The term epigenetics encompasses all the modifications that are stable across cell generations, but which do not imply any change in DNA sequence. Post-translational modifications of the histones and DNA methylation are the most studied types of epigenetic information due to their major impact on transcription. The link between epigenetics and cancer arises from the fact that epigenetic deregulations frequently participate in tumorigenesis by inactivation of tumour-suppressor genes. Since these deregulations are reversible, hopes of treatment rely on a better understanding of the maintenance mechanisms of the epigenetic information. Among the different pathways of transcription inhibition, DNA methylation is the simplest and one of the best characterized at the present time. Inhibitors of DNA methyltransferases are currently under clinical trials and already show promising results.

Medullary thyroid carcinoma (MTC) is a rare cancer which originates from the calcitonin producing "C" cells of thyroid gland. It presents in as isolated form or as part of the multiple endocrine neoplasia type 2 (MEN 2). The familial form of MTC which frequency remains underestimated, account for 25 to 40% of all MTC presentations. All hereditary forms are transmitted in an autosomal dominant manner and are due to proto-oncogene RET germ line mutations. Although MCT is relatively rare, preclinical or prebiological diagnosis can be achieved with genetic screening with high specificity and sensitivity. Early diagnosis is crucial for disease prevention. In this study we identified the first RET mutation underlying NEM 2A in Morocco. The C634Y mutation was present in the heterozygous state in a Moroccan family with MEN 2A. Genetic screening showed that six asymptomatic members of this family were not C364Y carriers. This report should contribute to the development of genetic screening for NEM 2 and F-MTC in Morocco.

Interindividual differences observed in the metabolism of xenobiotics have been attributed to the genetic polymorphism of genes, which code for enzymes involved in detoxification. This genetic variability seems to be associated with the individual's susceptibility to certain cancers, including nasopharyngeal carcinoma. In this study, we have investigated the genotypic frequencies of DNA polymorphisms of two detoxification's genes: the gluthatione-S-transferase (GST) and the N-acetyl transferase 2 (NAT2). The study has included 45 patients with nasopharyngeal carcinoma compared to 100 healthy Tunisian controls. The presence of the GSTM1 null and GSTT1 null polymorphism was screened by using a multiplex PCR procedure. A PCR-RFLP method was used to detect polymorphism for the most common alleles of the NAT2 gene. Allelic frequencies between the two groups were compared using a chi2 test and odds ratio with 95% confidence intervals were calculated. The results indicate that the genotypic frequency of GSTM10/0 between controls and patients was significantly different. This genotype confers an increased risk of nasopharyngeal carcinoma (Odds Ratio = 2.12, [0.64-4.7]). However, genotypic frequencies of NAT2*6/NAT2*6 were significantly higher in the group of nasopharyngeal carcinoma patients. The calculated Odds Ratio showed an association between this genotype and nasopharyngeal carcinoma. In conclusion, the increase of nasopharyngeal carcinoma risk in Tunisia seems to be associated with GSTM10/0 and NAT2*6/6 genotype.

Parathyroid carcinoma is a rare disease accounting for 1 to 5% of parathyroid neoplasms. This malignant tumour must be suspected when a severe primary hyperparathyroidism occurs with high hypercalcemia and elevated parathormon levels. At this time, a cervical mass is often palpable. Both head and neck ultrasonography and 99mTc-sestamibi scintigraphy are the best preoperative imaging tests to suspect and localize the tumour. Surgical approach with simultaneous tumorectomy and hemithyroidectomy, completed by selective neck dissection (level VI) is the treatment of choice. An elective lateral neck dissection should be performed if necessary. Tumour control should be monitored by regular measurement of calcium and parathormon levels. Local recurrence or metastasis risk is 30 to 70% and the 5 year overall survival about 50 to 80%. In case of recurrence, aggressive surgical management should be applied and adjuvant radiation therapy may be discussed.

A major obstacle to the expansion of abnormal cells with significant proliferative potential is the induction of either cellular senescence or programmed cell death. Consequently, oncogene-driven hyperproliferation must be associated with apoptosis inhibition to allow malignant outgrowth. The oncogenic cooperation of N-Myc and Twist 1 in the development of neuroblastoma, the most common and deadly solid tumour of childhood, perfectly illustrates such a process. N-Myc promotes cell proliferation whereas Twist 1 counteracts its pro-apoptotic properties by knocking-down the ARF/p53 pathway. This observation provides a mechanistic explanation for the rarity of p53 mutations in neuroblastomas. It also highlights the involvement of two crucial regulators of embryogenesis in human cancer development. In this review, we discuss the possible role of Twist 1 in tumour progression, based on the numerous recent studies reporting its overexpression in a variety of human cancers.

