title: Genetic radiotherapy overcomes tumor resistance to cytotoxic agents.
abstract: We report that radiation enhances gene therapy of a radioresistant tumor by upregulating the induction of a chimeric gene encoding a radiosensitizing protein, tumor necrosis factor alpha (TNF-alpha). We ligated the radiation-inducible CArG elements of the radiation-inducible Egr-1 promoter/enhancer region upstream to the transcriptional start site of the human TNF cDNA (pE425-TNF). This construct was transfected using cationic liposomes into the variant murine fibrosarcoma cell line, P4L. The P4L cell line was both radioresistant (D0 = 188) and resistant to TNF. After a single intratumoral injection of 10 micrograms of pE425-TNF in cationic liposomes and two 20-Gy doses of irradiation, mean tumor volumes were significantly reduced in P4L tumors as compared to those receiving either pE425-TNF in liposomes or radiation alone (P = 0.01). TNf protein in P4L tumors was induced by radiation as high as 29 times control levels and remained detectable for 14 days. Our data indicate that combined gene therapy using liposomes, together with ionizing radiation to locally activate the induction of a radiosensitizing protein, is successful at overcoming resistance to both TNF and radiation.
authors.affiliation: Department of Radiation and Cellular Oncology, University of Chicago, Illinois 60637, USA.
authors.forename: L P
authors.initials: LP
authors.lastname: Seung
authors.forename: H J
authors.initials: HJ
authors.lastname: Mauceri
authors.forename: M A
authors.initials: MA
authors.lastname: Beckett
authors.forename: D E
authors.initials: DE
authors.lastname: Hallahan
authors.forename: S
authors.initials: S
authors.lastname: Hellman
authors.forename: R R
authors.initials: RR
authors.lastname: Weichselbaum
mesh_terms: D000818:Animals; D003131:Combined Modality Therapy / Q000379:methods; D005260:Female; D005354:Fibrosarcoma / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy / Q000628:therapy*; D015316:Genetic Therapy; D008081:Liposomes; D051379:Mice; D008819:Mice, Nude; D009374:Neoplasms, Experimental / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy / Q000628:therapy*; D009381:Neoplasms, Radiation-Induced; D011836:Radiation Tolerance; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000008:administration & dosage / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D008081:Liposomes; D014409:Tumor Necrosis Factor-alpha