Molecular Mechanisms of Resistance to Therapies Targeting the Epidermal Growth Factor Receptor

Early Clinical Success of MTA-Cooperative PRMT5 Inhibitors for the Treatment of CDKN2A/MTAP-Deleted Cancers

SUMMARY

CDKN2A encodes the tumor suppressors p16 and p14ARF and is the most common homozygously deleted gene in all human cancers; tumors frequently codelete the nearby gene MTAP, creating a dependency on PRMT5. In this issue of Cancer Discovery, Engstrom and colleagues report an MTA-cooperative PRMT5 methyltransferase inhibitor MRTX1719 that selectively kills CDKN2A/MTAP-codeleted cancers and demonstrates early efficacy in clinical trials for solid tumors harboring the CDKN2A/MTAP codeletion. See related article by Engstrom et al., p. 2412 (1).

DMU-212 against EGFR-mutant non-small cell lung cancer via AMPK/PI3K/Erk signaling pathway

Although some important advances have been achieved in clinical and diagnosis in the past few years, the management of non-small cell lung cancer (NSCLC) is ultimately dissatisfactory due to the low overall cure and survival rates. Epidermal growth factor (EGFR) has been recognized as a carcinogenic driver and is a crucial pharmacological target for NSCLC. DMU-212, an analog of resveratrol, has been reported to have significant inhibitory effects on several types of cancer. However, the effect of DMU-212 on lung cancer remains unclear. Therefore, this study aims to determine the effects and underlying mechanism of DMU-212 on EGFR-mutant NSCLC cells. The data found that the cytotoxicity of DMU-212 on three EGFR-mutant NSCLC cell lines was significantly higher than that of normal lung epithelial cell. Further study showed that DMU-212 can regulate the expression of cell cycle-related proteins including p21 and cyclin B1 to induce G2/M phase arrest in both H1975 and PC9 cells. Moreover, treatment with DMU-212 significantly promoted the activation of AMPK and simultaneously down-regulated the expression of EGFR and the phosphorylation of PI3K, Akt and ERK. In conclusion, our study suggested that DMU-212 inhibited the growth of NSCLCs via targeting of AMPK and EGFR.

Impact of Smoking Status in Combination Treatment with EGFR Tyrosine Kinase Inhibitors and Anti-Angiogenic Agents in Advanced Non-Small Cell Lung Cancer Harboring Susceptible EGFR Mutations: Systematic Review and Meta-Analysis

Patients with advanced non-small cell lung cancer (NSCLC) who harbor susceptible epidermal growth factor receptor (EGFR) mutations and are treated with EGFR tyrosine kinase inhibitors (TKIs) show longer progression-free survival (PFS) than those treated with chemotherapy. However, developed EGFR-TKI resistance limits PFS improvements. Currently, combination treatment with EGFR-TKIs and anti-angiogenic agents is considered a beneficial regimen for advanced-stage NSCLC harboring susceptible EGFR mutations. However, several trials reported osimertinib plus bevacizumab failed to show superior efficacy over osimertinib alone. However, subgroup analysis showed significantly longer PFS among patients with a history of smoking over those who never smoked. We performed a comprehensive systematic review and meta-analysis to evaluate the smoking status impact. At the end of the process, a total of 2068 patients from 11 randomized controlled trials (RCTs) were included in our meta-analysis. Overall, combination EGFR-TKI plus anti-angiogenic agent treatment showed significantly better PFS among patients with a smoking history (Hazard Ratio (HR) = 0.59, 95% confidence interval (CI) = 0.48-0.73). Erlotinib-based combination therapy showed positive PFS benefits regardless of smoking status (HR = 0.54, 95%CI = 0.41-0.71 for ever smoker, HR = 0.69, 95%CI = 0.54-0.87 for never smoker). Combination therapy prolonged PFS significantly regardless of ethnicity (HR: 0.64, 95% CI: 0.44-0.93 for Asian RCTs, HR: 0.55, 95% CI: 0.41-0.74 for global and non-Asian RCTs). PROSPERO registration number is CRD42022304198).

