Effects of Herpes Simplex Virus on Human Papillomavirus Promoters

We recently constructed an oncolytic mutant of Herpes simplex virus type-1 (HSV) in which the replication is controlled by the enhancer/promoter of Human papillomavirus type-16 (URR16, Cancer Gene Ther 14:985-993, 2007). Unexpectedly, the mutant replicated in brain tumor cells despite the fact that URR16 shows very low activity in such cells. Objectives: To find if a factor from HSV might affect the activity of URR16. Methods: Plasmids were constructed in which the luciferase reporter gene is under the control of either URR16, truncated derivatives of URR16, or the related URR18. Plasmids were transfected into the Tu167 oral cancer cell line after which the cells were infected with various strains of HSV. Results: When cells were transfected with URR16, wild type HSV (strain KOS) led to an increase in expression by a factor of 30.3 (±SD 16.3). A mutant (7134) that does not express ICP0 led to no increase in expression (1.18 ± 0.22) while a mutant (d106) that expresses only ICP0 did show induction (4.9 ± 0.73). The use of truncated plasmids did not reveal a unique responsive element in URR16, but major sites of activity were located in a 249-base fragment between nucleotides 7760 and 27, and in a 16-base fragment between nucleotides 89 and 105. When URR16 was replaced by URR18, induction by KOS was only 2.04-fold. Conclusion: The ICP0 gene of HSV encodes the previously unknown function of activating the enhancer/promoter of HPV-16, but not of HPV-18. The design of future oncolytic mutants of HSV-1 must take this into account, or the mutants will lack specificity for oral cancer.

Supported by NIH grant R01DE13214.