OBJECTIVEThe aim of this study is to investigate the release of TNF-alpha mRNA in two lung cancer cell lines in vitro and the regulation of TNF-alpha mRNA expression by ionizing radiation.

METHODSTwo lung cancer cell lines (A549 and NCI-H596) were investigated for their TNF-alpha mRNA expression before and after exposure to different irradiation doses (2, 5, 10, 20, 30 and 40 Gy) and at different time intervals (1, 3, 6, 12, 24, 48 and 72 hours after irradiation). The TNF-alpha mRNA expression was quantified by fluorescence-based real-time quantitative RT-PCR. Colony formation assays were performed after irradiation with a dose of 2, 4, 6, and 8 Gy to determine the clonogenic survival.

RESULTSDependent on the dose given, irradiation was found to cause increasing induction of TNF-alpha mRNA expression of NCI-H596 cells, reaching maximal level after 40 Gy irradiation, which was 83 times higher than that of normal controls. On the other hand, dependent on the time after irradiation, TNF-alpha mRNA expression of NCI-H596 and A549 cells was increased, reaching maximal level at 6h for NCI-H596 cells, which was 568 times higher than that of normal control cells. TNF-alpha mRNA expression of A549 cells was increased to maximum at 1 h after irradiation and was 136 times higher than that of control cells. Colony formation efficiency (number of colonies divided by the number of inoculated cells) of unirradiated control A549 and NCI-H596 cells was 0.37-0.45 and 0.12-0.24, respectively. The survival fraction (SF) of A549 cells was 47.3% +/- 9.0% at 2 Gy, 18.0% +/- 3.0% at 4 Gy, 6.0% +/- 2.0% at 6 Gy, 1.4% +/- 0.3% at 8 Gy. The SF of NCI-H596 cells was 55.2% +/- 51.0% at 2 Gy, 15.9% +/- 9.2% at 4 Gy, 3.5% +/- 1.7% at 6 Gy; 0.9% +/- 0.6% at 8 Gy. The curves of TNF-alpha expression of the two tumor cell lines were nearly identical, therefore the radiosensitivity of these cell lines was similar. Statistically there was no significant difference for D(0) and D(q) (P > 0.05).

CONCLUSIONThe two lung cancer cell lines studied express TNF-alpha following irradiation in a time- and irradiation dose-dependent manner. Radiation-induced TNF-alpha production of tumor cells may be of paramount importance not only for tumor behaviour, but also in respect to potential damage to normal tissues and the clinical status of the host.

Adenocarcinoma ; diagnostic imaging ; metabolism ; pathology ; Carcinoma, Squamous Cell ; diagnostic imaging ; metabolism ; pathology ; Cell Line, Tumor ; Humans ; Lung Neoplasms ; diagnostic imaging ; metabolism ; pathology ; RNA, Messenger ; biosynthesis ; genetics ; Radiation Dosage ; Radiography ; Reverse Transcriptase Polymerase Chain Reaction ; Tumor Necrosis Factor-alpha ; biosynthesis ; genetics