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cell death studies on account of the variable geometric, densitometric, and textural results and ARs produced and the unpublished consideration of a very slow growth rate generated under this growth condition.

RNA relocation and persistence of nucleolus-like bodies at mitosis in benzo[a]pyrene-transformed human breast epithelial cells after microcell-mediated transfer of chromosomes 11 and 17

RNA relocation and the incidence of nucleolus-like bodies accumulated during mitosis were studied cytochemically in benzo[a]pyrene (BP)-transformed human breast epithelial MCF-10F cells after microcell-mediated transfer of normal chromosomes 11 and 17. The changes resulting from the transfer of these two chromosomes in tumorigenic MCF-10F cells (BP1-E cell line) were examined, since alterations in these chromosomes are involved in the expression of the transformed and tumorigenic phenotypes in the MCF-10F cell series. In addition, the frequency of nucleolus-like bodies decreases drastically with transformation and tumorigenicity in MCF-10F cells, thus being conceivable that it would be affected in presence of normal chromosomes 11 or 17. The pattern of RNA relocation associated with the mitotic spindle did not vary in the cell lines analyzed. The introduction of chromosome 17 in BP1-E cells either decreased or did not affect the frequency of persistent nucleolus-like bodies. In contrast, in cells which received a normal chromosome 11, the frequency of nucleolus-like bodies was closer to that of non-transformed MCF-10F cells. These results suggest that a normal chromosome 11 but not chromosome 17 contributes to the maintenance of an RNA surplus which accumulates in nucleolus-like bodies during cell division of the human breast epithelial cells, at least in vitro. Some loci which were retained in the BP1-E cells which received a normal chromosome 11 are probably involved with the control of RNA transcript production. Figure 1 on http://www.esacp.org/acp/2001/23-3,4/mello.htm

Carcinogenicity of estrogens in human breast epithelial cells

Epidemiological and clinical evidences indicate that breast cancer risk is associated with prolonged ovarian function that results in elevated circulating levels of steroid hormones. Principal among these is estrogen, which is associated with two important risk factors, early onset of menarche and late menopause. However, up to now there is no direct experimental evidence that estrogens are responsible of the initiation of human breast cancer. We postulate that if estrogens are causative agents of this disease, they should elicit in human breast epithelial cells (HBEC) genomic alterations similar to those exhibited by human breast cancers, such as DNA amplification and loss of genetic material representing tumor suppressor genes. These effects could result from binding of the hormone to its nuclear receptors (ER) or from its metabolic activation to reactive metabolites. This hypothesis was tested by treating with the natural estrogen 17beta-estradiol (E2) and the synthetic steroid diethylstilbestrol (DES) MCF-10F cells, a HBEC line that is negative for ER. Cells treated with the chemical carcinogen benzo (a) pyrene (BP) served as a positive control of cell transformation. BP-, E2-, and DES-treated MCF-10F cells showed increases in survival efficiency and colony efficiency in agar methocel, and loss of ductulogenic capacity in collagen gel. The largest colonies were formed by BP-treated cells, becoming progressively smaller in DES- and E2-treated cells. The loss of ductulogenic capacity was maximal in BP-, and less prominent in E2- and DES-treated cells. Genomic analysis revealed that E2- and DES-treated cells exhibited loss of heterozygosity in chromosomes 3 and 11, at 3p21, 3p21-21.2, 3p21.1-14.2, and 3p14.2 14.1, and at 11q23.3 and 11q23.1-25 regions, respectively. It is noteworthy that these loci are also affected in breast lesions, such as ductal hyperplasia, carcinoma in situ, and invasive carcinoma. Our data are the first ones to demonstrate that estrogens induce in HBEC phenotypic changes indicative of cell transformation and that those changes are associated with significant genomic alterations that might unravel new pathways in the initiation of breast cancer.