Cancer gene plays key role in cystic fibrosis lung infections

PTEN is best known as a tumor suppressor, a type of protein that protects cells from growing uncontrollably and becoming cancerous. But according to a new study from Columbia University Medical Center (CUMC), PTEN has a second, previously unknown talent: working with another protein, CFTR, it also keeps lung tissue free and clear of potentially dangerous infections.

The findings, published in Immunity, explain why people with cystic  are particularly prone to respiratory infections—and suggest a new approach to treatment.

A quarter-century ago, researchers discovered that cystic fibrosis is caused by mutations in the CFTR gene, which makes an eponymous protein that transports chloride ions in and out of the cell. Without ion transport, mucus in the lung becomes thicker and stickier and traps bacteria—especially Pseudomonas—in the lung. The trapped bacteria exacerbate the body’s inflammatory response, leading to persistent, debilitating infections.

But newer research suggests CFTR mutations also encourage infections through a completely different manner.

“Recent findings suggested that  with CFTR mutations have a weaker response to bacteria, reducing their ability to clear infections and augmenting inflammation,” said lead author Sebastián A. Riquelme, PhD, a postdoctoral fellow at CUMC. “This was interesting because it pointed to a parallel deregulated immune mechanism that contributes to airway destruction, beyond CFTR’s effect on mucus.”

That’s where PTEN comes into play. “We had no idea that PTEN was involved in cystic fibrosis,” said study leader Alice Prince, MD, professor of pediatrics (in pharmacology). “We were studying mice that lack a form of PTEN and noticed that they had a severe inflammatory response to Pseudomonas and diminished clearance that looked a lot like what we see in patients with cystic fibrosis.”

Delving deeper, the CUMC team discovered that when PTEN is located on the surface of lung and immune cells, it helps clear Pseudomonas bacteria and keeps the inflammatory response in check. But PTEN can do this only when it’s attached to CFTR.

And in most cases of cystic fibrosis, little CFTR finds it way to the cell surface. As a result, the duo fail to connect, and Pseudomonas run wild.

As it happens, the latest generation of cystic fibrosis drugs push mutated CFTR to the cell surface, with the aim of improving chloride channel function and reducing a buildup of mucus. The new findings suggest that it might be beneficial to coax nonfunctional CFTR to the surface as well, since even abnormal CFTR can work with PTEN to fight infections, according to the researchers.

“Another idea is to find drugs that improve PTEN membrane anti-inflammatory activity directly,” said Dr. Riquelme. “There are several PTEN promotors under investigation as cancer treatments that might prove useful in cystic fibrosis.”

The study also raises the possibility that PTEN might have something to do with the increased risk of gastrointestinal cancer in . “With better clinical care, these patients are living much longer, and we’re seeing a rise in gastrointestinal cancers,” said Dr. Prince. “Some studies suggest that CFTR may be a tumor suppressor. Our work offers an alternative hypothesis, where CFTR mutations and lack of its partner, PTEN, might be driving this cancer in patients with .”

The paper is titled, “Cystic fibrosis transmembrane conductance regulator attaches tumor suppressor PTEN to the membrane and promotes anti Pseudomonas aeruginosa immunity.”

For journal article click here:

http://www.cell.com/immunity/fulltext/S1074-7613(17)30487-9

Why Aspiration Is a Silent, Hidden Danger for Cystic Fibrosis Patients

Dr. Gwen A. Huitt is an infectious disease doctor at National Jewish Health with a special interest in mycobacteria, bronchiectasis, and cystic fibrosis. Here, she talks to us about the hidden dangers of a major medical issue she feels doesn’t receive the attention it needs in the CF community — aspiration.

Q: What is aspiration? What is silent aspiration?

A: Aspiration is defined as any liquid, substance, or foreign body that gains access (below the vocal cords) to the airways. Many times when we have an overt aspiration, a cough is triggered. Think, “something went down the wrong pipe.” This may occur when folks drink fluids too quickly, toss their head back to take pills, etc. A small amount of liquid trickles down the windpipe, irritating it and causing a cough. Additionally, overt aspiration may occur in some folks with neurologic disorders that impair the ability to swallow appropriately (think stroke, Parkinson’s disease, etc.).

