Ex vivo isolation of RCC-reactive CD8+ CTL clones from HLA-identical allogeneic donor T cell lines stimulated by CD80-transfected tumor cells

Abstract

15625 Background: Regression of metastatic renal cell carcinoma (mRCC) is observed in a minority of patients treated by immunotherapies such as interleukin-2 (IL-2), interferon-a (IFN-a), or reduced-intensity allogeneic hematopoietic cell transplantation. However, the development of specific cellular immunotherapies for mRCC has been hindered by the lack of molecularly characterized T cell antigens with preferential expression on RCC cells. We have developed an ex vivo strategy for the isolation of RCC-reactive CD8+ CTL clones that may facilitate the identification of novel RCC-associated T cell antigens. Methods: RCC tumor lines were established from two patients with mRCC presenting to our institution for allogeneic HCT received from either an HLA-matched sibling or volunteer unrelated donor. Irradiated RCC tumor lines that were unmodified or transfected with a cDNA for human CD80 were used to stimulate responder CD8+ T cells isolated from pretransplant patient (autologous) or donor-derived (allogeneic) blood samples in mixed lymphocyte/tumor cell (MLTC) cultures supplemented with recombinant human IL-7 and IL-12 (stimulation #1) or IL-2 (2nd and subsequent stimulations). T cell lines with anti-tumor activity measured by IFN-γ ELISA were then cloned by limiting dilution. Results: After two or more in vitro stimulations, allogeneic CD8+ T cell lines stimulated by CD80- transfected RCC tumor cells, but not the other MLTC culture combinations tested demonstrated tumor-specific IFN-γ release. CD3+/CD8+/TCRaβ+ CTL clones with potent in vitro anti-tumor activity for unmodified RCC tumor were isolated from both sibling- and unrelated- donor derived T cell lines. Three such clones with unique specificities for allogeneic targets recognized the unmodified RCC tumor but not LCL or fibroblast target cells isolated from the same patient suggesting tumor-restricted expression of the target antigens. Conclusions: Ex vivo MLTC culture utilizing CD80-transfected RCC tumor and HLA- matched allogeneic responder CD8+ T cells warrants further study as a strategy to isolate CTL clones that may be used to identify novel RCC-associated T cell antigens. No significant financial relationships to disclose.