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

The mechanisms responsible for the development of the taxol resistance phenotype are unclear, and are likely explained by multiple mechanisms. To understand the molecular changes associated with drug resistance more fully, a taxol-resistant subline, derived from the human ovarian cancer cell line SKOV-3, was established through selection by culture in incrementally increasing 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 esistance (A) under bar ssociated (G) under bar ene-3). In comparison to the parental line, SKOV-3, TRAG-3 mRNA is overexpressed in the taxol-resistant cell 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 amino 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 analysis demonstrates that TRAG3 is overexpressed in the taxol-resistant breast cancer cell line MDA 435(TR) as well as the doxorubicin-resistant multiple myeloma cell lines 8226/DOX40 and 8226/MDR10V. A survey of normal tissue shows minimal or absent TRAG3 mRNA expression. Screening of a wide variety of cancer cell lines demonstrates TRAG-3 expression in many cell lines derived from different tissue types. In summary, TRAG-3 is a novel gene whose expression is associated with the chemotherapy-resistant and neoplastic phenotype. (C) 1999 Published by Elsevier Science B.V. All rights reserved.