A safety concern with gene editing

BY JON HOLMLUND

Hat-tip to Dr. Joe Kelley for bring this to my attention…

As readers of this blog will recall, there is keen interest in exploiting recent discoveries in genetic engineering to “edit” disease-causing gene mutations and develop treatments for various diseases.  Initially, such treatments would likely use a patient’s own cells—removed from the body, edited to change the cells’ genes in a potentially therapeutic way, then return the altered cells to the patient’s bloodstream to find their way to the appropriate place and work to treat the disease.  How that would work could differ—make the cells do something they wouldn’t normally do, or make them do something better than they otherwise do (as in altering immune cells to treat cancer); or maybe make them work normally so that the normal function would replace the patient’s diseased function (as in altering blood cells for people with sickle cell anemia so that the altered cells make normal hemoglobin to replace the person’s diseased hemoglobin).

Or maybe we could even edit out a gene that causes disease (sickle cell anemia, Huntington’s disease) or increases the risk of disease (e.g., BRCA and cancer) so that future generations wouldn’t inherit it.  Or maybe we could edit genes to enhance certain health-promoting or other desirable qualities.

The recent scientific enthusiasm for gene editing is fueled by the discovery of the relatively slick and easy-to-use (if you’re a scientist, anyway) CRISPR-Cas9 system, which is a sort of immune system for bacteria but can be used to edit/alter genes in a lot of different kinds of cells.

It turns out that cells’ normal system to repair gene damage can and does thwart this, reducing the efficiency of the process.  The key component to this is something called p53, a critical protein that, if abnormal, may not do its repair job so well.  When that happens, the risk of cancer increases, often dramatically.  In cancer research, abnormal p53 is high on the list of culprits to look out for.

Two groups of scientists, one from the drug company Novartis and one from the Karolinska Institute in Sweden, have published on this.  P53’s thwarting of gene editing is particularly active in pluripotent stem cells, that are some, but not the only, candidate cells to be edited to create treatments.  These cells are also constituent cells of human embryos.  If the CRISPR-Cas9 process is used on these cells, p53 usually kills them off—unless it’s lacking or deficient, in which case it doesn’t, but also in which case it means that the altered cells could themselves become cancers, later on.

This is something that has to be monitored carefully in developing cells as medicines, so to speak, with genetic editing.  One does not want the patient to appear to be healed, only to develop a cancer, or a new cancer, later on.  One certainly would want to know the risk of that before editing an embryo—an unborn human, a future baby if placed in the right environment—to create a gene-edited human being.

Yet, as I’ve written here in the past, it appears that experimentation in heritable gene editing is pressing on.  I’ve argued, and continue to argue, that heritable human gene editing is a line that must not be crossed, that would place too much trust in the providence of the scientists/technologists who are the “actors” exerting power over fellow humans who become “subjects” in a deep sense of the term; that the risks to the subjects are undefinable; that it would enable perception of humans as “engineering projects”; that the gift of life would tend to be replaced by seeking to limit birth to “the people we want”; that the people acted upon are unable to provide consent or know what risks have been chosen for them by others, even before birth.  Rather than press ahead, we in the human race should exercise a “presumption to forbear.”

A counter argument is that, in limited cases where the genetic defect is limited and known, the disease is terrible, treatment alternatives are few or none, that the risks are worth it.  The recent papers seem to expose that line as a bit too facile.  How many embryos created (and destroyed) to develop the technique before “taking it live?”  Could we work things out in animals—monkeys, maybe?  How many generations to alter, create, and follow to be sure that a late risk—such as cancer—does not emerge?  Or maybe our animal rights sensibilities stop us from putting monkeys at such risk—maybe mice will do?

The new papers are dense science.  Frankly, I can grasp the topline story but have trouble digesting all the details.  More sophisticated readers will not be so impaired.  The news report, in the English of the general public, can be read here, the Novartis and Karolinska reports read (but not downloaded or printed) here and here, respectively.

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