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Targeting the epidermal growth factor receptor in non-small cell lung cancer cells: the effect of combining RNA interference with tyrosine kinase inhibitors or cetuximab.

ABSTRACT: BACKGROUND:The epidermal growth factor receptor (EGFR) is a validated therapeutic target in non-small cell lung cancer (NSCLC). However, current single agent receptor targeting does not achieve a maximal therapeutic effect, and some mutations confer resistance to current available agents. In the current study we have examined, in different NSCLC cell lines, the combined effect of RNA interference targeting the EGFR mRNA, and inactivation of EGFR signaling using different receptor tyrosine kinase inhibitors (TKIs) or a monoclonal antibody cetuximab. METHODS:NSCLC cells (cell lines HCC827, H292, H358, H1650, and H1975) were transfected with EGFR siRNA and/or treated with the TKIs gefitinib, erlotinib, and afatinib, and/or with the monoclonal antibody cetuximab. The reduction of EGFR mRNA expression was measured by real-time quantitative RT-PCR. The down-regulation of EGFR protein expression was measured by western blot, and the proliferation, viability, caspase3/7 activity, and apoptotic morphology were monitored by spectrophotometry, fluorimetry, and fluorescence microscopy. The combined effect of EGFR siRNA and different drugs was evaluated using a combination index. RESULTS:EGFR-specific siRNA strongly inhibited EGFR protein expression almost equally in all cell lines and inhibited cell growth and induced cell apoptosis in all NSCLC cell lines studied, albeit with a different magnitude. The effects on growth obtained with siRNA was strikingly different from the effects obtained with TKIs. The effects of siRNA probably correlate with the overall oncogenic significance of the receptor, which is only partly inhibited by the TKIs. The cells which showed weak response to TKIs, such as the H1975 cell line containing the T790M resistance mutation, were found to be responsive to siRNA knockdown of EGFR, as were cell lines with downstream TKI resistance mutations. The cell line HCC827, harboring an exon 19 deletion mutation, was more than 10-fold more sensitive to TKI proliferation inhibition and apoptosis induction than any of the other cell lines. Cetuximab alone had no relevant in vitro activity at concentrations obtainable in the clinic. The addition of EGFR siRNA to either TKIs or cetuximab additively enhanced growth inhibition and induction of apoptosis in all five cell lines, independent of the EGFR mutation status (wild-type or sensitizing mutation or resistant mutation). The strongest biological effect was observed when afatinib was combined with an EGFR-specific siRNA. CONCLUSIONS:EGFR knockdown by siRNA further decreases the cell growth of lung cancer cells that are treated with TKIs or cetuximab alone, confirming that single agent drug targeting does not achieve a maximal biological effect. The siRNA inhibits EGFR oncogenic activity that bypasses downstream "resistance" mutations such as KRAS and PTEN. The combined treatment of siRNA and EGFR inhibitory agents is additive. The combination of a potent, irreversible kinase inhibitor such as afatinib, with EGFR-specific siRNAs should be further investigated as a new strategy in the treatment of lung cancer and other EGFR dependent cancers, including those with downstream resistance mutations.

SUBMITTER: Chen G

PROVIDER: S-EPMC3334713 | biostudies-literature | 2012 Mar

REPOSITORIES: biostudies-literature

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Targeting the epidermal growth factor receptor in non-small cell lung cancer cells: the effect of combining RNA interference with tyrosine kinase inhibitors or cetuximab.

Chen Gang G Kronenberger Peter P Teugels Erik E Umelo Ijeoma Adaku IA De Grève Jacques J

BMC medicine 20120321

<h4>Background</h4>The epidermal growth factor receptor (EGFR) is a validated therapeutic target in non-small cell lung cancer (NSCLC). However, current single agent receptor targeting does not achieve a maximal therapeutic effect, and some mutations confer resistance to current available agents. In the current study we have examined, in different NSCLC cell lines, the combined effect of RNA interference targeting the EGFR mRNA, and inactivation of EGFR signaling using different receptor tyrosin ...[more]

