MCF-7 breast cancer and 8932 pancreatic tumor cells

The human breast cancer cell line MCF-7 (ATCC^® HTB-22^™) was cultivated as a monolayer in Dulbecco's modified Eagle's medium (DMEM Biochrom, Germany) supplemented with 5% fetal calf serum (37 °C, 5% CO₂). The mouse pancreatic tumor cell line 8932 was maintained as a monolayer culture in Dulbecco's modified Eagle's medium (DMEM Biochrom, Germany) supplemented with 10% fetal calf serum (FCS) and 1% Penicillin/Streptomycin (Pen/Strep, Biochrom, Germany). This cell line was established from the pancreatic cancer of a Ptf1a^Cre/+;LSL-PIK3CA^H1047R/+ mouse as previously described ^{28, 29}. The cells were detached immediately before the NMR measurement with Trypsin/EDTA and centrifuged at 1300 rpm for 3 min. The cell pellet was dissolved in DMEM (supplemented with 10% FCS and 1% Pen/Strep) and transferred to an 8-mm susceptibility-matched NMR glass tube. The cell number was determined using a Neubauer cell counting chamber. For delineation of dead cells the solution of cells was stained with Trypan blue. Cell numbers were ~ 20-40 x 10⁶. To investigate the diffusion characteristics of tumor cells undergoing membrane changes, 8932 tumor cells were incubated with 0.002% Triton X-100 in the assay medium. At this concentration of Triton X-100, membrane permeabilization was an immediate process over several seconds, as tested in a preceding experiment with trypan blue staining.