VasGene Therapeutics (United States)

Abstract One of the main goals of cancer therapeutics is to develop smart molecules that can deliver drugs or immunogens to cancer cells within the tumor, while avoiding the toxicity to normal cells. Lately, immune checkpoint inhibitors have shown significant effects in the field of cancer treatment. Atezolizumab is an immune check point inhibitor specific to PD-L1. In order to potentiate anti-tumor aspects of Atezolizumab, we have developed TecApta, a switchable single strand DNA oligonucleotide aptamer that specifically binds to this antibody with a high affinity and specificity. However, TecApta is detached from Atezolizumab upon binding of this antibody to its target PD-L1. This switchable aspect of TecApta makes it a suitable drug carrier for targeting cancer cells within the tumor microenvironment. We have developed modified versions of TecApta which include either the chemotherapy drug, gemcitabine, or the immune activator, TLR9A. Based on our in vitro data, both versions are biologically active. The gemcitabine sensitive cell line MDA-MB-231/Luc exhibits similar IC50s (20nM) for both gemcitabine-linked-TecApta (GMZ-TecApta) and the free unbound gemcitabine. Moreover, the same concentrations of TLR9A-linked-TecApta (TLR9A-TecApta) and the free TLR9A show similar effects in inducing TLR9 receptors in a cell-based assay. These results suggest that possibly GMZ-TecApta and TLR9A-TecApta can be carried by Atezolizumab and released within the tumor microenvironment, where they may induce apoptosis or aggravate an immune reaction, respectively. Animal studies will be conducted in the future to investigate the possibility of such favorable outcomes. Citation Format: Mohammad Sadegh Atefi, Sola Takahashi, David Sich, Jessica Grondin, Rami Doueiri, Lindsay Bourgeois, Gary Olsem, Akiko Futamura, Julie Yang, Joan Oliva, John Elshimali, Carlos Pereira. Switchable binding of TecApta to Atezolizumab provides the possibility of enhancing the therapeutic effects of this immune checkpoint inhibitor [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1752.

Simple SummaryPancreatic cancer is one of the deadliest solid malignancies. Pancreatic ductal adenocarcinoma accounts for 90% of pancreatic cancer cases with minimal response to traditional chemotherapies. Protein tyrosine kinases have been shown to be hyperactivated in cancers and thus can serve as therapeutic targets. Patient-derived tumor xenografts (PDXs) in animal models such as mice are an appropriate resource to identify such activated kinases. PDXs models are excellent for the identification of therapeutic targets as compared to cell line models as they better reflect an in vivo environment. We identified ephrin type-B receptor 4 (EphB4) as hyperactivated in PDXs derived from pancreatic ductal adenocarcinoma.Pancreatic ductal adenocarcinoma is a recalcitrant tumor with minimal response to conventional chemotherapeutic approaches. Oncogenic signaling by activated tyrosine kinases has been implicated in cancers resulting in activation of diverse effector signaling pathways. Thus, the discovery of aberrantly activated tyrosine kinases is of great interest in developing novel therapeutic strategies in the treatment and management of pancreatic cancer. Patient-derived tumor xenografts (PDXs) in mice serve as potentially valuable preclinical models as they maintain the histological and molecular heterogeneity of the original human tumor. Here, we employed high-resolution mass spectrometry combined with immunoaffinity purification using anti-phosphotyrosine antibodies to profile tyrosine phosphoproteome across 13 pancreatic ductal adenocarcinoma PDX models. This analysis resulted in the identification of 1199 tyrosine-phosphorylated sites mapping to 704 proteins. The mass spectrometric analysis revealed widespread and heterogeneous activation of both receptor and non-receptor tyrosine kinases. Preclinical studies confirmed ephrin type-B receptor 4 (EphB4) as a potential therapeutic target based on the efficacy of human serum albumin-conjugated soluble EphB4 in mice bearing orthotopic xenografts. Immunohistochemistry-based validation using tissue microarrays from 346 patients with PDAC showed significant expression of EphB4 in >70% of patients. In summary, we present a comprehensive landscape of tyrosine phosphoproteome with EphB4 as a promising therapeutic target in pancreatic ductal adenocarcinoma.

