Strategies for diagnosis and management of CMMRD in low-resource countries: report of a Tunisian family

Constitutional Mismatch Repair Deficiency (CMMRD) is a rare childhood cancer predisposition syndrome, caused by biallelic pathogenic germline variants in the mismatch repair genes. Diagnosis and management of this syndrome is challenging, especially in low-resource settings. This study describes a patient diagnosed with colorectal cancer and grade 3 astrocytoma at the age of 11 and 12 respectively. Immunohistochemistry analysis showed a loss of MSH2 and MSH6 protein expression in CRC tissues of the patient. We identified by Targeted Exome Sequencing a homozygous pathogenic germline variant in exon 9 of the MSH6 gene (c.3991 C > T; p.Ala1268Glyfs*6). Genetic investigation of the family showed that the father was heterozygous for the identified pathogenic variant while the brother was wild type for this variant. Our study highlights the importance of a correct and timely diagnosis of CMMRD which can have implications for treatment. It also underlines the imperative need to enhance awareness, diagnostic standards, and surveillance that are crucial for patients and their families.

Association between interleuleukin-1β polymorphism (rs16944) and biomarkers levels in Iraqi patients with prostate cancer

OBJECTIVE

Prostate cancer (PCa) is the second-leading cause of mortality in men and the most commonly diagnosed non-cutaneous male malignancy. Host genetic factors, and inflammation-induced cytokines, play a key role in prostate oncogenesis. Single Nucleotide Polymorphisms (SNP) in cytokine genes were suggested to increase the susceptibility for PCa development and progression. This study aimed to investigate the association between the SNP (rs16944) in the interleukin-1 β (IL-1β) gene and the serum levels of Prostate Specific Antigen (PSA) Prolactine (PRL), testosterone, and IL-1β in Iraqi PCa patients versus healthy controls.

METHODS

Taqman Real Time-PCR, was performed to investigate the IL-1β (rs16944) polymorphism in 100 Iraqi PCa patients and 50 age-matched healthy controls in a case-control study. Serum levels of PSA, PRL, and testosterone were determined by ELISA and FIA, and associated with the IL-1β serum level as well as with the SNP (rs 16944). The association between the clinico-pathological parameters and the genotype distribution of PCa patients was also studied.

RESULTS

There level of IL-1β was significant increased in the serum of PCa patients compared to controls (P = 8.19 10^-7). Serum levels for other biomarkers such as PSA, PRL and testosterone were also significantly elevated in patients compared to controls (P < 0.0001). No differences were seen for genotype and allele distribution between PCa patients and controls. Nevertheless, in the group of controls, we found that 36% carried the GG genotype against only 26% in the patients group.This suggests that this could be a protective genotype (OR 0.62, P = 0.254). In addition, we found that the GA genotype is slightly more frequent in patients as compared to controls (OR 1.22, P = 0.605). Interestingly, serum levels of IL-1β, PSA, PRL and testosterone were significantly higher in PCa patients carrying the GA genotype, and the GA and AA genotypes are strongly associated with the aggressive behavior of the disease such as advanced TNM, and high Gleason score.

CONCLUSION

Our data suggest that both serum IL-1β level and IL-1β SNP (rs16944) may be considered as candidate biomarkers for PCa. Moreover, the GA, and AA genotypes carriers along with high sera levels of IL-1β, PSA and PRL, have an increased risk for PCa with aggressive behavior in Iraqi men.

Predominance of the Rare EGFR Mutation p.L861Q in Tunisian Patients with Non-Small Cell Lung Carcinoma

Objectives: Several new cancer therapies targeting signaling pathways involved in the growth and progression of cancer cells were developed as personalized medicine. Our study aimed to identify epidermal growth factor receptor (EGFR) mutations for TKI treatment in non-small-cell lung cancer (NSCLC) Tunisian patients. Methods: Analysis of the TKI sensitivity mutations in exons 18 to 21 of the EGFR gene and exon 15 of the B-raf gene was performed in 79 formalin fixed-paraffin embedded (FFPE) NSCLC samples using pyrosequencing. Results: EGFR mutations were detected in 34 cases among 79 (43%), with the predominance of the L861Q in exon 21 found in 35.3% of the cases (12 out of 34). Deletions in exon 19 were found in 8 cases (23.5%), and only one young male patient had the T790M mutation. Three patients harbored composite EGFR mutations (p.E746_A750del/p.L861R, p.E746_S752>V/p.S768I, and p.G719A/p.L861Q). Furthermore, the EGFR mutated status was significantly more frequent in female patients (p = 0.019), in non-smoker patients (p = 0.008), and in patients with metastasis (p = 0.044). Moreover, the B-raf V600E was identified in 5 EGFR negative patients among 39 analyzed samples (13.15%). Conclusion: The p.L861Q localized in exon 21 of the EGFR gene was the most common mutation identified in our patients (35.3%), whereas the “classic” EGFR mutations such as Del19 and p.L858R were found in 23.5% and 11.7% of the cases, respectively. Interestingly, most of p.L861X mutation-carrying patients showed good response to TKI treatment. Altogether, our findings suggest a particular distribution of the EGFR-TKIs sensitivity mutations in Tunisian NSCLC patients.

The Identification by Exome Sequencing of Candidate Genes in BRCA-Negative Tunisian Patients at a High Risk of Hereditary Breast/Ovarian Cancer

(1) Background: Germline variants in BRCA1/BRCA2 genes explain about 20% of hereditary breast/ovarian cancer (HBOC) cases. In the present paper, we aim to identify genetic determinants in BRCA-negative families from the South of Tunisia. (2) Methods: Exome Sequencing (ES) was performed on the lymphocyte DNA of patients negative for BRCA mutations from each Tunisian family with a high risk of HBOC. (3) Results: We focus on the canonical genes associated with HBOC and identified missense variants in DNA damage response genes, such as ATM, RAD52, and RAD54; however, no variants in PALB2, Chek2, and TP53 genes were found. To identify novel candidate genes, we selected variants harboring a loss of function and identified 17 stop-gain and 11 frameshift variants in genes not commonly known to be predisposed to HBOC. Then, we focus on rare and high-impact genes shared by at least 3 unrelated patients from each family and selected 16 gene variants. Through combined data analysis from MCODE with gene ontology and KEGG pathways, a short list of eight candidate genes (ATM, EP300, LAMA1, LAMC2, TNNI3, MYLK, COL11A2, and LAMB3) was created. The impact of the 24 selected genes on survival was analyzed using the TCGA data resulting in a selection of five candidate genes (EP300, KMT2C, RHPN2, HSPG2, and CCR3) that showed a significant association with survival. (4) Conclusions: We identify novel candidate genes predisposed to HBOC that need to be validated in larger cohorts and investigated by analyzing the co-segregation of selected variants in affected families and the locus-specific loss of heterozygosity to highlight their relevance for HBOC risk.

Novel and recurrent BRCA1/BRCA2 germline mutations in patients with breast/ovarian cancer: a series from the south of Tunisia

Background

The incidence of breast cancer (BC) and/or ovarian cancer (OC) is increasing in Tunisia especially in young women and mostly those with family history. However, the spectrum of BRCA mutations remains little explored in Tunisian patients in particular in the southern region.

