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Induction of hypoxia-inducible factor-1α inhibits drug-induced apoptosis in the human leukemic cell line HL-60.

Yook YJ, Seo YJ, Kang HJ, Ko SH, Shin HY, Lee JJ, Jeong G, Ahn HS - Korean J Hematol (2010)

Bottom Line: Leukemic cells originate from hypoxic bone marrow, which protects them from anti-cancer drugs.Flow cytometry analysis and western blots were performed to investigate apoptosis-related proteins.Unlike its previously known apoptotic effect, the expression of HIF-1α increased the survival rate of human promyelocytic leukemia HL-60 cells when these cells were exposed to anti-leukemic drugs; these effects were mediated by heat-shock protein HSP70 and the pro-apoptotic protein Bax.

View Article: PubMed Central - PubMed

Affiliation: Department of Pediatrics, Cancer Research Institute, Seoul National University College of Medicine, Seoul, Korea.

ABSTRACT

Background: Leukemic cells originate from hypoxic bone marrow, which protects them from anti-cancer drugs. Although many factors that cause drug resistance in leukemic cells have been studied, the effect of hypoxia on drug-induced apoptosis is still poorly understood.

Methods: In this study, we examined the effect of hypoxia on anti-leukemic drug resistance in leukemic cell lines treated with cobalt chloride (CoCl(2)), a hypoxia-mimetic agent. Cellular proliferation was evaluated using the methyl thiazolyl tetrazolium (MTT) assay. Flow cytometry analysis and western blots were performed to investigate apoptosis-related proteins.

Results: Unlike its previously known apoptotic effect, the expression of HIF-1α increased the survival rate of human promyelocytic leukemia HL-60 cells when these cells were exposed to anti-leukemic drugs; these effects were mediated by heat-shock protein HSP70 and the pro-apoptotic protein Bax.

Conclusion: These findings may provide new insights for understanding the mechanisms underlying hypoxia and for designing new therapeutic strategies for acute myeloid leukemia.

No MeSH data available.


Related in: MedlinePlus

The expression of HIF-1α increases the resistance of HL-60 cells to ATO. (A) HL-60 cells were cultured in the presence of the indicated doses of CoCl2 for 24 hrs. Expression of HIF-1α was then analyzed by western blotting. A β-actin antibody was used as an internal control. (B) HL-60 cells were cultured in the presence or absence of CdCl2 and/or CoCl2 for 12 hrs and with ATO for additional 48 hrs. Cell viability was analyzed by the MTT assay. The relative viable cell number was calculated as the ratio of each OD to the control OD. Results are expressed as relative viability±SEM. Two asterisks (*) represents statistical significance when the P-value is lower than 0.01.
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Figure 4: The expression of HIF-1α increases the resistance of HL-60 cells to ATO. (A) HL-60 cells were cultured in the presence of the indicated doses of CoCl2 for 24 hrs. Expression of HIF-1α was then analyzed by western blotting. A β-actin antibody was used as an internal control. (B) HL-60 cells were cultured in the presence or absence of CdCl2 and/or CoCl2 for 12 hrs and with ATO for additional 48 hrs. Cell viability was analyzed by the MTT assay. The relative viable cell number was calculated as the ratio of each OD to the control OD. Results are expressed as relative viability±SEM. Two asterisks (*) represents statistical significance when the P-value is lower than 0.01.

Mentions: As shown in Fig. 4, CoCl2 strongly increased the expression level of HIF-1α in a CoCl2-dose dependent manner (Fig. 4A) without significant cell death (data not shown). To determine if the effect of CoCl2 on decreased apoptosis was mediated by HIF-1α, we performed an inhibition assay using CdCl2, an inhibitor of HIF-1α activation [22]. CdCl2 effectively decreased the expression level of HIF-1α (Fig. 4B). While resistance of HL-60 cells was significantly increased more than 2-fold by CoCl2, treatment with CdCl2 reduced the survival rate of ATO-treated cells. These results show that the induction of HIF-1α by CoCl2 increases resistance of HL-60 cells to ATO.


