Expression of Wnt3 activates Wnt/β-catenin pathway and promotes EMT-like phenotype in trastuzumab-resistant HER2-overexpressing breast cancer cells.
To understand the mechanisms leading to trastuzumab resistance in HER2-overexpressing breast tumors, we created trastuzumab-insensitive cell lines (SKBR3/100-8 and BT474/100-2). The cell lines maintain HER2 receptor overexpression and show increase in EGF receptor (EGFR). Upon trastuzumab treatment, SKBR3/100-8 and BT474/100-2 cell lines displayed increased growth rate and invasiveness. The trastuzumab resistance in SKBR3/100-8 and BT474/100-2 was accompanied with activation of the Wnt/β-catenin signaling pathway. Further investigation found that Wnt3 overexpression played a key role toward the development of trastuzumab resistance. The expression of Wnt3 in trastuzumab-resistant cells increased nuclear expression of β-catenin and transactivated expression of EGFR. The increased Wnt3 in the trastuzumab-resistant cells also promoted a partial EMT-like transition (epithelial-to-mesenchymal transition); increased N-cadherin, Twist, Slug; and decreased E-cadherin. Knockdown of Wnt3 by siRNA restored cytoplasmic expression of β-catenin and decreased EGFR expression in trastuzumab-resistant cells. Furthermore, the EMT markers were decreased, E-cadherin was increased, and the cell invasiveness was inhibited in response to the Wnt3 downregulation. Conversely, SKBR3 cells which had been stably transfected with full-length Wnt3 exhibited EMT-like transition. The Wnt3 transfectants, SKBR3/Wnt3-7 and SKBR3/Wnt3-9, showed a significant decrease in E-cadherin and increase in N-cadherin, Twist, and Slug. The cells were less sensitive to trastuzumab than parental SKBR3 and vector-transfected cells. In summary, our data suggest that Wnt3 overexpression activates Wnt/β-catenin signaling pathway that leads to transactivation of EGFR and promotes EMT-like transition. This could be an important mechanism leading to trastuzumab resistance in HER2-overexpressing breast cancer cells.
Division of Cancer Research and Training, Department of Medicine, Charles R. Drew University of Medicine and Science, Los Angeles, CA 90059, USA. yanyuanwu@cdrewu.edu
Yanyuan
Y
Wu
Charles
C
Ginther
Juri
J
Kim
Nicole
N
Mosher
Seyung
S
Chung
Dennis
D
Slamon
Jaydutt V
JV
Vadgama
D061067:Antibodies, Monoclonal, Humanized / Q000494:pharmacology*; D001943:Breast Neoplasms / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D015820:Cadherins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm; D066246:ErbB Receptors / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D005260:Female; D006801:Humans; D009687:Nuclear Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D027701:Organic Cation Transport Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D010641:Phenotype; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D015533:Transcriptional Activation; D000068878:Trastuzumab; D051879:Twist-Related Protein 1 / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D060449:Wnt Signaling Pathway; D060508:Wnt3 Protein / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D051176:beta Catenin / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D000099254:Organic Cation Transporter 3
D061067:Antibodies, Monoclonal, Humanized; D015820:Cadherins; D066246:ErbB Receptors; D009687:Nuclear Proteins; D027701:Organic Cation Transport Proteins; D018719:Erb-b2 Receptor Tyrosine Kinases; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors; D000068878:Trastuzumab; D051879:Twist-Related Protein 1; D060508:Wnt3 Protein; D051176:beta Catenin; D000099254:Organic Cation Transporter 3; C000604407:SNAI1 protein, human; C103173:TWIST1 protein, human; C555507:WNT3 protein, human; C512478:EGFR protein, human