Persistent activation of stat3 signaling induces survivin gene expression and confers resistance to apoptosis in human breast cancer cells.
OBJECTIVE
Signal transducer and activator of transcription 3 (Stat3) protein is persistently activated in breast cancer and promotes tumor cell survival. To gain a better understanding of the role of constitutive Stat3 signaling in breast cancer progression, we evaluated the expression profile of potential Stat3-regulated genes that may confer resistance to apoptosis.


METHODS
Stat3 signaling was blocked with antisense oligonucleotides in human MDA-MB-435s breast cancer cells and Affymetrix GeneChip microarray analysis was done. The candidate Stat3 target gene Survivin was further evaluated in molecular assays using cultured breast cancer cells and immunohistochemistry of breast tumor specimens.


RESULTS
Survivin, a member of the inhibitor of apoptosis protein family, was identified as a potential Stat3-regulated gene by microarray analysis. This was confirmed in Survivin gene promoter studies and chromatin immunoprecipitation assays showing that Stat3 directly binds to and regulates the Survivin promoter. Furthermore, direct inhibition of Stat3 signaling blocked the expression of Survivin protein and induced apoptosis in breast cancer cells. Direct inhibition of Survivin expression also induced apoptosis. Increased Survivin protein expression correlates significantly (P = 0.001) with elevated Stat3 activity in primary breast tumor specimens from high-risk patients who were resistant to chemotherapy treatment.


CONCLUSIONS
We identify Survivin as a direct downstream target gene of Stat3 in human breast cancer cells that is critical for their survival in culture. Our findings suggest that activated Stat3 signaling contributes to breast cancer progression and resistance to chemotherapy by, at least in part, inducing expression of the antiapoptotic protein, Survivin.
Gritsko
Tanya
T
Molecular Oncology, H. Lee Moffitt Cancer Center and Research Institute Department of Interdisciplinary Oncology, University of South Florida College of Medicine, Tampa, Florida, USA.
Williams
Ann
A
Turkson
James
J
Kaneko
Satoshi
S
Bowman
Tammy
T
Huang
Mei
M
Nam
Sangkil
S
Eweis
Ibrahim
I
Diaz
Nils
N
Sullivan
Daniel
D
Yoder
Sean
S
Enkemann
Steve
S
Eschrich
Steven
S
Lee
Ji-Hyun
JH
Beam
Craig A
CA
Cheng
Jin
J
Minton
Susan
S
Muro-Cacho
Carlos A
CA
Jove
Richard
R
D017209:Apoptosis / Q000502:physiology*; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D024202:Electrophoretic Mobility Shift Assay; D004789:Enzyme Activation / Q000502:physiology; D005260:Female; D015870:Gene Expression; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D051034:Inhibitor of Apoptosis Proteins; D008869:Microtubule-Associated Proteins / Q000096:biosynthesis* / Q000235:genetics; D009363:Neoplasm Proteins / Q000096:biosynthesis* / Q000235:genetics; D020411:Oligonucleotide Array Sequence Analysis; D011401:Promoter Regions, Genetic; D050796:STAT3 Transcription Factor / Q000378:metabolism*; D000077022:Survivin
C107489:BIRC5 protein, human; D051034:Inhibitor of Apoptosis Proteins; D008869:Microtubule-Associated Proteins; D009363:Neoplasm Proteins; D050796:STAT3 Transcription Factor; D000077022:Survivin