TY - JOUR
T1 - NOTCH1 mutations associate with low CD20 level in chronic lymphocytic leukemia
T2 - Evidence for a NOTCH1 mutation-driven epigenetic dysregulation
AU - Pozzo, F.
AU - Bittolo, T.
AU - Arruga, F.
AU - Bulian, Pietro
AU - Macor, Paolo
AU - Tissino, E.
AU - Gizdic, B.
AU - Rossi, Francesca M.
AU - Bomben, Riccardo
AU - Zucchetto, Antonella
AU - Benedetti, Dania
AU - Degan, Massimo
AU - D'Arena, Giovanni
AU - Chiarenza, Annalisa
AU - Zaja, Francesco
AU - Pozzato, Gabriele
AU - Rossi, Davide
AU - Gaidano, Gianluca
AU - Del Poeta, Giovanni
AU - Deaglio, Silvia
AU - Gattei, Valter
AU - Dal Bo, Michele
PY - 2016/1/1
Y1 - 2016/1/1
N2 - In chronic lymphocytic leukemia (CLL), NOTCH1 mutations have been associated with clinical resistance to the anti-CD20 rituximab, although the mechanisms behind this peculiar behavior remain to be clarified. In a wide CLL series (n=692), we demonstrated that CLL cells from NOTCH1-mutated cases (87/692) were characterized by lower CD20 expression and lower relative lysis induced by anti-CD20 exposure in vitro. Consistently, CD20 expression by CLL cells was upregulated in vitro by γ-secretase inhibitors or NOTCH1-specific small interfering RNA and the stable transfection of a mutated (c.7541-7542delCT) NOTCH1 intracellular domain (NICD-mut) into CLL-like cells resulted in a strong downregulation of both CD20 protein and transcript. By using these NICD-mut transfectants, we investigated protein interactions of RBPJ, a transcription factor acting either as activator or repressor of NOTCH1 pathway when respectively bound to NICD or histone deacetylases (HDACs). Compared with controls, NICD-mut transfectants had RBPJ preferentially complexed to NICD and showed higher levels of HDACs interacting with the promoter of the CD20 gene. Finally, treatment with the HDAC inhibitor valproic acid upregulated CD20 in both NICD-mut transfectants and primary CLL cells. In conclusion, NOTCH1 mutations are associated with low CD20 levels in CLL and are responsible for a dysregulation of HDAC-mediated epigenetic repression of CD20 expression.
AB - In chronic lymphocytic leukemia (CLL), NOTCH1 mutations have been associated with clinical resistance to the anti-CD20 rituximab, although the mechanisms behind this peculiar behavior remain to be clarified. In a wide CLL series (n=692), we demonstrated that CLL cells from NOTCH1-mutated cases (87/692) were characterized by lower CD20 expression and lower relative lysis induced by anti-CD20 exposure in vitro. Consistently, CD20 expression by CLL cells was upregulated in vitro by γ-secretase inhibitors or NOTCH1-specific small interfering RNA and the stable transfection of a mutated (c.7541-7542delCT) NOTCH1 intracellular domain (NICD-mut) into CLL-like cells resulted in a strong downregulation of both CD20 protein and transcript. By using these NICD-mut transfectants, we investigated protein interactions of RBPJ, a transcription factor acting either as activator or repressor of NOTCH1 pathway when respectively bound to NICD or histone deacetylases (HDACs). Compared with controls, NICD-mut transfectants had RBPJ preferentially complexed to NICD and showed higher levels of HDACs interacting with the promoter of the CD20 gene. Finally, treatment with the HDAC inhibitor valproic acid upregulated CD20 in both NICD-mut transfectants and primary CLL cells. In conclusion, NOTCH1 mutations are associated with low CD20 levels in CLL and are responsible for a dysregulation of HDAC-mediated epigenetic repression of CD20 expression.
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U2 - 10.1038/leu.2015.182
DO - 10.1038/leu.2015.182
M3 - Article
SN - 0887-6924
VL - 30
SP - 182
EP - 189
JO - Leukemia
JF - Leukemia
IS - 1
ER -