title: The influence of cell growth media on the stability and antitumour activity of methionine enkephalin.
abstract: Studies with cultured tumour cell lines are widely used in vitro to evaluate peptide-induced cytotoxicity as well as molecular and biochemical interactions. The objectives of this study were to investigate the influence of the cell culture medium on peptide metabolic stability and in vitro antitumour activity. The degradation kinetics of the model peptide methionine enkephalin (Met-E, Tyr-Gly-Gly-Phe-Met), demonstrated recently to play an important role in the rate of proliferation of tumour cells in vitro and in vivo, were investigated in cell culture systems containing different amounts of fetal bovine serum (FBS). The influence of enzyme inhibitors (bestatin, captopril, thiorphan) on the Met-E degradation was also investigated. The results obtained in the Dulbecco's modified Eagle medium containing 10% FBS indicated a rapid degradation of Met-E (t(1/2) = 2.8 h). Preincubation of the medium with a mixture of peptidase inhibitors reduced the hydrolysis of Met-E, as shown by the increased half-life to 10 h. The in vitro activity of Met-E against poorly differentiated cells from lymph node metastasis of colon carcinoma (SW620) and human larynx carcinoma (HEp-2) cells was determined. Tumour cells were grown for 3 weeks prior to the experiment in a medium supplemented with 10%, 5% or 2% FBS. Statistically significant to mild or no suppression of cell proliferation was observed in all cultures. In both cell lines, a significant suppression of cell growth by a combination of peptidase inhibitors and Met-E, compared with cells exposed to the peptide alone and cells grown in the absence of Met-E, was observed. This study indicated that caution must be exercised in interpreting the antiproliferative effects of peptide compounds in conventional drug-response assays.
authors.affiliation: Department of Nuclear Medicine, Radiation Protection and Pathophysiology, Clinical Hospital Osijek, School of Medicine Osijek, Croatia. glavas-obrovac.ljubica@kbo.hr
authors.forename: Ljubica
authors.initials: L
authors.lastname: Glavas-Obrovac
authors.forename: Andreja
authors.initials: A
authors.lastname: Jakas
authors.forename: Saska
authors.initials: S
authors.lastname: Marczi
authors.forename: Stefica
authors.initials: S
authors.lastname: Horvat
mesh_terms: D000970:Antineoplastic Agents / Q000737:chemistry* / Q000494:pharmacology*; D049109:Cell Proliferation / Q000187:drug effects; D003470:Culture Media; D004354:Drug Screening Assays, Antitumor; D004744:Enkephalin, Methionine / Q000737:chemistry* / Q000494:pharmacology*; D006801:Humans; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D003470:Culture Media; D004744:Enkephalin, Methionine