Interactions between microsatellite instability and human gut colonization by Escherichia coli in colorectal cancer.

Recent studies suggest that colonization of colonic mucosa by pathogenic Escherichia coli could be involved in the development of colorectal cancer (CRC), especially through the production of genotoxins such as colibactin and/or by interfering with the DNA mismatch repair (MMR) pathway that leads to microsatellite instability (MSI). The present study, performed on 88 CRC patients, revealed a significant increase in E. coli colonization in the MSI CRC phenotype. In the same way, E. coli persistence and internalization were increased in vitro in MMR-deficient cells. Moreover, we demonstrated that colibactin-producing E. coli induce inhibition of the mutL homologue 1 (MLH1) MMR proteins, which could lead to genomic instability. However, colibactin-producing E. coli were more frequently identified in microsatellite stable (MSS) CRC. The present study suggests differences in the involvement of colibactin-producing E. coli in colorectal carcinogenesis according to the CRC phenotype. Further host-pathogen interactions studies should take into account CRC phenotypes.

Clinical validation of the detection of KRAS and BRAF mutations from circulating tumor DNA.

Assessment of KRAS status is mandatory in patients with metastatic colorectal cancer (mCRC) before applying targeted therapy. We describe here a blinded prospective study to compare KRAS and BRAF mutation status data obtained from the analysis of tumor tissue by routine gold-standard methods and of plasma DNA using a quantitative PCR-based method specifically designed to analyze circulating cell-free DNA (cfDNA). The mutation status was determined by both methods from 106 patient samples. cfDNA analysis showed 100% specificity and sensitivity for the BRAF V600E mutation. For the seven tested KRAS point mutations, the method exhibited 98% specificity and 92% sensitivity with a concordance value of 96%. Mutation load, expressed as the proportion of mutant alleles in cfDNA, was highly variable (0.5-64.1%, median 10.5%) among mutated samples. CfDNA was detected in 100% of patients with mCRC. This study shows that liquid biopsy through cfDNA analysis could advantageously replace tumor-section analysis and expand the scope of personalized medicine for patients with cancer.

Anticancer activity of silver-N-heterocyclic carbene complexes: caspase-independent induction of apoptosis via mitochondrial apoptosis-inducing factor (AIF).

Fourteen silver(I) complexes bearing N-heterocyclic carbene (NHC) ligands were prepared and evaluated for anticancer activity. Some of these were found to exhibit potent antiproliferative activity toward several types of human cancer cell lines, including drug-resistant cell lines, with IC(50) values in the nanomolar range. An initial investigation into the mechanism of cell death induced by this family of silver(I) complexes was carried out. Cell death was shown to result from the activation of apoptosis without involvement of primary necrosis. In HL60 cells, silver-NHCs induce depolarization of the mitochondrial membrane potential (ΔΨ(m)) and likely allow the release of mitochondrial proteins to elicit early apoptosis. This effect is not related to the overproduction of reactive oxygen species (ROS). In addition, apoptosis is not associated with the activation of caspase-3, but is triggered by the translocation of apoptosis-inducing factor (AIF) and caspase-12 from mitochondria and the endoplasmic reticulum, respectively, into the nucleus to promote DNA fragmentation and ultimately cell death. No modification in cell-cycle distribution was observed, indicating that silver-NHCs are not genotoxic. Finally, the use of a fluorescent complex showed that silver-NHCs target mitochondria. Altogether, these results demonstrate that silver-NHCs induce cancer cell death independent of the caspase cascade via the mitochondrial AIF pathway.

New aldehyde and vinylsulfone proteasome inhibitors for targeted melanoma therapy.

The proteasome is a promising target in cancer therapy. However, it is ubiquitous and its inhibitors cause side effects. To target melanoma cells we synthesized new peptide aldehyde and vinylsulfone inhibitors of the proteasome conjugated to the melanin-targeting ligand (MTL) derived from radiotracer [(123)I]-N-(2-diethylaminoethyl)benzamide ([(123)I]BZA) or [(125)I]-N-(4-dipropylaminobutyl)-4-iodobenzamide ([(125)I]BZ18). Influence on the cytotoxicity of the benzamide alkyl side chain length and the composition of the amino acid sequence was assessed. Among the conjugates evaluated, compound 16 and 22 presented the highest cytotoxicity (IC(50), 0.71 and 0.64 µM respectively), which persisted in the presence of an MTL derived from N-(dialkylaminoalkylenyl)benzamide residue.

