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.