Pretreatment with interferon-alpha radiosensitizes Daudi cells modulating gene expression and biomarkers.
BACKGROUND
Interferon (IFN) potentiates cytotoxicity by X-ray irradiation. To elucidate the mechanism of this potentiation, the biological markers related to DNA damage and cell survival were studied.


METHODS
IFN-alpha-sensitive Daudi and its resistant cells were used. Survival after treatment was assessed by clonogenic assays. DNA breaks were studied by pulse-field gel electrophoresis (PFGE). Production of reactive oxygen metabolites was measured using flow cytometry. Messenger RNA and protein were examined by RT-PCR and immunoblot, respectively.


RESULTS
IFN-alpha treatment for 24 h before irradiation potentiated the sensitivity of Daudi cells to X-rays. This combination induced 50 kb DNA fragmentation and activated caspase-3 in Daudi cells. Pretreatment with IFN-alpha inhibited the production of reactive oxygen species by irradiation. IFN-alpha pretreatment down-regulated most of the double-strand break (DSB) repair-related mRNAs, but did not affect the repair of DSBs studied by PFGE. The induction and phosphorylation of p21(Cip1/WAF1) (p21) was prominently suppressed in cells pretreated with IFN-a.


CONCLUSIONS
Pretreatment with IFN-alpha potentiates the cytotoxic effects of X-rays. Inhibition of X-ray-induced p21 may cause the augmented sensitivity by IFN-alpha pretreatment.
Horiguchi-Yamada
Junko
J
Departments of Oncology, Institute of DNA Medicine, Jikei University School of Medicine, Minato-ku, Tokyo 105-8461, Japan.
Iwase
Satsuki
S
Kawano
Takeshi
T
Yamada
Hisashi
H
D014408:Biomarkers, Tumor / Q000096:biosynthesis* / Q000235:genetics; D002051:Burkitt Lymphoma / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000532:radiotherapy*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000096:biosynthesis / Q000378:metabolism; D045744:Cell Line, Tumor; D003131:Combined Modality Therapy; D050759:Cyclin-Dependent Kinase Inhibitor p21; D004249:DNA Damage; D004260:DNA Repair / Q000235:genetics; D004273:DNA, Neoplasm / Q000528:radiation effects; D015870:Gene Expression / Q000187:drug effects / Q000528:radiation effects; D006801:Humans; D016898:Interferon-alpha / Q000494:pharmacology*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*; D017382:Reactive Oxygen Species / Q000378:metabolism; D014965:X-Rays
D014408:Biomarkers, Tumor; C493956:CDKN1A protein, human; D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D004273:DNA, Neoplasm; D016898:Interferon-alpha; D012333:RNA, Messenger; D011838:Radiation-Sensitizing Agents; D017382:Reactive Oxygen Species; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases