Signal therapy for RAS-induced cancers in combination of AG 879 and PP1, specific inhibitors for ErbB2 and Src family kinases, that block PAK activation.
BACKGROUND
Both EGF family ligands and ErbB family receptor kinases act upstream of RAS to induce mitogenesis of normal cells, such as NIH 3T3 fibroblasts. However, oncogenically mutated RAS, such as v-Ha-RAS is constitutively activated and therefore no longer requires these ligands or receptors for its activation. Nevertheless, it up-regulates the expression of these EGF family ligands. To understand the biologic significance of RAS-induced up-regulation of these ligands in both RAS-induced PAK activation and malignant transformation, we have conducted the following studies, based on the previous observations that (1) the N-terminal SH3 domain of PIX selectively binds a Pro-rich domain of 18 amino acids of PAKs, CDC42/Rac-dependent Ser/Thr kinase family, and (2) this specific interaction is essential for both PAK activation and membrane ruffling


RESULTS
Using four distinct, cell-permeable, and highly specific inhibitors, namely WR-PAK18, which blocks the PAK-PIX interaction; AG 1478, which inhibits ErbB1 kinase activity; and AG 825 or AG 879, which inhibits ErbB2 kinase activity, we demonstrate that (1) the PAK-PIX interaction is essential for v-Ha-RAS-induced malignant transformation; (2) v-Ha-RAS requires not only ErbB1 but also ErbB2, which are activated through two independent autocrine pathways to induce both the PIX/Rac/CDC42-dependent PAK activation and malignant transformation in vitro; and (3) a combination of AG 879 and the Src family kinase-specific inhibitor PP1 suppresses almost completely the growth of RAS-induced sarcomas in nude mice.


CONCLUSIONS
These findings not only change our conventional view on the role of these RAS-inducible ligands and ErbB family receptors (serving as RAS activators) but also suggest a new avenue for the treatment of RAS-associated cancers by a combination of inhibitors specific for ERbB, Src, or PAK family kinases.
He
H
H
Ludwig Institute for Cancer Research, P.O. Box 2008, Royal Melbourne Hospital, Parkville/Melbourne, Australia 3050.
Hirokawa
Y
Y
Manser
E
E
Lim
L
L
Levitzki
A
A
Maruta
H
H
D016475:3T3 Cells / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D002417:Cattle; D018797:Cell Cycle Proteins / Q000378:metabolism*; D016895:Culture Media, Serum-Free; D004268:DNA-Binding Proteins; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000627:therapeutic use*; D005260:Female; D006023:Glycoproteins / Q000187:drug effects*; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D051379:Mice; D008819:Mice, Nude; D010446:Peptide Fragments / Q000494:pharmacology; D010940:Plant Proteins; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors*; D011799:Quinazolines; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000187:drug effects* / Q000502:physiology; D064067:Rho Guanine Nucleotide Exchange Factors; D012513:Sarcoma, Experimental / Q000188:drug therapy; D020032:Tyrphostins / Q000494:pharmacology / Q000627:therapeutic use*; D015854:Up-Regulation; D054462:p21-Activated Kinases; D019061:src-Family Kinases
D018797:Cell Cycle Proteins; D016895:Culture Media, Serum-Free; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D006023:Glycoproteins; D020662:Guanine Nucleotide Exchange Factors; D010446:Peptide Fragments; D010940:Plant Proteins; D017346:Protein Serine-Threonine Kinases; D017027:Protein Tyrosine Phosphatases; D011799:Quinazolines; D018719:Erb-b2 Receptor Tyrosine Kinases; D064067:Rho Guanine Nucleotide Exchange Factors; D020032:Tyrphostins; D054462:p21-Activated Kinases; D019061:src-Family Kinases; C081020:AG-879; C083693:PP1 protein, Physcomitrella patens; C101044:RTKI cpd