Methylation of miR124a-1, miR124a-2, and miR124a-3 in Hodgkin lymphoma.

Deregulation of the microRNA miR124a by DNA methylation has been implicated in various malignancies, but no study reported its methylation status in Hodgkin lymphoma (HL). We evaluated the methylation of the three loci encoding for miR124a using methylation-specific PCR in 64 HL patients and 15 reactive lymph nodes obtained from patients with nonmalignant diseases. Results were correlated with clinicopathological parameters. Methylation rates of miR124a-1, miR124a-2, and miR124a-3 in HL were 17, 50, and 28%, respectively. None of the nontumoral samples showed aberrant hypermethylation in any of the miR tested. In HL cases, we found that miR124a-1 methylation correlates with high-risk International Prognostic Score (IPS) (score >3, p = 0.04) and that miR124a-2 methylation was more frequent in children (82.3%, p = 0.006) and men (63.9%, p = 0.01). Methylation of miR124a-3 was associated with advanced Ann-Arbor stages (p = 0.007). The survival analysis showed that methylation of at least one of the miR124a genes was associated with shortened event-free survival in univariate (p = 0.03) and multivariate (p = 0.02) analyses. These results suggest that miR124a methylation is associated with aggressive HL disease and may be an interesting factor for predicting treatment response.

Clinicopathologic characteristics of colorectal cancer with microsatellite instability.

Colorectal cancer (CRC) can be classified according to the level of microsatellite instability (MSI) exhibited by the tumor. The aim of this study was to determine MSI status in CRC from Tunisia and to identify clinical and pathological characteristics of MSI-H tumors. Microsatellite status was determined by polymerase chain reaction amplification using standard markers (BAT25, BAT26, D2S123, D5S346 and D17S250, the Bethesda panel) in 44 CRC cases. Molecular results were correlated with pathological and clinical features. Six CRC cases (13.8%) showed high-level instability (MSI-H), 14 cases had low level instability (MSI-L), and the remainders were stable (MSS). Immunohistochemical analysis showed loss of MSH2 protein in 3 cases among the 6 MSI-H tumors, whereas no silencing of MLH1 or MSH6 was found in any case. Significant differences in age and family history of cancers were observed between MSI-H and MSS/MSI-L groups (p=0.01 and p=0.002). However, statistical analysis showed that there were no significant differences between MSI-H and MSS/MSI-L tumors in terms of tumor location, lymph node involvement and stage of disease. Regarding histological features, MSI-H tumors were more likely to be poorly differentiated (p=0.003), to have a medullary pattern (p=0.005), and to harbor increased numbers of peritumoral lymphocytes (p=0.001). These findings indicate that careful observation of the tumor morphology can assist in the identification of unstable colorectal cancers requiring molecular investigations.

Patterns of aberrant DNA hypermethylation in nasopharyngeal carcinoma in Tunisian patients.

BACKGROUND: Aberrant methylation in the promoter of tumor-related genes is associated closely with epigenetically mediated gene silencing. The aim of the present study was to evaluate the methylation profile of Tunisian nasopharyngeal carcinoma (NPC) and to determine the clinicopathological features of tumors showing this epigenetic alteration. METHODS: Thirty-six archival NPC biopsies were investigated in comparison with 19 non-tumor nasopharyngeal tissue specimens. DNA methylation status of ten tumor-suppressor and related genes was analyzed by using methylation-specific PCR. The Epstein-Barr virus (EBV) presence was verified by PCR and in situ hybridization and the LMP1 oncoprotein expression was analyzed by immunohistochemistry. Findings were then correlated with clinicopathological variables (Patients' gender and age, tumor histological subtype and stage). RESULTS: Hypermethylation frequencies of the investigated genes in NPC biopsies were 75% for RASSFIA, 58.3% for SHP1, 47.2% for DAPK, 33.3% for P16, 31% for RARß2, 19.4% for GSTP1 and TIMP3, 11% for APC and CDH1, and 5.5% for MGMT. In non-tumor nasopharyngeal samples, hypermethylation was detected in lower frequencies in 6 genes (SHP 26.3%, P16 21%, RARß2 21%, DAPK 15.8%, TIMP3 10.5%, and GSTP 5.3%). Hypermethylation of RARß2 promoter was more frequent in tumors with lymph node metastasis than those without metastasis (43.5% vs 0%, p=0.03). Methylation of RASSF1A was more frequently detected in non-keratinizing NPC than in undifferentiated subtype (100% vs 66.7%; p=0.05). A trend toward positive association was found between an increased number of methylated genes and LMP1 expression (p=0.07). However, no significant association was found for the remaining variables. CONCLUSIONS: This study indicates that hypermethylation of multiple genes is a common alteration in nasopharyngeal carcinomas in Tunisian patients and that this epigenetic change may play a role in the nasopharyngeal carcinogenesis.

