Oncolytic Vaccinia Virus Gene Therapy for HNSCC

Abstract

Problem Oncolytic viral therapy a promising new strategy for the treatment of cancer and an oncolytic adenovirus was first licensed for head and neck squamous cell carcinoma (HNSCC). However, the outcomes of clinical trials with viral monotherapy have been disappointing. Oncolytic vaccinia virus represents an attractive alternative as its replication is less dependent than adenovirus on the genetic make-up of tumor cells and it has been used safely as the smallpox vaccine in millions of patients. Methods The potency and replication of vaccinia virus and adenovirus were compared in a panel of HNSCC cell lines in vitro before assessing the tumor selectivity of systemically delivered vaccinia virus in vivo. In order to increase antitumor potency, a novel vaccinia virus expressing the angiogenesis inhibitory endostatin-angiostatin fusion protein was constructed. The expression and function of this protein was confirmed in vitro and antitumor efficacy assessed in vivo. Results Oncolytic vaccinia virus was more potent than adenovirus against all HNSCC cell lines and displayed high selectivity for cancer cells, sparing normal cells both in vitro and in animal tumour models in vivo. Vaccinia virus expressing the endostatin-angiostatin fusion protein inhibited new blood vessel formation as well as tumour growth by oncolysis. The protein was expressed in virus-infected HNSCC cells and demonstrated function by the inhibition of human umbilical vein epithelial cell proliferation and tube formation in vitro. Treatment of nude mice bearing FaDu HNSCC xenografts significantly prolonged survival when compared to the oncolytic adenovirus ONYX-015 used previously for HNSCC. Conclusion This novel vaccinia virus is a promising therapeutic agent for HNSCC, which improved survival in tumour bearing mice and requires further evaluation in vivo. Significance The combination of an oncolytic vaccinia virus that delivers tumor-specific angiogenesis inhibition may prove to be an effective treatment for patients with HNSCC, with the potential for systemic delivery to treat metastatic disease. Support Cancer Research UK, Royal College of Surgeons of England, Barts and the London Trustees.