Alterations in genes of the EGFR signaling pathway and their relationship to EGFR tyrosine kinase inhibitor sensitivity in lung cancer cell lines

Antitumor activity of sorafenib in human cancer cell lines with acquired resistance to EGFR and VEGFR tyrosine kinase inhibitors

Treatment of non small cell lung cancer (NSCLC) and colorectal cancer (CRC) have substantially changed in the last years with the introduction of epidermal growth factor receptor (EGFR) inhibitors in the clinical practice. The understanding of mechanisms which regulate cells sensitivity to these drugs is necessary for their optimal use.An in vitro model of acquired resistance to two tyrosine kinase inhibitors (TKI) targeting the EGFR, erlotinib and gefitinib, and to a TKI targeting EGFR and VEGFR, vandetanib, was developed by continuously treating the human NSCLC cell line CALU-3 and the human CRC cell line HCT116 with escalating doses of each drug. MTT, western blot analysis, migration, invasion and anchorage-independent colony forming assays were conducted in vitro and experiments with established xenografts in athymic nude mice were performed in vivo in sensitive, wild type (WT) and TKI-resistant CALU-3 and HCT116 cell lines.As compared to WT CALU-3 and HCT116 human cancer cells, TKI-resistant cell lines showed a significant increase in the levels of activated, phosphorylated AKT, MAPK, and of survivin. Considering the role of RAS and RAF as downstream signals of both the EGFR and VEGFR pathways, we treated resistant cells with sorafenib, an inhibitor of C-RAF, B-RAF, c-KIT, FLT-3, RET, VEGFR-2, VEGFR-3, and PDGFR-β. Sorafenib reduced the activation of MEK and MAPK and caused an inhibition of cell proliferation, invasion, migration, anchorage-independent growth in vitro and of tumor growth in vivo of all TKI-resistant CALU-3 and HCT116 cell lines.These data suggest that resistance to EGFR inhibitors is predominantly driven by the RAS/RAF/MAPK pathway and can be overcame by treatment with sorafenib.

KRAS mutant allele-specific imbalance in lung adenocarcinoma

The significance of KRAS mutant allele-specific imbalance (MASI) in lung adenocarcinomas is unknown. KRAS MASI was defined as predominance of the mutant allele over the wild-type allele. We assessed the frequency of KRAS MASI by comparing peak heights of mutant and wild-type alleles on sequencing electropherograms and by KRAS fluorescence in situ hybridization (FISH). A review of sequencing electropherograms of 207 KRAS-mutated lung adenocarcinomas demonstrated 23 (11%) cases with the mutant allele peak higher than the wild-type allele peak and 15 (7%) cases with the mutant allele peak equal to the wild-type allele peak. Of 17 cases with the mutant allele peak higher or equal to the wild-type allele peak, 8 (47%) showed KRAS amplification by FISH. KRAS FISH analysis of 36 KRAS-mutated lung adenocarcinomas with the mutant allele peak lower than the wild-type allele peak, 21 KRAS and EGFR wild-type and 16 EGFR-mutated adenocarcinomas showed no KRAS amplification. KRAS MASI was associated with selective amplification of the KRAS mutant allele (P<0.001). Patients with KRAS MASI showed worse overall survival. The cumulative proportion surviving at 17 months for KRAS MASI group was 35% compared with 84.1% for patients with KRAS mutant allele peak lower than wild-type allele peak (P=0.012). The adverse prognostic significance of KRAS MASI was independent of clinical stage and was maintained among stage I patients. The detection of KRAS MASI in lung adenocarcinomas by sequencing electropherograms may identify patients with more aggressive disease.

Erlotinib has better efficacy than gefitinib in adenocarcinoma patients without EGFR-activating mutations, but similar efficacy in patients with EGFR-activating mutations

Epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) are an effective treatment for advanced non-small cell lung cancer. The objective of the present study was to compare the efficacy of gefitinib and erlotinib in patients with pulmonary adenocarcinoma, whose tumor EGFR mutation status was known. Pulmonary adenocarcinoma patients who began receiving gefitinib or erlotinib treatment from January 2005 to December 2010, and whose tumor EGFR mutation status had been determined, were included. Clinical data, type of treatment response and survival time data were collected. Of the 224 patients enrolled, 124 received gefitinib treatment and 100 received erlotinib treatment. Of these patients, 146 individuals had tumors with EGFR-activating mutations (exon 19 deletions and/point mutation of L858R in exon 21) and 78 did not. There was no difference in treatment response whether or not the patients had tumors with EGFR-activating mutations at the time they received gefitinib or erlotinib treatment. The median progression-free survival (PFS) of the gefitinib and erlotinib groups was 7.6 and 7.9 months, respectively (p=0.4731). PFS was significantly longer for patients without EGFR-activating mutations who received erlotinib treatment (n=48; median, 4.5 months) than for those who received gefitinib treatment (n=30; median, 2.3 months), with a hazard ratio of 0.58 (95% CI, 0.35-0.96; p=0.0339). Patients whose tumors had EGFR-activating mutations displayed no difference in PFS with either gefitinib (n=94; median, 10.5 months) or erlotinib treatment (n=52; median, 10.4 months). In conclusion, PFS showed no difference with either agent in patients whose tumors had EGFR-activating mutations, but was significantly longer in patients whose tumors did not have EGFR-activating mutations when receiving erlotinib treatment.

The genomics of lung adenocarcinoma: opportunities for targeted therapies

Standard cytotoxic chemotherapy is effective for some cancers, but for many others, available treatments offer only a limited survival benefit. Lung adenocarcinoma is one such cancer, responsible for approximately half of lung cancer deaths each year. Development of targeted therapies is thought to hold the most promise for successfully treating this disease, but a targeted approach is dependent on understanding the genomic state of the tumor cells. Exon-directed sequencing of large numbers of lung adenocarcinoma tumor samples has provided an initial low-resolution image of the somatic mutation profile of these tumors. Such cancer sequencing studies have confirmed the high frequency of TP53 and KRAS mutations in lung adenocarcinoma, have found inactivating mutations in known tumor suppressor genes not previously associated with lung adenocarcinoma, and have identified oncogenic mutations of EGFR upon which the first targeted therapy for lung adenocarcinoma patients was based. Additional candidate oncogenes await functional validation. It is anticipated that upcoming whole-exome and whole-genome lung adenocarcinoma sequencing experiments will reveal a more detailed landscape of somatic mutations that can be exploited for therapeutic purposes.

Should we continue to use the term non-small-cell lung cancer?

Until recently the major clinical question was 'Is it small-cell or non small-cell cancer'. However, advances in conventional and targeted therapy have completely changed the landscape. Identification of the major non-small-cell lung cancer (NSCLC) types (adenocarcinoma and squamous carcinoma) are important for a number of predictive and prognostic reasons, including pemetrexed treatment, anti-angiogenic therapy and administration of tyrosine kinase inhibitors. Fortunately, advances in pathology of lung cancer have kept abreast, with newer, simplified methods to identify the major NSCLC types in small diagnostic samples, and modifications of the pathological classification of adenocarcinomas reflecting changing clinical and molecular concepts. For the patient to obtain maximum benefit from the recent developments in therapeutics, a multidisciplinary approach is required with co-operation between oncologists, surgeons, radiologists and pathologists.

Antitumour efficacy of MEK inhibitors in human lung cancer cells and their derivatives with acquired resistance to different tyrosine kinase inhibitors

Background:

To study the molecular mechanisms regulating cancer cell resistance to four different tyrosine kinase inhibitors (TKIs): erlotinib, gefitinib, vandetanib and sorafenib.

Methods:

An in vitro model of acquired resistance to these TKIs was developed by continuously treating the human lung adenocarcinoma cell line CALU-3 with escalating doses of each drug. Transcriptional profiling was performed with Agilent whole genome microarrays. Western blot analysis, enzyme-linked immunosorbent (ELISA), 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cell proliferation, migration, invasion and anchorage-independent colony growth assays were conducted in vitro and experiments with established xenografts in athymic nude mice were performed in vivo in parental (P) and TKI-resistant (R) CALU-3 cell lines.

Results:

As compared with P-CALU-3 cells, in TKI-R CALU-3 cell lines a significant increase in the expression of activated, phosphorylated MET, IGF-1R, AKT, MEK, MAPK and of survivin was observed. Downregulation of E-cadherin and amphiregulin mRNAs and upregulation of vimentin, VE-cadherin, HIF-1α and vascular endothelial growth factor receptor-1 mRNAs were observed in all four TKI-R CALU-3 cell lines. All four TKI-R CALU-3 cells showed increased invasion, migration and anchorage-independent growth. Together, these data suggest epithelial to mesenchymal transition (EMT) in TKI-R CALU-3 cells. Treatment with several agents that target AKT, MET or IGF-1R did not affect TKI-R CALU-3 cell proliferation. In contrast, treatment with MSC19363669B and selumetinib, two selective MEK inhibitors, caused inhibition of cell proliferation, invasion, migration, anchorage-independent growth in vitro and of tumour growth in vivo of all four TKI-R CALU-3 cell lines.

