MKP1 repression is required for the chemosensitizing effects of NF-@kB and PI3K inhibitors to cisplatin in non-small cell lung cancer

Cancer Lett 286(2):11 (2009) PMID 19553005

Treatment of non-small cell lung cancer (NSCLC) with cisplatin has a level of antitumor activity still modest. We have shown previously that MKP1/DUSP1 inhibits cisplatin-induced apoptosis in NSCLC cells and is overexpressed in tumors from most patients with stage I-II NSCLC. Here, using different NSCLC cell lines we found that MKP1 and NF-@kB are differentially expressed. We studied whether targeting MKP1, NF-@kB or both affects cisplatin-induced cell death. MKP1 is expressed in H460 and H727 cells. H727 and H1299 cells showed constitutive phosphorylation of Akt and increased NF-@kB activity than did H460 cells. H460-MKP1-siRNA-expressing cells (but not H727-MKP1-siRNA or H1299-MKP1-siRNA cells) exhibit a marked increase in cisplatin response compared with parental cells. Treatment with the PI3K inhibitor LY294002 or the NF-@kB inhibitor BAY11-7082 enhanced cisplatin antitumor activity in parental H1299 cells but only weakly affected responses of H727 and H460 cells. MKP1-siRNA expression enhanced the chemosensitization effect of LY294002 and BAY11-7082 on H727 and H460 cells. Additionally, NSCLC cell lines with higher NF-@kB-constitutive activation were the most sensitive to PS-341 (Bortezomib), a non-specific NF-@kB inhibitor. This finding suggests the proteasome as a suitable strategy in treating NSCLC tumors with high constitutive NF-@kB activity. Altogether, these results showed that either an activated PI3K/Akt/NF-@kB pathway and/or high MKP1 was linked to reduced sensitivity to cisplatin in NSCLC cells. Inhibition of NF-@kB or PI3K potently enhanced cisplatin cytotoxicity in cells with endogenous or genetically induced low MKP1 levels. These findings support the potential improvement in cisplatin responses by co-targeting NF-@kB or Akt and MKP1.