TY - JOUR
T1 - Novel regulatory role for Kaposi's sarcoma-associated herpesvirus-encoded vFLIP in chemosensitization to bleomycin
AU - Masuda, Yuri
AU - Noguchi, Kohji
AU - Segawa, Hatsune
AU - Tanaka, Noritaka
AU - Katayama, Kazuhiro
AU - Mitsuhashi, Junko
AU - Sugimoto, Yoshikazu
N1 - Funding Information:
This work was supported by Grant-in-Aid for Scientific Research (C) from the Ministry of Education, Culture, Sports, Science and Technology, Japan (KAKENHI 20590068 and 23590134 ).
PY - 2011/11/18
Y1 - 2011/11/18
N2 - Kaposi's sarcoma-associated herpesvirus (KSHV/HHV-8) is associated with malignancy. KSHV-derived vFLIP is structurally related to cellular FLIP and binds to NEMO/IκB kinase (IKKγ) to activate NF-κB signaling. NF-κB activation is postulated to confer chemoresistance to various anticancer drugs. However, here we showed that vFLIP expression uniquely sensitized HEK293 cells to bleomycin and its derivatives. Chemosensitization to bleomycin by vFLIP accompanied accumulation of γ-H2AX and G2/M-arrest of cells, while bleomycin-induced DNA damage checkpoints, such as phosphorylation of Chk2 and foci formation of Rad51, were similarly detected in both parental and vFLIP-expressing cells, suggesting that primary DNA damage was not affected by vFLIP. Paradoxically, while NF-κB activity was little affected by bleomycin treatment, vFLIP-stimulated NF-κB activity was suppressed by it. Additionally, cAMP-response element (CRE)- and p53-dependent transcriptional reporter activity was negatively regulated by vFLIP in the presence of bleomycin. Interestingly, a negative regulatory phosphatase essential for G2 checkpoint recovery and for dephosphorylation of γ-H2AX, Wip1/PPM1D, whose gene promoter is regulated by p53, CRE and NF-κB, was selectively downregulated in vFLIP-expressing cells after bleomycin treatment. These results suggest that vFLIP-mediated transcriptional regulation such as Wip1/PPM1D repression is involved in chemosensitization to bleomycin.
AB - Kaposi's sarcoma-associated herpesvirus (KSHV/HHV-8) is associated with malignancy. KSHV-derived vFLIP is structurally related to cellular FLIP and binds to NEMO/IκB kinase (IKKγ) to activate NF-κB signaling. NF-κB activation is postulated to confer chemoresistance to various anticancer drugs. However, here we showed that vFLIP expression uniquely sensitized HEK293 cells to bleomycin and its derivatives. Chemosensitization to bleomycin by vFLIP accompanied accumulation of γ-H2AX and G2/M-arrest of cells, while bleomycin-induced DNA damage checkpoints, such as phosphorylation of Chk2 and foci formation of Rad51, were similarly detected in both parental and vFLIP-expressing cells, suggesting that primary DNA damage was not affected by vFLIP. Paradoxically, while NF-κB activity was little affected by bleomycin treatment, vFLIP-stimulated NF-κB activity was suppressed by it. Additionally, cAMP-response element (CRE)- and p53-dependent transcriptional reporter activity was negatively regulated by vFLIP in the presence of bleomycin. Interestingly, a negative regulatory phosphatase essential for G2 checkpoint recovery and for dephosphorylation of γ-H2AX, Wip1/PPM1D, whose gene promoter is regulated by p53, CRE and NF-κB, was selectively downregulated in vFLIP-expressing cells after bleomycin treatment. These results suggest that vFLIP-mediated transcriptional regulation such as Wip1/PPM1D repression is involved in chemosensitization to bleomycin.
KW - Anticancer drug
KW - Bleomycin
KW - Chemotherapy
KW - KSHV
KW - NF-κB
KW - VFLIP
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U2 - 10.1016/j.bbrc.2011.10.050
DO - 10.1016/j.bbrc.2011.10.050
M3 - Article
C2 - 22037577
AN - SCOPUS:84855886078
VL - 415
SP - 305
EP - 312
JO - Biochemical and Biophysical Research Communications
JF - Biochemical and Biophysical Research Communications
SN - 0006-291X
IS - 2
ER -