This study addressed many issues related to oral cancer that have been previously discussed in the literature. The demographic, site, stage, histologic, and survival data available for this large number of cases in the NCDB allowed an accurate characterization of the contemporary status of oral cancer in the United States.

No abstract

The distribution of eukaryotic DNA topoisomerase I in the cell has been analyzed at four levels: (i) at the level of the nuclear matrix; (ii) at the cytological level by immunofluorescence of whole cells; (iii) at the electron microscopic level using the protein A/colloidal gold technique; and (iv) at the level of DNA to identify in situ the sequence upon which topoisomerase I is catalytically active. Although topoisomerase I is clearly distributed non‐randomly in the nucleus, the unique distribution of the enzyme is not related to the nuclear matrix. The data support the conclusion that topoisomerase I is heavily concentrated in the nucleolus of the cell; furthermore, particular regions within the nucleolus are depleted of topoisomerase. A technique has been developed which allows isolation and analysis of the cellular DNA sequences covalently attached to topoisomerase. Ribosomal DNA sequences are at least 20‐fold enriched in topoisomerase/DNA complexes isolated directly from a chromosomal setting, relative to total DNA. This is the first direct evidence that topoisomerase I is catalytically active on ribosomal DNA in vivo.

Organ preservation protocols in head and neck squamous cell carcinoma (HNSCC) are limited by tumors that fail to respond. We observed that larynx preservation and response to chemotherapy is significantly associated with p53 overexpression, and that most HNSCC cell lines with mutant p53 are more sensitive to cisplatin than those with wild-type p53. To investigate cisplatin resistance, we studied two HNSCC cell lines, UM-SCC-5 and UM-SCC-10B, and two resistant sublines developed by cultivation in gradually increasing concentrations of cisplatin. The cisplatin-selected cell lines, UM-SCC-5PT and UM-SCC-

Keratin 5 (K5) mRNA and protein are shown to be expressed in normal mammary epithelial cells in culture and are absent from tumor-derived cell lines. To extend these fridings, the full complements of keratins in normal, immortalized, and tumor cells were compared. It is shown here that normal cells produce keratins K5, K6, K7, K14, and K17, whereas tumor cells produce mainly keratins K8, K18, and K19. In immortalized cells, which are preneoplastic or partially transformed, the levels of K5 mRNA and protein are lower than in normal cells, whereas the amount of K18 is increased. Thus, K5 is an important marker in the tumorigenic process, distinguishing normal from tumor cells, and decreased K5 expression correlates with tumorigenic progression. (2, 4-11, 35, 36). Initial studies with keratins extracted from mammary glands showed differences between normal and tumor tissues (2).Immunohistochemical characterization has demonstrated that within the normal duct, basal and lumenal cells can be discriminated by the keratins they express. In these studies, basal cells, lying between the lumenal cells and the basement membrane, were characterized by expression of keratins K5 and K14, which are typical of myoepithelial cells in stratified epithelium, and lumenal cells were characterized by expression of simple epithelial keratins K8, K18, and K19 (12-15).These studies were performed in situ. Keratin expression may not be maintained after disruption of tissue architecture in cell culture. Medium constituents such as vitamin A, cAMP-elevating agents, epidermal growth factor, and other factors are known to affect keratin production (13,(16)(17)(18)37). The development of a medium capable of supporting the growth ofboth tumor and normal breast epithelial cells (1) has allowed us to make a comparison of their keratin profiles independent of medium effects. We have analyzed K5 as a potential marker for normal cells and have reviewed the array of keratins produced by cultured tumor and normal cells. cDNA Library Production. Total RNA was isolated from 184 cells by lysis with guanidinium isothiocyanate, centrifugation over a 5.7 M CsCl cushion, and purification of the resulting RNA pellet (24). Poly(A)+ RNA was purified by oligo(dT) chromatography using standard protocols (ref. 25, pp. 197-198). cDNA was made using the reverse transcriptase of Moloney murine leukemia virus (BRL) according to the supplier's instructions. cDNAs were blunt ended with T4 DNA polymerase, EcoRI linkers were ligated onto the cDNA, and the cDNA was cloned in the EcoRI site of AgtlO. MATERIALS AND METHODSSubtraction and Screening. The first-strand cDNA of 184 mRNA was hybridized with a 5-fold mass excess of 184B5KSVTu2 poly(A)+ RNA to Rot = 6000 mol (of nucleotide)-sec. Nonhybridizing nucleic acid was separated from DNARNA hybrids by chromatography over hydroxylapatite (26) and subjected to a further round of hybridization and hydroxylapatite chromatography. The final product (the "subtracted probe") was labeled by the random primer method (27)...

