EXPRESSION AND LOCALIZATION OF ACTIVIN RECEPTORS IN A HUMAN MYELOID-LEUKEMIA CELL-LINE, THP-1

THP-1, a human myeloid leukemia cell line, which secretes activin-A af ter phorbol ester induced cell differentiation, was used to examine th e possible expression and presence of activin receptors because activi n, a member of the transforming growth factor beta (TGF-beta) superfam ily, has been found to be up-regulated by phorbol ester. We have studi ed whether THP-1 cells transcribe mRNAs encoding for activin receptors II and IIB by the reverse transcription-polymerase chain reaction (RT -PCR) and in situ hybridization techniques. To confirm that THP-1 cell s produce activin-A, we also determined the presence of immunoreactivi ty for activin-A by immunocytochemistry. We observed that messenger RN A encoding activin beta A-subunit was also expressed in THP-1 cells. F urthermore, the identity of RT-PCR products was confirmed by DNA seque ncing. These results indicate that activin-A and its receptors are co- expressed in THP-1 cells and suggest that activin-A may have autocrine functions during cell proliferation in these cells.