Thiopurine Drugs in the Treatment of Ulcerative Colitis: Identification of a Novel Deleterious Mutation in TPMT.

Chronic inflammatory bowel disease (IBD) includes Crohn's disease and ulcerative colitis. Both are characterized by inflammation of part of the digestive tract lining. Azathioprine (AZA) is a well-known immunosuppressant that has been known for many years for its ability to provide long-term disease remission in IBDs, but has important side effects, most of which are related to a single nucleotide polymorphism in the gene for thiopurine methyltransferase (TPMT), which ensures the degradation and efficacy of AZA. Since a direct correlation between TPMT gene polymorphisms and the haematological toxicity of the AZA treatment has been widely demonstrated, TPMT genotyping has been made necessary prior to any introduction of AZA. The monitoring of thiopurine metabolites presents one of the factors that limit wide adaptation of these thiopurines in clinical practice. Thus, identifying patients with asymmetric metabolism could help clinicians provide an ideal treatment recommendation to improve response and reduce adverse effects. Here, we review the role of AZA in the treatment of IBD and discuss the usefulness of TPMT genotyping to guide clinical decision-making. In addition, we report the identification of a new molecular alteration, never described, TPMT mutation affecting the TPMT activity and responsible for deleterious side effects in a clinical case of a 20-year-old woman patient.

Facial cutaneo-mucosal venous malformations can develop independently of mutation of TEK gene but may be associated with excessive expression of Src and p-Src.

We aimed to search for mutations in the germline and somatic DNA of the TEK gene and to analyze the expression level of Src and phospho-Src (p-Src) in tumor and healthy tissues from patients with facial cutaneo-mucosal venous malformations (VMCM). Eligible patients from twelve families and thirty healthy controls were recruited respectively at the Departments of Stomatology and Oral Surgery, and Transfusion Medicine of Tlemcen University Medical Centre. Immunoblot analyses of Src and p-Src were performed after direct DNA sequencing. No somatic or germline mutations were found in all the 23 exons and their 5' and 3' intronic flanking regions, except for one case in which a c.3025+20-3025+22 del mutation was highlighted at the intron 15, both in the germline and somatic DNA. Additionally, elevated expression levels of Src and p-Src were observed only in the patient with such mutation. However, when normalized to ß-actin, the overall relative expression levels of both Src and p-Src were significantly increased in VMCM tissues when compared to healthy tissues (for both comparisons, p <0.001). In conclusion, we confirm the outcomes of our previous work suggesting that VMCM can develop independently of mutation of the TEK gene. Additionally, the results for Src activity are of particular interest in the context of specific targeted therapies and biological diagnosis. Nevertheless, such a conclusion should be confirmed through a mechanistic study and/or in a satisfactory number of patients.

The RIP140 gene is a transcriptional target of E2F1.

RIP140 is a transcriptional coregulator involved in energy homeostasis and ovulation which is controlled at the transcriptional level by several nuclear receptors. We demonstrate here that RIP140 is a novel target gene of the E2F1 transcription factor. Bioinformatics analysis, gel shift assay, and chromatin immunoprecipitation demonstrate that the RIP140 promoter contains bona fide E2F response elements. In transiently transfected MCF-7 breast cancer cells, the RIP140 promoter is transactivated by overexpression of E2F1/DP1. Interestingly, RIP140 mRNA is finely regulated during cell cycle progression (5-fold increase at the G1/S and G2/M transitions). The positive regulation by E2F1 requires sequences located in the proximal region of the promoter (-73/+167), involves Sp1 transcription factors, and undergoes a negative feedback control by RIP140. Finally, we show that E2F1 participates in the induction of RIP140 expression during adipocyte differentiation. Altogether, this work identifies the RIP140 gene as a new transcriptional target of E2F1 which may explain some of the effect of E2F1 in both cancer and metabolic diseases.

[Autoantibodies against tumor-related antigens: new tools for early detection of lung cancer]. / Auto-anticorps dirigés contre les antigènes associés aux tumeurs : nouveaux outils pour la détection précoce du cancer du poumon.

