Article

Erlotinib-mediated inhibition of EGFR signaling induces metabolic oxidative stress through NOX4.

Free Radical and Radiation Biology Program, Department of Radiation Oncology, Holden Comprehensive Cancer Center, The University of Iowa, Iowa City, Iowa 52242, USA.
Cancer Research (Impact Factor: 8.65). 06/2011; 71(11):3932-40. DOI: 10.1158/0008-5472.CAN-10-3425
Source: PubMed

ABSTRACT Redox regulation of epidermal growth factor receptor (EGFR) signaling helps protect cells against oxidative stress. In this study, we investigated whether the cytotoxicity of an EGFR tyrosine kinase inhibitor, erlotinib (ERL), was mediated by induction of oxidative stress in human head and neck cancer (HNSCC) cells. ERL elicited cytotoxicity in vitro and in vivo while increasing a panel of oxidative stress parameters which were all reversible by the antioxidant N-acetyl cysteine. Knockdown of EGFR by using siRNA similarly increased these oxidative stress parameters. Overexpression of mitochondrial targeted catalase but not superoxide dismutase reversed ERL-induced cytotoxicity. Consistent with a general role for NADPH oxidase (NOX) enzymes in ERL-induced oxidative stress, ERL-induced cytotoxicity was reversed by diphenylene iodonium, a NOX complex inhibitor. ERL reduced the expression of NOX1, NOX2, and NOX5 but induced the expression of NOX4. Knockdown of NOX4 by using siRNA protected HNSCC cells from ERL-induced cytotoxicity and oxidative stress. Our findings support the concept that ERL-induced cytotoxicity is based on a specific mechanism of oxidative stress mediated by hydrogen peroxide production through NOX4 signaling.

0 Bookmarks
 · 
130 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Lung cancer is the leading cause of cancer deaths, emphasizing the need for better treatments. In patients with EGFR-mutant NSCLC, increased responses to platinum-based chemotherapies have been seen, compared to EGFR wild-type cancers. However, the mechanisms underlying this association have remained elusive. Here, we confirmed in a panel of 9 lung cancer cell lines, that mutant EGFR was associated with a range of cisplatin sensitivities, with the most sensitive cell line displaying a more than 35-fold lower survival fraction than EGFR wild-type lines (for 16 μM cisplatin). Cisplatin sensitivity can be associated with defects in the Fanconi Anemia (FA) pathway, which functions in the detection and repair of DNA ICL at stalled replication forks. Strikingly, EGFR-mutant cells displayed the hallmarks of the FA phenotype, namely increased cell kill, damage-induced G2 cell-cycle arrest, and chromosomal radial formation in response to ICL introduced by mitomycin C. In ICL repair the FA pathway produces DSB intermediates, which are subsequently repaired by HRR. RAD51 is the key mediator in HRR. EGFR-mutant cells exhibited an impaired RAD51 foci response specifically after ICL induction. Impaired RAD51 foci formation in EGFR-mutant cells was resistant to inhibition of EGFR downstream signaling, implying a kinase-independent regulation of HRR. Supporting this notion, overexpression of wild-type EGFR in EGFR-mutant cells was able to rescue RAD51 foci formation, while siRNA-mediated depletion of wild- type EGFR, but not kinase inhibition suppressed RAD51 foci. The effect of EGFR mutation was epistatic with a defective FA pathway caused by mutated FANCD2, as the presence of either or both of these mutations resulted in virtually identical DNA damage levels. We identified a defect downstream of FANCD2 at the level of recruitment of the FAN1 nuclease and ICL unhooking. FAN1 has a putative dual role in unhooking ICL and in resolving HJ late in HRR. HRR defects can be exploited by targeted treatment with PARP inhibitors. Indeed, in response to the PARP inhibitor olaparib, FAN1 foci failed to form in EGFR- mutant cells compared to wild-type cells (13% versus 29%). Interestingly RAD51 foci formed initially normally in EGFR-mutant cells, suggesting that the RAD51 foci defect seen after ICL induction was due to a lack of DNA substrate secondary tofailed ICL incision. However, RAD51 foci persisted >24 hours (25.6% vs 5.1%) in EGFR-mutant cells, indicating an inability to complete HRR. EGFR-mutant lung cancer cell lines demonstrated reduced clonogenic survival after olaparib treatment, with IC50 values < 6 μM for 8/9 cell lines, compared to > 6 μM for all EGFR wild-type cell lines. Consistent with this phenotype, we observed increased DNA damage levels in biopsy material from EGFR-mutant NSCLC treated with olaparib ex-vivo compared to wild-type tumor, i.e., 21% vs 4% cells with !H2AX foci (p=0.03). In conclusion, we describe an EGFR kinase-independent disruption of the FA pathway downstream of FANCD2 in EGFR-mutant cells, which impairs ICL unhooking or completion of HRR in response to cisplatin or olaparib treatment, respectively. EGFR-mutant lung cancer patients thus may benefit from treatment with PARP inhibitors.
    11/2013, Degree: Dr. rer. nat./PhD, Supervisor: Henning Willers
  • [Show abstract] [Hide abstract]
    ABSTRACT: Based on the thieno[2,3-d]pyrimidine scaffold, a series of new 4-amino-6-aryl thienopyrimidines have been prepared and evaluated as EGFR tyrosine kinase inhibitors. The in vitro activity was found to depend strongly on the substitution pattern in the 6-aryl ring, the stereochemistry, and the basicity at the secondary 4-amino group. A stepwise optimization by combination of active fragments led to the discovery of three structures with EGFR IC50 < 1 nM. The most potent drug candidate had an IC50 of 0.3 nM towards EGFR and its mutants L858R and L861Q. Studies using human cancer cell lines and an EGFR-L858R reporter cell system revealed good cellular potency, verifying the identified thienopyrimidines as promising lead structures.
    European journal of medicinal chemistry 01/2014; 75:354–374. · 3.27 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Drug interactions are an on-going concern in the treatment of cancer, especially when targeted therapies, such as tyrosine kinase inhibitors (TKI) or mammalian target of rapamycin (mTOR) inhibitors, are being used. The emergence of elderly patients and/or patients with both cancer and other chronic co-morbidities leads to polypharmacy. Therefore, the risk of drug-drug interactions (DDI) becomes a clinically relevant issue, all the more so as TKIs and mTOR inhibitors are essentially metabolised by cytochrome P450 enzymes. These DDIs can result in variability in anticancer drug exposure, thus favouring the selection of resistant cellular clones or the occurrence of toxicity. This review provides a comprehensive overview of DDIs that involve targeted therapies approved by the FDA for the treatment of solid tumours for more than 3 years (sorafenib, sunitinib, erlotinib, gefitinib, imatinib, lapatinib, everolimus, temsirolimus) and medicinal herb or drugs. This review also provides some guidelines to help oncologists and pharmacists in their clinical practice.
    Critical reviews in oncology/hematology 08/2013; · 5.27 Impact Factor

Full-text (2 Sources)

View
18 Downloads
Available from
Jun 1, 2014