Hypoxia induced paclitaxel resistance in human ovarian cancers via hypoxia-inducible factor 1alpha.
OBJECTIVE
Chemoresistance severely restricts the anti-cancer medicines from effectively treating human ovarian cancer, which has been shown to develop and survive in the specific hypoxic environments. To understand the relationship between hypoxia and chemoresistance, we investigated the potential role of hypoxia in the pathophysiology of chemoresistance, especially focusing on hypoxia-inducible factor 1alpha (HIF-1alpha).


METHODS
The A2780 ovarian cancer cells are cultured in gradient hypoxic conditions (5% O(2), 3% O(2), and 1% O(2)), the sensitivity of the cells to paclitaxel and the cell inhibitory rate were determined by MTT assay. The expression and the transcriptional activity of HIF-1alpha were examined by western blot, Immunocytochemical staining, reverse transcription-polymerase chain reaction (RT-PCR), and the dual luciferase reporter system, respectively. The cell cycle distribution was analyzed by flow cytometry. In addition, we silence HIF-1alpha expression by performing RNA interference.


RESULTS
MTT assay demonstrates that hypoxic challenge substantially reduces the susceptibility of cells to paclitaxel at all the tested concentrations. Coincident with this is the activation of HIF-1alpha in nuclear, which displays the increased transcriptional activity and high protein expression. Hypoxic manipulation (5% O(2), approximately 1% O(2)) significantly increased the cell population at G0/G1. Interestingly, knockdown of endogenous HIF-1alpha significantly alleviates the chemoresistance and promotes G1/S transition with the increased sensitivity of A2780 cells to paclitaxel under each hypoxic condition.


CONCLUSIONS
It suggests that HIF-1alpha, stimulated by hypoxia, exerts a pivotal role in chemoresistance by G0/G1 arrest. Eliminating hypoxic conditions or silencing HIF-1alpha by siRNA might provide a potent tool to enhance paclitaxel effectiveness in treatment of human ovarian cancer.
Huang
Lei
L
Cancer Biology Center, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, 1095 Jiefang Ave., 430030, Wuhan, Hubei, People's Republic of China.
Ao
Qilin
Q
Zhang
Qinghua
Q
Yang
Xiaokui
X
Xing
Hui
H
Li
Fang
F
Chen
Gang
G
Zhou
Jianfeng
J
Wang
Shixuan
S
Xu
Gang
G
Meng
Li
L
Lu
Yunping
Y
Ma
Ding
D
D000972:Antineoplastic Agents, Phytogenic / Q000627:therapeutic use; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D002277:Carcinoma / Q000188:drug therapy* / Q000235:genetics* / Q000378:metabolism; D015687:Cell Hypoxia / Q000187:drug effects / Q000502:physiology; D049109:Cell Proliferation / Q000187:drug effects; D004353:Drug Evaluation, Preclinical; D019008:Drug Resistance, Neoplasm / Q000187:drug effects / Q000235:genetics* / Q000502:physiology; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000502:physiology; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D010051:Ovarian Neoplasms / Q000188:drug therapy* / Q000235:genetics* / Q000378:metabolism; D010101:Oxygen Consumption / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D017239:Paclitaxel / Q000008:administration & dosage / Q000627:therapeutic use*; D034741:RNA, Small Interfering / Q000008:administration & dosage / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D000972:Antineoplastic Agents, Phytogenic; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D034741:RNA, Small Interfering; D017239:Paclitaxel