2.2. Cell Viability Assay

TF and gefitinib were tested in vitro for cytotoxicity against gefitinib resistant NSCLC cell line PC-9R in 96-well plates by using the MTT assay. In brief, a number of 2500 cells/well were seeded into 96-well plates and cultured for 24 h. After that, the medium was replaced with variable concentrations of TF alone or combined with indicated dose of gefitinib in full growth medium. Cells were exposed to variable concentrations of TF alone or in combined with indicated doses of gefitinib for 24 h followed by the MTT assay to determine cell survival rates. Using a microplate reader, the absorbance of each sample was read at OD570 nm.