Because of its development marked by a long preclinical phase and the difficulties to screen patients, lung cancer is usually diagnosed at an advanced stage of disease, even in high-risk populations. The advent of new molecular tools, including proteomics, has promoted the study of the humoral response to cancer and has allowed the demonstration of the appearance of a large number of autoantibodies against tumor antigens in the serum of patients. In this article, we describe the different molecular approaches used to identify autoantibodies and immunogenic proteins and we present the different clinical studies applied to early detection of lung cancer. Early trials demonstrated the development of a humoral response several months before the first radiographic or clinical signs. Further studies are under evaluation and are intended to identify early forms of cancer in populations with high cancer risk. Many efforts are made in the implementation of robust and reproducible tests that could help to the emergence in the future of such biological tools in clinical practice.

The transcriptional coregulator RIP140 represses E2F1 activity and discriminates breast cancer subtypes.

PURPOSE: Receptor-interacting protein of 140 kDa (RIP140) is a transcriptional cofactor for nuclear receptors involved in reproduction and energy homeostasis. Our aim was to investigate its role in the regulation of E2F1 activity and target genes both in breast cancer cell lines and in tumor biopsies. EXPERIMENTAL DESIGN: Glutathione S-transferase pull-down assays, coimmunoprecipitation experiments, and chromatin immunoprecipitation analysis were used to evidence interaction between RIP140 and E2F1. The effects of RIP140 expression on E2F1 activity were determined using transient transfection and quantification of E2F target mRNAs by quantitative real-time PCR. The effect on cell cycle was assessed by fluorescence-activated cell sorting analysis on cells overexpressing green fluorescent protein-tagged RIP140. A tumor microarray data set was used to investigate the expression of RIP140 and E2F1 target genes in 170 breast cancer patients. RESULTS: We first evidenced the complex interaction between RIP140 and E2F1 and showed that RIP140 represses E2F1 transactivation on various transiently transfected E2F target promoters and inhibits the expression of several E2F1 target genes (such as CCNE1 and CCNB2). In agreement with a role for RIP140 in the control of E2F activity, we show that increasing RIP140 levels results in a reduction in the proportion of cells in S phase in various human cell lines. Finally, analysis of human breast cancers shows that low RIP140 mRNA expression was associated with high E2F1 target gene levels and basal-like tumors. CONCLUSION: This study shows that RIP140 is a regulator of the E2F pathway, which discriminates luminal- and basal-like tumors, emphasizing the importance of these regulations for a clinical cancer phenotype.

Specific activity of class II histone deacetylases in human breast cancer cells.

Although numerous studies have underlined the role of histone deacetylases (HDAC) in breast physiology and tumorigenesis, little is known on the particular contribution of the various classes of HDACs in these processes. Using estrogen receptor-alpha (ERalpha)-positive MCF-7 breast cancer cells, the effects of MC1575 and MC1568, two novel class II-specific HDAC inhibitors, were analyzed on cell proliferation, apoptosis, and estrogen signaling. The specificity of these HDAC inhibitors was validated by measuring histone and alpha-tubulin acetylation and by the specific in vitro inhibition of recombinant HDAC4 using histone and nonhistone substrates, contrasting with the lack of inhibition of class I HDACs. In addition, MC1575 did not inhibit class I HDAC gene expression, thus confirming the specific targeting of class II enzymes. Similar to trichostatin A (TSA), MC1575 displayed a dose-dependent antiproliferative effect and induced cell cycle arrest although this blockade occurred at a different level than TSA. Moreover, and in contrast to TSA, MC1575 had no effect on MCF-7 cells apoptosis. Interestingly, MC1575 was able to increase p21(waf1/CIP1) mRNA levels but did not regulate the expression of other genes such as cyclin D1, p27, p14(ARF), Bcl2, Baxalpha, Trail-R1, and Trail-R2. Finally, MC1575 strongly induced ERbeta gene expression but did not decrease ERalpha expression, nor did it switch hydroxytamoxifen to an agonist activity. Altogether, these data suggest that the class II HDAC subfamily may exert specific roles in breast cancer progression and estrogen dependence.

Differential involvement of mitochondria during ursolic acid-induced apoptotic process in HaCaT and M4Beu cells.

