Antibody production: an endurance sport

To understand recent research from immunologist Jerry Boss’s lab on antibody production, think about the distinction between sprinting and long-distance Read more

Less mucus, more neutrophils: alternative view of CF

A conventional view of cystic fibrosis (CF) and its effects on the lungs is that it’s all about mucus. Rabin Tirouvanziam has an alternative view, centered on Read more

epidemiology

Low-level cadmium toxicity and fatty liver disease

A recent study concluded that it’s more difficult for adults today to maintain the same weight as those a few decades ago, even with the same levels of food intake and exercise. On one level, this news is comforting to anyone in middle age, who may have been athletic as a teenager in the 1980s but isn’t anymore. It’s just harder nowadays!

However, the study authors also suggested, in an interview with The Atlantic’s Olga Khazan, an array of factors that might be contributing to the rise in obesity: exposure to chemicals such as pesticides and flame retardants, prescription drugs such as antidepressants, and altered microbiomes linked with antibiotic use in livestock.

The heavy metal cadmium may belong on that list of chemicals, not primarily as a booster of obesity, but instead in connection with the increase in prevalence in NAFLD (non-alcoholic fatty liver disease) over the last few decades.

Researchers led by Young-Mi Go and Dean Jones exposed mice to low levels of cadmium, so that the amounts of cadmium in their livers were comparable to those present in average middle age Americans, without tobacco or occupational exposure. They observed that cadmium-treated mice had more fat accumulation in the liver and elevated liver enzymes in their blood, compared with control mice with 10 times less cadmium.

Cadmium accumulates in the body over time. Tobacco smoke and the industrial workplace can be routes for cadmium exposure, but food is the major source for most non-smokers. Until the 1990s, most batteries were made with cadmium, and much cadmium production still goes into batteries. It is also found in paint and in corrosion-resistant steel. Read more

Posted on by Quinn Eastman in Uncategorized Leave a comment

Statins, prostate cancer and mitochondria

In honor of Fathers’ Day, we are examining a connection between two older-male-centric topics: statins and prostate cancer.

Statins are a very widely prescribed class of drugs used to lower cholesterol levels, for the purpose of preventing cardiovascular disease. In cell culture, they appear to kill prostate cancer cells, but the epidemiological evidence is murkier. Statin effects on prostate cancer incidence have been up in the air, but recent reports point to the possibility that starting statins may slow progression, after a man has been diagnosed with prostate cancer.

Winship Cancer Institute researchers have some new results that shed some light on this effect. John Petros, Rebecca Arnold and Qian Sun have found that mutations in mitochondrial DNA make prostate cancer cells resistant to cell death induced by simvastatin [Zocor, the most potent generic statin]. Sun recently presented the results at the American Urological Association meeting in Orlando.

In other forms of cancer such as breast and lung cancer, genomic profiling can determine what DNA mutations are driving cancer growth and what drugs are likely to be effective in fighting the cancer. The prostate cancer field has not reached the same point, partly because prostate cancers are not generally treated with chemotherapy until late in the game, Petros says. But potentially, information on mitochondrial mutations could guide decisions on whether to initiate statin (or another) therapy.

“This is part of our soapbox,” he says. “When we are looking at mutational effects on prostate cancer, let’s be sure to include the mitochondrial genome.”

Winship’s Carlos Moreno and his colleagues are working on the related question of biomarkers that predict prostate cancer progression, after prostatectomy surgery and potentially after just a biopsy.

Read more

Posted on by Quinn Eastman in Cancer Leave a comment

Highlights and links from PSA debate

On January 8, Emory University School of Medicine’s Department of Medicine Grand Rounds had an unusual format: a debate between Otis Brawley, MD and John Petros, MD on the topic of PSA testing.

Otis Brawley, MD

Prostate cancer is the second leading cause of cancer death for American men. PSA (prostate specific antigen) is a protein produced by the prostate gland and its levels can be measured by a simple blood test.  A higher number could indicate prostate cancer, but the test doesn’t differentiate between an aggressive, fast-growing cancer, and one that is so slow-growing it wouldn’t threaten a man’s life.

Brawley, professor of hematology and medical oncology and chief medical officer for the American Cancer Society, led off the debate arguing that studies show PSA testing to be unreliable and possibly leading to too many diagnoses and unnecessary treatment for prostate cancer. Petros, a professor of urology who treats prostate cancer patients, looked at other studies (more details below), which show the PSA test to be a tool that has helped save lives by detecting prostate cancer at earlier stages.

In May 2012, the U.S. Preventive Services Task Force issued a “grade D” rating for PSA screening, saying the practice offers more harms — in terms of complications from PSA-test-driven treatment such as incontinence and blood clots — than benefits. Brawley agreed with this Ray Ban outlet assessment and says he’s not convinced the PSA test saves lives, but he doesn’t rule out its use. He framed this issue this way:

Pretend you are offered the choice of taking a pill that will double the risk of prostate cancer diagnosis from 10 to 20 percent, but could decrease risk of prostate cancer death by one fifth: from 3 to 2.4 percent.  “Do you feel lucky?” Brawley quipped.

John Petros, MD

As a counterpoint, Petros cited National Cancer Institute epidemiology data indicating that the rate of metastatic prostate cancer has substantially decreased over the last few decades, since prostate cancers are now being diagnosed at an earlier stage. He also went over studies conducted in Sweden (Goteborg) and in Austria (Tyrol), which show significant reductions in prostate cancer-related mortality coming from PSA testing.

Five things Brawley and Petros agreed on:

  1. PSA testing should be performed in the context of a physician-patient relationship, with men making an informed decision about the value of the information they will receive and the associated risks.
  2. Vans in supermarket parking lots – more broadly, community- or employer-based screening  — are not the ideal setting for PSA testing.
  3. The PLCO study, a NCI-sponsored randomized clinical trial to examine the effects of screening on cancer-related mortality, was flawed. In particular, the “control” arm had a substantial rate of PSA testing.
  4. Brawley said: “Some cancers that are detected early do not pose a threat and do not need to be treated.” Similarly, Petros said: “Prostate cancer can be low risk if safely observed, but high risk forms are lethal. We need to focus on cancers that matter.”
  5. Biomarkers that are better than PSA alone are needed. Brawley said: “We need a 2013 definition of prostate cancer, informed by genomics, rather than going by what Virchow decided prostate cancer looks like under the microscope 160 years ago.”

Petros agreed with this last point and noted that more sophisticated tests than PSA already have been identified such as the prostate health index, which measures levels for three forms of PSA and may be more cancer-specific. Research being conducted at Emory by Carlos Moreno and colleagues also moves toward this goal. In 2011, his team published results in the American Journal of Pathology on a panel of biomarkers that can predict prostate cancer outcomes after prostatectomy. The Atlanta Business Chronicle recently had a story on a patent related to Moreno’s research.

Petros said a key question, and one he and Moreno are planning on testing, is whether the same biomarkers could be useful on prostate biopsy samples. This could help make treatment decisions regarding surgery vs radiation. Biopsy-based tests could be combined with data based on urine biomarkers, to get around the problem of tumor heterogeneity and imperfect sampling, Petros said.

For now, Petros said he believes in initiating a conversation about PSA screening with patients 50 and older, or younger if they have risk factors for the disease.   He said the decision to have routine PSA testing, follow-up tests and prostate cancer treatments, is a very individualized process.

“It comes down to, what do you tell the man standing in front of you?” he said. “You have to consider where they are in life and what their goals are, and that varies with every man.”

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