Effects of Src inhibitors on cell growth and epidermal growth factor receptor and MET signaling in gefitinib-resistant non-small cell lung cancer cells with acquired MET amplification

The efficacy of epidermal growth factor receptor (EGFR)–tyrosine kinase inhibitors such as gefitinib and erlotinib in non-small cell lung cancer (NSCLC) is often limited by the emergence of drug resistance conferred either by a secondary T790M mutation of EGFR or by acquired amplification of the MET gene. We now show that the extent of activation of the tyrosine kinase Src is markedly increased in gefitinib-resistant NSCLC (HCC827 GR) cells with MET amplification compared with that in the gefitinib-sensitive parental (HCC827) cells. In contrast, the extent of Src activation did not differ between gefitinib-resistant NSCLC (PC9/ZD) cells harboring the T790M mutation of EGFR and the corresponding gefitinib-sensitive parental (PC9) cells. This activation of Src in HCC827 GR cells was largely abolished by the MET-TKI PHA-665752 but was only partially inhibited by gefitinib, suggesting that Src activation is more dependent on MET signaling than on EGFR signaling in gefitinib-resistant NSCLC cells with MET amplification. Src inhibitors blocked Akt and Erk signaling pathways, resulting in both suppression of cell growth and induction of apoptosis, in HCC827 GR cells as effectively as did the combination of gefitinib and PHA-665752. Furthermore, Src inhibitor dasatinib inhibited tumor growth in HCC827 GR xenografts to a significantly greater extent than did treatment with gefitinib alone. These results provide a rationale for clinical targeting of Src in gefitinib-resistant NSCLC with MET amplification. ( Cancer Sci 2009)     

Alveolar hemorrhage as a possible adverse drug reaction by gefitinib (ZD1839, Iressa)

We experienced a case in which severe alveolar hemorrhage occurred in the course of gefitinib therapy. A 56-year-old man with non-small cell lung cancer had been treated with CDDP + CPT-11, CDDP + GEM + VNR, CDDP + TXT. After the chemotherapy with these regimens was found to be ineffective, daily oral gefitinib was started. Four weeks later, the patient complained of cough, bloody sputum and dyspnea. Chest X-ray and CT showed bilateral infiltrations with air bronchogram. Fiberoptic bronchoscopy revealed alveolar hemorrhage with an increase of lymphocytes in the BALF. After the cessation of gefitinib therapy and the administration of steroid, he gradually recovered.     

Functional polymorphisms of the microsomal epoxide hydrolase gene: a reappraisal on a early-onset lung cancer patients series

As concomitant chemoradiotherapy for stage III NSCLC is associated with survival advantage in comparison to a sequential approach, we conducted a phase III randomised study aiming to determine the best sequence and safety of chemotherapy (CT) and chemoradiotherapy (CT-RT), using a regimen with cisplatin (CDDP), gemcitabine (GEM) and vinorelbine (VNR). Unresectable stage III NSCLC patients received CDDP (60 mg/m(2)), GEM (1g/m(2), days 1 and 8) and VNR (25mg/m(2), days 1 and 8) with reduced dosage of GEM and VNR during radiotherapy (66Gy). Two cycles of CT with radiotherapy followed by two further cycles of CT alone were administered in arm A or the reverse sequence in arm B. The study was prematurely closed for poor accrual due to administrative problems. Forty-nine eligible patients were randomised. Response rates and median survival times were, respectively 57% (95% CI: 36-78%) and 17 months (95% CI: 9.3-24.6 months) in arm A and 79% (95% CI: 64-94%) and 23.9 months (95% CI: 13.3-34.5 months) in arm B (p>0.05). Chemotherapy dose-intensity was significantly reduced in arm A. Grade 3-4 oesophagitis occurred in 5 patients. One case of grade 5 radiation pneumonitis was observed. In conclusion, chemoradiotherapy with CDDP, GEM and VNR appears feasible as initial treatment or after induction chemotherapy. Consolidation chemoradiotherapy seems less toxic with a better observed response rates and survival although no valid conclusion can be drawn from the comparison of both arms.     

