E1A oncogene-induced cellular sensitization to immune-mediated apoptosis is independent of p53 and resistant to blockade by E1B 19 kDa protein

E1A oncogene expression sensitizes mammalian cells to apoptosis triggered by cytolytic lymphocytes (CL) [16]. Most studies suggest that E1A-induced apoptosis involves a p53-dependent cellular pathway that is blocked by the E1B 19 kDa gene product. In this study, the roles of p53 and E1B 19 kDa were tested for E1A sensitization to CL-induced apoptosis in contrast with apoptosis triggered by TNF alpha or chemical injuries. E1A sensitization to immune-mediated (CL- or TNF-induced) apoptosis was independent of p53 expression and was resistant to blockade by E1B 19 kDa protein in mouse and hamster cells. In contrast, the p53 requirement for chemically induced apoptosis of E1A-sensitized cells varied with the agent used to treat cells. Apoptosis induced by diverse chemical agents (hygromycin, beauvericin, etoposide, H(2)O(2)) was blocked by E1B 19 kDa expression. Therefore, both the p53-dependence and the E1B 19 kDa blockade of E1A-induced cellular sensitization to apoptotic injury depend on the type of proapoptotic injury tested. These data suggest that the mechanisms by which E1A sensitizes tumor cells to immune-mediated apoptosis and to rejection by immunocompetent animals do not require cellular expression of wild-type p53 and can function independently of the Bcl-2-like, antiapoptotic mechanisms of E1B 19 kDa.

Transcriptional activation of NF-kappa B activity by Epstein-Barr virus (EBV) LMP1 as a selective therapeutic strategy for EBV-associated diseases

Epstein-Barr virus (EBV) has been known to be associated with many malignant tumors, including nasopharyngeal carcinoma (NPC). Previous studies have indicated that an EBV-encoded oncoprotein, latent membrane protein 1 (LMP1), is expressed in many NPC tissues. LMP1 has been shown to stimulate HIV LTR through the two NF-kappa B binding sites within this promoter. In this study, we examined the feasibility of using this property of LMP1 as a therapeutic strategy for the treatment of NPC. This therapy consists of the preferential killing of the LMP1-expressing cells by gene transfer using the NF-kappa B-mediated herpes simplex virus thymidine kinase (HSVtk)/ganciclovir (GCV) system. The 800-bp HIV-LTR, which contains two NF-kappa B binding sites, was used to drive the HSVtk gene. Stable C33A cell clones expressing the LMP1 and the HSVtk genes were subjected to the GCV sensitivity test. Results showed that cells expressing both the LMP1 and the HSVtk genes were highly sensitive to GCV treatment. These cells were introduced into nude mice subcutaneously and tumors became palpable within 2 weeks. GCV was then introduced intraperitoneally to these mice and the sizes of the tumors were measured daily. Results showed that the tumors regressed in the group of mice carrying cells that stably expressed both the LMP1 and the HSVtk genes, but not in mice carrying cells containing LMP1 or HSVtk alone. Our data indicate that the HSVtk gene expressed from a NF-kappa B-binding motif-containing promoter that is regulated by LMP1 may be used as an in vivo gene therapy strategy of EBV LMP1-expressing cancers such as NPC.

Rebleeding rate of various stigmata of recent hemorrhage in peptic ulcer bleeding with different severity

The stigmata of recent hemorrhage (SRH) have been used as a factor for predicting peptic ulcer rebleeding. In previous studies, the rebleeding rate of the visible vessel varied. A hypothesis had been proposed stating that the evolution of the color of the stigmata depends on the point in the healing process of the blood clot on the bleeding ulcer. This retrospective study evaluates the rebleeding rates associated with various colors of stigmata of recent hemorrhage. Of a total of 623 cases of peptic ulcer bleeding (474 male and 149 female, with a mean age of 59 years old), there were 232 gastric ulcers, 369 duodenal ulcers, and 22 stomal ulcers. Stigmata of recent hemorrhage were found in 387 cases (62%). The overall rebleeding rate for those with gastric ulcers was higher than for those with duodenal ulcers (24.2% versus 16.3%, p<0.05), especially for oozing and sentinel clots, the rebleeding rates for active bleeding, blood clots, sentinel clots, and others were 35%, 24.8%, 17%, and 11.3% respectively. The red clot of stigmata of recent hemorrhage had a slightly higher rebleeding rate than the black clot, but the difference was not statistically important. Furthermore, the 5 duodenal ulcers with white sentinel clots experienced no rebleeding. When comparing the rebleeding rates between groups with massive and minor bleeding, a significantly higher rebleeding rate was found in the massive bleeding group (50.5% versus 6.6%, p < 0.001). It can thus be seen that the different types of stigmata of recent hemorrhage represent different stages in the healing process of a bleeding ulcer. A white sentinel clot had a change of not rebleeding.(ABSTRACT TRUNCATED AT 250 WORDS)