Conclusion:

These data suggest that resistance to four different TKIs is characterised by EMT, which is MEK-inhibitor sensitive in human CALU-3 lung adenocarcinoma.

Quantitative and sensitive detection of rare mutations using droplet-based microfluidics

Somatic mutations within tumoral DNA can be used as highly specific biomarkers to distinguish cancer cells from their normal counterparts. These DNA biomarkers are potentially useful for the diagnosis, prognosis, treatment and follow-up of patients. In order to have the required sensitivity and specificity to detect rare tumoral DNA in stool, blood, lymph and other patient samples, a simple, sensitive and quantitative procedure to measure the ratio of mutant to wild-type genes is required. However, techniques such as dual probe TaqMan(®) assays and pyrosequencing, while quantitative, cannot detect less than ∼1% mutant genes in a background of non-mutated DNA from normal cells. Here we describe a procedure allowing the highly sensitive detection of mutated DNA in a quantitative manner within complex mixtures of DNA. The method is based on using a droplet-based microfluidic system to perform digital PCR in millions of picolitre droplets. Genomic DNA (gDNA) is compartmentalized in droplets at a concentration of less than one genome equivalent per droplet together with two TaqMan(®) probes, one specific for the mutant and the other for the wild-type DNA, which generate green and red fluorescent signals, respectively. After thermocycling, the ratio of mutant to wild-type genes is determined by counting the ratio of green to red droplets. We demonstrate the accurate and sensitive quantification of mutated KRAS oncogene in gDNA. The technique enabled the determination of mutant allelic specific imbalance (MASI) in several cancer cell-lines and the precise quantification of a mutated KRAS gene in the presence of a 200,000-fold excess of unmutated KRAS genes. The sensitivity is only limited by the number of droplets analyzed. Furthermore, by one-to-one fusion of drops containing gDNA with any one of seven different types of droplets, each containing a TaqMan(®) probe specific for a different KRAS mutation, or wild-type KRAS, and an optical code, it was possible to screen the six common mutations in KRAS codon 12 in parallel in a single experiment.

Heterogeneous distribution of EGFR mutations is extremely rare in lung adenocarcinoma

PURPOSE

Some studies have shown that epidermal growth factor receptor (EGFR) mutations can be heterogeneously distributed in individual tumors. In this study, we re-evaluated the distribution of EGFR mutations within tumors.

PATIENTS AND METHODS

We used multiple approaches, including an analysis of simultaneous dual hot spot mutations, a trans-sectional analysis of individual lung adenocarcinomas, and comparisons of the mutation patterns between primary and metastatic sites and between primary and recurrent tumors.

RESULTS

None of the 862 tumors harboring an EGFR mutation showed simultaneous dual hot spot mutations, although identical EGFR mutations were found throughout individual tumors in a trans-sectional analysis involving 50 tumors divided into three parts and five lung adenocarcinomas divided into 100 parts. In addition, no discordant mutation patterns were detected among 77 paired primary and metastatic site samples or among 54 primary and recurrent tumor pairs.

CONCLUSION

All of these results suggest that the heterogeneous distribution of EGFR mutations is extremely rare. However, it is possible that pseudoheterogeneity occurs because of a combination of mutant allele-specific imbalance and heterogeneously distributed EGFR amplification, especially when a less sensitive method is used for detection. Specifically, when EGFR amplification occurs, the mutant allele is amplified, and this amplification is involved in invasive growth. Accordingly, invasive growth area significantly over-represents the mutation signal. In contrast, weak EGFR mutation signals in the area without EGFR amplification may not reach the threshold of detection because of the mixture with normal cells. Such unbalanced mutation signals might lead to pseudoheterogeneity.

