Lung-Derived Factors Mediate Breast Cancer Cell Migration through CD44 Receptor-Ligand Interactions in a Novel Ex Vivo System for Analysis of Organ-Specific Soluble Proteins

Abstract

Breast cancer preferentially metastasizes to lung, lymph node, liver, bone, and brain. However, it is unclear whether properties of cancer cells, properties of organ microenvironments, or a combination of both is responsible for this observed organ tropism. We hypothesized that breast cancer cells exhibit distinctive migration/growth patterns in organ microenvironments that mirror common clinical sites of breast cancer metastasis and that receptor-ligand interactions between breast cancer cells and soluble organ-derived factors mediate this behavior. Using an ex vivo model system composed of organ-conditioned media (CM), human breast cancer cells (MDA-MB-231,MDA-MB-468, SUM149, and SUM159) displayed cell line-specific and organ-specific patterns of migration/proliferation that corresponded to their in vivo metastatic behavior. Notably, exposure to lung-CM increased migration of all cell lines and increased proliferation in two of four lines (P < .05). Several cluster of differentiation (CD) 44 ligands including osteopontin (OPN) and L-selectin (SELL) were identified in lung-CM by protein arrays. Immunodepletion of SELL decreased migration of MDA-MB-231 cells, whereas depletion of OPN decreased both migration and proliferation. Pretreatment of cells with a CD44-blocking antibody abrogated migration effects (P < .05). "Stemlike" breast cancer cells with high aldehyde dehydrogenase and CD44 (ALDH(hi)CD44(+)) responded in a distinct chemotactic manner toward organ-CM, preferentially migrating toward lung-CM through CD44 receptor-ligand interactions (P < .05). In contrast, organ-specific changes in migration were not observed for ALDH(low)CD44(-) cells. Our data suggest that interactions between CD44(+) breast cancer cells and soluble factors present in the lung microenvironment may play an important role in determining organotropic metastatic behavior.

Breast cancer molecular subtypes and the metastatic microenvironment: Review of literature

“…In addition to increased migratory patterns, MDA-MB-231 and MDA-MB-468 cell lines demonstrated cell line specific patterns of proliferation in response to organ-CM. MDA-MB-231 cells showed increased proliferation in the presence of liver and lung-CM and MDA-MB-468 cells showed increased proliferation in the presence of lung-CM [50] . These results indicate the potential of the lung microenvironment for promoting metastatic progression of breast cancer cells.…”

“…Organs representing common sites of breast cancer metastasis (lung, bone, liver, brain, LN) are isolated from healthy mice and used to generate organ-conditioned media (CM). Using this model, Chu et al (2014) demonstrated that different human breast cancer cell lines show specific chemotactic and proliferative behaviours in response to various organ-CM, reflective of their metastatic behaviours in vivo [50] . Specifically, the most aggressive of the cell lines, MDA-MB-231, showed increased migration patterns towards bone, lymph node, and lung-CM.…”

Effect of dacarbazine on CD44 in live melanoma cells as measured by atomic force microscopy-based nanoscopy

“…The percentage of viable cells was about 99% and the cell number was about 3×10 4 cells/mL. Cells in exponential growth were placed in 96-well plates at a final concentration of 3×10 4 cells/mL and then treated with differing concentrations of DTIC for differing periods of time. Cell viability was assessed using the Cell Counting Kit (CCK-8) assay (Beyotime Biotechnology, Shanghai, China) according to the manufacturer's instructions.…”

“…[1][2][3][4] Tumor cells with CD44 receptor proteins (CD44 treatment of melanoma. [8][9][10] Increased levels of soluble CD44s (the standard isoform, comprising exons 1-5 and 16-20) and soluble CD44v (splice variants containing variable exons) in the circulation of cancer patients have been considered prognostic markers for disease progression.…”

“…Modulation of the binding affinity of CD44 is important for cellular adhesion, proliferation, apoptosis, migration, tumor metastasis, and signal transduction. [1][2][3][4] Previously, serialtriggering and kinetic proofreading models of cell activation suggested that very high affinity (less than or equal to a few nanomolar) would be detrimental to the signaling process. 68 On the other hand, very low affinity, in the millimolar range for nonaffinity ligands, leads to antagonist activity.…”