[Expression of HSP70 and P-glycoprotein (P-gp) in human hepatocarcinoma HepG2 cells induced by heat shock and inhibiting effect of quercetin on them].
OBJECTIVE
Heat shock protein 70 (HSP70) has been thought to inhibit apoptosis and reduce the effectiveness of hyperthermal therapy and chemotherapy on cancer. However, the relationship between HSP70 and the drug resistance to chemotherapy has not been definited. P-glycoprotein (P-gp) was a kind of protein that could decrease the effectiveness of chemotherapy. In order to explore the relationship between HSP70 and P-gp, the human hepatocarcinoma line HepG2 cells was induced by heat shock in vitro, and the inhibiting effect of quercetin on them was observed at the same time to seek the method increasing the effectiveness of hyperthermal therapy on hepatocarcinoma.


METHODS
HepG2 cells were bathed in water at 42 degrees C stably for 90 minutes. The expression of HSP70 and P-gp were detected at 0, 2, 4, 8, 12, and 24 hours after 42 degrees C heat shock using immunocytochemistry and flow cytometry (FCM). Furthermore, at 4 hours later after heat shock, they were also detected in HepG2 cells which had been pretreated by quercetin in different concentrations within an hour before 42 degrees C heat shock.


RESULTS
(1) Immunocytochemistry showed that HSP70 overexpressed in the cells and "moved" from cytoplasm to nucleus and nucleolus after heat shock. The percentage of HSP70 positive cells came to the climax (11.47%) at 4th hour and increased about 2 folds compared with that of the control group (6.64%) (P< 0.01). At the 24th hour after heat shock, it declined to a low level. The percentage of cells with P-gp positive went up following HSP70 after heat shock. It came to the climax(96.31%) at the 12th hour. And it increased about 3 folds compared with that of the control group(33.95%) (P< 0.01). (2) The overexpression of HSP70 and P-gp induced by heat shock could be inhibited effectively by quercetin in a dose-dependent manner, especially by quercetin at the concentrations of 100- 200 micromol/L(P< 0.01).


CONCLUSIONS
(1) The overexpression of HSP70 and P-gp in HepG2 cells can be induced by heat shock and P-gp maybe has a correlation with HSP70. (2) The overexpression of HSP70 and P-gp in HepG2 cells induced by heat shock can be inhibited by quercetin.
Tang
Wu-Bing
WB
Cancer Center, People's Hospital of Nanhai, Foshan City, Foshan, Guangdong, 528200, PR China. tangwbing@163.com
Ma
Pei-Qiu
PQ
Ni
Hong
H
Zeng
Wen-Ting
WT
Zhu
Ke-Lun
KL
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000032:analysis / Q000096:biosynthesis*; D006528:Carcinoma, Hepatocellular / Q000378:metabolism*; D045744:Cell Line, Tumor; D018840:HSP70 Heat-Shock Proteins / Q000032:analysis / Q000096:biosynthesis*; D018869:Heat-Shock Response; D006801:Humans; D007150:Immunohistochemistry; D008113:Liver Neoplasms / Q000378:metabolism*; D011794:Quercetin / Q000494:pharmacology*
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D018840:HSP70 Heat-Shock Proteins; D011794:Quercetin