CXCR4 promotes gefitinib resistance of Huh7 cells by activating the c-Met signaling pathway.

C-X-C chemokine receptor type 4 (CXCR4) expression is associated with poor prognosis of hepatocellular carcinoma (HCC). The aim of this study was to explore the biological role of CXCR4 in gefitinib resistance of HCC. Compared with a normal, non-gefitinib-resistant, human HCC cell line (Huh7), CXCR4 mRNA and protein were highly expressed in gefitinib-resistant Huh7 cells (Huh7-R). Cell proliferation was decreased, and apoptosis was enhanced in Huh7 cells in the presence of gefitinib. These influences conferred by gefitinib treatment on proliferation and apoptosis of Huh7 cells were abolished by CXCR4 overexpression. CXCR4 knockdown reduced the proliferation ability of HuH-7R cells after gefitinib treatment. Importantly, CXCR4 overexpression had no influence on caveolin 1 (Cav-1) expression; similarly, Cav-1 silencing did not cause a substantive change in CXCR4 expression. However, CXCR4 activated Cav-1, c-Met, and Raf-1 in Huh7 cells, whereas Cav-1 silencing repressed the expression of Raf-1 and phosphorylated c-Met in Huh7 cells. CXCR4 overexpression promoted proliferation and repressed apoptosis in gefitinib-treated Huh7 cells, which was partly rescued by PHA-665752 (a c-Met inhibitor) treatment or c-Met deficiency. Finally, we constructed a tumor xenograft model to determine the influence of CXCR4 overexpression on tumor growth of HCC. CXCR4 overexpression accelerated tumor growth of HCC, which was abrogated by c-Met deficiency. These findings demonstrate that CXCR4 overexpression activates c-Met via the Cav-1 signaling pathway, thereby promoting gefitinib resistance of Huh7 cells. Thus, this study highlights novel insights into the mechanism of gefitinib resistance of HCC and CXCR4 may become a potential target for HCC treatment.

Comprehensive identification, fragmentation pattern, and metabolic pathways of gefitinib metabolites via UHPLC-Q-TOF-MS/MS: in vivo study of rat plasma, urine, bile, and faeces.

Gefitinib, the first approved inhibitor for oral epidermal growth factor receptor (EGFR), has been proved to be effective in non-small cell lung cancer with EGFR mutation. However, there are many metabolites of gefitinib that have not been identified in vivo. This study aims to identify the metabolites of gefitinib and its metabolic pathways in rats using ultra-high-performance liquid chromatography coupled with a quadrupole time-of-flight mass spectrometry (UHPLC-Q-TOF-MS/MS) detector. Protein precipitation, solid-phase and ultrasonic extraction were used for the pre-treatment of plasma, urine, bile and faeces samples. In this study, a total of 28 compounds were identified in rat plasma, 29 in bile, 20 in urine and 16 in faeces. 20 new compounds were firstly reported as metabolites of gefitinib. Reduction, hydroxylation, dealkylation and dehalogenation were the major metabolic pathways in phase I. For phase II, the main pathways were sulphate and glucuronide conjugation. The fragment ions of gefitinib and its metabolites were usually generated via the fracture of C1-O bond of propoxy on the C6 position of aniline quinazoline ring. The results may be valuable and important for understanding the metabolic process of gefitinib in clinical application and drug safety.

Reactive metabolite of gefitinib activates inflammasomes: implications for gefitinib-induced idiosyncratic reaction.

The epidermal growth factor receptor tyrosine kinase inhibitors (EGFR TKIs) have been approved for non-small cell lung cancer. Although EGFR TKIs are less toxic than traditional cytotoxic therapies, they cause many severe idiosyncratic drug reactions. Reactive metabolites can cause cellular damage with the release of danger-associated molecular patterns (DAMPs), which is thought to be involved in immune activation. Inflammasomes can be activated by DAMPs, and this may be a common mechanism by which DAMPs initiate an immune response. We tested the ability of afatinib, dacomitinib, erlotinib, gefitinib, and osimertinib to induce the release of DAMPs that activate inflammasomes. Human hepatocarcinoma functional liver cell-4 (FLC-4) cells were used for bioactivation of drugs, and the detection of inflammasome activation was performed with the human macrophage cell line, THP-1 cells. Gefitinib is known to be oxidized to a reactive iminoquinone metabolite. We found that the supernatant from the incubation of gefitinib with FLC-4 cells for 7 days led to increased caspase-1 activity and production of IL-1ß by THP-1 cells. In the supernatant of FLC-4 cells with gefitinib, the heat shock protein (HSP) 40, 70 and 90 were significantly increased. In addition, activated THP-1 cells secreted high mobility group box 1 (HMGB1) protein. These results support the hypothesis that the reactive iminoquinone metabolite can cause the release of DAMPs from hepatocytes, which in turn, can activate inflammasomes. Inflammasome activation may be an important step in the activation of the immune system by gefitinib, which in some patients, can cause immune-related adverse events.

