Cancer Spreads Through Body Long Before Tumor Develops

Tuesday, February 03, 2009 by: David Gutierrez, staff writer

(NaturalNews) Seemingly healthy cells may spread to distant parts of the body long before any cancerous tumors are visible, researchers have discovered. This suggests that the virulence of a specific case of cancer might actually be determined early in the disease, perhaps even before diagnosis.

At issue is a phenomenon called metastasis, by which cancer cells spread from one organ to a non-adjacent organ. Cancers that have metastasized are particularly lethal and hard to treat; the majority of lethal breast cancers, for example, are metastatic.

"These findings indicate that properties inherent in normal cells are sufficient for negotiating a significant portion of the metastatic cascade," lead researcher Dr Katrina Podsypanina said. "Our data seems to point toward the inherent decision that is made when the tumor is formed whether it is highly malignant or not."

The findings might explain the mystery of why some cancers have such high rates of metastasis and recurrence. Breast cancer is one such disease, with roughly 20 percent of women who are free of cancer five years after diagnosis suffering a recurrence some time in the following 10 years.

Previously, researchers had thought that metastasis could only occur in the late stages of cancer, when highly developed cancer cells break off from tumors and enter the circulatory or lymphatic systems. They had thought that prior to this point, cells would be unable to survive the journey and establish themselves in other organs.

In the current study, published in the journal Science, Podsypanina and colleagues at the Memorial Sloan-Kettering Center in New York injected mice with mammary (breast) cells that had been genetically modified to contain an "oncogene" that could be switched on to turn them cancerous. These cells were observed to travel through the blood and establish colonies in the lungs, where they were able to survive for up to 16 weeks.

They did not begin to form tumors, however, until their oncogenes were switched on. At that point, they rapidly developed into aggressive tumors without passing through the traditional early stage.

For comparison, the researchers also injected mice with non-modified mammary cells. In these mice, too, the breast cells established colonies in the lungs that were observed to grow and proliferate. These clusters of mammary cells never became malignant, however. When they were removed and implanted into other mice, they developed into normal, apparently healthy breast tissue.

"The finding that metastatic disease can arise from untransformed mammary cells in the circulation refines our conception of cancer progression," the researchers said.

The researchers and other cancer experts cautioned that more research is needed before it can be known for sure whether healthy cells are really involved in the spread of cancer. For one thing, it is not clear why or how healthy cells would get to other parts of the body in the first place, or how they would be activated once there.

"This does suggest that cells can sit for a long time, and then be activated," said Claudine Isaacs of Georgetown University. "But these cells were injected into the circulation. Normal breast cells are not supposed to be in the circulation."

In addition, the same effect might not occur in humans as in mice.

Yet if the implications of the study are correct, it might be possible to develop new cancer treatments that prevent the disease from spreading and becoming more lethal.

"If follow-up research suggested that dissemination of normal breast cells can account for metastatic relapse in breast cancer patients (a hypothetical situation, at present), we would argue that treatment strategies should aim to compromise viability and/or proliferation of normal breast cells, and not just breast tumor cells," they said.

"It's definitely conceptually very profound," Podsypanina said.

Sources for this story include: news.bbc.co.uk; info.cancerresearchuk.org; www.washingtonpost.com.