Molecular Endocrinology, Vol 3, 567-574, Copyright © 1989 by Endocrine Society

ARTICLES

Characterization of insulin-like growth factor binding proteins from human breast cancer cells

DD De Leon, DM Wilson, B Bakker, G Lamsom, RL Hintz and RG Rosenfeld
Department of Pediatrics, Stanford University Medical Center, California 94305.

The insulin-like growth factor binding proteins (IGF-BPs) are structurally and immunologically distinct from the IGF type 1 or type 2 receptors and are characterized by two major forms: a large, GH- dependent BP found in human plasma (Mr = 150 k) and a small GH- independent BP (Mr = 28-42 k) present in human plasma, amniotic fluid, and HEP G2 cells. Using affinity cross-linking techniques, we have identified several binding proteins secreted by human breast cancer cell lines (Hs578T, MDA-231, T-47D, and MCF-7). Under nonreducing conditions these proteins migrated at an apparent Mr = 35, 28, 27, and 24 k, while reducing conditions revealed bands of apparent Mr = 35, 32, 27, and 24 k. Competitive binding studies in T-47D-conditioned media demonstrated that these BPs bound more IGF-II than IGF-I, and that IGF- II potently inhibited binding of either IGF-I or -II. Immunological studies using a polyclonal antibody against the HEP G2 small BP revealed no immunoreactive BP in conditioned media from MCF-7 and T-47D and only slight immunoreactivity in conditioned media from Hs578T and MDA 231. Analysis by Northern blot, using a probe from the cDNA sequence of the HEP G2 BP, demonstrated that Hs578T and MDA-231 cell lines contained small amounts of the 1.65 kilobase mRNA characteristic of the HEP G2 BP, while MCF-7 and T-47D tested negative.(ABSTRACT TRUNCATED AT 250 WORDS)

This article has been cited by other articles:

				Y. H. Ibrahim and D. Yee Insulin-Like Growth Factor-I and Breast Cancer Therapy Clin. Cancer Res., January 15, 2005; 11(2): 944s - 950s. [Abstract] [Full Text] [PDF]