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.