Topography, Nanomechanics, and Cell Surface Components of Cancer Cells Examined by Combined Atomic Force Microscopy and Raman Microspectroscopy

The investigation of the nanostructures and hydrophobic properties of cancer cell membranes is of importance for elucidating the plasma membrane roles in protein folding, membrane fusion, and cell adhesion that are directly related to cancer cell biophysical properties, such as aggressive growth and migration. On the other hand, the chemical component analysis of the cancer cell membrane could be potentially applied in the clinical diagnosis of cancer by the identification of specific biomarker receptors expressed on cancer cell surfaces. In the present work, a combined atomic force microscopy (AFM) and Raman microspectroscopy technique was applied to detect the difference in nanomechanics and membrane chemical components between two cancer cell lines, human lung adenocarcinoma epithelial cells (A549) and human breast cancer cells (MDA-MB-435 with and without expression of BRMS1 metastasis suppressor). The membrane surface adhesion forces for these cancer cells acquired in culture medium were measured using AFM at 0.478 +/- 0.091 nN for A549 cells, 0.253 +/- 0.070 nN for 435 cells, and 1.114 +/- 0.281 nN for 435/BRMS1 cells, and the cell spring constant was measured at 2.62 +/- 0.682 mN/m for A549 cells, 2.105 +/- 0.691 mN/m for 435 cells, and 5.448 +/- 1.081 mN/m for 435/BRMS1 cells. Raman spectral analysis indicated similar peaks between the A549 cells and the breast cancer cell lines 435 and 435/BRMS1 including similar to 720 cm(-1) (guanine band of DNA), 940 cm(-1) (skeletal mode polysaccharide), 1006 cm(-1) (symmetric ring breathing phenylalanine), and 1451 cm(-1) (CH deformation). Slight variations were observed between similar to 780-985 cm(-1) (DNA/RNA and proteins) and 1035-1210 cm(-1) (lipid and proteins).