Comparative pathology of cells transformed by herpes simplex virus type 1 or type 2

Gene therapy--its potential in the management of oral cancer

Gene therapy is an important new approach to the treatment of many diseases. This review summarises the methods that are available for developing gene therapy, and demonstrates that oral cancer is probably susceptible to these approaches.

Viruses and oral cancer

Oral cancer is a disease with a complex etiology. There is evidence for important roles of smoking, drinking, and genetic susceptibility, as well as strong indications that DNA viruses could be involved. The herpes simplex virus type 1 has been associated with oral cancer by serological studies, and animal models and in vitro systems have demonstrated that it is capable of inducing oral cancer. Papillomaviruses are found in many oral cancers and are also capable of transforming cells to a malignant phenotype. However, both virus groups depend on co-factors for their carcinogenic effects. Future research on viruses and oral cancer is expected to clarify the role of these viruses, and this will lead to improvements in diagnosis and treatment of the disease.

Electron microscopic localization of acridine orange chromatin interaction products in cells transformed by herpes simplex virus type 2

The purpose of this study was to examine the distribution pattern of acridine orange (AO) binding to DNA in transformed cells and derived tumor cells. Two cell clones from hamster embryonic fibroblasts (HEF) transformed by herpes simplex virus type 2, tumor cells derived from the transformed cell clones, and normal HEF in culture were processed for ultracytochemistry. Uptake studies and autoradiography using [3H] thymidine and [3H]-uridine were also performed. Ultrastructural examination revealed that AO became bound to DNA exclusively within the euchromatin portion of the cell nucleus. The percentages of AO-positive cell nuclei were 18.0% and 15.5% in transformed cell clones and 21.3% and 18.3% in the derived tumor cells, but only 2. 7% in the HEF. The average amounts of AO-chromatin interaction products increased in the transformed and tumor cells. Labeling indices of [3H] thymidine were 28.9% and 33.2% in both the transformed cell clones, 32.4% and 36.9% in their tumor cells, and 3.7% in the HEF. Euchromatin/heterochromatin (EU/HEF) ratios were found to be higher in AO-positive nuclei than in AO-negative nuclei in each cell line. The increase in the number of AO-positive nuclei and in the EU/HET ratios may represent a basic reaction of cell nuclei in transformation and tumorigenesis.

Tumorgenicity of herpesvirus hominis type 2-transformed cells (line 333-8-9) in adult hamsters

Inoculation of adult hamsters with greater than 1.5 X 10(2) Herpesvirus type 2 (HSV-2) transformed hamster embryo fibroblasts induced rapidly growing tumours at the site of inoculation, in more than 50 per cent of animals. The tumours were examined by light and electron microscopy, and were histologically anaplastic fibrosarcomas. Lung metastases were frequently found in tumour-bearing animals; these were usually only seen microscopically, and were cytologically similar to the primary tumours. The nature of tumour development showed similarities with naturally occurring tumours of man, and HSV-2 tumour is probably a better model of human cancer than other virus-induced tumours studied in the past.

Transformation of mouse cells after infection with ultraviolet irradiation-inactivated herpes simplex virus type 2

A transformed mouse cell line (H238) was obtained following the infection of 238 mouse cells with ultraviolet (UV) irradiation-inactivated herpes simplex virus type 2 (HSV-2). The transformed cells produced tumors with a 100% incidence within 8 weeks in 6-week-old syngeneic BALB/c mice at an inoculum of 1 times 10(6). Indirect immunofluorescence (IF) tests revealed the presence of HSV antigens in the transformed cells. Antibodies to HSV-2 were found in the sera of tumor-bearing animals by neutralization and IF techniques. Neither HSV-2 infectious virus nor viral antigens could be detected by the transfer of transformed-cell DNA into permissive cells.