Methods

We sequenced the entire coding regions of BRCA1and BRCA2 genes using next generation sequencing (NGS) in 134 selected patients with BC and/or OC.

Results

Among the 134 patients, 19 (14.17%) carried pathogenic mutations (10 are BRCA1 mutation carriers and 9 are BRCA2 mutation carriers) that are mainly frameshift index (76.9%). Interestingly, 5 out of the 13 variants (38.46%) were found at least twice in unrelated patients, as the c.1310-1313 delAAGA in BRCA2 and the c.5030_5033 delCTAA that has been identified in 4/98 BC patients and in 3/15 OC patients from unrelated families with strong history of cancer. Besides recurrent mutations, 6 variant (4 in BRCA1 and 2 in BRCA2) were not reported previously. Furthermore, 3 unrelated patients carried the VUS c.9976A > T, (K3326*) in BRCA2 exon 27. BRCA carriers correlated significantly with tumor site (p = 0.029) and TNBC cases (p = 0.008). In the groups of patients aged between 31 and 40, and 41–50 years, BRCA1 mutations occurred more frequently in patients with OC than those with BC, and conversely BRCA2 carriers are mostly affected with BC (p = 0.001, and p = 0.044 respectively).

Conclusions

The overall frequency of the BRCA germline mutations was 14.17% in patients with high risk of breast/ovarian cancer. We identified recurrent mutations as the c.1310_1313 delAAGA in BRCA2 gene and the c.5030_5033 delCTAA in BRCA1 gene that were found in 4% and 20% of familial BC and OC respectively. Our data will contribute in the implementation of genetic counseling and testing for families with high-risk of BC and/or OC.

Identification of novel candidate genes by exome sequencing in Tunisian familial male breast cancer patients

Male Breast Cancer (MBC) is a rare and aggressive disease that is associated with genetic factors. Mutations in BRCA1 and BRCA2 account for 10% of all MBC cases suggesting that other genetic factors are involved. The aim of the present study is to screen whole BRCA1 and BRCA2 exons using the Ampliseq BRCA panel in Tunisian MBC patients with family history. Furthermore, we performed exome sequencing using the TruSight One sequencing panel on an early onset BRCA negative patient. We showed that among the 6 MBC patients, only one (MBC-F1) harbored a novel frameshift mutation in exon 2 of the BRCA2 gene (c.17-20delAAGA, p.Lys6Xfs) resulting in a short BRCA2 protein of only 6 amino-acids. We selected 9 rare variants after applying several filter steps on the exome sequencing data. Among these variants, and based on their role in breast carcinogenesis, we retained 6 candidate genes (MSH5, DCC, ERBB3, NOTCH3, DIAPH1, and DNAH11). Further studies are needed to confirm the association of the selected genes with family MBC.

Serine protease inhibitors and human wellbeing interplay: new insights for old friends

Serine Protease Inhibitors (Serpins) control tightly regulated physiological processes and their dysfunction is associated to various diseases. Thus, increasing interest is given to these proteins as new therapeutic targets. Several studies provided functional and structural data about human serpins. By comparison, only little knowledge regarding bacterial serpins exists. Through the emergence of metagenomic studies, many bacterial serpins were identified from numerous ecological niches including the human gut microbiota. The origin, distribution and function of these proteins remain to be established. In this report, we shed light on the key role of human and bacterial serpins in health and disease. Moreover, we analyze their function, phylogeny and ecological distribution. This review highlights the potential use of bacterial serpins to set out new therapeutic approaches.

B1.12: a novel peptide interacting with the extracellular loop of the EBV oncoprotein LMP1

Latent membrane protein 1 (LMP1) encoded by the Epstein-Barr virus (EBV) plays an important role in EBV-induced cell transformation. Down-regulation of the LMP1 expression had shown promising results on cancer cell therapy. In this study, we identified by Phage display a novel peptide called B1.12 (ACPLDLRSPCG) which selectively binds to the extracellular loop (B1) of the LMP1 oncoprotein as demonstrated by molecular docking, NMR and ITC. Using an LMP1 expressing cell line, we showed that B1.12 decreased cell viability, and induced G0/G1 cell cycle arrest. In addition, the expression of A20, pAkt, and pNFkb (pRelA536) in C666-1 cells treated with B1.12 decreased compared to the untreated cells. In conclusion, we selected a novel peptide able to bind specifically to the extracellular loop of LMP1 and thus modulate its oncogenic properties.

RIP140 and LCoR expression in gastrointestinal cancers

The transcription coregulators RIP140 and LCoR are part of a same complex which controls the activity of various transcription factors and cancer cell proliferation. In this study, we have investigated the expression of these two genes in human colorectal and gastric cancers by immunohistochemistry. In both types of tumors, the levels of RIP140 and LCoR appeared highly correlated. Their expression tended to decrease in colorectal cancer as compared to adjacent normal tissues but was found higher in gastric cancer as compared to normal stomach. RIP140 and LCoR expression correlated with TNM and tumor differentiation. Significant correlations were observed with expression levels of key proteins involved in tumor progression and invasion namely E-cadherin and Cyclooxygenase-2. Survival analysis showed that patients with LCoR^low/RIP140^high colorectal tumors have a significant prolonged overall and disease-free survival. In gastric cancer, high LCoR expression was identified as an independent marker of poor prognosis suggesting a key role in this malignancy. Altogether, these results demonstrate that RIP140 and LCoR have a prognostic relevance in gastrointestinal cancers and could represent new potential biomarkers in these tumors.

Clinical and prognosis value of the CIMP status combined with MLH1 or p16 INK4a methylation in colorectal cancer

Aberrant DNA methylation of CpG islands occurred frequently in CRC and associated with transcriptional silencing of key genes. In this study, the CIMP combined with MLH1 or p16 ^INK4a methylation status was determined in CRC patients and correlated with clinicopathological parameters and overall survival. Our data showed that CIMP+ CRCs were identified in 32.9% of cases and that CACNAG1 is the most frequently methylated promoter. When we combined the CIMP with the MLH1 or the p16 ^INK4a methylation status, we found that CIMP-/MLH1-U (37.8%) and CIMP-/p16 ^INK4a -U (35.4%) tumors were the most frequent among the four subtypes. Statistical analysis showed that tumor location, lymphovascular invasion, TNM stage, and MSI differed among the group of patients. Kaplan-Meier analyses revealed differences in overall survival according to the CIMP combined with MLH1 or p16 ^INK4a methylation status. In a multivariate analysis, CIMP/MLH1 and CIMP/p16 ^INK4a methylation statuses were predictive of prognosis, and the OS was longer for patients with tumors CIMP-/MLH1-M, as well as CIMP-/p16 ^INK4a -M. Furthermore, DNMT1 is significantly overexpressed in tumors than in normal tissues as well as in CIMP+ than CIMP- tumors. Our results suggest that tumor classification based on the CIMP status combined with MLH1 or p16 ^INK4a methylation is useful to predict prognosis in CRC patients.

