Genetic screening for prostate cancer is now a real possibility following results from the largest-ever study into inherited risk factors for the disease. A clinical trial is likely to start this year as a result of the ground-breaking findings from an international group led by The Institute of Cancer Research, London, and the University of Cambridge, funded by Cancer Research UK and the European Commission.
The three-year study of 50,000 men (prostate cancer patients and controls without cancer) identified 23 new genetic variations associated with an increased risk of the disease. This raises the total discovered so far to 78. Significantly, 16 of the 23 newly discovered genetic changes are associated with the disease at its most aggressive and life-threatening.
None of the 23 genetic changes on its own raises a man’s risk of prostate cancer by more than a slight amount. But when a man has a number of the genetic changes these can combine to raise his risk significantly. With the genetic changes discovered, scientists can for the first time identify men who have inherited just over a 50% lifetime risk of developing prostate cancer.
Following these discoveries scientists now think they can identify the top 1% of men with the highest risk of developing prostate cancer who have 4.7 times the risk of the population average. It is these men who, it is hoped, will be identified by screening. They would then receive close monitoring in order that, if they do develop the disease, it is caught early when it is easier to treat. The way in which that screening would be conducted – for example, through blood tests or biopsies – will be indicated by the results of future clinical studies.
Study leader Professor Ros Eeles, Professor of Oncogenetics at The Institute of Cancer Research (ICR) and Honorary Clinical Consultant at The Royal Marsden NHS Foundation Trust, said: ‘These results are the single biggest leap forward in finding the genetic causes of prostate cancer yet made. They allow us, for the first time, to identify men who have a very high risk of developing prostate cancer during their lifetime through inheritance of multiple risk genetic variants. If we can show from further studies that such men benefit from regular screening, we could have a big impact on the number of people dying from the disease, which is still far too high.’
Over 40,000 men are diagnosed with prostate cancer in the UK each year, with almost 11,000 men dying from the disease. If it is caught early treatments are more effective, which is why identifying those most at risk, particularly from aggressive forms of the disease, is so important.
The team, from the ICR and the University of Cambridge, analysed 211,000 genetic variants from blood samples from 25,000 prostate cancer patients and compared them with those of a similar number of healthy men. The gene variants were analysed as part of the COGS (Collaborative Oncological Gene-environment Study) project, which publishes a series of research papers simultaneously today about the causes of prostate, breast and ovarian cancer. The Institute of Cancer Research

Prostate cancer doesn’t kill in the prostate – it’s only once the disease travels to bone, lung, liver, etc. that it turns fatal. Previous studies have shown that loss of the protein E-Cadherin is essential for this metastasis. A University of Colorado Cancer Center study describes for the first time a switch that regulates the production of E-Cadherin: the transcription factor SPDEF turns on and off production, leading to metastasis or stopping it cold in models of prostate cancer.
‘When E-Cadherin is lost, cells become ‘rogue’ – they can detach from their surrounding tissues, move effortlessly through the circulatory system, grow and attach at new sites. In prostate tumours that had lost E-Cadherin, we put in SPDEF and the tumours once again expressed E-Cadherin. They were once again anchored in place and unable to metastasise. We can make these ‘rouge’ cells back into epithelial-like cells and these epithelial cells stay anchored and lose the ability to migrate,’ says Hari Koul, PhD, investigator at the CU Cancer Center and professor and director of Urology Research at the University of Colorado School of Medicine, the study’s senior author.

In fact, the work could have implications far beyond prostate cancer, as increasing evidence points to loss of E-Cadherin as a prerequisite for metastasis in many cancers.

Koul and colleagues first showed that E-Cadherin levels varied directly with the addition or subtraction of SPDEF. Then the group artificially knocked down E-Cadherin despite the presence of SPDEF and showed that cells remained able to migrate and invade new tissues (SPDEF didn’t by itself affect metastasis and was instead dependent on modulating E-Cadherin, which is the driver). The group also showed a one-way switch – SPDEF regulates E-Cadherin, but E-Cadherin expression does nothing to affect levels of SPDEF.

‘Taken together, these studies paint a pretty compelling picture of SPDEF working in part through the modulation of E-Cadherin to inhibit prostate cancer metastasis,’ Koul says. ‘To the best of our knowledge these are the first studies demonstrating the requirement of SPDEF for expression of E-Cadherin.’

Koul says that his group is getting very close to turning off the loss of E-Cadherin in cancer cells by re-arming tumours with the gene that makes SPDEF and by testing small molecules that increase SPDEF in cancer cells.

‘This could be a real landmark,’ Koul says. ‘We see a prerequisite for metastasis and now we have a very clear picture of how to remove this necessary condition for the most dangerous behaviour of prostate cancer.’ University of Colorado Cancer Center

What genes are responsible for the development of breast cancer? What are the brain cell mutations that lead to the onset of Alzheimer’s? To find new therapies, scientists have to understand how diseases are triggered at cell level. Experiments on genetically modified mice are an indispensable part of basic medical research. Now a method has been found to help laboratories carry out their work with fewer test animals.
Scientists use genetically modified laboratory mice to investigate the underlying mechanisms of diseases. These ‘knockout’ mice carry genes or gene regions that are thought to trigger diseases.

