Toxicology 156 (2001) 101 – 107 Bacillus intermedius ribonuclease as inhibitor of cell proliferation and membrane current Olga Ilinskaya a , Katrin Decker b , Andreas Koschinski b , Florian Dreyer b , Holger Repp b, * a Department of Microbiology, Kazan State Uniersity, Kremleskaya Street 18, 420008 Kazan, Russia b Rudolf -Buchheim-Institute of Pharmacology, Justus -Liebig -Uniersity of Giessen, Frankfurter Street 107, 35392 Giessen, Germany Received 3 May 2000; received in revised form 6 June 2000; accepted 6 September 2000 Abstract The antiproliferative action of the guanine-specific ribonuclease secreted by Bacillus intermedius (binase) was studied in different chicken and mouse cell lines. The proliferation rate of chicken embryo fibroblasts, either normal or Rous sarcoma virus-transformed, was significantly reduced by binase treatment. Among mouse fibroblasts, v-ras -transformed NIH3T3 cells were sensitive to binase, whereas the growth of non-transformed, v-src -transformed or v-fms -transformed NIH3T3 cells was not affected. A 48 h treatment with binase inhibited the Ca 2 + -dependent K + current of v-ras -transformed NIH3T3 cells but had no effect on this membrane current in non-transformed and in v-src - or v-fms -transformed NIH3T3 cells. Our results suggest that mammalian cells expressing the ras -oncogene are a potential target for the antiproliferative action of binase. © 2001 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Bacillus intermedius RNase (binase); Chicken embryo fibroblasts; Mouse fibroblasts; Transformation; Proliferation; Ca 2 + -dependent K + current www.elsevier.com/locate/toxicol 1. Introduction A number of ribonucleases, such as binase (Bacillus intermedius RNase), pancreatic RNase A, bovine seminal ribonuclease, and RNase from oocytes of Rana pipiens (onconase) were shown to possess enzymatic and biological activities which may be exploited for the development of novel cytotoxic agents (Youle et al., 1993; Di Donato et al., 1994; Mikulski et al., 1995; Boque and Wlo- dawer, 1996; Prior et al., 1996). To assess the possibilty of a future clinical application of bacte- rial ribonucleases, the toxicity of these enzymes in various cell lines is currently under investigation. Compared to pancreatic RNase A, binase is a more effective growth inhibitor of Ehrlich ascites tumor cells and also of the ascitic form of lymp- Abbreiations: CEF, chicken embryo fibroblast; EGTA, ethyleneglycol-bis( -aminoethyl)-N,N,N’,N’ -tetraacetic acid; HEPES, 2-[4-(2-hydroxyethyl)-1-piperazine]-ethanesulfonic acid; LPA, lysophosphatidic acid; RNA, ribonucleic acid; RNase, ribonuclease; RSV, Rous sarcoma virus. * Corresponding author. Tel.: +49-641-9947622; fax: +49- 641-9947609. E-mail address: holger.repp@pharma.med.uni-giessen.de (H. Repp). 0300-483X/01/$ - see front matter © 2001 Elsevier Science Ireland Ltd. All rights reserved. PII: S0300-483X(00)00335-8