title: Expression of transfected recombinant oncogenes increases radiation resistance of clonal hematopoietic and fibroblast cell lines selectively at clinical low dose rate.
abstract: To determine the effect of oncogene expression on gamma radiation sensitivity of hematopoietic compared to fibroblastic cells, we selected clonal sublines of an interleukin-3 (IL-3)-dependent hematopoietic progenitor cell line 32D cl 3 and NIH/3T3 embryo fibroblastic cells following transfection with each oncogene linked to the mycophenolic acid resistance gene. Each mycophenolic acid-resistant subclone demonstrated high levels of specific poly(A)+ mRNA for each oncogene. The parent line 32D cl 3 demonstrated similar radiosensitivity at 116 cGy/min (D0 126, n 1.17) compared to 5 cGy/min (D0 123, n 1.65). This pattern was not altered in subclones of 32D cl 3 cells transfected with the epidermal growth factor (EGF) receptor gene and grown in EGF (at 116 cGy/min D0 104, n 0.998, at 5 cGy/min D0 115, n 1.09), or in 32D cl 3 cells expressing the v-sis oncogene (at 116 cGy/min D0 122.4, n 1.79, at 5 cGy/min D0 135, n 1.43). In contrast, expression of the transfected oncogenes v-erb-B, v-abl, or v-src conferred significant radioresistance at 5 cGy/min dose rate (D0 194, n 1.77; D0 165.5, n 1.56; D0 171, n 1.28, respectively). With the exception of v-sis, oncogene expression resulted in nonautocrine factor independence of 32D cl 3 subclones, and production of donor origin tumors in syngeneic new-born or adult mice. Two rare spontaneous factor-independent subclones of 32D cl 3 were also tested. Nonautocrine clone 32D cl 2 demonstrated significantly increased radioresistance at low dose rate (D0 186, n 1.63), while autocrine (IL-3 producing) subclone 32D cl 4 revealed no significant increase in radioresistance at 5 cGy/min. The parent fibroblast cell line NIH/3T3 showed an intrinsic relative radioresistance at low dose rate (at 5 cGy/min D0 157.3, n 1.81, compared to 116 cGy/min D0 134.3, n 1.57). Expression in NIH/3T3 of transfected oncogenes v-abl, v-fms, v-fos, or H-ras increased radioresistance at low dose rate (D0 208.6, n 1.61; D0 206.6, n 1.51; D0 167.5, n 1.85; and D0 206.8, n 1.08, respectively). Thus expression of each of several oncogenes induces resistance to gamma irradiation at 5 cGy/min in hematopoietic and fibroblast cell lines. These data may help explain the clinical recurrence of oncogene-expressing leukemia and lymphoma cells after marrow stem cell ablative doses of low-dose-rate total-body irradiation.
authors.affiliation: Department of Radiation Oncology, University of Massachusetts Medical Center, Worcester 01655.
authors.forename: T J
authors.initials: TJ
authors.lastname: FitzGerald
authors.forename: S
authors.initials: S
authors.lastname: Henault
authors.forename: M
authors.initials: M
authors.lastname: Sakakeeny
authors.forename: M A
authors.initials: MA
authors.lastname: Santucci
authors.forename: J H
authors.initials: JH
authors.lastname: Pierce
authors.forename: P
authors.initials: P
authors.lastname: Anklesaria
authors.forename: K
authors.initials: K
authors.lastname: Kase
authors.forename: I
authors.initials: I
authors.lastname: Das
authors.forename: J S
authors.initials: JS
authors.lastname: Greenberger
mesh_terms: D000818:Animals; D002460:Cell Line; D002470:Cell Survival; D004274:DNA, Recombinant; D004307:Dose-Response Relationship, Radiation; D005347:Fibroblasts / Q000528:radiation effects; D006412:Hematopoietic Stem Cells / Q000187:drug effects / Q000528:radiation effects*; D006801:Humans; D007377:Interleukin-3 / Q000494:pharmacology; D009857:Oncogenes; D011836:Radiation Tolerance; D011994:Recombinant Proteins / Q000494:pharmacology; D014162:Transfection
chemical_list: D004274:DNA, Recombinant; D007377:Interleukin-3; D011994:Recombinant Proteins