New Genetic Bomb Trigger: Design, Synthesis, Molecular Dynamics Simulation, and Biological Evaluation of Novel BIBR1532-Related Analogs Targeting Telomerase against Non-Small Cell Lung Cancer

Telomeres serve a critical function in cell replication and proliferation at every stage of the cell cycle. Telomerase is a ribonucleoprotein, responsible for maintaining the telomere length and chromosomal integrity of frequently dividing cells. Although it is silenced in most human somatic cells, telomere restoration occurs in cancer cells because of telomerase activation or alternative telomere lengthening. The telomerase enzyme is a universal anticancer target that is expressed in 85–95% of cancers. BIBR1532 is a selective non-nucleoside potent telomerase inhibitor that acts by direct noncompetitive inhibition. Relying on its structural features, three different series were designed, and 30 novel compounds were synthesized and biologically evaluated as telomerase inhibitors using a telomeric repeat amplification protocol (TRAP) assay. Target compounds 29a, 36b, and 39b reported the greatest inhibitory effect on telomerase enzyme with IC₅₀ values of 1.7, 0.3, and 2.0 μM, respectively, while BIBR1532 displayed IC₅₀ = 0.2 μM. Compounds 29a, 36b, and 39b were subsequently tested using a living-cell TRAP assay and were able to penetrate the cell membrane and inhibit telomerase inside living cancer cells. Compound 36b was tested for cytotoxicity against 60 cancer cell lines using the NCI (USA) procedure, and the % growth was minimally impacted, indicating telomerase enzyme selectivity. To investigate the interaction of compound 36b with the telomerase allosteric binding site, molecular docking and molecular dynamics simulations were used.

Epidermal Growth Factor Receptor's Function in Cutaneous Squamous Cell Carcinoma and Its Role as a Therapeutic Target in the Age of Immunotherapies

OPINION STATEMENT

Recent studies have evidenced the potential of combining anti-EGFR therapies with anti-PD-1/PD-L1 checkpoint therapies. Both anti-EGFR and anti-PD-1/PD-L1 have been separately tested in the treatment of cutaneous SCC (cSCC). Here, we review recent data on EGFR in the context of cancer progression, as a prognostic and as a therapeutic target in cSCC. Anti-EGFR/checkpoint immunotherapy and other combination therapy approaches are discussed. With the advent of immunotherapy, EGFR is still a valid cSCC target.

Semaphorin 7A promotes EGFR-TKI resistance in EGFR mutant lung adenocarcinoma cells

Although responses to EGFR tyrosine kinase inhibitors (EGFR-TKIs) are initially positive, 30%-40% of patients with EGFR-mutant tumors do not respond well to EGFR-TKIs, and most lung cancer patients harboring EGFR mutations experience relapse with resistance. Therefore, it is necessary to identify not only the mechanisms underlying EGFR-TKI resistance, but also potentially novel therapeutic targets and/or predictive biomarkers for EGFR-mutant lung adenocarcinoma. We found that the GPI-anchored protein semaphorin 7A (SEMA7A) is highly induced by the EGFR pathway, via mTOR signaling, and that expression levels of SEMA7A in human lung adenocarcinoma specimens were correlated with mTOR activation. Investigations using cell culture and animal models demonstrated that loss or overexpression of SEMA7A made cells less or more resistant to EGFR-TKIs, respectively. The resistance was due to the inhibition of apoptosis by aberrant activation of ERK. The ERK signal was suppressed by knockdown of integrin β1 (ITGB1). Furthermore, in patients with EGFR mutant tumors, higher SEMA7A expression in clinical samples predicted poorer response to EGFR-TKI treatment. Collectively, these data show that the SEMA7A-ITGB1 axis plays pivotal roles in EGFR-TKI resistance mediated by ERK activation and apoptosis inhibition. Moreover, our results reveal the potential utility of SEMA7A not only as a predictive biomarker, but also as a potentially novel therapeutic target in EGFR-mutant lung adenocarcinoma.

