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Hypoxia induces gefitinib resistance in non-small-cell lung cancer with both mutant and wild-type epidermal growth factor receptors.

ABSTRACT: Somatic mutations in the epidermal growth factor receptor (EGFR) gene, such as exon 19 deletion mutations, are important factors in determining therapeutic responses to gefitinib in non-small-cell lung cancer (NSCLC). However, some patients have activating mutations in EGFR and show poor responses to gefitinib. In this study, we examined three NSCLC cell lines, HCC827, PC9, and HCC2935, that expressed an EGFR exon 19 deletion mutation. All cells expressed mutant EGFR, but the PC9 and HCC2935 cells also expressed wild-type EGFR. The HCC827 cells were highly sensitive to gefitinib under both normoxia and hypoxia. However, the PC9 and HCC2935 cells were more resistant to gefitinib under hypoxic conditions compared to normoxia. Phosphorylation of EGFR and ERK was suppressed with gefitinib treatment to a lesser extent under hypoxia. The expression of transforming growth factor-? (TGF?) was dramatically upregulated under hypoxia, and the knockdown of TGF? or hypoxia-inducible factor-1? (HIF1?) reversed the resistance to gefitinib in hypoxic PC9 and HCC2935 cells. Finally, introduction of the wild-type EGFR gene into the HCC827 cells caused resistance to gefitinib under hypoxia. This phenomenon was also reversed by the knockdown of TGF? or HIF1?. Our results indicate that hypoxia causes gefitinib resistance in EGFR-mutant NSCLC through the activation of wild-type EGFR mediated by the upregulation of TGF?. The presence of wild-type and mutant EGFR along with tumor hypoxia are important factors that should be considered when treating NSCLC patients with gefitinib.

SUBMITTER: Minakata K

PROVIDER: S-EPMC7659171 | biostudies-literature | 2012 Nov

REPOSITORIES: biostudies-literature

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Hypoxia induces gefitinib resistance in non-small-cell lung cancer with both mutant and wild-type epidermal growth factor receptors.

Minakata Kunihiko K Takahashi Fumiyuki F Nara Takeshi T Hashimoto Muneaki M Tajima Ken K Murakami Akiko A Nurwidya Fariz F Yae Suzu S Koizumi Fumiaki F Moriyama Hiroyuki H Seyama Kuniaki K Nishio Kazuto K Takahashi Kazuhisa K

Cancer science 20120914 11

Somatic mutations in the epidermal growth factor receptor (EGFR) gene, such as exon 19 deletion mutations, are important factors in determining therapeutic responses to gefitinib in non-small-cell lung cancer (NSCLC). However, some patients have activating mutations in EGFR and show poor responses to gefitinib. In this study, we examined three NSCLC cell lines, HCC827, PC9, and HCC2935, that expressed an EGFR exon 19 deletion mutation. All cells expressed mutant EGFR, but the PC9 and HCC2935 cel ...[more]

PMID: 22863020

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Project description:BackgroundNon-small cell lung cancer (NSCLC) expressed high levels of epidermal growth factor receptor (EGFR). Gefitinib (Iressa) has demonstrated clinical efficacy in NSCLC patients harboring EGFR mutations or refractory to chemotherapy. However, most of NSCLC patients are with wild type EGFR, and showed limited response to gefitinib. Therefore, to develop new effective therapeutic interventions for NSCLC is still required. Our previous study showed Marsdenia tenacissima extract (MTE) restored gefitinib efficacy in the resistant NSCLC cells, but whether MTE acts in the gefitinib-sensitive NSCLC cells is the same as it in the resistant one is unknown.MethodsDose response curves for gefitinib and MTE were generated for two sensitive NSCLC cell lines with mutant or wild type EGFR status. Three different sequential combinations of MTE and gefitinib on cell growth were evaluated using IC50 and Combination Index approaches. The flow cytometric method was used to detect cell apoptosis and cell cycle profile. The impact of MTE combined with gefitinib on cell molecular network response was studied by Western blotting.ResultsUnlike in the resistant NSCLC cells, our results revealed that low cytotoxic dose of MTE (8 mg/ml) combined gefitinib with three different schedules synergistically or additively enhanced the growth inhibition of gefitinib. Among which, MTE→MTE+gefitinib treatment was the most effective one. MTE markedly prompted cell cycle arrest and apoptosis caused by gefitinib both in EGFR mutant (HCC827) and wild type of NSCLC cells (H292). The Western blotting results showed that MTE→MTE+gefitinib treatment further enhanced the suppression of gefitinib on cell growth and apoptosis pathway such as ERK1/2 and PI3K/Akt/mTOR. This combination also blocked the activation of EGFR and c-Met which have cross-talk with each other. Unlike in gefitinib-resistant NSCLC cells, MTE alone also demonstrated certain unexpected modulation on EGFR related cell signal pathways in the sensitive cells.ConclusionOur results suggest that MTE is a promising herbal medicine to improve gefitinib efficacy in NSCLC regardless of EGFR status. However, why MTE acted differently between gefitinib-sensitive and -resistant NSCLC cells needs a further research.

Dataset Information

Hypoxia induces gefitinib resistance in non-small-cell lung cancer with both mutant and wild-type epidermal growth factor receptors.

Publications

Hypoxia induces gefitinib resistance in non-small-cell lung cancer with both mutant and wild-type epidermal growth factor receptors.

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