Role of Tetraspanin Co-029/TSPAN8 in the metastatic process in colon carcinoma ; Rôle de la Tétraspanine Co-029/TSPAN8 dans le processus métastatiquedans le cancer du côlon
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Medientyp:
E-Book
Titel:
Role of Tetraspanin Co-029/TSPAN8 in the metastatic process in colon carcinoma ; Rôle de la Tétraspanine Co-029/TSPAN8 dans le processus métastatiquedans le cancer du côlon
Erschienen:
[Erscheinungsort nicht ermittelbar]: HAL CCSD, 2016
Sprache:
Französisch
Entstehung:
Hochschulschrift:
Dissertation, HAL CCSD, 2016
Anmerkungen:
Beschreibung:
This work deals with the tetraspanin Co-029/Tspan8 and its role in tumor progression in colon cancer. Tetraspanins are a family of glycoproteins that have the property to associate directly with other membrane proteins to form primary complexes. These primary complexes then assemble into secondary order complexes realizing a membrane compartmentalization, called Tetraspanin Web " or Tetraspanins Enriched Microdomains. Numerous clinical and experimental studies have established a correlation between the expression level of certain tetraspanins and tumor progression, including metastasis.The objective of this work was to advance the understanding of the mechanism by which the tetraspanin Co-029/Tspan8 can modulate the action of other surface molecules such as receptors for growth factors or adhesion molecules on cell migration, required for invasion and metastasis. We use as cellular tools, lines expressing little or no Co-029/Tspan8 and the same transduced cell lines strongly expressing this tetraspanin. We have identified several partners for Co-029/Tspan8 by co-immunoprecipitation, cross-linking and mass spectrometry (MS), particularly EGFR, CD44 and ECE1.EGFR expression in cells inhibits cell migration only when Co-029/Tspan8 is expressed, which was demonstrated by the inhibition of expression by RNA interference or the use of EGFR inhibitors such as AG-1478 or cetuximab. This effect is reversed either by dual inhibition of EGFR and Co-029/Tspan8 or by co-treatment with anti-Co029 antibody. We have observed, on the one hand a marked increase in the association of EGFR with tetraspanins complexes in the presence of Co-029/Tspan8 and, secondly an increase in the phosphorylation of EGFR (pEGFR) suggesting a mechanism linked to signaling of this receptor.We also observed that the CD44 effect on migration of isolated cells is dependent on Co-029/Tspan8. As many types of tumors and their metastases express high levels of CD44 variants such as gastrointestinal cancer or breast cancer, we studied CD44 isoforms associated with the tetraspanin Co-029/Tspan8. We found the peptides variable exons v8-v10 of CD44 by immunoprecipitation of CD44 in our cellular model expressing Co-029/Tspan8 after mass spectrometry analysis. CD44 v8-v10 corresponds to products of the last 3 exons of the variable region of CD44. On the other hand, to investigate whether the effect of CD44 could be mediated by interaction with EGFR, we measured the level of pEGFR in cells treated by RNA interference targeting CD44. We observed that a reduction in CD44 expression was accompanied by a 50% reduction of pEGFR specifically in cells expressing Co-029/Tspan8.Finally, the analysis of tetraspanin complexes by mass spectrometry allowed us to find a new partner of Co-029/Tspan8, the type 1 endothelin-1 converting enzyme (ECE1). It is a membrane enzyme of the family of Zn dependent metallopeptidases which generates the active form of endothelin. It is expressed in various types of cancer and is associated with an invasive phenotype. Its presence in the tetraspanin complexes depends on the presence of Co-029/Tspan8 and this association increases its cleavage activity of Big-endothelin, the endothelin precursor. We investigated the functional relationship between Co-029/Tspan8 and ECE1 in normal digestive tissues by comparing wild-type mice and mice in which we inactivated the Co-029/Tspan8 gene.