New Phage Display-Isolated Heptapeptide Recognizing the Regulatory Carboxy-Terminal Domain of Human Tumour Protein p53

The transcription factor tumor protein p53 (P53) controls a variety of genes most involved in cell cycle and is at the origin of apoptosis when DNA is irreparably damaged. We planned to select novel tumor protein p53-interacting peptides through the screening of hepta-peptide phage-display libraries. For this aim, human tumor suppressor protein p53 was expressed in Escherichia coli as Glutathione S-transferase fusion and purified by affinity chromatography. The phage library was then screened on this immobilized protein target. After three rounds of panning, phages were sequenced and shown to contain a consensus sequence NPNSAQG. Thereafter, either free p53 liberated from the fusion protein through thrombin treatment or Histidine-tagged p53 were recognized efficiently by the selected phage. To locate the p53-binding epitope of the selected hepta-peptide, three long peptides parts of the three known domains of the protein were synthesized and screened by the selected phage/peptide. Thus, the Carboxy-terminal p53 region was shown to be the target of the isolated phage as well as by its derived Fluorescein isothiocyanate-peptide. Molecular docking showed Lysine 386 as an important residue potentially engaged in this interaction. The selected hepta-peptide is a novel p53-interacting peptide, not described by other studies, and could be used as therapeutic tool in the future.

Expression and role of nuclear receptor coregulators in colorectal cancer

Colorectal cancer (CRC) is one of the most common human cancers and the cause of about 700000 deaths per year worldwide. Deregulation of the WNT/β-catenin pathway is a key event in CRC initiation. This pathway interacts with other nuclear signaling pathways, including members of the nuclear receptor superfamily and their transcription coregulators. In this review, we provide an overview of the literature dealing with the main coactivators (NCoA-1 to 3, NCoA-6, PGC1-α, p300, CREBBP and MED1) and corepressors (N-CoR1 and 2, NRIP1 and MTA1) of nuclear receptors and summarize their links with the WNT/β-catenin signaling cascade, their expression in CRC and their role in intestinal physiopathology.

Overexpression of miR-10b in colorectal cancer patients: Correlation with TWIST-1 and E-cadherin expression

MicroRNAs are emergent players of epigenetics that function as oncogenes or tumor suppressors and that have been implicated in regulating diverse cellular pathways. MiR-10b is an oncogenic microRNA involved in tumor invasion and metastasis in various cancers. Our data have shown that miR-10b is overexpressed in colorectal cancer samples in comparison with non-tumorous adjacent mucosa (p = 0.0025) and that it is associated with severe features such as tumor size >5 cm (p = 0.023), distant metastasis (p = 0.0022), non-differentiated tumors (p = 0.016), and vascular invasion (p = 0.01). Regarding the regulation of its expression, positive correlation between the loss of miR-10b and aberrant DNA methylation (p = 0.02) as well as a loss of TWIST-1 messenger RNA (p = 0.018) have been observed. Furthermore, expression analysis of the downstream miR-10b targets has shown that there are associations between low HOXD10 messenger RNA and E-cadherin protein levels (p < 0.0001, p = 0.0008, respectively) and overexpression of miR-10b. Our data suggests that overexpression of miR-10b results from high levels of TWIST-1 and may induce a decrease of E-cadherin membranous protein levels, thus contributing to the acquisition of metastatic phenotypes in colorectal cancer.

Clinical and prognosis relevance of COX-2 expression in Tunisian patients with primary gastric adenocarcinoma

BACKGROUND

Inflammation and hormonal signalling induce the cyclooxygenase-2 (COX-2) expression in various human cancers including Gastric Cancer (GC). GC remains among the human malignancies diagnosticated at advanced tumor stage and thus having a poor prognosis. COX-2 is a key protein in cancer progression which is involved in proliferation, invasion, and metastasis of tumor cells.

OBJECTIVE

The aim of this study was to investigate the expression of COX-2 and its association with clinico-patholocigal parameters and survival in Tunisian GC patients and to correlate COX-2 expression with others cancer-related proteins.

METHODS

The immunohistochemistry was used to study the expression of COX-2 on 93 patients with gastric adenocarcinoma.

RESULTS

Our results show that COX-2 immunostaining is negative to weak in 51.6%, moderate in 33.3%, and intense in 15.1% of tumor tissues. The expression of COX-2 associated significantly with tumor differentiation (p = 0.003), and histological type (p = 0.039). Furthermore, lack of COX-2 expression is significantly associated with 1-year (p= 0.005), 2-years (p= 0.000), and 5-years (p= 0.042) relapse free survival. In addition, Cox regression model, revealed that metastasis (p= 0.014), tumor site (p= 0.013), histotype (p = 0.02), and COX-2 expression (p = 0.003) are independent factors for prognosis. Regarding the relationship between COX-2 and cancer related proteins, we found that COX-2 expression is positively associated with APC (p = 0.006), and P53 (p = 0.026), supporting a cross link between these proteins in gastric carcinogenesis.

CONCLUSION

Our findings emphasize the importance of COX-2 as a potential marker of tumor progression and prognosis in GC, and that the inhibition of COX-2 activity may have a therapeutic benefit in GC.

Phage-display screening identifies LMP1-binding peptides targeting the C-terminus region of the EBV oncoprotein

Latent membrane protein 1 (LMP1), a major oncoprotein of Epstein Barr Virus (EBV) is responsible for transforming B lymphocytes in vitro. LMP1 is overexpressed in several EBV-associated malignancies, and different approaches have been developed to reduce its level and accordingly its oncogenic function in tumor tissues. This study aimed to use phage display peptide library to obtain peptides which could specifically bind to the cytoplasmic region of LMP1 to prevent its interaction with signaling proteins. The LMP1 C-terminus region was produced in bacterial E. coli and used as target for the phage library panning. After 3 rounds, 20 phage clones were randomly selected and 8 showed high binding affinity to the recombinant C-terminus LMP1 protein. The most interesting candidates are the FO5 "QPTKDSSPPLRV" and NO4 "STTSPPAVPHNN" peptides since both bind the C-terminus LMP1 as showed by molecular docking. Furthermore, sequence alignment revealed that the FO5 peptide shared sequence similarity with the Death Receptor 4 which belongs to the tumor necrosis factor-related apoptosis-inducing receptor which plays key role in anti-tumor immunity.

Clinicopathological and prognostic significance of p53, Ki-67, and Bcl-2 expression in Tunisian gastric adenocarcinomas

Gastric carcinoma (GC) is a highly aggressive malignancy with poor prognosis. It is widely accepted that malignancy results from abnormal cell growth due to dysregulation of the balance between cell proliferation and apoptosis. Our study aimed to investigate the clinicopathological and prognostic significance of p53, Ki-67, and Bcl-2 in Tunisian GC patients by immunohistochemistry. It was observed that the older patients showed p53 overexpression compared with the younger patients (p<0.05). There was higher p53 expression in the intestinal-type compared with the diffuse-type (p<0.05), and in well/moderate differentiated than in poor differentiated tumors. The expression of Ki-67 was positively associated with tumor size and venous invasion (p<0.05). Bcl2 expression occurred in male patients and correlated with depth of invasion (p=0.02). A Kaplan-Meier analysis indicated an inverse correlation between p53 and Ki-67 expression and the overall survival. Multivariate analysis revealed that the tumor site, Ki-67 and p53 expression were independent prognostic factors for gastric carcinomas (p<0.05). Finally, combined expression of p53, Ki-67 and Bcl-2 showed that the group of patients with tumors p53+/Ki-67+/Bcl2- had aggressive behavior and poor prognosis (p log rank=0.000). In summary, our data indicated that the expression of p53, Ki-67, and Bcl-2 may provide useful information for identifying patients with aggressive behavior and poor prognosis of GC.

