Freeze-fracture morphometry on normal and cancer breast tissues

A stereological procedure to evaluate the number of particles per unit surface area (Np/micron2) and the particle density distribution in both protoplasmic (pf) and external face (ef) of the plasma membrane was applied on freeze-fracture preparations of human breast tissues with invasive carcinoma and with non-neoplastic lesions. A significant higher intramembrane particle density was recorded on the protoplasmic face of plasma membrane of epithelial cells from non-neoplastic breast tissues (2999 +/- 720 Np/micron2) compared to the particle density on the corresponding face of cancer cells (911 +/- 608 Np/micron2). Moreover, in the latter cells the external face had more than 50% of the surface area totally smooth while residual particles were often aggregated. The reduction of integral glycoproteins in the plasma membrane of malignant tissues fits apparently well with the increased activity of the methyltransferase-I, an enzyme methylating membrane phospholipids. These findings suggest a distribution of constituents and a lipid environment peculiar for the plasma membrane of breast cancer cells.