Members of the Eph family of receptor tyrosine kinases have been implicated in a wide array of human cancers. The EphB4 receptor is ubiquitously expressed in head and neck squamous cell carcinoma (HNSCC) and has been shown to impart tumorigenic and invasive characteristics to these cancers. In this study, we investigated whether EphB4 receptor targeting can enhance the radiosensitization of HNSCC. Our data show that EphB4 is expressed at high to moderate levels in HNSCC cell lines and patient-derived xenograft (PDX) tumors. We observed decreased survival fractions in HNSCC cells following EphB4 knockdown in clonogenic assays. An enhanced G2 cell cycle arrest with activation of DNA damage response pathway and increased apoptosis was evident in HNSCC cells following combined EphB4 downregulation and radiation compared to EphB4 knockdown and radiation alone. Data using HNSCC PDX models showed significant reduction in tumor volume and enhanced delay in tumor regrowth following sEphB4-HSA administration with radiation compared to single agent treatment. sEphB4-HSA is a protein known to block the interaction between the EphB4 receptor and its ephrin-B2 ligand. Overall, our findings emphasize the therapeutic relevance of EphB4 targeting as a radiosensitizer that can be exploited for the treatment of human head and neck carcinomas.

Over the last decade our understanding of cancer has fundamentally accepted the paradigm that cancer is a disease of stem cells. Rather than accumulate a multitude of mutations that would confer a normal cell all these variant properties, deregulatory mutation(s) arise in a cancer stem cell (CSC) or progenitor cell that already has several hallmarks of cancer as part of normal biological function such as tissue homeostasis, wound healing and repair. CSCs divide under influence of driver mutations and give rise to cells that differentiate into heterogeneous populations of tissue cells and set aside stem cells with self-renewal properties and cell-division potential. The heterogeneous populations then acquire secondary and tertiary mutations that aid the tumor evolve cells into gaining invasive and metastatic properties. Since most DNA-damaging agents and chemotherapy target DNA or cell division in replicating cells, these agents tend to target the heterogenic populations that results in de-bulking of the tumor and creates the illusion of therapy. However CSCs are metabolically inactive and contain mechanism(s) to repair their DNA, rendering them refractory and acquiring resistance to therapy. Inability to target CSCs has been the Achilles heel to developing therapeutics against cancer.

Prostate cancer is the most common cancer in men. Advanced prostate cancer spreading beyond the gland is incurable. Identifying factors that regulate the spread of tumor into the regional nodes and distant sites would guide the development of novel diagnostic, prognostic, and therapeutic targets. The aim of our study was to examine the expression and biological role of EphB4 in prostate cancer. EphB4 mRNA is expressed in 64 of 72 (89%) prostate tumor tissues assessed. EphB4 protein expression is found in the majority (41 of 62, 66%) of tumors, and 3 of 20 (15%) normal prostate tissues. Little or no expression was observed in benign prostate epithelial cell line, but EphB4 was expressed in all prostate cancer cell lines to varying degrees. EphB4 protein levels are high in the PC3 prostate cancer cell line and several folds higher in a metastatic clone of PC3 (PC3M) where overexpression was accompanied by EphB4 gene amplification. EphB4 expression is induced by loss of PTEN, p53, and induced by epidermal growth factor/epidermal growth factor receptor and insulin-like growth factor-I/insulin-like growth factor-IR. Knockdown of the EphB4 protein using EphB4 short interfering RNA or antisense oligodeoxynucleotide significantly inhibits cell growth/viability, migration, and invasion, and induces apoptosis in prostate cancer cell lines. Antisense oligodeoxynucleotide targeting EphB4 in vivo showed antitumor activity in murine human tumor xenograft model. These data show a role for EphB4 in prostate cancer and provide a rationale to study EphB4 for diagnostic, prognostic, and therapeutic applications.