Enhanced cytotoxicity induced by gefitinib and specific inhibitors of the Ras or phosphatidyl inositol-3 kinase pathways in non-small cell lung cancer cells

In this study, we have characterized a panel of NSCLC cell lines with differential sensitivity to gefitinib for activating mutations in egfr, pik3ca, and k-ras, and basal protein expression levels of PTEN. The egfr mutant NSCLC cell line H1650 as well as the egfr wild type cell lines H292 and A431 were highly sensitive to gefitinib treatment, indicating that other factors determine gefitinib-sensitivity in egfr wild type cells. Activating k-ras mutations were specifically detected in gefitinib-resistant cells, suggesting that the occurrence of k-ras mutations is correlated with resistance to EGFR antagonists. No pik3ca mutations were detected within the panel of cell lines, and PTEN protein expression levels did not correlate with gefitinib sensitivity. Gefitinib effectively blocked Akt and Erk phosphorylation in two gefitinib-sensitive NSCLC cell lines, further supporting our previous findings that persistent activity of the PI3K/Akt and/or Ras/Erk pathways is associated with gefitinib-resistance of NSCLC cell lines. Gefitinib-resistant NSCLC cell lines, showing EGFR-independent activity of the PI3K/Akt or Ras/Erk pathways, were treated with gefitinib in combination with specific inhibitors of mTOR, P13K, Ras, and MEK. Additive cytotoxicity was observed in A549 cells co-treated with gefitinib and the MEK inhibitor U0126 or the farnesyl transferase inhibitor SCH66336 and in H460 cells treated with gefitinib and the PI3K inhibitor LY294002, but not in H460 cells treated with gefitinib and rapamycin. These data suggest that combination treatment of NSCLC cells with gefitinib and specific inhibitors of the PI3K/Akt and Ras/Erk pathways may provide a successful strategy.     

Better survival with EGFR exon 19 than exon 21 mutations in gefitinib-treated non-small cell lung cancer patients is due to differential inhibition of downstream signals

Somatic mutations in the epidermal growth factor receptor (EGFR) kinase domain are associated with sensitivity to tyrosine kinase inhibitors (TKIs) in patients with non-small cell lung cancer (NSCLC). Our clinical data showed NSCLC patients with exon 19 deletions survived longer following gefitinib treatment than those with exon 21 point mutations. We aimed to investigate whether these two mutations produced differences in phosphorylation of EGFR and downstream signals. Two stable cell lines expressing these mutations were obtained by transfection. Inhibition of phosphorylation of EGFR, Akt, and Erk by gefitinib was detected using Western blotting, and cell inhibition tests were conducted to evaluate the bio-behavior. Gefitinib inhibited the phosphorylation of EGFR, Akt, and Erk to a greater degree in exon 19 deletion cells than in L858R cells. Gefitinib produced G1 arrest in more of the cells with exon 19 deletion than with L858R. This might be attributable to patient selection in TKIs therapy.     

Cisplatin, gemcitabine and vinorelbine in locally advanced or metastatic non-small-cell lung cancer: A phase I study

