Citations

Abstract Strategies that generate tumor Ag-specific effector cells do not necessarily cure established tumors. We hypothesized that the relative efficiency with which tumor-specific effector cells reach the tumor is critical for therapy. We demonstrate in this study that activated T cells respond to the chemokine CCL3, both in vitro and in vivo, and we further demonstrate that expression of CCL3 within tumors increases the effector T cell infiltrate in those tumors. Importantly, we show that adenoviral gene transfer to cause expression of CCL3 within B16ova tumors in vivo increases the efficacy of adoptive transfer of tumor-specific effector OT1 T cells. We additionally demonstrate that such therapies result in endogenous immune responses to tumor Ags that are capable of protecting animals against subsequent tumor challenge. Strategies that modify the “visibility” of tumors have the potential to significantly enhance the efficacy of both vaccine and adoptive transfer therapies currently in development.

Abstract Previously, we showed that nine intradermal injections of a plasmid in which the HSVtk suicide gene is expressed from a melanocyte-specific promoter (Tyr-HSVtk), combined with a plasmid expressing heat shock protein 70 (CMV-hsp70), along with systemic ganciclovir, kills normal melanocytes and raises a CD8+ T cell response that is potent enough to eradicate small, 3-day established B16 tumors. We show in this study that, in that regimen, hsp70 acts as a potent immune adjuvant through TLR-4 signaling and local induction of TNF-α. hsp70 is required for migration of APC resident in the skin to the draining lymph nodes to present Ags, derived from the killing of normal melanocytes, to naive T cells. The addition of a plasmid expressing CD40L increased therapeutic efficacy, such that only six plasmid injections were now required to cure large, 9-day established tumors. Generation of potent immunological memory against rechallenge in cured mice accompanied these therapeutic gains, as did induction of aggressive autoimmune symptoms. Expression of CD40L, along with hsp70, increased both the frequency and activity of T cells activated against melanocyte-derived Ags. In this way, addition of CD40L to the hsp70-induced inflammatory killing of melanocytes can be used to cure large established tumors and to confer immunological memory against tumor cells, although a concomitant increase in autoimmune sequelae also is produced.

Abstract Oncolytic virotherapy offers the potential to treat tumors both as a single agent and in combination with traditional modalities such as chemotherapy and radiotherapy. Here we describe an effective, fully systemic treatment regimen, which combines virotherapy, acting essentially as an adjuvant immunotherapy, with adoptive cell transfer (ACT). The combination of ACT with systemic administration of a vesicular stomatitis virus (VSV) engineered to express the endogenous melanocyte antigen glycoprotein 100 (gp100) resulted in regression of established melanomas and generation of antitumor immunity. Tumor response was associated with in vivo T-cell persistence and activation as well as treatment-related vitiligo. However, in a proportion of treated mice, initial tumor regressions were followed by recurrences. Therapy was further enhanced by targeting an additional tumor antigen with the VSV-antigen + ACT combination strategy, leading to sustained response in 100% of mice. Together, our findings suggest that systemic virotherapy combined with antigen-expressing VSV could be used to support and enhance clinical immunotherapy protocols with adoptive T-cell transfer, which are already used in the clinic. Cancer Res; 72(18); 4753–64. ©2012 AACR.

An antitumor T-cell response can lead to tumor control without clearing all tumor cells. As long as residual tumor cells remain, there is a constant risk of escape from that T-cell response. We previously showed that adoptive transfer of anti-ova OT-I T cells into B16ova-bearing mice led to tumor regression followed by escape of tumors that had lost the ova gene, rendering the OT-I T cells ineffective. In this study, we hypothesized that simultaneous transfer of cytotoxic T lymphocytes targeted against two independent antigens would reduce selection for single-antigen-loss cells, thereby limiting tumor escape. Using OT-I and Pmel T cells to treat B16ova tumors, we found that early cotransfer could prevent tumor emergence in most mice, whereas neither T-cell specificity alone was able to do so. When combined with total body irradiation for the treatment of larger 7-day tumors, cotransfer was also better at limiting tumor recurrence, and the tumors that did escape combination therapy continued to express both target antigens. As adoptively transferred T cells also persisted in vivo , even in mice with recurrent tumors, we hypothesized that restimulation of these antitumor T cells would prolong survival of mice with recurrent tumors. Consistent with this hypothesis, administration of a low-dose regimen of cyclophosphamide following tumor escape slowed tumor growth in mice that had previously received T-cell therapy, but not in control-treated mice, an effect that was associated with increased activation of T cells in vitro by low- but not high-dose cyclophosphamide.

