Harrington, Kevin J.

Abstract Tumor cells are able to evade cytotoxic therapies through the accumulation of genomic mutations and rapid evolution. In the case of oncolytic virotherapy, understanding the mechanisms by which cancer cells develop resistance to infection and lysis is critical to the development of more effective viral-based platforms. Here, we identify APOBEC3 as an important factor involved in the restriction of vesicular stomatitis virus (VSV). We show that VSV infection of B16 murine melanoma cells upregulated APOBEC3 in an IFNβ-dependent manner, which was responsible for the evolution of virus-resistanT-cell populations and suggested that APOBEC3 expression promoted the acquisition of a virus-resistant phenotype. ShRNA knockdown of APOBEC3 in B16 cells diminished their capacity to develop resistance to VSV infection in vitro, and enhanced the therapeutic effect of VSV in vivo. Similarly, overexpression of human APOBEC3B promoted the acquisition of resistance to oncolytic VSV in murine melanoma and glioblastoma lines, as well as in a human melanoma cell line in vitro and in vivo. Finally, we demonstrate that progeny virus obtained after passage through APOBEC3B overexpressing cells contained more defective interfering particles, thereby indicating that APOBEC3B directly affected the fitness of VSV, an RNA virus that has not previously been identified to be restricted by APOBEC3B. This research identifies APOBEC3 enzymes as key players to target in order to improve the efficacy of oncolytic viruses as well as broader nucleic acid-based therapeutic platforms. Citation Format: Amanda L. Huff, Phonphimon Wongthida, Timothy Kottke, Jill Thompson, Christopher B. Driscoll, Matthew Schuelke, Kevin G. Shim, Reuben S. Harris, Amy Molan, Jose S. Pulido, Peter J. Selby, Kevin J. Harrington, Alan Melcher, Laura Evgin, Richard Vile. APOBEC3 confers resistance to oncolytic VSV therapy [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr A133.

Vascular protection using gene therapy can reduce the late toxicities of radiotherapy.

Intravenous infusion of oncolytic reovirus in patients leads to infection of brain tumors, infiltration by cytotoxic T cells, and up-regulation of PD-L1.

AbstractUnderstanding how incompletely cleared primary tumors transition from minimal residual disease (MRD) into treatment-resistant, immune-invisible recurrences has major clinical significance. We show here that this transition is mediated through the subversion of two key elements of innate immunosurveillance. In the first, the role of TNFα changes from an antitumor effector against primary tumors into a growth promoter for MRD. Second, whereas primary tumors induced a natural killer (NK)–mediated cytokine response characterized by low IL6 and elevated IFNγ, PD-L1hi MRD cells promoted the secretion of IL6 but minimal IFNγ, inhibiting both NK-cell and T-cell surveillance. Tumor recurrence was promoted by trauma- or infection-like stimuli inducing VEGF and TNFα, which stimulated the growth of MRD tumors. Finally, therapies that blocked PD-1, TNFα, or NK cells delayed or prevented recurrence. These data show how innate immunosurveillance mechanisms, which control infection and growth of primary tumors, are exploited by recurrent, competent tumors and identify therapeutic targets in patients with MRD known to be at high risk of relapse. Cancer Immunol Res; 5(11); 1029–45. ©2017 AACR.

Objective Oncolytic viruses (OVs) represent promising, proinflammatory cancer treatments. Here, we explored whether OV-induced innate immune responses could simultaneously inhibit HCV while suppressing hepatocellular carcinoma (HCC). Furthermore, we extended this exemplar to other models of virus-associated cancer. Design and results Clinical grade oncolytic orthoreovirus (Reo) elicited innate immune activation within primary human liver tissue in the absence of cytotoxicity and independently of viral genome replication. As well as achieving therapy in preclinical models of HCC through the activation of innate degranulating immune cells, Reo-induced cytokine responses efficiently suppressed HCV replication both in vitro and in vivo. Furthermore, Reo-induced innate responses were also effective against models of HBV-associated HCC, as well as an alternative endogenous model of Epstein–Barr virus-associated lymphoma. Interestingly, Reo appeared superior to the majority of OVs in its ability to elicit innate inflammatory responses from primary liver tissue. Conclusions We propose that Reo and other select proinflammatory OV may be used in the treatment of multiple cancers associated with oncogenic virus infections, simultaneously reducing both virus-associated oncogenic drive and tumour burden. In the case of HCV-associated HCC (HCV-HCC), Reo should be considered as an alternative agent to supplement and support current HCV-HCC therapies, particularly in those countries where access to new HCV antiviral treatments may be limited.

