Immune outposts inside tumors predict post-surgery outcomes

The immune system establishes “forward operating bases”, or lymph node-like structures, inside the tumors of some patients with kidney and other urologic Read more

Hedgehog pathway outside cilia (with CBD bonus)

The Hedgehog pathway has roles in both specifying what embryonic cells will become and in guiding growing neural Read more

Tracking how steroid hormone receptor proteins evolved

When thinking about the evolution of female and male, consider that the first steroid receptor proteins, which emerged about 550 million years ago, were responsive to estrogen. The ancestor of other steroid hormone receptors, responsive to hormones such as testosterone, progesterone and cortisol, emerged many millions of years later. Biochemist Eric Ortlund and colleagues have a new paper in Structure that reconstructs how interactions of steroid receptor proteins evolved over time. This is a complex Read more

John Petros

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.”

Posted on by Quinn Eastman in Cancer Leave a comment

A family of troublemakers known as XMRV

A long-delayed paper on the connection between chronic fatigue syndrome and XMRV (xenotropic murine leukemia virus-related virus) finally surfaced last week in PNAS. Astute readers may recall that XMRV has also been linked to prostate cancer.

Detecting XMRV in prostate tissue. A variety of assays (neutralizing antibodies, polymerase chain reaction or fluorescence in situ hybridization) may be used to look for XMRV

The twist from last week’s paper is that the NIH/FDA team, led by Harvey Alter, didn’t find viruses all with the same sequence in chronic fatigue patients. Instead, they found a cluster of closely related, but different, viruses. While confusing, these results may explain why tests for the presence of the virus that are based on viral DNA sequences may have generated varying (and conflicting) results. An alternative assay based on antibodies, such as the one urologist John Petros and colleagues at Emory developed, may be useful because it casts a wider net.

Pathologist Hinh Ly has been diving into the XMRV field, with a recent paper in Journal of Virology describing what “gateway” (receptor) molecule the virus uses to sneak into cells and what kinds of cells in the prostate it can infect.

In a collaboration with Ila Singh at the University of Utah, antiviral drug expert Raymond Schinazi has found that a number of drugs active against HIV also stop XMRV. This offers some hope that if doctors can detect members of the XMRV family, and figure out what they’re up to, they might be able to combat the troublemakers as well.

Posted on by Quinn Eastman in Uncategorized Leave a comment