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  2. Abstract

Proteasome inhibitor PS-341 induces growth arrest and apoptosis of multiple myeloma (MM) cells via inactivation of NF-κB in vitro and has afforded some objective responses in individuals with relapsed, refractory MM. However, the activity of PS-341 against non-hematological malignancies remains to be fully elucidated. In this study, we found that PS-341 induced growth arrest and apoptosis of NCI-H520 and -H460 non-small cell lung cancer (NSCLC) cells in conjunction with markedly up-regulated levels of p21waf1 and p53, and down-regulation of bcl-2 protein in these cells. Also, PS-341 caused phosphorylation of c-Jun NH2-terminal kinase (JNK) and c-Jun, and enhanced AP-1/DNA binding activities in these cells as measured by western blotting and enzyme-linked immunosorbent assay (ELISA), respectively. Interestingly, when the JNK/ c-Jun/AP-1 signal pathway was disrupted by the JNK inhibitor SP600125, the ability of PS-341 to inhibit the growth of NSCLC cells and to up-regulate the levels of p21waf1 in these cells was blunted, but the expression of p53 was sustained at a high level, suggesting that the JNK/c-Jun/AP-1 signal pathway might mediate the anti-lung cancer effects of PS-341, with p21waf1 playing the central role. Thus, PS-341 might be useful for the treatment of individuals with NSCLC.


non-small cell lung cancer


multiple myeloma


c-Jun NH2-terminal kinase




extracellular signal-regulated protein kinase


mitogen-activated protein kinase


activator protein-1


ubiquitin-proteasome pathway


nuclear factor-κB


phosphate-buffered saline


enzyme-linked immunosorbent assay


tumor necrosis factor α

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