Purpose: The objective of this study was to determine the maximally tolerable doses (MTDs) of vinorelbine (VNR) and gemcitabine (GEM) when combined with a fixed dose of cisplatin (CDDP).Patients and methods: Chemotherapy-naïve patients with stage IIIB–IV non-small-cell lung cancer (NSCLC) received a fixed dose of CDDP (50 mg/m²) and escalating doses of VNR (starting from 20 mg/m²) and GEM (starting from 800 mg/m²) on days 1 and 8, every three weeks. The single escalation of GEM alone, by 200 mg/m² at each step, was initially planned up to a dose of 1,200 mg/m², to be followed by increments of the VNR dose of 5 mg/m² at each step.Results: Thirty-one patients were enrolled at five different dose levels. The escalation was stopped at level 4 (GEM 1,200 mg/m² and VNR 25 mg/m²) since two of six patients of this cohort showed dose-limiting neutropenia at treatment cycle 1. Two different dose levels, GEM 1,200 mg/m² + VNR 20 mg/m², and GEM 1,000 mg/m² + VNR 25 mg/m², were fairly well tolerated. No treatment-related deaths occurred. Neutropenia was the main toxic effect, occurring in 76% of the total of 116 cycles delivered, and in 24% of them was of grades 3 or 4. A total of eight patients (26%) experienced grade 4 neutropenia lasting more than seven days; in five of them it occurred in the first course. Neutropenic fever was observed in four cases. Grade 4 thrombocytopenia occurred in only two patients. Non-hematologic toxicity was a minor problem in all patients but was never dose-limiting. No complete responses were obtained, but sixteen out of 31 (52%) patients achieved partial responses. The median duration of response was 20 (range 6–56+) weeks, while at a nine-month median follow-up, the median survival time has not yet been reached. To date, 18 patients are still alive. The one-year projected survival for all patients was 51%.Conclusions: Our results show that CDDP, VNR and GEM can be safely given together without substantial reductions in their individual dose intensities. In our opinion, the dose level of GEM 1,000 mg/m² + VNR 25 mg/m² given in combination with CDDP 50 mg/m² on days 1 and 8 of a three-week cycle can be recommended for phase II trials, since it provides a better balance in dose intensity of GEM and VNR. A phase II randomised study is underway to establish the activity of this new regimen (at the above-cited dose level) in chemo-naïve NSCLC patients.     

SU11274逆转肝细胞生长因子诱导不同EGFR基因型非小细胞肺癌细胞株对吉非替尼耐药

背景与目的：肝细胞生长因子(hepatocyte growth factor,HGF)诱导敏感非小细胞肺癌(nonsmall cell lung cancer,NSCLC)细胞对表皮生长因子受体酪氨酸激酶抑制剂(epidermal growth factor receptor-tyrosine kinase inhibitor,EGFR-TKI)耐药,其机制与c-Met激活有关。本研究探讨c-Met抑制剂SU11274逆转HGF诱导的不同EGFR基因型NSCLC细胞株对吉非替尼耐药及逆转耐药机制。方法：选择人NSCLC细胞株PC9(EGFR突变型)、H292(EGFR野生型)和A549(EGFR野生型),应用吉非替尼和SU11274单独或联合作用于HGF诱导的细胞株。实验分为6组：C组(不加药对照组)、H组(HGF处理组)、G组(吉非替尼处理组)、S(SU11274处理组)、HG组(HGF+吉非替尼处理组)和HGS组(HGF+吉非替尼+SU11274处理组)。MTT法检测对细胞增殖的影响,流式细胞术检测细胞凋亡的影响;应用蛋白质印迹法(Western blot)检测细胞中c-Met及其下游通道Stat3、Akt和Erk1/2蛋白表达水平。结果：吉非替尼对3种细胞的生长抑制作用均呈浓度依赖性,HGF处理能够缓解吉非替尼的增殖抑制作用(P<0.05);不同浓度吉非替尼联合SU11274作用于HGF诱导细胞时,3种细胞株存活率比吉非替尼单独作用于HGF诱导细胞时明显降低(P<0.05);HGS组的细胞凋亡比HG组明显增加(P<0.05);HGS组的c-Met、Stat3、Akt和Erk1/2活化蛋白量比HG组明显减少。结论：c-Met抑制剂SU11274可逆转HGF诱导的不同EGFR基因型NSCLC细胞株对吉非替尼耐药,其机制可能与抑制HGF活化的c-Met及其下游通道蛋白表达有关。     

Role of survivin in EGFR inhibitor-induced apoptosis in non-small cell lung cancers positive for EGFR mutations

