Researchers have identified a potential new pathway in prostate cancer cells by which cancer-driving gene products can be generated, according to a study.
‘Our work shows that cancers have many more tricks than we thought to generate potential cancer-driving genes or gene products,’ said Hui Li, Ph.D., assistant professor of pathology at the University of Virginia in Charlottesville, and a recipient of an Innovative Research Grant from Stand Up To Cancer (SU2C). The AACR is the scientific partner of SU2C.
Gene fusion is a common characteristic of human cancers. In many cases, the protein products of these gene fusions, which are generated via an RNA intermediate, have a key role in the genesis of the cancer. A well-characterised example of this is the protein that drives chronic myeloid leukaemia, BCR-ABL, which is generated via RNA intermediates from a fusion gene formed by chromosomal translocation — an event involving exchange of genomic DNA between two distinct chromosomes.
‘For many years, chromosomal translocation was considered the sole way in which single RNAs consisting of copies of parts of two genes, so-called fusion RNAs, could be generated,’ said Li. ‘We have shown that fusion RNAs can be generated without changes to DNA by a new mechanism that we are calling cis-SAGe [cis-splicing of adjacent genes].’ Recently, a fusion RNA formed from parts of the SLC45A3 and ELK4 genes was identified in prostate cancer cells in the absence of any DNA alterations. Li and his colleagues confirmed in two prostate cancer cells lines that the SLC45A3-ELK4 fusion RNA could be detected even though there was no evidence of genomic DNA rearrangement.
Detailed molecular analysis of the prostate cancer cell lines indicated that the SLC45A3-ELK4 fusion RNA was generated by cis-SAGe. SLC45A3 and ELK4 are neighbouring genes, and cis-SAGe occurred when an RNA that crossed the boundary between the two genes was formed.
The protein CCCTC-binding factor normally acts to insulate SLC45A3 and ELK4 from each other. Li and his colleagues found that levels of this protein at the gene boundary inversely correlated with the amount of SLC45A3-ELK4 fusion RNA generated, providing molecular insight into how the quantity of this fusion RNA could be regulated.
A functional role for the SLC45A3-ELK4 fusion RNA in prostate cancer was suggested by two observations. First, it promoted the growth of the two prostate cancer cell lines in culture. Second, its levels in human prostate samples correlated with prostate cancer disease progression — normal prostate tissue expressed the lowest levels and prostate cancer specimens from men with metastatic disease expressed the highest levels.
‘These data are not sufficient to say that the SLC45A3-ELK4 fusion RNA has a causal role in prostate cancer,’ said Li. ‘But they are highly suggestive, and I am very excited that this high-risk project, which I would not have been able to pursue without the grant from Stand Up To Cancer, has uncovered what seems to be a new way in which cancer can be driven.’ EurekAlert

Why do some people experience post-traumatic stress disorder (PTSD) while others who suffered the same ordeal do not? A new UCLA study may shed light on the answer.

UCLA scientists have linked two genes involved in serotonin production to a higher risk of developing PTSD. The findings suggest that susceptibility to PTSD is inherited, pointing to new ways of screening for and treating the disorder.

‘People can develop post-traumatic stress disorder after surviving a life-threatening ordeal like war, rape or a natural disaster,’ said lead author Dr. Armen Goenjian, a research professor of psychiatry at the Semel Institute for Neuroscience and Human Behavior at UCLA. ‘If confirmed, our findings could eventually lead to new ways to screen people at risk for PTSD and target specific medicines for preventing and treating the disorder.’

PTSD can arise following child abuse, terrorist attacks, sexual or physical assault, major accidents, natural disasters or exposure to war or combat. Symptoms include flashbacks, feeling emotionally numb or hyper-alert to danger, and avoiding situations that remind one of the original trauma.

Goenjian and his colleagues extracted the DNA of 200 adults from several generations of 12 extended families who suffered PTSD symptoms after surviving the devastating 1988 earthquake in Armenia.

In studying the families’ genes, the researchers found that persons who possessed specific variants of two genes were more likely to develop PTSD symptoms. Called TPH1 and TPH2, these genes control the production of serotonin, a brain chemical that regulates mood, sleep and alertness — all of which are disrupted in PTSD.