Multiplex mutation screening by mass spectrometry evaluation of 820 cases from a personalized cancer medicine registry

There is an immediate and critical need for a rapid, broad-based genotyping method that can evaluate multiple mutations simultaneously in clinical cancer specimens and identify patients most likely to benefit from targeted agents now in use or in late-stage clinical development. We have implemented a prospective genotyping approach to characterize the frequency and spectrum of mutations amenable to drug targeting present in urothelial, colorectal, endometrioid, and thyroid carcinomas and in melanoma. Cancer patients were enrolled in a Personalized Cancer Medicine Registry that houses both clinical information and genotyping data, and mutation screening was performed using a multiplexed assay panel with mass spectrometry-based analysis to detect 390 mutations across 30 cancer genes. Formalin fixed, paraffin-embedded specimens were evaluated from 820 Registry patients. The genes most frequently mutated across multiple cancer types were BRAF, PIK3CA, KRAS, and NRAS. Less common mutations were also observed in AKT1, CTNNB1, FGFR2, FGFR3, GNAQ, HRAS, and MAP2K1. Notably, 48 of 77 PIK3CA-mutant cases (62%) harbored at least one additional mutation in another gene, most often KRAS. Among melanomas, only 54 of 73 BRAF mutations (74%) were the V600E substitution. These findings demonstrate the diversity and complexity of mutations in druggable targets among the different cancer types and underscore the need for a broad-spectrum, prospective genotyping approach to personalized cancer medicine.

Epigenetic silencing of microRNA-34b/c plays an important role in the pathogenesis of malignant pleural mesothelioma

PURPOSE

Malignant pleural mesothelioma (MPM) is an aggressive tumor with a dismal prognosis. Unlike other malignancies, TP53 mutations are rare in MPM. Recent studies have showed that altered expression of microRNA (miRNA) is observed in human malignant tumors. In this study, we investigated the alterations of miR-34s, a direct transcriptional target of TP53, and the role of miR-34s on the pathogenesis of MPM.

EXPERIMENTAL DESIGN

Aberrant methylation and expression of miR-34s were examined in MPM cell lines and tumors. miR-34b/c was transfected to MPM cells to estimate the protein expression, cell proliferation, invasion, and cell cycle.

RESULTS

Aberrant methylation was present in 2 (33.3%) of 6 MPM cell lines and 13 (27.7%) of 47 tumors in miR-34a and in all 6 MPM cell lines (100%) and 40 (85.1%) of 47 tumors in miR-34b/c. Expression of miR-34a and 34b/c in all methylated cell lines was reduced and restored with 5-aza-2'-deoxycytidine treatment. Because epigenetic silencing was the major event in miR-34b/c, we investigated the functional role of miR-34b/c in MPM. miR-34b/c-transfected MPM cells with physiologic miR-34b/c expression exhibited antiproliferation with G(1) cell cycle arrest and suppression of migration, invasion, and motility. The forced overexpression of miR-34b/c, but not p53, showed a significant antitumor effect with the induction of apoptosis in MPM cells.

CONCLUSIONS

We show that the epigenetic silencing of miR-34b/c by methylation is a crucial alteration and plays an important role in the tumorigenesis of MPM, suggesting potential therapeutic options for MPM.

Pivotal role of epithelial cell adhesion molecule in the survival of lung cancer cells

Epithelial cell adhesion molecule (EpCAM) is overexpressed in a wide variety of human cancers including lung cancer, and its contribution to increased proliferation through upregulation of cell cycle accelerators such as cyclins A and E has been well established in breast and gastric cancers. Nevertheless, very little is known about its role in supporting the survival of cancer cells. In addition, the functional role of EpCAM in the pathogenesis of lung cancer remains to be explored. In this study, we show that RNAi-mediated knockdown of EpCAM suppresses proliferation and clonogenic growth of three EpCAM-expressing lung cancer cell lines (H3255, H358, and HCC827), but does not induce cell cycle arrest in any of these. In addition, EpCAM knockdown inhibits invasion in the highly invasive H358 but not in less invasive H3255 cells in a Transwell assay. Of note, the EpCAM knockdown induces massive apoptosis in the three cell lines as well as in another EpCAM-expressing lung cancer cell line, HCC2279, but to a much lesser extent in a cdk4/hTERT immortalized normal human bronchial epithelial cell line, HBEC4, suggesting that EpCAM could be a therapeutic target for lung cancer. Finally, EpCAM knockdown partially restores contact inhibition in HCC827, in association with p27(Kip1) upregulation. These results indicate that EpCAM could contribute substantially to the pathogenesis of lung cancer, especially cancer cell survival, and suggest that EpCAM targeted therapy for lung cancer may have potential.