The molecular mechanism by which epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKI) induce apoptosis in non-small cell-lung cancer (NSCLC) cells that are positive for activating mutations of the EGFR remains unclear. In this study, we report the effects of the EGFR-TKI gefitinib on expression of the antiapoptotic protein survivin that have functional consequences in EGFR mutation-positive NSCLC cells. Immunoblot analysis revealed that gefitinib downregulated survivin expression, likely through inhibition of the PI3K-AKT signaling pathway, in NSCLC cells positive for EGFR mutation. Stable overexpression of survivin attenuated gefitinib-induced apoptosis and also inhibited the antitumor effect of gefitinib in human tumor xenografts. Furthermore, the combination of survivin overexpression with inhibition of the gefitinib-induced upregulation of the proapoptotic protein BIM attenuated gefitinib-induced apoptosis to a greater extent than either approach alone. Our results indicate that downregulation of survivin plays a pivotal role in gefitinib-induced apoptosis in EGFR mutation-positive NSCLC cells. Furthermore, they suggest that simultaneous interruption of the PI3K-AKT-survivin and MEK-ERK-BIM signaling pathways is responsible for EGFR-TKI-induced apoptotic death in these cells.     

Gemcitabine and vinorelbine followed by docetaxel in patients with advanced non-small-cell lung cancer: a multi-institutional phase II trial of nonplatinum sequential triplet combination chemotherapy (JMTO LC00-02)

To evaluate the efficacy and toxicity of the sequential nonplatinum combination chemotherapy consisting of gemcitabine (GEM) and vinorelbine (VNR) followed by docetaxel (DOC) in patients with advanced non-small-cell lung cancer (NSCLC), we conducted the multiinstitutional phase II study. A total of 44 chemotherapy-naive patients with advanced NSCLC were treated with GEM 1000 mg m(-2) and VNR 25 mg m(-2) intravenously on days 1 and 8 every 3 weeks for three cycles. DOC 60 mg m(-2) was then administrated intravenously at 3-week intervals for three cycles. Patients were evaluated for response and toxicity with each cycle of the treatment. The major objective response rate was 47.7% (95% confidence interval (CI), 33.8-62.1%). Median survival time (MST) was 15.7 months and 1-year survival rate was 59%. In the GEM/VNR cycle, grade 3/4 neutropenia occurred in 36.3%, grade 3/4 anaemia in two patients (4.5%) and grade 3 thrombocytopenia in one patient (2.3%). Grade 3 pneumonitis occurred in two patients (4.5%) in GEM/VNR cycles. In the DOC cycles, grade 3/4 neutropenia occurred in 39.4% but no patient experienced grade 3/4 anaemia or thrombocytopenia. Of the 44 eligible patients, 33 patients completed three cycles of GEM/VNR and 22 patients completed six cycles of planned chemotherapy (three cycles of GEM/VNR followed by three cycles of DOC). The sequential triplet nonplatinum chemotherapy consisted of GEM/VNR followed by DOC, and was very active and well tolerated. This study forms the basis for an ongoing phase III trial that compares this nonplatinum triplet and standard platinum doublet combination (carboplatin/paclitaxel).     

Response to dual blockade of epidermal growth factor receptor (EGFR) and cycloxygenase-2 in nonsmall cell lung cancer may be dependent on the EGFR mutational status of the tumor

