肺癌表皮生长因子受体酪氨酸激酶抑制剂获得性耐药的逆转

以表皮生长因子受体（EGFR）为靶点治疗非小细胞肺癌是治疗肺癌的前沿手段,其产生的获得性耐药限制了靶向药物的发展。目前已有大量的有关EGFR突变耐药的数据,利用这些数据,人们正在探讨克服EGFR靶向治疗耐药的3个基本方法：强化EGFR的抑制、EGFR抑制剂与其他靶向治疗相结合以及通过替代途径改变抗癌治疗方法。     

培美曲塞单药或联合吉非替尼治疗EGFR-TKI耐药后晚期非小细胞肺癌临床观察

背景与目的:生长因子受体-酪氨酸激酶抑制剂(epidermal growth factor receptor-tyrosine kinase inhibitor,EGFR-TKI)治疗晚期非小细胞肺癌(non-small cell lung cancer,NSCLC)获得性耐药后尚无标准的治疗方案,亟待探寻有效的后续治疗方法.为临床应用提供指导,该研究旨在比较后续治疗采用培美曲塞单药或联合吉非替尼治疗EGFR-TKI获得性耐药的晚期NSCLC的临床疗效及安全性.方法:入组既往接受过EGFR-TKI治疗后进展的晚期NSCLC患者62例.其中32接受培美曲塞联合吉非替尼治疗,设为联合组;30例单用培美曲塞治疗,设为化疗组.评价临床疗效及不良反应.结果:联合组客观有效率(objective response rate,ORR)为46.9%,高于化疗组的20%,差异有统计学意义(χ2=4.933,P<0.05);两组疾病控制率(disease control rate,DCR)差异无统计学意义(P>0.05);联合组的中位无病生存期(progression-free survival,PFS)为8.0个月,化疗组中位PFS为6.3个月,差异有统计学意义(χ2=8.063,P<0.05),两组总生存期(overall survival,OS)差异无统计学意义(P>0.05).联合组中性粒细胞减少、皮疹的发生率高于化疗组,差异有统计学意义(P<0.05),Ⅲ~Ⅳ不良反应两组差异无统计学意义(P>0.05).结论:晚期NSCLC患者EGFR-TKI获得性耐药后,采用培美曲塞联合吉非替尼较单用培美曲塞显示出更优势临床有效率和中位PFS,不良反应可耐受,值得临床推广运用.     

Overcoming resistance to EGFR tyrosine kinase inhibitors in lung cancer,focusing on non-T790M mechanisms

Introduction: despite initial dramatic efficacy of EGFR tyrosine kinase inhibitors (TKIs) in EGFR-mutant lung cancer patients, emergence of acquired resistance is almost inevitable. The EGFR T790M secondary mutation that accounts for ~50% of resistance is now treatable with osimertinib. However, for the remaining 50% of patients who develop resistance mechanisms other than T790M mutation, cytotoxic chemotherapies are still the standard of care and novel treatment strategies are urgently needed.

Areas covered: In this review, we discuss current experimental and clinical evidence to develop better treatment strategies to overcome or prevent acquired resistance to EGFR-TKIs in lung cancers, focusing on non-T790M mechanisms.

Expert commentary: There are numerous non-T790M resistant mechanisms to EGFR-TKIs, and therefore, strategies that can be applied to many of these resistance mechanisms may be reasonable and useful in clinical practice. Although the combination of cytotoxic chemotherapy plus an EGFR-TKI has proved to be detrimental following front-line EGFR-TKI treatment failure, promising experimental and/or early clinical data have been reported for the combination of bevacizumab or anti-EGFR monoclonal antibody plus EGFR-TKIs. Upfront polytherapy, which co-targets potential resistance mechanisms or other important signaling for EGFR-mutant lung cancer cells, is also a promising strategy.     

Continuation of epidermal growth factor receptor tyrosine kinase inhibitor treatment prolongs disease control in non-small-cell lung cancers with acquired resistance to EGFR tyrosine kinase inhibitors

Objectives

Patients with non-small-cell lung cancer (NSCLC) develop acquired resistance to epidermal growth factor receptor tyrosine kinase inhibitors (EGFR TKIs) after tumor regression. No approved targeted therapies are currently available after initial EGFR TKI treatment. This study investigated the efficacy of continuing EGFR TKI therapy with local treatments for patients with NSCLC and local progression or minimal/slow progression on TKI therapy.

Materials and Methods

Fifty-five patients with NSCLC treated with EGFR TKIs and developed acquired resistance to the drug were included. Initial response to target therapy, median progression free survival (PFS1), progression pattern, and first progression site were assessed. Median progression free survival to physician assessment progression (PFS2) and difference between PFS1 and PFS2 (PFS difference) were also recorded.

