An oncolytic mutant of herpes simplex virus type-1 in which replication is governed by a promoter/enhancer of human papillomavirus type-16

Abstract

Although herpes simplex virus type-1 (HSV-1) can be used as an oncolytic virus it has the undesirable side effect of neurotoxicity. To create a virus with improved specificity for oral cancer we used a fragment of human papillomavirus type-16, which is frequently found in oral and cervical cancers, but not elsewhere. The upstream regulatory region, URR16, was shown to have a high level of transcriptional activity in three of four oral cancer cell lines but low activity in three cell lines derived from brain cancers. URR16 was therefore placed in HSV-1, replacing the promoter of the essential gene ICP4, and the resulting virus was named HSPV-1. When cells were infected with HSPV-1, ICP4 was expressed at levels that were not associated with the level of activity of URR16. The virus replicated in each type of cell to a final titer that showed a correlation with the level of expression of ICP4, but with no correlation to either the tumor of origin or the presence of HPV sequences in the cells. To find if some function of HSV-1 was affecting the activity of URR16, oral cancer cells were transfected with a URR-reporter construct and were then infected with virus. This induced transcription, which was attributed to immediate-early viral genes other than ICP4. A promoter/enhancer from a papillomavirus therefore has the potential to regulate the functions of an oncolytic strain of HSV-1, and is affected by functions of both the host cell and of HSV-1 itself.

Effect of a caspase inhibitor, zVADfmk, on the inhibition of breast cancer cells by herpes simplex virus type 1

“…Alternatively, essential genes of the virus can be placed under the control of tissue-specific promoters, thus limiting their replication to specific tissues. [1][2][3] Finally, therapeutic strains in which the virus thymidine kinase gene remains unmodified will still be susceptible to antiviral drugs such as acyclovir. The combination of modified viruses with chemical agents to increase their potency in tumors shows promise for use in the treatment of human cancers.…”

“…Cell growth was assessed at the indicated times, by the conversion of thiazolyl blue into formazan (MTT assay) as measured at (OD 560 -OD 690 ). 1,30 Growth of virus-infected cells was expressed as a percentage of mock-infected cells.…”

“…Viral titers were measured at 48 and 96 hpi by a standard plaque assay on Vero cells. 1 To determine the number of virus genomes, quantitative polymerase chain reaction (qPCR) was used. Viral DNA was isolated from cell lysates or medium using the DirectPCR Lysis reagent (Viagen Biotech, Los Angeles, CA) combined with 1 mg ml À1 proteinase K (Viagen) following the manufacturers' instructions.…”

“…Herpes simplex virus-1 (HSV-1) is a suitable candidate virus because of its large genome with many non-essential proteins, ease of manipulation, natural oncolytic properties and wide host tropism. [1][2][3] The removal of virulence genes enhances the safety of HSV-1 vectors against serious complications and/or reversion to wild type. [4][5][6] Some of these oncolytic HSV-1 viruses have been approved for clinical trials in breast cancer, 3,7 head and neck carcinoma, 8 glioma, 9 melanoma, 10 non-small-cell lung carcinoma 11 and metastases from colorectal cancer 12 (reviewed in Manservigi et al 13 ).…”

Development of an oncolytic herpes simplex virus using a tumor-specific HIF-responsive promoter

“…An alternative approach is to use a viral, rather than cellular, promoter to regulate ICP4 expression. HSPV-1 contains the human papillomavirus type-16 upstream regulatory region (URR16) promoter for the targeted expression of ICP4 in oral cancer 17. Unfortunately, viral replication did not correlate with the tumor origin or the presence of HPV sequences in the cell.…”