‘We suspect that the gene variants produce less serotonin, predisposing these family members to PTSD after exposure to violence or disaster,’ Goenjian said. ‘Our next step will be to try and replicate the findings in a larger, more heterogeneous population.’

PTSD affects about 7 percent of Americans and has become a pressing health issue for a large percentage of war veterans returning from Iraq and Afghanistan. The UCLA team’s discovery could be used to help screen people who may be at risk for developing PTSD.

‘A diagnostic tool based upon TPH1 and TPH2 could enable military leaders to identify soldiers who are at higher risk of developing PTSD and reassign their combat duties accordingly,’ Goenjian said. ‘Our findings may also help scientists uncover alternative treatments for the disorder, such as gene therapy or new drugs that regulate the chemicals responsible for PTSD symptoms.’

According to Goenjian, pinpointing genes connected with PTSD symptoms will help neuroscientists classify the disorder based on brain biology instead of clinical observation. Psychiatrists currently rely on a trial-and-error approach to identify the best medication for controlling an individual patient’s symptoms. UCLA

Research on an investigational DNA methylation test for colorectal cancer demonstrated that the only clinical variable that influenced test results was age, according to findings presented by researchers from the Mayo Clinic in Rochester, USA, at the AACR Annual Meeting 2012, held from March 31 – April 4. The group at the Mayo Clinic, in collaboration with Exact Sciences, developed the multimarker molecular stool test, which is highly sensitive to the critical cancer screening targets of early-stage cancers and precancerous adenomas. The researchers examined common patient variables, including age, gender, race, alcohol consumption, tobacco use, body mass and medication use in 500 patients undergoing screening colonoscopy or polyp follow-up. Patients had a normal colonoscopy in the last three years.With the exception of age, none of the variables influenced test results, nor did family history of colorectal cancer or polyps or personal history of polyps. Researchers have now selected the two markers least affected by age for further test development and validation based on these study results to try and minimise false positives and avoid unnecessary colonoscopies.

A new genetic mutation that causes familial amyotrophic lateral sclerosis (ALS), a fatal neurological disorder also known as Lou Gehrig’s Disease, has been identified by a team of scientists led by researchers at the University of Massachusetts Medical School (UMMS). Mutations to the profilin (PFN1) gene, which is essential to the growth and development of nerve cell axons, is estimated to account for one to two percent of inherited ALS cases. The finding points to defects in a neuron’s cytoskeleton structure as a potential common feature among diverse ALS genes.
‘This discovery identifies what may possibly be a common biological mechanism involved across familial ALS cases regardless of genetics,’ said John Landers, PhD, associate professor of neurology and senior author of the study. ‘We know of at least three other ALS genes, in addition to PFN1, that adversely impact axon growth. If indeed, this is part of the disease’s mechanism, then it might also be a potential target for therapeutics.’
Robert Brown, MD, DPhil, a co-author on the study and chair of neurology at UMass Medical School, said ‘Dr. Landers has done great work in defining this new pathway for motor neuron death. We are delighted to have identified the defects in families from the U.S., Israel and France that we have been investigating for several years. Our finding is particularly exciting because it may provide new insights into ALS treatment targets.’
ALS is a progressive, neurodegenerative disorder affecting the motor neurons in the central nervous system. As motor neurons die, the brain’s ability to send signals to the body’s muscles is compromised. This leads to loss of voluntary muscle movement, paralysis and eventually respiratory failure. The cause of most cases of ALS is not known. Approximately 10 percent of cases are inherited. Though investigators at UMass Medical School and elsewhere have identified several genes shown to cause inherited or familial ALS, almost 50 percent of these cases have an unknown genetic cause.
The current study details the discovery of the PFN1 gene mutation among two large ALS families. Both families were negative for known ALS-causing mutations and displayed familial relationships that suggested a dominant inheritance mode for the disease. For each family, two affected members with maximum genetic distance were selected for deep DNA sequencing. To identify an ALS-causing mutation, genetic variations between the family members were identified and screened against known databases of human genetic variation, such as the 1000 Genomes Project. This narrowed down the resulting number of candidate, ALS-causing mutations to two within the first family and three within the second. Interestingly, both families contained different mutations within the same gene – PFN1, the likely causative mutation. With additional screening, the team documented that in a total of 274 families sequenced, seven contained a mutation to the PFN1 gene, establishing it as a likely cause for ALS.
While it is not certain how the PFN1 mutation causes ALS, the cellular functions it controls within the motor neurons are responsible for regulation of a number of activities, including the growth and development of the axon, the slender projection through which neurons transmit electrical impulses to neighboring cells, such as muscle. When introduced into motor neuron cells, normal PFN1 protein was found diffused throughout the cytoplasm. Conversely, the mutant PFN1 observed in ALS patients was found to collect in dense aggregates, keeping it from functioning properly. Motor neurons producing mutated PFN1 showed markedly shorter axon outgrowth.
‘The discovery that mutant PFN1 interferes with axon outgrowth was very exciting to us,’ said Claudia Fallini, PhD, a postdoctoral researcher at Emory University School of Medicine who collaborated with the UMass Medical School authors to investigate PFN1’s functions in cultured motor neurons. ‘It suggests that alterations in actin dynamics may be an important mechanism at the basis of motor neuron degeneration.’
‘In healthy neurons, PFN1 acts almost like a railroad tie for fibrous filaments called actin, which make up the axon’ said Landers. ‘PFN1 helps bind these filaments to each other, promoting outgrowth of the axon. Without properly functioning PFN1 these filaments can’t come together. Here we show that mutant PFN1 may contribute to ALS pathogeneses by accumulating in these aggregates and altering the actin dynamics in a way that inhibits axon outgrowth.’ EurekAlert

