The PSA Test for Prostate Cancer

For over 20 years some health professionals have been recommending that men over 50, and men as young as 45 if they belong to a high-risk group, be screened for prostate cancer by means of a PSA test (see Human Biology 5th ed., table 18.4). The PSA test measures the level of prostate-specific antigen, a protein from prostate cells. An elevated serum PSA indicates that prostate cancer might be present, in which case the next step is a biopsy to determine for sure.

When the PSA test was first introduced in 1987, scientists thought it might lead to as much as a 50% reduction in prostate cancer deaths. But now it seems that it may not save lives after all. In a study of 77,000 U.S. men, the 10-year death rate from prostate cancer was the same in a group who had an annual PSA test for six years plus a digital rectal examination for four years, compared to a control group who were never tested over the same time period. The study may need to be continued out for another decade or so to determine whether the PSA test has any usefulness over the longer term, however.

How can a test that accurately detects prostate tumors not save lives? Apparently the answer is that most prostate cancers are so slow-growing that older men are likely to die of something else first, even if they do have a diagnosis of prostate cancer. For older men, skipping the PSA test altogether may someday be safe option.

By the way, a digital rectal examination is not some sort of digital readout. It's a physician’s gloved digit, or finger.

If Not Bird Flu, Then.....What?

In Human Biology: Concepts and Current Issues we discuss the possibility that a human pandemic might be caused by the bird flu virus, H5N1, if the virus evolves to become easily transmissible between humans. But so far it hasn’t happened. Where will the next great human pandemic come from, if not from the bird flu virus? No one knows for sure, but the smart money is on pathogens living in animal species closely related to humans, such as non-human primates. In fact, that’s precisely how HIV developed – an evolving virus in monkeys jumped to chimpanzees and then to humans.

Knowing this, how might we prevent the next pandemic, or at least have some warning that it was coming? One intriguing possibility would be to keep a close eye on diseases that develop in humans who are in close contact with wild animals. To learn more, read “Preventing the Next Pandemic”, by Nathan Wolfe (Scientific American, April, 2009, pp. 76-81), and then check out the website of the Global Viral Forecasting Initiative. In fact you can download a .pdf file of the Scientific American article directly from the the GVFI website.

Obama Lifts Stem Cell Ban

Last week President Obama signed an executive order lifting the restrictions on stem cell research laid down by President Bush in 2001 (See the Current Issue in Human Biology 5th. ed., pp. 72-73). Most political analysts expect Congress to enact new legislation soon that will permit federal research dollars to again begin to flow for promising stem cell research projects.

President Obama’s executive order will permit federally funded researchers to use the hundreds of stem cell lines in existence today, as well as new stem cell lines created by private funding in the future. But there is still a prohibition in place, called the Dickey-Wicker Amendment of 1996, which prohibits federal funding for research “in which human embryos are created, destroyed, discarded, or knowingly subjected to risk of injury or death”. So while federally funded researchers will be able to use stem cell lines created by private funds (because they themselves did not destroy any embryos), they will still be prohibited from creating their own new cell lines from human embryos.

How long can the Dickey-Wicker Amendment can stand up in this new climate of stem cell research permissiveness? It's anybody’s guess. The debate continues…

A Way to Cure HIV Infection?

Modern HIV treatment drugs suppress an active HIV infection well enough that an HIV-infected person can live a relatively normal life. But they don’t cure an HIV infection because some viruses lie dormant inside living cells, out of reach of suppressive drug therapy. For that reason, high-cost suppressive therapy needs to be continued throughout the life of the patient, just so the drug is present whenever viruses do come out of hiding. What is needed is a way to get rid of the latent viruses lying dormant inside cells, once and for all.

A new approach is anti-latent therapy – therapy designed to prevent dormant viruses from staying dormant and hidden. The idea is to force any remaining dormant viruses to become active again so that they can be targeted and killed by suppressive therapy. A combination of anti-latent therapy and suppressive therapy just might wipe out an HIV infection completely. At least, that’s the idea.

Designer Babies? - Not Yet!

On Tuesday, a fertility doctor with clinics in New York and Los Angeles said that within six months he would offer couples the chance to choose some of their baby’s physical traits. Dr. Jeff Steinberg said that his company, Fertility Institutes, would use in vitro fertilization (IVF) techniques combined with pre-implantation genetic diagnosis (PGD) to help couples select from among their IVF embryos for the one with the best chance of having their preferred hair and eye color and even skin tone. Fertility experts scoffed that it could be done with any reliability. And when right-to-life advocates objected strenuously and his clinic received hundreds of calls, Dr. Steinberg backed down – at least for now. According to an article in the Daily News later the same day, he said he’ll stick to helping couples concerned about known genetic disorders.

The unresolved issue of whether would-be parents should be allowed to create designer babies is a train wreck waiting to happen. New York, for example, does not have laws against using PGD strictly for cosmetic purposes, so clinics such as Dr. Steinberg’s are free to promise what they will. Nevertheless, it’s a slippery ethical slope they’re on. The issue is discussed in Human Biology 5th ed., pp. 396-397.

Walking Like a Modern Human

Well-documented fossilized 3.8 million-year-old footprints show that our early ancestors walked with a decidedly ape-like primitive gait, with bent knees, short steps, and a predominant point of impact on the heels. It may have taken several million more years of evolution before changes in our ancestors’ physical structure allowed them to walk with the long stride of modern humans. Recent analysis of 1.5 million-year-old footprints in Kenya indicates that the footprint-makers (most likely Homo erectus) had a long stride and the ability to push off with the big toe, as we do. The footprints also show that by 1.5 million years ago, foot anatomy was very much like ours.