Inhibin activin subunits and activin receptors in human breast cell-lines and lactating rat mammary-glands.

We have reported previously that a human breast cancer cell line, MCF-7, transcribes messenger RNAs coding inhibin/activin alpha-, beta A-, and beta B-subunits and activin receptor II as well as produces inhibin and/or activin proteins, using immunocytochemistry, in situ hybridization, and the reverse transcription-polymerase chain reaction (RT-PCR) analysis. In the present study, we report that four additional cell lines derived from human breast cancers, T47D, HS-578, ZR-75-1, and MDA-MB 321 express mRNAs for alpha- and beta-subunits of inhibin/activin and activin receptors as well as stain positive with antisera specific for inhibin alpha- and inhibin/activin beta-subunits, respectively. We have also localized immunocytochemically inhibin and activin-A in rat lactating mammary glands and found mRNAs for activin receptors I, II, and IIB as well as follistatin, a binding protein for activin, in lactating rat mammary glands by RT-PCR. These findings provide additional evidence that inhibin and activin may be involved in regulating the normal and abnormal cell growth of mammary glands.