Cancer spread 'happens earlier' (BBC 29 August 2008)

Cancer spread 'happens earlier'
Breast cancer cells
It was thought cancer cells stayed put until advanced stages of the
disease

Apparently "normal" cells may carry cancer to new sites long before a
tumour develops, lying dormant until key genes are activated, experts
say.

US researchers say their findings, published in Science, could explain
why some breast cancers lead to new tumours long after the disease is
treated.

Secondary, or metastatic, cancers are responsible for the majority of
deaths from the disease.

UK experts said it was essential to know more about how the cancer
spreads.


These are important but early results
Liz Baker, Cancer Research UK

It has traditionally been thought that the spread of cancer to another
site in the body was a late event that only occurred when a disease
was advanced.

Cancer cells had been thought to have stayed in place until they had
undergone a series of genetic alterations making them more aggressive.

They have to be able to survive the journey through the bloodstream
and be able to initiate malignant growth in their new environment in
the new site.

Lying in wait

In this latest research, by a team at the Memorial Sloan-Kettering
Center in New York, mice were injected with normal breast tissue cells
which had been manipulated so the scientists could "switch on" cancer
genes (oncogenes).

It was found that the cells were capable of travelling in the
bloodstream to the lungs and surviving there for up to 16 weeks
without expressing any oncogenes.

The cells did not begin growing aggressively in the lungs until the
oncogenes had been turned on.

The researchers say that examining each step of the process by which
cancer metastasizes, including those involving normal cells, it might
be possible to work out ways to destroy the cells responsible for the
disease's spread through the body.

Writing in Science the researchers, led by Dr Katrina Podsypanina,
said: "The finding that metastatic disease can arise from
untransformed mammary cells in the circulation refines our conception
of cancer progression."

Liz Baker, senior science information officer for Cancer Research UK,
said: "Learning more about the spread of cancer - or metastasis - is
essential because it's harder to treat the disease once it has spread.

"These are important but early results in mice - it will be
interesting to see whether this can one day help the outcome of people
affected by cancer."