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Characterization of a novel amphiregulin‐related molecule in 12‐ O ‐tetradecanoylphorbol‐13‐acetate‐treated breast cancer cells
Author(s) -
MartinezLacaci Isabel,
Johnson Gibbes R.,
Salomon David S.,
Dickson Robert B.
Publication year - 1996
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/(sici)1097-4652(199612)169:3<497::aid-jcp10>3.0.co;2-3
Subject(s) - amphiregulin , 12 o tetradecanoylphorbol 13 acetate , cancer research , chemistry , cancer , molecule , breast cancer , medicine , oncology , biology , biochemistry , signal transduction , phorbol ester , protein kinase c , organic chemistry , epidermal growth factor receptor
Amphiregulin (AR) can be induced at the mRNA level by 17‐β‐estradiol (E 2 ) or the phorbol ester tumor promoter 12‐ O ‐tetradecanoylphorbol‐13‐acetate (TPA). This study compares the effects of TPA and E 2 on the regulation of processing of AR isoforms and on subcellular localization in human MCF‐7 breast cancer cells. AR was localized in the nucleus of MCF‐7 cells after E 2 treatment, whereas it was predominantly secreted after TPA treatment. AR isoforms of 28, 18, and 10 kDa and an additional species of approximately 55–60 kDa were detected in the cellular conditioned media after TPA stimulation. Expression of this unusual AR isoform was inhibited by protein kinase C (PKC) inhibitors such as bryostatin or H‐7. The biochemical properties of this isoform are consistent with it being an N ‐linked glycosylated form of the AR precursor that contains unprocessed mannose residues. The size of this large isoform is reduced to approximately 40 kDa after treating the TPA‐induced MCF‐7 cells with tunicamycin or treating the conditioned media of such cells with N ‐glycosidase F or with endoglycosidase H. Moreover, this isoform is able to bind several lectins with specificity for mannose residues. The 55–60 kDa glycosylated AR isoform, like lower Mr AR isoforms, is able to bind to heparin and to stimulate the growth of MCF‐10A cells by interacting with the EGF receptor. These data suggest that TPA activation of PKC may be involved in post‐translational modifications of AR, such as glycosylation, and in alteration of its subcellular routing to predominantly a secretory pathway. © 1996 Wiley‐Liss, Inc.