Negative control glucose dependent mediated by the PreS2 region on the translation efficiency of the reporter Sh-bleomycin gene in Saccharomyces cerevisiae

Saccharomyces cerevisiae is able to sense and respond to environmental changes such as the availability of carbon sources. In a previous work, we showed that the expression of the PreS2-S gene of HBV in yeast was negatively regulated at the translational level dependent of glucose. In this study, we show that the S mRNA is detected in the polysomes indicating its active translation, while the PreS2-S mRNA was mainly found in monosomes. Moreover, we used the gene reporter assay based on Zeocin resistance, to better characterize the PreS2 region responsible for this control. Two chimeric genes composed of the N- and C-terminal part of the PreS2 fused to the Sh-bleomycin gene conferring the resistance to Zeocin were expressed in yeast. We found that the strain expressing the N-terminal part of the PreS2 was sensitive to Zeocin on rich medium with 2% glucose. In contrast, the strain harbouring the C-terminal part of the PreS2 fused to the Sh-bleomycin grew on Zeocin, indicating that the Sh-bleomycin mRNA is efficiently translated, subsequently conferring resistance to Zeocin. Our data suggest the establishment of a translational control via the N-terminal part of the PreS2 mediated by the presence of 2% glucose in the media.

Expression of APC, β-catenin and E-cadherin in Tunisian patients with gastric adenocarcinoma: clinical significance

Aberrant activation of the Wnt signalling pathway is a key feature of many cancers. β-Catenin, adenomatous polyposis coli (APC) and E-cadherin are major players in this pathway. The aim of this study is to examine the expression of β-catenin, APC and E-cadherin in tumour tissues of 80 Tunisian patients with gastric carcinoma and to determine the methylation status of the APC promoter in tumour tissues. Associations between protein expression and clinico-pathological parameters, including prognosis, were performed. Positive expression of β-catenin, APC and E-cadherin was observed in 77.5, 68.7 and 60% of cases, respectively. Tumours lacking membranous expression of β-catenin had greater extent of lymph node metastasis, poor differentiation and advanced T-stage. The expression of E-cadherin correlated with poor differentiation (P = 0.05) and β-catenin expression (P = 0.004). With regards to prognosis, the overall survival time was significantly prolonged for patients showing normal β-catenin expression (exclusively or predominantly membranous staining) alone or combined with positive APC expression (P log rank = 0.008 and 0.003, respectively). The methylated pattern of APC promoter 1A was detected in 43.8% of cases and correlated with T-stage (P = 0.046) and distant metastasis (P = 0.037). No correlation was found between the methylated profile of APC promoter 1A and the expression of APC protein in tumour tissues. Our findings suggest that deregulation of the Wnt pathway via abnormal expression of β-catenin and E-cadherin occurred frequently in gastric carcinoma and correlated with worse clinical behaviour.

Quantitative expression analysis and prognostic significance of the BCL2-associated X gene in nasopharyngeal carcinoma: a retrospective cohort study

Background

Nasopharyngeal carcinoma (NPC) is a highly metastatic epithelial malignancy showing high prevalence in Southeast Asia and North Africa. The BCL2-associated X (BAX) gene encodes the most important pro-apoptotic member of the BCL2 family. We have recently shown that BCL2 and BCL2L12, two other members of the same apoptosis-related family, possess significant prognostic value in NPC. The objective of the current study was to analyze BAX mRNA expression in nasopharyngeal biopsies of NPC patients, and to assess its prognostic potential in this disease.

Methods

Total RNA was isolated from 88 malignant and 9 hyperplastic nasopharyngeal biopsies, resected from Tunisian patients. After cDNA synthesis by reverse transcription of polyadenylated RNA, BAX mRNA expression was analyzed using a highly sensitive quantitative real-time polymerase chain reaction (qRT-PCR) method.

Results

Lower BAX mRNA levels were detected in NPC biopsies than in hyperplastic nasopharyngeal samples. BAX mRNA expression status was associated with low tumor extent, negative regional lymph node status, and absence of distant metastases. Kaplan-Meier survival analysis demonstrated that patients with BAX mRNA-positive NPC have significantly longer disease-free survival (DFS) and overall survival (OS). In accordance with these findings, Cox regression analysis revealed that BAX mRNA expression can be considered as a favorable prognostic indicator of DFS and OS in NPC, independent of their gender, age, tumor histology, tumor extent, and nodal status. Furthermore, NPC patients without distant metastases are less likely to relapse when their primary tumor is BAX mRNA-positive, compared to metastasis-free patients with a BAX-negative nasopharyngeal malignancy.

Conclusion

This is the first study examining the potential clinical utility of BAX as a prognostic tumor biomarker in NPC. We provide evidence that BAX mRNA expression can be considered as an independent favorable prognostic indicator of DFS and OS in NPC.

Loss of WIF-1 and Wnt5a expression is related to aggressiveness of sporadic breast cancer in Tunisian patients

Activation of the Wnt/β-catenin signaling pathway is common in various human cancers. The aim of this study was to investigate the expression of 2 members of the Wnt family (WIF-1 and Wnt5a) in sporadic and hereditary breast cancer tissues. WIF-1, is a secreted antagonist that binds Wnt ligands, and therefore inhibits the canonical Wnt/β-catenin pathway. Wnt5a is one of the members of the noncanonical Wnt family that mainly acts through calcium signaling pathway. The expression of WIF-1 was analyzed by methylation-specific PCR and RT-PCR, and the level of Wnt5a ligand was quantified by RT-QPCR in breast cancer tissues. Methylation of WIF-1 was detected in 71.3 % and 81.8 % of sporadic and hereditary cases, respectively. Aberrant methylation of WIF-1 was associated with advanced TNM stage and triple negative cases in sporadic breast carcinoma (p=0.001 and p=0.037, respectively). In hereditary cases, methylation of WIF-1 correlated with age at diagnosis (p=0.027) and p53 status (p=0.035). Regarding patients' survival, WIF-1 methylated promoter conferred a reduced overall survival rate, and particularly in a group of patients with advanced TNM stage (p log rank=0.006). Furthermore, aberrant CpG methylation of the WIF-1 promoter was significantly associated with transcriptional silencing of this tumor suppressor gene in sporadic breast cancer tissues (p=0.036). On the other hand, in sporadic tumor tissues, the level of Wnt5a mRNA was significantly lower compared to normal tissues (p=0.031) and lower still in those showing more aggressive behavior, suggesting that Wnt5a, a ligand involved in the noncanonical Wnt/β-catenin pathway, could act as a tumor suppressor gene in breast cancer.