Results and Conclusion

PFS1 was 11.2 months, PFS2 was 20.3 months, and PFS difference was 8.3 months. Nineteen patients (34.5%) who manifested progression received local therapy, and 16 (28.6%) underwent rebiopsy after progression with six positive EGFR T790M mutations detected. Cox proportional hazards regression model showed that only the first line of treatment was significantly correlated with PFS difference. NSCLC patients with acquired resistance to EGFR TKIs could benefit from the same TKI therapy through months to years of disease control.     

Strategies for overcoming resistance to EGFR family tyrosine kinase inhibitors

The first-generation epidermal growth factor receptor tyrosine kinase inhibitors erlotinib and gefitinib have been incorporated into treatment paradigms for patients with advanced non-small cell lung cancer. These agents are particularly effective in a subset of patients whose tumors harbor activating epidermal growth factor receptor mutations. However, most patients do not respond to these tyrosine kinase inhibitors, and those who do will eventually acquire resistance that typically results from a secondary epidermal growth factor receptor mutation (e.g., T790M), mesenchymal-epithelial transition factor amplification, or activation of other signaling pathways. For patients whose tumors have wild-type epidermal growth factor receptor, there are several known mechanisms of initial resistance (e.g., Kirsten rat sarcoma viral oncogene homolog mutations) but these do not account for all cases, suggesting that unknown mechanisms also contribute. To potentially overcome the issue of resistance, next-generation tyrosine kinase inhibitors are being developed, which irreversibly block multiple epidermal growth factor receptor family members (e.g., afatinib [BIBW 2992] and PF-00299804) and/or vascular endothelial growth factor receptor pathways (e.g., BMS-690514 and XL647). In addition, drugs that block parallel signaling pathways or signaling molecules downstream of the epidermal growth factor receptor, such as the insulin-like growth factor-1 receptor and the mammalian target of rapamycin, are undergoing clinical evaluation. As drug resistance appears to be pleomorphic, combinations of drugs or drugs with multiple targets may be more effective in circumventing resistance.     

Mechanisms of acquired resistance to epidermal growth factor receptor tyrosine kinase inhibitors in non-small cell lung cancer.

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors gefitinib and erlotinib are effective therapies for non-small cell lung cancer patients whose tumors harbor somatic mutations in EGFR. All patients, however, ultimately develop resistance to these agents. Thus, there is a great need to understand how patients become resistant to develop effective therapies for these cancers. Studies over the last few years have identified two different EGFR tyrosine kinase inhibitor resistance mechanisms, a secondary mutation in EGFR, EGFR 790M, and amplification of the MET oncogene. These findings have led to clinical trials using newly designed targeted therapies that can overcome these resistance mechanisms and have shown promise in laboratory studies. Ongoing research efforts will likely continue to identify additional resistance mechanisms, and these findings will hopefully translate into effective therapies for non-small cell lung cancer patients.     

Clinical implications of T790M mutation in patients with acquired resistance to EGFR tyrosine kinase inhibitors

Objectives

Although T790M mutation is considered to be the major mechanism of acquired resistance to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) in patients with non-small cell lung cancer (NSCLC), its clinical implication remains undetermined.

Methods

Post-progression tumor specimens were prospectively collected for T790M mutation analysis in NSCLC patients with acquired resistance to initial EGFR TKIs. Clinical features were compared between patients with and without T790M.

Results

Out of 70 cases, 36 (51%) were identified to have T790M mutation in the rebiopsy specimen. There was no difference in the pattern of disease progression, progression-free survival for initial TKIs (12.8 and 11.3 months), post-progression survival (14.7 and 14.1 months), or overall survival (43.5 and 36.8 months) in patients with and without T790M. In total, 34 patients received afatinib after post-progression biopsy as a subsequent treatment, and the response rate was 18%. The median progression-free survival for afatinib was 3.7 months for the entire group, and 3.2 and 4.6 months for the groups with and without T790M, respectively (P = 0.33).

Conclusions

The identification of T790M as acquired resistance mechanism was clinically feasible. Although T790M had no prognostic or predictive role in the present study, further research is necessary to identify patients with T790M-mutant tumors who might benefit from newly developed T790M-specific TKIs.     

Management of tyrosine kinase inhibitor resistance in lung cancer with EGFR mutation

The identification of driver mutations and drugs that inhibit their activity has been a major therapeutic advance for patients with advanced lung adenocarcinoma. Unfortunately, the success of these drugs is limited by the universal development of resistance. Treatment failure can result from inadequate drug exposure or selection of resistant malignant clones. Clinically distinct mechanisms of disease progression have been identified and can inform treatment decisions. Investigations into the biochemical mechanisms of tyrosine kinase inhibitor resistance may provide additional therapeutic targets by which the efficacy of targeted therapy can be improved.     

