms of the related diseases.

However, in order to select the correct actions, and generate proper motor activity it is essential to continuously process sensory information, often arriving from different sources, different sides of the body and from different sensory modalities, such as tactile (touch), visual, auditory, and olfactory. This integration of sensory information is in fact a fundamental function of our nervous system.

Patch-clamp recordings

In the current study, researchers Gilad Silberberg and Ramon Reig show that individual striatal neurons integrate sensory input from both sides of the body, and that a subpopulation of these neurons process sensory input from different modalities; touch, light and vision. The team used intracellular patch-clamp recordings from single neurons in the mouse striatum to show their responses to whisker stimulation from both sides as well as responses to visual stimulation. Neurons responding to both visual and tactile stimuli were located in a specific medial region of the striatum.

“We also showed that neurons of different types integrate sensory inputs in a different manner, suggesting that they have specific roles in the processing of such sensory information in the striatal network”, says Gilad Silberberg.

(Image: Shutterstock)

Biologists Reprogram Skin Cells to Mimic Rare Disease

Johns Hopkins stem cell biologists have found a way to reprogram a patient’s skin cells into cells that mimic and display many biological features of a rare genetic disorder called familial dysautonomia. The process requires growing the skin cells in a bath of proteins and chemical additives while turning on a gene to produce neural crest cells, which give rise to several adult cell types. The researchers say their work substantially expedites the creation of neural crest cells from any patient with a neural crest-related disorder, a tool that lets physicians and scientists study each patient’s disorder at the cellular level.

Previously, the same research team produced customized neural crest cells by first reprogramming patient skin cells into induced pluripotent stem (iPS) cells, which are similar to embryonic stem cells in their ability to become any of a broad array of cell types.

“Now we can circumvent the iPS cells step, saving seven to nine months of time and labor and producing neural crest cells that are more similar to the familial dysautonomia patients’ cells,” says Gabsang Lee, Ph.D., an assistant professor of neurology at the Institute for Cell Engineering and the study’s senior author. A summary of the study was published online in the journal Cell Stem Cell on Aug. 21.

Neural crest cells appear early in human and other animal prenatal development, and they give rise to many important structures, including most of the nervous system (apart from the brain and spinal cord), the bones of the skull and jaws, and pigment-producing skin cells. Dysfunctional neural crest cells cause familial dysautonomia, which is incurable and can affect nerves’ ability to regulate emotions, blood pressure and bowel movements. Less than 500 patients worldwide suffer from familial dysautonomia, but dysfunctional neural crest cells can cause other disorders, such as facial malformations and an inability to feel pain.

The challenge for scientists has been the fact that by the time a person is born, very few neural crest cells remain, making it hard to study how they cause the various disorders.

To make patient-specific neural crest cells, the team began with laboratory-grown skin cells that had been genetically modified to respond to the presence of the chemical doxycycline by glowing green and turning on the gene Sox10, which guides cells toward maturation as a neural crest cell.

Testing various combinations of molecular signals and watching for telltale green cells, the team found a regimen that turned 2 percent of the cells green. That combination involved turning on Sox10 while growing the cells on a layer of two different proteins and giving them three chemical additives to “rewind” their genetic memory and stimulate a protein network important for development.

Analyzing the green cells at the single cell level, the researchers found that they showed gene activity similar to that of other neural crest cells. Moreover, they discovered that 40 percent were “quad-potent,” or able to become the four cell types typically derived from neural crest cells, while 35 percent were “tri-potent” and could become three of the four. The cells also migrated to the appropriate locations in chick embryos when implanted early in development.

The team then applied a modified version of the technique to skin cells from healthy adults and found that the skin cells became neural crests at a rate similar to the team’s previous experiments.

Finally, the investigators used their regimen on skin cells from patients with familial dysautonomia, then compared these familial dysautonomia-neural crest cells to the control neural crest cells made from healthy adults. They identified 412 genes with lower activity levels in the familial dysautonomia-neural crest cells, of which 98 are involved in processing RNA products made from active genes.

According to the authors, this new observation offers insight into what goes wrong in familial dysautonomia.

“It seems as though the neural crest cells created directly from patient skin cells show more of the characteristics of familial dysautonomia than the neural crest cells we created previously from induced pluripotent stem cells,” says Lee. “That means they should be better predictors of what happens in a particular familial dysautonomia patient, and whether or not a potential treatment will work for any given individual.”

The method they devised should also be applicable to skin cells taken from people with any of the other diseases that result from dysfunctional neural crest cells, such as congenital pain disorders and Charcot-Marie-Tooth diseases, Lee says.

Can We Reconcile the Declarative Memory and Spatial Navigation Views on Hippocampal Function?

Some argue that hippocampus supports declarative memory, our capacity to recall facts and events, whereas others view the hippocampus as part of a system dedicated to calculating routes through space, and these two contrasting views are pursued largely independently in current research. Here we offer a perspective on where these views can and cannot be reconciled and update a bridging framework that will improve our understanding of hippocampal function.

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