Extracellular Matrix-Mediated Breast Cancer Cells Morphological Alterations, Invasiveness, and Microvesicles/Exosomes Release

Breast cancer is a leading disease in women. Several studies are focused to evaluate the critical role of extracellular matrix (ECM) in various biochemical and molecular aspects but also in terms of its effect on cancer cell morphology and therefore on cancer cell invasion and metastatic potential. ECM fibrillar components, such as collagen and fibronectin, affect cell behavior and properties of mammary cancer cells. The aim of this study was to investigate using the scanning electron microscopy (SEM) how the highly invasive MDA-MB-231 breast cancer cells, interplaying with ECM substrates during cell migration/invasion, modify their morphological characteristics and cytoplasmic processes in relation to their invasive potential. In particular we reproduced and analyzed how natural structural barriers to cancer cell invasion, such as the basement membrane (Matrigel) and fibrillar components of dermis (fibronectin as well as the different concentrations/array of type I collagen), could induce morphological changes in 3D cultures. Interestingly, we demonstrate that, even with different effects, all collagen concentrations/arrays lead to morphological alterations of breast cancer cells. Intriguingly, the elongated mesenchymal shaped cells were more prominent in 3D cultures with a dense and thick substrate (thick Matrigel, high concentrated collagen network, and densely packed collagen fibers), even though cells with different shape produced and released microvesicles and exosomes as well. It is therefore evident that the peri-tumoral collagen network may act not only as a barrier but also as a dynamic scaffold which stimulates the morphological changes of cancer cells, and modulates tumor development and metastatic potential in breast cancer.