Normal skin contains an unexpectedly high number of cancer-associated mutations, according to a study. The findings illuminate the first steps cells take towards becoming a cancer and demonstrate the value of analysing normal tissue to learn more about the origins of the disease.

The study revealed that each cell in normal facial skin carries many thousands of mutations, mainly caused by exposure to sunlight. Around 25 per cent of skin cells in samples from people without cancer were found to carry at least one cancer-associated mutation.

Ultra-deep genetic sequencing was performed on 234 biopsies taken from four patients revealing 3,760 mutations, with more than 100 cancer-associated mutations per square centimetre of skin. Cells with these mutations formed clusters of cells, known as clones, that had grown to be around twice the size of normal clones, but none of them had become cancerous.

‘With this technology, we can now peer into the first steps a cell takes to become cancerous,’ explains Dr Peter Campbell, a corresponding author from the Wellcome Trust Sanger Institute. ‘These first cancer-associated mutations give cells a boost compared to their normal neighbours. They have a burst of growth that increases the pool of cells waiting for the next mutation to push them even further.

‘We can even see some cells in normal skin that have taken two or three such steps towards cancer. How many of these steps are needed to become fully cancerous? Maybe five, maybe 10, we don’t know yet.’

The mutations observed showed the patterns associated with the most common and treatable form of skin cancer linked to sun exposure, known as cutaneous squamous cell carcinoma, rather than melanoma, a rarer and sometimes fatal form of skin cancer.

‘The burden of mutations observed is high but almost certainly none of these clones would have developed into skin cancer,’ explains Dr Iñigo Martincorena, first author from the Sanger Institute. ‘Because skin cancers are so common in the population, it makes sense that individuals would carry a large number of mutations. What we are seeing here are the hidden depths of the iceberg, not just the relatively small number that break through the surface waters to become cancer.’

Skin samples used in this study were taken from four people aged between 55 and 73 who were undergoing routine surgery to remove excess eyelid skin that was obscuring vision. The mutations had accumulated over each individual’s lifetime as the eyelids were exposed to sunshine. The researchers estimate that each sun-exposed skin cell accumulated on average a new mutation in its genome for nearly every day of life.

‘These kinds of mutations accumulate over time – whenever our skin is exposed to sunlight, we are at risk of adding to them,’ explains Dr Phil Jones, a corresponding author from the Sanger Institute and the MRC Cancer Unit at the University of Cambridge. ‘Throughout our lives we need to protect our skin by using sun-block lotions, staying away from midday sun and covering exposed skin wherever possible. These precautions are important at any stage of life but particularly in children, who are busy growing new skin, and older people, who have already built up an array of mutations.’

Recent studies analysing blood samples from people who do not have cancer had revealed a lower burden of mutations, with only a small percentage of individuals carrying a cancer-causing mutation in their blood cells. Owing to sun exposure, skin is much more heavily mutated, with thousands of cancer-associated mutations expected in any adult’s skin.

The results demonstrate the potential of using normal tissue to better understand the origins of cancer. The Cancer Genomics group at the Sanger Institute will continue this work with larger sample numbers and a broader range of tissues to understand how healthy cells transition into cancerous cells. Sanger Institute

Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), in cooperation with colleagues at the University of Zurich and the Ruhr-Universität Bochum, have for the first time successfully tested a new tumour diagnosis method under near-real conditions. The new method first sends out an antibody as a ‘spy’ to detect the diseased cells and then binds to them. This antibody in turn attracts a subsequently administered radioactively labelled probe. The scientists could then clearly visualize the tumour by utilizing a tomographic method. This procedure could improve cancer treatment in the future by using internal radiation.

The human immune system forms antibodies that protect the body from pathogens. Antibodies can also, however, be produced in a laboratory to precisely bind to tumour cells. They are used in cancer research to detect and fight malignant tumours. For example, antibodies can serve as transport vehicles for radionuclides, with which the affected regions can be visualized or can even be damaged. Until recently, a stumbling block has been their large molecular mass. “This causes them to circulate in the body for too long before they reach the diseased cells,” explains Dr Holger Stephan from the Institute of Radiopharmaceutical Cancer Research at HZDR. ‘This is a disadvantage because organs that are not affected by the disease are exposed to radiation. It also makes the exact localization of the tumour in the body more difficult because the resulting images are less sharp.”

Together with colleagues at the University of Zurich and the Ruhr-Universität Bochum, the researchers from Dresden therefore chose an alternative strategy. “By using what is known as ‘pre-targeting’, the antibodies’ task is divided into two steps,” Dr Kristof Zarschler, a member of Stephan’s team, explains. “In a figurative sense, we first send spies out in advance, over a longer period of time, to scout out the enemy – the tumour cells. The ‘spies’ then share their position with their troops, which we subsequently send out so that they will directly reach their target with the radioactive material.” The researchers fall back on the cetuximab antibody as the scout, which binds selectively to the epidermal growth factor receptor (EGFR). In various types of tumours, there is an increase in this molecule’s formation or it might be found in a mutated form, which then leads the cells to grow and multiply uncontrolled.

