Expression of DNA methylation-related proteins in invasive lobular carcinoma of breast: comparison to invasive ductal carcinoma

Abstract

Purpose: We aimed to compare the expression of DNA methylation-related proteins in invasive lobular carcinoma (ILC) of breast with those of invasive ductal carcinoma (IDC) of breast and to assess its potential clinical application. Methods: Immunohistochemical staining of DNA methylation-related proteins (5-meC, DNMT1, DNMT3B and ISL-1) was applied to tissue microarrays generated from 108 ILCs and 203 IDCs. Protein expression and its correlation with clinicopatholgic variables were statistically analyzed. Results: ISL-1 and DNMT3B were highly expressed in ILC (p<0.001) and tumoral 5-meC was highly expressed in IDC (p=0.006). DNMT1 (p<0.001) showed higher expression rate in luminal A type ILC. ISL-1 and DNMT3B showed higher expression rate in both luminal A type and luminal B type of ILC (p<0.05). In IDC, tumoral 5-meC commonly showed high positivity (p=0.039). On univariate analysis, shorter disease-free survival of ILC was associated with DNMT1 high positivity (p=0.001) and ISL-1 positivity (p=0.018). Conclusion: DNA methylation-related proteins are differentially expressed in ILC and IDC, and DNMT1, DNMT3B and ISL-1 show high expression rate in ILC.