REVIEW Combined therapeutic use of AdGFPFasL and small molecule inhibitors of ceramide metabolism in prostate and head and neck cancers: a status report JS Norris 1 , A Bielawska 2 , T Day 3 , A El-Zawahri 1 , S ElOjeimy 1 , Y Hannun 2 , D Holman 1 , M Hyer 4 , C Landon 1 , S Lowe 1 , JY Dong 1 , J McKillop 1 , K Norris 5 , L Obeid 6 , S Rubinchik 1 , M Tavassoli 7 , S Tomlinson 1 , C Voelkel-Johnson 1 and X Liu 1 1 Departments of Microbiology and Immmunology, Medical University of South Carolina (MUSC), Charleston, SC, USA; 2 Department of Biochemistry and Molecular Biology, Medical University of South Carolina (MUSC), Charleston, SC, USA; 3 Otolaryngology – Head & Neck Surgery, Medical University of South Carolina (MUSC), Charleston, SC, USA; 4 The Burnham Institute, Reed Lab, La Jolla, CA, USA; 5 Surgical Neurology Branch, NINDS, Porter Neuroscience Research Center, Bethesda, MD, USA; 6 General Internal Medicine/Geriatrics, Medical University of South Carolina (MUSC), Charleston, SC, USA and 7 Guy’s, King’s & St Thomas’ College of London, Oral Pathology Dental Institute, University of London, London, UK As of January 2005, there were 1020 gene therapy clinical trials ongoing worldwide with 675 or 66.2% devoted to cancer gene therapy. The majority are occurring in the US and Europe (http://www.wiley.co.uk/genetherapy/clinical/). At the present time, to our knowledge there are no trials that employ gene delivery of Fas Ligand (FasL). As an important note, and in contrast to somatic cell therapy trials, there are no reported deaths due to therapeutic vector administration in any cancer gene therapy trial. That said, from our studies and from the published literature, the issue of gene delivery remains the major obstacle to successfully employing gene therapy for cancer treatment. Numerous laboratories are studying this with many different approaches. My co-workers and I have focused on the delivery issue by using various approaches that address tumor targeting and transgene expression. In addition, we are focusing on enhancing tumor cell killing via the bystander effect and through use of small molecules to enhance bystander activity. Cancer Gene Therapy (2006) 13, 1045–1051. doi:10.1038/sj.cgt.7700965; published online 9 June 2006 Keywords: FasL; HNSCC; ceramide; prostate; adenovirus; bystander effect Tissue-specific expression Our initial approach was to develop tissue specificity of transgene expression, by using tissue or tumor-restricted promoters to regulate a TET-derived transcription factor (tTA) which drives transcription of the selected transgene (FasL, Apoptin, Bax or TRAIL) 1–9 (See Figure 1a). We successfully carried out such studies with adenoviral vectors and demonstrated restricted gene expression. 1 To target expression to the prostate, we utilized a modified rat probasin promoter AAR2PB developed by the Matusik laboratory. 10,11 We have shown tissue selectivity of the prostate targeting vector, and we demonstrated that it can be injected into the mouse tail vein at 1 Â 10 9 pfu with no negative effect on mouse survival and no observable liver damage. 1 Conversely, if we inject a virus with a CMV driven GFPFasL fusion gene, the mice die within 24 h. These data demonstrate restricted expression is occurring. Of special note, this virus is designed for orthotopic use in human gene therapy and any reasonably sized promoter can be inserted in the regulatory region to target tumors or specific tissues. Most recently, we have shifted our focus to head and neck cancer (HNSCC) xenografts and we are now developing a vector that specifically targets tumor versus normal tissue using a tumor-specific promoter. Based on our data with this model and because of its general accessibility for orthotopic injection, this will likely be our first target for a Phase I clinical trial. Received 8 August 2005; revised 22 January 2006; accepted 5 March 2006; published online 9 June 2006 Correspondence: Dr JS Norris, Department of Microbiology & Immunology, PO Box 250504, 173 Ashley Avenue, Charleston, South Carolina 29425, USA. E-mail: norrisjs@musc.edu Cancer Gene Therapy (2006) 13, 1045–1051 r 2006 Nature Publishing Group All rights reserved 0929-1903/06 $30.00 www.nature.com/cgt