Neoplasia and cytogenetic abnormalities

Assessment of Unstimulated Whole Salivary Tumor Necrosis Factor Alpha (TNF-α) and Cellular Micronuclei Levels in Snuff (Naswar) Users and Non-Users for Early Diagnosis of Oral Squamous Cell Carcinoma

The aim of the study was to investigate the unstimulated whole saliva (UWS) tumor necrosis factor alpha (TNF-α) and cellular micronuclei in snuff dippers (Naswar) compared to healthy control subjects. The case control study was conducted over 9 months at a tertiary care center. Sixty patients were divided into two groups: Snuff dippers (SD) (Naswar) and non-snuff dippers (NSD) (control subjects). The included self-reported SD used Snuff twice daily for more than 12 months. UWS was collected and salivary TNF-α assessment was performed using enzyme-linked immunosorbent assay (ELISA). For cellular micronuclei, buccal mucosa was brushed to obtain cells in Naswar users, fixed with a dibutylphthalate polystyrene xylene (DPX) mounting to view micronuclei. Means and standard deviations were compared using the t-test and outcomes were related using Pearson correlation, considering p ≤ 0.05 as significant. The mean age of participants was 38.85 ± 11.56 years. The mean duration of snuff use was 20.43 ± 12.79 years and the common site for Naswar placement was the lower vestibule (n = 19, 63.3%). TNF-α levels among SD were 9.6 ± 3.3 pg/mL, which were significantly higher than levels in NSD, 5.2 ± 3 pg/mL (p < 0.05). The number of cellular micronuclei in SD was 30.7 ± 7.8, which was comparatively higher than in NSD, which was 9.2 ± 3.3 (p < 0.05). The duration of snuff use was positively correlated to TNF-α levels (p = 0.048) rather than the micronuclei number (p = 0.97). SD showed higher levels of TNF-α and cellular micronuclei compared with NSD (control subjects); a positive correlation was shown with the duration of snuff use. We conclude that TNF-α and micronuclei are potential salivary biomarkers for an oral biological effect in snuff (Naswar) users.

Effects of griseofulvin in medium-term liver carcinogenesis assay and peripheral blood micronucleus test in rat

Published data have suggested a possible link between the tumor promoting activity and the aneugenic properties of griseofulvin. The present study was conducted to explore this relationship. Griseofulvin was evaluated both for its potential promoting activity in liver carcinogenesis in partially hepatectomized F344 male rats initiated by diethylnitrosamine and for its genotoxic potential in the peripheral blood micronucleus assay. Rats were treated daily with 2,000 mg/kg body weight by oral gavage for 12 weeks in the medium-term carcinogenesis bioassay. GST-P-positive foci (mean number and surface area) and altered cell foci were compared in the liver of rats treated with griseofulvin alone, diethylnitrosamine alone,and griseofulvin in addition to diethylnitrosamine by using immunohistochemical and histopathological evaluation, respectively. This evaluation allowed the conclusion that griseofulvin did not initiate the carcinogenic process but rather had a potential in the liver for tumor promoting activity. Griseofulvin was found to be negative in the rat peripheral blood micronucleus test when given at a daily oral dose of 2,000 mg/kg body weight for at least 3 weeks.

The in vitro micronucleus test: a multi-endpoint assay to detect simultaneously mitotic delay, apoptosis, chromosome breakage, chromosome loss and non-disjunction

Genotoxicity testing aims to detect a large range of genetic damage endpoints and evaluate such results in context of cell survival. The cytokinesis block micronucleus test offers the advantage to provide simultaneously information on both cell cycle progression and chromosome/genome mutations. Indeed, 1. frequencies of cytokinesis-blocked binucleated cells (and polynucleated) are good estimators of the mitotic rate; 2. frequencies of apoptotic figures in mononucleated and binucleated cells provide a measure for cell death before or after cell division; 3. combination of fluorescence in situ hybridization (FISH) for centromere/telomeres and micronucleus scoring allows discrimination between clastogenic and aneugenic events; 4. detection of FISH signals for chromosome specific sequences in both macronuclei and micronuclei, discriminates between aneuploidy due to chromosome non-disjunction or to chromosome loss. The cytokinesis block in vitro micronucleus test is thus a cytogenetic multi-test providing mechanistic information with a simple, rapid, objective, microscopical analysis.

Aneuploidy and consistent structural chromosome changes associated with transformation of Syrian hamster embryo cells

To gain a better understanding of the role of specific numerical and structural chromosome changes in the multistage process of transformation of Syrian hamster embryo (SHE) cells, we analyzed seven benzo(a)pyrene (BP)-induced immortal SHE cell lines, and one spontaneously immortalized cell line. In addition, we analyzed chromosome changes in early passage tumor-derived cell lines induced by injection of four immortalized cell lines into neonate hamsters. Of particular interest was the observation of a deletion in the short arm of chromosome 2 in four of the seven BP-immortalized cell lines. Other types of alterations in chromosome 2 were observed in two other cell lines. Loss of one copy of chromosome 16 was also observed in more than 90 to 100% of the cells in three of seven BP-immortalized cell lines. In contrast, the only chromosome alteration seen in the spontaneously immortalized cell line was a deletion in the short arm of chromosome 20. Genetic instability, as indicated by increased numerical or structural chromosome changes, was observed in all tumor-derived cell lines compared to the immortal cell line from which they originated. These results, along with previous reports in the literature, suggest that alterations in specific chromosomes, like chromosome 2, may be involved in transformation of SHE cells.