The activity of the endogenous DNA topoisomerase type I (EC 5.99.1.2) can be quantified in situ by determining how efficiently the enzyme is trapped in a covalent complex with DNA upon lysis of nuclei with detergents. In this way, we can measure relative levels of topoisomerase binding to DNA at native sites in chromatin. Since the majority of topoisomerase I is localized in the nucleolus at rRNA genes, we have evaluated how low levels of actinomycin D, which terminate transcription of rRNA genes, affect the activity of topoisomerase I. In vivo, as well as in vitro with purified topoisomerase I, we have found that drug treatment extends the half-life of the covalent topoisomerase-DNA complex. Actinomycin D stabilizes the nicked intermediate in the cleavage and resealing reaction but otherwise does not significantly alter the strand-passing ability of topoisomerase I. Sequence-specific cleavages by topoisomerase I were stimulated by actinomycin D at identical sequences recognized by the enzyme in the absence of drug. The localization of topoisomerase I in the nucleolus, coupled with the observation that transcription in this organelle is highly sensitive to actinomycin D and camptothecin treatment, leads us to propose that topoisomerase I contributes to actinomycin D inhibition of transcription.A number of reports have suggested that type I DNA topoisomerase (topoisomerase I; EC 5.99.1.2) is involved in transcription based on its association with actively transcribed genes in chromatin (1-6). This association is clearly evident for rRNA genes in animals, yeast, and Tetrahymena (2,3,7). The enzyme is acting catalytically at genes characterized by a high rate of transcription and the heaviest enrichment of topoisomerase I is seen cytologically within the nucleolus (2). Topoisomerase I makes a transient singlestrand break in the sugar-phosphate backbone of DNA (for reviews, see refs. 8 and 9), which introduces a site of rotational freedom in the template; thus, topoisomerase action may provide a swivel point to facilitate entry and/or progression of the bulky transcriptional apparatus. Alternatively, when nascent RNA chains are hybridized to the one strand of template, the topology changes and topoisomerase I may be required to return to (or adjust) the topological ground state. Studies of yeast topoisomerase I mutants suggest that topoisomerase I is not an essential gene (10, 11); however, it seems that topoisomerase II (EC 5.99.1.3) is complementing the defect since topoisomerase II (like topoisomerase I) has been associated with transcriptionally active regions in chromatin (ref. 12; M.T.M. and V. Mehta, unpublished data) and topoisomerase I and II double mutants display a defect in rRNA transcription (7).A better understanding of the involvement of topoisomerase I in transcription can be obtained by analyzing the activity of topoisomerase I catalyzed reactions in a chromosomal setting. The covalent intermediate is a functional reaction intermediate in the process of breaking and rejoining the DNA substra...

Die Selbstorganisation vorgebildeter Alumosilicat‐Nanocluster in Gegenwart von Micellen als Template ermöglicht es, stark saure, unter hydrothermalen Bedingungen stabile mesoporöse Alumosilicate mit geordneten hexagonalen Strukturen herzustellen (MAS‐5). Dieses Beta‐Zeolith‐ähnliche Material zeigt eine hohe katalytische Aktivität beim Cracken von 1,3,5‐Triisopropylbenzol.

A rapid and simple method has been developed which allows detection and isolation of covalent DNA/protein adducts. The method is based upon the use of an ionic detergent, SDS, to neutralize cationic sites of weakly bound proteins thereby resulting in their dissociation off the helix. Proteins tightly or covalently bound to DNA that are not dissociable by SDS, result in the precipitation of the DNA fragment by the addition of KCl; however, free nucleic acid does not precipitate. The method is particularly useful as an analytical tool to titrate the binding of prototypic covalent binding proteins, topoisomerase I and II; thus, quantitation of topoisomerase activity is possible under defined conditions. As an analytical tool the method can be used as a general assay in the purification of as yet unidentified topoisomerases or other activities that bind DNA covalently. Moreover, the technology can be adapted for use in a preparative mode to separate covalent complexes from free DNA in a single step.