Heat shock increases expression of NAD(P)H:quinone oxidoreductase (NQO1), mediator of beta-lapachone cytotoxicity, by increasing NQO1 gene activity and via Hsp70-mediated stabilisation of NQO1 protein.
NAD(P)H:quinone oxidoreductase (NQO1) mediates cell death caused by the novel anti-cancer drug beta-lapachone (beta-lap). Therefore, beta-lap sensitivity of cells is positively related to the level of cellular NQO1. Heat shock up-regulates NQO1 expression in cancer cells, thereby enhancing the clonogenic cell death caused by beta-lap. The mechanisms by which heat shock elevates NQO1 expression were investigated in the present study using human A549 lung cancer cells and human MDA-MB-231 breast cancer cells. When MDA-MB-231(NQO1+) cells stably transfected with NQO1 were heated at 42 degrees C for 1 h the expression of NQO1 and the sensitivity of the cells to beta-lap progressively increased during the 24-48 h post-heating period. Heating increased NQO1 transcription by cis-acting elements such as xenobiotic response element and antioxidant response element located in the NQO1 gene promoter region. The turnover of NQO1 protein in heated cells was much slower than in unheated cells. NQO1 and heat shock protein 70 (Hsp70) co-precipitated and co-localised in cells before and after heating, demonstrating the close association of these two proteins in the cells. These results suggest that NQO1 is stabilised by the Hsp70 molecular chaperone. It is concluded that the prolonged increase in NQO1 expression after heat shock is due to increased NQO1 transcription, and also increased Hsp70-mediated NQO1 stabilisation.
Dong
Guang-Zhi
GZ
Department of Microbiology, and Centre for Advanced Medical Education by BK21 Project, College of Medicine, Inha University, Inchon, South Korea.
Youn
Hyewon
H
Park
Moon-Taek
MT
Oh
Eun-Taex
ET
Park
Kyung Hee
KH
Song
Chang Won
CW
Choi
Eun Kyung
EK
Park
Heon Joo
HJ
D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D016923:Cell Death; D045744:Cell Line, Tumor; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D018840:HSP70 Heat-Shock Proteins / Q000502:physiology*; D018869:Heat-Shock Response; D006801:Humans; D006979:Hyperthermia, Induced; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000096:biosynthesis*; D009285:Naphthoquinones / Q000494:pharmacology*
D000972:Antineoplastic Agents, Phytogenic; D018840:HSP70 Heat-Shock Proteins; D009285:Naphthoquinones; D003609:Dactinomycin; C014638:beta-lapachone; D003513:Cycloheximide; D016660:NAD(P)H Dehydrogenase (Quinone); C447479:NQO1 protein, human