743 Resistance to oncolytic vaccinia can be reversed by targeting regulatory T cells with vaccinia-directed delivery of a TGFβ inhibitor

Background

Oncolytic viruses are an underappreciated immunotherapy capable of inflaming the tumor microenvironment (TME), vaccinating a patient against their own tumor, and delivering gene therapy to the TME. However, apart from the oncolytic HSV T-vec, these therapies have not seen widespread use, due in part to incomplete understanding of their immunologic mechanisms of action. We sought to determine features of oncolytic vaccinia virus (VV) response and resistance using subclones of the HPV+ head and neck cancer model MEER rendered sensitive or resistant to VV.

Methods

A VV sensitive MEER tumor resisting treatment was serially passaged in mice and treated with VV until a stably resistant line was generated (Fig1). Sensitive or resistant MEER tumors were implanted, treated with a single intratumoral dose of VV, and harvested 4–7 days later for cytometric analysis. A genetically encoded TGFβ inhibitor was recombined into oncolytic VV (VV-TGFβi).

Results

We used serial in vivo passaging to generate a VV-resistant MEER line (MEERvvR) from one sensitive to VV (MEERvvS, figure 1) and compared their immune infiltrate. While VV promoted acute cytokine production and cytotoxicity in conventional T cells, the major determining factor between sensitivity and resistance was the phenotype of Treg cells. At baseline, Treg cells in MEERvvS had lower Nrp1 expression and higher IFNγ-STAT1 signaling compared to MEERvvR, indicative of Treg 'fragility'. VV treatment induced MEERvvS Treg cells to become immunostimulatory and produce IFNγ (figure 2). RNAseq revealed MEERvvR produced more TGFβ than MEERvvS cells, suggesting these tumors directly stabilize Treg cells. To determine if MEERvvR could be sensitized to VV, we engineered oncolytic vaccinia to produce a genetically-encoded TGFβ inhibitor which binds TGFβRII, preventing TGFβ1-3 binding (VV-TGFβi). When MEERvvR were treated with VV-TGFβi, elite responses were restored, with commensurate increase in survival (figure 3) associated with increased STAT1 signaling in Treg cells.

Conclusions

Resistance to oncolytic vaccinia is controlled by Treg cell phenotype; tumors harboring more fragile Treg cells respond exquisitely to VV. An oncolytic vaccinia engineered to produce a novel TGFβi could remodel the TME to be less supportive of Tregs, rendering resistant tumors sensitive to VV. Our data highlight the importance of Treg cell status in resistance to oncolytic virus therapy and suggest TGFβ can be effectively targeted through an inhibitor encoded within the virus. Importantly, this TME directed production of the TGFβi carries no toxicity previously associated with systemic TGFβ inhibition, suggesting a viral approach to TGFβ inhibition can be an effective strategy support broader immunotherapy response.

Abstract 743 Figure 1

Strategy used to generate a vaccinia resistant MEER (MEERvvR) from vaccinia sensitive MEER (MEERvvS)

Abstract 743 Figure 2

IFNγ production in Treg cells in MEERvvS and MEERvvR after treatment with PBS or control vaccinia (VV-Ctrl)

Abstract 743 Figure 3

Survival of VV-resistant MEER treated with PBS, control vaccinia (VV-Ctrl), or vaccinia engineered to deliver a potent inhibitor of TGFβ (VV-TGFβi)

Abstract B34: TGF-β-rich tumor-derived exosomes promote a proangiogenic phenotype in HNSCC

