Table I.

Comparison of radiosensitivity of untransfected, control siRNA-transfected and TLR9 siRNA-transfected A549 cells treated with IR or CpG ODN 7909.

Group	D0	Dq	N	SF2	SER
TLR9 siRNA + IR	2.38	4.39	2.85	0.82	1.03
Control + IR	2.46	4.56	2.86	0.84	–
Control siRNA + IR	2.42	4.40	2.82	0.82	1.02
TLR9 siRNA + CpG ODN + IR	2.41	4.40	2.82	0.81	1.01
Control + CpG ODN + IR	1.92	2.90	2.52	0.67	1.28
Control siRNA + CpG ODN + IR	1.91	3.00	2.57	0.68	1.29

A549 cells treated with CpG ODN 7909 plus IR exhibited lower values of D0, Dq, N and SF2 compared with those treated with IR alone, and the SER was 1.28. No significant difference between the D0, Dq, N and SF2 values in the TLR9 siRNA-transfected A549 cells treated with CpG ODN 7909 plus IR compared with those treated with IR alone was observed, and the SER was 1.01. Compared with those of TLR9 siRNA-transfected A549 cells, the D0, Dq, N and SF2 values of control siRNA transfection cells demonstrated no significant difference. D0, slope rate of survival curve; Dq, initial shoulder of survival curve; N, extrapolation value of D0, which is an associated parameter reflecting primary radiation sensitivity of cells; SF2, the survival fraction after 2 Gy irradiation; TLR9, toll-like receptor 9; CpG ODN, cytosine-phosphorothioate-guanine-containing oligodeoxynucleotides; IR, irradiation; SER, sensitivity enhancement ratio; si, small interfering.