A peptide mimicking the binding sites of VEGF-A and VEGF-B inhibits VEGFR-1/-2 driven angiogenesis, tumor growth and metastasis

Interfering with interactions of vascular endothelial growth factors (VEGFs) with their receptors (VEGFRs) effectively inhibits angiogenesis and tumor growth. We designed an antagonist peptide of VEGF-A and VEGF-B reproducing two discontinuous receptor binding regions of VEGF-B (loop 1 and loop3) covalently linked together by a receptor binding region of VEGF-A (loop3). The designed peptide (referred to as VGB4) was able to bind to both VEGFR1 and VEGFR2 on the Human Umbilical Vein Endothelial Cells (HUVECs) surface and inhibited VEGF-A driven proliferation, migration and tube formation in HUVECs through suppression of ERK1/2 and AKT phosphorylation. The whole-animal fluorescence imaging demonstrated that fluorescein isothiocyanate (FITC)-VGB4 accumulated in the mammary carcinoma tumors (MCTs). Administration of VGB4 led to the regression of 4T1 murine MCT growth through decreased expression of p-VEGFR1 and p-VEGFR2 and abrogation of ERK1/2 and AKT activation followed by considerable decrease of tumor cell proliferation (Ki67 expression) and angiogenesis (CD31 and CD34 expression), induction of apoptosis (increased p53 expression, TUNEL staining and decreased Bcl2 expression), and suppression of metastasis  (increased E-cadherin and decreased N-cadherin, NF-κB and MMP-9 expression). These findings indicate that VGB4 may be applicable for antiangiogenic and antitumor therapy.

Structure-Based Drug Design Studies Toward the Discovery of Novel Chalcone Derivatives as Potential Epidermal Growth Factor Receptor (EGFR) Inhibitors

Human Epidermal Growth Factor Receptor-1 (EGFR), a transmembrane tyrosine kinase receptor (RTK), has been associated with several types of cancer, including breast, lung, ovarian, and anal cancers. Thus, the receptor was targeted by a variety of therapeutic approaches for cancer treatments. A series of chalcone derivatives are among the most highly potent and selective inhibitors of EGFR described to date. A series of chalcone derivatives were proposed in this study to investigate the intermolecular interactions in the active site utilizing molecular docking and molecular dynamics simulations. After a careful analysis of docking results, compounds 1a and 1d were chosen for molecular dynamics simulation study. Extensive hydrogen bond analysis throughout 7 ns molecular dynamics simulation revealed the ability of compounds 1a and 1d to retain the essential interactions needed for the inhibition, especially MET 93. Finally, MM-GBSA calculations highlight on the capability of the ligands to bind strongly within the active site with binding energies of −44.04 and −56.6 kcal/mol for compounds 1a and 1d, respectively. Compound 1d showed to have a close binding energy with TAK-285 (−66.17 kcal/mol), which indicates a high chance for compound 1d to exhibit inhibitory activity, thus recommending to synthesis it to test its biological activity. It is anticipated that the findings reported here may provide very useful information for designing effective drugs for the treatment of EGFR-related cancer disease.

Intrapleural targeted therapies (anti-VEGF and anti-EGFR) in the model of malignant pleural effusion

Rationale

Malignant pleural effusion has few options of treatment and drugs administrated by different routes can lead to a less permissive microenvironment for the development of malignant pleural disease.

Objectives

To analyze therapies administered intrapleurally in malignant pleural disease and to study EGFR and KRAS mutations in adenocarcinoma.

Methods

Mice received LLC cells and were treated intrapleurally with anti-VEGF, anti-EGFR, anti-VEGF+anti-EGFR or saline. Animal survival, weight and mobility, volume, biochemistry and immunology of fluid, gene expression, KRAS and EGFR mutation were evaluated.

