BACKGROUND: Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) have shown modest clinical benefit in patients with relapsed nonsmall cell lung cancer (NSCLC). Down-regulation of Akt appears to correlate with the antitumor activity of EGFR-TKIs. Akt activates nuclear factor kappa B (NF-kappaB), which transcribes genes important for cell survival, invasion, and metastasis. The authors hypothesized that genistein, through the inhibition of NF-kappaB, could enhance the activity of EGFR-TKIs in NSCLCs. METHODS: Three NSCLC cell lines with various EGFR mutation status and sensitivities to EGFR-TKIs were selected: H3255 (L858R), H1650 (del E746-A750), and H1781 (wild-type EGFR). Cells were treated with erlotinib, gefitinib, genistein, or the combination of each of the EGFR-TKIs with genistein. Cell survival and apoptosis were assessed, and expression levels of EGFR, pAkt, cyclooxygenase-2 (COX-2), E-cadherin, prostaglandin E(2) (PGE(2)), and NF-kappaB were measured. RESULTS: Both EGFR-TKIs demonstrated growth inhibition and apoptosis in each of the cell lines, but H1650 and H1781 were much less sensitive. Genistein demonstrated some antitumor activity in all cell lines, but enhanced growth inhibition and apoptosis when combined with the EGFR-TKIs in each of the cell lines. Both combinations down-regulated NF-kappaB significantly more than either agent alone in H3255. In addition, the combinations reduced the expression of EGFR, pAkt, COX-2, and PGE(2,) consistent with inactivation of NF-kappaB. CONCLUSIONS: The authors concluded that genistein enhances the antitumor effects of EGFR-TKIs in 3 separate NSCLC cell lines. This enhanced activity is in part because of greater reduction in the DNA-binding activity of NF-kappaB when EGFR-TKIs were combined with genistein.
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