Histological analysis of lymphocyte subsets infiltrated into mouse tumor tissue exposed to local irradiation

Local radiation therapy of B16 melanoma tumors increases the generation of tumor antigen-specific effector cells that traffic to the tumor

Immunotherapy of cancer is attractive because of its potential for specificity and limited side effects. The efficacy of this approach may be improved by providing adjuvant signals and an inflammatory environment for immune cell activation. We evaluated antitumor immune responses in mice after treatment of OVA-expressing B16-F0 tumors with single (15 Gy) or fractionated (5 x 3 Gy) doses of localized ionizing radiation. Irradiated mice had cells with greater capability to present tumor Ags and specific T cells that secreted IFN-gamma upon peptide stimulation within tumor-draining lymph nodes than nonirradiated mice. Immune activation in tumor-draining lymph nodes correlated with an increase in the number of CD45(+) cells infiltrating single dose irradiated tumors compared with nonirradiated mice. Similarly, irradiated mice had increased numbers of tumor-infiltrating lymphocytes that secreted IFN-gamma and lysed tumor cell targets. Peptide-specific IFN-gamma responses were directed against both the class I and class II MHC-restricted OVA peptides OVA(257-264) and OVA(323-339), respectively, as well as the endogenous class I MHC-restricted B16 tumor peptide tyrosinase-related protein 2(180-188). Adoptive transfer studies indicated that the increased numbers of tumor Ag-specific immune cells within irradiated tumors were most likely due to enhanced trafficking of these cells to the tumor site. Together these results suggest that localized radiation can increase both the generation of antitumor immune effector cells and their trafficking to the tumor site.

Changes of lymphocyte subsets after local irradiation for early stage breast cancer and seminoma testis: long-term increase of activated (HLA-DR+) T cells and decrease of "naive" (CD4-CD45R) T lymphocytes

Blood lymphocyte subsets of early breast cancer patients and of men with stage I seminoma of the testis were studied up to 6 years after radiotherapy. Similar results were obtained in the two patient groups. After a temporary decrease, the CD4-w29 or "memory" T cells recovered completely, while the CD4-45R or "naive" T cells remained decreased up to 6 years after irradiation. The number of CD8 T lymphocytes did not change during or after treatment. Because of the decrease of a subset of CD4 cells, and the unchanged values of CD8 cells, the CD4/CD8 ratio decreased significantly after irradiation, and remained lower than before treatment up to 5-6 years after radiotherapy. The number of both HLA-DR positive CD4 and HLA-DR positive CD8 T cells ("activated" T cells) increased significantly after irradiation. The natural killer (NK) cells were not affected by treatment. We propose that the recovery of the CD4 cells is limited to the CD4-w29 ("memory") population because of thymic dysfunction in older humans. The impact of the observed immune modulation on the low susceptibility for infections after local irradiation, and on putative antitumour immune responses is discussed.

Combination therapy of pions and SPG (Sonifilan, Schizophyllan), a biological response modifier for mouse tumor systems

Female C3H mice aged 8-10 weeks with transplanted KHT sarcoma or SCCVII tumor were used to investigate the antitumor effect of SPG (Sonifilan, Schizophyllan) alone and in combination with local irradiation of pions with 4 fractions of 400 cGy (total 1600 cGy). Daily doses of 10 mg/kg of SPG were given intramuscularly to the mice bearing KHT sarcoma for 14 consecutive days from day 7, and to mice bearing SCCVII tumor for 20 consecutive days from day 7 and thereafter three times a week for another 2 weeks. The antitumor effect was evaluated by the changes in tumor volume, survival curves, and the number of pulmonary metastatic nodules on the surface of the lungs. SPG failed to exert any antitumor effect and any life-prolonging effect for the KHT sarcoma. As for SCCVII tumor, in the group treated with pions and SPG, tumor growth decreased significantly (p less than 0.01) compared with the group treated with pion only, and life prolonging effect and metastasis-suppressing effect were also observed (p less than 0.04). In conditions of minimal residual disease brought about by pion irradiation, the adjuvant effect of a Biological Response Modifier (BRM) SPG may prove to be a promising method of cancer therapy for some tumors.