Results

All animals developed malignant effusion and presented progressive weight loss without difference between groups; however, groups treated with anti-EGFR were more active. No difference in mortality was observed. Temporal increase of volume and inflammatory markers was observed mainly in the untreated group. Gene expression in tumors was overexpressed in VEGF, EGFR and KRAS compared with normal tissue. Mutation in exon 2 of the KRAS gene was observed.

Conclusions

Intrapleural Anti-VEGF and/or anti-EGFR reduced volume and inflammatory mediators in pleural fluid. Anti-EGFR and anti-VEGF+anti-EGFR decreased morbidity although without impact on survival. LLC tumors presented KRAS mutation, this could have influenced the action of these therapies.

Bevacizumab counteracts VEGF-dependent resistance to erlotinib in an EGFR-mutated NSCLC xenograft model

Erlotinib, an epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI), shows superior efficacy in patients with non-small cell lung cancer (NSCLC) harboring activating EGFR mutations (EGFR Mut⁺). However, almost all tumors eventually develop resistance to erlotinib. Recently, the Phase II JO25567 study reported significant prolongation of progression-free survival (PFS) by erlotinib plus bevacizumab combination compared with erlotinib in EGFR Mut⁺ NSCLC. Herein, we established a preclinical model which became refractory to erlotinib after long-term administration and elucidated the mode of action of this combination. In this model, tumor regrowth occurred after remarkable shrinkage by erlotinib; regrowth was successfully inhibited by erlotinib plus bevacizumab. Tumor vascular endothelial growth factor (VEGF) was greatly reduced by erlotinib in the erlotinib-sensitive phase but significantly increased in the erlotinib-refractory phase despite continued treatment with erlotinib. Although EGFR phosphorylation remained suppressed in the erlotinib-refractory phase, phosphorylated extracellular signal-regulated kinase (pERK), phosphorylated AKT, and phosphorylated signal transducer and activator of transcription 3 (pSTAT3) were markedly higher than in the erlotinib-sensitive phase; among these, pERK was suppressed by erlotinib plus bevacizumab. MVD was decreased significantly more with erlotinib plus bevacizumab than with each drug alone. In conclusion, the erlotinib plus bevacizumab combination demonstrated promising efficacy in the B901L xenograft model of EGFR Mut⁺ NSCLC. Re-induction of VEGF and subsequent direct or indirect VEGF-dependent tumor growth was suggested as a major mechanism of erlotinib resistance, and erlotinib plus bevacizumab achieved remarkably prolonged antitumor activity in this model.

MiR-30 Family Potentially Targeting PI3K-SIAH2 Predicted Interaction Network Represents a Novel Putative Theranostic Panel in Non-small Cell Lung Cancer

Non-small cell lung cancer (NSCLC) comprises about 84% of all lung cancers. Many treatment options are available but the survival rate is still very low due to drug resistance. It has been found that phosphoinositide-3-kinase (PI3K) affects sensitivity to tyrosine kinase inhibitors (TKIs), including gefitinib and erlotinib. Expression level of seven in absentia homolog 2 (SIAH2), an E3 ubiquitin-protein ligase, is upregulated in NSCLC and correlated with tumor grade. However, the relationship between PI3K and SIAH2 remains unclear and therefore it is not known whether they can act as treatment co-targets and theranostic dual markers for overcoming TKI resistance. It is worthy to note that PI3K and SIAH2 are potentially regulated by a common group of microRNAs in miR-30 family. Our bioinformatics analyses showed upregulated SIAH2 expression in NSCLC based on mass spectrometry data, explored its indirect interaction with PI3K and predicted their targeting microRNAs in common. We have also explored the potential role of miR-30 family in the modulation of PI3K-SIAH2 interaction in NSCLC.

