Beta-parvin inhibits integrin-linked kinase signaling and is downregulated in breast cancer.
We analysed breast tumors and breast cancer cell lines for the expression of beta-parvin (ParvB), an adaptor protein that binds to the integrin-linked kinase (ILK). Quantitative RT-PCR indicated that ParvB mRNA was downregulated, by at least 60%, in four of nine breast tumors, relative to patient-matched normal mammary gland tissue. We also found that ParvB protein levels were reduced by > or =90% in five of seven advanced tumors, relative to matched normal breast tissue. Conversely, ILK protein and kinase activity levels were elevated in these tumors, suggesting that downregulation of ParvB stimulates ILK signaling. Western blot analyses indicated very low levels of ParvB protein in MDA-MB-231 and MCF7 breast cancer cells, facilitating functional studies of the effects of ParvB on ILK signaling. Expression of ParvB in MDA-MB-231 and MCF7 cells increased cell adhesion to collagen. ParvB inhibited ILK kinase activity, anchorage-independent cell growth and in vitro matrigel invasion by MDA-MB-231 cells. EGF-induced phosphorylation of two ILK targets, PKB (Ser473) and glycogen synthase kinase 3beta (Ser9), was also inhibited by ParvB. These results indicated that ParvB inhibits ILK signaling downstream of receptor tyrosine kinases. Our results suggest that loss of ParvB expression is a novel mechanism for upregulating ILK activity in tumors.
Cancer Research Program, Research Institute, Hospital for Sick Children, 555 University Avenue, Toronto, Ontario, Canada M5G 1X8.
Perry S
PS
Mongroo
Cameron N
CN
Johnstone
Izabela
I
Naruszewicz
Chungyee
C
Leung-Hagesteijn
Raphael K
RK
Sung
Leanne
L
Carnio
Anil K
AK
Rustgi
Gregory E
GE
Hannigan
D000185:Actinin / Q000378:metabolism*; D000256:Adenoviridae / Q000235:genetics; D000595:Amino Acid Sequence; D000906:Antibodies / Q000737:chemistry; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000378:metabolism* / Q000473:pathology; D002448:Cell Adhesion; D002453:Cell Cycle; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D003094:Collagen / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D004396:Coloring Agents / Q000494:pharmacology; D018076:DNA, Complementary / Q000378:metabolism; D015536:Down-Regulation; D004338:Drug Combinations; D004815:Epidermal Growth Factor / Q000378:metabolism; D017930:Genes, Reporter; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D006801:Humans; D007797:Laminin / Q000737:chemistry / Q000494:pharmacology; D008957:Models, Genetic; D008969:Molecular Sequence Data; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D011509:Proteoglycans / Q000737:chemistry / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D013778:Tetrazolium Salts / Q000494:pharmacology; D013844:Thiazoles / Q000494:pharmacology; D014162:Transfection; D020798:Two-Hybrid System Techniques; D015854:Up-Regulation; D000099200:Scaffold Protein ILK
D000185:Actinin; D000906:Antibodies; D003094:Collagen; D004396:Coloring Agents; D018076:DNA, Complementary; D004338:Drug Combinations; D004815:Epidermal Growth Factor; D038362:Glycogen Synthase Kinase 3; D000071679:Glycogen Synthase Kinase 3 beta; D007797:Laminin; D017346:Protein Serine-Threonine Kinases; D011509:Proteoglycans; D012333:RNA, Messenger; D011994:Recombinant Proteins; D013778:Tetrazolium Salts; D013844:Thiazoles; D000099200:Scaffold Protein ILK; C486591:PARVB protein, human; C059485:matrigel; C000605506:GSK3B protein, human; C022616:thiazolyl blue