Improved survival of pediatric cancer patients will lead to an increase of late sequellae such as secondary malignant neoplasms (SMN). Specific pediatric factors predisposing to these SMN are as follows: long expecting duration of life, high cellular proliferative potential, toxicity of often combined cancer therapies (radio- and chemotherapies) and more frequent genetic predisposition to cancer. Better understanding of these factors could improve patients management and could lead to the development of less toxic future therapies with the hope to decrease the risk of SMN.

Acute leukemia of megakaryocyte lineage (AML-7) is a rare entity defined by a blastic proliferation of which a part (>or= 50%) is represented by megakaryoblasts. We report the case of a 95 year old woman presenting a AML-7 secondary to a myelodysplastic syndrome (MDS), that represents an unusual form of MDS acutisation.

Multiple myeloma is a blood disease that is often easy to diagnose, relying on a combination of an excessive medullary plasmacytosis, a serum and/or urinary monoclonal immunoglobulin and one or several signs of organ involvement (anemia, renal failure, bone lesions, hypercalcaemia, infections). The beta2m, serum albumin, and certain chromosomal anomalies of the malignant clone are the essential prognostic factors. Intensive treatment with auto-transplantation of stem cells of peripheral blood is a significant development from which patients less than or equal to 65 years of age have benefited. The diphosphonates are combined with chemotherapy in order to limit the effect on bones, and recombinant erythropoietin is used in certain patients. Above all, therapeutic progress has been made thanks to thalidomide, bortezomib and lenalidomide, even if the optimal utilisation of these molecules is still to be determined.

We present the case of large desmoid tumor of the anterior chest wall with pleural involvement, which persistently progressed despite hormonotherapy, chemotherapy and surgery. After many years of therapeutic failures, given the tumor size and its hemodynamic repercussions, the patient was presumed to be incurable and only supportive measures were given. One year later, the desmoid tumor had completely disappeared. Even though wide surgical excision is an essential element in the treatment of desmoid tumors, spontaneous regression may occur in very advanced disease.

Tumor suppressor gene inactivation as proposed by the Knudson model implies a sequential inactivation of two alleles of a gene. For example, the first allele is inactivated by a missense mutation, and the second one is inactivated by a deletion or insertion. The alteration of the p53 tumor suppressor gene is far to correspond only to this model. In the great majority of cancers, the mutated allele of p53 coexists with the normal allele. It is well known that the transcriptional activity is one of the most important functions of p53. The p53 protein is active as a tetramer (this complex activates the expression of targeted genes by binding to its consensus DNA sequence called the p53 response element). Experimental evidence shows that wild-type p53 interacts with mutant proteins to form heterotetramers. In association with wild-type proteins, mutant proteins drive the wild-type subunits into a mutant conformation. This association leads to a loss of trans-activating function. The capacity of mutant subunits to form heterotetramers with wild-type subunits and to commit them into a mutant conformation is called << dominant negative effect >>. Many p53 mutant proteins possess this dominant negative activity. Recently, several factors, which are implicated in the control of the dominant negative activity of p53 mutants, have been identified. The elucidation of these complex molecular functions, which are implicated in the dominant negative activity of the p53 mutated protein represents an important aspect in the comprehension of the biological mechanisms involved in carcinogenesis.

Nevoid basal cell carcinoma syndrome is an autosomal dominant disorder characterized by developmental abnormalities and cancer predisposition. The PTCH 1 gene, the human homolog of the Drosophila segment polarity gene patched, has been shown to be involved in the development of nevoid basal cell carcinoma syndrome. PTCH 1 is mapped to chromosome 9q22.3. The aim of the present study was to report on clinical and genetic characteristics in patients followed for nevoid basal cell carcinoma syndrome and to compare them to the data in the literature.