MiR-30a-5p Overexpression May Overcome EGFR-Inhibitor Resistance through Regulating PI3K/AKT Signaling Pathway in Non-small Cell Lung Cancer Cell Lines

Lung cancer is one of the most common deadly diseases worldwide, most of which is non-small cell lung cancer (NSCLC). The epidermal growth factor receptor (EGFR) mutant NSCLCs frequently respond to the EGFR tyrosine kinase inhibitors (EGFR-TKIs) treatment, such as Gefitinib and Erlotinib, but the development of acquired resistance limits the utility. Multiple resistance mechanisms have been explored, e.g., the activation of alternative tyrosine kinase receptors (TKRs) sharing similar downstream pathways to EGFR. MicroRNAs (miRNAs) are short, endogenous and non-coding RNA molecules, regulating the target gene expression. In this study, we explored the potential of miR-30a-5p in targeting the EGFR and insulin-like growth factor receptor-1 (IGF-1R) signaling pathways to overcome the drug resistance. IGF-1R is one of the tyrosine kinase receptors that share the same EGFR downstream molecules, including phosphatidylinositol 3 kinase (PI3K) and protein kinase B (AKT). In this work, an in vitro study was designed using EGFR inhibitor (Gefitinib), IGF-1R inhibitor (NVP-AEW541), and miRNA mimics in two Gefitinib-resistant NSCLC cell lines, H460 and H1975. We found that the combination of EGFR and IGF-1R inhibitors significantly decreased the phosphorylated AKT (p-AKT) expression levels compared to the control group in these two cell lines. Knockdown of phosphoinositide-3-kinase regulatory subunit 2 (PIK3R2) had the same effect with the dual inhibition of EGFR and IGF-1R to reduce the expression of p-AKT in the signaling pathway. Overexpression of miR-30a-5p significantly reduced the expression of the PI3K regulatory subunit (PIK3R2) to further induce cell apoptosis, and inhibit cell invasion and migration properties. Hence, miR-30a-5p may play vital roles in overcoming the acquired resistance to EGFR-TKIs, and provide useful information for establishing novel cancer treatment.

Lung squamous cell carcinoma with brachial soft tissue metastasis responsive to gefitinib: Report of a rare case

Metastasis of lung cancer to soft tissue is rare and patient outcomes are generally poor. There are no reports describing soft tissue metastasis in lung squamous cell carcinoma (SCC), in which gefitinib treatment was effective not only for the primary tumor but also the metastatic lesion. A 61‐year‐old Asian woman presented to our facility with pain and a mass in the brachium. An additional tumor was identified in the lung. As we suspected soft tissue metastasis of lung cancer, an incisional biopsy was performed, yielding a diagnosis of SCC. The brachial tumor continued to grow and became exposed at the biopsy site when the incisional wound dehisced. Because the biopsied specimen was positive for an epidermal growth factor receptor (EGFR) gene mutation, we commenced gefitinib administration. This treatment resulted in the rapid shrinkage of both the brachial metastasis and the primary tumor, followed by healing of the wound. Therefore, tyrosine kinase inhibitors should be used for cases that present EGFR activating mutations independently from the presence of skin and soft tissue metastases.

Associations of mRNA:microRNA for the Shared Downstream Molecules of EGFR and Alternative Tyrosine Kinase Receptors in Non-small Cell Lung Cancer

