Project description:To identify potential miRNA effectors responsible for anti-tumorigenesis by targeting PLD1, we performed miRNA microarray in Wnt-relevant colon cancer cells and analyzed miRNAs that were differently expressed by inhibition of PLD1
Project description:We have sequenced miRNA libraries from human embryonic, neural and foetal mesenchymal stem cells. We report that the majority of miRNA genes encode mature isomers that vary in size by one or more bases at the 3’ and/or 5’ end of the miRNA. Northern blotting for individual miRNAs showed that the proportions of isomiRs expressed by a single miRNA gene often differ between cell and tissue types. IsomiRs were readily co-immunoprecipitated with Argonaute proteins in vivo and were active in luciferase assays, indicating that they are functional. Bioinformatics analysis predicts substantial differences in targeting between miRNAs with minor 5’ differences and in support of this we report that a 5’ isomiR-9-1 gained the ability to inhibit the expression of DNMT3B and NCAM2 but lost the ability to inhibit CDH1 in vitro. This result was confirmed by the use of isomiR-specific sponges. Our analysis of the miRGator database indicates that a small percentage of human miRNA genes express isomiRs as the dominant transcript in certain cell types and analysis of miRBase shows that 5’ isomiRs have replaced canonical miRNAs many times during evolution. This strongly indicates that isomiRs are of functional importance and have contributed to the evolution of miRNA genes
Project description:Mitogen-activated protein kinases (MEK 1/2) are central components of the RAS signaling pathway and attractive targets for cancer therapy. However, PIK3CA mutation, which commonly co-occurs with KRAS mutation, offered resistance to MEK inhibitor through activation of PI3K-AKT signaling. We identified a gene that cooperates with MEK inhibitors to forcefully treat PIK3CA mutant colon cancer cells. -catenin, a key molecule of the WNT pathway, emerged as a candidate by protein/Ab Chip array. MEK inhibitor treatment led to a decrease in -catenin in PIK3CA wild-type colon cancer cells but not in PIK3CA mutant colon cancer cells. Tumor regression was promoted by a combination of MEK inhibitor and NVP-TNS656, which targets the WNT pathway. Furthermore, combined inhibition of MEK and -catenin by NVP-TNS656 promoted tumor regression in colon cancer patient-derived xenograft (PDX) models expressing mutant PIK3CA. Taken together, we propose that inhibition of the WNT pathway, particularly -catenin, may bypass resistance to MEK inhibitor in human PIK3CA mutant colon cancer. Additionally, -catenin is a potential PD marker of MEK inhibitor resistance. In the study, we identified and evaluated biomarker for response to MEK inhibitor on colon cancer cells.
Project description:Kynureninase is a member of a large family of catalytically diverse but structurally homologous pyridoxal 5'-phosphate (PLP) dependent enzymes known as the aspartate aminotransferase superfamily or alpha-family. The Homo sapiens and other eukaryotic constitutive kynureninases preferentially catalyze the hydrolytic cleavage of 3-hydroxy-l-kynurenine to produce 3-hydroxyanthranilate and l-alanine, while l-kynurenine is the substrate of many prokaryotic inducible kynureninases. The human enzyme was cloned with an N-terminal hexahistidine tag, expressed, and purified from a bacterial expression system using Ni metal ion affinity chromatography. Kinetic characterization of the recombinant enzyme reveals classic Michaelis-Menten behavior, with a Km of 28.3 +/- 1.9 microM and a specific activity of 1.75 micromol min-1 mg-1 for 3-hydroxy-dl-kynurenine. Crystals of recombinant kynureninase that diffracted to 2.0 A were obtained, and the atomic structure of the PLP-bound holoenzyme was determined by molecular replacement using the Pseudomonas fluorescens kynureninase structure (PDB entry 1qz9) as the phasing model. A structural superposition with the P. fluorescens kynureninase revealed that these two structures resemble the "open" and "closed" conformations of aspartate aminotransferase. The comparison illustrates the dynamic nature of these proteins' small domains and reveals a role for Arg-434 similar to its role in other AAT alpha-family members. Docking of 3-hydroxy-l-kynurenine into the human kynureninase active site suggests that Asn-333 and His-102 are involved in substrate binding and molecular discrimination between inducible and constitutive kynureninase substrates.