[Advances in head and neck cancers on behalf of the French Intergroup ORL and GORTEC]. / Évolution des concepts dans les cancers des voies aérodigestives supérieures, sous l'égide de l'Intergroupe ORL (GORTEC, GETTEC, GERCOR).

Head and neck cancers are the fifth among the most common cancers in France. Two thirds of cases occur at an advanced stage. For advanced disease, progression-free survival, despite undeniable progress, remains below 50% at three years. The last 20 years have been marked by the necessity to identify situations where less intense surgery and/or radiotherapy and/or chemotherapy is possible without jeopardizing the prognosis, and situations where a therapeutic intensification is necessary and results in a gain in survival while better preserving function with less toxicity. French cooperative groups gathering radiation oncologists (GORTEC), surgeons (GETTEC) and medical oncologists or physicians involved in the management of systemic treatments in head and neck cancers (GERCOR) are now belonging to the INCa-labelled Intergroup ORL to deal with the challenges of head and neck cancers.

Regulation of the Ets-1 transcription factor by sumoylation and ubiquitinylation.

Sumoylation and ubiquitinylation reversibly regulate the activity of transcription factors through covalent attachment to lysine residues of target proteins. We examined whether the Ets-1 transcription factor is modified by sumoylation and/or ubiquitinylation. Among four potential SUMO motifs in Ets-1, we identified lysines 15 and 227 within the LK(15)YE and IK(227)QE motifs, as being the sumoylation acceptor sites. Using transfection of Ets-1 wildtype (WT) or its sumoylation deficient version (Ets-1 K15R/K227R), as well as WT or mutant proteins of the SUMO pathway, we further demonstrated that the E2 SUMO-conjugating enzyme Ubc9 and a E3 SUMO ligase, PIASy, can enhance Ets-1 sumoylation, while a SUMO protease, SENP1, can desumoylate Ets-1. We also found that Ets-1 is modified by K48-linked polyubiquitinylation independently of the sumoylation acceptor sites and is degraded through the 26S proteasome pathway, while sumoylation of Ets-1 does not affect its stability. Finally, sumoylation of Ets-1 leads to reduced transactivation and we demonstrated that previously identified critical lysine residues in Synergistic Control motifs are the sumoylation acceptor sites of Ets-1. These data show that Ets-1 can be modified by sumoylation and/or ubiquitinylation, with sumoylation repressing transcriptional activity of Ets-1 and having no clear antagonistic action on the ubiquitin-proteasome degradation pathway.

Stromelysin-1 expression is activated in vivo by Ets-1 through palindromic head-to-head Ets binding sites present in the promoter.

Regulation of the gene expression of Stromelysin-1 (matrix metalloproteinase-3), a member of the matrix metalloproteinase family, is critical for tissue homeostasis. The Stromelysin-1 promoter is known to be transactivated by Ets proteins through palindromic head-to-head Ets binding sites (EBS), an unusual configuration among metalloproteinase promoters. Patterns of increased co-expression of Stromelysin-1 and Ets-1 genes have been observed in pathological processes such as rheumatoid arthritis, glomerulonephritis and tumor invasion. In this context, we show in a synovial fibroblastic model cell line (HIG-82), which is able to co-express Stromelysin-1 and Ets-1, that the EBS palindrome is essential for the expression of Stromelysin-1. More precisely, using electrophoretic mobility shift assays, DNA affinity purification and chromatin immunoprecipitation, we demonstrate that endogenous Ets-1, but not Ets-2, is present on this palindrome. The use of a dominant-negative form of Ets-1 and the decrease of Ets-1 amount either by fumagillin, an antiangiogenic compound, or by short interfering RNA show that the activation rate of the promoter and the expression of Stromelysin-1 correlate with the level of endogenous Ets-1. Thus, it is the first demonstration, using this cellular model, that endogenously expressed Ets-1 is actually a main activator of the Stromelysin-1 promoter through its effective binding to the EBS palindrome.