Immunodetection of SV40 T/t-antigens in human osteosrcoma in a series of Tunisian patients.

Osteosarcoma is a primary bone malignancy that typically occurs during adolescence but also has a second incidence peak in the elderly. The etiology of osteosarcoma is not well understood. Recent investigations have identified SV40 DNA sequences in osteosarcomas, suggesting that SV40 may contribute to tumor development. However, these studies also demonstrated geographical differences in SV40-positive osteosarcomas. The purpose of this study was to determine the prevalence and clinicopathological characteristics of SV40 positive osteosarcoma in Tunisian patients. Fifty-six formalin-fixed paraffin-embedded specimens of osteosarcomas were retrospectively investigated. Samples investigated were clinical cases examined between 1990 and 2004 in the Laboratory of Pathology at the University Hospital Farhat-Hached of Sousse (Tunisia). The search for SV40 was performed by immunohistochemistry using the Pab108 antibody for the detection of the viral oncoproteins: large T antigen and small t antigen (T/t-ag). SV40 status was correlated with clinico-pathological data. T/t-ag immunostaning was detected in the tumor cells in 31/56 (55.4%) osteosarcoma cases. SV40 positivity was more frequent (83%) in patients older than 40 years (5/6 cases) than in patients under 40 years (52%, 26/50), but the difference does not reach statistical significance (p = 0.33). Moreover, the time between the onset of clinical symptoms and diagnosis was shorter for SV40 positive than SV40 negative cases (p = 0.08). However, the viral status did not differ significantly according to gender, tumor size, histological subtype, tumor location, or metastases. This study documents the presence SV40 T/t-antigens in a proportion of osteosarcomas in Tunisian patients. The expression of these viral oncoproteins supports the hypothesis that SV40 may have a role in the pathogenesis of this tumor.

Contribution of epigenetic alteration of BRCA1 and BRCA2 genes in breast carcinomas in Tunisian patients.

OBJECTIVE: The aim of this study was to evaluate the contribution of the BRCA1 and BRCA2 promoter methylation in the pathogenesis of sporadic breast cancer in Tunisian patients. METHODS: Breast carcinoma tissues (n=117) and available paired normal breast tissues (n=65) from Tunisian women who had no family history were investigated for the methylation status of BRCA1 and BRCA2 promoters using methylation-specific PCR. Breast specimens from women without carcinoma (16 fibroadenomas and 5 mastopathies) were used as control. RESULTS: Hypermethylation of BRCA1 and BRCA2 promoters was detected respectively in 60.7% and 69.2% of the carcinoma tissues, and in only 7.7% and 4.6% of the paired normal breast tissues. None of the fibroadenomas and mastopathies showed hypermethylation. Correlations were found between BRCA1 and BRCA2 hypermethylation and decrease in their mRNA expression (p=0.02 and p=0.009, respectively). Moreover, BRCA1 methylation correlates with patients age (p=0.01) and triple negative (ER-, PR-, HER2-) tumors (p=0.01). Patients with methylated BRCA1 and/or BRCA2 had a significant prolonged survivals compared to those with unmethylated tumors (p=0.002). CONCLUSION: Our results suggest an important role of BRCA1 and BRCA2 promoter methylation in breast cancer development in the Tunisian population.