Simultaneous visualization of membrane fluidity and morphology defines adhesion signatures of cancer cells

We developed an advanced optical microscope for the simultaneous visualization of membrane fluidity and morphology to define cell adhesion signatures. This microscope combines ratiometric spectral imaging of membrane fluidity and interferometric imaging of membrane morphology. As a preliminary demonstration, we simultaneously visualized the interface between a giant unilamellar vesicle (GUV) and a glass substrate at different temperatures. We identified more fluid regions of the membrane and membrane adhesion sites (conversely, low-fluidic, ordered membrane domains correlate with nonadhered regions). This microscopic system was applied to human breast cancer cell lines with different malignancies; then, we identified adhesion signature of cancer cells: 1) low-fluidic, ordered membrane domains at the cell periphery and 2) large fluidic deviation at the nonadhered region. Inhibition of the cholesterol synthesis pathway suppresses the ordered membrane domains at the cancer cell periphery; thus, high level of cholesterol supports the appearance. Furthermore, an inhibitor of the unsaturated lipid synthesis pathway suppressed the large fluidic deviation at the nonadhered region; variation of unsaturated lipids contributes to heterogeneity of the cancer membrane. Therefore, our advanced optical microscopy enables us to couple membrane physical properties with cell adhesion, leading to definition of adhesion signatures of broad cell types, not just for cancer cells, that regulate life phenomena.