Virotherapy on the basis of oncolytic vaccinia virus (VACV) infection is a promising approach for cancer therapy. In this study we describe the establishment of a new preclinical model of feline mammary carcinoma (FMC) using a recently established cancer cell line, DT09/06. In addition, we evaluated a recombinant vaccinia virus strain, GLV-5b451, expressing the anti-vascular endothelial growth factor (VEGF) single-chain antibody (scAb) GLAF-2 as an oncolytic agent against FMC. Cell culture data demonstrate that GLV-5b451 virus efficiently infected, replicated in and destroyed DT09/06 cancer cells. In the selected xenografts of FMC, a single systemic administration of GLV-5b451 led to significant inhibition of tumor growth in comparison to untreated tumor-bearing mice. Furthermore, tumor-specific virus infection led to overproduction of functional scAb GLAF-2, which caused drastic reduction of intratumoral VEGF levels and inhibition of angiogenesis.In summary, here we have shown, for the first time, that the vaccinia virus strains and especially GLV-5b451 have great potential for effective treatment of FMC in animal model.
Schwannoma tumours typically arise on the 8th cranial nerve and are mostly caused by loss of the tumour suppressor Merlin (NF2). There are no approved chemotherapies for these tumours and the surgical removal of the tumour carries a high risk of damage to the 8th or other close cranial nerve tissue. New treatments for schwannoma and other NF2-null tumours such as meningioma are urgently required. Using a combination of human primary tumour cells and mouse models of schwannoma, we have examined the role of the Hippo signalling pathway in driving tumour cell growth. Using both genetic ablation of the Hippo effectors YAP and TAZ as well as novel TEAD palmitoylation inhibitors, we show that Hippo signalling may be successfully targeted in vitro and in vivo to both block and, remarkably, regress schwannoma tumour growth. In particular, successful use of TEAD palmitoylation inhibitors in a pre-clinical mouse model of schwannoma points to their potential future clinical use. We also identify the cancer stem cell marker aldehyde dehydrogenase 1A1 (ALDH1A1) as a Hippo signalling target, driven by the TAZ protein in human and mouse NF2-null schwannoma cells, as well as in NF2-null meningioma cells, and examine the potential future role of this new target in halting schwannoma and meningioma tumour growth.
Introduction: Meningiomas are the most common intracranial tumor and arise from the arachnoidal cell layer of the meninges. Schwannomas develop from Schwann cells which provide myelin and trophic support in the peripheral nerves. The tumor suppressor Merlin is deleted in approximately 50-60% of meningiomas and 70% of schwannomas. Loss of Merlin results in dysregulation of the Hippo pathway and consequent aberrant activation of the transcriptional coactivators YAP and TAZ. Nuclear localisation of YAP and TAZ has been shown to drive tumor phenotypes in many cancers. The TEAD family of transcription factors are major targets of YAP and TAZ-dependent signaling. TEAD family members undergo autopalmitoylation and this modification is required for transcriptional activation by YAP or TAZ. Vivace therapeutics have identified small molecule inhibitors of autopalmitoylation that block the interaction of TEAD family members with YAP and TAZ. This study seeks to establish the efficacy of small molecule inhibitors of TEAD activity in meningioma and schwannoma tumor cells. Experimental Procedures: Meningioma cell lines, primary human meningioma and schwannoma cells, as well as a schwannoma mouse model (PerisotinCRE /NF2 fl/fl) were treated with Vivace inhibitors to assess their effects upon tumor cell proliferation and TEAD driven transcription. Results: TEAD inhibition significantly reduced the proliferation of the BenMen-1 meningioma cell line, as well as in primary human meningioma cells. In schwannoma, inhibitors reduced proliferation and also reduced the expression of CTGF, a target of TEAD activation in both primary human meningioma and schwannoma cells. These novel inhibitors are also currently being tested in the Periostin CRE-NF2fl/fl schwannoma mouse model to evaluate their efficacy in vivo. Conclusions: The use of these novel compounds to inhibit TEAD function shows great potential as an effective treatment for reducing the rate of cell proliferation in meningioma and schwannoma, two clinically important tumor types. Citation Format: Liyam Laraba, Julio Grimm de Guibert, Tracy T. Tang, Leonard Post, David B. Parkinson. TEAD inhibition reduces tumor proliferation in Merlin null meningioma and schwannoma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6384.
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