BACKGROUND: Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) have demonstrated clinical benefit in patients with nonsmall cell lung cancer (NSCLC), particularly those with tumors that have EGFR-TK domain mutations. Moreover, the EGFR and cyclooxygenase (COX)-2 pathways are known to enhance the procarcinogenic effects of each other in different tumor types. Therefore, it was hypothesized that tumor EGFR mutation status may influence the effectiveness of simultaneous EGFR and COX-2 inhibition in patients with NSCLC. METHODS: Three NSCLC cell lines with varying 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, or celecoxib alone, and the combination of both EGFR-TKI inhibitors with celecoxib. Cell survival and apoptosis was assessed and correlated with the expression of COX-2, EGFR, pEGFR, Akt, pAkt, expression, and derived prostaglandin E2 (PGE(2)). RESULTS: Celecoxib by itself was found to have no effects on cell growth or apoptosis in any of the cell lines. Erlotinib and gefitinib inhibited cell growth and induced apoptosis in both mutant cell lines and did so in H1781 cells at 10-fold higher concentrations. Celecoxib when added to erlotinib or gefitinib significantly enhanced the antiproliferative and proapoptotic effects in both mutant cell lines but had no additional effects in H1781 cells. Greater down-regulation of COX-2, EGFR, pEGFR, Akt, pAkt, and PGE(2) was found when H3255 cells were treated with the combination compared with any of the single agents alone. CONCLUSIONS: The results of the current study demonstrate that the effectiveness of the addition of celecoxib to an EGFR-TKI is significantly greater in NSCLC cells with EGFR mutations, which is likely due to more complete inhibition of both pathways.     

Activated Src and Ras induce gefitinib resistance by activation of signaling pathways downstream of epidermal growth factor receptor in human gallbladder adenocarcinoma cells

Purpose: Although gefitinib, a selective inhibitor of epidermal growth factor receptor (EGFR) tyrosine kinase, has been demonstrated to exhibit its antitumor activity by the blockade of EGF receptor, the role of signaling pathways downstream of EGFR in gefitinib sensitivity remains unknown. In this study, we investigated the mechanistic role of Src and Ras, major oncogene products implicated in the pathogenesis of many human cancers in gefitinib sensitivity. Methods: Using parental and v-src- or c-H-ras-transfected HAG-1 human gallbladder adenocarcinoma cell lines, effects of gefitinib on cytotoxicity, cell cycle purtubation and apoptosis, and tyrosine phosphorylation of EGFR, Akt, and Erk were determined by WST-1 assay, flow cytometry, and Western blots, respectively. Results: Activated Ras and Src conferred a strong resistance to gefitinib by nearly 30-fold and 200-fold, respectively. Gefitinib induced accumulation of cells in the G0/G1 phase of the cell cycle at 24-h, with progressive expansion of apoptotic cell population in parental HAG-1 cells, but these effects were completely abolished in v-src- or c-H-ras-transfected cell line. Upon gefitinib treatment, EGFR activation and subsequent downstream activation through Erk and Akt were significantly inhibited in HAG-1 cells. By contrast, gefinitib failed to inhibit the activation of both Akt and Erk in v-src-transfected cells and Erk, but not Akt in c-H-ras-transfected cells, despite the blockade of EGFR activation in these respective cell lines. Treatment of v-src-transfected cells with herbimycin A, a Src tyrosine kinase inhibitor, partially reversed the gefitinib resistance, with concomitant inhibition of Akt and Erk. Conclusion: Our results suggest that activated Ras and Src could induce gefitinib resistance by activating either or both of Akt and Erk signaling pathways, thus providing a strategic rationale for assessment of these specific signaling molecules downstream of EGFR to customize treatment.Baoli Qin and Hiroshi Ariyama contributed equally to this work.     

Triplet chemotherapy with cisplatin, gemcitabine and vinorelbine for malignant pleural mesothelioma

