Figure 1.

TTField-mediated inhibition of viability is enhanced by hyperthermia. (A) The scheme illustrates the treatment of PDAC cells with TTFields at a regular incubation temperature of 37°C or mild hyperthermia at 38.5°C. (B) The human PDAC cell lines AsPC-1, BxPC-3 and BxGEM were incubated at 37°C or 38.5°C in the presence (TTF) or absence (CO) of TTFields at 150 kHz and an intensity of less than 0.7 V/cm. To measure TTField effects as a function of treatment duration, PDAC cells were treated for 1 to 6 days in separate experiments. The examination of all 6 days together in one large experiment was not possible because the availability of the cell culture plates with antenna wires was limited. At the end of each single experiment, the viability was measured by MTT assay, the results were accumulated as a total curve for each cell line, and the values of each curve were normalized to start at 0 on day 1. (C) The cells were treated as described above, and the viability was analyzed 3 or 6 days later by MTT assay. The controls were set to 1. (D) The morphology of the cells, which were treated as described above, was microscopically examined at 100× magnification 6 days after treatment, and representative images are shown. The scale bar indicates 100 µm. (E) Likewise, the viability of the human, nonmalignant pancreatic duct cell line CRL-4023 was evaluated by MTT assay and microscopic evaluation at 100× magnification. Representative images of each treatment group of CRL-4023 cells 6 days after treatment are shown. Three independent experiments were performed at least in triplicate, and the data are presented as the means ± SD; *P < 0.05, **P < 0.01.