TRAG-3, a novel gene, isolated from a taxol-resistant ovarian carcinoma cell line

The mechanisms responsible for the development of the taxol resistance phen otype are unclear, and are likely explained by multiple mechanisms. To unde rstand the molecular changes associated with drug resistance more fully, a taxol-resistant subline, derived from the human ovarian cancer cell line SK OV-3, was established through selection by culture in incrementally increas ing taxol concentrations. Comparison of SKOV-3 to SKOV-3,, by differential display identifies a new gene, TRAG-3 ((T) under bar axol (R) under bar esi stance (A) under bar ssociated (G) under bar ene-3). In comparison to the p arental line, SKOV-3, TRAG-3 mRNA is overexpressed in the taxol-resistant c ell line SKOV-3(TR). The nucleotide sequence of the TRAG-3 cDNA contains an open reading frame of 333 bp that predicts for a protein product of 110 am ino acids. A GenBank search identifies a cosmid clone containing a genomic sequence corresponding to that of TRAG-3. DNA and protein analysis reveals that TRAG3 has no homology to any known cDNAs or proteins. Northern analysi s demonstrates that TRAG3 is overexpressed in the taxol-resistant breast ca ncer cell line MDA 435(TR) as well as the doxorubicin-resistant multiple my eloma cell lines 8226/DOX40 and 8226/MDR10V. A survey of normal tissue show s minimal or absent TRAG3 mRNA expression. Screening of a wide variety of c ancer cell lines demonstrates TRAG-3 expression in many cell lines derived from different tissue types. In summary, TRAG-3 is a novel gene whose expre ssion is associated with the chemotherapy-resistant and neoplastic phenotyp e. (C) 1999 Published by Elsevier Science B.V. All rights reserved.