Morphological effects of natural retinoids on human mammary carcinoma cell lines in monolayer culture.

The morphological effects of treatment with the natural retinoids were studied using scanning electron microscopy (SEM) utilizing both secondary electron imaging and backscatter electron imaging. Three human cell lines originally isolated from metastatic infiltrating adenocarcinomas of the breast and one cell line isolated from human milk were treated with various concentrations of retinol and retinoic acid. Growth inhibition curves showed that all three malignant cell lines were moderately to extremely sensitive to treatment with both retinoids. The nontumorigenic cell line, HBL-100, derived from human milk was only slightly or not affected by treatment. Morphological changes with retinoid treatment varied with the cell lines examined. Two tumorigenic cell lines, MDA-MB-231 and CaMa-15, showed alteration in cell shape. CaMa-15 and MCF-7 showed a loss in number of surface microvilli while MDA-MB-231 gained microvilli. HBL-100 cells exhibited an increased number of pits or lacunae on the cell surfaces with treatment. These findings suggest that treatment with retinoids does not result in uniform morphological changes and that the changes observed vary with the cell line examined.