Similarity between natural and recombinant human alpha-fetoprotein as inhibitors of estrogen-dependent breast cancer growth

Abstract

Alpha-fetoprotein (AFP) isolated from rodent amniotic fluid or human cord sera, upon incubation with a molar excess of estradiol, is converted to a form which inhibits estrogen-stimulated tissue growth. The purpose of this study was to determine whether recombinant human AFP produced in an E. coli expression system retained this function. The recombinant protein was similar to the natural protein isolated from pooled human cord sera in all functional aspects evaluated. It was detected by monoclonal and polyclonal antibodies to the natural protein. Following exposure to estradiol, it was converted to an inhibitor of estrogen-stimulated growth of immature mouse uterus yielding a dose/response curve similar to that of the natural protein. It inhibited the growth of estrogen-dependent (MCF-7) but not estrogen-independent (MDA-MB-231) breast cancer xenografts with the same schedule dependency and resultant histological changes as the natural protein. Availability of large quantities of homogeneous, biologically active recombinant human AFP will facilitate further studies of structure/function, mechanism, and therapeutic potential of this agent as a regular of breast cancer growth.

Gravidomimetic Prevention of Breast Cancer

“…the peptide could be used after cancers have become tamoxifen-resistant (and when the patient has very few options), or b.) the peptide could be used in conjunction with tamoxifen, especially if we could show that lower doses of tamoxifen (or of both drugs) would be efficacious, thereby delaying onset of resistance to tamoxifen, or c.) the peptide could be used alone, in replacement of tamoxifen, especially since the pep tide, unlike tamoxifen, is not uterotrophic (18). Similar potential presumably exists for the prevention aspects of the drug vis a vis tamoxifen.…”

“…A bioassay for antiestrotrophic activity was performed by using an immature mouse uterine growth assay based on previous studies, which demonstrated that i.p. administration of 0.5 jxg E 2 to these mice doubled their uterine weights with a corresponding increase in mitotic figures by 24 h after E 2 (3,18). Swiss/Webster female mice, 6-8 g in body weight (13-15 days old), were obtained from Taconic Farms.…”

“…Cyclization of peptides was accomplished using methods described by Kates et al (17,18). Briefly, N-alpha Fmoc-L-glutamic acid-alpha-allyl ester at the C-terminus of the synthetic peptide was coupled to the resin via the gamma carboxylic acid.…”

“…Removal of the N'-Fmoc allowed the remaining amino acids to be incorporated sequentially into the growing peptide. A free alpha-carboxyl group was then generated upon removal of the allyl group from the C-terminal Glu (18). Peptidyl-resin was dried in an incubator and the tube was flushed with nitrogen delivered through a septum.…”

Hemoglobin-associated proteins isolated from blood serum of Ehrlich carcinoma-bearing mice

“…The transgenic mice strain MMTV-neu (ErbB-2) with transplanted breast cancer showed that the liver of tumor-bearing mice displayed a fetal phenotype with expression of α-fetoprotein (AFP) (8). AFP acts as a growth factor and biological response modifier, which affects cell proliferation (9)(10)(11)(12). AFP functions as a transporter of various ligands, such as steroid hormones and hemoglobin degradation products (bilirubin) (13)(14)(15).…”