Expression of COX-2 and E-cadherin in Tunisian patients with colorectal adenocarcinoma

Cyclo-oxygenase 2 (COX-2) and E-cadherin are promising biomarkers for cancer diagnosis and therapy. The aim of this study was to examine the expression of these two proteins in primary colorectal adenocarcinomas and to investigate their association with clinicopathological characteristics including survival of patients. Immunostaining of E-cadherin and COX-2 was assessed in 70 primary colorectal adenocarcinomas from Tunisian patients. Membranous E-cadherin immunostaining and cytoplasmic COX-2 expression were observed in 74.3% and 68.6% of cases respectively. A significant association was found between COX-2 expression and age at diagnosis (P=0.02), and vessel invasion (P=0.037). The expression of E-cadherin correlated with age at diagnosis (P=0.01), and tumor size (P=0.02). In addition, by multivariate analysis, we revealed a significant association with 1-year disease free survival and a tendency with distant metastasis (P=0.017 and P=0.065 respectively). On the other hand, tumors exhibiting COX-2+/E-cadherin-profile were larger (P=0.006), and in an advanced stage (P=0.001). Survival analysis showed that COX-2 over-expression confers a reduced overall survival rate (Plog rank=0.036) and is an independent factor predictive for prognosis.

Negative/low HER2 expression alone or combined with E-cadherin positivity is predictive of better prognosis in patients with breast carcinoma

The loss of E-cadherin expression leads to absence of tissue integrity, an essential step in tumor progression. Methylation of CpG islands in the promoter region of the CDH1 gene coding E-cadherin might be an alternative for gene silencing. In the present study, we investigate the expression of E-cadherin and hormone receptors in invasive ductal breast carcinoma (IDCs). Protein expression was analysed immunohistochemically in 87 cases, including 26 familial tumors. The most interesting results revealed a significantly reduced E-cadherin expression in cases with familial history compared to sporadic tumors (p=0.009), as well as with tumors ≤5 cm (p=0.022). Moreover, HER2 over-expression was associated with distant metastasis (p=0.011) and overall survival (p log rank=0.028). Tumors displaying negative/low HER2 expression combined with E-cadherin positivity confer better patient survival (p=0.052). Triple Negative tumors (TN) were more frequently found in patients with advanced grade (GIII) (p=0.001) and TNM (III+IV) (p=0.018) which supports the aggressive behavior of TN tumors. On the other hand, hypermethylation of CDH1 gene promoter was observed in 46% of hereditary cases and strongly associated with loss of E-cadherin expression (p=0.002). Furthermore, patients with unmethylated CDH1 pattern have a better 5-year disease free survival (p=0.021). In conclusion, in patients with hereditary breast cancer, the CpG methylation event contributes to the loss of E-cadherin expression. On the other hand, HER2 over-expression is predictive of worse prognosis, either alone or combined with loss of E-cadherin expression in Tunisian patients with breast cancer.

Yeasts as a tool for heterologous gene expression

The yeasts Saccharomyces cerevisiae and Pichia pastoris are attractive hosts for production of human proteins. The main advantages offered by these systems are the well-developed and easily accessible genetic tools, rapid growth, the simple and inexpensive culture media, and many of the cellular and metabolic processes found in higher eukaryotes are conserved in both yeast species. In this chapter, we describe the production of two proteins of therapeutic interest: the human P53 tumor suppressor and the viral HBsAg in P. pastoris and S. cerevisiae using the strong and inducible promoters AOX1 and Gal10/Cyc1, respectively. Besides the production as a goal of both expressions, we also report on an unexpected result that has occurred in S. cerevisiae: The overexpression of human p53 induces yeast cell death with characteristic markers of apoptosis, such as the externalization of phosphatidylserines and DNA strand cleavage.

Prognostic significance of p16INK4a/p53 in Tunisian patients with breast carcinoma

Infiltrating ductal carcinoma (IDC) of the breast is a result of genetic alterations that affect the regulation of the cell cycle check-point and apoptosis. The aim of the present study was analysis using immunohistochemical localization of mouse double minute-2 (mdm2), p16INK4a, p53, bax and bcl-2 markers in Tunisian patients with breast IDC and to determine if there was correlation with the major clinico-pathological parameters and with survival of patients. We showed that the expression of p53, p16INK4a, mdm2, bcl-2, and bax was observed in 46.3%, 20.7%, 38%, 50% and 11.9% of cases, respectively. Statistical analysis revealed that positive expression of mdm2 was associated with larger tumors (P=0.013), whereas bax positivity was more prevalent in younger patients and in tumors of smaller size (P=0.008 and P=0.012 respectively). Furthermore, the expression of p16INK4a correlated with advanced grade (P<0.0001), triple negative tumors (ER-/PR-/HER2-, P=0.001) and mdm2 expression (P=0.017). The absence of nuclear p53 accumulation was predictive of good prognosis as well as when it was associated with negative expression of p16INK4a. Our findings suggest that among the biomarkers tested, p16INK4a might have a useful clinical and prognostic significance in infiltrating ductal carcinoma of the breast.

Hypermethylation of tumor-related genes in Tunisian patients with gastric carcinoma: clinical and biological significance

BACKGROUND

Promoter hypermethylation is an alternative mechanism of gene silencing in cancers including gastric carcinoma (GC). Its affects genes with crucial functions as tumor suppressor.

METHODS

DNA methylation in the promoter of P16INK4a, DAPK, retinoic acid receptor β (RARβ2), RASSF1A, and CDH1 genes was investigated in 79 Tunisian patients with GC using methylation-specific PCR.

RESULTS

The methylation frequencies vary from 31.6% for P16INK4a to 65.8% for RARβ2. Hypermethylation of DAPK and CDH1 was associated with tumor grade and age (P = 0.04 and 0.034) respectively, while hypermethylation of RASSF1A correlated with TNM stage (P = 0.027). The distribution of the methylated DNA at P16INK4a, DAPK, and CDH1 promoters were different in the intestinal and diffuse histotypes of GC according to TNM. Moreover, the survival rate of patients with P16INK4a methylated status was shorter than that of patients with the unmethylated status (P log rank = 0.009). On the other hand, the hypermethylation of RARβ2 correlated with COX-2 expression (P = 0.001).

CONCLUSION

We showed that methylation of P16INK4a is predictive of poor prognosis and could be a useful marker. Moreover, the association between RARβ2 methylation and COX-2 expression suggests a functional link between these two proteins in gastric carcinogenesis.

Methylation status and overexpression of COX-2 in Tunisian patients with ductal invasive breast carcinoma

Inflammation and hormonal signalling induce the cyclooxygenase-2 (COX-2) expression in solid tumours including breast cancer, which in turn affects cell proliferation, apoptosis and metastasis. The aim of this study was to investigate the expression of COX-2 and its association with clinical parameters, patient's survival, hormones receptors (oestrogen, progesterone), ERBB2 and TP53 expression in 83 cases of infiltrating ductal breast carcinomas. Moreover, the methylation status at the CpG islands of the COX-2 gene promoter was also explored in 70 specimens. We showed that tumours exhibiting moderate to intense COX-2 immunostaining were significantly more frequent in patients over 45 years old (p = 0.027). Moreover, a high level of COX-2 expression correlated with a shorter survival time (p log-rank = 0.04) and was an independent prognostic factor (p = 0.022; HR 6.4; 95% CI = 1.3-31.4). On the other hand, hypermethylation of the COX-2 gene promoter was observed in 27% of cases and strongly associated with smaller tumours (<5 cm, p = 0.011). Furthermore, patients with methylated COX-2 pattern have a better 4-year disease-free survival (p = 0.022) as well as a prolonged overall survival (p log-rank test = 0.034). In conclusion, we showed that high COX-2 expression was associated with reduced survival and was an independent prognostic factor. However, hypermethylation of the COX-2 promoter correlated with a better overall survival in Tunisian patients with breast carcinoma.

