Identification of the insulin-like growth factor binding proteins 5 and 6 (IGFBP-5 and 6) in human breast cancer cells.
Four estrogen receptor-positive (ER+) [MCF-7, T47D, ZR75 and BT474] and 3 ER- [Hs578T, MDA-MB-468 and MDA-MB-231] human breast cancer cell lines were examined for expression of the IGFBP-5 and IGFBP-6 genes. Northern blot analysis revealed that all cell lines, except MDA-MB-231, expressed IGFBP-5 mRNA. IGFBP-6 mRNA, however, was expressed only by the ER- cell lines. Western immunoblotting indicated that the previously unidentified 31-kDa and 32-kDa IGF binding species secreted by these cell lines are IGFBP-5. The levels of IGFBP-4 and IGFBP-5 were increased in MCF-7 cells by estradiol and IGF-I, respectively, indicating that these BPs may contribute to the growth stimulatory response to these mitogens.
Sheikh
M S
MS
Department of Medicine and Cancer Center, University of Maryland, Baltimore.
Shao
Z M
ZM
Clemmons
D R
DR
LeRoith
D
D
Roberts
C T
CT
Fontana
J A
JA
D015152:Blotting, Northern; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000737:chemistry*; D002352:Carrier Proteins / Q000032:analysis*; D005260:Female; D006801:Humans; D018975:Insulin-Like Growth Factor Binding Protein 5; D018969:Insulin-Like Growth Factor Binding Proteins; D008934:Mitogens / Q000032:analysis; D012333:RNA, Messenger / Q000032:analysis; D011956:Receptors, Cell Surface / Q000032:analysis; D017451:Receptors, Somatomedin; D013002:Somatomedins / Q000032:analysis*; D014407:Tumor Cells, Cultured / Q000737:chemistry*
D002352:Carrier Proteins; D018975:Insulin-Like Growth Factor Binding Protein 5; D018969:Insulin-Like Growth Factor Binding Proteins; D008934:Mitogens; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D017451:Receptors, Somatomedin; D013002:Somatomedins