RESUMO
Expression of the tetraspanin CD151 is frequently upregulated in epithelial malignancies and correlates with poor prognosis. Here, we report that CD151 is involved in regulation of the expression of fibroblast growth factor receptor 2 (FGFR2). Depletion of CD151 in breast cancer cells resulted in an increased level of FGFR2. Accordingly, an inverse correlation between CD151 and FGFR2 was observed in breast cancer tissues. CD151-dependent regulation of the FGFR2 expression relies on post-transcriptional mechanisms involving HuR (also known as ELAVL1), a multifunctional RNA-binding protein, and the assembly of processing bodies (P-bodies). Depletion of CD151 correlated with inhibition of PKC, a well-established downstream target of CD151. Accordingly, the levels of dialcylglycerol species were decreased in CD151-negative cells, and inhibition of PKC resulted in the increased expression of FGFR2. Whereas expression of FGFR2 itself did not correlate with any of the clinicopathological data, we found that FGFR2-/CD151+ patients were more likely to have developed lymph node metastasis. Conversely, FGFR2-/CD151- patients demonstrated better overall survival. These results illustrate functional interdependency between CD151 complexes and FGFR2, and suggest a previously unsuspected role of CD151 in breast tumorigenesis.
Assuntos
Neoplasias da Mama/metabolismo , Proteína Quinase C/metabolismo , Receptor Tipo 2 de Fator de Crescimento de Fibroblastos/biossíntese , Tetraspanina 24/metabolismo , Neoplasias da Mama/genética , Neoplasias da Mama/patologia , Carcinogênese , Linhagem Celular Tumoral , Feminino , Humanos , Células MCF-7 , Receptor Tipo 2 de Fator de Crescimento de Fibroblastos/genética , Transdução de Sinais , Tetraspanina 24/biossíntese , Tetraspanina 24/genética , Transcrição GênicaRESUMO
The Cancer Stem Cells (CSCs) hypothesis postulates that a minute subpopulation of cells is accountable for cancer initiation and progression. Unlike the stochastic and clonal evolution models, the CSC theory proposes that tumours are hierarchical and only the rare subset of cells at the top of the 'stemness hierarchy tree' are adequately 'equipped' biologically to initiate and drive tumourigenesis. CSCs have been implicated in various solid malignancies including prostate cancer (PCa), where their existence seems to provide an explanation for the failure of tumour eradicating therapies. As CSCs are thought to share many properties with normal stem cells, understanding normal stem cells should shed light on the pathomechanisms of cancer and, importantly, on potential therapeutic interventions. The purpose of this paper is to review the existing data on CSCs in PCa, their putative phenotypic markers, potential role in tumour biology and relevance to therapy.