Researchers at National Jewish Health have discovered a novel genetic mechanism of immune deficiency. Magdalena M. Gorska, MD, PhD, and Rafeul Alam, MD, PhD, identified a mutation in Unc119 that causes immunodeficiency known as idiopathic CD4 lymphopenia. Unc119 is a signalling protein that activates and induces T cell proliferation. The mutation impairs Unc119 ability to activate T cells.
‘A better understanding of the molecular mechanisms associated with this mutation will improve diagnosis and pave the way for development of new therapies,’ said Dr. Gorska.
Nearly a decade ago Drs. Alam and Gorska identified Unc119 as a novel activator of SRC-type tyrosine kinases, important regulators of cellular function. Since then, they have published numerous papers where they characterised the function of this protein in various aspects of the immune system.
Idiopathic CD4 lymphopenia is a rare and heterogeneous syndrome defined by low levels of CD4 T cells in the absence of HIV infection, which predisposes patients to infections and malignancies. Recent research by others had linked the syndrome to reduced activation of the SRC-type kinase known as Lck. The latter kinase is involved in T cell development, activation and proliferation.
So, Drs. Alam and Gorska thought Unc119, an activator of Lck, might be involved. They kept an eye out for patients with CD4 lymphopenia coming to National Jewish Health, which specialises in immune-related disorders as well as respiratory and cardiac diseases. They identified three patients with CD4 lymphopenia, then sequenced their Unc119 gene as well as the Unc119 gene in several patients who suffered low CD4 T cell counts as a result of other conditions.
One of the three patients, a 32-year-old woman with a history of recurrent infections, had a missense mutation in her Unc119 gene. The same mutation was not present in other lymphopenia patients nor in any genetic database.
The researchers then performed several studies with the woman’s blood cells, to understand the mutation’s effect. They introduced the mutated gene into normal T cells and examined the outcome.
The mutation prevents Lck activation and its downstream signalling. It also reduces the amount of Lck found near the plasma membrane, where it plays a major role in propagating signals from the T-cell receptor. Proliferation of T cells, which normally occurs on stimulation of T-cell receptors, was profoundly reduced in cells from the patient.
‘Since we originally published our findings earlier this year, we have received inquiries from many physicians with lymphopenia subjects,’ said Dr. Alam. ‘Working with them, we expect to find several more patients with this novel mutation, which should help us better understand its effect, improve diagnosis and possibly find therapies.’
At this point there is no treatment for CD4 lymphopenia caused by this mutation other than close monitoring of the patient and treatment of resulting infections and malignancies. National Jewish Health