RESUMO
Cancer stem cells (CSCs) are initiating cells in colorectal cancer (CRC). Colorectal tumours undergo epithelial to mesenchymal transition (EMT)-like processes at the invasive front, enabling invasion and metastasis, and recent studies have linked this process to the acquisition of stem cell-like properties. It is of fundamental importance to understand the molecular events leading to the establishment of cancer initiating cells and how these mechanisms relate to cellular transitions during tumourigenesis. We use an in vitro system to recapitulate changes in CRC cells at the invasive front (mesenchymal-like cells) and central mass (epithelial-like cells) of tumours. We show that the mesoderm inducer BRACHYURY is expressed in a subpopulation of CRC cells that resemble invasive front mesenchymal-like cells, where it acts to impose characteristics of CSCs in a fully reversible manner, suggesting reversible formation and modulation of such cells. BRACHYURY, itself regulated by the oncogene ß-catenin, influences NANOG and other 'stemness' markers including a panel of markers defining CRC-CSC whose presence has been linked to poor patient prognosis. Similar regulation of NANOG through BRACHYURY was observed in other cells lines, suggesting this might be a pathway common to cancer cells undergoing mesenchymal transition. We suggest that BRACHYURY may regulate NANOG in mesenchymal-like CRC cells to impose a 'plastic-state', allowing competence of cells to respond to signals prompting invasion or metastasis.
Assuntos
Neoplasias Colorretais/genética , Neoplasias Colorretais/patologia , Proteínas Fetais/genética , Células-Tronco Neoplásicas/fisiologia , Proteínas com Domínio T/genética , Antígeno AC133 , Antígenos CD/biossíntese , Antígenos CD/genética , Carcinoma Embrionário/genética , Carcinoma Embrionário/metabolismo , Carcinoma Embrionário/patologia , Moléculas de Adesão Celular Neuronais/biossíntese , Moléculas de Adesão Celular Neuronais/genética , Contagem de Células , Processos de Crescimento Celular/genética , Linhagem Celular Tumoral , Neoplasias Colorretais/metabolismo , Transição Epitelial-Mesenquimal , Proteínas Fetais/biossíntese , Regulação Neoplásica da Expressão Gênica , Técnicas de Silenciamento de Genes , Glicoproteínas/biossíntese , Glicoproteínas/genética , Proteínas de Homeodomínio/biossíntese , Proteínas de Homeodomínio/genética , Humanos , Receptores de Hialuronatos/biossíntese , Receptores de Hialuronatos/genética , Proteína Homeobox Nanog , Células-Tronco Neoplásicas/metabolismo , Células-Tronco Neoplásicas/patologia , Peptídeos/genética , Proteínas com Domínio T/biossíntese , beta Catenina/biossíntese , beta Catenina/genéticaRESUMO
Adenomatous polyposis coli (APC) is a multifunctional tumour suppressor protein, central to development and the mature organism. It is mutated in most cases of colorectal cancer, rendering it ineffective in mediating beta-catenin degradation. We show that localization of full-length APC in colon carcinoma and noncancer cell lines is independent of cell density. However, the location of truncated APC is a function of cell density and in high-density cells truncated APC is predominantly not nuclear. Although the distribution of truncated APC and beta-catenin is closely linked in subconfluent SW480 cells, at high cell density they are not colocalized. We postulated that in this cell line this could be due to an increase in beta-catenin bound to E-cadherin with formation of adherens junctions at high cell density. However, while in coimmunoprecipitation assays we observe an increase in binding between beta-catenin and E-cadherin and a corresponding decrease in binding between beta-catenin and APC at high cell density, we did not observe a strict colocalization of beta-catenin and E-cadherin at the membrane of all cells.