Cancer cells may 'prepare' earlier than believed

The spread of cancer to new sites in the body--the process ultimately responsible for most cancer deaths--may happen earlier in the disease process than was previously thought, new research on mice suggests.

Scientists said the finding suggests an explanation for why some breast cancers, for example, me­tastasize, or spread, long after the initial tumor has been treated.

Be cause cancer metastasis involves many steps--the cells must be equipped to survive a trip in the blood stream and start malignant growth in a new area of the body--researchers have traditionally considered it to be a late event in cancer progression. According to this view, metastasis occurs af­ter primary tumor cells have racked up a series of genetic alterations that switch on cancer genes.

The new results, scientists said, suggest metastatic disease might instead arise from normal cells that spread early in the disease. These remain dormant at the new organ site until cancer genes are switched on.

In the study, Katrina Podsypanina at Memorial Sloan-Kettering Cancer Center in New York and col­leagues injected mice with mammary cells manipulated in a way that allowed re searchers to turn on certain cancer genes, or “oncogenes,” at various times after injection.

The researchers found that the normal mammary cells could travel in the blood stream to the lungs and survive there up to four months with out activating any oncogenes. The cells didn’t begin grow­ing aggressively until the oncogenes had been turned on.

Examining each step of the process by which cancer me tasta sizes, including those involving nor­mal cells, might allow scientists to identify new strategies for destroying the cells responsible for the spread, accord ing to Podsypanina and colleagues. The findings appear in the Aug. 29 issue of the research journal Science.

World Science