Suppression of Her2/neu expression through ILK inhibition is regulated by a pathway involving TWIST and YB-1.
In a previous study it was found that the therapeutic effects of QLT0267, a small molecule inhibitor of integrin-linked kinase (ILK), were influenced by Her2/neu expression. To understand how inhibition or silencing of ILK influences Her2/neu expression, Her2/neu signaling was evaluated in six Her2/neu-positive breast cancer cell lines (LCC6(Her2), MCF7(Her2), SKBR3, BT474, JIMT-1 and KPL-4). Treatment with QLT0267 engendered suppression (32-87%) of total Her2/neu protein in these cells. Suppression of Her2/neu was also observed following small interfering RNA-mediated silencing of ILK expression. Time course studies suggest that ILK inhibition or silencing caused transient decreases in P-AKT(ser473), which were not temporally related to Her2/neu downregulation. Attenuation of ILK activity or expression was, however, associated with decreases in YB-1 (Y-box binding protein-1) protein and transcript levels. YB-1 is a known transcriptional regulator of Her2/neu expression, and in this study it is demonstrated that inhibition of ILK activity using QLT0267 decreased YB-1 promoter activity by 50.6%. ILK inhibition was associated with changes in YB-1 localization, as reflected by localization of cytoplasmic YB-1 into stress granules. ILK inhibition also suppressed TWIST (a regulator of YB-1 expression) protein expression. To confirm the role of ILK on YB-1 and TWIST, cells were engineered to overexpress ILK. This was associated with a fourfold increase in the level of YB-1 in the nucleus, and a 2- and 1.5-fold increase in TWIST and Her2/neu protein levels, respectively. Taken together, these data indicate that ILK regulates the expression of Her2/neu through TWIST and YB-1, lending support to the use of ILK inhibitors in the treatment of aggressive Her2/neu-positive tumors.
Kalra
J
J
Department of Experimental Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada. jkalra@bccrc.ca
Sutherland
B W
BW
Stratford
A L
AL
Dragowska
W
W
Gelmon
K A
KA
Dedhar
S
S
Dunn
S E
SE
Bally
M B
MB
D001391:Azo Compounds / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000032:analysis / Q000502:physiology*; D066246:ErbB Receptors / Q000032:analysis; D006801:Humans; D009687:Nuclear Proteins / Q000032:analysis / Q000502:physiology*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000502:physiology; D011720:Pyrazoles / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000235:genetics; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000032:analysis / Q000037:antagonists & inhibitors*; D050796:STAT3 Transcription Factor / Q000502:physiology; D015398:Signal Transduction; D014407:Tumor Cells, Cultured; D051879:Twist-Related Protein 1 / Q000502:physiology*; D051840:Y-Box-Binding Protein 1; D000099200:Scaffold Protein ILK
D001391:Azo Compounds; D004268:DNA-Binding Proteins; D066246:ErbB Receptors; D009687:Nuclear Proteins; D017346:Protein Serine-Threonine Kinases; D011720:Pyrazoles; D034741:RNA, Small Interfering; D018719:Erb-b2 Receptor Tyrosine Kinases; D050796:STAT3 Transcription Factor; D051879:Twist-Related Protein 1; D051840:Y-Box-Binding Protein 1; D000099200:Scaffold Protein ILK; C552362:QLT 0267; C494086:STAT3 protein, human; C103173:TWIST1 protein, human; C070856:YBX1 protein, human; C508053:ERBB2 protein, human