[Experimental study of the antitumor effect of Z-100 in the treatment of MM46 tumor transplanted in C3H/He mice. 2. Effect of the combination therapy of radiation and long term administration of Z-100].

Female C3H/He mice aged 14 weeks with transplanted MM46 tumor were used to investigate the effect of an immunomodulator, Z-100 (an arabinomannan lipid extracted from Mycobacterium tuberculosis strain Aoyama B) combined with local irradiation of 30 Gy (3,000 rad). Daily doses of 5 micrograms, 50 micrograms and 500 micrograms/kg of Z-100 were injected intramuscularly for 14 consecutive days after irradiation, and 2 times a week for 6 weeks thereafter. The antitumor effect was evaluated by the changes in tumor volume and survival curves. In groups administered 50 micrograms and 500 micrograms/kg of Z-100, tumor growth decreased significantly compared with the control group (radiotherapy group). Concerning survival rates of each group of mice, there were no marked differences between Z-100 administered groups and the control group. To clarify the mechanisms of action of Z-100, the changes in the lymphocyte subsets infiltrated into tumor tissue after Z-100 treatment were analysed immunohistochemically using monoclonal antibodies, anti-Thy 1.2, anti-Lyt-1, anti-Lyt-2, anti-L3T4, MAS034b and MAS053c and avidin-biotin-peroxidase complex method (ABC method). In the findings of immunohistochemical studies, differences were hardly observed between groups administered Z-100 and groups treated with radiation only. From these results, it was concluded that immunological effects of Z-100 resembled that of radiotherapy on the topical tumor tissue.