Authors: Huafeng Wei, M.D.,Ph.D. et al
We compared the effects and mechanisms of sevoflurane vs. propofol at equipotent dose (1 MAC vs 2 µM) on cell survival, proliferation and migration, intracellular calcium homeostasis in different types of human breast normal or cancer cells.
We used estrogen receptor positive (MCF7) and estrogen receptor negative (MDA-MB-436) human breast cancer cell lines or normal breast cells (MCF10A). Cells were exposed to sevoflurane for 3, 6, and 24 hours at concentrations of 0.5, 1.0 and 2.0 MAC and to propofol at concentrations of 1, 2, and 4 μM, which are clinically relevant doses and durations. Subsequent exposures were performed at equipotent sevoflurane vs. propofol (1 MAC vs. 2 μM) for 6 hours. The MTT reduction assay was used to assess cell survival. Cell proliferation was determined with DAPI and 5-bromodeoxyuridine (BrdU) immunostaining. The Transwell invasion assay was used to determine invasiveness of the cells. Cytosolic calcium concentration ([Ca2+]c) was measured using jellyfish specific photoprotein aequorin-based probe, after treating cells to equivalent propofol vs. sevoflurane. TRPV1 protein expression levels were quantified using Western Blot.
Sevoflurane affected breast cancer cell survival in dose-, time- and cell type-dependent manners. Exposure to sevoflurane, but not propofol, at equipotent and clinically relevant doses (1 MAC vs. 2 µM) for 6 hours significantly promoted breast cell survival in all three types of cells. Paradoxically, extreme exposure to sevoflurane (2 MAC, 24 hours) but not propofol (4 µM, 24 hrs) decreased survival in all three cell lines, although more apparent in the MCF-10A cells. Reduction of baseline [Ca2+]c with BAPTA-AM dramatically decreased cell survival only in both type of cancer but not control cells. Inhibition of Ca2+ influx through the TRPV1 receptor with the selective antagonist SB-366791 significantly reduced cell survival in all three type of cells, which was partially inhibited only by equipotent sevoflurane but not propofol. Six-hours exposure to sevoflurane or propofol had no significant effect on cell proliferation, metastasis or TRPV1 protein expression of all three cell lines, although baseline cell proliferation and metastasis in two types of breast cancer cells were significantly greater than in control breast cells. Sevoflurane caused significantly more overall elevation of [Ca2+]c than equipotent concentration of propofol, especially in MCF7 breast cancer cells.
Adequate activation TRPV1 and associated Ca2+ influx support baseline level of [Ca2+]c and cell survival, which may be a potential target of general anesthetics to affect breast cell survival, with sevoflurane significantly more potent than propofol. Both general anesthetics at clinically relevant concentrations and durations did not have significant effects on breast cancer cell proliferation or metastasis.