Enhanced IL-12 transgene expression improves oncolytic viroimmunotherapy.

Introduction: Malignant peripheral nerve sheath tumors (MPNSTs) are aggressive sarcomas with unacceptably low cure rates occurring often in patients with neurofibromatosis 1 defects. To investigate oncolytic Herpes Simplex Virus (oHSV) as an immunotherapeutic approach, we compared viral replication, functional activity, and immune response between unarmed and interleukin 12 (IL-12)-armed oncolytic viruses in virus-permissive (B109) and -resistant (67C-4) murine MPNSTs. Methods: This study compared two attenuated IL-12-oHSVs with γ134.5 gene deletions (Δγ134.5) and the same transgene expression cassette. The primary difference in the IL-12-oHSVs was in their ability to counter the translational arrest response in infected cells. Unlike M002 (Δγ134.5, mIL-12), C002 (Δγ134.5, mIL-12, IRS1) expresses an HCMV IRS1 gene and evades dsRNA activated translational arrest in infected cells. Results and discussion: Our results show that oHSV replication and gene expression results in vitro were not predictive of oHSV direct oncolytic activity in vivo. Tumors that supported viral replication in cell culture studies resisted viral replication by both oHSVs and restricted M002 transgene expression in vivo. Furthermore, two IL-12-oHSVs with equivalent transcriptional activity differed in IL-12 protein production in vivo, and the differences in IL-12 protein levels were reflected in immune infiltrate activity changes as well as tumor growth suppression differences between the IL-12-oHSVs. C002-treated tumors exhibited sustained IL-12 production with improved dendritic cells, monocyte-macrophage activity (MHCII, CD80/CD86 upregulation) and a polyfunctional Th1-cell response in the tumor infiltrates. Conclusion: These results suggest that transgene protein production differences between oHSVs in vivo, in addition to replication differences, can impact OV-therapeutic activity.

Understanding and therapeutically exploiting cGAS/STING signaling in glioblastoma.

Since the discovery that cGAS/STING recognizes endogenous DNA released from dying cancer cells and induces type I interferon and antitumor T cell responses, efforts to understand and therapeutically target the STING pathway in cancer have ensued. Relative to other cancer types, the glioma immune microenvironment harbors few infiltrating T cells, but abundant tumor-associated myeloid cells, possibly explaining disappointing responses to immune checkpoint blockade therapies in cohorts of patients with glioblastoma. Notably, unlike most extracranial tumors, STING expression is absent in the malignant compartment of gliomas, likely due to methylation of the STING promoter. Nonetheless, several preclinical studies suggest that inducing cGAS/STING signaling in the glioma immune microenvironment could be therapeutically beneficial, and cGAS/STING signaling has been shown to mediate inflammatory and antitumor effects of other modalities either in use or being developed for glioblastoma therapy, including radiation, tumor-treating fields, and oncolytic virotherapy. In this Review, we discuss cGAS/STING signaling in gliomas, its implications for glioma immunobiology, compartment-specific roles for STING signaling in influencing immune surveillance, and efforts to target STING signaling - either directly or indirectly - for antiglioma therapy.

[89Zr]-CD8 ImmunoPET imaging of glioblastoma multiforme response to combination oncolytic viral and checkpoint inhibitor immunotherapy reveals CD8 infiltration differential changes in preclinical models.

Rationale: Novel immune-activating therapeutics for the treatment of glioblastoma multiforme (GBM) have shown potential for tumor regression and increased survival over standard therapies. However, immunotherapy efficacy remains inconsistent with response assessment being complicated by early treatment-induced apparent radiological tumor progression and slow downstream effects. This inability to determine early immunotherapeutic benefit results in a drastically decreased window for alternative, and potentially more effective, treatment options. The objective of this study is to evaluate the effects of combination immunotherapy on early CD8+ cell infiltration and its association with long term response in orthotopic syngeneic glioblastoma models. Methods: Luciferase positive GBM orthotopic mouse models (GSC005-luc) were imaged via [89Zr]-CD8 positron emission tomography (PET) one week following treatment with saline, anti-PD1, M002 oncolytic herpes simplex virus (oHSV) or combination immunotherapy. Subsequently, brains were excised, imaged via [89Zr]-CD8 ImmunoPET and evaluated though autoradiography and histology for H&E and CD8 immunohistochemistry. Longitudinal immunotherapeutic effects were evaluated through [89Zr]-CD8 PET imaging one- and three-weeks following treatment, with changes in tumor volume monitored on a three-day basis via bioluminescence imaging (BLI). Response classification was then performed based on long-term BLI signal changes. Statistical analysis was performed between groups using one-way ANOVA and two-sided unpaired T-test, with p < 0.05 considered significant. Correlations between imaging and biological validation were assessed via Pearson's correlation test. Results: [89Zr]-CD8 PET standardized uptake value (SUV) quantification was correlated with ex vivo SUV quantification (r = 0.61, p < 0.01), autoradiography (r = 0.46, p < 0.01), and IHC tumor CD8+ cell density (r = 0.55, p < 0.01). Classification of therapeutic responders, via bioluminescence signal, revealed a more homogeneous CD8+ immune cell distribution in responders (p < 0.05) one-week following immunotherapy. Conclusions: Assessment of early CD8+ cell infiltration and distribution in the tumor microenvironment provides potential imaging metrics for the characterization of oHSV and checkpoint blockade immunotherapy response in GBM. The combination therapies showed enhanced efficacy compared to single agent immunotherapies. Further development of immune-focused imaging methods can provide clinically relevant metrics associated with immune cell localization that can inform immunotherapeutic efficacy and subsequent treatment response in GBM patients.

Combination immunotherapy with vaccine and oncolytic HSV virotherapy is time dependent.

PURPOSE: Oncolytic virotherapy or immunovirotherapy is a strategy that utilizes viruses to selectively infect and kill tumor cells while also stimulating an immune response against the tumor. Early clinical trials in both pediatric and adult patients using oncolytic herpes simplex viruses (oHSVs) have demonstrated safety and promising efficacy; however, combinatorial strategies designed to enhance oncolysis while also promoting durable T cell responses for sustaining disease remission are likely required. We hypothesized that combining the direct tumor cell killing and innate immune stimulation by oHSV with a vaccine that promotes T cell mediated immunity may lead to more durable tumor regression. EXPERIMENTAL DESIGN: To this end, we investigated the preclinical efficacy and potential synergy of combining oHSV with a self-assembling nanoparticle vaccine co-delivering peptide antigens and Toll-like receptor-7 and -8 agonists (TLR-7/8a) (referred to as SNAPvax™), that induces robust tumor specific T cell immunity. We then assessed how timing of the treatments (i.e., vaccine before or after oHSV) impacts T cell responses, viral replication, and preclinical efficacy. RESULTS: The sequence of treatments was critical, as survival was significantly enhanced when the SNAPvax™ vaccine was given prior to oHSV. Increased clinical efficacy was associated with reduced tumour volume and increases in virus replication and tumor antigen specific CD8+ T cells. CONCLUSIONS: These findings substantiate the criticality of combination immunotherapy timing and provide preclinical support for combining SNAPvax with oHSV as a promising treatment approach for both pediatric and adult tumors.

Bilateral metastatic renal hemangiopericytoma ten years after primary intracranial lesion

We report a case of bilateral metastatic renal hemangiopericytoma. A 37-year-old Caucasian male presented in 1993 with intracranial hemangiopericytoma. Subsequent metastatic disease noted years later include bilateral renal hemangiopericytoma 10 years after initial presentation. To our knowledge, this is only the second reported case of bilateral metastatic renal hemangiopericytoma.