ABSTRACT
AIM: Accumulated evidence suggests that aberrant methylation of the TP73 gene and increased levels of ΔNp73 in primary tumours correlate with poor prognosis. However, little is known regarding the transcriptional and functional regulation of the TP73 gene in breast cancer. The aim of the present study was to determine the expression of the ΔNp73 isoform, its relationship with DNA methylation of TP73 and their clinical prognostic significance in breast cancer patients. METHODS: TP73 gene methylation was studied in TCGA datasets and in 70 invasive ductal breast carcinomas (IDCs). The expression of p73 isoforms was evaluated by immunohistochemistry (IHC) and Western blot and correlated with clinicopathological variables and clinical outcome. RESULTS: We observed that the methylation of diverse CpG islands of TP73 differed significantly between molecular subtypes. An inverse correlation was found between p73 protein expression and the methylation status of the TP73 gene. The expression of exon 3' of p73 (only expressed in ΔNp73) was significantly higher in patients with wild-type p53. Immunohistochemical analysis revealed that all p73 isoforms were localised in both the nuclear and cytoplasmic compartments. We confirmed a positive association between the expression of ∆Np73 and high histological grade. CONCLUSIONS: Our findings suggest that high expression of ΔNp73 could be used to determine the aggressiveness of IDCs and could be incorporated in the pathologist's report.
Subject(s)
Breast Neoplasms/diagnosis , Carcinoma, Ductal, Breast/diagnosis , CpG Islands/genetics , Tumor Protein p73/genetics , Breast/metabolism , Breast/pathology , Breast Neoplasms/metabolism , Breast Neoplasms/pathology , Carcinoma, Ductal, Breast/metabolism , Carcinoma, Ductal, Breast/pathology , DNA Methylation , Disease-Free Survival , Female , Humans , Immunohistochemistry , Prognosis , Protein Isoforms , Tumor Protein p73/metabolismABSTRACT
Breast carcinogenesis is a multistep process that involves both genetic and epigenetic alterations. Identification of aberrantly methylated genes in breast tumors and their relation to clinical parameters can contribute to improved diagnostic, prognostic, and therapeutic decision making. Our objective in the present study was to identify the methylation status of 34 cancer-involved genes in invasive ductal carcinomas (IDC). Each of the 70 IDC cases analyzed had a unique methylation profile. The highest methylation frequency was detected in the WT1 (95.7%) and RASSF1 (71.4%) genes. Hierarchical cluster analysis revealed three clusters with different distribution of the prognostic factors tumor grade, lymph node metastasis, and proliferation rate. Methylation of TP73 was associated with high histological grade and high proliferation rate; methylation of RARB was associated with lymph node metastasis. Concurrent methylation of TP73 and RARB was associated with high histological grade, high proliferation rate, increased tumor size, and lymph node metastasis. Patients with more than six methylated genes had higher rates of relapse events and cancer deaths. In multivariate analysis, TP73 methylation and the methylation index were associated with disease outcome. Our results indicate that methylation index and methylation of TP73 and/or RARB are related to unfavorable prognostic factors in patients with IDC. These epigenetic markers should be validated in further studies to improve breast cancer management.
Subject(s)
Breast Neoplasms/genetics , Carcinoma, Ductal, Breast/genetics , CpG Islands , DNA Methylation , Gene Expression Regulation, Neoplastic , Adult , Breast/metabolism , Breast/pathology , Breast Neoplasms/diagnosis , Breast Neoplasms/pathology , Carcinoma, Ductal, Breast/diagnosis , Carcinoma, Ductal, Breast/pathology , Cluster Analysis , DNA-Binding Proteins/genetics , Female , Humans , Middle Aged , Nuclear Proteins/genetics , Prognosis , Receptors, Retinoic Acid/genetics , Tumor Protein p73 , Tumor Suppressor Proteins/genetics , WT1 Proteins/geneticsABSTRACT
INTRODUCTION: Giant fibroadenoma is an uncommon variant of benign breast lesions. Aberrant methylation of CpG islands in promoter regions is known to be involved in the silencing of genes (for example, tumor-suppressor genes) and appears to be an early event in the etiology of breast carcinogenesis. Only hypermethylation of p16INK4a has been reported in non-giant breast fibroadenoma. In this particular case, there are no previously published data on epigenetic alterations in giant fibroadenomas. Our previous results, based on the analysis of 49 cancer-related CpG islands have confirmed that the aberrant methylation is specific to malignant breast tumors and that it is completely absent in normal breast tissue and breast fibroadenomas. CASE PRESENTATION: A 13-year-old Hispanic girl was referred after she had noted a progressive development of a mass in her left breast. On physical examination, a 10 × 10 cm lump was detected and axillary lymph nodes were not enlarged. After surgical removal the lump was diagnosed as a giant fibroadenoma. Because of the high growth rate of this benign tumor, we decided to analyze the methylation status of 49 CpG islands related to cell growth control. We have identified the methylation of five cancer-related CpG islands in the giant fibroadenoma tissue: ESR1, MGMT, WT-1, BRCA2 and CD44. CONCLUSION: In this case report we show for the first time the methylation analysis of a giant fibroadenoma. The detection of methylation of these five cancer-related regions indicates substantial epigenomic differences with non-giant fibroadenomas. Epigenetic alterations could explain the higher growth rate of this tumor. Our data contribute to the growing knowledge of aberrant methylation in breast diseases. In this particular case, there exist no previous data regarding the role of methylation in giant fibroadenomas, considered by definition as a benign breast lesion.
