Effects of steroid hormones on nuclear membrane and membrane-bound heterochromatin from breast cancer cells evaluated by fractal morphometry.

Objective: To evaluate the effect of steroid hormones on the ultrastructure of nuclear heterochromatin and perinuclear membranes in human MCF-7 breast cancer cells.

Study Design: MCF-7 cells were cultured briefly (five minutes) in the presence of 10(-9) M estrogen 17 beta-estradiol, a stimulator of cell proliferation and/or 10(-9) M glucocorticoid dexamethasone. Changes in the morphologic complexity of nuclear membrane-bound heterochromatin (NMBHC) and nuclear membranes (ENM) were assessed by means of the fractal capacity dimension, D, a noneuclidean geometric descriptor of complex, irregular bodies.

Results: 17 beta-estradiol (10(-9) M) enhanced the ultrastructural irregularity of NMBHC, as documented by the increased value of D, whereas dexamethasone (10(-9) M) reduced it when compared to NMBHC from untreated MCF-7 control cells. In contrast, neither steroid modified ENM ultrastructure. Changes in the nuclear heterochromatin complexity induced by estrogen 17 beta-estradiol occurred concomitantly with functional changes at the cell periphery, such as activation of the phospholipase C, a cell membrane-associated enzyme involved in signal transduction. Dexamethasone reduced the ultrastructural complexity of NMBHC without affecting functional processes.

Conclusion: Fractal morphometry proved its usefulness in quantifying early ultrastructural changes in nuclear components induced in MCF-7 cells by steroid hormones, 17 beta-estradiol and dexamethasone.