HSP90 inhibition induces cytotoxicity via down-regulation of Rad51 expression and DNA repair capacity in non-small cell lung cancer cells.
Heat shock protein 90 (HSP90) is an exciting new target in cancer therapy. Repair protein Rad51 is involved in protecting non-small cell lung cancer (NSCLC) cell lines against chemotherapeutic agent-induced cytotoxicity. This study investigated the role of Rad51 expression in HSP90 inhibitor 17-allylamino-17-demethoxygeldanamycin (17-AAG)-induced cytotoxicity in two NSCLC cell lines, A549 and H1975. The 17-AAG treatment decreased cellular Rad51 protein and mRNA levels and phosphorylated MKK1/2-ERK1/2 protein levels, and disrupted the HSP90 and Rad51 interaction. This triggered Rad51 protein degradation through the 26S proteasome pathway. The 17-AAG treatment also decreased the NSCLC cells' DNA repair capacity, which was restored by the forced expression of the Flag-Rad51 vector. Specific inhibition of Rad51 expression by siRNA further enhanced 17-AAG-induced cytotoxicity. In contrast, enhanced ERK1/2 activation by the constitutively active MKK1/2 (MKK1/2-CA) vector significantly restored the 17-AAG-reduced Rad51 protein levels and cell viability. Arachidin-1, an antioxidant stilbenoid, further decreased Rad51 expression and augmented the cytotoxic effect and growth inhibition of 17-AAG. The 17-AAG and arachidin-1-induced synergistic cytotoxic effects and decreased DNA repair capacity were abrogated in lung cancer cells with MKK1/2-CA or Flag-Rad51 expression vector transfection. In conclusion, HSP90 inhibition induces cytotoxicity by down-regulating Rad51 expression and DNA repair capacity in NSCLC cells.
Department of Internal Medicine, National Taiwan University Hospital, Hsin-Chu Branch, Taiwan.
Jen-Chung
JC
Ko
Huang-Jen
HJ
Chen
Yu-Ching
YC
Huang
Sheng-Chieh
SC
Tseng
Shao-Hsing
SH
Weng
Ting-Yu
TY
Wo
Yi-Jhen
YJ
Huang
Hsien-Chun
HC
Chiu
Min-Shao
MS
Tsai
Robin Y Y
RY
Chiou
Yun-Wei
YW
Lin
D000970:Antineoplastic Agents / Q000494:pharmacology; D016227:Benzoquinones / Q000494:pharmacology*; D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy / Q000473:pathology; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004260:DNA Repair / Q000187:drug effects; D015536:Down-Regulation / Q000187:drug effects; D004357:Drug Synergism; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors*; D006801:Humans; D047029:Lactams, Macrocyclic / Q000494:pharmacology*; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000473:pathology; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000008:administration & dosage; D051135:Rad51 Recombinase / Q000235:genetics*; D013267:Stilbenes / Q000494:pharmacology
D000970:Antineoplastic Agents; D016227:Benzoquinones; D018841:HSP90 Heat-Shock Proteins; D047029:Lactams, Macrocyclic; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D013267:Stilbenes; C520888:arachidin-1; C112765:tanespimycin; C495153:RAD51 protein, human; D051135:Rad51 Recombinase