Imaging of P-glycoprotein of H69/VP small-cell lung cancer lines by scanning near-field optical microscopy and confocal laser microspectrofluorometer.

Chemoresistance remains the major obstacle to successful therapy of the lung cancer. The multi-drug resistance (MDR) is generally associated with altered expression of drug transporter proteins, such as P-glycoprotein (P-gp). So the distribution of P-gp on the membrane is of great importance to further study the interaction between drug and P-gp. In the present work, the P-gp of the H69/VP small-lung cancer cells was detected using monoclonal antibody UIC2. A secondary goat-anti mouse antibody coupled with biotin was used. The fluorescence emission was detected from a streptavidin-Texas Red. Results were investigated by a homemade scanning near-field optical microscope (SNOM) coupled to a confocal laser microspectrofluorometer (CLMF). Topographical images and localized spectra were obtained at the level of one cell membrane. It was found that the distribution of P-gp is not homogeneous and this observation is basically in accord with the fluorescent images obtained by classical microscopy. The distribution of P-gp would be localized in a higher region on a cell surface. This methodology would also enhance our understanding of MDR under physiological conditions.