New research by an international team including Keck Medicine of USC scientists is bringing the origins of ovarian cancer into sharper focus.

The study highlights the discovery of three genetic variants associated with mucinous ovarian carcinomas (MOCs), offering the first evidence of genetic susceptibility in this type of ovarian cancer. The research also suggests a link between common pathways of development between MOCs and colorectal cancer and for the first time identifies a gene called HOXD9, which turns genes on and off, and provides clues about the development of MOCs.

‘It remains a mystery where these cancers come from,’ said Simon Gayther, Ph.D., professor in preventive medicine, Keck School of Medicine of USC, corresponding author of the international genome-wide association study (GWAS). ‘By finding these genetic markers, we begin to understand more about the biology of the disease itself. This study tells us more about the biology of ovarian cancer from the early development stage than most research has.’

Ovarian cancer is the fourth leading cause of cancer in American women and seventh most common cancer in women throughout the world (World Health Organization). In 2015, more than 14,000 American women will die of ovarian cancer, according to the American Cancer Society.

Most ovarian cancers have low survival rates, typically because of the misunderstanding of symptoms and discovery of the cancer in later, less treatable stages. ‘Although MOCs are a less common type of ovarian cancer with generally good prognosis when diagnosed in early stages, they are twice as likely to be resistant to treatment at later stages,’ said Andrew Berchuck, M.D., director of gynecologic oncology at Duke University Cancer Institute, and senior author of the study. ‘Our results will contribute to the identification of women at greatest risk of developing the disease with the long-term goal of prevention.’

The association analysis was based on 1,644 women diagnosed with MOC and more than 21,000 women without ovarian cancer. The research was conducted as part of the Collaborative Oncological Gene-environment Study (COGS), launched in 2009 with the goal of determining risks of breast, ovarian and prostate cancer. EurekAlert

Practically everyone gets fatter as they get older, but some people can blame their genes for the extra padding. Researchers have shown that two different mutations in a gene called ankyrin-B cause cells to suck up glucose faster than normal, fattening them up and eventually triggering the type of diabetes linked to obesity.

The more severe of the two mutations, called R1788W, is carried by nearly one million Americans. The milder mutation, known as L1622I, is shared by seven percent of the African American population and is about as common as the trait for sickle cell anaemia.

The findings, which were generated in mice, could help identify at-risk individuals who might be able to tip the scales back in their favour by eating better and exercising more.

“This is one of the first examples of a susceptibility gene that would only be manifested through a modern lifestyle,” said Vann Bennett, M.D., Ph.D., senior author of the study and George Barth Geller Professor of Biochemistry, Cell Biology, and Neurobiology at Duke University School of Medicine. “The obesity epidemic really took off in the 1980’s, when sugary sodas and French fries became popular. It’s not like we suddenly changed genetically in 1980, but rather we have carried susceptibility genes that were exacerbated by this new diet. We think our findings are just the beginning, and that there are going to be many genes like this.’

Bennett, who is also an investigator with the Howard Hughes Medical Institute, discovered ankyrin-B more than thirty years ago. He found that ankyrin-B acts as a kind of protein anchor, tethering important proteins to the inside of the cell’s plasma membrane. Since his initial discovery, Bennett and other researchers have implicated defects in ankyrin-B in a wide variety of human afflictions, including irregular heartbeat, autism, muscular dystrophy, aging, and, more recently, diabetes.

Diabetes is quickly becoming one of the greatest threats to public health, as waistlines expand around the world and here in the United States. If the current trends continue, one in three Americans will have diabetes by 2050. Patients with type 1 diabetes do not make enough insulin, the hormone that helps process the glucose that builds up in the bloodstream after a meal. Patients with type 2 diabetes, the form linked to obesity, make insulin but become resistant to its effects.

