Dense tissue promotes aggressive breast cancers

August 23rd, 2008 - 12:25 pm ICT by IANS  

Washington, Aug 23 (IANS) Women with increased breast density that shows up on mammograms have an increased risk of developing breast cancers with invasive characteristics, says a new study on the subject. Breast cancer cells grown in dense, rigid surroundings step up their invasive activities, according to the study. The findings suggest a cellular mechanism behind the link between breast tissue density and tumour aggressiveness.

This connection between breast density and cancer aggressiveness has begged the question of which comes first. Is the tissue denser because the tumour is more aggressive, or is the tumour more aggressive because the tissue is denser?

“Our study shows that if you have a dense, rigid matrix, the cells will be more aggressive and invasive; it’s a direct effect,” said Alissa Weaver, assistant professor at Vanderbilt Integrative Cancer Biology Centre and co-author of the study.

Weaver and colleagues were interested in invadopodia - the finger-like protrusions that a cancer cell uses to drill holes in the extracellular matrix. These structures are believed to be important for cancer invasion.

“If you have enough invadopodia, over time they’ll make large holes that cells can move through to invade and metastasize,” Weaver said.

Despite the intimate connection between invadopodia and the matrix, very little was known about what role the matrix might play in regulating invadopodia function.

Weaver and colleagues started probing this question as part of computational math modeling project through the Vanderbilt Centre.

They were surprised to find that breast cancer cells cultured on a denser - and thus, more rigid - matrix had a greater number of active invadopodia than breast cancer cells cultured on a less dense matrix.

“We thought that more ’stuff’ for the cells to get through was going to make it harder, so we expected to see less matrix degradation, but instead we found this interesting effect where cells actually sense the rigidity and degrade more,” Weaver said.

Weaver said that it’s exciting to find a cellular mechanism that could explain why denser breast tissue is correlated with more aggressive tumours and a poorer prognosis for patients.

These findings will appear in the Sep 9 issue of Current Biology.

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