KCl depolarization increases HIF-1 transcriptional activity via the calcium-independent pathway in SGC7901 gastric cancer cells.
BACKGROUND
Hypoxia-inducible factor 1alpha (HIF-1alpha) has been reported to be expressed aberrantly in gastric cancer cells. Stability and transactivation of HIF-1 were associated with the change of intracellular calcium. We hypothesized that KCl depolarization may modulate HIF-1 activity in gastric cancer cells through calcium involvement.


METHODS
HIF-1alpha expression and its transcriptional activity were determined in SGC7901 gastric cancer cells treated with KCl and/or CoCl2 under normoxia. KCl induced change in the intracellular free calcium concentration and its effect on HIF-1 activity was investigated subsequently.


RESULTS
Exposure of SGC7901 cells to KCl (50 mM) could induce HIF-1alpha expression and its nucleus accumulation under normoxic conditions, reaching the peak at 8 and 2 h, respectively. KCl could also induce transactivation of the HIF-1 reporter gene and its target gene VEGF secretion at 8 h. Further experiments confirmed that depolarization of SGC7901 cells with KCl caused an increase in intracellular free calcium concentration. Chelation of intracellular calcium by BAPTA [1,2-bis (2-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid] induced HIF-1alpha accumulation and HIF-1 activity. However, elevation of cytosolic calcium level by ionomycin, a calcium ionophore, failed to induce HIF-1 transcriptional activity.


CONCLUSIONS
KCl depolarization would act through the calcium-independent pathway leading to enhanced HIF-1 transcriptional activity in gastric cancer cells.
Lan
Mei
M
State Key Laboratory of Cancer Biology and Institute of Digestive Diseases, Xijing Hospital, Fourth Military Medical University, Xi'an, China.
Shi
Yongquan
Y
Sun
Li
L
Liu
Lili
L
Guo
Xueyan
X
Lu
Yuanyuan
Y
Wang
Jun
J
Liang
Jie
J
Fan
Daiming
D
D045744:Cell Line, Tumor; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D017930:Genes, Reporter; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000502:physiology*; D015759:Ionomycin / Q000494:pharmacology; D008156:Luciferases / Q000235:genetics; D011189:Potassium Chloride / Q000494:pharmacology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013274:Stomach Neoplasms / Q000235:genetics* / Q000473:pathology; D014158:Transcription, Genetic / Q000187:drug effects*; D014162:Transfection
C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D004533:Egtazic Acid; D015759:Ionomycin; D011189:Potassium Chloride; D008156:Luciferases; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid