Therapeutic Effectiveness of Adaptive T-Cell Transfer for Minimal Residual Mantle Cell Lymphoma Following High Dose Therapy.

Mantle cell lymphoma (MCL) is the most aggressive B-cell malignancy with an overall survival of less than four years. Although high-dose therapy followed by stem cell transplantation is effective in reducing the tumor burden and increasing the survival, the patients eventually relapse due to residual lymphoma. Therefore effective therapeutic modalities are needed to target residual MCL. In this study we have developed an immune-based approach to treat minimal residual MCL. HLA matched normal donor mononuclear cells were used to generate dendric cells in vitro. Following characterization, the dendritic cells were fused with the MCL cell line Granta 519 cells to create DC/MCL hybrids. The hybrids were then used to stimulate T cells from the same donor to generate MCL-specific cytotoxic T lymphocytes (CTL). The CTLs were tested for their MCL-specific cytotoxic abilities in vitro against MCL target cells and compared to control T cells or DC primed with MCL lysate or DCs transfected with MCL RNA. HLA matched human breast cancer cell line MDA-231 was used as an irrelevant tumor target. The in vitro results showed the highest MCL specific cytotoxic effects of CTLs generated using DC-MCL hybrids for immunostimulation. As a logical next step, in vivo therapeutic affects the MCL-specific CTLs were tested using a preclinical animal model. Four groups of NOD-SCID mice, with a minimum 10 mice per group, were transplanted with Grant-519 human MCL cell line intravenously. MCL bearing mice were treated with combination chemotherapy (CHOP)over three days followed by transplantation of 1 ×10⁶ mononuclear cells. Ten days after, mice were transplanted with 3 ×10⁶ adoptive T cells weekly for four weeks. The results of the in vivo studies showed that, adoptively transferred T cells that had been stimulated with DC/MCL hybrids were able to significantly inhibit tumor growth in the liver (p = 0.005), kidneys (p = 0.001), and lungs (p= 0.001) of mice with minimal residual MCL compared to control tumor bearing animals as determined by analyzing tumor burden in the organs using virtual images and Neuroinformatica software. When combined with CHOP chemotherapy, adoptively transferred T cells were able to significantly (P = 0.001) extend the survival of the mice by significantly further reducing the tumor burden as compared to mice only receiving the chemotherapy plus unmanipulated T cells. Specificity of the CTL mediated response was also confirmed by cytokine profiling in vitro and in vivo. In summary, we have clearly shown that antigen-primed DCs can be used to activate MCL-specific T cells which, when administered adoptively, are effective in treating minimal residual MCL. Thus these studies lay foundation for a PhaseI/II clinical trial.

(This study was supported by the Lymphoma Research Foundation, New York, NY).