Contractile Forces Contribute to Increased Glycosylphosphatidylinositol-anchored Receptor CD24-facilitated Cancer Cell Invasion

• Published in: The Journal of biological chemistry 2011-10, Vol.286 (40), p.34858-34871
• Main Authors: Mierke, Claudia Tanja, Bretz, Niko, Altevogt, Peter
• Format: Article
• Language: English
• Subjects: Biophysics; Breast Neoplasms - metabolism; CD24; CD24 Antigen - metabolism; Cell Line, Tumor; Cell Migration; Cell Movement; Collagen - chemistry; Contractile Forces; Cytoskeletal Remodeling Dynamics; Cytoskeleton - metabolism; Extracellular Matrix - metabolism; Female; Gene Expression Regulation, Neoplastic; Glycosylphosphatidylinositols - metabolism; Humans; Integrin; Integrin beta1 - metabolism; Invasion; Lung Neoplasms - metabolism; Matrix Metatalloproteinases; Models, Biological; Molecular Biophysics; Muscle Contraction; Neoplasm Invasiveness; Neoplasm Metastasis; siRNA; Tumor
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M111.245183

The malignancy of a tumor depends on the capability of cancer cells to metastasize. The process of metastasis involves cell invasion through connective tissue and transmigration through endothelial monolayers. The expression of the glycosylphosphatidylinositol-anchored receptor CD24 is increased in several tumor types and is consistently associated with increased metastasis formation in patients. Furthermore, the localization of β1-integrins in lipid rafts depends on CD24. Cell invasion is a fundamental biomechanical process and usually requires cell adhesion to the extracellular matrix (ECM) mainly through β1 heterodimeric integrin receptors. Here, we studied the invasion of A125 human lung cancer cells with different CD24 expression levels in three-dimensional ECMs. We hypothesized that CD24 expression increases cancer cell invasion through increased contractile forces. To analyze this, A125 cells (CD24 negative) were stably transfected with CD24 and sorted for high and low CD24 expression. The invasiveness of the CD24high and CD24low transfectants was determined in three-dimensional ECMs. The percentage of invasive cells and their invasion depth was increased in CD24high cells compared with CD24low cells. Knockdown of CD24 and of the β1-integrin subunit in CD24high cells decreased their invasiveness, indicating that the increased invasiveness is CD24- and β1-integrin subunit-dependent. Fourier transform traction microscopy revealed that the CD24high cells generated 5-fold higher contractile forces compared with CD24low cells. To analyze whether contractile forces are essential for CD24-facilitated cell invasion, we performed invasion assays in the presence of myosin light chain kinase inhibitor ML-7 as well as Rho kinase inhibitor Y27632. Cell invasiveness was reduced after addition of ML-7 and Y27632 in CD24high cells but not in CD24neg cells. Moreover, after addition of lysophosphatidic acid or calyculin A, an increase in pre-stress in CD24neg cells was observed, which enhanced cellular invasiveness. In addition, inhibition of the Src kinase or STAT3 strongly reduced the invasiveness of CD24high cells, slightly reduced that of CD24low cells, and did not alter the invasiveness of CD24neg cells. Taken together, these results suggest that CD24 enhances cell invasion through increased generation or transmission of contractile forces.