Lung cancer is the top cancer killer worldwide with high mortality rate. Majority belong to non-small cell lung cancers (NSCLCs). The epidermal growth factor receptor (EGFR) has been broadly explored as a drug target for therapy. However, the drug responses are not durable due to the acquired resistance. MicroRNAs (miRNAs) are small non-coding and endogenous molecules that can inhibit mRNA translation initiation and degrade mRNAs. We wonder if some downstream molecules shared by EGFR and the other tyrosine kinase receptors (TKRs) further transduce the signals alternatively, and some miRNAs play the key roles in affecting the expression of these downstream molecules. In this study, we investigated the mRNA:miRNA associations for the direct EGFR downstream molecules in the EGFR signaling pathway shared with the other TKRs, including c-MET (hepatocyte growth factor receptor), Ron (a protein tyrosine kinase related to c-MET), PDGFR (platelet-derived growth factor receptor), and IGF-1R (insulin-like growth factor receptor-1). The multiple linear regression and support vector regression (SVR) models were used to discover the statistically significant and the best weighted miRNAs regulating the mRNAs of these downstream molecules. These two models revealed the similar mRNA:miRNA associations. It was found that the miRNAs significantly affecting the mRNA expressions in the multiple regression model were also those with the largest weights in the SVR model. To conclude, we effectively identified a list of meaningful mRNA:miRNA associations: phospholipase C, gamma 1 (PLCG1) with miR-34a, phosphoinositide-3-kinase, regulatory subunit 2 (PIK3R2) with miR-30a-5p, growth factor receptor-bound protein 2 (GRB2) with miR-27a, and Janus kinase 1 (JAK1) with miR-302b and miR-520e. These associations could make great contributions to explore new mechanism in NSCLCs. These candidate miRNAs may be regarded as the potential drug targets for treating NSCLCs with acquired drug resistance.

Identification of phenotype-relevant differentially expressed genes in breast cancer demonstrates enhanced quantile discretization protocol's utility in multi-platform microarray data integration

Microarray for transcriptomics experiments often suffer from limited statistical power due to small sample size. Quantile discretization (QD) maps expression values for a sample into a series of equivalently sized 'bins' that represent a discrete numerical range, e.g. [Formula: see text]4 to [Formula: see text]4, which enables normalized data from multiple experiments and/or expression platforms to be combined for re-analysis. We found, however, that informal selection of bin numbers often resulted in loss of the underlying correlation structure in the data through assigning of the same numerical value to genes that are in reality expressed at significantly different levels within a sample. Here we report a procedure for determining an optimal bin number for dataset. Applying this to integrated public breast cancer datasets enabled statistical identification of several differentially expressed tumorigenesis-related genes that were not found when analyzing the individual datasets, and also several cancer biomarkers not previously indicated as having utility in the disease. Notably, differential modulation of translational control and protein synthesis via multiple pathways were found to potentially have central roles in breast cancer development and progression. These findings suggest that our protocol has significant utility in making meaningful novel biomedical discoveries by leveraging the large public expression data repositories.

Multi-Center Randomized Phase II Study Comparing Cediranib plus Gefitinib with Cediranib plus Placebo in Subjects with Recurrent/Progressive Glioblastoma

BACKGROUND

Cediranib, an oral pan-vascular endothelial growth factor (VEGF) receptor tyrosine kinase inhibitor, failed to show benefit over lomustine in relapsed glioblastoma. One resistance mechanism for cediranib is up-regulation of epidermal growth factor receptor (EGFR). This study aimed to determine if dual therapy with cediranib and the oral EGFR inhibitor gefitinib improved outcome in recurrent glioblastoma.

METHODS AND FINDINGS

This was a multi-center randomized, two-armed, double-blinded phase II study comparing cediranib plus gefitinib versus cediranib plus placebo in subjects with first relapse/first progression of glioblastoma following surgery and chemoradiotherapy. The primary outcome measure was progression free survival (PFS). Secondary outcome measures included overall survival (OS) and radiologic response rate. Recruitment was terminated early following suspension of the cediranib program. 38 subjects (112 planned) were enrolled with 19 subjects in each treatment arm. Median PFS with cediranib plus gefitinib was 3.6 months compared to 2.8 months for cediranib plus placebo (HR; 0.72, 90% CI; 0.41 to 1.26). Median OS was 7.2 months with cediranib plus gefitinib and 5.5 months with cediranib plus placebo (HR; 0.68, 90% CI; 0.39 to 1.19). Eight subjects (42%) had a partial response in the cediranib plus gefitinib arm versus five patients (26%) in the cediranib plus placebo arm.

