S. Chatterjee et al., HYPERSENSITIVITY TO DNA CROSS-LINKING AGENTS ASSOCIATED WITH UP-REGULATION OF GLUCOSE-REGULATED STRESS PROTEIN GRP78, Cancer research, 57(22), 1997, pp. 5112-5116
We have shown previously that NAD/poly(ADP-ribose) polymerase-deficien
t cells that overexpress M-r 78,000 glucose-regulated stress protein (
GRP78) are resistant to topoisomerase II inhibitors, such as etoposide
, m-amsacrine, and doxorubicin. However, these cells have been found t
o be hypersensitive to DNA cross-linking agents, including melphalan,
cisplatin, and 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU). These obse
rvations prompted us to examine whether overexpression of GRP78 is ass
ociated with modulation of cytotoxicity of clinically useful DNA-cross
-linking agents such as melphalan, BCNU, and cisplatin. We up-regulate
d GRP78 in V79 Chinese hamster cells by 2-5-fold using two independent
approaches that include exposure to 6-aminonicotinamide, or 2-deoxygl
ucose. Subsequently, these GRP78-overexpressing cells were trypsinized
, plated in regular medium without GRP78-inducing agents, and allowed
a 5-h attachment time before being treated with melphalan, BCNU, or ci
splatin for 1 h to determine clonogenic survivals. In addition, repair
of DNA cross-links induced by those agents were determined by alkalin
e elution assay. Our results show that the GRP78-overexpressing V79 ce
lls are hypersensitive to DNA cross-linking agents compared to the con
trol V79 cells. Furthermore, repair of drug-induced DNA cross-links ap
pears to be considerably slower in these cells relative to that found
in control V79 cells, Thus, our results suggest that (a) up-regulation
of GRP78 is associated with an impairment of DNA cross-link repair, (
b) up-regulation of GRP78 is associated with potentiation of cytotoxic
ity induced by alkylating and platinating agents, and (c) up-regulatio
n of GRP78 can be considered as a potentially useful tool to modulate
the cytotoxicity of clinically useful alkylating and platinating agent
s.