BCL2L12 is a novel biomarker for the prediction of short-term relapse in nasopharyngeal carcinoma

BCL2-like 12 (BCL2L12 ) is a new member of the apoptosis-related BCL2 gene family, members of which are implicated in various malignancies. Nasopharyngeal carcinoma is a highly metastatic, malignant epithelial tumor, with a high prevalence in Southeast Asia and North Africa. The purpose of the current study was to quantify and investigate the expression levels of the BCL2L12 gene in nasopharyngeal carcinoma biopsies and to assess its prognostic value. Total RNA was isolated from 89 malignant and hyperplastic nasopharyngeal biopsies from Tunisian patients. After testing the quality of the extracted RNA, cDNA was prepared by reverse transcription. A highly sensitive real-time polymerase chain reaction (PCR) method for BCL2L12 mRNA quantification was developed using SYBR Green chemistry. GAPDH served as a reference gene. Relative quantification analysis was performed using the comparative C(T) (2(-ΔΔCT)) method. Higher BCL2L12 mRNA levels were detected in undifferentiated carcinomas of the nasopharynx, rather than in nonkeratinizing nasopharyngeal tumors (P = 0.045). BCL2L12 expression status was also found to be positively associated with the presence of distant metastases (P = 0.014). Kaplan-Meier survival analysis demonstrated that patients with BCL2L12-positive nasopharyngeal tumors have significantly shorter disease-free survival (P = 0.020). Cox regression analysis showed BCL2L12 expression to be an unfavorable and independent prognostic indicator of short-term relapse in nasopharyngeal carcinoma (P = 0.042). Our results suggest that mRNA expression of BCL2L12 may constitute a novel biomarker for the prediction of short-term relapse in nasopharyngeal carcinoma.

Epigenetic alteration of the Wnt inhibitory factor-1 promoter is common and occurs in advanced stage of Tunisian nasopharyngeal carcinoma

Activation of the wingless-type (Wnt) signaling pathway is common in cancers. The Wnt inhibitory factor-1 (WIF-1) is a secreted antagonist that acts by binding to Wnt ligands. We examined by methylation-specific PCR (MSP), whether WIF-1 is inactivated in 68 nasopharyngeal carcinomas (NPC), and 10 normal mucosa. We showed that the WIF-1 promoter was methylated in 89.7% of tumors, whereas all normal mucosa were unmethylated. The WIF-1 methylation was associated with the tumor, node, and metastasis (TNM) (p = .003) and the age (p = .014). The Wnt-5a mRNA was higher in tumors and correlated with TNM (p = .012). The methylation of WIF-1 contributes to the activation of the Wnt pathway in NPC.

Hypermethylation of RARβ2 correlates with high COX-2 expression and poor prognosis in patients with colorectal carcinoma

Silencing of gene expression by aberrant methylation at the CpG islands is common in human tumors, including colorectal cancer. This epigenetic alteration affects promoter of genes having crucial cellular functions such as tumor suppressor, DNA repair, apoptosis, cell adhesion, etc. We investigated the methylation status in the promoter regions of the RARβ2, RASSF1A, DAPKinase, and CDH1 genes in 73 colorectal carcinoma and 43 paired normal tissues of Tunisian patients using methylation-specific PCR assays. The association between methylation status and the clinicopathological features was evaluated. To determine whether aberrant methylation affects gene expression, we performed immunohistochemistry analysis for E-cadherin and COX-2, a target gene of RARβ2. The methylation frequencies vary from 80.8% for RARβ2 to 35.6% for RASSF1A while in non-tumor-paired samples; the frequencies of methylation are significantly lower for all the fourth genes tested. The methylation status did not correlate with any of the clinical features considered; however, aberrant methylation of RARβ2 was associated with a shortened overall patients' survival (p log rank = 0.026); nevertheless, it needs to be confirmed on larger sample size. Moreover, a significant inverse association was observed between methylation status of RARβ2 and COX-2 protein expression in tumor specimen (p = 0.014). On the other hand, we found that loss of E-cadherin expression was significantly associated with aberrant methylation of the CDH1 promoter (p = 0.005). Our findings showed that RARβ2 was frequently methylated in colorectal cancer and correlated with a worse prognosis and high expression of COX-2 suggesting a link between these two proteins in colorectal carcinogenesis. We also showed that epigenetic alteration of CDH1 is a major mechanism of the loss of E-cadherin protein expression in primary colorectal tumors.

Selection of cell death-deficient p53 mutants in Saccharomyces cerevisiae

The budding yeast Saccharomyces cerevisiae is a useful system for the detection and transcriptional evaluation of mutant p53 in cancer. In previous work we showed that the overexpression of wild-type p53 induces yeast cell death on minimal medium; however, the R248W p53 mutant was completely inactive, and we suggested that ROS production is a key event in p53-induced yeast cell death. In this study we explored the effect of other p53 mutants, such as the hot-spot mutant R282W and the double mutant N268S::I332V. Unexpectedly, both mutants behaved inversely to R248W, as they completely inhibited yeast growth on minimal medium and induced ROS production. This phenotype 'yeast cell death on minimal medium' allowed for the subsequent screening of intragenic p53-inactivating mutations. In all cases, the 'revertant yeast clones' display a complete p53 inactivation through either gross deletion or nonsense mutations. More interestingly, missense mutations were also found: the deletion of I255 or substitution of R337G completely inactivated the p53 mutant R282W in the yeast context. Taken together, these results suggest that p53 tumour-derived mutants could be classified according to their ability to induce yeast cell death and not uniquely by their transcriptional activity on a selected target reporter gene.

PIK3CA amplification is predictive of poor prognosis in Tunisian patients with nasopharyngeal carcinoma

PI3Ks (phosphatidylinositol 3-kinases) are lipid kinases that regulate signalling pathways involved in cell proliferation, motility, and adhesion. Somatic mutations and amplification of the PIK3CA gene have been reported in various types of human cancers. However, little is known about the frequency and prognosis role of PIK3CA activation in nasopharyngeal carcinoma (NPC). This study was conducted with the aim to screen for PIK3CA mutations in the two hot spot regions (exons 9 and 20) and to investigate for the PIK3CA gene amplification combined with the expression analysis of the phosphorylated Akt (pAkt). We showed that among 88 specimens, none had mutation in the helical domain (exon 9) and only one (1.13%) had mutation in the kinase domain (exon 20). On the other hand, PIK3CA gene amplification was found in 21.6% of cases and was strongly associated with distant metastasis (P = 0.002), lymph node involvement (P = 0.032), and advanced tumor stage (P < 0.001). Moreover, patients with PIK3CA copy number gain have a significant reduced overall survival time (P log rank = 0.02). We concluded that PIK3CA gene amplification is frequent in NPC and occurs in the advanced stage of NPC. Moreover, our finding emphasizes the association of PIK3CA gene amplification with worse prognosis in nasopharyngeal carcinoma.