CONCLUSIONS

Cediranib and gefitinib in combination is tolerated in patients with glioblastoma. Incomplete recruitment led to the study being underpowered. However, a trend towards improved survival and response rates with the addition of gefitinib to cediranib was observed. Further studies of the combination incorporating EGFR and VEGF inhibition are warranted.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01310855.

Molecular Targeting of Growth Factor Receptor Signaling in Radiation Oncology

Ionizing radiation has been shown to activate and interact with multiple growth factor receptor pathways that can influence tumor response to therapy. Among these receptor interactions, the epidermal growth factor receptor (EGFR) has been the most extensively studied with mature clinical applications during the last decade. The combination of radiation and EGFR-targeting agents using either monoclonal antibody (mAb) or small-molecule tyrosine kinase inhibitor (TKI) offers a promising approach to improve tumor control compared to radiation alone. Several underlying mechanisms have been identified that contribute to improved anti-tumor capacity after combined treatment. These include effects on cell cycle distribution, apoptosis, tumor cell repopulation, DNA damage/repair, and impact on tumor vasculature. However, as with virtually all cancer drugs, patients who initially respond to EGFR-targeted agents may eventually develop resistance and manifest cancer progression. Several potential mechanisms of resistance have been identified including mutations in EGFR and downstream signaling molecules, and activation of alternative member-bound tyrosine kinase receptors that bypass the inhibition of EGFR signaling. Several strategies to overcome the resistance are currently being explored in preclinical and clinical models, including agents that target the EGFR T790 M resistance mutation or target multiple EGFR family members, as well as agents that target other receptor tyrosine kinase and downstream signaling sites. In this chapter, we focus primarily on the interaction of radiation with anti-EGFR therapies to summarize this promising approach and highlight newly developing opportunities.

Acquired resistance of non-small cell lung cancer to epidermal growth factor receptor tyrosine kinase inhibitors

Activation of epidermal growth factor receptor (EGFR) triggers anti-apoptotic signaling, proliferation, angiogenesis, invasion, metastasis, and drug resistance, which leads to development and progression of human epithelial cancers, including non-small cell lung cancer (NSCLC). Inhibition of EGFR by tyrosine kinase inhibitors such as gefitinib and erlotinib has provided a new hope for the cure of NSCLC patients. However, acquired resistance to gefitinib and erlotinib via EGFR-mutant NSCLC has occurred through various molecular mechanisms such as T790M secondary mutation, MET amplification, hepatocyte growth factor (HGF) overexpression, PTEN downregulation, epithelial-mesenchymal transition (EMT), and other mechanisms. This review will discuss the biology of receptor tyrosine kinase inhibition and focus on the molecular mechanisms of acquired resistance to tyrosine kinase inhibitors of EGFR-mutant NSCLC.

Role of tumor markers in patients with solid cancers: A critical review

The measurement of tumor markers is currently one of the most rapidly growing areas in laboratory medicine. Lack of sensitivity and specificity preclude the use of most existing markers for the early detection of malignancy. For patients with diagnosed malignancy, however, markers are potentially useful in determining prognosis, predicting therapeutic response, maintaining surveillance following curative surgery and monitoring therapy in advanced disease. Clinically useful markers include CEA in the surveillance of patients with diagnosed colorectal cancer, AFP and HCG in the management of patients with non-seminomatous germ cell tumors, HCG in the management of patients with trophoblastic disease, CA 125 for monitoring therapy in patients with ovarian cancer, estrogen receptors for predicting response to hormone therapy in breast cancer and HER-2 for the identification of women with breast cancer likely to respond to trastuzumab (Herceptin). Although widely used, the impact of PSA screening in reducing mortality from prostate cancer remains to be shown.