742 Multi-armed myxoma virus induces potent anti-tumor responses in vitro and in vivo

BackgroundMyxoma virus (MYXV) has been shown to selectively infect cancer cells in humans in vitro and inhibit tumor growth in mice. The genome of MYXV is large and amenable to engineering for expression of multiple transgenes. We armed MYXV with mouse or human IL-12 and human decorin. IL-12 is an immune modulator. Cellular responses to decorin include tumor cell intrinsic signaling effects, tumor matrix remodeling, and inhibition of the TGF-beta pathway. We hypothesized that MYXV armed with decorin and IL-12 would be an effective anti-tumor therapy. The current work describes the oncolytic activity and transgene expression, following exposure to armed MYXV in human cancer cell lines in vitro and efficacy in in vivo in murine models, as single agents and in combination with immune checkpoint inhibition.MethodsCytotoxicity was measured by a cell viability assay. ELISAs were used to detect transgene expression, Caspase-3 activation, and TGF-beta induced SMAD phosphorylation. Mouse tumor models were treated with vehicle control or the indicated virus.ResultsMYXV carrying payloads of decorin and mouse IL-12 (vMYX-mIL-12/Dec) or human IL-12 (vMYX-hIL-12/Dec) were tested. Human tumor cell lines infected with vMYX-hIL-12/Dec in vitro showed independent effects when levels of transgene expression and cytotoxicity were compared, suggesting that oncolytic activity and transgene expression differentially contribute to MYXV activity. Virus-free supernatants derived from infected cells suggested a decorin specific response in caspase-3 activation, and inhibition of TGF-beta signaling. Human IL-12 is not active on mouse immune cells giving the opportunity to evaluate the role of decorin in tumor regression. B16-F10 murine melanoma mice treated with vMYX-mIL-12/Dec showed a robust response while vMYX-hIL-12/Dec showed an intermediate anti-tumor response suggesting decorin has cancer inhibitory activity and synergized with IL-12. We tested anti-PD-1 and vMYX-mIL-12/Dec in the colon adenocarcinoma model MC38. We observed that the combination for multi-armed MYXV with an immune checkpoint inhibitor showed dramatically reduced tumor growth and improved survival.ConclusionsOur data demonstrates that MYXV with IL-12 and decorin payloads have cytotoxic activity in vitro and inhibit tumor growth in vivo. Cellular responses to decorin in vitro included inhibition of processes intrinsic to tumor progression. In mouse tumor models decorin played a role in inhibiting tumor progression and synergized with IL-12 implying the combination has immune-modulatory activity. Interestingly, MYXV with IL-12 and decorin payloads significantly synergized with anti-PD-1 in preventing tumor growth, suggesting a potentially new approach towards anti-cancer therapy.Ethics ApprovalAll studies and procedures involving animals were carried out under the institutional guidelines of Translational Drug Development Institutional Animal Care and Use Committee

Enhancing Therapeutic Efficacy of Oncolytic Herpes Simplex Virus with MEK Inhibitor Trametinib in Some BRAF or KRAS-Mutated Colorectal or Lung Carcinoma Models

Oncolytic virus (OV) as a promising therapeutic agent can selectively infect and kill tumor cells with naturally inherited or engineered properties. Considering the limitations of OVs monotherapy, combination therapy has been widely explored. MEK inhibitor (MEKi) Trametinib is an FDA-approved kinase inhibitor indicated for the treatment of tumors with BRAF V600E or V600K mutations. In this study, the oncolytic activity in vitro and anti-tumor therapeutic efficacy in vivo when combined with oHSV and MEKi Trametinib were investigated. We found: (1) Treatment with MEKi Trametinib augmented oHSV oncolytic activity in BRAF V600E-mutated tumor cells. (2) Combination treatment with oHSV and MEKi Trametinib enhanced virus replication mediated by down-regulation of STAT1 and PKR expression or phosphorylation in BRAF V600E-mutated tumor cells as well as BRAF wt/KRAS-mutated tumor cells. (3) A remarkably synergistic therapeutic efficacy was shown in vivo for BRAF wt/KRAS-mutated tumor models, when a combination of oHSV including PD-1 blockade and MEK inhibition. Collectively, these data provide some new insights for clinical development of combination therapy with oncolytic virus, MEK inhibition, and checkpoint blockade for BRAF or KRAS-mutated tumors.