Silent aspiration may also occur in many neuromuscular disorders as well in “normal” hosts. This is where my patient population lives for the most part. There are two distinct situations that may occur. The first would be that when we take a drink, some small amounts of liquid “pools” in a recess around the vocal cords and then little amounts can trickle over the vocal cords down into the airway, but it does not trigger a cough or any sensation that something has just gained access to the airway. The second scenario is when we silently or overtly reflux up liquids from the stomach or esophagus and they reach high enough in the esophagus that they then trickle into the airway.

Q: What contributes most to aspiration?

A: For our patient population, we believe that overdistending the stomach with too much liquid, bending forward or lying too flat on your back, stomach, or on your right side contributes to most of our silent reflux episodes.

Q: What are the dangers of aspiration for a CF patient?

A: The dangers of aspiration for CF or non-CF patients are that you are sending not only germs such as pseudomonas or non-tuberculosis mycobacteria (NTM) into the airway that contribute to infection, but also that digestive enzymes and acids cause significant inflammation in the airways. This situation worsens inflammation and infection in the vulnerable airway.

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Q: What are telltale signs of aspiration damage in the lungs?

A: We know that aspiration can lead to bronchiectasis. Additionally, by looking at microbiology of the sputum, we may find many organisms that are predominantly only supposed to be found in the digestive tract. When we see certain organisms such as citrobacter or E. coli we know for sure that these organisms were translocated from the digestive tract to the airway via aspiration. In all likelihood, other organisms such as pseudomonas, NTM, and Klebsiella are also primarily acquired in the airway via this mechanism. Much more research needs to be done in this area though.

Q: What is something about aspiration you think people would be surprised to learn?

A: That so much of aspiration is silent and we currently don’t have any good test to assess for intermittent reflux that may lead to aspiration. Also, there is no medication that stops reflux (which then leads to aspiration). Medications such as PPI (i.e., Nexium) or H2 blocker (i.e., Zantac) medications suppress acid production, which certainly can help with heartburn or cough, but they do not stop the physical action of reflux.

Q: Should reflux medication be a last resort or is it enough of a danger that it should be used as soon as a patient begins exhibiting reflux/aspiration symptoms?

A: As I said earlier, we currently have no medication to stop the action of reflux. In many ways, taking these medications may actually make reflux worse because you don’t feel heartburn symptoms but most certainly are still refluxing. Also, part of what PPIs and H2 blockers do is lower acid. Part of the action of acid in digestive juices is to kill some proportion of germs that we swallow. If you are still refluxing (while taking PPIs) and you then aspirate some of this digestive “soup,” you are actually aspirating more germs per aliquot of gastric contents. [But] you should definitely take a medication to help with heartburn symptoms or if you have been seen by a [gastro doctor] and they have diagnosed ulcer disease or Barrett’s esophagus.

Q: Do you believe aspiration is taken as seriously in the CF health care setting as it should be?

A: No, I do not think that aspiration is taken seriously at all in the CF community. Nor is it taken as seriously in the non-CF world.

Original article found at: https://cysticfibrosisnewstoday.com/2017/12/14/aspiration-risks/?utm_source=Cystic+Fibrosis&utm_campaign=a772c5a83f-RSS_THURSDAY_EMAIL_CAMPAIGN&utm_medium=email&utm_term=0_b075749015-a772c5a83f-71418393

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New Inhaled Antibiotic To Treat Respiratory Infections

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Microbiologists uncover clues to clustering of lethal bacteria in CF patients’ lungs

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Scientists find new way to attack antibiotic-resistant lung infections

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New Drug Application Submitted for Treatment of P. aeruginosa

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French Biotech Receives an Award to Develop a Novel Cystic Fibrosis Antibiotic

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