Exacerbation of gefitinib-induced liver injury by glutathione reduction in mice.

Gefitinib (GEF) is the first selective tyrosine kinase inhibitor of epidermal growth factor receptor. It is associated with the occurrence of clinical drug-induced liver injury. Although GEF is metabolized to chemically reactive metabolites by cytochrome P450 3A and 1A enzymes and then conjugated to glutathione (GSH), whether these reactive metabolites contribute to GEF-induced toxicity remains unknown. In this study, we investigated whether GSH depletion can sensitize mice to liver injury caused by GEF. Male C57BL/6J mice were intraperitoneally pretreated with L-buthionine (S,R)-sulfoximine (BSO) at 700 mg/kg to inhibit GSH synthesis and then orally administered GEF at 500 mg/kg every 24 hr for 4 consecutive days. The coadministration of BSO and GEF increased plasma alanine aminotransferase (ALT) levels to approximately 700 U/L and 1600 U/L at 72 and 96 hr after the first administration, respectively, whereas the increase in plasma ALT levels in mice receiving GEF at 500 mg/kg alone was limited, suggesting that GSH plays a protective role in GEF-induced liver injury. Histological examination showed nuclear karyorrhexis and sporadic single hepatocyte death in the livers of BSO+GEF coadministered mice. In these mice, the hepatic expression levels of heme oxygenase 1 (Hmox1) and metallothionein 2 (Mt2) mRNA, caspase 3/7 enzymatic activity, and the amounts of 2-thiobarbiuric acid reactive substances were significantly increased, suggesting the presence of oxidative stress, which may be associated with hepatocellular death. Together, these results show that oxidative stress as well as the reactive metabolites of GEF are involved in GEF-induced liver injury in GSH-depleted mice.

Tentative identification of gefitinib metabolites in non-small-cell lung cancer patient plasma using ultra-performance liquid chromatography coupled with triple quadrupole time-of-flight mass spectrometry.

BACKGROUND: Gefitinib is an orally potent and selective ATP-competitive inhibitor of epidermal growth factor receptor (EGFR) tyrosine kinase and is commonly used to treat locally advanced or metastatic non-small-cell lung cancer (NSCLC) with sensitive EGFR mutations. Multiple adverse effects associated with gefitinib, including liver and lung injuries, severe nausea, and diarrhea, have limited its clinical application. Xenobiotic-induced bioactivation is thought to be an important reason for gefitinib toxicity, which encouraged us to clarify the metabolism of gefitinib in NSCLC patients. MATERIALS AND METHODS: An ultra-performance liquid chromatography coupled with triple quadrupole time-of-flight mass spectrometry (UPLCQ-TOF-MS) method was established to tentatively identify the metabolites of gefitinib in human plasma. The extracted ion chromatogram peak intensity threshold was set at 1500 cps with minimum MS and MS/MS peak intensities of 400 and 100 cps, respectively. RESULTS: A total of 18 tentative metabolites were identified. Eight novel tentative metabolites with metabolic changes in dechlorination, defluorination, and hydrogenation on the quinazoline skeleton; removal of a partial or complete 3-chloro-4-fluoroaniline-substituted group; and sulfate conjugation and taurine conjugation were newly discovered in human plasma. Based on structural analysis of the tentative metabolites, the metabolic pathways were proposed. In addition, the pathways of dechlorination, defluorination, and hydrogenation on the quinazoline skeleton; removal of partial or complete 3-chloro-4-fluoroaniline-substituted groups; and sulfate conjugation and taurine conjugation in humans in vivo indicate that novel metabolic pathways exist in humans. CONCLUSIONS: In summary, the metabolism of gefitinib in humans in vivo is extensive and complex. Based on in vivo evidence, the propoxy-morpholine ring side chain and O-methyl group are the critical metabolic regions of gefitinib in humans. The novel metabolic pathways differ from those of in vitro studies, suggesting that intestinal floral metabolism might be involved.

Reduced expression of CYLD promotes cell survival and inflammation in gefitinib-treated NSCLC PC-9 cells: Targeting CYLD may be beneficial for acquired resistance to gefitinib therapy.

