Moncef Mokni

Poly(ADP-ribose) polymerase-1, a novel partner of progesterone receptors in endometrial cancer and its precursors

Endometrial carcinomas are the most common malignancy of the female genital tract. Although the downregulation of the progesterone receptor (PR) in the progression of endometrioid carcinomas (ECs) has been well documented, the mechanism of PR alteration in endometrioid carcinogenesis is poorly understood. Recently, biochemical studies have shown that the DNA strand break‐sensing molecule poly(ADP‐ribose) polymerase (PARP‐1) was associated with the DNA binding domain of PR. In our present study, we show that in normal endometrial epithelium, the expression level of PARP‐1 protein is high in the proliferative phase but markedly decreases during the secretory phase. Interestingly, PARP‐1 expression gradually increases in nonatypical and atypical endometrial hyperplasia, reaching its highest level in grade I, and decreases significantly toward grade III ECs. Notably, PARP‐1 and PR expressions, in each stage, are positively correlated (p < 0.0001), with the exception of nonendometrioid carcinomas. Thus, these data suggest that PARP‐1 is substantially involved in the regulation of progesterone action in the development of ECs.

Presence of simian virus 40 DNA sequences in diffuse large B-cell lymphomas in Tunisia correlates with aberrant promoter hypermethylation of multiple tumor suppressor genes.

The simian virus SV40 (SV40), a potent DNA oncogenic polyomavirus, has been detected in several human tumors including lymphomas, mainly in diffuse large B‐cell type (DLBCL). However, a causative role for this virus has not been convincingly established. Hypermethylation in promoter regions is a frequent process of silencing tumor suppressor genes (TSGs) in cancers, which may be induced by oncogenic viruses. In this study, we investigated the relationship between the presence of SV40 DNA sequences and the methylation status of 13 TSGs in 108 DLBCLs and 60 nontumoral samples from Tunisia. SV40 DNA presence was investigated by PCR assays targeting the large T‐antigen, the regulatory and the VP1 regions. Hypermethylation was carried out by methylation‐specific PCR. SV40 DNA was detected in 63/108 (56%) of DLBCL and in 4/60 (6%) of nontumoral samples. Hypermethylation frequencies for the tested TSGs were 74% for DAPK, 70% for CDH1, SHP1, and GSTP1, 58% for p16, 54% for APC, 50% for p14, 39% for p15, 19% for RB1, 15% for BLU, 3% for p53, and 0% for p300 and MGMT. No hypermethylation was observed in nontumoral samples. Hypermethylation of SHP1, DAPK, CDH1, GSTP1 and p16 genes were significantly higher in SV40‐positive than in SV40‐negative DLBCL samples (p values ranging from 0.0006 to <0.0001). Our findings showed a high prevalence of SV40 DNA in DLBCLs in Tunisia. The significant association of promoter hypermethylation of multiple TSGs with the presence of SV40 DNA in DLBCLs supports a functional effect of the virus in those lymphomas.

Correlation between the DNA global methylation status and progesterone receptor expression in normal endometrium, endometrioid adenocarcinoma and precursors

Endometrial carcinomas are the most common malignancy of the female genital tract and the third most common cancer in women. Progesterone and oestrogen receptors (PRs, ERs) are the most widely documented prognostic and predictive factors in endometrioid adenocarcinoma. Besides the hormonal pathway involved in the progression of preneoplastic and neoplastic lesions, alterations of the DNA methylation status have been shown to be an early signal of tumorigenesis. In this study, we show that in normal endometrium, during the proliferative phase, DNA methylation and PR expression are high, with a significant decline towards the end of the secretory phase and a gradual increase in non-atypical and atypical endometrial hyperplasia; they reach their highest level in grade I, then decrease significantly in grade-II and grade-III endometrioid adenocarcinomas. During each stage, a significant positive correlation is observed between DNA methylation and PR (P<0.0001). The strong parallelism between DNA methylation and PR expression precludes establishing a precise determination regarding the timing of these events, clearly involved in the genesis of endometrioid adenocarcinoma.

p16INK4A overexpression and HPV infection in uterine cervix adenocarcinoma.