The Dresden researchers combined the antibody with a peptide nucleic acid (PNA) derivative which Prof Gilles Gasser and Prof Nils Metzler-Nolte developed together with their respective working groups in Switzerland and Germany. “It is a very stable synthetic variant of DNA,’ says Holger Stephan. “Similar to a single strand of DNA, it consists of a certain sequence of the four organic bases. Complementary PNA with matching sequence binds to it in a highly precise and stable manner.” During their experiments, the scientists first injected the PNA-EGFR antibody into tumour-bearing mice and gave this “spy” time to accumulate at the tumour site. They then administered the PNA counterpart, labelled with the radioactive substance technetium-99m. “Images we took using single photon emission computed tomography show that both the antibody and its counterpart located each other quickly,” says Zarschler, pleased with the results.

The tumour could thus be clearly visualized within a short period of time. “Furthermore, the radioactively labelled probes had already disappeared from the bloodstream after sixty minutes,” explains Holger Stephan. “This minimizes radioactive exposure risk of healthy body tissue. By pre-targeting, we can overcome limitations of conventional, radioactively marked antibodies.” According to the researchers, it will, however, take some time before the combination of PNA antibodies and their matching PNA counterparts can be used in diagnosing tumours in humans.

“Our results however show that the PNAs we tested are suitable candidates for further preclinical studies,” Stephan sums up. They could provide new possibilities not only for visualizing diseased cells but also for fighting them. “If the method is proven to work, it could also be used to transport therapeutically effective radioactive substances to the tumour in order to irradiate it from within and ultimately damage it.” Helmholtz-Zentrum Dresden-Rossendorf

Researchers at The University of Texas Health Science Center at Houston (UTHealth) are helping to make precision medicine a reality by sequencing entire exomes of people to assess chronic disease risk and drug efficacy.

For years, scientists have been using a method called “knockout mice,” which allows them to study gene functions by inactivating a gene in mice and then observing how it affects the mice. Now, UTHealth researchers are using new methods to study naturally occurring “knockout humans.”

Rather than genetically engineer human gene mutations in the lab, UTHealth researchers scanned 8,554 exomes, the protein-encoding portion of the genome, of African Americans and European Americans in the United States for naturally occurring mutations that inactivate a certain gene. A typical human exome has dozens of these loss-of-function gene variants.

“Years ago, we found a mutation that knocks out a gene that lowers your cholesterol. That turned into drugs that can help with cholesterol. That was with one gene. We are now sequencing lots of people and looking at where people are losing function from every gene in their body,” said Eric Boerwinkle, Ph.D., senior author, professor and chair of the Human Genetics Center and the Department of Epidemiology, Human Genetics and Environmental Sciences at UTHealth School of Public Health.

The study participants were part of Atherosclerosis Risk in Communities (ARIC), a study conducted by the National Heart, Lung and Blood Institute (NHLBI). The group was measured for 20 phenotypes related to chronic diseases, such as serum magnesium levels, triglyceride levels, blood pressure and cholesterol.

By observing how certain mutations affect health, researchers were able to identify eight new relationships between genes and diseases and confirm the already established relationship between gene variant PCSK9 and lower blood cholesterol and lower heart disease risk.

A heterozygous form of gene TXNDC5 was found to be related to Type 1 Diabetes progression and elevated fasting glucose levels. A recessive form of C1QTNF8 was related to elevated serum magnesium levels and participants who had a mutation of SEPT10 had significantly reduced lung function.

“Loss-of-function variation in certain genes, such as TXNDC5, may predispose individuals to develop disease. More research is needed to determine the exact mechanisms of these newly discovered relationships,” said Boerwinkle, who is also the Kozmetsky Family Chair in Human Genetics at UTHealth. University of Texas at Houston Health Science Center

Unreliable oestrogen measurements have had a negative impact on the treatment of and research into many hormone-related cancers and chronic conditions. To improve patient care, a panel of medical experts has called for accurate, standardized oestrogen testing methods in a statement published in the Endocrine Society’s Journal of Clinical Endocrinology & Metabolism (JCEM).
The panel’s recommendations are the first to address how improved testing methods can affect clinical care, and were developed based on discussions at an oestrogen measurement workshop hosted by the Endocrine Society, AACC and the Partnership for Accurate Testing of Hormones (PATH).