The application of tyrosine kinase inhibitors (TKIs) to the epidermal growth factor receptor (EGFR) has been proven to be highly effective for non-small-cell lung cancer (NSCLC). However, patients often evolve into acquired resistance. The secondary mutations in EGFR account for nearly half of the acquired resistance. While the remaining 50% of patients exhibit tolerance to EGFR-TKIs with unclear mechanism(s). Cylindromatosis (CYLD), a deubiquitinase, functions as a tumor suppressor to regulate cell apoptosis, proliferation, and immune response, and so on. The role of CYLD in NSCLC EGFR-TKI resistance remains elusive. Here, we found CYLD was upregulated in PC-9 cells, whereas downregulated in PC-9 acquired gefitinib-resistant (PC-9/GR) cells in response to the treatment of gefitinib, which is consistent with the results in the Gene Expression Omnibus database. Overexpression of CYLD promoted a more apoptotic death ratio in PC-9/GR cells than that in PC-9 cells. In addition, silencing the expression of CYLD resulted in an increase of the expression level of interleukin-6, transforming growth factor-ß and tumor necrosis factor-α, which may contribute to acquired resistance of PC-9 cells to gefitinib. Taken together, our data in vitro demonstrate that PC-9/GR cells downregulated CYLD expression, enhanced subsequent CYLD-dependent antiapoptotic capacity and inflammatory response, which may provide a possible target for acquired gefitinib-resistant treatment in NSCLC.

In Vitro Inhibition of Human Aldehyde Oxidase Activity by Clinically Relevant Concentrations of Gefitinib and Erlotinib: Comparison with Select Metabolites, Molecular Docking Analysis, and Impact on Hepatic Metabolism of Zaleplon and Methotrexate.

Gefitinib and erlotinib are epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) with activity against metastatic non-small cell lung cancer. Aldehyde oxidase-1 (AOX1) is a cytosolic drug-metabolizing enzyme. We conducted an experimental and molecular docking study on the effect of gefitinib, erlotinib, and select metabolites on the in vitro catalytic activity of AOX1, as assessed by carbazeran 4-oxidation, and determined the impact of AOX1 inhibition on hepatic metabolism of zaleplon and methotrexate. Gefitinib, desmorpholinopropylgefitinib, erlotinib, desmethylerlotinib, and didesmethylerlotinib inhibited human hepatic cytosolic carbazeran 4-oxidation by a competitive mode, with inhibition constants in submicromolar or low micromolar concentrations. Desmethylgefitinib did not affect AOX1 catalytic activity. A similar pattern was obtained when investigated with human kidney cytosol or recombinant AOX1. The differential effect of gefitinib on human, rat, and mouse hepatic AOX1 catalytic activity suggests species-dependent chemical inhibition of AOX1. Erlotinib was considerably more potent than gefitinib in decreasing hepatic cytosolic zaleplon 5-oxidation and methotrexate 7-oxidation. Molecular docking analyses provided structural insights into the interaction between EGFR-TKIs and AOX1, with key residues and bonds identified, which provided favorable comparison and ranking of potential inhibitors. Based on the US Food and Drug Administration guidance to assess the risk of drug-drug interactions, the calculated R1 values indicate that further investigations are warranted to determine whether gefitinib and erlotinib impact AOX1-mediated drug metabolism in vivo. Overall, erlotinib desmethylerlotinib, didesmethylerlotinib, gefitinib, and desmorpholinopropylgefitinib are potent inhibitors of human AOX1 catalytic function and hepatic metabolism of zaleplon and methotrexate, potentially affecting drug efficacy or toxicity. SIGNIFICANCE STATEMENT: As epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs), gefitinib and erlotinib are first-line pharmacotherapy for metastatic non-small cell lung cancer. Our experimental findings indicate that clinically relevant concentrations of gefitinib, desmorpholinopropylgefitinib, erlotinib, desmethylerlotinib, and didesmethylerlotinib, but not desmethylgefitinib, inhibit human aldehyde oxidase (AOX1) catalytic activity and hepatic cytosolic metabolism of zaleplon and methotrexate. Molecular docking analysis provide structural insights into the key AOX1 interactions with these EGFR-TKIs. Our findings may trigger improved strategies for new EGFR-TKI design and development.

Marsdenia tenacissima extract promotes gefitinib accumulation in tumor tissues of lung cancer xenograft mice via inhibiting ABCG2 activity.

