AND-34/BCAR3, a GDP exchange factor whose overexpression confers antiestrogen resistance, activates Rac, PAK1, and the cyclin D1 promoter.
AND-34 is a murine protein that binds by a cdc25-like GDP exchange factor domain to the focal adhesion docking protein p130Cas. Overexpression of either of the human homologues of AND-34 and p130Cas, BCAR3 and BCAR1, respectively, has been reported to induce resistance to antiestrogens in breast cancer cell lines. Here we show that overexpression of AND-34 leads to activation of the Rho family GTPases Cdc42 and Rac. Consistent with these findings, BCAR3 overexpression induced alterations in F-actin distribution and augmented both autophosphorylation and kinase activity of the Cdc42/Rac-responsive serine/threonine kinase PAK1. p130Cas-associated BCAR3 protein was detected in the estrogen-independent breast cancer cell line 578-T, but not in estrogen-dependent MCF7 or ZR-75-1 cells. Stable ZR-75-1 transfectants overexpressing BCAR3, but not vector-only transfectants, grew in the presence of the pure antiestrogen ICI 182,780. Stable transfection with RacV12, a constitutively active form of Rac1, also induced antiestrogen resistance in ZR-75-1 cells. Transient transfection of BCAR3 in estrogen-dependent MCF7 cells induced activation of luciferase constructs containing the proximal 1745 or 163 bp but not 66 bp of the cyclin D1 promoter. Such cyclin D1 promoter activation was inhibited by dominant negative forms of Rac1 and PAK1. Overexpression of the PAK1 autoinhibitory domain (residues 83-149) but not an inactive PAK1 autoinhibitory domain point mutant (L107F) also blocked BCAR3-mediated cyclin D1 activation. These studies suggest that AND-34/BCAR3 induces antiestrogen resistance in breast cancer cell lines by a Rac1- and PAK1-dependent pathway.
Department of Medicine, Boston University School of Medicine, Boston, Massachusetts 02118, USA.
Dongpo
D
Cai
Anita
A
Iyer
Kyriacos N
KN
Felekkis
Richard I
RI
Near
Zhijun
Z
Luo
Jonathan
J
Chernoff
Chris
C
Albanese
Richard G
RG
Pestell
Adam
A
Lerner
D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000818:Animals; D001943:Breast Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism; D002352:Carrier Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D045744:Cell Line, Tumor; D019938:Cyclin D1 / Q000235:genetics*; D004789:Enzyme Activation; D004958:Estradiol / Q000031:analogs & derivatives* / Q000494:pharmacology*; D020847:Estrogen Receptor Modulators / Q000494:pharmacology*; D000077267:Fulvestrant; D020662:Guanine Nucleotide Exchange Factors; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D041681:NIH 3T3 Cells; D009376:Neoplasms, Hormone-Dependent / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic; D014176:Protein Biosynthesis; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011506:Proteins / Q000235:genetics / Q000502:physiology*; D011817:Rabbits; D014162:Transfection; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism; D054462:p21-Activated Kinases; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; C118588:BCAR3 protein, human; C120867:Bcar3 protein, mouse; D002352:Carrier Proteins; D020847:Estrogen Receptor Modulators; D020662:Guanine Nucleotide Exchange Factors; D011506:Proteins; D019938:Cyclin D1; D000077267:Fulvestrant; D004958:Estradiol; C515903:PAK1 protein, human; C515905:Pak1 protein, mouse; D017346:Protein Serine-Threonine Kinases; D054462:p21-Activated Kinases; D020764:cdc42 GTP-Binding Protein; D020830:rac1 GTP-Binding Protein