Spontaneous and induced primary oncogenesis in natural killer (nk)‐cell‐deficient beige mutant mice

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Abstract
Spontaneous tumor development and primary oncogenesis were compared in a large number of NK 1 Abbreviations: NK, Natural killer; s.c, subcutaneously; i.u., infectious units; d.f., degree(s) of freedom; DMBA-LV, dime-thylbenzanthracene-induced murine leukemia virus; PVM, pneumonia virus of mice; Reo-3, Reo virus 3; MHV, murine hepatitis virus; LCM, lymphocytic choriomeningitis virus; MEV, murine encephalomyelitis virus; MVM, minute virus of mice; BP, benzo[alpha]pyrene. -deficient, homozygous C57B1/6-bg/bg mice and their NK normal, heterozygous + /bg littermate controls. In a group of 167 retired breeders followed for spontaneous tumors, the probability of survival for mice eventually dying with a tumor was greater for the NK-competent, +/bg than for the NK-deficient, homozygous C57BL/6-bg/bg mice (p = 0.0019), although the higher overall incidence of tumors in the bg/bg group (48%) was not significantly different from that in the +/bg group (37%). In the bg/bg group the incidence of tumor death appeared to increase relatively sharply in the 25- to 29-month age bracket compared to the fairly regular increase in incidence observed in the +/bg group. All the spontaneous tumors except 2 (discovered in +/bg mice) were classified histologically as widely disseminated malignant lymphomas. The other two were one squamous-cell carcinoma and one sarcoma. A total of 73 bg/bg mice injected s.c. with benzo[alpha]pyrene (BP) had a higher overall incidence of tumors (81%) (rhabdomyosarcomas) than 138 +/bg mice (64%) and in the largest group (0.3 mg, n = 85) the bg/bg group developed tumors, at a higher incidence (p = 0.01) and with a shorter latency (p = 0.025) than the +/bg group. On the other hand, mice injected with dimethylbenzanthracene or given 4 weekly doses of 160 rads of gamma irradiation showed no difference in overall tumor incidence. In addition, mice injected with various doses of DMBA-induced murine leukemia virus (DMBA-LV) also showed no significant difference in tumor incidence. Others have reported that some of these treatments (DMBA, split-dose irradiation) cause profound NK suppression, thereby reducing NK differences between the two groups of mice. These results suggest that a partial NK impairment in beige mutant mice early in life may lead to significantly greater rates of death with spontaneous malignant tumors late in life. Some primary oncogenesis treatments (BP) but not others (DMBA, split-dose irradiation, leukemia viruses) cause tumors with a greater incidence and shorter latency in beige mice. The results suggest, but do not prove, that NK cells play a role in surveillance against spontaneously arising, and possibly some types of carcinogen-induced, tumors.