BACKGROUND: The incidence of malignant pleural mesothelioma (MPM) is expected to increase due to delayed control of occupational exposure to asbestos in Japan. We investigated the use of triplet combination chemotherapy with cisplatin (CDDP), gemcitabine (GEM) and vinorelbine (VNR) for the treatment of Japanese patients with MPM. METHODS: From December 2000 to August 2003, 12 patients received the following regimen: CDDP 40 mg/m(2), GEM 800 mg/m(2) and VNR 20 mg/m(2) on days 1 and 8 every 4 weeks. Among the 12 patients, six selected patients underwent an extrapleural pneumonectomy (EP) after a median of three cycles of triplet chemotherapy. RESULTS: The overall response rate for all patients and the response rate for chemotherapy-naive cases were 58 and 67%, respectively. The median survival time and survival rate at 2 years for all patients were 11 months and 50%, respectively. The 2-year survival rates for the patients with and without EP were 83.3 and 16.7%, respectively. CONCLUSIONS: Triplet chemotherapy with CDDP, GEM and VNR was thus found to be highly effective for patients with MPM and its toxicity was manageable. A multi-institutional phase II trial is now being planned to establish the effectiveness of this new regimen in chemotherapy-naive patients with MPM.     

A phase I pharmacokinetic and pharmacodynamic study of intravenous calcitriol in combination with oral gefitinib in patients with advanced solid tumors.

PURPOSE: In preclinical models, calcitriol and the tyrosine kinase inhibitor gefitinib are synergistic and modulate extracellular signal-regulated kinase (Erk) and Akt pathways. Therefore, we conducted a phase I study of calcitriol and gefitinib to determine the maximum tolerated dose (MTD) of this combination. EXPERIMENTAL DESIGN: Calcitriol was given i.v. over 1 h on weeks 1, 3, and weekly thereafter. Gefitinib was given at a fixed oral daily dose of 250 mg starting at week 2 (day 8). Escalation occurred in cohorts of three patients until the MTD was defined. Pharmacokinetic studies were done for calcitriol and gefitinib. Serial skin biopsies were done to investigate epidermal growth factor receptor (EGFR) pathway pharmacodynamic interactions. RESULTS: Thirty-two patients were treated. Dose-limiting hypercalcemia was noted in two of four patients receiving 96 mug/wk of calcitriol. One of seven patients developed dose-limiting hypercalcemia at the MTD 74 mug/wk calcitriol dose level. The relationship between calcitriol dose and peak serum calcitriol (C(max)) and systemic exposure (AUC) was linear. Mean (+/-SD) serum calcitriol C(max) at the MTD was 6.68 +/- 1.42 ng/mL. Gefitinib treatment inhibited EGFR, Akt, and Erk phosphorylation in the skin. Calcitriol did not have consistent effects on skin EGFR or its downstream elements. The combination of gefitinib and calcitriol did not modulate tumor EGFR pathway in patients with serial tumor biopsies. CONCLUSIONS: High doses of weekly i.v. calcitriol can be administered safely in combination with gefitinib. Calcitriol concentrations achieved at the MTD 74 mug calcitriol exceed in vivo concentrations associated with antitumor activity in preclinical models.     

Antitumor effect of gefitinib on head and neck squamous cell carcinoma enhanced by trastuzumab

The overexpression of EGFR and/or HER-2 is associated with tumor cell resistance to chemotherapy, radiotherapy, disease progression and poor prognosis in patients with a variety of malignant tumors. Treatment combining the EGFR-targeting drug, gefitinib (ZD1839, Iressa) with the HER-2-targeting drug, trastuzumab (Herceptin) has been reported to improve therapeutic efficacy in patients with breast cancer. The purpose of this study was to examine the antitumor effect of this combination on head and neck squamous cell carcinoma (HNSCC) in vitro. Cell proliferation was inhibited significantly in two cell lines. Although IC50 of gefitinib alone against some cell lines was not reached, it was achieved after being combined with trastuzumab. Furthermore, IC50 was lower for the combination than for gefitinib alone in several cell lines. These results suggest that the combination may improve efficacy against HNSCC.     

