Non-viral suicide gene therapy in cervical, oral and pharyngeal carcinoma cells with CMV- and EEV-plasmids.

Abstract

Cervical cancer is the third most common cause of cancer in women. The 5-year survival rate in oropharyngeal squamous cell carcinomas is approximately 50% and this rate has not improved in recent decades. These cancers are accessible to direct intervention. We examined the ability of a highly efficient non-viral vector, TransfeX (ATCC, Manassas, VA, USA), to deliver the suicide gene HSV-tk to cervical, oral and pharyngeal cancer cells and to induce cytotoxicity following the administration of the prodrug, ganciclovir. HeLa cervical carcinoma, HSC-3 and H357 oral squamous cell carcinoma and FaDu pharyngeal carcinoma cells were transfected with cytomegalovirus (CMV)- or enhanced episomal vector (EEV)-driven HSV-tk plasmids and treated with ganciclovir for 24-120h. Cell viability was assessed by Alamar blue. The viability of HeLa cells was reduced to only 30-40%, despite the very high levels of transgene expression. By contrast, the viability of HSC-3 cells was reduced to 10%, although transgene expression was 18-fold lower than that in HeLa cells. An approximately five-fold higher transgene expression was obtained with the EEV-plasmid than from the CMV-plasmid. Nevertheless, HeLa cell viability after suicide gene+ganciclovir treatment was reduced by only 35% compared to 70% with the CMV-plasmid. For HSC-3 cells, the reduction was 40% for the EEV- and 80% for the CMV-plasmid. The lower efficiency of transfection with the EEV-plasmid may explain the lower cytotoxicity. TransfeX-mediated gene delivery to cervical, pharyngeal and oral cancer cells may be used for suicide gene therapy. The levels of transgene expression, however, do not translate directly to cytotoxicity.