New strategy of cancer immunotherapy: irradiation or chemotherapeutics-induced lymphopenia combined with immune reconstitution and tumor vaccine / 中华肿瘤杂志

ABSTRACT

<p><b>OBJECTIVE</b>To test whether vaccination performed during irradiation or chemotherapeutics-induced lymphopenia-driven T cell proliferation could augment the antitumor immunity.</p><p><b>METHODS</b>The study composed of two parts, investigating the anti-tumor efficacy of performing tumor vaccination during early immune reconstitution period following sublethal total body irradiation and cyclophosphamide (Cy)-induced lymphopenia, respectively. Mice were subsequently reconstituted with naïve splenocytes from syngeneic mice and were named RLM (Reconstituted lymphopenic mice). Immunization/vaccination (F10) and adoptive immunotherapy (D5-G6) were used to explore anti-tumor immune responses in vaccinated irradiation/RLM and vaccinated Cy/RLM, respectively. Both normal C57BL/6 mice and RLM were vaccinated with irradiated, weakly immunogenic F10 melanoma cells and subsequently challenged with F10 cells. In addition, to determine the role of CD4(+) and CD8(+) T cells in the protective anti-tumor immune response, irradiation/RLM were depleted of these subpopulations by administration of the appropriate mAb around challenge. In the second part, adoptive immunotherapy was used to evaluate the anti-tumor immune responses under chemotherapeutics-induced lymphopenic condition. Both normal mice and RLM (Cy-treated) were vaccinated with GM-CSF-modified D5 melanoma cells (D5-G6) and tumor vaccine draining lymph nodes (TVDLN) were harvested 9-10 days later. Effector T cells were generated in vitro from TVDLN cells and adoptively transferred to mice bearing 3-day pre-established pulmonary metastases (D5). Recipient mice were sacrificed 2 weeks later after tumor inoculation and pulmonary metastases were enumerated.</p><p><b>RESULTS</b>Significantly greater protection was induced in vaccinated irradiation/RLM, compared to vaccinated normal mice (63.2% vs 16.7%). Protective immunity in RLM depended on CD8(+) T cells. Increase in the interval between reconstitution and vaccination significantly decrease the protection. Effector T cells generated from vaccinated Cy-treated RLM demonstrated significantly higher in vivo anti-tumor efficacy over those of vaccinated normal mice.</p><p><b>CONCLUSION</b>This study suggests that vaccination of RLM could elicit augmented antitumor immunity compared to normal hosts, highlighting the potential clinical benefit of performing tumor vaccination during irradiation or chemotherapeutics-induced lymphopenia in cancer patients.</p>