Human papillomaviruses (HPVs) are causally involved in the genesis of cervical carcinomas and their precursors, and there is a strong relationship between the cyclin-dependant kinase inhibitor p16INK4A and HPV infection. This study was carried out to assess the correlations between p16INK4A expression as an early biomarker of the endocervical adenocarcinoma and HPV infection. p16INK4A expression and HPV typing were performed on 46 samples including 5 normal endocervix, 9 benign lesions of the endocervix, 25 endocervical adenocarcinomas, and 7 endometrioid adenocarcinomas of the uterine corpus. A semiquantification of the p16INK4A immunostaining was realized (using both the staining intensity and the percentage of positive cells) and was graded from 0 to 15. All of the 25 endocervical adenocarcinomas overexpressed p16INK4A; the adjacent epithelium and the connective tissue were strictly negative. No p16INK4A was detected in nine benign endocervical lesions and in five normal endocervix. Few endometrioid adenocarcinomas of the uterine corpus that infiltrate the endocervix exhibited a low immunoreactivity (score 0/15 or 1/15). This pattern of expression is significantly associated with HPV infection (p<10−3), mainly high-risk HPV types (p=0.02). Our results suggest that p16INK4A is a putative molecular biomarker that consistently discriminates uterine cervix adenocarcinomas from benign lesions and from endometrioid adenocarcinomas of the uterine corpus .

Trends in the incidence of cancer in the Sousse region, Tunisia, 1993-2006.

In this article, we analyzed trends in incidence rates of the major cancer sites for a 14‐year period, 1993–2006, in the Sousse region localized in the centre of Tunisia. Five‐year age‐specific rates, crude incidence rates (CR), world age‐standardized rates (ASR), percent change (PC) and annual percent change (APC) were calculated using annual data on population size and its estimated age structure. A total of 6,975 incident cases of cancer were registered, with a male to‐female sex ratio of 1.4:1. ASRs showed stable trends (−0.1% in males, and +1.0% in females). The leading cancer sites in rank were lung, breast, lymphoma, colon‐rectum, bladder, prostate, leukemia, stomach and cervix uteri. For males, the incidence rates of lung, bladder and prostate cancers remained stable over time. While, cancers of colon‐rectum showed a marked increase in incidence (APC: +4.8%; 95% CI: 1.2%, 8.4%) and non‐Hodgkins lymphoma (NHL) showed a notable decline (APC: −4.4%; 95% CI: −8.2, −0.6). For females, cancers of the breast (APC: +2.2%; 95% CI: 0.4%, 4.0%) and corpus uteri (APC: +7.4%; 95% CI: 2.8%, 12.0%) showed a marked increase in incidence during the study period, while the cervix uteri cancer decreased significantly (APC: −6.1%; 95% CI: −9.2%, −3.0%). The results underline the increasing importance of cancer as a cause of mortality and morbidity in Tunisia. Our findings justify the need to develop effective program aiming at the control and prevention of the spread of cancer amongst Tunisian population.

Prevalence and characteristics of the MMTV-like associated breast carcinomas in Tunisia

The involvement of a retrovirus homologous to the mouse mammary tumor virus (MMTV) in the pathogenesis of human breast cancer (BC) has long been assumed, but has never been proven. Previous studies have reported the detection of MMTV-like env sequences in variable proportions that did not exceed 40% of BC cases in several countries. However, these viral sequences have been found in higher proportion (74%) in Tunisian diagnosed with BC during the seventies. This study is an attempt to evaluate the current prevalence of MMTV-like env gene in BC in Tunisian women. We used semi-nested PCR that amplify a 190-bp MMTV-like env sequence, followed by direct sequencing to screen a series of 122 cases of BC randomly selected. The findings were correlated to clinicopathological data and immunohistochemical expression status of progesterone and oestrogen receptors, HER2, and P53. Specific MMTV-like env sequences were found in 17 (13.9%) cases of breast carcinomas, whereas the same sequences were not detected in matched normal breast tissues. The presence of the viral sequences correlates inversely with progesterone receptor expression (6.8% versus 20.3%; P=0.03) and HER2 overexpression (3.1% versus 17.7%; P=0.04). This present study confirms the presence of MMTV-like env sequences in BC in Tunisian women but describes an important decrease in the prevalence of the viral sequences compared with previous studies. This reduction may be due to some changes in the virological characteristics or exposure to the virus.

Promoter hypermethylation of CDH13, DAPK1 and TWIST1 genes in precancerous and cancerous lesions of the uterine cervix.

