Developing combinatorial approaches for durable cancer treatment

Objectives: Considerable effort has been extended in testing vaccine platforms in clinical trials. However, the combination of vaccines with traditional modalities like chemotherapy remains largely untested. We show that by monitoring chemotherapy-induced hematopoietic reconstitution kinetics, we were able to time vaccine administration after chemotherapy to optimize its combinatorial efficacy in a murine model.Methods: BL6 mice were given paclitaxel (TAX), and blood samples drawn and analyzed to monitor for lymphopenia and reconstitution thereof. After establishing the nadir, we administered tumor subcutaneously (EG6 thymoma over the right hindquarter for ease of measurement and fast growth) and devised a treatment strategy of TAX with or without MIS-OVA vaccine, administered at different points along the cycle of lymphocyte nadir and reconstitution. Therefore, the mice were given MIS-OVA, and naïve OT-1 cells were adoptively transferred to provide a means to monitor for T-cell activation and proliferation. They were then split into 3 groups and given the vaccine on day 0, day 7 (during nadir), or day 14 (during reconstitution). The mice were observed for treatment response measurable with tumor size. After establishing the optimal timing, we tested MIS alone versus TAX alone versus MIS + TAX administered at time 0 to tumor-bearing mice to accurately conclude that the effect of tumor shrinkage was because of the vaccination/timing in concert with the TAX, and not any one factor alone.Results: Flow cytometric analysis of splenic and lymphatic tissue demonstrated significant activation and memory responses. Much higher expansion and activation was noted in the day 0 and day 14 groups, particularly in the day 0 group, with 569,174 activated OT-1 cells recovered versus less than 200,000 from groups B and C mice when analyzing the spleen. Similar effect was noted in the lymph nodes, with 138,825 cells elicited on day 0, 13,964 cells on day 7, and 106,584 total OT-1 cells on day 14. Furthermore, 4 of 5 mice given MIS + TAX were NED 21 days after TAX administration, whereas the other populations had multiple deaths and heavy tumor burden.Conclusions: The keystone to tumor-specific immunologic treatment will be establishing benchmarks such as vaccination schedules in concert with current adjuvant chemotherapy. Given the strong evidence of memory and activation in group A, and the ease of clinical application, a phase I human clinical trial is both feasible and easy to implement in current clinical models. Objectives: Considerable effort has been extended in testing vaccine platforms in clinical trials. However, the combination of vaccines with traditional modalities like chemotherapy remains largely untested. We show that by monitoring chemotherapy-induced hematopoietic reconstitution kinetics, we were able to time vaccine administration after chemotherapy to optimize its combinatorial efficacy in a murine model. Methods: BL6 mice were given paclitaxel (TAX), and blood samples drawn and analyzed to monitor for lymphopenia and reconstitution thereof. After establishing the nadir, we administered tumor subcutaneously (EG6 thymoma over the right hindquarter for ease of measurement and fast growth) and devised a treatment strategy of TAX with or without MIS-OVA vaccine, administered at different points along the cycle of lymphocyte nadir and reconstitution. Therefore, the mice were given MIS-OVA, and naïve OT-1 cells were adoptively transferred to provide a means to monitor for T-cell activation and proliferation. They were then split into 3 groups and given the vaccine on day 0, day 7 (during nadir), or day 14 (during reconstitution). The mice were observed for treatment response measurable with tumor size. After establishing the optimal timing, we tested MIS alone versus TAX alone versus MIS + TAX administered at time 0 to tumor-bearing mice to accurately conclude that the effect of tumor shrinkage was because of the vaccination/timing in concert with the TAX, and not any one factor alone. Results: Flow cytometric analysis of splenic and lymphatic tissue demonstrated significant activation and memory responses. Much higher expansion and activation was noted in the day 0 and day 14 groups, particularly in the day 0 group, with 569,174 activated OT-1 cells recovered versus less than 200,000 from groups B and C mice when analyzing the spleen. Similar effect was noted in the lymph nodes, with 138,825 cells elicited on day 0, 13,964 cells on day 7, and 106,584 total OT-1 cells on day 14. Furthermore, 4 of 5 mice given MIS + TAX were NED 21 days after TAX administration, whereas the other populations had multiple deaths and heavy tumor burden. Conclusions: The keystone to tumor-specific immunologic treatment will be establishing benchmarks such as vaccination schedules in concert with current adjuvant chemotherapy. Given the strong evidence of memory and activation in group A, and the ease of clinical application, a phase I human clinical trial is both feasible and easy to implement in current clinical models.