Oestrogen is primarily produced in the ovaries and is also produced in small amounts by the adrenal glands, which is why men as well as women have oestrogen in their bodies. It is critical for fertility in women, and also plays a role in many health conditions, from precocious puberty to cancers of the breast, ovary, prostate and liver. Accurate blood tests for oestrogen are necessary to diagnose patients with these conditions and ensure they receive appropriate, effective treatment. Many medical studies also rely on oestrogen tests, such as research assessing the connection between oestrogen levels and the risk of breast or prostate cancer.

“Accurate data on patients’ oestrogen levels are needed to ensure appropriate and effective patient care, reduce the need for retesting, and enable clinicians to implement the latest research in patient care,” said one of the authors and co-chair of the PATH Steering Committee, Hubert Vesper, PhD. “Research studies, however, found high inaccuracies among different oestrogen tests, especially when the test is measuring low oestrogen levels in postmenopausal women, men and children.”

The expert panel called for improving the accuracy of measurements through standardization, and recommended clinicians, researchers and public health officials support standardization programs like CDC’s and other efforts to ensure oestrogen measurement is accurate and consistent.

The panel also advised clinicians and researchers to consider the purpose of the test when selecting an oestrogen measurement method. Clinicians and researchers currently use several methods to measure oestrogen, including mass spectrometry and immunoassays. The experts agreed both methods are valid, but that one may be more effective than the other depending on the situation. For instance, mass spectrometry—the more expensive, but also more sensitive testing method—may be appropriate in people who tend to have low oestrogen levels, including postmenopausal women and children beginning puberty.

Additionally, the experts recommended that medical journals require authors to fully explain the oestrogen measurement testing methods used in studies. Ensuring researchers explain the processes they used will help the field move toward standardized methods. The Endocrine Society

Scientists at The Scripps Research Institute (TSRI) and the Salk Institute for Biological Studies have discovered how a mutant protein triggers nerve damage in a subtype of Charcot-Marie-Tooth (CMT) diseases, a group of currently untreatable conditions that cause loss of function in a person’s hands and feet.

The new research suggests future therapies may target this haywire protein, restoring nerve function in patients with CMT.

“This is the first major advancement toward a molecular mechanistic understanding of CMT subtype CMT2D,” said TSRI Professor Xiang-Lei Yang, senior author of the new study with Samuel Pfaff, a neuroscience professor at the Salk Institute and a Howard Hughes Medical Institute investigator. “These findings will help us develop future diagnostics and treatments.”

CMT is one of the most common inherited neurological diseases, affecting about one in 2,500 people. Genetic sequencing usually turns up an array of mutations in people with CMT, making it difficult to pin down the gene responsible and develop a treatment.

In the new study, researchers focused on a protein called glycyl-tRNA synthetase (GlyRS), which is altered in people with disease subtype CMT2D.

Previous work by Yang and her colleagues showed that mutant forms of GlyRS open up their molecular structure to reveal binding components inside—a bit like opening Velcro to reveal the sticky components.

Until now, it was not clear how mutant GlyRS harmed patients.

The work in Yang’s lab, spearheaded by TSRI graduate student Weiwei He, revealed that mutant GlyRS can interact with the Nrp1 receptor on cells. Normally, a growth factor, called vascular endothelial growth factor (VEGF), binds to part of the receptor and relays signals to maintain nerve health.

A postdoctoral researcher in the Yang lab, Huihao Zhou, found that opened-up, mutant GlyRS can bind to the same part of the Nrp1 receptor, blocking the signals for nerve maintenance. This causes motor neurons to decline and even die, breaking the connection between the brain and muscles in the limbs. “GlyRS competes with VEGF,” explained Yang.

Researchers at Salk further confirmed this finding by observing the effect of mutant GlyRS in mouse models of CMT. The team, including Salk Staff Scientist Ge Bai, used gene therapy techniques to ramp up VEGF production in mouse models. Higher levels of VEGF out-competed GlyRS, restoring function in the Nrp1 receptor. The mice with CMT regained some muscle strength and showed significant improvements in CMT symptoms.

“This solves a long-running mystery of how a gene mutation damages the neurons that carry information from the spinal cord to our muscles, resulting in a range of sensory and movement problems,” said Pfaff. “It’s an exciting finding, as we were able in experiments to reduce the symptoms of the disease by targeting the activity of these proteins.”

The next step is to develop targeted strategies that could recognize and intercept GlyRS mutants before they block VEGF. Yang is currently working to screen possible antibodies in collaboration with Kim Janda, the Ely R. Callaway Jr. Professor of Chemistry and member of the Skaggs Institute for Chemical Biology at TSRI.

The new study also has broader implications outside the subtype of CMT examined in these experiments. Yang said mutant GlyRS’s abnormal interaction with Nrp1 is a crucial clue for understanding nerve damage. “This could shed light on the mechanisms behind other forms of CMT,” said Yang. The Scripps Research Institute