Apoptosis and catastrophic cell death in benzo[a]pyrene-transformed human breast epithelial cells

Toluidine blue staining for cell and tissue biology applications

Toluidine blue (TB) staining either alone or in association with other methodologies has the potential to answer a variety of biological questions regarding the human, animal and plant tissues or cells. In this brief review, we not only report the primary use of TB to detect the anionic substrates and availability of their binding sites, but also unveil the resulting applications of TB staining in biological research. Among these applications, the uses of TB staining to identify the changes in chromatin DNA-protein complexes, nucleolus location, and extracellular matrix proteoglycan complexes associated with different physiological and pathological events are described. The usefulness of TB staining to monitor the effects elicited by environmental insults on chromatin and intercalation of drugs into the DNA is also included.

Apoptotic ratios and mitotic abnormalities in 17-β-estradiol-transformed human breast epithelial MCF-10F cells

Treatment of human breast epithelial cells MCF-10F with 17-β-estradiol has been reported to result in E2-transformed cells which have given rise to highly invasive C5 cells that in turn generate tumors in SCID mice. From these tumors, various cell lines, among which C5-A6-T6 and C5-A8-T8, were obtained. Although different phases of the tumorigenesis process in this model have been studied in molecular biology and image analysis assays, no cytological data on apoptotic ratios and mitotic abnormalities have been established to accompany the various steps leading to 17-β-estradiol-treated MCF-10F cells to tumorigenesis. Here we detected that the apoptotic ratio decreases with the transformation and tumorigenesis progress, except for the tumor cell line C5-A8-T8, probably on account of its more intense proliferation rate and a more rapid culture medium consumption. Increased frequency of mitotic abnormalities contributed by triple- and tetrapolar metaphases, and by lagging chromosomes and chromosome bridges observed at the anaphase found by transformation and tumorigenesis progress. However, no difference was found under these terms when the C5-A6-T6 and C5-A8-T8 tumor cell lines were compared to each other. Present findings are in agreement with the nuclear instability and enrichment of dysregulated genes in the apoptotic process promoted by transformation and tumorigenesis in 17-β-estradiol-treated MCF-10F cells.

Nucleus image properties and cell death in MCF-10F cells grown on slide substrates differing in nature and size

The immortalized human breast epithelial cell line MCF-10F is an important tool for studies on experimental tumorigenesis induced by drugs, transfected Ha-ras oncogene, and hormones. Considering that many relevant data have thus far been established only for MCF-10F cells cultivated on glass, and that there are data showing different cell death ratios for tumorigenic cells obtained from benzo[a]pyrene (BP)-transformed MCF-10F cells cultivated on plastic compared with glass, nuclear parameters estimated by image analysis and cell death ratios were compared for cells grown on plastic and glass substrates differing in chamber surface sizes and working culture medium volumes. It was concluded that for slides with a growth size equal to 9.4 cm2, plastic substrate was more advantageous than glass for growing MCF-10F cells because although the apoptotic ratios (AR) for the cells grown on plastic are low as it would be expected for nontransformed cells, they are bigger than those reported for the BP-transformed MCF-10F cells cultivated on the same substrate but closer to those of the BP-transformed MCF-10F cells receiving a normal chromosome 17. In addition, the plastic substrate did not induce variable nuclear image results as those found in the latter. The 0.5-cm2-sized chambers on plastic slides proved to be inadequate for cell nuclear image analysis and cell death studies on account of the variable geometric, densitometric, and textural results and ARs produced and the unpublished consideration of a very slow growth rate generated under this growth condition.

Sulforaphane inhibits human MCF-7 mammary cancer cell mitotic progression and tubulin polymerization

Sulforaphane (SUL), an isothiocyanate derived from hydrolysis of glucoraphanin in broccoli and other cruciferous vegetables, was shown to induce phase II detoxification enzymes, inhibit chemically induced mammary tumors in rodents, and more recently, to induce cell cycle arrest and apoptosis in colon cancer cells. In the present study, we demonstrate that SUL also acts to inhibit proliferation of MCF-7 adenocarcinoma cells from the human breast. Treatment of synchronized MCF-7 cells with 15 micromol/L SUL resulted in significant (P < 0.05) G(2)/M cell cycle arrest (167% of control) and elevated cyclin B1 protein (175% of control) within 24 h. Moreover, 15 micromol/L SUL significantly (P < 0.05) induced phosphorylation of histone H1 (167% of control), blocked cells in early mitosis ( approximately 10-fold increase over control), and disrupted polymerization of mitotic microtubules in vivo. Subsequent exposure of purified bovine brain tubulin to relatively high doses of SUL significantly (P < 0.05) inhibited both tubulin polymerization rate (51% of control) and total tubulin polymerization (78% of control) in vitro. Additionally, polymerization of purified tubulin exposed to isothiocyanate-containing analogs of SUL was similarly inhibited. Taken together, these findings indicate that SUL has mammary cancer suppressive actions involving mitotic cell cycle arrest and suggest a mechanism linked to the disruption of normal tubulin polymerization and/or more subtle effects on microtubule dynamics.

The effects of seasonal weather on the genotoxicity, cytokinetic properties, cytotoxicity and organochemical content of extracts of airborne particulates in Mexico City

Extracted organic material (EOM) from PM10 airborne particles collected during three distinct seasons in Mexico City was assayed for genotoxicity, cytokinetic effects and cytotoxicity. Using sister chromatid exchange (SCE) for genotoxicity, replication index (RI) and mitotic index (MI) for cytokinetics, and microscopic evaluation (cell death) for cytotoxicity on human lymphocytes exposed to increasing concentrations of EOM, this study showed that the extent of genotoxic, cytokinetic, and cytotoxic change caused by pollutants depended at least in part on the seasonal weather. Bioactivated extracts of samplings in April (warm and dry), August (warm and rainy) and November (cool and dry) produced the highest rate of genotoxicity (SCE) in November and the lowest rate in April. Without bioactivation the rates were still highest in November but equally low in April and August. Thus, almost all of the genotoxic responses in the bioactivation experiments during these latter months were from promutagens. However, in November equally large amounts of mutagens and promutagens were present. Cytokinetics (RI and MI) showed steady decreases as the concentration of EOM was increased, independent of bioactivation and weather. Cytotoxicity (cell death) occurred when higher concentrations of EOM were used. EOM was the least cytotoxic in April and most cytotoxic in November. Bioactivation was not required for cytokinetic change and cytotoxicity, suggesting that the agents involved may be different from the genotoxic agents. Using gas chromatography/mass spectroscopy (GC/MS) it could be shown that the type of pollutant chemicals in the EOM also depended on the weather. In particular, all 15 polycyclic aromatic hydrocarbons (PAH) studied were present in November EOM whereas four different PAH were absent in the other 2 months. Generally the amounts were less in the EOM collected in April and August. Conversely, nitro-PAH compounds were greater in number in April EOM but higher in amount in November EOM. The significance of these findings is discussed.