Increased spindle resistance to antimicrotubule agents in cells prone to chromosomal nondisjunction

The cytological behavior of the spindle apparatus was studied in cells prone to nondisjunction (ND), i.e., PHA-stimulated lymphocytes derived from children suffering from different types of neoplasia. These cells, which exhibited a high frequency of nonspecific aneuploidy, revealed an increased resistance of the spindle fibers to colchicine, podophyllotoxin, and cold, which was several times that of lymphocytes derived from healthy children. The results are in accord with previous findings showing a high resistance of spindle microtubules to the antimicrotubular agents colchicine, podophyllotoxin, vinblastine, and cold in PHA-stimulated lymphocytes derived from individuals prone to meiotic ND. It is therefore assumed that high resistance of the spindle apparatus to antimicrotubule agents characterizes cells at high risk for aneuploidy, and possibly, the overstabilized spindle fibers are responsible for failure of chromosomal disjunction.

Chromosomal changes in cell lines from mouse tumors induced by nickel sulfide and methylcholanthrene

Rhabdomyosarcomas were induced in mice by intramuscular injections of crystalline nickel sulfide and 3-methylcholanthrene. At early passage, karyotypes were performed by G-banding for four nickel sulfide cell lines and for three 3-methylcholanthrene cell lines. Six cell lines were near-diploid and one nickel sulfide line was near-tetraploid. Three of the nickel sulfide cell lines were characterized by a rearranged marker chromosome which was present in a majority of the cells of each line. The rearrangements leading to the formation of marker chromosomes were different in each nickel sulfide cell line but involved chromosome 4 in two of the nickel sulfide cell lines. Extra copies of chromosome 15 were present in two nickel sulfide cell lines. Possible rearrangement and/or gene activation was examined for the c-mos oncogene on chromosome 4 and the c-myc oncogene on chromosome 15, but no alteration or activation was observed. None of the 3-methylcholanthrene cell lines contained rearranged marker chromosomes; however, one MCA cell line did contain large numbers of double minutes. In all cell lines, minichromosomes (small atypical acrocentric chromosomes) were observed that contained distinct centromeric regions but no other G-positive bands.

Gene dosage mutants at adenine phosphoribosyltransferase locus induced by colcemid in Chinese hamster V79-AP4 cells

Pseudodiploid Chinese hamster V79-AP4 cells, functionally diploid at the adenine phosphoribosyltransferase (aprt) locus, were treated with colcemid, a well-known aneuploidizing agent, under various experimental conditions. Aneuploid and tetraploid cells and variants resistant to 10 micrograms/ml of 2,6-diaminopurine (DAP), which selects for presumptive aprt+/- heterozygotes in the untreated cells, were induced. Many of the induced variants were hypotetraploid with three (rather than four) chromosomes carrying the aprt gene. Dot-blot and Southern analysis of the DNA of these clones confirmed that they had three copies of the aprt gene. Their APRT specific enzymatic activity was 60-80% of that of wild-type V79-AP4. The results of these and other experiments suggest that in these variants resistance to DAP is due to an altered aprt gene dosage and point to a possible genetic effect of colcemid and other aneuploidizing agents in somatic mammalian cells.

Mutation as a cause of genetic disease

Mutational changes can be conveniently classified into two sorts: those that appear to involve single genes and are generally referred to as gene mutations, and those that involve chromosomal segments containing many genes, or even whole chromosomes, and are referred to as chromosomal mutations. Both of these kinds of mutation occur in germ-cell lineages and contribute substantially to inherited disease, or pre-disposition to disease, and both also occur in somatic cells and contribute to acquired disease. The mutation rates for inherited disease ascribed to mutation in a single gene differ for different genes and are age-dependent. Moreover, a single disease entity, such as haemophilia B, may be the result of any one of a number of different alterations within the gene responsible for the disease. The mutation rate for inherited chromosomal mutation is also age-dependent, particularly so in the case of mutations involving alterations in chromosome number. Studies in experimental animals demonstrate that exposure to physical or chemical mutagens results in increasing the incidence of inherited gene and chromosomal mutations. However, such increases have not been unequivocally demonstrated in human populations exposed to known mutagens. Studies on mutation in human lymphoid or epithelial somatic cells clearly demonstrate an increased frequency in cells taken from people exposed to ionizing radiations or chemical mutagens or in cells exposed in vitro. The consequences of such mutations will depend upon their nature and the origins and functions of the cells in which they occur. Of particular importance are mutations influencing cell growth and proliferation, and both gene and chromosomal mutations are implicated as causal factors in the development of human cancers.

Flow cytometric DNA ploidy in colorectal adenomas and family history of colorectal cancer

Flow cytometric DNA ploidy of colorectal adenomas resected from 34 patients and the corresponding patient family history in first-degree relatives were evaluated. The samples with at least two separate G0-G1 peaks were defined as DNA aneuploid. The correlation between DNA ploidy and family history was evaluated using two-by-two contingency tables. This correlation was highly statistically significant: seven of nine patients (78%) with positive family histories, and five of 25 (20%) with negative family history had adenomas with DNA aneuploid stemlines (P = 0.0068). The overall DNA aneuploidy incidence was 12 in 34 cases (35.2%). The combined information of DNA aneuploidy and positive family history of colorectal cancer in patients with colorectal adenomas may help to better understand the process of colon carcinogenesis and to identify patients who have a higher risk for developing a malignancy.

Size variation in kinetochores of human chromosomes

Aneuploidy, the loss or gain of chromosomes from cells, is likely in many cases to involve the kinetochore, the site of attachment of spindle microtubules. We analyzed human fibroblast cells with antikinetochore-antibody indirect immunofluorescence, and noted an apparent heterogeneity in the sizes of kinetochores among different chromosomes. The Y chromosome in particular always showed minute kinetochores, an observation which was quantified and substantiated using computer-assisted image analysis. This finding, combined with literature reports about in vivo and in vitro involvement of the Y chromosome in aneuploidy, was used to frame a novel hypothesis about the generation of chromosome imbalance.