PURPOSE: del(17p), del(11q), and associated p53 dysfunction predict for short survival and chemoresistance in B-cell chronic lymphocytic leukemia (CLL). DNA-dependent protein kinase (DNA-PK) is activated by DNA damage and mediates DNA double-strand break repair. We hypothesized that inhibiting DNA-PK would sensitize CLL cells to drug-induced DNA damage and that this approach could increase the therapeutic index of agents used to treat CLL. EXPERIMENTAL DESIGN: Fifty-four CLL cases were characterized for poor prognosis markers [del(17p), del(11q), CD38, and ZAP-70]. In selected cases, DNA-PK catalytic subunit (DNA-PKcs) expression and activity and p53 function were also measured. Ex vivo viability assays established sensitivity to fludarabine and chlorambucil and also tested the ability of a novel DNA-PK inhibitor (NU7441) to sensitize CLL cells to these drugs. The effects of NU7441 on fludarabine-induced DNA damage repair were also assessed (Comet assays and detection of gammaH2AX). RESULTS: DNA-PKcs levels correlated with DNA-PK activity and varied 50-fold between cases but were consistently higher in del(17p) (P = 0.01) and del(11q) cases. NU7441 sensitized CLL cells to chlorambucil and fludarabine, including cases with del(17p), del(11q), p53 dysfunction, or high levels of DNA-PKcs. NU7441 increased fludarabine-induced double-strand breaks and abrogated drug-induced autophosphorylation of DNA-PKcs at Ser2056. High DNA-PK levels predicted for reduced treatment-free interval. CONCLUSIONS: These data validate the concept of targeting DNA-PKcs in poor risk CLL, and demonstrate a mechanistic rationale for use of a DNA-PK inhibitor. The novel observation that DNA-PKcs is overexpressed in del(17p) and del(11q) cases indicates that DNA-PK may contribute to disease progression in CLL.
PURPOSE: del(17p), del(11q), and associated p53 dysfunction predict for short survival and chemoresistance in B-cell chronic lymphocytic leukemia (CLL). DNA-dependent protein kinase (DNA-PK) is activated by DNA damage and mediates DNA double-strand break repair. We hypothesized that inhibiting DNA-PK would sensitize CLL cells to drug-induced DNA damage and that this approach could increase the therapeutic index of agents used to treat CLL. EXPERIMENTAL DESIGN: Fifty-four CLL cases were characterized for poor prognosis markers [del(17p), del(11q), CD38, and ZAP-70]. In selected cases, DNA-PK catalytic subunit (DNA-PKcs) expression and activity and p53 function were also measured. Ex vivo viability assays established sensitivity to fludarabine and chlorambucil and also tested the ability of a novel DNA-PK inhibitor (NU7441) to sensitize CLL cells to these drugs. The effects of NU7441 on fludarabine-induced DNA damage repair were also assessed (Comet assays and detection of gammaH2AX). RESULTS: DNA-PKcs levels correlated with DNA-PK activity and varied 50-fold between cases but were consistently higher in del(17p) (P = 0.01) and del(11q) cases. NU7441 sensitized CLL cells to chlorambucil and fludarabine, including cases with del(17p), del(11q), p53 dysfunction, or high levels of DNA-PKcs. NU7441 increased fludarabine-induced double-strand breaks and abrogated drug-induced autophosphorylation of DNA-PKcs at Ser2056. High DNA-PK levels predicted for reduced treatment-free interval. CONCLUSIONS: These data validate the concept of targeting DNA-PKcs in poor risk CLL, and demonstrate a mechanistic rationale for use of a DNA-PK inhibitor. The novel observation that DNA-PKcs is overexpressed in del(17p) and del(11q) cases indicates that DNA-PK may contribute to disease progression in CLL.
Authors: Jonathan F Goodwin; Vishal Kothari; Justin M Drake; Shuang Zhao; Emanuela Dylgjeri; Jeffry L Dean; Matthew J Schiewer; Christopher McNair; Jennifer K Jones; Alvaro Aytes; Michael S Magee; Adam E Snook; Ziqi Zhu; Robert B Den; Ruth C Birbe; Leonard G Gomella; Nicholas A Graham; Ajay A Vashisht; James A Wohlschlegel; Thomas G Graeber; R Jeffrey Karnes; Mandeep Takhar; Elai Davicioni; Scott A Tomlins; Cory Abate-Shen; Nima Sharifi; Owen N Witte; Felix Y Feng; Karen E Knudsen Journal: Cancer Cell Date: 2015-07-13 Impact factor: 31.743
Authors: David Davidson; Jeremy Grenier; Veronica Martinez-Marignac; Lilian Amrein; May Shawi; Marc Tokars; Raquel Aloyz; Lawrence Panasci Journal: Invest New Drugs Date: 2011-05-13 Impact factor: 3.850
Authors: Cindy R Timme; Barbara H Rath; John W O'Neill; Kevin Camphausen; Philip J Tofilon Journal: Mol Cancer Ther Date: 2018-03-16 Impact factor: 6.261