Repair of radiation damage in Lewis lung carcinoma cells following in situ treatment with fast neutrons and $gamma$ rays

Journal Article · Tue Apr 01 04:00:00 EDT 1975 · Cancer Res., v. 35, no. 4, pp. 932-938

OSTI ID:4164083

Shipley, W U; Stanley, J A; Courtenay, V D; Field, S B

Lewis lung tumor cells were irradiated with $sup 60$Co $gamma$ rays or cyclotron-produced neutrons in situ as solid s.c. tumors or in vitro as single cell suspensions. Cell survival was assayed by colony formation both in vitro in soft agar and in the lungs of isogeneic recipient mice. Survival curve characteristics measured in vitro were: D$sub 0$ = 111 rads, D/sub q/ = 342 rads, n = 22 for $gamma$-rays, and D$sub 0$ = 61 rads, D/sub q/ = 46 rads, n = 2 for neutrons. In situ, the hypoxic fraction was 0.36. Irradiation in situ gave, for the hypoxic subpopulation, D$sub 0$ = 315 rads for $gamma$-rays and D$sub 0$ = 91 rads for neutrons. The oxygen-enhancement ratio for $gamma$ rays was 2.8 and for neutrons was 1.5. Using the split-dose technique, in which two equal doses were administered, separated by 4 hr chronically hypoxic tumor cells repaired sublethal damage after $gamma$ ray but not after neutron irradiation. Repair of potentially lethal damage, assayed by leaving tumor cells in situ up to 24 hr posttreatment, could not be detected after neutrons, but after $gamma$ rays it was observed as a 3- to 6-fold increase in survival. The repair of potentially lethal damage increased the relative biological effectiveness of neutrons from 3.7 at a survival level of 5 percent when assayed immediately after treatment to 4.7 when assayed 6 to 24 hr after treatment. These observations, primarily limited to the chronically hypoxic subpopulation of tumor cells, suggest that decreased repair of potentially lethal damage as well as sublethal damage may be an important radiobiological difference between the effects of high and low linear energy transfer radiation. (auth)

• Research Organization: Inst. of Cancer Research, Sutton, Eng.
• NSA Number: NSA-33-003259
• OSTI ID: 4164083
• Journal Information: Cancer Res., v. 35, no. 4, pp. 932-938, Journal Name: Cancer Res., v. 35, no. 4, pp. 932-938; ISSN CNREA
• Country of Publication: United States
• Language: English

Related Subjects

*FAST NEUTRONS-- RBE
*TUMOR CELLS-- BIOLOGICAL REPAIR
560152* --Biomedical Sciences
Applied Studies--Radiation Effects--Radiation Effects on Animals--Vertebrates
ANOXIA
COMPARATIVE EVALUATIONS
FRACTIONATED IRRADIATION
GAMMA RADIATION
IN VITRO
IN VIVO
IRRADIATION
LET
LUNGS
MICE
N48520* --Life Sciences--Radiation Effects on Animals-- Vertebrates
OXYGEN ENHANCEMENT RATIO
SURVIVAL TIME