Apoptosis induction by E2F-1 via adenoviral-mediated gene transfer results in growth suppression of head and neck squamous cell carcinoma cell lines.

E2F-1, a transcription factor by discovery, is thought to play a crucial role in regulating G1/S cell cycle progression. Its activity is modulated by complex formation with the retinoblastoma protein and related proteins. Overexpression of E2F-1 has been shown to induce apoptosis in quiescent fibroblasts. We constructed a recombinant E2F-1 adenovirus to test whether an overexpression of E2F-1 in head and neck squamous cell carcinoma cell lines would also induce apoptosis. Two cell lines, Tu-138 and Tu-167, were chosen for use in this study. Both cell lines harbor p53 mutations but express different levels of the retinoblastoma protein. Upon E2F-1 adenovirus infection, both cell lines expressed elevated levels of E2F-1 protein and then activated a pRb-chloramphenicol acetyltransferase reporter construct containing an E2F-1 binding motif. In vitro growth assay demonstrated that growth suppression by the E2F-1 protein was effective on both cell lines. Results from DNA fragmentation and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end-labeling analyses indicated apoptosis induction in cells infected with AdCMV-E2F-1. Moreover, ex vivo experiments in nude mice showed total suppression of tumor growth at sites that received cells infected AdCMV-E2F-1. An in vivo analysis of apoptosis using in situ end-labeling further demonstrated the induction of apoptosis by AdCMV-E2F-1 in tumor-bearing animals. These data indicate that overexpression of E2F-1 via an adenoviral vector suppresses in vitro and in vivo growth of head and neck squamous carcinoma cell lines through induction of apoptosis.

Management of the N(0) neck.

Paramount among the challenges and controversies among the head and neck surgeon is the proper treatment of the N0 neck. Therapeutic intervention for the N0 neck usually involves any of two treatment modalities alone or in combination: surgery or radiation therapy. This article discusses the potential treatment strategies for possible subclinical neck metastasis and the rationale for their use on a site by site basis for head and neck primary tumors.

Gene therapy for head and neck cancer.

Head and neck cancer continues to present a major therapeutic challenge to physicians. Recent advances in molecular or gene therapy have allowed us to reassess these malignancies and consider novel strategies for their management. Since the first clinical trial 5 years ago, it has become apparent that gene transfer is no longer a speculative approach for treating malignancies. Gene therapy involves the introduction of genetic material (DNA) into host cells to induce the expression of the therapeutic product of that gene. This review summarizes the most recent data concerning the use of gene therapy as a treatment strategy for head and neck solid malignancies. A brief overview of the basic concepts of gene therapy as well as future potential applications is also discussed.

Telomerase activity in head and neck tumors after introduction of wild-type p53, p21, p16, and E2F-1 genes by means of recombinant adenovirus.

BACKGROUND: Telomerase (reverse transcriptase) has been shown to play a role in the process of cellular immortalization. METHODS: Telomerase activity was determined in 11 head and neck squamous cell carcinoma (SCCHN) cell lines. The effects of wild-type p16, p21, E2F-1, and p53 genes on telomerase activity were examined by introducing the wild-type genes into two SCCHN cell lines by means of a recombinant adenovirus. RESULTS: We found elevated telomerase activity in 10 of the 11 SCCHN cell lines tested. When we infected Tu-138 and Tu-167 cell lines with wild-type p16, p21, E2F-1, and p53 genes, we found that p16 had little effect on telomerase activity. Both E2F-1 and p53 were known to induce apoptosis in SCCHN cell lines. Significantly reduced telomerase activity by p53 in both cell lines and E2F-1 in Tu-167 cells was in agreement with suppression of cell growth. Overexpression of p21 also exhibited reduction in telomerase activity. CONCLUSIONS: We conclude from this study that overexpression of E2F-1 and p53 can reverse telomerase activity in SCCHN cell lines and that telomerase activity may be involved in cancer cell immortalization.

Kinetic interactions between 4-methylpyrazole and ethanol in healthy humans.

4-Methylpyrazole (4-MP), a potent inhibitor of alcohol dehydrogenase activity, is a candidate to replace ethanol as the antidote for methanol and ethylene glycol intoxications, because it has a longer duration of action and apparently fewer adverse effects. To study a probable mutual inhibitory effect between ethanol and 4-MP on their elimination, two studies were performed in healthy human volunteers using double-blind crossover designs. In study A1 4-MP in the presumed therapeutic dose range of 10 to 20 mg/kg caused a 40% reduction in the rate of elimination of ethanol in 12 subjects given 0.5 to 0.7 g/kg of ethanol. These data suggest that such doses of 4-MP inhibit alcohol dehydrogenase activity in humans in vivo and would be effective at blocking methanol or ethylene glycol metabolism. In study B, ethanol (0.6 g/kg followed by 0.2 g/kg twice) significantly decreased the rate of elimination of 4-MP (5 mg/kg, given intravenously to four subjects). These moderate doses of ethanol also inhibited the rate of urinary excretion of 4-carboxypyrazole, the primary metabolite of 4-MP in humans. Data suggest that ethanol inhibits 4-MP metabolism, thereby increasing the duration of therapeutic blood levels of 4-MP in the body. This mutual interaction may have clinical implications, because most self-poisoned patients have also ingested ethanol. Theoretically, methanol and ethylene glycol might also show such interactions with 4-MP.