Inactivation of RASSF1A, RARbeta2 and DAP-kinase by promoter methylation correlates with lymph node metastasis in nasopharyngeal carcinoma

Epigenetic modification is one of the mechanisms leading to gene silencing in neoplastic cells. By methylation-specific PCR, we analyzed the promoter methylation of three cancer-related genes: Ras Association domain Family 1A (RASSF1A), Death Associated Protein kinase (DAP-kinase) and Retinoic Acid Receptor beta2 (RARbeta2) in two NPC xenografts (C15 and C17), 68 primary NPC tumors, and nine normal nasopharyngeal epithelia. We showed that C15 and C17 displayed a complete promoter methylation of RASSF1A, RARbeta2 and DAP-kinase genes. In primary NPC tumors, the incidence of promoter methylation was very high for all three tested genes: 91% for RASSF1A, 88% for both RARbeta2 and DAP-kinase whereas all normal nasopharyngeal epithelia were unmethylated. Interestingly, our study revealed that aberrant promoter methylation of the three genes were statistically associated with the lymph node involvement (p < 0.0001). In addition, hypermethylation of RASSF1A was correlated with age at diagnosis (p = 0.047) and T stage (p = 0.037) while the RARbeta2 hypermethylation was associated with histological type (p = 0.011). Taken together, our results demonstrate that silencing of RASSF1A and RARbeta2 expression by promoter hypermethylation is associated with highly differentiated tumors, advanced tumor stage and the presence of lymph node metastasis. To assess the functional significance of the epigenetic silencing of RARbeta2 and DAP-kinase in NPC, we analysed the expression of two downstream target genes COX-2 and p53 by reverse PCR (RT-PCR) and immunohistochemistry (IHC). We revealed a significant association between expression of COX-2 and loss of RARbeta2 through aberrant methylation (p = 0.003) in NPC biopsies. We concluded that the inactivation of RASSF1A, RARbeta2 and DAP-Kinase by hypermethylation is a key step in NPC tumorigenesis and progression.

Inactivation of RASSF1A, RARbeta2 and DAP-kinase by promoter methylation correlates with lymph node metastasis in nasopharyngeal carcinoma

Epigenetic modification is one of the mechanisms leading to gene silencing in neoplastic cells. By methylation-specific PCR, we analyzed the promoter methylation of three cancer-related genes: Ras Association domain Family 1A (RASSF1A), Death Associated Protein kinase (DAP-kinase) and Retinoic Acid Receptor beta2 (RARbeta2) in two NPC xenografts (C15 and C17), 68 primary NPC tumors, and nine normal nasopharyngeal epithelia. We showed that C15 and C17 displayed a complete promoter methylation of RASSF1A, RARbeta2 and DAP-kinase genes. In primary NPC tumors, the incidence of promoter methylation was very high for all three tested genes: 91% for RASSF1A, 88% for both RARbeta2 and DAP-kinase whereas all normal nasopharyngeal epithelia were unmethylated. Interestingly, our study revealed that aberrant promoter methylation of the three genes were statistically associated with the lymph node involvement (p < 0.0001). In addition, hypermethylation of RASSF1A was correlated with age at diagnosis (p = 0.047) and T stage (p = 0.037) while the RARbeta2 hypermethylation was associated with histological type (p = 0.011). Taken together, our results demonstrate that silencing of RASSF1A and RARbeta2 expression by promoter hypermethylation is associated with highly differentiated tumors, advanced tumor stage and the presence of lymph node metastasis. To assess the functional significance of the epigenetic silencing of RARbeta2 and DAP-kinase in NPC, we analysed the expression of two downstream target genes COX-2 and p53 by reverse PCR (RT-PCR) and immunohistochemistry (IHC). We revealed a significant association between expression of COX-2 and loss of RARbeta2 through aberrant methylation (p = 0.003) in NPC biopsies. We concluded that the inactivation of RASSF1A, RARbeta2 and DAP-Kinase by hypermethylation is a key step in NPC tumorigenesis and progression.

Human p53 induces cell death and downregulates thioredoxin expression in Saccharomyces cerevisiae

The p53 tumour suppressor protein has a crucial role in controlling cell cycle and apoptosis in human cells and its inactivation by selective point mutations is associated with human cancers. Here we show that overexpression of the human wild-type (wt) p53 in Saccharomyces cerevisiae completely inhibits yeast growth under minimal media conditions. In contrast, the R248W 'hot spot' p53 mutant (one of the most frequent p53 mutations encountered in human cancers) does not impair yeast growth. Moreover, we report, for the first time, that the human wt p53 induces yeast cell death with characteristic markers of apoptosis: exposure of phosphatidylserine and DNA strand cleavage as shown by Annexin V staining and terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling assay, respectively. In addition, p53 also has an impact on the expression of yeast genes. Using differential display and Northern blot analysis, we demonstrated that human wt p53 expression in yeast leads to gene repression of thioredoxin (TRX1/2), a highly conserved multifunctional antioxidative and antiapoptotic protein family. Accordingly, we demonstrated that reactive oxygen species (ROS) are highly produced in p53 yeast induced cell death as shown by dihydrorhodamine 123 staining. These results suggest that the generation of ROS is a key event in p53 yeast induced cell death.

Overexpression of COX-2 and LMP1 are correlated with lymph node in Tunisian NPC patients

Cyclooxygenase 2 (COX-2) an inducible form of COX is frequently up-regulated in many human tumours. The expression of COX-2 in nasopharyngeal carcinoma (NPC) and its relationship to clinicopathological features were studied in Tunisian patients. COX-2 mRNA was detected in 91% of tumour tissues. Immunohistochemical analysis showed that COX-2 protein was strongly detected in tumour cells and the staining was mainly cytoplasmic. In contrast, COX-2 mRNA and protein were very low or undetectable in normal nasopharyngeal mucosa. Our result showed a significant association of COX-2 overexpression with the lymph node involvement, however, no correlation was observed with age, tumour stage, histological type and distant metastasis. Moreover, we showed that all tumour specimens co-overexpressed COX-2 and the EBV oncoprotein LMP1 corroborating the fact that LPM1 is known to induce COX-2. Altogether, our data suggests that the COX-2 is overexpressed in NPC biopsies and that is linked to the lymph node involvement.

High-level expression of human tumour suppressor P53 in the methylotrophic yeast: Pichia pastoris

The human tumour suppressor P53 is a key protein involved in tumour suppression. P53 acts as a "guardian of genome" by regulating many target genes involved in cell cycle regulation, DNA repair and apoptosis. We report the P53 expression by the methylotrophic yeast Pichia pastoris using the methanol inducible AOX1 promoter. We have produced the rP53 in intracellular form as well as secreted using the Saccharomyces cerevisiae alpha-mating factor prepro-leader sequence in two genetic contexts of Pichia, Mut(s) and Mut(+). The intracellular P53 was successfully produced by Mut(s) (KM71) as well as Mut(+) (X33) strains, however, the secreted form was mainly observed in the Mut(s) strain, despite a higher number of p53 copies integrated in the Mut(+) strain. Interestingly, in Mut(s) phenotype, the medium pH influences markedly the rP53 production since it was higher at pH 7 than 6.

