Extracellular
glycoproteins of the
laminin family are essential components of basement membranes involved in a number of biological processes, including tissue differentiation, wound healing, and
tumorigenesis. We present the first comprehensive study of promoter methylation status of the genes encoding
laminin chains in normal tissues (peripheral blood leucocytes, buccal epithelial cells, autopsy breast tissue samples) and in
breast carcinoma samples. Based on the results of this study, we divide
laminin genes into three categories. Genes, constitutively methylated in breast tissues include LAMA3A, LAMB2, LAMB3, and LAMC2. Genes prone to abnormal methylation in
breast carcinoma include LAMA1, LAMA2, LAMA3B, LAMA4, LAMB1, and LAMC3. Genes that are rarely if ever methylated in
breast carcinoma include LAMA5 and LAMC1. The constitutively methylated group includes all of the genes that encode subunits of
laminin-5 (the historical name of
laminin 332), the promoters of which were previously considered unmethylated in normal tissues and prone to abnormal methylation in
breast cancer.