The insulin-like growth factor binding protein BP-25 is expressed by human breast cancer cells.
Specific binding proteins are thought to modulate the effects of IGF-I. Previous work has demonstrated that media conditioned by human breast cancer cells contains IGF-I binding activity. Radiolabelled IGF-I incubated with serum-free conditioned media from the breast cancer cell line MDA-MB 231 eluted with an apparent M.W. of 35-40 kDa when analyzed by gel filtration chromatography at pH 7.4. The M.W. of this binding activity corresponded to that of BP-25, a binding protein cloned from the hepatocellular carcinoma cell line HepG2. Two breast cancer cell lines, MDA-MB 231 and Hs578T, were found to express BP-25 RNA. Specific BP-25 radioimmunoassay detected BP-25 production in the conditioned media of these two cell lines. Immunoprecipitation confirmed that metabolically labelled MDA-MB 231 released 30 kDa BP-25 into its medium. This study demonstrates that some breast cancer cells express the IGF-I binding protein, BP-25.
Yee
D
D
Medicine Branch, National Cancer Institute, Bethesda, Maryland 20892.
Favoni
R E
RE
Lupu
R
R
Cullen
K J
KJ
Lebovic
G S
GS
Huff
K K
KK
Lee
P D
PD
Lee
Y L
YL
Powell
D R
DR
Dickson
R B
RB
D001943:Breast Neoplasms / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D002460:Cell Line; D005260:Female; D006801:Humans; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008970:Molecular Weight; D012334:RNA, Neoplasm / Q000235:genetics; D013002:Somatomedins / Q000378:metabolism*
D002352:Carrier Proteins; D018969:Insulin-Like Growth Factor Binding Proteins; D012334:RNA, Neoplasm; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I