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

Abstract

Non-small-cell lung cancer (NSCLC) represents the most frequent and therapy-refractive sub-class of lung cancer. Improving apoptosis induction in NSCLC represents a logical way forward in treating this tumor. Cisplatin, a commonly used therapeutic agent in NSCLC, induces activation of N-terminal-c-Jun kinase (JNK) that, in turn, mediates induction of apoptosis. In analysing surgical tissue samples of NSCLC, we found that expression of MKP1/CL100, a negative regulator of JNK, showed a strong nuclear staining for tumor cells, whereas, in normal bronchial epithelia, MKP1 was localized in the cytoplasm as well as in nuclei. In the NSCLC-derived cell lines H-460 and H-23, we found that MKP1 was constitutively expressed. Expressing a small-interfering RNA (siRNA) vector for MKP1 in H-460 cells resulted in a more efficient activation by cisplatin of JNK and p38 than in the parental cells, and this correlated with a 10-fold increase in sensitivity to cisplatin. A similar response was also observed in H-460 and H-23 cells when treated with the MKP1 expression inhibitor RO-31-8220. Moreover, expression of a siRNA-MKP2, an MKP1-related phosphatase, had no effect on H-460 cell viability response to cisplatin. Tumors induced by H-460 cells expressing MKP1 siRNA grew slower in nu À /nu À mice and showed more susceptibility to cisplatin than parental cells, and resulted in an impaired growth of the tumor in mice. On the other hand, overexpression of MKP1 in the H-1299 NSCLC-derived cell line resulted in further resistance to cisplatin. Overall, the results showed that inhibition of MKP1 expression contributes to a slow down in cell growth in mice and an increase of cisplatin-induced cell death in NSCLC. As such, MKP1 can be an attractive target in sensitizing cells to cisplatin to increase the effectiveness of the drug in treating NSCLC.

DUSP1/MKP1 promotes angiogenesis, invasion and metastasis in non-small-cell lung cancer

“…NSCLC cells expressing a smallinterfering RNA (siRNA) specific for DUSP1 were more sensitive to cisplatin and grew more slowly when injected into nude mice. Chemical compounds that inhibit DUSP1 expression also induce higher sensitivity to cisplatin (Chattopadhyay et al, 2006). These results suggested that DUSP1 is an important target for tumor regression and understanding its function might lead to improvements in cell-death promoting chemotherapy.…”

“…Identification of genes differentially expressed in parental control versus DUSP1-deficient H460 lung cancer cells We have previously reported that expressing DUSP1-siRNA in H460 cells (H460cri) (Chattopadhyay et al, 2006) resulted in earlier phosphorylation of JNK and p38 in response to CDDP and differences in tumor growth. Thus, changes in gene expression controlled by both kinases could underlie this observation.…”

“…DUSP1 is a nuclear mitogen and stress-inducible MAP kinase phosphatase highly expressed in different types of human tumors, including non-small-cell lung cancer (NSCLC), breast, ovarian, bladder, osteosarcoma and in prostate cancer in early stages of disease (Loda et al, 1996;Denkert et al, 2002;Chattopadhyay et al, 2006). We have previously demonstrated that DUSP1 has an essential function in NSCLC biology (Chattopadhyay et al, 2006), both in tumor growth and in response to cisplatin treatment. NSCLC cells expressing a smallinterfering RNA (siRNA) specific for DUSP1 were more sensitive to cisplatin and grew more slowly when injected into nude mice.…”

Unphosphorylated STAT6 contributes to constitutive cyclooxygenase-2 expression in human non-small cell lung cancer

“…To explore the physiological significance of unphosphorylated STAT6, the sensitivity of apoptosis of the STAT6 DN cells and STAT6Y641W cells was investigated. Cisplatin, a commonly used chemotherapeutic reagent in lung cancer treatment (Wang and Lippard, 2005;Chattopadhyay et al, 2006), was utilized to treat the cells. The induction of apoptosis was determined by poly ADP-ribose polymerase (PARP) cleavage through Western analysis.…”

Human recombinant erythropoietin does not promote cancer growth in presence of functional receptors expressed in cancer cells

“…17 To test the significance of hrEPO supplementation with regard to tumor growth, aliquots containing 5 x 10 3 cells were seeded on a 24-well plate in standard medium supplemented either with 0.5% or 10% FBS ± 8 IU hrEPO. At subsequent 24 hourly intervals, cells were fixed with 1% glutaraldehyde and the number of cells determined by staining with crystal violet.…”