Down-regulation of 3-phosphoinositide-dependent protein kinase-1 levels inhibits migration and experimental metastasis of human breast cancer cells.
High expression of 3-phosphoinositide-dependent protein kinase-1 (PDK1) has been detected in various invasive cancers. In the current study, we investigated its role in cancer cell migration and experimental metastasis. Down-regulation of PDK1 expression by small interference RNA markedly inhibited spontaneous migration and epidermal growth factor (EGF)-induced chemotaxis of human breast cancer cells. The defects were rescued by expressing wild-type PDK1. PDK1-depleted cells showed impaired EGF-induced actin polymerization and adhesion, probably due to a decrease in phosphorylation of LIM kinase/cofilin and integrin beta1. Confocal microscopy revealed that EGF induced cotranslocation of PDK1 with Akt and protein kinase Czeta (PKCzeta), regulators of LIM kinase, and integrin beta1. Furthermore, PDK1 depletion dampened EGF-induced phosphorylation and translocation of Akt and PKCzeta, suggesting that Akt and PKCzeta functioned downstream of PDK1 in the chemotactic signaling pathway. In severe combined immunodeficiency mice, PDK1-depleted human breast cancer cells formed more slowly growing tumors and were defective in extravasation to mouse lungs after i.v. injection. Our results indicate that PDK1 plays an important role in regulating the malignant behavior of breast cancer cells, including their motility, through activation of Akt and PKCzeta. Thus, PDK1, which increases its expression in cancer cells, can be used as a target for the development of novel therapies.
Liu
Ying
Y
Department of Chemical Biology, Peking University, Beijing, China.
Wang
Jingna
J
Wu
Min
M
Wan
Wuzhou
W
Sun
Ronghua
R
Yang
De
D
Sun
Xiangjun
X
Ma
Dalong
D
Ying
Guoguang
G
Zhang
Ning
N
D064413:3-Phosphoinositide-Dependent Protein Kinases; D000199:Actins / Q000378:metabolism; D000818:Animals; D001943:Breast Neoplasms / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D002448:Cell Adhesion / Q000235:genetics; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000502:physiology*; D002633:Chemotaxis / Q000187:drug effects / Q000502:physiology; D015536:Down-Regulation; D004815:Epidermal Growth Factor / Q000494:pharmacology; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007150:Immunohistochemistry; D008175:Lung Neoplasms / Q000556:secondary; D051379:Mice; D016513:Mice, SCID; D008856:Microscopy, Fluorescence; D009361:Neoplasm Invasiveness; D009362:Neoplasm Metastasis; D051745:Protein Kinase C-delta / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000096:biosynthesis* / Q000235:genetics; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism
D000199:Actins; D034741:RNA, Small Interfering; D004815:Epidermal Growth Factor; D064413:3-Phosphoinositide-Dependent Protein Kinases; C494921:AKT2 protein, human; C578562:PDPK1 protein, human; C578564:Pdpk1 protein, mouse; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D051745:Protein Kinase C-delta