Enhancement of human tumor cell killing by L-canavanine in combination with gamma-radiation
On the basis of several physiological properties of L-canavanine, we have tested the prediction that this analogue of arginine would enhance the cytotoxic effects of gamma-rays in mammalian cells. Using the human colonic tumor cell line, HT-29, time-dose studies were performed with log-phase cultures in order to determine conditions which maximize the incorporation of L-canavanine into cellular proteins while leaving a large fraction of the cells viable for subsequent gamma-ray survival measurements. At an input ratio of 2.5 (L-canavanine:arginine), the analogue exerted a cytostatic effect on the cells for at least 6 days following one cell division. Little cell killing (less than 20%) by clonogenicity was caused by L-canavanine during the first 12 hr of treatment of log-phase cells, even at a L-canavanine:arginine ratio of 20. A 24-hr exposure, however, produced an exponential decrease in survival as a function of L-canavanine concentration. The interaction between L-canavanine treatment and gamma-ray damage with respect to cell survival was examined under several conditions and times based on the above findings. Optimal enhancement of X-ray-induced cytotoxicity (assayed by loss of clonogenicity) was observed with a 48-hr exposure to the analogue at a L-canavanine:arginine ratio of 10. A marked increase in radiosensitivity was observed when L-canavanine was administered either before or after irradiation of the cells. In both protocols, enhancement was seen at all radiation doses. Together with our earlier findings showing the antitumor activity of L-canavanine in L1210 murine leukemia, these results suggest the potential usefulness of this amino acid analogue in the treatment of cancer.
- Research Organization:
- Department of Biology, University of California, San Diego
- OSTI ID:
- 5714651
- Journal Information:
- Cancer Res.; (United States), Vol. 43:9
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ARGININE
RADIOSENSITIVITY EFFECTS
NEOPLASMS
RADIOSENSITIVITY
AMINO ACIDS
ANIMAL CELLS
ANTIMETABOLITES
BIOLOGICAL RADIATION EFFECTS
CELL CULTURES
GAMMA RADIATION
LARGE INTESTINE
MAN
RADIOSENSITIZERS
SYNERGISM
ANIMALS
BIOLOGICAL EFFECTS
BODY
CARBOXYLIC ACIDS
DIGESTIVE SYSTEM
DISEASES
DRUGS
ELECTROMAGNETIC RADIATION
GASTROINTESTINAL TRACT
INTESTINES
IONIZING RADIATIONS
MAMMALS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANS
PRIMATES
RADIATION EFFECTS
RADIATIONS
VERTEBRATES
550603* - Medicine- External Radiation in Therapy- (1980-)