Neanderthaler met hersentumor

[Cees Binkhorst]

REPLY TO: D66 at nic.surfnet.nl

Wellicht dat die vondst in de Noordzee nog kan helpen bij het onderzoek
van die apoptose als tumoroorzaak?

Groet / Cees

http://www.nd.nl/artikelen/2009/juni/15/eerste-nederlandse-neanderthaler-ontdekt
[deel weggelaten]
Wetenschappers hebben de Neanderthaler ‘Krijn’ genoemd. ,,Deze Zeeuwse
jongeman is gestorven op de linkeroever van de toenmalige Rijn’’, vertelde
een wetenschapper. De man had een goedaardige tumor, ontdekten
wetenschappers van het Max Planck Instituut in Duitsland. Hij was dus
ziek, maar deze ziekte was niet zijn doodsoorzaak. De man moet volgens de
wetenschappers ,,een verschrikkelijke vleeseter’’ geweest zijn.
[deel weggelaten]

http://www.usnews.com/articles/science/medical-science/2009/06/10/is-cancer-the-price-for-our-big-brains.html
Human's large brain size could be one reason why we are more prone than
chimps to cancer
Our large brains may make us cognitively superior to chimps, but,
according to a new hypothesis, we could be paying a price for our sizable
cerebrum: a higher rate of cancer.
 Chimpanzees are thought to be the closest evolutionary relative to
humans, and we share around 98 percent of our genes with these primates.
But for years, scientists have observed that chimps have a surprisingly
low cancer rate compared to humans.

To find out why this might be, John McDonald, a researcher at Georgia
Tech, turned to the human and chimp genome.

Many past studies have looked at differences in how genes are expressed
among humans and chimps. McDonald and his colleagues re-examined the data
of a previous gene expression study and added some previously excluded
information.

They looked for differences in gene expression in several tissues,
including the brain, liver, testes and kidneys.

Self-destroying cells

McDonald wanted to test a hypothesis that the difference in cancer rates
between the species could be due to differences in the way their cells
self-destroy themselves — an important biological process known as
programmed cell death or apoptosis.

The researchers saw that some of the genes for apoptosis were expressed
differently in humans than in chimps, and their data suggests that human
cells are not as efficient at carrying out programmed cell death as chimp
cells, at least in the brain and other studied tissues.

What does apoptosis have to do with cancer?

Reduced amounts of apoptosis have been associated with an increased risk
of cancer. Also, several genes involved in apoptosis are thought to
"malfunction" in cancer cells. This makes sense: cancer cells divide
uncontrollably and somehow seem to override the signal to self-destruct.

Paying the price

And what does that have to do with a large brain? During human evolution,
it is thought that people were naturally selected for larger brains and
increased cognition. There is also another hypothesis that to get these
larger brains, we needed to have a high rate of neuron synthesis.

The researchers are tying these two hypotheses together. They think that
reduced apoptosis may have helped people acquire their large brains. But
it may also have made us more prone to cancer.

"It's kind of hard to explain why we could have evolved to have a less
efficient apoptotic system," says McDonald. "So the hypothesis we came up
with was that maybe selection to increase brain size was what put the
selective pressure on the system to reduce apoptosis." And even though
less apoptosis may have meant more cancer, there would not have been
selective evolutionary pressure against it since most cancers don't appear
until after reproductive age, McDonald adds.

The hypothesis is slightly different from many previous ideas about how we
evolved large brains. "We have larger brains than chimps, [and] most
people have focused on the fact that we may be producing neurons at a
higher rate," McDonald told LiveScience. "But I think the other side of
the story is that we could also not be destroying them."

The research was also supported by recent studies that observed that
people with certain cognitive diseases — diseases that are associated with
an increase in neuron apoptosis — have lower cancer rates.
[deel weggelaten]

**********
Dit bericht is verzonden via de informele D66 discussielijst (D66 at nic.surfnet.nl).
Aanmelden: stuur een email naar LISTSERV at nic.surfnet.nl met in het tekstveld alleen: SUBSCRIBE D66 uwvoornaam uwachternaam
Afmelden: stuur een email naar LISTSERV at nic.surfnet.nl met in het tekstveld alleen: SIGNOFF D66
Het on-line archief is te vinden op: http://listserv.surfnet.nl/archives/d66.html
**********