Cisplatin induces a persistent activation of JNK that is related to cell death

Abstract

Genotoxic stress triggers signalling pathways that either mediate cell killing or protection of a ected cells. While induction of p53 is observed for most of the genotoxins, activation of MAPK/SAPK cascades is not a general response. The role of MAPK/SAPK activation on cell fate, seems to be dependent, in some systems, on the balanced response among both cascades. We have here examined the e ect of cis and trans-DDP on the activation of ERK and JNK activities. While no signi®cant induction of ERK was observed with the compounds, both of them are able to strongly activate JNK. Trans-DDP response is rapid and transient while the cis-DDP one is slow and persistent. In contrast with the observed nuclear translocation of JNK in response to U.V. light, none of the platinum compounds induces translocation, on the contrary, activation of JNK occurs in both the nuclear and cytoplasmic compartments. Inhibition of tyrosine phosphatases by orthovanadate pretreatment prolongs the time of JNK induction in response to both platinum compounds. The positive modulation of JNK activation correlates with an increase in toxicity that, for cis-DDP corresponds to a tenfold decrease in the IC 50 . A strong increase in MKP-1 levels was observed only in response to trans-DDP suggesting the involvement of this activity in the downregulation of JNK activity in response to this compound. Altogether the results suggest that the prolonged activation of JNK in response to cis-DDP contributes to cell death induction.

MKP1/CL100 controls tumor growth and sensitivity to cisplatin in non-small-cell lung cancer

“…In agreement with this latter study, we found differences in sub-cellular distribution of MKP1: mainly cytoplasmic in normal tissue and nuclear in tumor tissue. As the preferred substrate of MKP1 is JNK and this is translocated to the nuclei following a stimulus (Sa´nchez-Pe´rez et al, 1998), it appears reasonable to propose that a preferential distribution of MKP1 to this sub-cellular compartment would be to facilitate its access to the substrate. Furthermore, we found that expression of MKP1 was detected from very early stages in tumor development and maintained until later stages, indicating that it should be advantageous for tumor progression.…”

“…Cell extracts, Western blots and RT-PCR Whole-cell extracts were prepared essentially as described previously (Sa´nchez-Pe´rez et al, 1998). Western blotting was performed using standard methods (Sa´nchez-Pe´rez et al, 1998).…”

“…Western blotting was performed using standard methods (Sa´nchez-Pe´rez et al, 1998). For RT-PCR, total RNA was isolated from cells using Trizol (Life Technologies, Rockville, MD, USA) according to the manufacturer's instructions.…”

“…Cell viability, growth kinetic and clonogenic assay determinations Cell viability was determined using a crystal violet staining method followed by colorimetric assay, as described previously (Sa´nchez-Pe´rez et al, 1998). For the growth kinetic studies, cells were plated in triplicate at 1000 cells/well in a 24-well plate and allowed to grow in normal culture medium.…”

“…MKP1/CL100 is an immediate-early gene whose expression is regulated by mitogenic, inflammatory and DNA-damage stimuli (Beltman et al, 1996;Sa´nchez-Pe´rez et al, 1998;Li et al, 2001). Although MKP1 levels in normal cells are low, increased levels of MKP1 have been found in human ovarian carcinoma, breast and prostate cancer (Srikanth et al, 1999;Denkert et al, 2002;Wang et al, 2003).…”