Tumor-Specific CD8+ T Cells Expressing Interleukin-12 Eradicate Established Cancers in Lymphodepleted Hosts

Abstract

T-cell-based immunotherapies can be effective in the treatment of large vascularized tumors, but they rely on adoptive transfer of substantial numbers (∼20 million) of tumor-specific T cells administered together with vaccination and high-dose interleukin (IL)-2. In this study, we report that ∼10,000 T cells gene-engineered to express a single-chain IL-12 molecule can be therapeutically effective against established tumors in the absence of exogenous IL-2 and vaccine. Although IL-12-engineered cells did not perist long-term in hosts, they exhibited enhanced functionality and were detected in higher numbers intratumorally along with increased numbers of endogenous natural killer and CD8 + T cells just before regression. Importantly, transferred T cells isolated from tumors stably overproduced supraphysiologic amounts of IL-12, and the therapeutic effect of IL-12 produced within the tumor microenvironment could not be mimicked with high doses of exogenously provided IL-12. Furthermore, antitumor effects could be recapitulated by engineering wild-type open-repertoire splenocytes to express both the single-chain IL-12 and a recombinant tumor-specific T-cell receptor (TCR), but only when individual cells expressed both the TCR and IL-12, indicating that arrested migration of T cells at the tumor site was required for their activities. Successful tumor eradication was dependent on a lymphodepleting preconditioning regimen that reduced the number of intratumoral CD4 + Foxp3 + T regulatory cells.Our findings reveal an approach to genetically modify T cells to reduce the cell number needed, eliminate the need for vaccines or systemic IL-2, and improve immunotherapy efficacy based on adoptive transfer of gene-engineered T cells.

miR-155 augments CD8 + T-cell antitumor activity in lymphoreplete hosts by enhancing responsiveness to homeostatic γ c cytokines

“…However, it is unclear whether such approaches can replace both lymphodepletion and cytokine support. For instance, overexpression of IL-12 in pmel-1 cells could not substitute the requirement for lymphodepletion in this model of T-cell therapy (34). Here, we demonstrate that total body irradiation preconditioning or high-doses of exogenous cytokines could not increase the treatment efficacy of miR-155 cells, indicating that overexpression of miR-155 is sufficient in surrogating the therapeutic advantages conveyed by these regimens.…”

Dihydrofolate Reductase and Thymidylate Synthase Transgenes Resistant to Methotrexate Interact to Permit Novel Transgene Regulation

“…IL-12 is such a transgene. IL-12 is a cytokine capable of inducing a strong immune response against tumor from tumor-specific T cells (25). However, systemic IL-12 is highly toxic and hence of low efficacy (26).…”

Tumor-targeted T cells modified to secrete IL-12 eradicate systemic tumors without need for prior conditioning

“…Interestingly, this finding may also reconcile our results compared with previously published studies wherein infusion with IL-12-secreting tumor-targeted CD8 ϩ T cells alone still required prior conditioning to achieve optimal antitumor efficacy. 35 In these studies, the authors proposed that conditioning therapy retained relevance because of continued dependence on depletion of endogenous lymphocyte "cytokine sinks" and Tregs, which have been previously demonstrated to suppress the function of CAR-modified T cells. 17 However, the lack of targeted CD4 ϩ IL-12-secreting T cells in these latter studies may be an alternative explanation for these conflicting results.…”