Bovine seminal ribonuclease (
BS RNase), a dimeric homolog of bovine
pancreatic ribonuclease has been proven to have important
biological properties as aspermatogenic, antitumor, embryotoxic and immunosuppressive activities. Recently we published preliminary results concerning the ability of
bovine seminal ribonuclease (
BS RNase) to induce time dependent apoptosis in Con-A stimulated human lymphocytes and in human
tumor cells based on
DNA content and cell cycle analysis. In this study we bring more confirmative data concerning the concentration dependent in vitro induction of apoptosis in stimulated human lymphocytes and
tumor cells of three human cell lines using the most sensitive and specific cytometric method for at present apoptosis determination the indirect TUNEL.
BS RNase 50 microg/ml was proven to induce 49.7, 54 and 68.1% apoptosis in the cells of the ML-2 myeloid cell line and two
neuroblastoma cell lines: NB-1 and NB-2, respectively. In Con A-stimulated human lymphocytes,
BS RNase also induced apoptosis, eventhough not so pronounced as in human tumor cell lines. In all cultures the induction of apoptosis was proportional to
BS RNase concentration ranging from 2-50 microg/ml and correlated with proportional decrease in 3H-thymidine incorporation into the newly synthesized
DNA. Side by side with the ability of
BS RNase to suppress the growth of human
tumors transplanted to nude mice, these
biological properties determine this
enzyme as a promising agent with potential clinical application.