Receptor tyrosine kinase EphB4 is a survival factor in breast cancer.
EphB4, a member of the largest family of receptor tyrosine kinases, is normally expressed on endothelial and neuronal cells. Although aberrant expression of EphB4 has been reported in several human tumors, including breast cancer, its functional significance is not understood. We report here that EphB4 is expressed in 7 of 12 (58%) human breast cancer specimens and 4 of 4 (100%) breast tumor cell lines examined. Overexpression of EphB4 in breast cancer cells was driven by gene amplification and by the erbB family of receptors via activation of Janus tyrosine kinase-signal transducers and activators of transcription and protein kinase B. The aberrantly expressed receptor was phosphorylated by its natural ligand, EphrinB2, and signaled via the protein kinase B pathway. Targeted knockdown of EphB4 expression by small interference RNA (and antisense oligodeoxynucleotides (ODNs)) led to dose-dependent reduction in cell survival, increased apoptosis, and sensitization to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). Antisense ODN-mediated EphB4 knockdown resulted in reduced tumor growth in a murine tumor xenograft model. Antisense ODN-treated tumors were 72% smaller than control tumors at 6 weeks, with an 86% reduction in proliferating cells, 15-fold increase in apoptosis, and 44% reduction in tumor microvasculature. Our data indicate that biologically active EphB4 functions as a survival factor in breast cancer and is a novel target for therapy.
Kumar
S Ram
SR
Department of Pathology, Keck School of Medicine of the University of Southern California, 1441 Eastlake Avenue, NOR 6330, Los Angeles, CA 90033, USA.
Singh
Jasbir
J
Xia
Guangbin
G
Krasnoperov
Valery
V
Hassanieh
Loubna
L
Ley
Eric J
EJ
Scehnet
Jeffrey
J
Kumar
Neil G
NG
Hawes
Debra
D
Press
Michael F
MF
Weaver
Fred A
FA
Gill
Parkash S
PS
D000818:Animals; D017209:Apoptosis / Q000502:physiology; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D001943:Breast Neoplasms / Q000378:metabolism* / Q000473:pathology*; D045744:Cell Line, Tumor; D002470:Cell Survival; D016373:DNA, Antisense; D036388:Ephrin-B2 / Q000378:metabolism; D005260:Female; D005784:Gene Amplification; D006801:Humans; D015151:Immunoblotting; D007150:Immunohistochemistry; D008562:Membrane Glycoproteins / Q000378:metabolism; D051379:Mice; D009361:Neoplasm Invasiveness; D018739:Oncogene Proteins v-erbB / Q000378:metabolism; D016133:Polymerase Chain Reaction; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D034741:RNA, Small Interfering; D036224:Receptor, EphB4 / Q000235:genetics / Q000378:metabolism*; D053221:TNF-Related Apoptosis-Inducing Ligand; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D051017:Apoptosis Regulatory Proteins; D016373:DNA, Antisense; D036388:Ephrin-B2; D008562:Membrane Glycoproteins; D018739:Oncogene Proteins v-erbB; D034741:RNA, Small Interfering; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; C505654:Tnfsf10 protein, mouse; D014409:Tumor Necrosis Factor-alpha; D036224:Receptor, EphB4; D051057:Proto-Oncogene Proteins c-akt