Numb-like (NumbL) downregulation increases tumorigenicity, cancer stem cell-like properties and resistance to chemotherapy
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José M. García-Heredia1,2, Eva M. Verdugo Sivianes1, Antonio Lucena-Cacace1, Sonia Molina-Pinelo1,3, Amancio Carnero1
1Instituto de Biomedicina de Sevilla (IBIS), Hospital Universitario Virgen del Rocio, Universidad de Sevilla, Consejo Superior de Investigaciones Cientificas, Seville, Spain
2Department of Vegetal Biochemistry and Molecular Biology, University of Seville, Seville, Spain
3Present address: Instituto de Investigación Hospital 12 de Octubre, Madrid, Spain
Amancio Carnero, email: [email protected]
Keywords: NumbL, Notch, cancer stem cells, tumor suppressor, tumorigenicity
Received: April 22, 2016 Accepted: August 12, 2016 Published: August 23, 2016
NumbL, or Numb-like, is a close homologue of Numb, and is part of an evolutionary conserved protein family implicated in some important cellular processes. Numb is a protein involved in cell development, in cell adhesion and migration, in asymmetric cell division, and in targeting proteins for endocytosis and ubiquitination. NumbL exhibits some overlapping functions with Numb, but its role in tumorigenesis is not fully known. Here we showed that the downregulation of NumbL alone is sufficient to increase NICD nuclear translocation and induce Notch pathway activation. Furthermore, NumbL downregulation increases epithelial-mesenchymal transition (EMT) and cancer stem cell (CSC)-related gene transcripts and CSC-like phenotypes, including an increase in the CSC-like pool. These data suggest that NumbL can act independently as a tumor suppressor gene. Furthermore, an absence of NumbL induces chemoresistance in tumor cells. An analysis of human tumors indicates that NumbL is downregulated in a variable percentage of human tumors, with lower levels of this gene correlated with worse prognosis in colon, breast and lung tumors. Therefore, NumbL can act as an independent tumor suppressor inhibiting the Notch pathway and regulating the cancer stem cell pool.
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