Role of Cu metabolism in the cisplatin-sensitive and resistant ovarian cancer cells

Abstract

Ovarian cancer is the fourth most common cancer among women worldwide, leading to high mortality rates. Platinum anti-cancer drugs have been widely used in the treatment of ovarian cancers, but the development of resistance to these drugs is a rapidly growing impediment for their clinical use. Studies of the cell morphology using IncuCyte Zoom and HoloMonitor M4 have shown that A2780.CisR cells contained heterogeneous cell populations that partially underwent epithelial-to-mesenchymal transition (EMT). Mesenchymal A2780.CisR cells were likely to be more resistant to a cytotoxic natural killer (NKL) cell line, compared with the epithelial A2780 cells. Mesenchymal phenotype was associated with lower total Cu content and higher total Fe content in A2780.CisR compared with A2780 cells under physiologically relevant conditions (2.0 M Cu(II) or 10 M Fe(III) for 24 h). Conversely, live cell confocal microscopy studies with a novel ratiometric Cu(I)-sensitive fluorescent dye, InCCu1, revealed higher cellular content of labile Cu in A2780.CisR cells compared with A2780 cells. Moreover, the InCCu1 dye showed promise for differential staining of multiple cellular organelles, including mitochondria, endosomes/lysosomes, fat droplets and budding extracellular vesicles. Fat droplets were more abundant in A2780.CisR compared with A2780 cells and concentrated at the advancing edges of cellular protrusions (shown by InCCu1 and Nile Red staining). Comparison of the biochemical content of cell membranes using ATR-FTIR (attenuated total reflection Fourier transform infrared) spectroscopy technique showed higher relative content of fatty acids and cholesterol in the membranes and surrounding environments of A2780.CisR compared with A2780 cells.