Interleukin-2 and CD80 transfectants of a methylcholanthrene-induced murine sarcoma Mc12 (Mc12-IL-2 and Mc12-CD80 cells) with similar tumorigenicity in euthymic mice were utilized for experiments designed to investigate a co-stimulatory role of the CD80 molecule in allogeneic, congenitally athymic (nu/nu) mice. The CD80-transfected cells were as tumorigenic in nu/nu mice as the parental Mc12 sarcoma. The IL-2-transfected cells grew only transiently and regressed in all nu/nu recipients during four weeks after challenge with doses up to 5x10(7) cells. The 1:1 mixture of parental Mc12 with Mc12-CD80 cells grew progressively in all inoculated nu/nu mice; in a 1:1 mixture with parental Mc12 cells, Mc12-IL-2 cells were able to cause regressions in approximately 50% of nu/nu mice; the 1:1 mixture of Mc12-IL-2 and Mc12-CD80 transfectants showed only transient growth and regressed during four weeks in all inoculated nu/nu mice. Adoptive transfer of cell-mediated immunity revealed that spleen cells from tumor regressors were capable of transferring the resistance to Mc12 tumor in nu/nu mice. The spleen cells from tumor regressors were not cytolytic when allowed to react in vitro with Mc12, Mc12-IL-2, or Mc12-CD80 target cells. However, when grown in IL-2-containing medium, splenocytes from tumor regressors, but not the splenocytes from tumor progressors, could develop cytolytic activity directed against Mc12 target cells that was comparable to that of the splenocytes from tumor-free controls. These results suggest that the rejection of tumors in nu/nu mice was mediated by IL-2-dependent mechanisms in which the CD80 molecule played a co-stimulatory role; the results also indicate that the ability to be activated by IL-2 and to give rise to cytolytic activity of nu/nu splenocytes from tumor progressors is decreased.

Animals↗

PubMedDate not supplied

Chemoimmunotherapy of cancer: potentiated effectiveness of granulocyte-macrophage colony-stimulating factor and ifosfamide derivative CBM-4A.

The effectiveness of combined chemoimmunotherapy with ifosfamide derivative CBM-4A and granulocyte-macrophage colony-stimulating factor (GM-CSF) was investigated in two experimental tumor models, 3MC-induced MHC class I+ sarcoma Mc12 and HPV16 E6/E7 oncogene-induced MHC class I- carcinoma MK16, transplanted in syngeneic mice. Treatment of Mc12 and MK16 tumor-bearing mice with GM-CSF or CBM-4A alone produced moderate anti-tumor effects. However, when the tumor-bearing mice were first treated i.p. with a single dose of CBM-4A (150 mg/kg) and three days later peritumorally with five daily doses of GM-CSF (100 ng/day), substantially stronger tumor-inhibitory effects were observed. The results indicate that in both, MHC class I+ and MHC class I- tumors, the combined chemoimmunotherapy can inhibit tumor progression more effectively than GM-CSF therapy or chemotherapy alone, and they suggest that GM-CSF should be considered as adjuvant to chemotherapy in clinical trials with HPV 16-associated neoplasms.

Animals↗

PubMedDate not supplied

Age-related decrease in transplantability of human tumours in nu/nu mice.

Experiments were designed to assess age-related changes in the transplantability of human tumours xenografted in congenitally athymic (nu/nu) mice. It has been found that the number of progressively growing human tumour xenografts decreased significantly with increasing age of BALB/c nu/nu recipients. These findings, taken together with a previously recognized increase in the frequency of endogenous interleukin 2 (IL-2)-producing cells with age of nu/nu mice, prompted us to investigate whether administration of exogenous IL-2 to young adult nu/nu mice could change the transplantability of human tumours in the mice. Peritumoral administration of exogenous interleukin 2 to 8-week-old nu/nu mice inhibited the growth of the human tumour xenografts. In vitro activation of nu/nu splenocytes with exogenous Il-2 resulted in the generation of killer cells which have been found to be cytolytic when allowed to react with human tumour targets in 51Cr cytotoxicity assay. In addition, it has been found that the percentage of IL-2-activated Thy 1.2+ and ASGM1+ cells substantially increased with increasing age of nu/nu spleen cell donors. These findings are compatible with the hypothesis that the observed age-related decrease in takes of human tumour xenografts might be determined by the increasing level of IL-2 production and subsequent maturation of IL-2-dependent effector cells.

Aging↗