PMID: 22436374

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Project description:Lung cancer still represents the leading cause of cancer-related mortality. However, the recent advent of tyrosine kinase inhibitors (TKI), pioneering drugs against targetable mutations, have dramatically improved prognosis of advanced non-small cell lung cancer (NSCLC) patients. Anaplastic lymphoma kinase (ALK) gene rearrangements, identified in 3–7% of NSCLC cases, reflects in the constitutive activation of downstream signalling pathways, stimulating tumour cell proliferation, differentiation and survival. To accurately detect the wide spectrum of ALK rearrangements, the introduction of innovative techniques, like reverse transcriptase polymerase chain reaction (RT-PCR) or next generation sequencing (NGS) now allows for a more precise detection of variants and a more objective reading assessment, compared to the traditional diagnostic approaches. In some occasions, these new tools may dynamically monitor tumor evolution and even guide the choice of the most appropriate ALK inhibitor. In fact, among ALK TKIs available, crizotinib was the first to receive FDA accelerate approval for ALK rearranged NSCLC patients. Notwithstanding its response rate, ranging from 57% to 74%, the majority of patients progress within the first year of drug administration, due to acquired resistance. Both ALK-dependent and independent mechanisms of acquired resistance to TKIs have been identified. If the activation of multiple bypass signaling pathways constitutes the most common ALK-independent mechanism of resistance and one of the most difficult to overcome, ALK-dependent escape strategy mainly consists of mutations in the kinase domain, where the type of mutation largely depends on the TKI administered. Second and third generation TKIs are now available and are demonstrating high systemic and central nervous system (CNS) efficacy in clinical trials. Even though appropriate timing and sequencing of these compounds are still unclear, the large number of ALK inhibitors is now a precious resource aiming to prolong progression-free survival (PFS) and finally overall survival (OS). Here Authors provide an overview of the current approaches in the clinical management of advanced NSCLC patients harboring ALK rearrangement and discuss future perspectives to address current issues, highlighting the perception that ALK-rearranged advanced NSCLC patients benefit from maintained ALK inhibition for as long as possible.

Project description:AimsEpidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) have shown dramatic clinical benefits in advanced non-small cell lung cancer (NSCLC); however, resistance remains a serious problem in clinical practice. The present study analyzed mTOR-associated signaling-pathway differences between the EGFR TKI-sensitive and -resistant NSCLC cell lines and investigated the feasibility of targeting mTOR with specific mTOR inhibitor in EGFR TKI resistant NSCLC cells.MethodsWe selected four different types of EGFR TKI-sensitive and -resistant NSCLC cells: PC9, PC9GR, H1650 and H1975 cells as models to detect mTOR-associated signaling-pathway differences by western blot and Immunoprecipitation and evaluated the antiproliferative effect and cell cycle arrest of ku-0063794 by MTT method and flow cytometry.ResultsIn the present study, we observed that mTORC2-associated Akt ser473-FOXO1 signaling pathway in a basal state was highly activated in resistant cells. In vitro mTORC1 and mTORC2 kinase activities assays showed that EGFR TKI-resistant NSCLC cell lines had higher mTORC2 kinase activity, whereas sensitive cells had higher mTORC1 kinase activity in the basal state. The ATP-competitive mTOR inhibitor ku-0063794 showed dramatic antiproliferative effects and G1-cell cycle arrest in both sensitive and resistant cells. Ku-0063794 at the IC50 concentration effectively inhibited both mTOR and p70S6K phosphorylation levels; the latter is an mTORC1 substrate and did not upregulate Akt ser473 phosphorylation which would be induced by rapamycin and resulted in partial inhibition of FOXO1 phosphorylation. We also observed that EGFR TKI-sensitive and -resistant clinical NSCLC tumor specimens had higher total and phosphorylated p70S6K expression levels.ConclusionOur results indicate mTORC2-associated signaling-pathway was hyperactivated in EGFR TKI-resistant cells and targeting mTOR with specific mTOR inhibitors is likely a good strategy for patients with EGFR mutant NSCLC who develop EGFR TKI resistance; the potential specific roles of mTORC2 in EGFR TKI-resistant NSCLC cells were still unknown and should be further investigated.

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Targeting the epidermal growth factor receptor in non-small cell lung cancer cells: the effect of combining RNA interference with tyrosine kinase inhibitors or cetuximab.

Publications

Targeting the epidermal growth factor receptor in non-small cell lung cancer cells: the effect of combining RNA interference with tyrosine kinase inhibitors or cetuximab.

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