Scheduling of paclitaxel and gefitinib to inhibit repopulation for optimal treatment of human cancer cells and xenografts that overexpress the epidermal growth factor receptor

Purpose

In clinical studies, evaluating the combination of chemotherapy and the epidermal growth factor receptor (EGFR) inhibitor gefitinib, treatments were administered concurrently, despite it being counter-intuitive to give a cytostatic agent concurrent with cycle-active chemotherapy. One strategy to enhance efficacy might be to give the agents sequentially, thus allowing selective inhibition of repopulation of cancer cells between doses of chemotherapy. Here, we evaluate the hypothesis that sequential administration might allow inhibition of repopulation by gefitinib, with tumor cells re-entering cycle to allow sensitivity to subsequent chemotherapy.

Methods

Sequential and concurrent administration of paclitaxel and gefitinib were studied in vitro and in xenografts using EGFR over-expressing, EGFR-mutant, and EGFR wild-type human cancer cell lines. We evaluated cell cycle distribution and repopulation during treatment.

Results

The sequential use of gefitinib and paclitaxel to treat EGFR over-expressing A431 cells in vitro decreased repopulation compared to chemotherapy alone, and there was greater cell kill compared to concurrent treatment. In contrast, combined treatment led to greater growth delay than use of gefitinib alone for concurrent but not for sequential treatment of mice bearing A431 xenografts; concurrent treatment had greater effects to reduce functional vasculature in the tumors. Conversely, sequential treatment led to greater growth delay than concurrent treatment of EGFR-mutant HCC-827 xenografts that are sensitive to lower doses of gefitinib.

Conclusions

These studies highlight the importance of considering effects on the cell cycle, and on the solid tumor microenvironment, including tumor vasculature, when scheduling cytostatic and cytotoxic agents in combination.     

Reduction of PTEN protein and loss of epidermal growth factor receptor gene mutation in lung cancer with natural resistance to gefitinib (IRESSA)

Gefitinib (IRESSA), an epidermal growth factor receptor (EGFR) tyrosine kinase (TK) inhibitor, has antitumour activity in the advanced non-small-cell lung cancer (NSCLC) setting. However, in chemotherapy-naïve patients with advanced NSCLC, the addition of gefitinib to standard chemotherapy regimens failed to increase survival. These results suggest the need for improved patient selection and combination rationales for targeted therapies. We have identified subpopulations of an adenocarcinoma cell line that are naturally resistant to gefitinib, and have analysed the cDNA expression profiles, genomic status of EGFR gene and the effect of gefitinib on signalling pathways in these cell lines in order to identify key mechanisms for naturally acquired resistance to gefitinib. Gefitinib-resistant subpopulations demonstrated increased Akt phosphorylation (not inhibited by gefitinib), reduced PTEN protein expression and loss of the EGFR gene mutation when compared with parental cell lines. These differences in Akt and PTEN protein expression were not evident from the cDNA array profiles. These data suggests that (1) the EGFR gene mutation may be possibly lost in some cancer cells with other additional mechanisms for activating Akt, (2) reintroduction of PTEN or pharmacological downregulation of the constitutive PI3K–Akt-pathway activity may be an attractive therapeutic strategy in cancers with gefitinib resistance.     

5-aza-CdR增强吉非替尼对人非小细胞肺癌细胞株H1650敏感性机制的研究

目的:探讨EGFR基因启动子甲基化水平与人非小细胞肺癌细胞株H1650对吉非替尼敏感性之间的关系。方法:5-aza-CdR和吉非替尼单独或联合用药作用于H1650细胞株后,应用甲基化特异性PCR法检测EGFR基因启动子区甲基化状态;CCK-8法检测细胞增殖率;流式细胞仪技术检测细胞凋亡率变化;蛋白质印迹法和实时荧光定量PCR法检测EGFR蛋白和mRNA的表达情况。结果:5-aza-CdR可去除H1650细胞EGFR基因启动子区甲基化;CCK-8法检测结果显示,H1650对吉非替尼的敏感性较差,5-aza-CdR去甲基化后联合运用吉非替尼处理72h,联合用药组IC50为(2.93±0.95)μmol/L,与吉非替尼组(14.53±1.13)μmol/L、5-aza-CdR组(4.91±1.42)μmol/L比较显著降低,P<0.05;流式细胞仪技术结果显示,联合用药组细胞凋亡率为(83.62±4.3)%,与吉非替尼组(20.29±2.9)%、5-aza-CdR组(25.73±7.5)%比较,差异有统计学意义,P<0.05;蛋白质印迹法和实时荧光定量PCR法结果显示,吉非替尼与5-aza-CdR联合用药干预72h后细胞EGFR蛋白和mRNA表达显著下降,与单药组相比,具有统计学意义,P<0.05。结论:EGFR基因启动子区甲基化可能是非小细胞肺癌细胞株H1650对吉非替尼获得性耐药的机制之一。     

