p53 (4 page)

ARE WE CREATING FRANKENSTEIN SPECIES?

Attempting to answer such questions was extremely painstaking work with the tools then available – and the technical difficulties were compounded by an atmosphere of
high anxiety and ethical soul-searching among scientists at the time. Genetic engineering was in its infancy. It had begun in the 1960s with work on a class of viruses that
infect only bacteria and nothing else. Scientists had discovered that these viruses – known as ‘bacteriophages’ (often contracted simply to ‘phages’) – have a
habit of taking up genes from one bacterium they have infected and transferring them to their next bacterial victims; researchers had begun to harness this trait to investigate the activity of
genes from a wider variety of organisms.

The bacterium most commonly used as a vehicle for the scientists’ experiments was
Escherichia coli
(E. coli), because it readily takes up new genes, is tough and breeds fast, thus
offering them swift results. But as the technology developed and scientists became adept at splicing genes – chopping out bits of DNA from one genome and stitching them into another to
produce what is known as ‘recombinant DNA’ – some among them grew concerned.

They were no longer working only with bacteriophages, but with animal viruses also. And, as is the custom, there was a good deal of sharing of hybrids between labs worldwide, so the novel scraps
of life were being ever more widely distributed. But were these curious scientists – with their minds focused on cracking the secrets of the cell – wandering in where angels feared to
tread? While many were hugely excited by the potential of the new gene-splicing tools to deliver better ways of treating disease and improving food crops, others feared the potential for
catastrophe, wrote M J Peterson, in a case study for the Science, Technology and Society Initiative of the University of Massachusetts. ‘They believed that the probability of unintentionally
creating dangerous organisms – virulent “super” versions of disease-causing viruses or bacteria, strange and invasive life forms that push others out of habitats – because
the ways genes and gene sequences interact were not well understood, was too high to be ignored.’

Researchers were using a strain of E. coli known as K12 that had evolved to a stage where it could no longer live outside of cell cultures in test tubes and Petri dishes.
However, the fear was that, if it ever escaped the lab, K12 might combine with other strains of E. coli – a bacterium widespread in nature and living harmoniously for the most part with us
and other animals. Most concerned about the Pandora’s Box they might be opening were the microbiologists, who fretted that those without their specialist training in the life habits of
micro-organisms – which category included many researchers who had eagerly taken up the new tools – did not fully appreciate the risks. Often they would tip biological waste that
contained bacteria down the drain at the end of experiments, or draw up solutions by mouth with a pipette. As the critics pointed out tartly in a report on the possible hazards some time later,
‘A micro-organism is not simply a “warm body” to house a recombinant DNA molecule of interest.’ In 1974 a number of leading scientists stopped their work on recombinant DNA
pending a formal debate on the way forward for laboratories using this technology.

The following year the intense soul-searching among scientists, and the equally volatile debate that had begun in the world’s media, culminated in an international conference held at the
Asilomar Center, a magnificent old lodge built of warm local wood and stone overlooking the Pacific near Monterey, California. Writing for
Science
magazine in 2000 on the 25th anniversary
of the Asilomar Conference, journalist Marcia Barinaga called it ‘the Woodstock of molecular biology: a defining moment for a generation, an unforgettable experience, a milestone in the
history of science and society’. Looking back across the years, David Baltimore, who won the Nobel Prize for Medicine in 1975 for his work with viruses and was one of the organisers of the
conference, said, ‘Recombinant DNA was the most monumental power ever handed to us. The moment you heard you could do this, the imagination went wild.’

In fact, so exciting was it, and so potentially scary, that the attempt to reach consensus on the way forward among the disparate group of 133 scientists gathered at
Asilomar – debating under the watchful eyes and listening ears of 16 journalists and four lawyers – was extremely difficult. What eased the process was the decision to divide the types
of experiments using recombinant DNA into several categories – depending on whether they involved organisms or fragments of DNA known to cause disease or pose other dangers, or used materials
considered harmless – and making recommendations about how to proceed under different scenarios. These included taking measures to disarm living organisms used in experiments so that they
could not interbreed nor survive outside of tissue cultures; and adopting specific safety measures in the design of labs. It fell to national governments to turn the recommendations of the Asilomar
Conference into useable guidelines, and by 1976 scientists were able to resume their experiments with recombinant DNA, more or less reassured that they were not about to unleash Frankenstein
species upon the world.

