This study determines the role of
laminin-1 in promoting metastatic colonization during
breast cancer. For this purpose, human mammary epithelial cell lines representing normal (MCF-10A),
adenocarcinoma (MCF-7), and malignant
carcinoma (MDA-MB-231) were propagated in 3-dimensional cultures composed of
laminin-1,
collagen I, or mixtures of the two, and analyzed by Western blot, immunocytochemistry, semiquantitative reverse transcription polymerase chain reaction, and methylation-specific PCR. Here we demonstrate that
laminin-1 decreases methylation of the
E-cadherin promoter, resulting in increased
mRNA and
protein expression for malignant mammary epithelial cells. This decreased methylation is associated with dramatic changes in the cellular and structural morphology as well as a 70-fold decrease in
DNA methyltransferase 1 (DNMT1) and a 6-fold decrease in
cadherin 11 protein expression. To control for specificity of
laminin-1 interactions, cells were also cultured on 2-dimensional
plastic substrata and
collagen I
hydrogels for analysis, and the MCF-10A and MCF-7 were used as nonmalignant controls. Using a 3-dimensional model, we present evidence that
laminin-1 is capable of inducing epigenetic change by inhibiting expression of DNMT1 and preventing methylation of the
E-cadherin promoter, resulting in
E-cadherin expression and the formation of cell-cell bonds in malignant
carcinoma.