Abstract Innate immune effector mechanisms triggered by oncolytic viruses may contribute to the clearance of both infected and uninfected tumor cells in immunocompetent murine hosts. Here, we developed an in vitro tumor cell/bone marrow coculture assay and used it to dissect innate immune sensor and effector responses to intratumoral vesicular stomatitis virus (VSV). We found that the type III IFN interleukin-28 (IL-28) was induced by viral activation of innate immune-sensing cells, acting as a key mediator of VSV-mediated virotherapy of B16ova melanomas. Using tumor variants which differentially express the IL-28 receptor, we showed that IL-28 induced by VSV within the tumor microenvironment sensitizes tumor cells to natural killer cell recognition and activation. These results revealed new insights into the immunovirological mechanisms associated with oncolytic virotherapy in immune-competent hosts. Moreover, they defined a new class of tumor-associated mutation, such as acquired loss of responsiveness to IL-28 signaling, which confers insensitivity to oncolytic virotherapy through a mechanism independent of viral replication in vitro. Lastly, the findings suggested new strategies to manipulate immune signals that may enhance viral replication, along with antitumor immune activation, and improve the efficacy of oncolytic virotherapies. Cancer Res; 70(11); 4539–49. ©2010 AACR.

Abstract Our preclinical and clinical trials using a replication-defective adenoviral vector expressing IFN-β have shown promising results for the treatment of malignant mesothelioma. Based on the hypotheses that a replication-competent vesicular stomatitis virus (VSV) oncolytic vector would transduce more tumor cells in vivo, that coexpression of the immunostimulatory IFN-β gene would enhance the immune-based effector mechanisms associated both with regression of mesotheliomas and with VSV-mediated virotherapy, and that virus-derived IFN-β would add further safety to the VSV platform, we tested the use of IFN-β as a therapeutic transgene expressed from VSV as a novel treatment for mesothelioma. VSV-IFN-β showed significant therapy against AB12 murine mesotheliomas in the context of both local and locoregional viral delivery. Biologically active IFN-β expressed from VSV added significantly to therapy compared with VSV alone, dependent in part on host CD8+ T-cell responses. Immune monitoring suggested that these antitumor T-cell responses may be due to a generalized T-cell activation rather than the priming of tumor antigen–specific T-cell responses. Finally, IFN-β also added considerable extra safety to the virus by providing protection from off-target viral replication in nontumor tissues and protected severe combined immunodeficient mice from developing lethal neurotoxicity. The enhanced therapeutic index provided by the addition of IFN-β to VSV therefore provides a powerful justification for the development of this virus for future clinical trials. [Cancer Res 2009;69(19):7713–20]

Abstract We have a long-term interest in the connectivity between autoimmunity and tumor rejection. However, outside of the melanocyte/melanoma paradigm, little is known about whether autoimmune responses to normal tissue can induce rejection of tumors of the same histologic type. Here, we induced direct, pathogen-like cytotoxicity to the normal pancreas in association with the immune adjuvant heat shock protein 70. In sharp contrast to our studies with a similar approach for the treatment of prostate cancer, inflammatory killing of the normal pancreas induced a Th1-like, anti-self-response to pancreatic antigens, which was rapidly suppressed by a concomitant suppressive regulatory T cell (Treg) response. Interestingly, even when Treg cells were depleted, the Th1-like response was insufficient to induce significant ongoing autoimmunity. However, the Th1-like response to antigens expressed in the pancreas at the time of damage was sufficient to induce rejection of tumors expressing either a foreign (ova) antigen or fully syngeneic tumor antigens (on Panc02 tumor cells), provided that Treg were depleted before inflammatory killing of the normal pancreas. Taken together, these data indicate that profound differences exist between the immunoprotective mechanisms in place between different tissues (pancreas and prostate) in their response to pathogen-like damage. Moreover, they also show that, although multiple layers of immunologic safeguards are in place to prevent the development of severe autoimmune consequences in the pancreas (in contrast to the prostate), tumor rejection responses can still be decoupled from pathologic autoimmune responses in vivo, which may provide novel insights into the immunotherapeutic treatment of pancreatic cancer. [Cancer Res 2009;69(19):7767–74]