Induction of hypoxia-inducible factor-1α inhibits drug-induced apoptosis in the human leukemic cell line HL-60.

Yook YJ, Seo YJ, Kang HJ, Ko SH, Shin HY, Lee JJ, Jeong G, Ahn HS - Korean J Hematol (2010)

The expression of HIF-1α increases the resistance of HL-60 cells to ATO. (A) HL-60 cells were cultured in the presence of the indicated doses of CoCl2 for 24 hrs. Expression of HIF-1α was then analyzed by western blotting. A β-actin antibody was used as an internal control. (B) HL-60 cells were cultured in the presence or absence of CdCl2 and/or CoCl2 for 12 hrs and with ATO for additional 48 hrs. Cell viability was analyzed by the MTT assay. The relative viable cell number was calculated as the ratio of each OD to the control OD. Results are expressed as relative viability±SEM. Two asterisks (*) represents statistical significance when the P-value is lower than 0.01.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2983039&req=5

Figure 4: The expression of HIF-1α increases the resistance of HL-60 cells to ATO. (A) HL-60 cells were cultured in the presence of the indicated doses of CoCl2 for 24 hrs. Expression of HIF-1α was then analyzed by western blotting. A β-actin antibody was used as an internal control. (B) HL-60 cells were cultured in the presence or absence of CdCl2 and/or CoCl2 for 12 hrs and with ATO for additional 48 hrs. Cell viability was analyzed by the MTT assay. The relative viable cell number was calculated as the ratio of each OD to the control OD. Results are expressed as relative viability±SEM. Two asterisks (*) represents statistical significance when the P-value is lower than 0.01.
Mentions: As shown in Fig. 4, CoCl2 strongly increased the expression level of HIF-1α in a CoCl2-dose dependent manner (Fig. 4A) without significant cell death (data not shown). To determine if the effect of CoCl2 on decreased apoptosis was mediated by HIF-1α, we performed an inhibition assay using CdCl2, an inhibitor of HIF-1α activation [22]. CdCl2 effectively decreased the expression level of HIF-1α (Fig. 4B). While resistance of HL-60 cells was significantly increased more than 2-fold by CoCl2, treatment with CdCl2 reduced the survival rate of ATO-treated cells. These results show that the induction of HIF-1α by CoCl2 increases resistance of HL-60 cells to ATO.

Bottom Line: Leukemic cells originate from hypoxic bone marrow, which protects them from anti-cancer drugs.Flow cytometry analysis and western blots were performed to investigate apoptosis-related proteins.Unlike its previously known apoptotic effect, the expression of HIF-1α increased the survival rate of human promyelocytic leukemia HL-60 cells when these cells were exposed to anti-leukemic drugs; these effects were mediated by heat-shock protein HSP70 and the pro-apoptotic protein Bax.

View Article: PubMed Central - PubMed

Affiliation: Department of Pediatrics, Cancer Research Institute, Seoul National University College of Medicine, Seoul, Korea.

ABSTRACT

Background: Leukemic cells originate from hypoxic bone marrow, which protects them from anti-cancer drugs. Although many factors that cause drug resistance in leukemic cells have been studied, the effect of hypoxia on drug-induced apoptosis is still poorly understood.

Methods: In this study, we examined the effect of hypoxia on anti-leukemic drug resistance in leukemic cell lines treated with cobalt chloride (CoCl(2)), a hypoxia-mimetic agent. Cellular proliferation was evaluated using the methyl thiazolyl tetrazolium (MTT) assay. Flow cytometry analysis and western blots were performed to investigate apoptosis-related proteins.

Results: Unlike its previously known apoptotic effect, the expression of HIF-1α increased the survival rate of human promyelocytic leukemia HL-60 cells when these cells were exposed to anti-leukemic drugs; these effects were mediated by heat-shock protein HSP70 and the pro-apoptotic protein Bax.

Conclusion: These findings may provide new insights for understanding the mechanisms underlying hypoxia and for designing new therapeutic strategies for acute myeloid leukemia.

No MeSH data available.


Related in: MedlinePlus