Immunohistochemical Status of p53, MDM2, bcl2, bax, and ER in Invasive Ductal Breast Carcinoma in Tunisian Patients

TP53 gene alterations have been associated with sporadic breast cancer. To assess the role of p53 in invasive ductal carcinoma (IDC) of the breast among Tunisian patients, p53 protein status was studied by immuno-histochemical analysis. The p53 protein was expressed in 41 of 70 (58%) tumors. Study of the status of its target gene expression showed that MDM2 was overexpressed in 43 tumors (61%), bcl2 in 29 (41%), and bax in only 9 (12%). Estrogen receptor (ER) was detected in 38 tumor tissues (54%). The accumulated p53 was significantly associated with MDM2-positive, bcl2-negative, and ER-negative tumors (P = 0.024, P = 0.000027, and P = 0.000008, respectively), whereas with bax the correlaton was not significant. Bcl2 immunostaining displayed a positive correlation with ER (P = 0.001). A significantly higher fraction of p53-positive cells was observed in ER-negative SBRII-SBRIII tumors than in ER-positive SBRI-SBRII tumors (P = 0.000066). bcl2-positive tumors were significantly correlated with ER-positive/SBRI-SBRII tumors (P = 0.007), but negatively correlated with p53/bax (P = 0000004). MDM2 immunostaining displayed the same phenotype as p53 in the correlation with bcl2 and ER (P = 0.003), strengthened by significant associations between MDM2-positive/p53-positive and bcl2-negative or ER-negative, respectively (P = 0.00005 and P = 0.000001, respectively). MDM2-positive cells were significantly correlated with the p53-positive/bax-negative phenotype (P = 0.04). These results suggest that p53 accumulated in these tumor tissues is associated with bad prognostic markers (ER-negative, SBRIII) of IDC. MDM2 overexpression might be responsible for the accumulated p53 value in IDC. Regulation of the apoptotic process is involved in IDC; bcl2 is associated with a good prognostic marker (ER-positive and SBRI-II), whereas the regulation of bax is complex and does not necessarily correlate with the overexpression of p53.

Various 30 and 69 bp deletion variants of the Epstein-Barr virus LMP1 may arise by homologous recombination in nasopharyngeal carcinoma of Tunisian patients

Nasopharyngeal carcinoma (NPC) occurs with a striking geographic distribution, it is endemic in certain areas of Southeast Asia and North Africa. NPC is tightly linked to Epstein-Barr virus (EBV), however, only a small subset of EBV genes are expressed, among them the latent membrane protein 1 (LMP1). LMP1 is considered as the main EBV oncoprotein and its 30 bp deleted-variant has been reported to be more prevalent in biopsies of NPC. We have assessed the 30 bp deletion and the XhoI polymorphisms of the BNLF1 gene in 30 peripheral bloods of NPC patients and 62 nasopharyngeal biopsies, 42 being confirmed as undifferentiated nasopharyngeal carcinoma and 20 are normal nasopharyngeal epithelium cells. Our results show that 100% of individuals retained the XhoI restriction site. A rare NPC variant, having a 69 bp deletion in the C-terminus region of the BNLF1 gene, covering the 30 bp deletion, was found in two NPC biopsies. The deleted 30 and 69 bp deleted-variants are significantly (p = 0.006) more frequent in NPC (71.42%) than in control biopsies (52%). In peripheral blood of NPC patients, the deleted-variants (47%) are also lower than in tumor tissues (p = 0.0004), suggesting that the deletion could be associated with a risk of tumor genesis. Direct repeats, located at the extremities of the 30 and 69 bp deletions, should be involved in this process. We propose that other deletions could be found since another similar direct repeat is present at the vicinity of the former ones.

No evidence of correlation between p53 codon 72 polymorphism and risk of bladder or breast carcinoma in Tunisian patients

The TP53 gene, frequently mutated in human cancers, carries several polymorphisms. The one most informative and studied concerns codon 72; a single base changes the CGC (arginine) to CCC (proline). The arginine form was considered to be a significant risk factor in the development of cancer. However, various reports on this polymorphism are controversial. We carried out the same investigation in two groups of patients, a group with bladder cancer and another with breast cancer, and in healthy controls in two regions of our country, using an improved PCR-RFLP method. The number of Arg/Arg, Arg/Pro, and Pro/Pro genotypes was as follows: 21, 23, 3 and 13, 19, 2 for patients (total 47) and controls (34), respectively, in the first group; 18, 9, 3 and 19, 26, 4 for patients (30) and controls (49), respectively, in the second group. Statistical analysis of the genotype and allele frequencies did not reveal any difference between patients and controls in both groups except for a weak difference between the homozygotes to heterozygotes in the second group with a chi square of 4.1 (P = 0.045); the number of breast cancer patients is actually low (30) and should be increased in order to assess such a conclusion. Our overall results are therefore not consistent with a high risk associated with TP53 codon 72 polymorphism in breast and in bladder cancers.

Glucose dependent [correction of dependant] negative translational control of the heterologous expression of the preS2 HBV antigen in yeast

In the present study, we have compared the expression level of the genes encoding the viral Hepatitis B S and preS2 using two different yeast vectors, a constitutive one (YepIPT) and a galactose-inducible one (YepDP1-8). We showed that the S and preS2 mRNAs were present in equivalent amounts in both systems, while the corresponding proteins showed a different pattern. The S and preS2 proteins were efficiently produced after galactose induction. However, under the constitutive promoter, the S protein was synthesized at the same level in presence of 2% glucose or galactose whereas the preS2 protein was efficiently synthesized on galactose but absent on 2% glucose. The substitution of glucose by non-repressive carbon sources such as 2% galactose, ethanol or glycerol led to a significant expression of preS2. A high level of preS2 expression was also achieved by lowering the glucose concentration. Our data suggest that glucose exerts a concentration dependent negative translational control on the preS2 mRNA.

Translational control of human p53 expression in yeast mediated by 5'-UTR-ORF structural interaction

We have expressed human p53 cDNA in the yeast Saccharomyces cerevisiae and shown that the level of production and the length of the p53 protein depends on the presence of untranslated mRNA regions (UTRs). The expression of the ORF alone leads to a p53 protein of correct size (53 kDa) that accumulates to high levels, concomitantly with the presence of a small amount of a p40 protein (40 kDa). However, when either the entire 5'-UTR and a part of the 3'- or 5'-UTR alone is used, this leads to the production of small amounts of the 40 kDa truncated form only. The p40 protein corresponds to a truncated form of p53 at the C-terminal extremity since it reacts only with a monoclonal antibody recognising the N-terminal epitope. This effect on the amount and length of p53 protein had no correlation at the mRNA level, suggesting that translational control probably occurs through the 5'-UTR. We propose a model of structural interaction between this UTR and a part of the ORF mRNA for the regulation of p53 expression in this heterologous context.

Genotyping of Tunisian hepatitis B virus isolates based on the sequencing of preS2 and S regions

The S nucleotide sequences of five hepatitis B virus strains isolated from plasma samples of Tunisian patients with chronic hepatitis B were determined; the preS2 region of three of them were sequenced. According to the comparative analysis of S peptide sequences with the reported sequences in the database bank, the five hepatitis B strains were shown to be related to the D genotypic group, subtype ayw. The nature of residues at positions 125 and 127 allowed us to distinguish between each subtype of the D group and to class all five Tunisian sequences in the 'ayw2' subtype. Moreover, two of them (1366 and 523) contained a substitution of the invariant Cys69 by Arg and Cys221 by Phe, respectively. Potential structural modifications due to the Cys-Arg change are discussed.