Several years ago, the Bennett laboratory found evidence that ankyrin-B mutations might play a role in insulin secretion and metabolism. Since then, several studies have uncovered rare ankyrin-B variants that are associated with type 2 diabetes. One mutation, called R1788W, was more common in Caucasians and Hispanics. Another, called L1622I, was found exclusively in African-Americans, a group known to be at a particularly high risk of diabetes. But it was still unclear how these changes in the genetic code could set a course for diabetes.

To get at that answer, Bennett’s MD/PhD student Jane Healy created mouse models that carried these same human genetic variants. She and her colleagues found that animals with two copies of the R1788W mutation made less insulin than normal mice. Despite this shortcoming, their blood glucose levels were normal. So the researchers performed the rodent equivalent of a glucose tolerance test –- commonly used to screen for type 2 diabetes in people — to determine how quickly glucose was cleared from the bloodstream in the mutant mice. To their surprise, the mutant mice metabolized glucose more quickly than normal mice.

“We thought that the main problem in these mice would be with the beta cells that produced and secreted insulin,’ said Healy, co-author of the study and a former trainee in Bennett’s laboratory. “Instead, our most significant finding lay with the target cells, which took up much more glucose than expected.”

Glucose doesn’t enter cells and tissues all on its own, but instead has to rely on a second molecule, called GLUT4 transporter, to gain access. Normally, GLUT4 hangs out in the cell, like a hostess waiting for party guests to arrive. When insulin is present it acts as a kind of doorbell, alerting GLUT4 to spring into action and open the door to let glucose into the cell. When insulin goes away, the GLUT4 transporters close the door, turn around, and go back into the middle of the cell.

However, postdoctoral fellow Damaris Lorenzo, Ph.D., found that wasn’t the case with the mutant mice. After conducting a number of biochemistry experiments, Lorenzo ddiscovered that the mice had lots of GLUT4 on the surface of their muscle and fat cells even when there wasn’t any insulin around. That meant that glucose could flow in without necessarily having to bother with the doorbell.

This open door policy was an advantage when they were young, because it protected the animals from low insulin levels. But when the mice got older — or switched to a particularly high-fat diet — it made the mice fatter and, eventually, led them to become insulin resistant.

The researchers believe that long ago, the R1788W mutation — and the milder L1622I mutation — may have provided an evolutionary advantage. Aging hunter-gatherer types, who weren’t as effective at chasing down their next meal, needed to gain as much fat as possible to avoid starvation. Now that high-fat, high-calorie foods are plentiful in much of the world, these variants put people at increased risk for modern afflictions like obesity and diabetes. Duke University

Building on their discovery of a gene linked to eating disorders in humans, a team of researchers at the University of Iowa has now shown that loss of the gene in mice leads to several behavioural abnormalities that resemble behaviours seen in people with anorexia nervosa.

The team, led by Michael Lutter, MD, PhD, assistant professor of psychiatry in the UI Carver College of Medicine, found that mice that lack the oestrogen-related receptor alpha (ESRRA) gene are less motivated to seek out high-fat food when they are hungry and have abnormal social interactions. The effect was stronger in female mice, which also showed increased obsessive-compulsive-like behaviours.

The study also shows that ESRRA levels are controlled by energy status in the mice. Restricting calorie intake to 60 percent of normal over several days significantly increased levels of ESRRA in the brains of normal mice.

“Decreased calorie intake usually motivates animals, including humans, to seek out high-calorie food. These findings suggest that loss of ESRRA activity may disrupt that response,” Lutter says.

Anorexia nervosa and bulimia nervosa are common and severe mental illnesses. Lutter notes that although 50 to 70 percent of the risk of getting an eating disorder is inherited, identifying the genes that mediate this risk has proven difficult. Learn more about the treatment of eating disorders at UI Hospitals and Clinics.