ETHNOPHARMACOLOGICAL RELEVANCE: Marsdenia tenacissima extract (MTE) is the water-soluble part of a traditional Chinese medicine Marsdenia tenacissima (Roxb.) Wight & Arn, and is commercially available in China for treating cancers. MTE has been revealed to be effective in improving gefitinib efficacy in treating non-small cell lung cancer (NSCLC). However, the mechanisms remain to be defined. AIM OF THE STUDY: To determine the effects of MTE on gefitinib metabolism and accumulation in vivo, and to explore the underlying mechanisms. MATERIALS AND METHODS: MTE or vehicle were intraperitoneally administrated to the H1975 xenograft model, followed by intragastric administration of gefitinib 12 h later. Mice plasma, tumors and liver tissues were harvested for further analysis. Hoechst 33342, a specific substrate of ATP Binding Cassette Subfamily G Member 2 (ABCG2), was used to determine the effects of MTE on activities of ABCG2 in tumor cells. RESULTS: A higher concentration of plasma gefitinib was detected in MTE-treated mice at 24 h after delivery of gefitinib, however, it became insignificant in another 24 h. By contrast, gefitinib levels were continuously higher in MTE-pretreated mice tumor tissues at 12-48 h post gefitinib administration. MTE suppressed plasma levels of gefitinib metabolites (M523595, M608236 and M537194) in the first 24 h after gefitinib delivery, and inhibited activities of liver CYP2D6 and CYP3A4 at early stage (within 6 h) after gefitinib treatment. Strikingly, the activities of ABCG2, the primary drug transporter for gefitinib, were significantly inhibited by MTE in H1975 lung cancer cells. Further, it was identified that tenacissoside H, but not tenacissoside I, may contribute to the ABCG2-suppressive effects of MTE. CONCLUSIONS: MTE pretreatment temporarily elevated plasma concentrations of gefitinib via inhibiting CYP450 enzymes. Most importantly, MTE promoted gefitinib accumulation in tumor tissues in a long-lasting manner via decreasing activities of ABCG2, a drug transporter responsible for gefitinib efflux.

Discovery of Potent and Selective Epidermal Growth Factor Receptor (EGFR) Bifunctional Small-Molecule Degraders.

Several epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors have been developed and approved by Food and Drug Administration for the treatment of non-small-cell lung cancers, but their efficacy can be compromised by acquired drug resistance conferred by EGFR-mutant variants. Here, we described the discovery of a novel E3 ligase von Hippel-Lindau-recruiting EGFR degrader, MS39 (compound 6), and a first-in-class E3 ligase cereblon-recruiting EGFR degrader, MS154 (compound 10), using the proteolysis targeting chimera technology. These compounds potently induced the degradation of mutant but not wild-type EGFR in an E3 ligase-dependent manner in cancer cell lines and effectively suppressed the growth of lung cancer cells compared with the corresponding negative controls. The global proteomic analyses revealed that the compounds were highly selective for EGFR. Furthermore, both compounds were bioavailable in mouse pharmacokinetic studies, and compound 6 is the first EGFR degrader suitable for in vivo efficacy studies. Overall, we provide a set of well-characterized chemical tools to the research community.

Development and validation of a sensitive LC-MS/MS method for determination of gefitinib and its major metabolites in human plasma and its application in non-small cell lung cancer patients.

Gefitinib, the first approved oral epidermal growth factor receptor (EGFR) inhibitor, has been demonstrated effective in cancers with EGFR active mutations. In this study, we established and validated a method for determining gefitinib and its main metabolites, M605211, M387783, M537194 and M523595 in patients with non-small cell lung cancer (NSCLC) by liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. The mobile phase was water: acetonitrile (35:65, v/v) with 0.1% formic acid at a flow-rate of 0.35 mL/min, within a 3 min run time. Gefitinib and its main metabolites were separated on a X-Terra RP18 column (50 × 2.1 mm, 3.5 µm) at 40 ℃ and subjected to mass analysis using positive electro-spray ionization (ESI). The calibration ranges of gefitinib and M523595 were 0.5-1000 ng/mL, and other compounds were 0.05-100 ng/mL with the correlation coefficients (r2) ≥ 0.99. Accuracies ranged from 92.60%-107.58 and the inter- and intra-assay precision were less than 15% for all analytes in quality control samples. There was no significant matrix effect. The ranges of extraction recoveries were 86-105% for all analytes and IS. Thirty plasmas were obtained from Sun Yat-sen university cancer center. The mean plasma concentration of (± SD) of gefitinib M537194, M523595, M387783 and M605211 were 247.18 (± 140.39) ng/mL, 7.78 (± 6.74) ng/mL, 101.09 (± 93.44) ng/mL, 1.6 (± 0.9) ng/mL and 11.63 (± 4.98) ng/mL, respectively. The validated LC/MS/MS method was effectively used in the determination of gefitinib and its four metabolites in NSCLC patients.