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Mitoxantrone in combination with an inhibitor of DNA-dependent kinase: a potential therapy for high risk B-cell chronic lymphocytic leukaemia

Lookup NU author(s): Dr Sarah Johnson, Clark Crawford, Dr Evan Mulligan, Dr Jonathan Wallis, Dr Tryfonia Mainou-Fowler, Emeritus Professor Barbara Durkacz, Dr Elaine Willmore

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Abstract

Defects in the DNA damage response pathway [e.g. del(17p)] are associated with drug-resistant B-cell chronic lymphocytic leukaemia (CLL). We previously demonstrated that over-expression of DNA-dependent protein kinase (DNA-PK) correlates with chemo-resistance and that inhibition of DNA-PK sensitizes CLL cells to chemotherapeutics. Here, we investigated expression of DNA-PK and other proteins that impact on drug resistance, and evaluated the effects of a DNA-PK inhibitor (NU7441) on mitoxantrone-induced cytotoxicity in CLL cells. NU7441 sensitized cells from 42/49 CLL samples to mitoxantrone, with sensitization ranging from 2- to 200-fold Co-culture of CLL cells in conditioned stromal medium increased chemoresistance but did not reduce sensitization by NU7441. Mitoxantrone treatment induced H2AX foci and NU7441 increased their longevity (24 h). NU7441 prevented mitoxantrone-induced autophosphorylation of the DNA-PK catalytic subunit (DNA-PKcs) at Ser 2056, confirming that DNA-PK participates in repair of mitoxantrone-induced DNA damage. del(17p) cases were more resistant to mitoxantrone than del(13q) cases, but were resensitized (7–16 fold) by co-incubation with NU7441. Expression of DNA-PKcs, Ku80, P-glycoprotein and topoisomerase IIβ were significantly higher in del(17p) cases. PRKDC mRNA levels correlated with DNA-PKcs protein expression, which predicted shorter survival. These data confirm the potential of DNA-PK as a therapeutic target in poor prognosis CLL.


Publication metadata

Author(s): Elliott SL, Crawford C, Mulligan E, Summerfield G, Newton P, Wallis J, Mainou-Fowler T, Evans P, Bedwell C, Durkacz BW, Willmore E

Publication type: Article

Publication status: Published

Journal: British Journal of Haematology

Year: 2011

Volume: 152

Issue: 1

Pages: 61-71

Print publication date: 18/11/2010

ISSN (print): 0007-1048

ISSN (electronic): 1365-2141

Publisher: Wiley-Blackwell

URL: http://dx.doi.org/10.1111/j.1365-2141.2010.08425.x

DOI: 10.1111/j.1365-2141.2010.08425.x


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