Ursolic acid (UA) is a pentacyclic triterpenoid compound which exists widely in nature and is known to have a pleitropic biological activity profile. For the last few decades, extensive work has been carried out to establish its biological activities and pharmacological actions. It is described as a promising chemopreventive agent with an antiproliferative effect on cancer cells that stems from its ability to induce apoptosis. We investigated and compared the role played by mitochondria during the apoptotic process induced by UA in human HaCaT-derived keratinotic cells and M4Beu human melanoma cells. In both cell lines, UA induced significant caspase-3 activation, the downstream central effector of apoptosis. Subsequent JC-1/TOTO-3 double staining clearly demonstrated that UA induces strong mitochondrial-transmembrane potential collapse in M4Beu cells, while mitochondria from HaCaT-treated cells remain largely unstimulated. This was confirmed by Western blot analysis, which revealed a Bax/Bcl-2-balance change in favor of Bax, the proapoptotic member, in UA-treated M4Beu cells. It can be concluded that UA induces apoptosis in M4Beu through the mitochondrial pathway, while other mechanisms are activated in the case of HaCaT cells.

The nuclear receptor transcriptional coregulator RIP140.

The nuclear receptor superfamily comprises ligand-regulated transcription factors that control various developmental and physiological pathways. These receptors share a common modular structure and regulate gene expression through the recruitment of a large set of coregulatory proteins. These transcription cofactors regulate, either positively or negatively, chromatin structure and transcription initiation. One of the first proteins to be identified as a hormone-recruited cofactor was RIP140. Despite its recruitment by agonist-liganded receptors, RIP140 exhibits a strong transcriptional repressive activity which involves several inhibitory domains and different effectors. Interestingly, the RIP140 gene, located on chromosome 21 in humans, is finely regulated at the transcriptional level by various nuclear receptors. In addition, the protein undergoes several post-translational modifications which control its repressive activity. Finally, experiments performed in mice devoid of the RIP140 gene indicate that this transcriptional cofactor is essential for female fertility and energy homeostasis. RIP140 therefore appears to be an important modulator of nuclear receptor activity which could play major roles in physiological processes and hormone-dependent diseases.

Ursolic acid induces apoptosis through mitochondrial intrinsic pathway and caspase-3 activation in M4Beu melanoma cells.

Over the coming years, skin cancer could become a significant public health problem. Previous results indicate that ursolic acid (UA), a pentacyclic triterpene acid, has pleiotropic biologic activities such as antiinflammatory and antiproliferative activities on cancer cells. As UA represents a promising chemical entity for the protection of human skin, in agreement with tests done by the cosmetic industry, we investigated its effects on the M4Beu human melanoma cell line. In this report, we demonstrated for the first time that UA had a significant antiproliferative effect on M4Beu, associated with the induction of an apoptotic process, characterized by caspase-3 activation, the downstream central effector of apoptosis. We demonstrated that UA-induced apoptosis was dependent on the mitochondrial intrinsic pathway, as shown by transmembrane potential collapse (DeltaPsim) and by alteration of the Bax-Bcl-2 balance, with a concomitant increase in Bax expression and decrease in Bcl-2 expression. We also showed that UA-induced DeltaPsim was associated with apoptosis-inducing factor leakage from mitochondria. Taken together, our results suggest that UA-induced apoptosis on M4Beu cells is accomplished via triggering of mitochondrial pathway. In conclusion, UA could be an encouraging compound in the treatment or prevention of skin cancer and may represent a new promising anticancer agent in the treatment of melanoma.

Ursolic acid induces apoptosis through caspase-3 activation and cell cycle arrest in HaCat cells.

Ursolic acid (UA) is a pentacyclic triterpene compound isolated from many kinds of medicinal plants and present in human diet. In this study, we investigated the pro-apoptotic effect of UA on HaCat derived keratinocyte cell line. Treatment with UA decreased the viability of HaCat cells in a concentration- and time-dependent manner. In addition, cell cycle analysis revealed that UA treated HaCat cells were blocked predominantly in G1 phase. Moreover, expression of p21WAF1, a cell cycle regulator, was increased by UA, indicating that UA-induced cell cycle arrest could be mediated through p21WAF1. During UA treatment, we also demonstrated that p53 was phosphorylated at serine 392 and translocated to the nucleus. It is well established that p53 achieves its tumor suppressor activity by inducing apoptosis on cells. To define the apoptotic process in our system, we examined effect of UA on caspase activities, and demonstrated caspase-3 activation. In conclusion, our results suggest that UA induces: i) cell cycle arrest concomitantly with the apparition of the apoptotic sub group G1 peak, and ii) cell death through apoptosis, which is mediated by caspase-3.