Wilhelm bernhard workshop on the cell nucleus

NUCLEAR CHANGES IN BREAST CANCER CELLS DURING EARLY PHASES OF CELL DEATH AND CELL GROWTH.

Losa G.A.^1,2, Castelli C.¹, Nonnenmacher T.F. <sup>1,3

1</sup>Institute of Scientific Interdisciplinary Studies, Locarno, and ²Faculty of Sciences, University of Lausanne, Switzerland; ³Department of Mathematical Physics, University of Ulm, Germany.
Fractal morphometry and grey level co-occurrence matrix analysis (GLCM) were applied to investigate early phases of cell growth and cell death in human breast cancer cells. Changes in the ultrastructural complexity of external perinuclear membrane (ENM), eu- and heterochromatins and in the textural features of selected nuclear domains (ROIs) were assessed in estrogen-insensitive SK-BR-3 breast cancer cells induced to apoptosis by 1 μM calcimycin, an apoptogenic Ca²⁺ ionophore. The reorganization of ENM and nuclear membrane-bound heterochromatin (NMBHC) was also established in estrogen-sensitive MCF-7 breast cancer cells triggered by 17-ß-estradiol and glucocorticoid dexamethasone. SK-BR-3 cells entered the early stage of apoptosis after 12-24 h of calcimycin treatment and had fractal dimension (FD) values of perinuclear membranes lower than in untreated cells, indicating a loss of morphological complexity. Changes of the chromatin texture within the entire nucleus and in ROIs were even more pronounced in treated cells as evaluated by decreased fractal dimensions and GLCM textural parameters. At the opposite, soon after a short treatment (five minutes) with 17-beta-estradiol, MCF-7 cells displayed an enhanced ultrastructural irregularity of NMBHC (higher FD values) while reduced with dexamethasone (lower FD) when compared to NMBHC from untreated cells. Unexpectedly, neither steroid modified ENM ultrastructure in these cells. Both fractal and GLCM analyses confirmed that the nuclear morphological reorganization imputable to a loss of structural complexity occurred in the early stage of apoptosis of SK-BR-3 cells while an increase was measured at the beginning of proliferation in estrogen-sensitive MCF-7 cells. These morphological-ultrastructural traits within the entire nucleus and in selected nuclear domains occurred well before the detection of conventional cellular markers and were accompanied by enzymatic changes at the cell periphery.