HOW ONCOGENES TURN NASTY

A question burning in the minds of researchers ever since Bishop and Varmus’s discovery of the Src oncogene in chickens and other birds was: could these cellular
oncogenes cause cancer without first being captured by a virus? They found that indeed they could. The first evidence came from labs, including Bishop and Varmus’s own, which were
investigating the action of viruses that infect animals and cause cancer, but that don’t actually possess oncogenes. What the researchers found was that these viruses ‘hit’ the
DNA of the host cell in animals, corrupting its information and diverting it from its normal function as part of the growth and repair machinery to drive a cancer programme instead.

Further evidence came from Bob Weinberg’s lab at MIT which was looking not at viruses but at how certain chemicals can cause cells to become cancerous. Weinberg was
intrigued by Bishop and Varmus’s work and it led him to wonder if chemical carcinogens worked in the same way – by corrupting would-be oncogenes (so-called
‘proto-oncogenes’) and turning them nasty. At that time, even though the idea that mutant genes were what drove cancer had been around for some time, there was still very little hard
evidence, lots to test and many doubters. Weinberg himself was not yet fully convinced.

To investigate his theory Weinberg’s team took mouse cells which they treated with chemicals to make them turn cancerous. Then they extracted the pure DNA from these cells, and inserted it
into normal mouse cells in Petri dishes in the lab. Sure enough, the normal cells turned cancerous too – indicating that the agent that was causing the cells to turn cancerous was carried in
the DNA, in the genes, though they didn’t yet know which gene or genes was the culprit. This was the first evidence that would-be oncogenes did not need the action of viruses to turn nasty;
mutations caused by chemicals could have the same effect.

However, these exciting results were somewhat overshadowed by a scandal involving a scientist in Canada who had been doing research along the same lines. ‘This person was invited to give a
seminar at Harvard,’ Bob Weinberg told his audience at MIT. ‘I attended it and I was both extraordinarily impressed and extraordinarily depressed. The work that was shown was so vast
that it was far beyond anything my laboratory could ever do. It was
beautiful
data, and it indicated to me that this guy had already done more than my own laboratory could do for the next
10, 20 years – just a
vast
amount of data! And I went up to this guy and I said, “You know, we’re beginning to get results just like these.” And he said,
“
Really?
” and he was very excited.

‘Now I will tell you that usually when you have somebody coming up to you after a seminar and telling you that they’re getting exactly the same results as you
have recently been getting, you have mixed feelings,’ Weinberg continued. ‘On the one hand it’s nice to feel confirmed in your findings. But on the other hand you begin to feel
the hot breath of competition on the back of your neck!’ His audience chuckled. ‘But he had unalloyed pleasure at this – which I sort of registered and then tucked
away.’

The Canadian scientist had obviously impressed a lot of people, because not long after this he was invited to give talks at the MIT Cancer Centre, Cold Spring Harbor and other prestigious labs
in the US. ‘But just before he was to come,’ said Weinberg, warming to his story, ‘David Baltimore swung around from his office to mine and said, “You won’t believe
what happened . . . this guy’s boss in Toronto has just thrown him out of the lab!” I said, “
What
?” He said, “Yeah, they sent a paper to
Cell
to be
reviewed, and one of the reviewers calculated how many Petri dishes would need to have been used in order to carry out this work – he calculated that it was more Petri dishes than were used
in all of eastern Canada that year!”’ Weinberg pulled a face to express his incredulity, and his audience laughed.

‘And so it turned out – although the guy to this day never admitted any wrongdoing – that this idea he had was maybe right on the mark, but all the data he published came out
of his brain rather than his lab bench . . .’

