Role of tumor necrosis factor-alpha and TRAIL in high-dose radiation-induced bystander signaling in lung adenocarcinoma.
In the present study, ionizing radiation (IR)-induced bystander effects were investigated in two lung cancer cell lines. A549 cells were found to be more resistant to radiation-conditioned medium (RCM) obtained from A549 cells when compared with the H460 exposed to RCM procured from H460 cells. Significant release of tumor necrosis factor-alpha (TNF-alpha) was observed in A549 cells after IR/RCM exposure, and the survival was reversed with neutralizing antibody against TNF-alpha. In H460 cells, significant release of TNF-related apoptosis-inducing ligand (TRAIL), but not TNF-alpha, was observed in response to IR, RCM exposure, or RCM + 2Gy, and neutralizing antibody against TRAIL diminished clonogenic inhibition. Mechanistically, TNF-alpha present in RCM of A549 was found to mediate nuclear factor-kappaB (NF-kappaB) translocation to nucleus, whereas the soluble TRAIL present in RCM of H460 cells mobilized the nuclear translocation of PAR-4 (a proapoptotic protein). Analysis of IR-inducible early growth response-1 (EGR-1) function showed that EGR-1 was functional in A549 cells but not in H460 cells. A significant decrease in RCM-mediated apoptosis was observed in both A549 cells stably expressing small interfering RNA EGR-1 and EGR-1(-/-) mouse embryonic fibroblast cells. Thus, the high-dose IR-induced bystander responses in A549 may be dependent on the EGR-1 function and its target gene TNF-alpha. These findings show that the reduced bystander response in A549 cells is due to activation of NF-kappaB signaling by TNF-alpha, whereas enhanced response to IR-induced bystander signaling in H460 cells was due to release of TRAIL associated with nuclear translocation of PAR-4.
Shareef
Mohammed M
MM
Weis Center for Research, Geisinger Clinic, Danville, Pennsylvania 17822-2616, USA.
Cui
Nuan
N
Burikhanov
Ravshan
R
Gupta
Seema
S
Satishkumar
Sabapathi
S
Shajahan
Shahin
S
Mohiuddin
Mohammed
M
Rangnekar
Vivek M
VM
Ahmed
Mansoor M
MM
D000230:Adenocarcinoma / Q000000981:diagnostic imaging*; D000818:Animals; D017209:Apoptosis / Q000502:physiology / Q000528:radiation effects; D024201:Bystander Effect / Q000502:physiology*; D045744:Cell Line, Tumor; D003114:Colony-Forming Units Assay; D051766:Early Growth Response Protein 1 / Q000172:deficiency / Q000235:genetics; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging*; D051379:Mice; D018345:Mice, Knockout; D011877:Radionuclide Imaging; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000502:physiology* / Q000528:radiation effects; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology* / Q000528:radiation effects; D014965:X-Rays
D051766:Early Growth Response Protein 1; C486109:Egr1 protein, mouse; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D014409:Tumor Necrosis Factor-alpha