Anti-tumor activity of a novel EGFR tyrosine kinase inhibitor against human NSCLC in vitro and in vivo

Epidermal growth factor receptor (EGFR) is highly expressed in many human tumors including non-small cell lung cancer (NSCLC). Treatment with epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) has led to dramatic clinical improvement in selected patients with NSCLC. However, intrinsic and acquired resistance to EGFR-TKI remains a common phenomenon. Novel EGFR-TKI, structurally different with erlotinib or gefitinib might be beneficial for patients with NSCLC. In this study, we examined the anti-tumor effect of a newly synthesized novel EGFR tyrosine kinase inhibitor N-(3-chloro-4-fluorophenyl)-N-(7-methoxy-6-(3-morpholinopropoxy) quinazolin-4-yl)-3,3-dimethylbutanamide (F90). In vitro studies in a panel of three different human NSCLC cell lines revealed that F90 inhibited cell proliferation with high potency and induced G0/G1 arrest of cell cycle and apoptosis. F90 markedly reduced phosphorylation of EGFR and inhibited activation of MAPK and Akt. Oral administration of F90 (80 mg/kg/day) to BALB/c nude mice bearing NSCLC cell lines xenografts significantly retarded tumor growth. In conclusion, F90 has potent anti-tumor activity on human lung cancer in vitro and in vivo.     

Enhancement of tumor radioresponse by combined treatment with gefitinib (Iressa, ZD1839), an epidermal growth factor receptor tyrosine kinase inhibitor, is accompanied by inhibition of DNA damage repair and cell growth in oral cancer

Molecular blockade of EGFR with either an EGFR MAb or an EGFR TKI enhances the radiosensitivity of human SCCs. In the present study, we investigated whether treatment with the EGFR TKI gefitinib (Iressa, ZD1839) improves the response to radiotherapy in the OSCC cell lines HSC2 and HSC3. We examined potential mechanisms that may contribute to the enhanced radiation response induced by gefitinib. Growth inhibition was observed in vitro with radiation or gefitinib. A cooperative antiproliferative effect was obtained when cancer cells were treated with radiation followed by gefitinib. Cells treated with a combination of radiation and gefitinib arrested in G(1) and G(2)-M phases, with a decrease in the S-phase population. While radiation alone did not significantly affect MEK1/2 and p38 MAPK autophosphorylation, the combination of gefitinib and radiation completely inhibited the downstream signaling of EGFR. Results from DNA damage repair analysis in cultured OSCC cells demonstrated that gefitinib had a strong inhibitory effect on DNA-PKc pathways after radiation. Tumor xenograft studies demonstrated that the combination of gefitinib and radiation caused growth inhibition and tumor regression of well-established OSCC tumors in athymic mice; tumor volume was reduced from 1,008.2 to 231.4 mm(3) in HSC2 cells (p < 0.01) and from 284.2 to 12.4 mm(3) in HSC3 cells (p < 0.01). Immunohistochemical analysis of OSCC xenografts revealed that gefitinib caused a striking decrease in tumor cell proliferation when combined with radiotherapy. Overall, we conclude that gefitinib enhances tumor radioresponse by multiple mechanisms that may involve antiproliferative growth inhibition and effects on DNA repair after exposure to radiation.