A new study has found an important link between breast cancer and the lungs, explaining why the cancer spreads, or metastasizes, to this organ. It is one of the most common sites for breast cancer metastasis. Researchers have discovered that the cancer’s tendency to spread to the lungs is based on a theory called “the seed and soil hypothesis.” 

Previous studies have shown that specific types of breast cancer cells, the breast cancer stem cell (CSC), are responsible for breast cancer’s spread to animals' lungs. In the new study, researchers developed an "outside the living organism" (ex vivo) model system to simulate different organ environments. The researchers were then able to observe the breast CSC’s inclination to grow inside the lungs, as explained in a press release. They identified the specific breast CSC and lung proteins that were involved in this interaction. By manipulating these CSCs and proteins, the researchers were able to reduce the movement of breast cancer to the lungs.

Lead researcher Alison Allan used an analogy of dandelion seeds to explain why breast cancer so often spreads to the lungs. When the dandelion releases its seeds, although the seeds blow everywhere, they do not grow everywhere they land. They only grow in soil that has the right nutrients. This is similar to metastasis. The tumor cells may spread to various areas of the body, but different organs have important factors that attract tumor cells to them and then support their survival and growth into new tumors.

“A lot of research has been done on the cancer cells because they’re easy to study, but not a lot has gone into understand the ‘soil’ factor. We’ve uncovered come specific proteins that are produced in the lung that seem to interact with cancer stem cells, making the lungs a congenial place for cancer cells to grow,” Allan explained in the press release.

Future studies will set out to determine whether higher levels of breast CSCs increase the likelihood of mestastsis in the lungs. If so, researchers will explore if directed monitoring could lead to successful treatment.

 

Source: Chu J, Xia Y, Chin-Yee B, Goodale D, Croker A, Allan A. Lung-Derived Factors Mediate Breast Cancer Cell Migration through DC44 Receptor-Ligand Interactions in a Novel Ex Vivo System for Analysis of Organ-Specific Soluble Proteins. Neoplasia. 2014.