The small GTPase ADP-Ribosylation Factor 1 mediates the sensitivity of triple negative breast cancer cells to EGFR tyrosine kinase inhibitors

The clinical use of EGFR-targeted therapy, in triple negative breast cancer patients, has been limited by the development of resistance to these drugs. Although activated signaling molecules contribute to this process, the molecular mechanisms remain relatively unknown. We have previously reported that the small GTPase ADP-Ribosylation Factor 1 (ARF1) is highly expressed in invasive breast cancer cells and acts as a molecular switch to activate EGF-mediated responses. In this study, we aimed at defining whether the high expression of ARF1 limits sensitivity of these tumor cells to EGFR inhibitors, such as gefitinib. Here, we show that the knock down of ARF1 expression or activity decreased the dose and latency time required by tyrosine kinase inhibitors to induce cell death. This may be explained by the observation that the depletion of ARF1 suppressed gefitinib-mediated activation of key mediators of survival such as ERK1/2, AKT and Src, while enhancing cascades leading to apoptosis such as the p38MAPK and JNK pathways, modifying the Bax/Bcl2 ratio and cytochrome c release. In addition, inhibiting ARF1 expression and activation also results in an increase in gefitinib-mediated EGFR internalization and degradation further limiting the ability of this receptor to promote its effects. Interestingly, we observed that gefitinib treatment resulted in the enhanced activation of ARF1 by promoting its recruitment to the receptor AXL, an important mediator of EGFR inhibition suggesting that ARF1 may promote its pro-survival effects by coupling to alternative mitogenic receptors in conditions where the EGFR is inhibited. Together our results uncover a new role for ARF1 in mediating the sensitivity to EGFR inhibition and thus suggest that limiting the activation of this GTPase could improve the therapeutic efficacy of EGFR inhibitors.     

ALDH-positive lung cancer stem cells confer resistance to epidermal growth factor receptor tyrosine kinase inhibitors

Molecular targeting therapeutics, such as EGFR tyrosine kinase inhibitors (TKIs), are important treatment strategies for lung cancer. Currently, the major challenge confronting targeted cancer therapies is the development of resistance. Cancer stem cells (CSCs) represent a rare population of undifferentiated tumorigenic cells responsible for tumor initiation, maintenance and spreading. Resistance to conventional chemotherapeutic drugs is a common characteristic of CSCs. However, the issue of whether CSCs contribute to EGFR TKI resistance in lung cancer is yet to be established. In the current study, we explored the association of ALDH1A1 expression with EGFR TKI resistance in lung cancer stem cells. ALDH1A1-positive lung cancer cells displayed resistance to gefitinib, compared to ALDH1A1-negative lung cancer cells. Moreover, PC9/gef cells (gefitinib-resistant lung cancer cells) presented a higher proportion of ALDH1A1-positive cells, compared to PC9 cells (gefitinib-sensitive lung cancer cells). Clinical sample studies were consistent with results from cell culture model systems showing that lung cancer cells with resistance to EGFR TKI and chemotherapy drugs contain significantly increased proportions of ALDH1A1-positive cells. These findings collectively suggest that ALDH1A1 positivity in cancer stem cells confers resistance to EGFR TKI in lung cancer.     

Differential sensitivity of glioma- versus lung cancer-specific EGFR mutations to EGFR kinase inhibitors

Activation of the epidermal growth factor receptor (EGFR) in glioblastoma (GBM) occurs through mutations or deletions in the extracellular (EC) domain. Unlike lung cancers with EGFR kinase domain (KD) mutations, GBMs respond poorly to the EGFR inhibitor erlotinib. Using RNAi, we show that GBM cells carrying EGFR EC mutations display EGFR addiction. In contrast to KD mutants found in lung cancer, glioma-specific EGFR EC mutants are poorly inhibited by EGFR inhibitors that target the active kinase conformation (e.g., erlotinib). Inhibitors that bind to the inactive EGFR conformation, however, potently inhibit EGFR EC mutants and induce cell death in EGFR-mutant GBM cells. Our results provide first evidence for single kinase addiction in GBM and suggest that the disappointing clinical activity of first-generation EGFR inhibitors in GBM versus lung cancer may be attributed to the different conformational requirements of mutant EGFR in these 2 cancer types. SIGNIFICANCE: Approximately 40% of human glioblastomas harbor oncogenic EGFR alterations, but attempts to therapeutically target EGFR with first-generation EGFR kinase inhibitors have failed. Here, we demonstrate selective sensitivity of glioma-specific EGFR mutants to ATP-site competitive EGFR kinase inhibitors that target the inactive conformation of the catalytic domain.     

