Abstract
Abstract Expression of P-glycoprotein (P-gp), the multidrug resistance (MDR) 1 gene product, can lead to MDR in tumors. Previous studies on multidrug-resistant cells have suggested changes in membrane fluidity associated with P-gp expression in drug-selected resistant cells. However, Aleman and co-workers have shown that, in MDR1 transfected cells, expression of P-gp has little effect on membrane fluidity and the changes in this parameter observed in drug-selected cells must reflect other host adaptations to drug selection. In this study and the other reported on drug-selected resistant cells, membrane fluidity has been measured using fluorescent membrane probes and fluorescence anisotropy or electron spin resonance on cell population samples (Aleman et al. Cancer Res. 2003 63:3084-91). Here, we propose to explore the plasma membrane microfluidity by using the fluorescent membrane probe DiA and fluorescence correlation micro-spectroscopy (FCM-S) on a single living cell and nanometer scale. By using the fluorescent membrane probe DiA and FCM-S to explore the plasma membrane micro-fluidity, we have previously shown a decrease in plasma membrane micro-fluidity in LR73R cells (the Chinese hamster ovarian LR73 cells transfected with MDR1 cDNA; Boutin et al., J Biomed Opt. 2009 14: 034030). Moreover, a strategy using flow cytometry and calcein-AM functional fluorescence-activated cell sorting permitted us to select two cell populations from LR73R cells expressing distinct levels of P-gp function. In this case, we were able to observe distinct level of membrane micro-fluidity in the two populations. Cells showing high level of calcein-AM uptake presented a higher membrane micro-fluidity. In contrast, the FCM-S yielded opposite data when we compared the membrane micro-fluidity of several parental cell lines (MCF7, KB3.1, LR73, ME-SSA) and their resistant counterparts which have been selected in the presence of anticancer drugs. Our data are not in agreement with previous published data and demonstrates clearly that alterations that can affect drug-selected cells do not induce any changes in membrane fluidity. Moreover, micro-analysis of cell membrane could allow to more precise measurements of membrane fluidity. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 690. doi:10.1158/1538-7445.AM2011-690
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