RESUMEN
An understanding of signaling pathways is a basic requirement for the treatment of melanoma. Currently, kinases are at the center of melanoma therapies. According to our research, additional alternative molecules are equally important for development of melanoma. In this regard, cancer progression is, among other factors, driven by an altered adhesion via cadherins. For instance, the de-regulated expression of the adhesion molecule T-cadherin is found in various cancer types, including melanoma, and influences migration and invasion. T-cadherin is thought to affect cellular function largely through its signaling and not its adhesion properties because the molecule is anchored into the cell membrane by a glycosylphosphatidylinositol (GPI) moiety. However, detailed knowledge about the consequences of the loss of T-cadherin in melanoma is currently lacking. For this reason, we were interested in assessing which signaling pathways are initiated by T-cadherin. The tumor growth of subcutaneously injected T-cadherin-positive melanoma cells was diminished compared with T-cadherin-negative cells in nude mice. The difference in tumor volume was not due to decreased proliferation but rather due to increased apoptosis. After the expression of T-cadherin was induced, we detected V-AKT murine thymoma viral oncogene homolog (AKT) and FoxO3a hypophosphorylation accompanied by the downregulation of the antiapoptotic molecules BCL-2, BCL-x and Clusterin. Furthermore, we detected a diminished transcriptional activity of CREB and AP-1. We demonstrated that T-cadherin functions as a pro-apoptotic tumor suppressor that antagonizes AKT/CREB/AP-1/FoxO3a signaling, whereas NFκB, TCF/LEF and mTOR are not part of the T-cadherin signaling pathway. Notably, we found that the restoration of T-cadherin in melanoma cells causes sensitization to apoptosis induced by CD95/Fas antibody CH-11.
Asunto(s)
Apoptosis , Cadherinas/metabolismo , Proliferación Celular , Melanoma/patología , Proteínas Proto-Oncogénicas c-akt/metabolismo , Animales , Western Blotting , Cadherinas/antagonistas & inhibidores , Cadherinas/genética , Ensayo de Cambio de Movilidad Electroforética , Ensayo de Inmunoadsorción Enzimática , Proteína Forkhead Box O3 , Factores de Transcripción Forkhead/genética , Factores de Transcripción Forkhead/metabolismo , Humanos , Técnicas para Inmunoenzimas , Inmunoprecipitación , Masculino , Melanoma/genética , Melanoma/metabolismo , Ratones , Ratones Desnudos , Neovascularización Patológica , Fosforilación , Proteínas Proto-Oncogénicas c-akt/genética , ARN Mensajero/genética , Reacción en Cadena en Tiempo Real de la Polimerasa , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Transducción de Señal , Células Tumorales Cultivadas , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
BACKGROUND: Merkel cell carcinoma (MCC) is an aggressive KIT-positive cutaneous tumor. KIT mutations are considered to play a key role in the pathogenesis of various neoplasms, but have not been found so far in MCC. The aim of the present study was therefore to investigate the presence of KIT mutations in MCC. MATERIALS AND METHODS: The entire coding region of KIT in the MCC cell line MCC-1 was sequenced. KIT exon 10 was amplified from archival paraffin-embedded MCC specimens by PCR and sequenced. RESULTS: Exon 10 M541L KIT sequence variation, which confers increased sensitivity to KIT ligand stem cell factor, was detected in the MCC-1 cell line. Sequencing of KIT exon 10 in six archival MCC specimens revealed the wild-type sequence. CONCLUSION: The presence of the M541L KIT variation in MCC warrants further studies for its role in the pathogenesis of this tumor.