Oncolytic H-1 parvovirus binds to sialic acid on laminins for cell attachment and entry

H-1 parvovirus (H-1PV) is a promising anticancer therapy. However, in-depth understanding of its life cycle, including the host cell factors needed for infectivity and oncolysis, is lacking. This understanding may guide the rational design of combination strategies, aid development of more effective viruses, and help identify biomarkers of susceptibility to H-1PV treatment. To identify the host cell factors involved, we carry out siRNA library screening using a druggable genome library. We identify one crucial modulator of H-1PV infection: laminin γ1 (LAMC1). Using loss- and gain-of-function studies, competition experiments, and ELISA, we validate LAMC1 and laminin family members as being essential to H-1PV cell attachment and entry. H-1PV binding to laminins is dependent on their sialic acid moieties and is inhibited by heparin. We show that laminins are differentially expressed in various tumour entities, including glioblastoma. We confirm the expression pattern of laminin γ1 in glioblastoma biopsies by immunohistochemistry. We also provide evidence of a direct correlation between LAMC1 expression levels and H-1PV oncolytic activity in 59 cancer cell lines and in 3D organotypic spheroid cultures with different sensitivities to H-1PV infection. These results support the idea that tumours with elevated levels of γ1 containing laminins are more susceptible to H-1PV-based therapies.

Nectin-1 Expression Correlates with the Susceptibility of Malignant Melanoma to Oncolytic Herpes Simplex Virus In Vitro and In Vivo

Talimogene laherparepvec (T-VEC), an oncolytic herpes simplex virus, is approved for intralesional injection of unresectable stage IIIB/IVM1a melanoma. However, it is still unclear which parameter(s) predict treatment response or failure. Our study aimed at characterizing surface receptors Nectin-1 and the herpes virus entry mediator (HVEM) in addition to intracellular molecules cyclic GMP-AMP synthase (cGAS) and stimulator of interferon genes (STING) as potential bio-markers for oncolytic virus treatment. In 20 melanoma cell lines, oncolytic activity of T-VEC was correlated with the expression of Nectin-1 but not HVEM, as evaluated via flow cytometry and immunohistochemistry. Knockout using CRISPR/Cas9 technology confirmed the superior role of Nectin-1 over HVEM for entry and oncolytic activity of T-VEC. Neither cGAS nor STING as evaluated by Western Blot and immunohistochemistry correlated with T-VEC induced oncolysis. The role of these biomarkers was retrospectively analyzed for the response of 35 cutaneous melanoma metastases of 21 patients to intralesional T-VEC injection, with 21 (60.0%) of these lesions responding with complete (n = 16) or partial regression (n = 5). Nectin-1 expression in pretreatment biopsies significantly predicted treatment outcome, while the expression of HVEM, cGAS, and STING was not prognostic. Altogether, Nectin-1 served as biomarker for T-VEC-induced melanoma regression in vitro and in vivo.

Transgene codon usage drives viral fitness and therapeutic efficacy in oncolytic adenoviruses

Arming oncolytic adenoviruses with therapeutic transgenes is a well-established strategy for multimodal tumour attack. However, this strategy sometimes leads to unexpected attenuated viral replication and a loss of oncolytic effects, preventing these viruses from reaching the clinic. Previous work has shown that altering codon usage in viral genes can hamper viral fitness. Here, we have analysed how transgene codon usage impacts viral replication and oncolytic activity. We observe that, although transgenes with optimized codons show high expression levels at the first round of infection, they impair viral fitness and are therefore not expressed in a sustained manner. Conversely, transgenes encoded by suboptimal codons do not compromise viral replication and are thus stably expressed over time, allowing a greater oncolytic activity both in vitro and in vivo. Altogether, our work shows that fine-tuning codon usage leads to a concerted optimization of transgene expression and viral replication paving the way for the rational design of more efficacious oncolytic therapies.

An Oncolytic Adenovirus Encoding SA-4-1BBL Adjuvant Fused to HPV-16 E7 Antigen Produces a Specific Antitumor Effect in a Cancer Mouse Model

Human papillomaviruses (HPVs) are responsible for about 25% of cancer cases worldwide. HPV-16 E7 antigen is a tumor-associated antigen (TAA) commonly expressed in HPV-induced tumors; however, it has low immunogenicity. The interaction of 4-1BBL with its receptor induces pleiotropic effects on innate, adaptive, and regulatory immunity and, if fused to TAAs in DNA vaccines, can improve the antitumor response; however, there is low transfection and antitumor efficiency. Oncolytic virotherapy is promising for antitumor gene therapy as it can be selectively replicated in tumor cells, inducing cell lysis, and furthermore, tumor cell debris can be taken in by immune cells to potentiate antitumor responses. In this study, we expressed the immunomodulatory molecule SA-4-1BBL fused to E7 on an oncolytic adenovirus (OAd) system. In vitro infection of TC-1 tumor cells and NIH-3T3 non-tumor cells with SA/E7/4-1BBL OAd demonstrated that only tumor cells are selectively destroyed. Moreover, protein expression is targeted to the endoplasmic reticulum in both cell lines when a signal peptide (SP) is added. Finally, in an HPV-induced cancer murine model, the therapeutic oncolytic activity of OAd can be detected, and this can be improved when fused to E7 and SP.