Carcinogenic and co-carcinogenic effects of radiation in rat mammary carcinogenesis and mouse T-cell lymphomagenesis: a review.
The importance of the promotion stage and of the physiological condition of target cells at the time of initiation is illustrated in both the rat mammary carcinogenesis and the mouse T-cell lymphomagenesis. In the former, prolactin was shown to be a powerful promoter regardless of the initiating agent. Prolactin was also found to be useful in detecting the carcinogenicity of the small doses of carcinogens; a high r.b.e. of 2.0 MeV fission spectrum neutrons was demonstrated by the application of prolactin to radiation-initiated mammary carcinogenesis in rats. In the latter, total-body irradiation involving both bone marrow and thymus facilitates chemically-initiated T-cell lymphomagenesis in mice. This could be attributed to the amplification of the cell population susceptible to a chemical carcinogen in the target tissue during the recovery phase after irradiation. The dual effect of a carcinogen, acting in the different phases of carcinogenesis was suggested by the split administration of N-nitrosoethylurea (NEU) in the induction of T-cell lymphomas. It is emphasized, through these findings, that besides the initiation by a genotoxic agent, the availability of a promoter or an inhibitor determines the fate of initiated cells, and that a modifier of target cells also plays a crucial role in the efficient induction of a tumour.
Yokoro
K
K
Niwa
O
O
Hamada
K
K
Kamiya
K
K
Seyama
T
T
Inoh
A
A
D000818:Animals; D003043:Cocarcinogenesis; D005038:Ethylnitrosourea; D005260:Female; D007953:Leukemia, Radiation-Induced; D008223:Lymphoma / Q000139:chemically induced / Q000209:etiology*; D008325:Mammary Neoplasms, Experimental / Q000139:chemically induced / Q000209:etiology*; D051379:Mice; D009381:Neoplasms, Radiation-Induced; D011388:Prolactin / Q000633:toxicity*; D051381:Rats; D013601:T-Lymphocytes
D011388:Prolactin; D005038:Ethylnitrosourea