PMID- 17289019
OWN - NLM
STAT- MEDLINE
DCOM- 20070412
LR  - 20131121
IS  - 0014-4827 (Print)
IS  - 0014-4827 (Linking)
VI  - 313
IP  - 5
DP  - 2007 Mar 10
TI  - Confluence-dependent resistance to doxorubicin in human MDA-MB-231 breast 
      carcinoma cells requires hypoxia-inducible factor-1 activity.
PG  - 867-77
AB  - Compared with tumour cells cultured as sparse monolayers, tumour cells cultured 
      as confluent monolayers exhibit high levels of resistance to anti-cancer agents. 
      This phenomenon is called confluence-dependent resistance (CDR). We determined 
      the contribution of hypoxia-inducible factor-1 (HIF-1), a key transcriptional 
      regulator of cellular adaptations to hypoxia, to the development of CDR in 
      MDA-MB-231 breast cancer cells. Clonogenic assays revealed a density-dependent 
      increase in resistance to doxorubicin. Cell density also correlated with 
      increased staining for reductively activated pimonidazole (a marker for hypoxia), 
      as well as with increased levels of the HIF-1alpha subunit and HIF 
      transcriptional activity as determined by immunocytochemistry, Western blot, and 
      luciferase reporter assays. Importantly, inhibition of HIF-1alpha expression with 
      siRNA significantly attenuated CDR. Similarly, shaking of cultures attenuated 
      CDR, pimonidazole immunostaining, HIF-1alpha accumulation, and HIF-1 
      transcriptional activity. Having established a link between HIF-1 and CDR, we 
      used HIF-1alpha and HIF-1 transcriptional activity as markers to investigate the 
      role of additional factors in the regulation of CDR. Confluence-dependent 
      increases in HIF-1alpha accumulation and HIF-1 transcriptional activity were 
      observed even in cells cultured at 0.1% O(2) as well as in sparse cultures 
      incubated with conditioned medium from confluent monolayers. Serum deprivation in 
      both sparse and confluent cultures also resulted in HIF-1alpha accumulation. 
      These results reveal that, although pericellular hypoxia may be a major 
      contributor to HIF-1 activity, changes in the levels of soluble factors may also 
      play a role. This study demonstrates that HIF-1 is required for CDR.
FAU - Fang, Yu
AU  - Fang Y
AD  - Department of Anatomy and Cell Biology, Botterell Hall Room 859, Queen's 
      University, Kingston, ON, Canada K7L 3N6.
FAU - Sullivan, Richard
AU  - Sullivan R
FAU - Graham, Charles H
AU  - Graham CH
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
DEP - 20061221
PL  - United States
TA  - Exp Cell Res
JT  - Experimental cell research
JID - 0373226
RN  - 0 (Antibiotics, Antineoplastic)
RN  - 0 (Hypoxia-Inducible Factor 1)
RN  - 80168379AG (Doxorubicin)
SB  - IM
MH  - Antibiotics, Antineoplastic/*pharmacology
MH  - Breast Neoplasms/*metabolism
MH  - Carcinoma/*metabolism
MH  - Cell Count
MH  - Cell Culture Techniques/methods
MH  - Cell Hypoxia
MH  - Cell Line, Tumor
MH  - Doxorubicin/*pharmacology
MH  - *Drug Resistance, Neoplasm
MH  - *Gene Expression Regulation, Neoplastic
MH  - Humans
MH  - Hypoxia-Inducible Factor 1/genetics/*metabolism
MH  - Transcription, Genetic
EDAT- 2007/02/10 09:00
MHDA- 2007/04/14 09:00
CRDT- 2007/02/10 09:00
PHST- 2006/10/27 00:00 [received]
PHST- 2006/12/06 00:00 [revised]
PHST- 2006/12/11 00:00 [accepted]
PHST- 2007/02/10 09:00 [pubmed]
PHST- 2007/04/14 09:00 [medline]
PHST- 2007/02/10 09:00 [entrez]
AID - S0014-4827(06)00499-X [pii]
AID - 10.1016/j.yexcr.2006.12.004 [doi]
PST - ppublish
SO  - Exp Cell Res. 2007 Mar 10;313(5):867-77. doi: 10.1016/j.yexcr.2006.12.004. Epub 
      2006 Dec 21.