PC3 human prostatic cancer cells, which are androgen-independent and hormone-nonresponsive, were used to examine the possible presence and expression of activin and its receptors in this cell line because activin is a member of transforming growth factor beta (TGF beta) superfamily which has been found to have growth-inhibitory activity. We have studied whether PC3 cells transcribe mRNAs coding for beta A- and beta B-subunits of activin, and activin receptors I, II, and IIB, and whether PC3 cells produce activin proteins. The expression and localization of the mRNAs were elucidated by the reverse transcription-polymerase chain reaction (RT-PCR) and in situ hybridization techniques. The presence of immunoreactivity for activin was determined by immunocytochemistry. We have observed that messenger RNAs encoding activin beta A-, beta B-subunits, and activin receptors I, II, and IIB, but not that of the alpha-subunit of inhibin, were expressed, and activin proteins, but not inhibin, are present in PC3 cells. Furthermore, the RT-PCR products were confirmed by DNA sequencing. We conclude that activins and their receptors are expressed in PC3 and suggest that activins may have autocrine functions in these cells.