1. ¹Institute of Pathology, Charité, Campus Mitte, Humboldt University Berlin, Schumannstr. 20/21, Berlin D-10117, Germany
2. ²University of Tokyo, Genome Science Division, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8944, Japan

Correspondence: H Lage, Humboldt University Berlin, Charité Campus Mitte, Institute of Pathology, Schumannstr, 20/21, Berlin D-10117, Germany. E-mail: hermann.lage@charite.de

Received 22 January 2003; Revised 18 August 2003; Accepted 25 September 2003; Published online 8 December 2003.

Abstract

Elevated expression of the heparan sulphate proteoglycan glypican-3 (GPC3) was found on mRNA and protein levels in the atypical multidrug-resistant gastric carcinoma cell line EPG85-257RNOV, which was established by in vitro selection against mitoxantrone. In order to elucidate a putative role of GPC3 in the drug-resistant phenotype, the mitoxantrone-resistant cell line EPG85-257RNOV was transfected with an expression vector construct carrying an anti-GPC3 hammerhead ribozyme. It could be demonstrated that in anti-GPC3 ribozyme-transfected cell clones, the GPC3-specific mRNA and corresponding protein expression levels were decreased to levels that are similar to those observed in nonresistant, parental cells. The anti-GPC3 ribozyme-containing clones reduced the mitoxantrone resistance level up to 21% of the original resistance and the crossresistance against etoposide to 33% of the original value. This reversal of drug resistance was accompanied by an increased cellular mitoxantrone accumulation in the anti-GPC3 ribozyme-expressing cells. In conclusion, it was verified that GPC3 is involved in the cellular protection against mitoxantrone in the atypical multidrug-resistant gastric carcinoma cell line EPG85-257RNOV.