Activation of c‐Jun NH2‐terminal kinase is required for gemcitabine's cytotoxic effect in human lung cancer H1299 cells

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Abstract
Although gemcitabine is a potent therapeutic agent in the treatment of human non‐small cell lung cancer (NSCLC), resistance to gemcitabine is common. In this study, we investigated the molecular mechanisms involved in acquired gemcitabine resistance against NSCLC cells. Gemcitabine‐resistant NSCLC H1299 cells (H1299/GR) were selected by long‐term exposure of parental H1299 cells to gemcitabine. The median inhibitory concentrations of gemcitabine in H1299 and H1299/GR cells were 19.4 and 233.1 nM, respectively. Gemcitabine induced activation of c‐Jun NH2‐terminal kinase (JNK) in parental H1299 cells but not in H1299/GR cells after 48 h. Blocking JNK activation by pretreatment with SP600125, a specific JNK inhibitor, or by transfection with dominant‐negative JNK vectors abrogated gemcitabine‐induced apoptosis in parental H1299 cells as evidenced by interruption of caspase activation. Transient transfection with a JNKK2–JNK1 plasmid expressing constitutive JNK1 partially restored the effect of gemcitabine in H1299/GR cells. Our results indicate that gemcitabine‐induced apoptosis in human NSCLC H1299 cells requires activation of the JNK signaling pathway. Attenuated JNK activation may contribute to development of acquired gemcitabine resistance in cancer cells.

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