Migration of Breast Cancer Cell Lines in Response to Pulmonary Laminin 332; Implications for Metastasis

Abstract

In order to determine whether lung tissue secretes a motility factor for breast cancer, minced fresh human pulmonary tissue was co‐cultured with MCF‐7 breast carcinoma cells. Dose‐dependent MCF‐7 migration was observed, consistent with a motility response to a factor secreted by the lung tissue. Pulmonary epithelial cells were isolated and cultured in defined medium. Concentrated conditioned lung culture medium induced motility in the breast carcinoma cell lines MDA‐MB‐231, SKBR3, and BT‐20 using a Boyden chamber assay. For MCF‐7, the motility was dose dependent by a scattering assay, when the concentrate was either in a soluble form or after deposition on tissue culture plastic. The deposited material was analyzed by mass spectrometry, revealing the α3 and β3 chains of the motility factor laminin 332 (LN332). Blocking antibodies to LN332 and to the LN332 receptor for motility, α3β1 integrin, inhibited motility to the same extent as the inhibition of motility that occurred when these antibodies were applied to MCF‐7 cells incubated with purified LN332. Finally, LN332 in normal lung was confirmed by immunohistochemistry. These experiments together showed that pulmonary LN332 induced motility in MCF‐7. These findings provide a mechanism for the migration of metastatic tumor cells from their arrest in the pulmonary vasculature into the surrounding tissue, allowing their establishment as a metastatic colony.