For laboratories, the knockout technique requires a lot of time and effort. ‘Scientists start by engineering a genetic defect into embryonic stem cells,’ explains Prof. Wolfgang Wurst, who carries out research at Technische Universität München (TUM) and Helmholtz Zentrum München. ‘Then they implant the manipulated stem cells into a mouse embryo.’
After multiple steps, organisms are created which have both modified and unmodified cells. The mice have to be crossed several times until offspring are produced which carry the knockout characteristic in all of their body cells. Including all tests, it takes scientists between one and two years to produce a functioning mouse model.

But now the team led by Prof. Wurst and Dr. Ralf Kühn have developed a new method, allowing them to complete the process in a much shorter time – just a little over four months. They modified the genes directly in the fertilised mouse egg cells so that all the cells in the bodies of the offspring would have the same genetic defect. ‘By eliminating the time-consuming crossing stage, laboratories will be able to produce mouse models much quicker and with much fewer test animals,’ remarks Wurst.
The team used TALEN enzymes for its research experiments. These DNA tools have a dual function: One part recognises and binds to a particular gene, while another cuts the DNA strand in situ. These ultra-precise DNA ‘scalpels’ were developed just a few years ago.

‘TALEN enzymes have a simple, modular structure,’ says Wurst. ‘This means that we can create a number of variants to cut through all genes in the genome and modify them for a specific purpose.’ The technique will allow scientists to knock out particular genes, introduce genetic defects within cells and repair genetic defects.

‘We have used the TALEN process to implant mutations associated with human dementia in mouse germ cells. These animal models will help us understand the molecular mechanisms behind dementia. The advantage of the technique is that we will in principle be able to model all hereditary diseases in the test mice,’ adds Wurst. Technische Universität München

Johns Hopkins scientists have found out how a gout-linked genetic mutation contributes to the disease: by causing a breakdown in a cellular pump that clears an acidic waste product from the bloodstream. By comparing this protein pump to a related protein involved in cystic fibrosis, the researchers also identified a compound that partially repairs the pump in laboratory tests.
The mutation in question, known as Q141K, results from the simple exchange of one amino acid for another, but it prevents the protein ABCG2 from pumping uric acid waste out of the bloodstream and into urine. A build-up of uric acid in the blood can lead to its crystallisation in joints, especially in the foot, causing excruciatingly painful gout.
‘The protein where the mutation occurs, ABCG2, is best known for its counterproductive activity in breast cancer patients, where it pumps anti-cancer drugs out of the tumour cells we are trying to kill,’ says William Guggino, Ph.D., professor and director of the Department of Physiology at the Johns Hopkins University School of Medicine. ‘In kidney cells, though, ABCG2 is crucial for getting uric acid out of the body. What we figured out is exactly how a gout-causing genetic mutation inhibits ABCG2 function.’
Gout affects 2 to 3 percent of Americans, approximately 6 million people. It usually involves sudden attacks of severe pain, often in the joint at the base of the big toe and frequently in the wee hours of the morning, when body temperature is lowest. It has been nicknamed the ‘disease of kings,’ because it usually results from high-purine diets, food that only kings and other noblemen could afford in large quantities in bygone years: red meat, organ meats, oily fishes and some vegetables like asparagus and mushrooms.
Guggino notes that the ABCG2 Q141K mutation was first connected with gout in 2008 through a large genomic study directed, in part, by Josef Coresh, M.D., a biostatistician and epidemiologist at the Johns Hopkins University School of Public Health. At the time, Guggino’s laboratory was studying a protein frequently found mutated in cystic fibrosis patients: cystic fibrosis transmembrane conductance regulator, or CFTR. The structure of ABCG2 is quite similar to CFTR’s, so Coresh suggested that Guggino’s team apply their knowledge of CFTR to characterise ABCG2.
The team first genetically engineered several standard mammalian cell types to make regular or mutant versions of ABCG2. Cells with the mutated ABCG2 gene contained much less of the ABCG2 protein than cells making the regular form. Additionally, the researchers found that the mutation made it difficult for ABCG2 molecules to get to their proper place on the cell surface. Since ABCG2 pumps molecules from the inside of the cell to the outside, it is not functional anywhere but the cell surface.
The team then lowered the temperature at which the ABCG2-making cells were growing, and found more mutant ABCG2 at the cell surface. Guggino says this finding suggested that the lower temperature had stabilised ABCG2 and helped it achieve its proper 3-D conformation, because proteins that don’t assume the right shape are likely to be broken into pieces for reuse, preventing them from reaching their final destinations.
When ABCG2 and CFTR are lined up, their structures are very similar. In fact, one of the most common cystic fibrosis mutations, a CFTR deletion of amino acid F508, lines up next to the Q141K mutation in ABCG2 and causes similar results in the protein’s location and processing.
Knowing that the F508 deletion in CFTR creates instability in a certain part of the protein, the researchers introduced additional mutations intended to stabilise the wobbly region of the Q141K mutant ABCG2. As predicted, they found that this stabilisation increased the amount of ABCG2 on the cell surface, suggesting again that ABCG2 had been saved from the recycling bin.
To confirm the involvement of the recycling process, the team fed the cells several small molecules known to help malformed proteins avoid degradation. One molecule, VRT-325, partially restores CFTR’s activity. The same molecule was also able to increase the amount of mutant ABCG2 found in the cells and on their surfaces, and to decrease the amount of uric acid in the cells, bringing it within the normal range.
‘Though there are many more lab tests needed before clinical trials can even be designed, our results represent an important step forward in both understanding how gout results from this mutation and finding a treatment,’ says Guggino. John Hopkins Medicine