TP73 DNA methylation and upregulation of ΔNp73 are associated with an adverse prognosis in breast cancer

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.

Abstract P5-16-05: Comparative analysis of the immunohistochemical profile of ductal carcinoma in situ to invasive ductal carcinoma

Introduction:

The molecular subtypes have classified invasive breast carcinomas in diverse entities with different clinical behaviors, but the prevalence of these subtypes in ductal carcinoma in situ (DCIS) has not been evaluated in detail. The main objectives of this study were to compare proteomic expression profiles of DCIS and invasive ductal carcinoma (IDC) by immunohistochemistry (IHC), classify them according to the molecular subtypes and evaluate the relationship between the expression of the biological markers and the tumoral grade.

Methods:

We assessed the frequency of expression of ER, PR, HER2, proliferation markers (PCNA or Ki67), Bcl-2 and p53 in 107 DCIS and compared them with the expression of 682 IDC. They were classified according to molecular subtypes. We evaluated the relationship between the expression of these markers and the nuclear and histological grades of DCIS and IDC respectively.

Results

The expression of Bcl-2 and PR was significantly more frequent in the DCIS group (p = 0.0461 and p = 0.0001 respectively). The IDC showed significantly increased values for cell proliferation markers and mutated p53 (p < 0.0001 and p = 0.0062 respectively). The prevalence of ER and HER2 was similar in both groups (p = 0.0912 and p = 0.4686 respectively).

Clinico-pathological parameters and biomarkers expression DCISIDCPN107682 Age (mean)52.75 years55.79 years0.0219Tumoral size (mean)1.62 cm2.23 cm<0.0001Grade 144 (41.12%)95 (13.92%)<0.0001Grade 229 (27.10%)277 (40.61%)0.0076Grade 334 (31.78%)310 (45.45%)0.0086ER positive82 (76.63%)467 (68.47%)0.0912PR positive70 (65.42%)373 (54.69%)0.0461HER2 positive19 (17.78%)101 (14.81%)0.4686Proliferation markers high65 (60.75%)206 (30.21%)<0.0001Bcl-2 positive84 (78.51%)405 (59.38%)0.0001p53 mutated33 (30.84%)307 (45.01%)0.0062

The luminal A subtype was more common in DCIS (p = 0.0003), whereas luminal B no-HER2 and triple negative were more prevalent in IDCs (p = 0.0195 and p = 0.0351 respectively). There were no differences in the frequency of luminal B-HER2 and HER2 positives (p = 0.3279 and p = 1.0000 respectively).

Prevalence of molecular subtypes. DCISIDCPLuminal A46 (43%)172 (25.22%)0.0003Luminal B32 (29.91%)288 (42.23%)0.0195Luminal B-HER2+11 (10.28%)50 (7.33%)0.3279HER28 (7.47%)51 (7.48%)1.0000Triple Negative10 (9.34%)121 (17.74%)0.0351

In relation to nuclear grade of DCIS, no differences were detected with respect to the expression of ER, Bcl-2 and mutated p53 (p = 0.3691, p = 0.8136 and p = 0.3138 respectively). Proliferation markers increased significantly with increasing nuclear grade (p <0.0001). PR was mostly expressed in DCIS grade 1 and HER2 in grade 3, but this was not statistically significant (p = 0.0741 and p = 0.0851 respectively). With regard to histological grade of IDCs, there were a higher frequency of ER, PR, Bcl-2 in grades 1 (p <0.0001). G3 carcinomas showed increased expression of HER2, proliferation markers and mutated p53 (p <0.0001, p <0.0001 and p = 0.0110 respectively).

Conclusions:

The DCIS presents significant differences in tumor subtypes compared with IDC. The lower frequency of triple negative tumors and Luminal B-HER2-, lower expression of mutated p53 and lower degree of proliferation, suggest a less aggressive behavior of DCIS.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-16-05.

DNA methylation index and methylation profile of invasive ductal breast tumors

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.

Methylation profile of triple-negative breast carcinomas

Breast cancer is a group of clinically, histopathologically and molecularly heterogeneous diseases, with different outcomes and responses to treatment. Triple-negative (TN) breast cancers are defined as tumors that lack the expression of estrogen receptor, progesterone receptor and epidermal growth factor receptor 2. This subgroup accounts for 15% of all types of breast cancer and its prevalence is higher among young African, African-American and Latino women. The hypermethylation of CpG islands (CpGI) is a common epigenetic alteration for suppressing gene expression in breast cancer and has been shown to be a key factor in breast carcinogenesis. In this study we analyzed the hypermethylation of 110 CpGI within 69 cancer-related genes in TN tumors. For the methylation analysis, we used the methyl-specific multiplex-ligation probe amplification assay. We found that the number of methylated CpGI is similar between TN and non-TN tumors, but the methylated genes between the groups are different. The methylation profile of TN tumors is defined by the methylation of five genes (that is, CDKN2B, CD44, MGMT, RB and p73) plus the non-methylation of 11 genes (that is, GSTP1, PMS2, MSH2, MLH1, MSH3, MSH6, DLC1, CACNA1A, CACNA1G, TWIST1 and ID4). We conclude that TN tumors have a specific methylation profile. Our findings give new information for better understanding tumor etiology and encourage future studies on potential drug targets for triple-negative breast tumors, which now lack a specific treatment.

Aberrant DNA methylation of cancer-related genes in giant breast fibroadenoma: a case report

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.

Integration of estrogen and progesterone receptors with pathological and molecular prognostic factors in breast cancer patients

In this study we have examined biopsies from women with localized primary breast cancer to investigate the prognostic performance of estrogen receptors (ER) and progesterone receptors (PR) for estimating the metastatic probability of the patients, and to explore whether discrimination gets better by combining clinicopathological and other molecular parameters into a score. This prospective study involved 205 patients with a median follow-up of 5 y. Among the evaluated clinicopathological data were: patient's age; tumor size; axillary lymph node involvement; and tumor grade. The most representative tumor samples were derived to a single laboratory for immunohistochemical evaluation of the following molecular markers: ER, PR, proliferating cell nuclear antigen (PCNA), p53 protein product, erbB-2 (HER-2/neu) oncoprotein, and P170 glycoprotein (mdrl gen product). Distant metastases (study endpoint) appeared in 19.5% (40/205) of the patients, most of these patients presented a mixture of poor, regular and good prognostic factors. Disease-free survival analysis procedures (Kaplan-Meier method) identified tumor size, axillary lymph node involvement, tumor grade, receptor status, PCNA, p53, erbB-2 and P170 as useful prognostic factors. Proportional hazard regression analysis (Cox) identified in order of importance erbB-2, tumor size, receptors status, tumor grade and PCNA as useful prognostic factors. To facilitate the evaluation of the prognostic factors, a practical and simple score system was derived. A high pathological score identified 65% of the patients that developed distant metastases, while a high molecular score was obtained in 57% of patients with metastatic disease. There was a significant improvement in the diagnosis of probability of being with distant metastases when the pathological score was combined with the molecular score, 82% of the patients with distant metastases showed an elevated combined score. Validation of this scoring system will need further larger studies (validation set as opposed to the training set used in the present study). Due to the complexity of events in cancer, the evaluation of a combination of prognostic factors should be of value to clinicians to make a more objective estimate of the prognosis of individual breast cancer patients.