Twist transcriptionally up-regulates AKT2 in breast cancer cells leading to increased migration, invasion, and resistance to paclitaxel.
Metastasis, the cardinal feature of malignant tumors, is an important clinical variable in patient prognosis. To understand the basis for metastasis, we systematically selected for highly invasive cells from breast cancer cell lines, MCF7 and MDA-MB-453, with moderate to low invasive ability using Boyden chamber invasion assay. The four-cycle selected invasive lines, named MCF7-I4 and MDA-MB-453-I4, respectively, displayed epithelial-mesenchymal transition (EMT) and dramatically enhanced invasive ability. EMT changes were corroborated with decreased level of E-cadherin and increased vimentin, fibronectin, and beta(1) integrin. Twist, a basic helix-loop-helix transcription factor, and AKT2, a known proto-oncogene, were found to be elevated in the invasive cells compared with the parental. Ectopic expression and knockdown of Twist by short interference RNA resulted in significant increase and reduction, respectively, of AKT2 protein and mRNA expression. Twist bound to E-box elements on AKT2 promoter and enhanced its transcriptional activity. Moreover, silencing AKT2 decreased Twist-promoted migration, invasion, and paclitaxel resistance. Reintroducing AKT2 largely rescued the phenotype resulted from knockdown of Twist in I4 cells, suggesting that AKT2 is a downstream target and functional mediator of Twist. Finally, we observed a 68.8% correlation of elevated Twist and AKT2 expression in late-stage breast cancers as oppose to 13% in early-stage breast cancers. Our study identifies Twist as a positive transcriptional regulator of AKT2 expression, and Twist-AKT2 signaling is involved in promoting invasive ability and survival of breast cancer cells.
Cheng
George Z
GZ
Department of Microbiology, Mount Sinai School of Medicine, One Gustave L. Levy Place, New York, NY 10029, USA.
Chan
Joseph
J
Wang
Qi
Q
Zhang
Weizhou
W
Sun
Calvin D
CD
Wang
Lu-Hai
LH
D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology / Q000627:therapeutic use; D001943:Breast Neoplasms / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism / Q000473:pathology*; D002465:Cell Movement / Q000187:drug effects; D019008:Drug Resistance, Neoplasm / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D009361:Neoplasm Invasiveness; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D017239:Paclitaxel / Q000494:pharmacology* / Q000627:therapeutic use; D011401:Promoter Regions, Genetic; D000090063:Proto-Oncogene Mas; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000494:pharmacology; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured; D051879:Twist-Related Protein 1 / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*
D000972:Antineoplastic Agents, Phytogenic; C000715470:MAS1 protein, human; D009687:Nuclear Proteins; D000090063:Proto-Oncogene Mas; D034741:RNA, Small Interfering; C103173:TWIST1 protein, human; D051879:Twist-Related Protein 1; C494921:AKT2 protein, human; D051057:Proto-Oncogene Proteins c-akt; D017239:Paclitaxel