The result of this fraudulent behaviour was that, for the next 10 years or so, labs like Weinberg’s had difficulty getting findings from similar experiments accepted by the cancer
community, which was wary of being duped again. But as evidence for oncogenes began to accumulate from many different labs, doubts about their central role began slowly to fade. The research
community became fixated on an ‘accelerator’ model of cancer – one in which the normal
mechanism of cell division is being actively reprogrammed by these
‘rogue’ genes, the oncogenes, to go into overdrive, thus causing the cells to proliferate wildly. This was the mindset at the time p53 was discovered in 1979.

***

The history of science is strewn with groundbreaking discoveries which are only subsequently recognised as such. No drama attaches to the moment itself, and life goes on as it
was before. Often, the circumstances are mundane – a scruffy laboratory with test tubes and microscope slides scattered among scientific papers, family pictures and a postcard from a
colleague on holiday pinned to the wall; a white jacket over the back of a swivel chair. The discovery of p53 in 1979 was no different. It occurred independently in labs in London, Paris, New
Jersey and New York at almost exactly the same time, though the two men most widely credited with finding the super-gene are David Lane and Arnie Levine, who published their research in the most
prestigious journals,
Nature
and
Cell
respectively.

Both were working in the still somewhat contentious field of oncogenes – Lane at the Imperial Cancer Research Fund (ICRF) in London and Levine at Princeton University,
New Jersey. After reading through the dry-as-dust accounts of their findings in the scientific literature, I set off to hear their stories from the men themselves. But first some
information about the experimental system they were working with, which has a colourful story of its own. They were studying a virus called SV40, which stands for simian vacuolating virus 40; it is
the workhorse of molecular biology because it provides a simple model for exploring how the machinery of cells – DNA, genes and proteins – works in complex organisms, including us.

As its name suggests, SV40 infects certain monkey species, though it does not usually cause them disease. The virus was discovered in 1960 by American microbiologist Maurice Hilleman, as a
contaminant of polio vaccines. The original Salk and Sabin vaccines were made using kidney cells of rhesus macaque monkeys, native to the jungles, forests and dry plains of Asia, as a medium for
growing polio viruses. The virus, which grew prolifically on the monkey cells, was harvested and treated so that it could no longer cause disease, but would induce an immune response that would
protect the vaccinated individual against subsequent infection with harmful polio virus.

Hilleman, who worked for the Merck Pharmaceutical Company and was famed for his fiery temper and for keeping in his office a row of ‘shrunken heads’ (models made by one of his
children to represent the employees he had fired for not coming up to his exacting standards), was a pioneer of vaccine research. In his lifetime he developed more than 40 vaccines, including those
for mumps and measles. Hilleman had warned of the possibility that monkey cells used to grow the polio virus might contain other viruses and, five years after the first mass vaccination campaigns
against the paralysing disease began, he and his colleague Benjamin Sweet duly showed that they did.

By the time the rogue virus harvested alongside the polio virus was detected, millions of people worldwide had
received their shots. But no one seemed unduly concerned
until the following year, 1961, when reports appeared that injection of SV40 into newborn hamsters caused tumours to develop. The US Government ordered all new batches of polio vaccine to be
screened to eliminate SV40. Existing stocks were not recalled, however, and by the time these were exhausted in 1963, 10–30 million Americans and countless people in other parts of the world
had been injected with contaminated polio vaccines (the oral vaccine was not a threat). But despite exhaustive investigation in the US and Europe over more than half a century – and the
detection of traces of SV40 in some rare tumours of the brain, bone and lung – public health watchdogs such as the Centers for Disease Control and Prevention and the National Cancer Institute
in the US assert that there is no evidence of increased risk of cancer in people who might have received contaminated polio vaccine. Nor, they say, is there any evidence that the monkey virus found
in the rare tumours was the cause of the cancers – though suspicion that it was will probably never completely go away.