Breast cancer cells with acquired resistance to the EGFR tyrosine kinase inhibitor gefitinib show persistent activation of MAPK signaling

Although the epidermal growth factor receptor (EGFR) is frequently expressed in human primary breast carcinoma, the majority of breast cancer patients do not respond to treatment with EGFR tyrosine-kinase inhibitors such as gefitinib. We isolated through a stepwise dose escalation of the drug two gefitinib-resistant SK-Br-3 clones, ZD6 and ZD10 (ZD) cells, which showed, respectively, a three- to five-fold increase in the IC₅₀ for gefitinib as compared with parental cells. The levels of expression of EGFR were increased in ZD cells as compared with wild-type SK-Br-3 cells. The phosphorylation of EGFR, ErbB-2, ErbB-3 and Akt was significantly reduced in gefitinib-resistant cells. In contrast, ZD cells showed levels of MAPK phosphorylation similar to untreated wild-type cells when cultured in presence of gefitinib. Persistent activation of MAPK was also observed in gefitinib-resistant clones isolated from MDA-MB-175 and MDA-MB-361 breast cancer cell lines. ZD cells showed an increased sensitivity to the MEK inhibitor PD98059 as compared with SK-Br-3 cells, and a synergistic anti-tumor effect was observed when ZD cells were treated with a combination of gefitinib and PD98059. Overexpression of a constitutively activated form of p42-MAPK in SK-Br-3 cells resulted in an approximately 50% increase in the IC₅₀ to gefitinib. Finally, culture of ZD10 resistant cells in absence of gefitinib led to reversion of the resistant phenotype. These observations suggest that MAPK signaling might play a role in the resistance that develops in breast cancer cells after long-term exposure to gefitinib. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Survival and prognosis analyses of concurrent PIK3CA mutations in EGFR mutant non-small cell lung cancer treated with EGFR tyrosine kinase inhibitors

In non-small cell lung cancer (NSCLC) patients with epidermal growth factor receptor (EGFR) mutation, the prognostic impact of a concurrent Phosphoinositide-3-kinase catalytic alpha polypeptide (PIK3CA) mutation was still unknown. Some studies have shown that EGFR mutant NSCLC patients treated with EGFR tyrosine kinase inhibitors (TKIs) when concurrent PIK3CA mutation have a worse prognosis and shorter survival time. This study conducted a retrospective analysis of NSCLC patients with EGFR mutant or concurrent PIK3CA mutations from January 2015 to October 2019 in the First Affiliated Hospital of Nanchang University. Relative to EGFR alone mutations (Single-Mt), we found that NSCLC patients with EGFR mutations coexisting with PIK3CA mutations (Double-Mt) treated with EGFR-TKIs had a shorter median time to progression (TTP): 7.8 months versus 10.9 months (Double-Mt versus Single-Mt, P = 0.001), and decrease in median overall survival (OS): 20.6 months versus 32.4 months (P < 0.001). The objective response rate (ORR) between Double-Mt and Single-Mt was 36.7% versus 61.9% (P = 0.044), disease control rates (DCR) was 80.1% versus 91.7% (P = 0.179). Obviously, EGFR-TKIs for EGFR mutate NSCLC patients when concurrent PIK3CA mutations have a worse prognosis and shorter survival time.     

TP53突变对非小细胞肺癌表皮生长因子受体突变患者酪氨酸激酶抑制剂的治疗效果和预后影响

基因突变能够影响肺癌细胞对靶向药物的敏感性,导致个体化临床治疗效果出现差异。表皮生长因子受体(EGFR)的突变状态在内科药物治疗决策中具有重要意义。此外,其他并存的基因突变均可影响疾病的治疗效果和患者的远期临床预后。EGFR突变合并TP53突变是否可改变肺癌细胞对酪氨酸激酶抑制剂治疗的敏感性和对远期预后的影响一直受到人们的关注。目前在临床实践中,TP53的突变状态并不是临床治疗决策中的参考依据,因此需要进一步的证据阐明TP53(包括各亚型)突变状态对EGFR靶向治疗潜在获益的影响,以指导非小细胞肺癌的治疗。     

Transformation to small-cell lung cancer following treatment with EGFR tyrosine kinase inhibitors in a patient with lung adenocarcinoma

We report the case of a 52-year-old woman with lung adenocarcinoma treated with EGFR tyrosine kinase inhibitor (TKI) therapy. After disease progression, histological examination of a secondary biopsy specimen revealed small-cell lung cancer (SCLC) that was sensitive to standard SCLC treatment. Tumor markers, including ProGRP and NSE, were elevated. Transformation to SCLC is a mechanism for acquired resistance to EGFR-TKI therapy. Secondary biopsy is important for evaluation of genetic and histological changes and selection of appropriate treatment. Furthermore, ProGRP and NSE may be useful for early detection of SCLC transformation in cases resistant to EGFR-TKI therapy.