Insights into ALK-driven cancers revealed through development of novel ALK tyrosine kinase inhibitors

Aberrant forms of the anaplastic lymphoma kinase (ALK) have been implicated in the pathogenesis of multiple human cancers, where ALK represents a rational therapeutic target in these settings. In this study, we report the identification and biological characterization of X-376 and X-396, two potent and highly specific ALK small molecule tyrosine kinase inhibitors (TKIs). In Ambit kinome screens, cell growth inhibition studies, and surrogate kinase assays, X-376 and X-396 were more potent inhibitors of ALK but less potent inhibitors of MET compared to PF-02341066 (PF-1066), an ALK/MET dual TKI currently in clinical trials. Both X-376 and X-396 displayed potent antitumor activity in vivo with favorable pharmacokinetic and toxicity profiles. Similar levels of drug sensitivity were displayed by the three most common ALK fusion proteins in lung cancer (EML4-ALK variants E13;A20, E20;A20, and E6b;A20) as well as a KIF5B-ALK fusion protein. Moreover, X-396 could potently inhibit ALK kinases engineered with two point mutations associated with acquired resistance to PF-1066, L1196M, and C1156Y, when engineered into an E13;A20 fusion variant. Finally, X-396 displayed synergistic growth inhibitory activity when combined with the mTOR inhibitor rapamycin. Our findings offer preclinical proof-of-concept for use of these novel agents to improve therapeutic outcomes of patients with mutant ALK-driven malignancies.

Pyrosequencing, a method approved to detect the two major EGFR mutations for anti EGFR therapy in NSCLC

Background

Epidermal Growth Factor Receptor (EGFR) mutations, especially in-frame deletions in exon 19 (ΔLRE) and a point mutation in exon 21 (L858R) predict gefitinib sensitivity in patients with non-small cell lung cancer. Several methods are currently described for their detection but the gold standard for tissue samples remains direct DNA sequencing, which requires samples containing at least 50% of tumor cells.

Methods

We designed a pyrosequencing assay based on nested PCR for the characterization of theses mutations on formalin-fixed and paraffin-embedded tumor tissue.

Results

This method is highly specific and permits precise characterization of all the exon 19 deletions. Its sensitivity is higher than that of "BigDye terminator" sequencing and enabled detection of 3 additional mutations in the 58 NSCLC tested. The concordance between the two methods was very good (97.4%). In the prospective analysis of 213 samples, 7 (3.3%) samples were not analyzed and EGFR mutations were detected in 18 (8.7%) patients. However, we observed a deficit of mutation detection when the samples were very poor in tumor cells.

Conclusions

pyrosequencing is then a highly accurate method for detecting ΔLRE and L858R EGFR mutations in patients with NSCLC when the samples contain at least 20% of tumor cells.

Molecular mode of action and role of TP53 in the sensitivity to the novel epothilone sagopilone (ZK-EPO) in A549 non-small cell lung cancer cells

Sagopilone, an optimized fully synthetic epothilone, is a microtubule-stabilizing compound that has shown high in vitro and in vivo activity against a broad range of human tumor models. We analyzed the differential mechanism of action of sagopilone in non-small cell lung cancer cell lines in vitro. Sagopilone inhibited proliferation of non-small cell lung cancer cell lines at lower nanomolar concentration. The treatment with sagopilone caused strong disturbances of cellular cytoskeletal organization. Two concentration-dependent phenotypes were observed. At 2.5 nM sagopilone or 4 nM paclitaxel an aneuploid phenotype occur whereas a mitotic arrest phenotype was induced by 40 nM sagopilone or paclitaxel. Interestingly, treatment with 2.5 nM of sagopilone effectively inhibited cell proliferation, but - compared to high concentrations (40 nM) - only marginally induced apoptosis. Treatment with a high versus a low concentration of sagopilone or paclitaxel regulates a non-overlapping set of genes, indicating that both phenotypes substantially differ from each other. Genes involved in G2/M phase transition and the spindle assembly checkpoint, like Cyclin B1 and BUBR1 were upregulated by treatment with 40 nM sagopilone. Unexpectedly, also genes involved in DNA damage response were upregulated under that treatment. In contrast, treatment of A549 cells with a low concentration of sagopilone revealed an upregulation of direct transcriptional target genes of TP53, like CDKN1A, MDM2, GADD45A, FAS. Knockdown of TP53, which inhibited the transcriptional induction of TP53 target genes, led to a significant increase in apoptosis induction in A549 cells when treated with a low concentration of sagopilone. The results indicate that activation of TP53 and its downstream effectors like CDKN1A by low concentrations of sagopilone is responsible for the relative apoptosis resistance of A549 cells and might represent a mechanism of resistance to sagopilone.

