Kit and PDGFR-alpha activities are necessary for Notch4/Int3-induced tumorigenesis.
Transgenic mice overexpressing Notch4 intracellular domain (Int3) under the control of the whey acidic protein (WAP) or mouse mammary tumor virus-long terminal repeat promoters, develop mammary tumors. Microarray analysis of these tumors revealed high levels of c-Kit expression. Gleevec is a tyrosine kinase inhibitor that targets c-Kit, platelet-derived growth factor receptors (PDGFRs) and c-Abl. This led us to speculate that tyrosine kinase receptor activity might be a driving force in the development of Int3 mammary tumors. WAP-Int3 tumor-bearing mice were treated with continuous release of Gleevec using subcutaneously implanted Alzet pumps. Phosphorylation of c-Kit, PDGFRs and c-Abl is inhibited in Int3 transgenic mammary tumors by Gleevec. Inhibition of these enzymes is associated with a decrease in cell proliferation and angiogenesis, and an induction of apoptosis. To examine the signaling mechanisms underlying Notch4/Int3 tumorigenesis, we employed small interfering RNA (siRNA) to knock down c-Kit, PDGFRs and c-Abl alone or in combination and observed the effects on soft agar growth of HC11 cells overexpressing Int3. Only siRNA constructs for c-Kit and/or PDGFR-alpha were able to inhibit HC11-Int3 colony formation in soft agar. Our data demonstrate an inhibitory effect of Gleevec on Int3-induced transformation of HC11 cells and mammary tumors and indicate an oncogenic role for c-Kit and PDGFR-alpha tyrosine kinases in the context of Int3 signaling.
Raafat
A
A
Oncogenetics Section, Mammary Biology and Tumorigenesis Laboratory, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
Zoltan-Jones
A
A
Strizzi
L
L
Bargo
S
S
Kimura
K
K
Salomon
D
D
Callahan
R
R
D000818:Animals; D000970:Antineoplastic Agents / Q000627:therapeutic use; D001549:Benzamides; D015152:Blotting, Northern; D002454:Cell Differentiation; D049109:Cell Proliferation; D002471:Cell Transformation, Neoplastic; D002478:Cells, Cultured; D005260:Female; D000068877:Imatinib Mesylate; D047468:Immunoprecipitation; D008321:Mammary Glands, Animal / Q000254:growth & development*; D008325:Mammary Neoplasms, Experimental / Q000235:genetics / Q000473:pathology*; D008324:Mammary Tumor Virus, Mouse / Q000235:genetics; D051379:Mice; D008822:Mice, Transgenic; D008894:Milk Proteins / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D010879:Piperazines / Q000627:therapeutic use; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D016315:Proto-Oncogene Proteins c-abl / Q000378:metabolism; D019009:Proto-Oncogene Proteins c-kit / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011743:Pyrimidines / Q000627:therapeutic use; D034741:RNA, Small Interfering / Q000494:pharmacology; D000074562:Receptor, Notch4; D020796:Receptor, Platelet-Derived Growth Factor alpha / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D020797:Receptor, Platelet-Derived Growth Factor beta / Q000378:metabolism; D051880:Receptors, Notch / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction
D000970:Antineoplastic Agents; D001549:Benzamides; D008894:Milk Proteins; C106075:NOTCH4 protein, human; D010879:Piperazines; D011518:Proto-Oncogene Proteins; D011743:Pyrimidines; D034741:RNA, Small Interfering; D000074562:Receptor, Notch4; D051880:Receptors, Notch; C024471:whey acidic proteins; D000068877:Imatinib Mesylate; D011505:Protein-Tyrosine Kinases; D019009:Proto-Oncogene Proteins c-kit; D020796:Receptor, Platelet-Derived Growth Factor alpha; D020797:Receptor, Platelet-Derived Growth Factor beta; D016315:Proto-Oncogene Proteins c-abl