Metal-NHC complexes: a survey of anti-cancer properties.

New weapons to fight cancer are constantly needed. Among chemotherapeutics, anti-cancer metal-drugs have enjoyed a long and successful history since the discovery of the benchmark cisplatin. Advances in metal-drug discovery have motivated chemists to build plethora of complex structures. Among them, a novel area is emerging. This article presents a survey of the metal-N-Heterocyclic Carbenes (Ag(I), Au(I), Pd(II) and Cu(I)-NHCs) as potential anti-cancer agents. Most of the metal-NHCs considered display higher cytotoxicities than the reference metallo-drug cisplatin. Some of them are even selective for particular cell lines. Their mechanisms of action at the cellular level are further discussed, showing that the nature of the metal is of great importance. All these promising results demonstrate that this approach deserves more attention and work.

Aging impact on biochemical activities and gene expression of Drosophila melanogaster mitochondria.

The consequences of aging are characterized by a decline in the main cellular functions, including those of the mitochondria. Although these consequences have been much studied, efforts have often focused solely on a few parameters used to assess the "state" of mitochondrial function during aging. We performed comparative measurements of several parameters in young (a few days) and old (8 and 12 weeks) adult male Drosophila melanogaster: respiratory complex activities, mitochondrial respiration, ATP synthesis, lipid composition of the inner membrane, concentrations of respiratory complex subunits, expression of genes (nuclear and mitochondrial) coding for mitochondrial proteins. Our results show that, in the mitochondria of "old" flies, the activities of three respiratory complexes (I, III, IV) are greatly diminished, ATP synthesis is decreased, and the lipid composition of the inner membrane (fatty acids, cardiolipin) is modified. However, the respiration rate and subunit concentrations measured by Western blot are unaffected. Although cellular mitochondrial DNA (mtDNA) content remains constant, there is a decrease in concentrations of nuclear and mitochondrial transcripts apparently coordinated. The expression of nuclear genes encoding the transcription factors TFAM, TFB1, TFB2, and DmTTF, which are essential for the maintenance and expression of mtDNA are also decreased. The decrease in nuclear and mitochondrial transcript concentrations may be one of the principal effects of aging on mitochondria, and could explain observed decreases in mitochondrial efficiency.

Preliminary studies of new proteasome inhibitors in the tumor targeting approach: synthesis and in vitro cytotoxicity.

The proteasome is a multicatalytic protease that plays a critical role in the cell. The control of proteasomes could, thus, provide a weapon for the treatment of cancer. Therefore, we have synthesized six new peptide aldehyde inhibitors of the proteasome linked to the N-(2-diethylaminoethyl)benzamide (BZA-CO) structure, in order to target the cytotoxic activity to malignant melanoma cells. Biological studies demonstrated the influence of length and composition of the amino acid chain on the cytotoxicity of our compounds. Among them, compound 19 presents the highest cytotoxicity (IC50 = 0.64 +/- 0.07 micromol): this cytotoxicity was maintained in the presence of BZA-CO but decreased 8-fold compared to the control MG132. Fluorescence activated cell sorter (FACS) and cytotoxic activity analysis demonstrated the selectivity of compound 19 for melanoma cells. Finally, western blottings of ubiquitinated proteins in IPC227F cells as well as proteasome assays confirmed that the cytotoxicity was linked to an inhibition of the proteasome activity.

Substrate affinity and substrate specificity of proteasomes with RNase activity.

We have partially reconstituted 20S proteasome/RNA complexes using oligonucleotides corresponding to ARE (adenosine- and uridine-rich element) (AUUUA)4 and HIV-TAR (human immunodeficiency virus-Tat transactivation response element), a stem-loop structure in the 5' UTR (untranslated region) of HIV-mRNAs. We demonstrate that these RNAs which associate with proteasomes are degraded by proteasomal endonuclease activity. The formation of these 20S proteasome/RNA substrate complexes is rather specific since 20S proteasomes do not interfere with truncated TAR that is not cleaved by proteasomal endonuclease. In addition, affinity of proteasomes for (AUUUA)4 is much stronger as it is for HIV-TAR. These results provide further arguments for our hypothesis that proteasomes could be involved in the destabilisation of cytokines mRNAs containing AUUUA sequences as well as viral mRNAs.