title: Radiation-induced TNFα cross signaling-dependent nuclear import of NFκB favors metastasis in neuroblastoma.
abstract: Ascertaining function-specific orchestration of NFκB in response to radiation may reveal a molecular blue-print that dictates induced relapse and metastasis of the neuroblastoma. We recently demonstrated that sustained activation of NFκB caused by ionizing radiation (IR)-initiated TNFα-NFκB feedback signaling leads to radioresistance and recurrence of neuroblastoma. We investigated whether muting IR-triggered or TNFα-dependent second-signaling feedback-dependent NFκB nuclear import results in limiting IR-altered invasion and metastasis. Neuroblastoma cells were exposed to 2 Gy and incubated for 1 h or 24 h. The cells were then treated with an NFκB-targeting peptide blocker, SN50. Upon confirming the blockade in DNA-binding activity, transcription driven transactivation of NFκB and secretion of soluble TNFα, transcriptional alterations of 93 tumor invasion/metastasis genes were assessed by using QPCR profiling and then were selectively validated at the protein level. Exposure to 2 Gy induced 63, 42 and 71 genes in surviving SH-SY5Y, IMR-32 and SK-N-MC cells, respectively. Blocking post-translational nuclear import of NFκB comprehensively inhibited both initial activation of genes (62/63, 34/42 and 65/71) triggered by IR and also TNFα-mediated second signaling-dependent sustained (59/63, 32/42 and 71/71) activation of tumor invasion and metastasis signaling molecules. Furthermore, alterations in the proteins MMP9, MMP2, PYK-2, SPA-1, Dnmt3b, Ask-1, CTGF, MMP10, MTA-2, NF-2, E-Cadherin, TIMP-2 and ADAMTS1 and the results of our scratch-wound assay validate the role of post-translational NFκB in IR-regulated invasion/metastasis. These data demonstrate that IR-induced second-phase (post-translational) NFκB activation mediates TNFα-dependent second signaling and further implies that IR induced NFκB in cells that survive after treatment regulates tumor invasion/metastasis signaling.
authors.affiliation: Radiation Biology Research Laboratory, Department of Radiation Oncology, University of Oklahoma Health Sciences Center, BMSB 737, 940 Stanton L. Young Boulevard, Oklahoma City, OK, USA.
authors.forename: Sheeja
authors.initials: S
authors.lastname: Aravindan
authors.forename: Mohan
authors.initials: M
authors.lastname: Natarajan
authors.forename: Terence S
authors.initials: TS
authors.lastname: Herman
authors.forename: Natarajan
authors.initials: N
authors.lastname: Aravindan
mesh_terms: D021581:Active Transport, Cell Nucleus; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism*; D006801:Humans; D016328:NF-kappa B / Q000378:metabolism*; D009361:Neoplasm Invasiveness; D009447:Neuroblastoma / Q000532:radiotherapy / Q000556:secondary*; D011836:Radiation Tolerance; D015398:Signal Transduction / Q000502:physiology / Q000528:radiation effects*; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology*; D014945:Wound Healing
chemical_list: D016328:NF-kappa B; D014409:Tumor Necrosis Factor-alpha