ESRRA is a transcription factor—a gene that turns on other genes. Lutter and his colleagues previously found that a mutation that reduces ESRRA activity is associated with an increased risk for eating disorders in human patients. Although ESRRA is expressed in many brain regions that are disrupted in anorexia, almost nothing was known about its function in the brain. In the new study Lutter’s team manipulated ESRRA in mice to investigate the gene’s role in behaviour. University of Iowa Hospitals and Clinics

Chemists at Caltech have developed a new sensitive technique capable of detecting colorectal cancer in tissue samples—a method that could one day be used in clinical settings for the early diagnosis of colorectal cancer.

Colorectal cancer is the third most prevalent cancer worldwide and is estimated to cause about 700,000 deaths every year. Metastasis due to late detection is one of the major causes of mortality from this disease; therefore, a sensitive and early indicator could be a critical tool for physicians and patients.

A paper describing the new detection technique by Caltech graduate student Ariel Furst (PhD ’15) and her adviser, Jacqueline K. Barton, the Arthur and Marian Hanisch Memorial Professor of Chemistry, are the paper’s authors.

‘Currently, the average biopsy size required for a colorectal biopsy is about 300 milligrams,’ says Furst. ‘With our experimental setup, we require only about 500 micrograms of tissue, which could be taken with a syringe biopsy versus a punch biopsy. So it would be much less invasive.’ One microgram is one thousandth of a milligram.

The researchers zeroed in on the activity of a protein called DNMT1 as a possible indicator of a cancerous transformation. DNMT1 is a methyltransferase, an enzyme responsible for DNA methylation—the addition of a methyl group to one of DNA’s bases. This essential and normal process is a genetic editing technique that primarily turns genes off but that has also recently been identified as an early indicator of cancer, especially the development of tumours, if the process goes awry.

When all is working well, DNMT1 maintains the normal methylation pattern set in the embryonic stages, copying that pattern from the parent DNA strand to the daughter strand. But sometimes DNMT1 goes haywire, and methylation goes into overdrive, causing what is called hypermethylation. Hypermethylation can lead to the repression of genes that typically do beneficial things, like suppress the growth of tumours or express proteins that repair damaged DNA, and that, in turn, can lead to cancer.

Building on previous work in Barton’s group, Furst and Barton devised an electrochemical platform to measure the activity of DNMT1 in crude tissue samples—those that contain all of the material from a tissue, not just DNA or RNA, for example. Fundamentally, the design of this platform is based on the concept of DNA-mediated charge transport—the idea that DNA can behave like a wire, allowing electrons to flow through it and that the conductivity of that DNA wire is extremely sensitive to mistakes in the DNA itself.

In the present study, Furst and Barton started with two arrays of gold electrodes—one atop the other—embedded in Teflon blocks and separated by a thin spacer that formed a well for solution. They attached strands of DNA to the lower electrodes, then added the broken-down contents of a tissue sample to the solution well. After allowing time for any DNMT1 in the tissue sample to methylate the DNA, they added a restriction enzyme that severed the DNA if no methylation had occurred—i.e., if DNMT1 was inactive. When they applied a current to the lower electrodes, the samples with DNMT1 activity passed the current clear through to the upper electrodes, where the activity could be measured.

‘No methylation means cutting, which means the signal turns off,’ explains Furst. ‘If the DNMT1 is active, the signal remains on. So we call this a signal-on assay for methylation activity. But beyond on or off, it also allows us to measure the amount of activity.”

Using the new setup, the researchers measured DNMT1 activity in 10 pairs of human tissue samples, each composed of a colorectal tumour sample and an adjacent healthy tissue from the same patient. When they compared the samples within each pair, they consistently found significantly higher DNMT1 activity, hypermethylation, in the tumorous tissue. Notably, they found little correlation between the amount of DNMT1 in the samples and the presence of cancer—the correlation was with activity.

‘The assay provides a reliable and sensitive measure of hypermethylation,’ says Barton, also the chair of the Division of Chemistry and Chemical Engineering.  ‘It looks like hypermethylation is good indicator of tumourigenesis, so this technique could provide a useful route to early detection of cancer when hypermethylation is involved.’ Caltech