Somatic mutations in epidermal growth factor receptor signaling pathway genes in non-small cell lung cancers

INTRODUCTION

Epidermal growth factor receptor (EGFR) signaling pathway plays a crucial role in the development and progression of lung cancer. We searched for mutations of EGFR pathway genes in non-small cell lung cancers (NSCLCs) and analyzed their relationship with clinicopathologic features.

METHODS

Mutations of EGFR, ERBB2, ERBB3, ERBB4, KRAS, NRAS, BRAF, PTEN, PIK3CA, LKB1, and AKT1 genes were determined by direct sequencing in 173 surgically resected NSCLCs--56 squamous cell carcinomas (SCCs) and 117 adenocarcinomas (ACs).

RESULTS

Of the 173 NSCLCs, a total of 65 mutations were detected in 63 (36.4%) tumors--10 (17.9%) in SCCs and 53 (45.3%) in ACs. Mutations in EGFR pathway genes were significantly more frequent in women and ACs than in women and SCCs (p = 0.02 and p < 0.001, respectively). The mutations occurred in a mutually exclusive pattern. When the genes were divided into three subgroups according to their roles in the signaling cascade, mutations in the EGFR/ERBB2 and KRAS/BRAF genes were more frequent in ACs than in SCCs (p < 0.001 and p = 0.01, respectively). In marked contrast, mutations in the PIK3CA/PTEN were more frequent in SCCs than in ACs (p = 0.002). Furthermore, mutations in the PIK3CA/PTEN genes were more frequent in smokers (p = 0.04).

DISCUSSION

Our study demonstrates that mutations in each part of the EGFR pathway were associated with different clinicopathologic features in patients with NSCLCs.

Mass spectrometry mapping of epidermal growth factor receptor phosphorylation related to oncogenic mutations and tyrosine kinase inhibitor sensitivity

The epidermal growth factor receptor (EGFR) plays an important role in cancer by activating downstream signals important in growth and survival. Inhibitors of EGFR are frequently selected as treatment for cancer including lung cancer. We performed an unbiased and comprehensive search for EGFR phosphorylation events related to somatic activating mutations and EGFR inhibitor (erlotinib) sensitivity. EGFR immunoprecipitation combined with high resolution liquid chromatography-mass spectrometry and label free quantitation characterized EGFR phosphorylation. Thirty (30) phosphorylation sites were identified including 12 tyrosine (pY), 12 serine (pS), and 6 threonine (pT). Site-specific phosphorylation was monitored by comparing ion signals from the corresponding unmodified peptide. Phosphorylation sites related to activating mutations in EGFR as well as sensitivity to erlotinib were identified using 31 lung cancer cell lines. We identified three sites (pY1092, pY1110, pY1172) correlated with activating mutations and three sites (pY1110, pY1172, pY1197) correlated with erlotinib sensitivity. Five sites (pT693, pY1092, pY1110, pY1172, and pY1197) were inhibited by erlotinib in concentration-dependent manner. Erlotinib sensitivity was confirmed using liquid chromatography coupled to multiple reaction monitoring (LC-MRM) and quantitative Western blotting. This LC-MS/MS strategy can quantitatively assess site-specific EGFR phosphorylation and can identify relationships between somatic mutations or drug sensitivity and protein phosphorylation.