Abstract We have developed the use of reovirus as a systemically delivered oncolytic agent in both pre-clinical models and in Phase I and II clinical trials. Reovirus has direct oncolytic activity against many human/murine tumor cells, partly because of disruption of the PKR-mediated anti-viral response in malignant cells. In addition however, we have shown that anti-tumor therapy is directly associated with immune activation by virus replication in tumors. The immune mechanisms of therapy include both innate immune activation against virally infected tumor cells, as well as the generation of adaptive anti tumor immune responses as a result of in vivo priming against tumor associated antigens released during that killing. Therefore, to exploit the immune components of reovirus anti-tumor therapy, we tested the combination of oncolytic therapy with systemic checkpoint inhibition. To do this, we used our murine, immune-competent, model and a protocol in which injection of reovirus into subcutaneous (s.c.) B16 melanomas generates moderate therapy following intra-tumoral injection of reovirus into 5d established subcutaneous B16 melanomas growing in C57Bl/6 mice. In this model, provision of systemic anti-PD-1 antibody along with i.t. reovirus, significantly enhanced survival compared to i.t. reovirus alone (p<0.01) and led to >40% of mice being cured long term. Immune analysis suggests that the enhanced therapeutic benefit of reovirus plus checkpoint inhibition is contributed by at least two factors. Thus, blockade of PD-1 significantly enhanced the ability of NK cells to recognize (TNF-α secretion), and kill, reovirus-infected target tumor cells. Second, antiPD-1 antibody led to a significant reduction in Treg activity in reovirus-treated mice, with the overall effect of increasing the adaptive CD8+ anti tumor T cell response. We also showed that timing of the checkpoint inhibitor antibody was significant in balancing toxicity with anti tumor therapy. These data suggest that combination of checkpoint inhibition therapy with reovirus oncolytic/immunotherapy represents a readily translatable method to enhance the therapeutic value of either alone. Citation Format: Shane Zaidi, Kevin Shim, Karishma Rajani, Rosa Diaz, Elizabeth Ilett, Timothy Kottke, Jill Thompson, Peter Selby, Kevin Harrington, Hardev Pandha, Alan Melcher, Matt Coffey, Richard Vile. Combination therapy of reovirus and checkpoint inhibition. [abstract]. In: Proceedings of the AACR Special Conference: Tumor Immunology and Immunotherapy: A New Chapter; December 1-4, 2014; Orlando, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2015;3(10 Suppl):Abstract nr B88.

Abstract We have developed the use of reovirus as a systemically delivered oncolytic agent in both pre-clinical models and in early Phase clinical trials. Reovirus has direct oncolytic activity against many human/murine tumor cells, partly because of disruption of the PKR-mediated anti-viral response in malignant cells. In addition however, we have shown that anti-tumor therapy is directly associated with immune activation by virus replication in tumors. The immune mechanisms of therapy include both innate immune activation against virally infected tumor cells, as well as the generation of adaptive anti tumor immune responses as a result of in vivo priming against tumor associated antigens released during that killing. Therefore, to exploit the immune components of reovirus anti-tumor therapy, we hypothesized that the combination of reovirus therapy with systemic checkpoint inhibition would augment therapeutic efficacy. To test the hypothesis, we used C57Bl/6 mice, an immune-competent murine model, with established subcutaneous (s.c.) B16 melanomas. In this model, intra-tumoral injection of reovirus into s.c. tumors generated moderate therapy. Provision of systemic anti-PD-1 antibody along with i.t. reovirus, significantly enhanced survival compared to i.t. reovirus alone (p<0.01) and led to >40% of mice being cured long term. Immune analysis suggested that the enhanced therapeutic benefit of reovirus plus checkpoint inhibition is contributed by at least two factors. First, blockade of PD-1 significantly enhanced the ability of NK cells to recognize (TNF-α secretion), and kill, reovirus-infected target tumor cells. Second, anti PD-1 antibody led to a significant reduction in Treg activity in reovirus-treated mice, with the overall effect of increasing the adaptive CD8+ anti-tumor T cell response. Furthermore, in vivo depletion studies demonstrated that NK cells had a dramatic effect in reducing the therapeutic efficacy of reovirus plus anti-PD-1 therapy. Overall, the results indicate that combination therapy of reovirus with PD-1 blockade confers significant survival benefit, by augmenting tumor-specific NK responses and specifically attenuating tumor-specific immunosuppression. These data also suggest that combination of PD-1 inhibition therapy with reovirus oncolytic/immunotherapy represents a readily translatable method to enhance the therapeutic efficacy. Citation Format: Karishma Rajani, Christopher Parrish, Kevin Shim, Liz Ilett, Fiona Errington-Mais, Jill Thompson, Tim Kottke, Rosa Maria-Diaz, Peter Selby, Hardev Pandha, Kevin Harrington, Alan Melcher, Matt Coffey, Shane Zaidi, Richard Vile. Combination therapy of reovirus and PD-1 blockade effectively establishes tumor control via innate and adaptive immune responses. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1360. doi:10.1158/1538-7445.AM2015-1360

Abstract Purpose: Reovirus is a wild-type oncolytic virus that is ubiquitous in the environment; most patients are therefore preimmune. Therapeutic administration leads to an increase in neutralizing antireovirus antibody (NARA) titer. We hypothesized that if NARA limited reovirus antitumor activity, the effect might be attenuated by coadministration of cyclophosphamide. Experimental design: In a phase I study, patients with advanced cancer received cyclophosphamide 3 days before intravenous reovirus serotype 3 Dearing (RT3D). The primary objective was to reduce the resulting rise in NARA titer. Cyclophosphamide dose was escalated from 25–1,000 mg/m2 through nine cohorts; we aimed to define a well-tolerated immunomodulatory dose. Results: The combination was well tolerated in 36 patients, with grade 3/4 toxicities only seen at or above the maximum tolerated dose of cyclophosphamide, which was 800 mg/m2 combined with reovirus. Immunosuppressive effect, defined as maintaining NARA titer rise below a predefined threshold, was observed in only one patient. Furthermore, despite expected myelosuppression seen at higher cyclophosphamide doses, no changes in T-cell subsets, including Tregs, occurred with dose escalation. Viable virus was detected in association with peripheral blood mononuclear cells (PBMC) from 14% of patients 10 days after the last RT3D injection, despite high plasma NARA titer, demonstrating a potential mechanism for prolonged evasion of neutralization by reovirus. Conclusions: Coadministration of cyclophosphamide with reovirus is safe, but does not attenuate host antiviral responses. Alternative immunomodulation approaches should be explored, but association with PBMCs may allow reovirus to persist and evade even high levels of neutralizing antibodies. Clin Cancer Res; 21(6); 1305–12. ©2014 AACR.