RESUMO
A gene signature specific for intestinal stem cells (ISCs) has recently been shown to predict relapse in colorectal cancer (CRC) but the tumorigenic role of individual signature genes remains poorly defined. A prominent ISC-signature gene is the cancer stem cell marker CD44, which encodes various splice variants comprising a diverse repertoire of adhesion and signaling molecules. Using Lgr5 as ISC marker, we have fluorescence-activated cell sorting-purified ISCs to define their CD44 repertoire. ISCs display a specific set of CD44 variant isoforms (CD44v), but remarkably lack the CD44 standard (CD44s) isoform. These CD44v also stand-out in transformed human ISCs isolated from microadenomas of familial adenomatous polyposis patients. By employing knock-in mice expressing either CD44v4-10 or CD44s, we demonstrate that the CD44v isoform, but not CD44s, promotes adenoma initiation in Apc(Min/+)mice. Our data identify CD44v as component of the ISCs program critical for tumor initiation, and as potential treatment target in CRC.
Assuntos
Polipose Adenomatosa do Colo/genética , Transformação Celular Neoplásica/genética , Receptores de Hialuronatos/genética , Receptores de Hialuronatos/metabolismo , Neoplasias Intestinais/metabolismo , Animais , Citometria de Fluxo , Perfilação da Expressão Gênica , Técnicas de Introdução de Genes , Camundongos , Camundongos Transgênicos , Células-Tronco Neoplásicas/citologia , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Receptores Acoplados a Proteínas G/genética , Células Tumorais Cultivadas , Via de Sinalização Wnt/genéticaRESUMO
The gene coding for xylose isomerase from the thermophilic bacterium Fervidobacterium gondwanense was cloned and overexpressed in Escherichia coli. The produced xylose isomerase (XylA), which closely resembles counterparts from Thermotoga maritima and T. neapolitana, was purified and characterized. It is optimally active at 70 degrees C, pH 7.3, with a specific activity of 15.0 U/mg for the interconversion of glucose to fructose. When compared with T. maritima XylA at 85 degrees C, a higher catalytic efficiency was observed. Divalent metal ions Co2+ and Mg2+ were found to enhance the thermostability.
