Administration of Autologous Dendritic Cells (DCs) Infected With an Adenovirus Expressing Her-2

Overview

We, the researchers at Hamilton Health Sciences, have developed a novel approach to cancer therapy using transfected dendritic cells (DCs) to generate enhanced immunity to defined tumor antigens. Dendritic cells are highly specialized antigen presenting cells found in the bone marrow, lymph nodes, skin and thymus. Infection of DCs with Adenovirus (Ad) vectors incorporating genes for defined tumor antigens enables intracellular expression and major histocompatability complex (MHC)-restricted presentation of tumor peptides by transfected DCs. Given the potent immunostimulatory properties of DCs and ability to use gene transfer to "load" DCs with tumor antigen, we hypothesize that administration of transduced autologous DCs may have potential therapeutic benefit as a cancer vaccine. We have examined Ad-tumor antigen DC based vaccination in murine models of breast cancer and melanoma. In both models, injection(s) of Ad-transduced DCs results in highly potent immune activation and antigen-specific anti-tumor responses. In these models, high levels of antigen-specific, cytotoxic effector lymphocytes that recognize and kill cancer cells directly correlates with a therapeutic response (tumor regression and/or complete protection of animals subsequently re-challenged with tumor cells). Animals demonstrating specific in vitro immunity are protected against subsequent injection of cancer cells. Moreover, we have observed complete resolution and significant long-term survival in animals with established metastatic disease with no demonstrable toxicity. As opposed to vaccination protocols with tumor peptides or purified epitopes that are MHC-I restricted (i.e. HLA-A2), we have found that injection of DCs transduced with a vector expressing the entire tumor antigen results in peptide presentation from both MHC-I and MHC-II complexes. The subsequent immune response is comprised of both CD4+ and CD8+ T cell populations. Thus, Ad-based gene transfer of tumor antigens appears to be an efficient approach: (1) enabling sustained endogenous peptide processing, and (2) facilitating DC-specific presentation to the host immune system. We have shown that using a replication deficient adenovirus vector expressing Her-2/neu DNA under the control of a human mouse mammary tumor virus (MMTV) promoter that we can transfect bone marrow derived DCs (AdHer2/DC). These cells are then used to immunize recipient mice against tumour challenge with Her2 transgenic tumour cells. The protection is antigen specific (anti Her2). On the basis of these pre-clinical studies we will initiate a pilot trial of the AdHer2/DC vaccine in Her -2/neu overexpressing patients with metastatic breast cancer. Long-term goals and implications of possible results: The goals of this initial pilot phase I study are to evaluate the safety and dosing schedule of the vaccine therapy. The vaccine will be tested in subsequent phase II and III studies to determine efficacy in comparison to standard therapies. The long-term goals are to eventually test this therapy in the adjuvant breast cancer setting in Her-2/neu overexpressing patients.