Cancer caused primarily by bad luck

Cancer causes: Bad luck to blame –
not lifestyle or genes
Findings suggest that it may be difficult
for individuals to significantly reduce
their risk of developing cancer
By OLIVER WRIGH..... 2015
Most cases of cancer are the result of
sheer bad luck – not unhealthy lifestyles,
diet or even inherited genes, new
research suggests today.
Scientists from Johns Hopkins University
found that random mutations that occur
in DNA when cells divide are responsible
for two-thirds of adult cancers.
The remaining third are linked to
environmental factors or defective
inherited genes, according to the
research published in the medical
journal Science.
The findings suggest that it may be
difficult for individuals to significantly
reduce their risk of developing cancer by
altering their lifestyle – but the scientists
warn that alcohol, smoking and a poor
diet can add to the “bad luck factor”
involved in cancer.
Stopping smoking would have prevented
314,000 cases of cancer in the past five
years
The researchers analysed published data
on the number of divisions of self-
renewing stem cells that occur in an
average lifetime in 31 different types of
tissue. These results were then compared
with the lifetime incidence of cancer in
the same tissues.
Researchers found a strong correlation
between a particular tissue’s stem cell
division rate and its likelihood of
developing cancer.
The more often cells divided, the more
likely that letters of their genetic code
become jumbled, leading to an increased
cancer risk.
Overall, the study found that random
mutations due to stem cell division could
explain around 65 per cent of cancer
incidence.
Professor Bert Vogelstein, from Johns
Hopkins University School of Medicine in
Baltimore, said: “All cancers are caused
by a combination of bad luck, the
environment and heredity, and we’ve
created a model that may help quantify
how much of these three factors
contribute to cancer development.
“This study shows that you can add to
your risk of getting cancers by smoking
or other poor lifestyle factors. However,
many forms of cancer are due largely to
the bad luck of acquiring a mutation in a
cancer driver gene regardless of lifestyle
and heredity factors. The best way to
eradicate these cancers will be through
early detection, when they are still
curable by surgery.”
Micrographic view of lung cancer cells
Scientists have known for more than a
century some tissue types give rise to
cancer millions of times more than
others, but why is not clear.
The research suggests that the answer
chiefly lies in the number of times a
tissue’s stem cells divide. “Bad luck”
mutations that occur when one chemical
letter in DNA is wrongly swapped for
another during cell replication largely
explained 22 of the 31 cancer types
studied.
The remaining nine had incidence rates
higher than predicted by bad luck, due
to the influence of environmental or
inherited factors.
“We found the types of cancer that had
higher risk than predicted by the
number of stem cell divisions were
precisely the ones you’d expect,
including lung cancer, which is linked to
smoking; skin cancer, linked to sun
exposure; and forms of cancers
associated with hereditary syndromes,”
Professor Vogelstein said.
People who live a long life despite
exposure to cancer-causing agents are
not blessed with “good genes” but good
luck, the professor said