Resistance to drug treatment is a common observation in malignant melanoma,
In order to analyze alterations in mRNA expression profiles associated wit
h drug resistance in melanoma cells we previously established a panel of va
rious drug-resistant cell variants derived from the human melanoma line MeW
o and compared the mRNA expression profiles by a differential display techn
ique, By that approach it could be demonstrated that the expression level o
f a mRNA encoded by a gene found to be mutated in non-syndromic hearing imp
airment, DFNA5 (ICERE-1), was distinctly decreased in the 33-fold etoposide
-resistant melanoma cell line MeWo ETO I. To evaluate the hypothesis that a
decrease in DFNA5 mRNA expression level contributes to the acquired etopos
ide resistance phenotype exhibited by MeWo ETO 1 cells, this drug-resistant
line was stably transfected with the DFNA5-encoding cDNA, Transfected clon
es showed a 30-35%, reduced etoposide susceptibility by comparing the IC25,
IC50 and IC75 values Of these clones with those displayed by the non-trans
fected, etoposide-resistant melanoma cell line MeWo ETO I and controls. Fur
thermore, etoposide exposure of stable DFNA5 transfectants resulted in an i
ncrease of caspase-3-mediated apoptotic events in DFNA5-transfected clones
in comparison to MeWo ETO 1 cells and controls. The data therefore demonstr
ate that a decrease in DNFA5 mRNA expression level is associated with an in
creased etoposide resistance in melanoma cells due to an elevated cellular
susceptibility to trigger a caspase-3-depending signal pathway leading to p
rogrammed cell death. (C) 2001 Federation of European Biochemical Societies
. Published by Elsevier Science B,V, All rights reserved.