Gastrointestinal stromal tumors (GISTs) are the most frequent mesenchymal tumors of the gastrointestinal tract. Major advances in their definition and classification and the understanding of their molecular mechanisms have recently been made. These advances have resulted in the delineation of a treatment that has become a model of targeted therapy in oncology. GISTs are defined as tumors of the gastrointestinal tract, but also of the mesentery and peritoneum, constituted by a proliferation of usually spindle-shaped, rarely epithelioid cells, usually, but not consistently expressing the KIT protein. Most GISTs are associated with molecular abnormalities in two target genes: KIT (which encodes the KIT protein) and PDGFRA (which encodes the A chain of the PDGF receptor). The diagnosis of GIST relies on histological arguments (proliferation of spindle-shaped cells in 70% of cases, of epithelioid cells in 20%; histological variants are rare and sometimes misleading) and on immunohistochemical arguments (expression of KIT in 95%, usually associated with CD34 expression in 60%-70% of cases). The demonstration of mutations in target genes is required only in cases that are histologically suggestive but KIT-negative; beyond this indication, this is only undertaken in research protocols. The differential diagnosis of GIST includes the other mesenchymal tumors of the gastrointestinal tract, such as leiomyomas and leiomyosarcomas, and the digestive locations of some sarcomas; it relies on both histological and immunohistochemical arguments. The evaluation of the prognosis is essential. According to the current concept, every GIST carries a risk of malignancy, which may vary from very low to very high. Prognosis is based on a simple algorithm using two histoprognostic parameters, i.e., tumor size and mitotic index. The treatment of localized GIST is surgical resection, which must be complete; that of advanced or unresectable GIST is based on the use of a targeted therapy, imatinib, which is a pharmacological antagonist of the KIT protein. Proper understanding and utilisation of the diagnostic criteria and classification of GIST by pathologists are essential for good patient management.

In the vertebrate embryo, the ventral wall of the aorta is the major site of Haematopoietic Stem Cell (HSC) production. HSC, which are at the basis of the adult blood cells hierarchy, are generated from Endothelial Cells (EC) through a complex cascade of molecular events. The transcription factor RUNX1/AML1 and its cofactor CBFbeta, disrupted in 20 % of acute myeloid leukaemia cases, are thought to control this process. A detailed gene expression analysis of RUNX1 and its associated factors in the chick embryo, prompted us to speculate on the molecular cascades involved in HSC production. The function of RUNX1 is however tightly regulated at several levels, rendering analysis through classical genetic approaches very difficult to manage. To offer new possibilities of investigation, we have designed a technique to target the blood forming system in vivo. Gene transfer was achieved by lipofection following delivery by intra-cardiac injection in the avian embryo. This method was optimised to allow a wide range of functional analysis, either by gain or loss of function, in a simple and efficient manner. In combination with experimental advantages of the avian embryo, this new system of genetic analysis allows us to perform a detailed study of RUNX1 function in HSC production from EC.

Recent studies have led a different view about membrane receptors. While a receptor used to be considered as inactive until bound by its ligand, it has been proposed that some receptors may also be active in the absence of their ligand. These so-called dependence receptors induce a specific death signal when the ligand is absent from the cell. Therefore, the expression of one of these receptors drives the cell to become dependent on the presence of the ligand for its survival. We have hypothesized that this mechanism allows inhibition of tumor growth, by inducing apoptosis of "abnormal" cells that would usually grow when ligand are unavailable--i.e., during local growth of tumor cells or growth beyond primary tumor site -. Along this line, back in the early 90s, Vogelstein and colleagues suggested that a gene called DCC (for "deleted in colorectal cancer") could be a tumor suppressor gene because it was found to be deleted in more than 70 % of colorectal cancers, as well as in many other cancers. During the last fifteen years, controversial data have failed to firmly establish whether DCC is indeed a tumor suppressor gene. However, our observation that DCC behaves as a dependence receptor that induces cell death unless its ligand netrin-1 is present, together with the fact that mice engineered to block DCC-induced cell death by overexpressing netrin-1 are predisposed to develop colorectal tumors, strengthen the role of dependence receptors as tumor suppressors. In this review, we will describe the implication of the netrin-1/receptor pairs as novel negative regulators of tumor development.

Cutaneous melanoma remains a management challenge. Melanoma is the leading cause of death from skin tumors worldwide. Melanoma progression is well defined in its clinical, histopathological and biological aspects, but the molecular mechanism involved and the genetic markers associated to metastatic dissemination are only beginning to be defined. The recent development of high-throughput technologies aimed at global molecular profiling of cancer is switching on the spotlight at previously unknown candidate genes involved in melanoma. Among those genes, BRAF is one of the most supposed to be of interest and targeted therapies are ongoing in clinical trials. In familial melanoma, germline mutations in two genes, CDKN2A and CDK4, that play a pivotal role in controlling cell cycle and division. It is hope that this better understanding of the biologic features of melanoma and the mechanisms underlying tumor-induced immunosuppression will lead to efficaceous targeted therapy.

This year, the innovations were numerous in sarcomas. Important progress were accomplished in the search for predictive factors which make it possible to propose to the patient a personalized treatment with the therapeutic ones reduced in the event of good prognosis or on the contrary aggressive steps in the event of bad prognosis. These prognostic factors can be genetic or clinical. Progress were also accomplished in the clinical field with the research of the most adapted therapeutic strategies and of advanced in various drugs of chemotherapy in particular the ET-743. Lastly, research is active and of many ways are tested into preclinic with a detailed attention on the way of the angiogenesis.