TGF-β is a key regulator for tumor initiation and progression in head and neck squamous cell carcinoma (HNSCC). Tumor-derived exosomes (TEX) contain TGF-β and accumulate in the tumor microenvironment (TME). This study characterizes in vitro and in vivo the TGF-β content of HNSCC-derived exosomes and evaluates TGF-β signaling by exosomes that promotes angiogenesis. TEX were isolated from supernantants of 5 different HNSCC cell lines by mini size exclusion chromatography (mini-SEC) and characterized by electron microscopy, nanoparticle tracking analysis, and immunoblotting. TGF-β content in exosomes was evaluated by mass spectrometry (LC-MS/MS). Proliferation and migration of SVEC4-10 lymphendothelial cells as well as phosphorylation of Smad2 in response to TEX were investigated in vitro. These experiments were confirmed in vivo, using a matrigel plug model in mice. A novel trivalent TGF-β receptor trap (mRER) was used to inhibit TGF-β signaling in vitro and in vivo. The 4-nitroquinoline-1-oxide (4-NQO) oral carcinogenesis mouse model was used to study TGF-β signaling in the TME during all phases of carcinogenesis. Exosomes isolated from plasma of these 4-NQO mice were quantified and the exosome TGF-β content was analyzed. Another cohort of 4-NQO mice received injections of TGF-β(+) TEX at early stages of carcinogenesis. In addition, TGF-β levels and activity were measured in exosomes isolated from plasma of 20 HNSCC patients. TEX carried high levels of TGF-β and were found to be potent inducers of angiogenesis in vitro and in vivo through functional reprogramming and phenotypic modulation of endothelial cells. Proliferation (p<0.01) and migration (p<0.01) by SVEC4-10 were stimulated by TEX and effects were inhibited by mRER treatment of SVEC4-10 (p<0.05). TEX promoted formation of defined vascular structures in vivo and increased (p<0.001) vascularization in matrigel plugs relative to controls. Those effects were inhibited by mRER treatment in a dose-dependent manner (p<0.001). TGF-β expression increased in 4-NQO tumor tissue during carcinogenesis (p<0.01) and correlated with increasing exosome numbers in plasma. TGF-β was found to be carried by plasma-derived exosomes throughout all stages of carcinogenesis. The injection of TEX into 4-NQO mice led to a systemic immunosuppression (p<0.001), increased vascularization (p<0.01), and enhanced the TGF-β levels in the tumor tissue (p<0.05). Exosomes in plasma of HNSCC patients carried varying levels of TGF-β, and patients with nodal metastases had higher TGF-β levels (p<0.01) relative to patients with no metastasis. The data show that TGF-β signaling by TEX in HNSCC promotes angiogenesis and drives tumor progression. Silencing of TGF-β in TEX promises to add new options to existing antiangiogenic therapies.

Citation Format: Nils Ludwig, Saigopalakrishna S. Yerneni, Juliana H. Azambuja, Beatrice M. Razzo, Cynthia S. Hinck, Monika Pietrowska, Andrew Hinck, Theresa L. Whiteside. TGF-β-rich tumor-derived exosomes promote a proangiogenic phenotype in HNSCC [abstract]. In: Proceedings of the AACR-AHNS Head and Neck Cancer Conference: Optimizing Survival and Quality of Life through Basic, Clinical, and Translational Research; 2019 Apr 29-30; Austin, TX. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(12_Suppl_2):Abstract nr B34.

D2HGDH regulates alpha-ketoglutarate levels and dioxygenase function by modulating IDH2

Isocitrate dehydrogenases (IDH) convert isocitrate to alpha-ketoglutarate (α-KG). In cancer, mutant IDH1/2 reduces α-KG to D2-hydroxyglutarate (D2-HG) disrupting α-KG-dependent dioxygenases. However, the physiological relevance of controlling the interconversion of D2-HG into α-KG, mediated by D2-hydroxyglutarate dehydrogenase (D2HGDH), remains obscure. Here we show that wild-type D2HGDH elevates α-KG levels, influencing histone and DNA methylation, and HIF1α hydroxylation. Conversely, the D2HGDH mutants that we find in diffuse large B-cell lymphoma are enzymatically inert. D2-HG is a low-abundance metabolite, but we show that it can meaningfully elevate α-KG levels by positively modulating mitochondrial IDH activity and inducing IDH2 expression. Accordingly, genetic depletion of IDH2 abrogates D2HGDH effects, whereas ectopic IDH2 rescues D2HGDH-deficient cells. Our data link D2HGDH to cancer and describe an additional role for the enzyme: the regulation of IDH2 activity and α-KG-mediated epigenetic remodelling. These data further expose the intricacies of mitochondrial metabolism and inform on the pathogenesis of D2HGDH-deficient diseases.

Schistosoma mansoni: TGF-beta signaling pathways

Schistosome parasites have co-evolved an intricate relationship with their human and snail hosts as well as a novel interplay between the adult male and female parasites. We review the role of the TGF-beta signaling pathway in parasite development, host-parasite interactions and male-female interactions. The data to date support multiple roles for the TGF-beta signaling pathway throughout schistosome development, in particular, in the tegument which is at the interface with the host and between the male and female schistosome, development of vitelline cells in female worms whose genes and development are regulated by a stimulus from the male schistosome and embryogenesis of the egg. The human ligand TGF-beta1 has been demonstrated to regulate the expression of a schistosome target gene that encodes a gynecophoric canal protein in the schistosome worm itself. Studies on signaling in schistosomes opens a new era for investigation of host-parasite and male-female interactions.