Aberrant DNA methylation is an early event in carcinogenesis and could serve as an additional molecular marker for the early diagnosis. The study was performed to investigate the promoter methylation of DAPK1, CDH13, and TWIST1 genes in uterine cervix lesions in an effort to examine whether this epigenetic event is involved in the process of cervical carcinogenesis, and whether it might be used as a molecular marker of cervical lesions. We conducted a retrospective study of 60 uterine cervix specimens, including 8 normal tissue samples, 10 benign lesions, 28 precancerous lesions (CIN1-3), and 14 squamous cell carcinomas (SCC). DNA hypermethylation was investigated using methylation-specific PCR. Immunohistochemistry was used to find p16(INK4A) overexpression. No hypermethylated promoters were detected in normal tissues and benign lesions. However, promoter hypermethylation of CDH13, TWIST1, and DAPK1 increased progressively from CIN1 to cancer, reaching values higher than 50% for cancer. DAPK1 and CDH13 displayed a significantly increased frequency of promoter methylation with progressively more severe cervical neoplasia (p<0.05). A statistically significant association was observed between p16(INK4A) expression and hypermethylation of DAPK1, TWIST1, and CDH13 (p<0.0001). Hypermethylation of CDH13, DAPK1, and TWIST1 promoters is an early event in the initiation and progression of cervix neoplasia. CDH13, DAPK1, and TWIST1 genes are potential biomarkers of cervical cancer risk.

Distribution of molecular breast cancer subtypes among Tunisian women and correlation with histopathological parameters: A study of 194 patients

According to the immunohistochemical test of estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor-2 (Her-2), breast cancer can be divided into 4 molecular subtypes: luminal A, luminal B, Her-2, and basal-like. The purpose of this study is to correlate these subtypes with clinicopathological features. We have selected from the files of our Pathology Department 194 breast carcinomas which had already been studied for ER, PR, and Her-2, diagnosed between January 2008 and October 2009. The cases were classified into 4 molecular subtypes. The clinicopathological characteristics of each subtype were compared. The luminal A subtype was the most prevalent (51.5%). The basal-like and Her-2 subtypes were significantly correlated to a large tumor size, a high tumor grade, and a high-volume nodal involvement (≥4). On multivariate analysis, patients with the Her-2 and basal-like subtypes were 4.2 (95% CI, 1.3-13.5) times more likely to have developed metastases in four or more lymph nodes than those with luminal tumors. Our analysis revealed that the Her-2 and basal-like subtypes are correlated with factors associated with a poor prognosis. The luminal A subtype is the commonest subtype, showing that breast cancer in Tunisia has no aggressive phenotype.

The Transesophageal Echocardiographic Diagnosis of Left Atrial Myxoma Simulating a Left Atrial Thrombus in the Setting of Mitral Stenosis

We report the case of a 56‐year‐old woman with a history of rheumatic heart disease. The clinical, electrocardiographic, and radiologic findings suggested mitral stenosis. Left atrial obstructive myxoma simulating a thrombus was found by transthoracic echocardiography (TTE). The diagnosis was established by use of transesophageal echocardiography (TEE), confirmed after surgery and by anatomical investigation. Cardiac myxoma associated with mitral stenosis may be difficult to diagnose accurately using TTE. The advantage of TEE in this case and in patients with mitral stenosis is emphasized. (ECHOCARDIOGRAPHY, Volume 21, May 2004)

Embryotoxicity and fetotoxicity following intraperitoneal administrations of hexavalent chromium to pregnant rats

Heavy metals are omnipresent in the environment, and industrial use has greatly increased their presence in soil, water and air. Their inevitable transfer to the human food chain remains an important environmental issue as many heavy metals cause a range of toxic effects, including developmental toxicity. Administration of chromium VI (1 and 2 mg/kg as potassium dichromate) through intraperitoneal (i.p.) injection during organogenesis (days 6 to 15 of gestation) in rats revealed embryo- and fetotoxic effects. Reduced fetal weight, retarded fetal development, number of fetuses per mother and high incidences of dead fetuses and resorptions in treated mothers were also observed. Gross morphological abnormalities, such as displayed form of edema, facial defect, lack of tail, hypotrophy, severs subdermal haemorrhage patches and hypotrophy of placenta were observed in fetuses after chromium VI-treated mothers. A skeletal development of fetuses presented an incomplete ossification in nasal, cranium, abdominal or caudal bones in rats treated with 1 mg/kg of chromium, whereas rats treated with 2 mg/kg showed ossification and absence of the sacral vertebrae compared with the control. At a higher dose of chromium, histological changes were found in fetuses with atrophy of theirs vital organs. Placental histological observations revealed a pronounced morphological alteration, with atrophy of decidual cells, a degenerated of chorionic villi and hypertrophy of blood lacuna. The present study suggests a risk to the developing embryo when the mother is exposed to a high concentration of chromium VI during organogenesis.