Overexpression of the receptor tyrosine kinase Tie-1 intracellular domain in breast cancer.
OBJECTIVE
Tyrosine kinase with immunoglobulin and epidermal growth factor homology domains (Tie-1) is a receptor tyrosine kinase that regulates angiogenesis and antiapoptotic survival signaling. Tie-1 expression is generally associated with endothelial cells and neovascularization. We previously identified Tie-1 in human breast tumor samples using a PCR-based screen for protein kinases expressed in breast tumors. The purpose of this study was to determine the cell types expressing Tie-1, whether Tie-1 is expressed in tumor cells, and to examine the regulation of Tie-1 in breast cancer.


METHODS
Tie-1 expression was analyzed by Western blot and immunohistochemistry using an antibody to the carboxy terminus of Tie-1. Tie-1 expression was determined in a variety of cancer cell lines, clinical breast and colon tumor samples, and in corresponding benign tissue from the same patient. Tie-1 expression and distribution in breast tumors was scored by immunohistochemistry.


RESULTS
Tie-1 was overexpressed in 14/23 breast tumors compared with 0/9 corresponding normal tissues from the same patients. Immunohistochemistry revealed that Tie-1 was overexpressed in epithelial breast cancer cells and ductal carcinoma in situ. In all breast tumor samples, Tie-1 was expressed as a truncated 40- to 43-kD doublet consisting of the intracellular portion of the protein, which contains the tyrosine kinase catalytic domain. The 40- to 43-kD Tie-1 doublet was expressed in a broad variety of cell lines.


CONCLUSIONS
We have shown that breast cancer cells overexpress a cleaved form of the Tie-1 protein. Our results implicate the intracellular domain of Tie-1, which includes the catalytic kinase domain, in breast cancer progression.
Yang
Xi-Hui
XH
Department of Surgery, Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, NC 27599, USA.
Hand
Randal A
RA
Livasy
Chad A
CA
Cance
William G
WG
Craven
Rolf J
RJ
D014408:Biomarkers, Tumor / Q000096:biosynthesis* / Q000235:genetics; D001943:Breast Neoplasms / Q000201:enzymology* / Q000235:genetics; D002278:Carcinoma in Situ / Q000201:enzymology* / Q000235:genetics; D018270:Carcinoma, Ductal, Breast / Q000201:enzymology* / Q000235:genetics; D005260:Female; D006801:Humans; D017434:Protein Structure, Tertiary; D020794:Receptor Protein-Tyrosine Kinases / Q000096:biosynthesis* / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction
D014408:Biomarkers, Tumor; D020794:Receptor Protein-Tyrosine Kinases