Читать книгу Masterminds: Genius, DNA, and the Quest to Rewrite Life - David Duncan Ewing - Страница 10

A researcher in obstetrics and gynecology at the National University of Singapore, Ariff Bongso, first grew human stem cells in 1994. In 1998, the University of Wisconsin’s James Thompson isolated human stem cells for the first time. Yet scientists have known about stem cells in mice since the seventies. The original discovery in mice occurred when researchers were studying certain cancer cells, which they now know have many of the properties of a mouse’s embryonic stem cell that can grow into different types of cells. Melton says this promising line of research stopped, however, in the early eighties before a connection was made between what was going on in mice and humans.

“The field didn’t move forward at the time because of an historical accident,” he says, which was the discovery of recombinant DNA technology. This became all the rage and sidelined other research as scientists sought to learn about cell differentiation not through working with stem cells, but by recombining genes from different species, and also by removing, or “knocking out” genes in mice to see what impact all of this would have on a cell or organism. “It’s only now that people are going back to mouse [embryonic stem] ES cells, let alone human ES cells. And while they’re extremely useful for studying gene function in an animal, they also have their own inherent interest. Could you make body parts, tissues, ex vivo? That’s the field I’m very excited about, but we’re way behind.”

Since Bongso’s discovery in 1994, stem cells have ignited two firestorms. One is a creative fire, a breathtaking moment for Melton and other scientists, for whom a new world has been opened up for exploration that they believe will save countless Sams and Emmas. The other is political and ethical, the scorching debate that pits scientific optimists against skeptics who believe that this fledgling science may open up a Pandora’s box that could have unforeseen and catastrophic consequences.

For those who believe that life begins at conception, an experiment using embryonic stem cells is indeed a homicide. “We should not intentionally create life in order to destroy it, even for good purposes of scientific research,” says William Hurlbut, a Stanford physician and conservative bioethicist who was appointed by George W. Bush to sit on the President’s Bioethics Commission. He is not opposed to doing stem cell research, he says, just to acquiring the stem cells by destroying an embryo. “If we say that a human life in process should have a certain inviolable moral status,” he says, “then we protect ourselves against the dangers of both crossing a fundamental moral boundary and what other people call the slippery slope.” Hurlbut is closely connected to Catholic leaders and opposes abortion but says his convictions about the status of an embryo are based less on his religious convictions than on a fundamental belief that a line needs to be drawn to protect what it means to be a human.

Opposition does not arise from just the right-to-life camp. There are liberal secularists, too, who bring up Brave New World scenarios of baby farms where clones of you or me would be grown exclusively to provide spare parts—and farmed like a turnip or a chicken is now. Another fear is that stem cells will lead to designer babies engineered by using stem cells not merely to replace damaged cells in Melton’s children, but to add new cells designed to be supermemory cells, or super-muscle cells. The technoskeptic Bill McKibben frets that biotech companies and commercial interests are poised to patent stem cell discoveries, which may lead to biotech barons’ pushing stem cells and other bioenhancements on the public out of greed. “And they’ll be hard to police,” writes McKibben in his 2003 book Enough, “not only because they’ll contribute to political campaigns, but also because their work, day in and day out, won’t be dramatic enough to attract notice.” Many others who are not religious zealots or anticorporate warriors feel uneasy about the notion of creating a human embryo solely with the intention of harvesting its cells to benefit a full-grown human, though this unease may dissipate if cures are discovered.

A greater source of discomfort surrounds the use of cloning to create embryonic stem cells. Scientists believe that stem cells made from cloned DNA will work best to reconstruct spinal cords and liver cells in a specific person because the cloned cells are an identical genetic match and won’t be rejected by the body’s immune system. Rejection is currently a major drawback in transplanting hearts, kidneys, and other organs. Cloning also allows researchers to study how diseased cells develop in specific patients. To clone stem cells from, say, Sam Melton, a researcher would take Sam’s own DNA and implant it into a denucleated egg, which would hopefully grow into an embryo that contains Sam-specific stem cells capable of developing into pancreatic cells. These stem cells would be harvested and the embryo destroyed, although the embryo up until then could be placed inside a womb and theoretically taken to term, creating a full-scale clone of Sam.

Melton and other stem cell scientists insist that they have no intention of creating cloned human beings. But mistrust and fear of scientists and their motives lingers in a society that wants treatments and gizmos from science but fears its potential dangers and excesses. “I’ve had to face up to the fact that most of our society thinks of scientists as people who are likely to do something bad,” sighs Melton. “Either bad to make money for themselves, or to cause trouble in the Frankensteinian sense. And the fact is, scientists that I know are trying to do good for people.”

Rogue scientists and quacks have fed into the fear. In early 2003, a company called Clonaid claimed to have created a cloned human on behalf of a New Age sect called the Raelians, founded by a former race car journalist named Claude Vorilhon, a.k.a. Rael, who says that humans were cloned and brought to Earth long ago by aliens. When the baby failed to show up, and Clonaid refused to allow independent verification, their announcement was declared a hoax. More legitimate is the Italian embryologist Severino Antinori, who has claimed to be working to create a human clone in an undisclosed location. In February 2004, the cloning issue heated up when a South Korean research team led by Hwang Woo Suk of Seoul National University cloned thirty embryos of about one hundred cells each—by far the largest number grown to date. They then successfully extracted embryonic stem cells from one of the embryos. Stem cell advocates were ecstatic, while their critics pointed out that the Koreans could have planted their cloned embryos into a womb and attempted to grow a Xeroxed person. Also in 2004, the British government for the first time issued a permit under the Human Fertilization Authority for a team of scientists at the Center for Life in Newcastle to clone embryos to create stem cells.

Geneticists insist that reproductive cloning does not work well for animals, and that clones are prone to illness and a short life span. The clones also don’t look like replicates of the parent. They are genetically identical, but environmental factors in the womb cause the clones to develop different features. For instance, a company in California recently cloned a calico cat that was born with a different calico pattern from its genetic “parent.” “So little Bobby’s clone won’t look like the original Bobby,” the pioneering molecular biologist Sydney Brenner told me. “Besides,” he said in his dry South African – British accent, “I can find much more pleasant ways of reproducing children that do not involve cloning.” Yet someone will one day most likely clone a human being, if no one has already. The scientists say that the technology is difficult, possibly impossible, though they used to say cloning a sheep would be impossible—and then came Dolly in 1997. “That will be a disaster,” says Melton, “first for the child, but also for science, if the child ends up getting sick and dying, or becomes an object of revulsion and ridicule.”

The controversy over embryonic stem cells being a force of good or evil is as old as fire. The Promethean myth is not just about a sympathetic god who gives mortals fire. A cautionary tale about the dangers of delving too much into the mysteries of the gods, it also underscores the dual nature of scientific discovery—that fire is a potent tool for improving life but can also be a force of destruction. Cro-Magnon scientists undoubtedly pointed to fire and realized the possibilities: Charbroiled mammoth steak! Torchlight to paint bison on cave walls! Cro-Magnon skeptics agreed that mammoth kabobs were better barbequed than raw, but what if the flames leapt up in a gust of wind and razed the village, burning people alive? For aeons, the profire and antifire forces have seesawed back and forth as the prevailing viewpoint when new technologies and discoveries appeared. Fire is still rightly feared in certain forms, and we have strict laws about arsonists and others who abuse it. Yet humans long ago decided the basics about what’s useful and dangerous about fire. We have imposed sensible regulations on its use, striking a balance that we can only hope will one day prevail for the work of Doug Melton and his fellow fire-bringers.