UC Irvine

Cell-to-substrate interactions are known to regulate important cellular processes such as migration, proliferation, and intercellular signaling. Cancer cells remodel the surrounding collagen matrix and promote collagen fibrillogenesis for invasion. This increases substrate density and activates the mechanosensing pathway for events such as adhesion and migration. Recent studies indicate that metabolism is able to affect cancer invasion and that mitochondria are recruited towards the invading edges of the cell. There seems to be a link between the mechanosensing and metabolism pathway in promoting invasion; however, it is unclear how these are regulated and affects mitochondria trafficking towards the protruding edges. In this thesis, focal adhesion (FA) dynamics within NIH3T3 cells were studied using the Number and Molecular Brightness analysis and were found to adapt to the underlying nanotopography by modulating their adhesion size and turnover dynamics leading to a change in cell speed. This laid the foundational studies within cancer cells. In MDA-MB231 breast cancer cells, raster imaging correlation spectroscopy (RICS) was used to study focal adhesion dynamics in response to substrate topography and collagen density. The increase of substrate density and addition of nanolines showed a decrease in FA protein dynamics and increased tension, respectively. In addition, Fluorescent lifetime imaging microscopy (FLIM) was used to measure metabolic signatures within MDA-MB231 cells. A shift from oxidative phosphorylation (OXPHOS) to glycolysis (GLY) with increasing collagen density was observed. Since the increase of substrate density is known to upregulate focal adhesion formation, actin polymerization, migration, and invasion, a large amount of ATP is consumed. Rac1 activation was stimulated to promote membrane formation and actin polymerization to observe mitochondria recruitment. Mitochondria transport speed increased when Rac1 was activated compared to when it was inactivated, specifically in breast tumor cells. This shows that mitochondria are transported to regions of high energy consumption and sustain processes needed for invasion. In addition, metabolism of the invading protrusions was found to shift towards a GLY metabolic signature. Results indicate that collagen density, metabolism and mitochondria trafficking all play an important role in regulating cancer cell invasion. When developing therapies, these parameters should be considered in order to effectively prevent metastasis.