ERK-Dependent MKP-1–Mediated Cisplatin Resistance in Human Ovarian Cancer Cells

Abstract

Mitogen-activated protein kinase (MAPK) phosphatase-1 (MKP-1) is the MAPK phosphatase family member that negatively regulates MAPK signaling. Our previous study showed that MKP-1 is involved in cisplatin resistance, but the mechanism underlying its resistance is not understood. Here, we show that ERK2-mediated MKP-1 expression is critical for cisplatin resistance. Specifically, we showed that in the human ovarian cancer cell lines, cisplatin induces MKP-1 through phosphorylation. We also showed that inhibition of ERK2 activity by the MEK1/2 inhibitor U0126 or by small interfering RNA silencing decreases MKP-1 induction, leading to an increase in cisplatin-induced cell death, which mimicked the results obtained with cells in which MKP-1 is downregulated. Importantly, down-regulation of ERK2 decreased cisplatin-induced MKP-1 phosphorylation, suggesting that MKP-1 phosphorylation depends on ERK2 activity. Furthermore, down-regulation of ERK2 or MKP-1 enhanced cisplatininduced apoptosis. In addition, we showed that down-regulation of ERK2 or MKP-1 decreases the basal level of Bcl-2 protein and that inhibition of Bcl-2 activity sensitizes ovarian cancer cells to cisplatin. Collectively, our results indicate that induction of MKP-1 by cisplatin is through phosphorylation involving ERK signaling and that MKP-1 plays a critical role in ERK-mediated cisplatin resistance. Thus, our results suggest that targeting ERK-MKP-1 signaling could overcome cisplatin resistance in human ovarian cancer. [Cancer Res 2007;67(24):11933-41]

Role of Autophagy in Cisplatin Resistance in Ovarian Cancer Cells

“…Fig. 3A shows that cisplatin treatment caused phosphorylation of ERK, p38, and c-Jun N-terminal kinases (JNK) and their downstream targets including CREB, and c-Jun, confirming our previous study showing that cisplatin activates all three major MAPK path- ways (26). Next, we determined which MAPK is responsible for cisplatin-induced autophagy.…”

“…Cell Lines and Culture Conditions-Human ovarian cancer cell lines RMG-1, OV90, OV433, OVCA420, and CAOV3 were maintained as described previously (26). Immortalized human ovarian surface epithelial IOSE385 cells were obtained from Dr. Nelly Auersperg (University of British Columbia, Vancouver, Canada).…”

“…Transfections were performed as suggested by the manufacturer's instruction with slight modifications as described previously (26). Briefly, cells were seeded in 6-well plates (5 ϫ 10 5 cells/well).…”

Post-translational regulation of mitogen-activated protein kinase phosphatase-2 (MKP-2) by ERK

“…We included cisplatin in this experiment because our previous study showed that cisplatin treatment leads to increased MKP-1 protein levels and activates MAPKs. 27 Our purpose for using cisplatin treatment is to determine whether MKP-2 plays a role in the presence of DNA damage since cisplatin is a DNA damaging agent. In addition, we showed that both wild-type and S386A/ S391A mutant MKP-2 are potent inhibitors of ERK.…”

Mitogen-activated protein kinase phosphatase-1 (MKP-1) impairs the response to anti-epidermal growth factor receptor (EGFR) antibody cetuximab in metastatic colorectal cancer patients

“…The molecular mechanism underlying MKP-1-mediated resistance to anti-cancer drugs is in part due to the activation of JNK-driven apoptosis by several anti-tumour agents such as anthracyclines, taxanes, cisplatin, proteasome inhibitors and more recently anti-EGFR drugs. High levels of MKP-1 inhibit JNK and counterbalance the cytotoxic effects of such drugs (Sanchez-Perez et al, 1998Small et al, 2004Small et al, , 2007Wang et al, 2006Wang et al, , 2007Workman and de Bono, 2008;Rojo et al, 2009). With respect to anti-EGFR therapy, in vitro results with the anti-EGFR drug AG1478 showed that MKP-1-modulated JNK activation was critical for drug-induced apoptosis.…”