A platform for rapid detection of multiple oncogenic mutations with relevance to targeted therapy in non-small-cell lung cancer

The identification of somatically acquired tumor mutations is increasingly important in the clinical management of cancer because the sensitivity of targeted drugs is related to the genetic makeup of individual tumors. Thus, mutational profiles of tumors can help prioritize anticancer therapy. We report herein the development and validation of two multiplexed assays designed to detect in DNA from FFPE tissue more than 40 recurrent mutations in nine genes relevant to existing and emerging targeted therapies in lung cancer. The platform involves two methods: a screen (SNaPshot) based on multiplex PCR, primer extension, and capillary electrophoresis that was designed to assess for 38 somatic mutations in eight genes (AKT1, BRAF, EGFR, KRAS, MEK1, NRAS, PIK3CA, and PTEN) and a PCR-based sizing assay that assesses for EGFR exon 19 deletions, EGFR exon 20 insertions, and HER2 exon 20 insertions. Both the SNaPshot and sizing assays can be performed rapidly, with minimal amounts of genetic material. Compared with direct sequencing, in which mutant DNA needs to compose 25% or more of the total DNA to easily detect a mutation, the SNaPshot and sizing assays can detect mutations in samples in which mutant DNA composes 1.56% to 12.5% and 1.56% to 6.25% of the total DNA, respectively. These robust, reliable, and relatively inexpensive assays should help accelerate adoption of a genotype-driven approach in the treatment of lung cancer.

[Molecular characteristics of lung cancer]

While no real improvement in the long term survival has been obtained in lung cancer, during this decade a significant improvement in cancer control has been obtained by biology driven targeted therapy as with anti EGFR tyrosine kinase. Two phases can be described in the knowledge of lung cancer biology: a first phase open in the 1980s describing the main molecular anomalies and impaired cell control mechanisms, and a second phase starting in the 2004-2005 giving rise to the therapeutic applications of this knowledge. A new molecular classification of lung cancer, particularly adenocarcinomas will soon be proposed for therapeutic application.

Predictive biomarkers in the management of EGFR mutant lung cancer

Activating mutations in the form of deletions in exon 19 (del 19) or the missense mutation L858R in the tyrosine kinase domain of the epidermal growth factor receptor (EGFR) predict outcome to use of EGFR tyrosine kinase inhibitors (TKIs), such as gefitinib and erlotinib. Pooled data from several phase II studies show that gefitinib and erlotinib induce responses in over 70% of NSCLC patients harboring EGFR mutations, with progression-free survival (PFS) ranging from 9 to 13 months. Two studies in Caucasian and Asian patients have confirmed that these subgroups of patients attain PFS up to 14 months. These landmark outcomes have been accompanied by new challenges, primarily the additional role of chemotherapy and the management of tumors with the secondary T790M mutation that confers resistance to EGFR TKIs. Mechanisms of resistance to reversible EGFR TKIs should be further clarified and could be related to modifications in DNA repair.

Reciprocal and complementary role of MET amplification and EGFR T790M mutation in acquired resistance to kinase inhibitors in lung cancer

PURPOSE

In epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) therapy for lung cancer patients, acquired resistance develops almost inevitably and this limits the improvement in patient outcomes. EGFR T790M mutation and MET amplification are the two main mechanisms underlying this resistance, but the relationship between these two mechanisms is unclear. In this study, we explored their relationship using in vitro models and autopsy specimens.

EXPERIMENTAL DESIGN

Erlotinib-resistant HCC827 (HCC827ER) cells were developed by chronic exposure to erlotinib at increasing concentrations. HCC827EPR cells were also developed by chronic exposure to erlotinib in the presence of PHA-665,752 (a MET TKI). The erlotinib-resistant mechanisms of these cells were analyzed. In addition, 33 autopsy tumor samples from 6 lung adenocarcinoma patients harboring multiple gefitinib-refractory tumors were analyzed.

RESULTS

HCC827ER developed MET amplification, and clinically relevant resistance occurred at ≥4-fold MET gene copy number gain (CNG). By contrast, HCC827EPR developed T790M without MET CNG. Of six patients harboring gefitinib-refractory tumors, three exhibited T790M only, one exhibited MET amplification only, and the other two exhibited T790M and/or MET amplification depending on the lesion sites. In these gefitinib-refractory tumors, T790M developed in 93% (14 of 15) of tumors without MET gene CNGs, in 80% (4 of 5) of tumors with moderate MET gene CNGs (<4-fold), and in only 8% (1 of 13) of tumors with MET amplification (≥4-fold).

CONCLUSIONS

These results indicate a reciprocal and complementary relationship between T790M and MET amplification and the necessity of concurrent inhibition of both for further improving patient outcomes.

Using iTRAQ combined with tandem affinity purification to enhance low-abundance proteins associated with somatically mutated EGFR core complexes in lung cancer

In this study, we report a novel use for the iTRAQ reagent combined with a peptide mass inclusion list to enhance the signal of low-abundance proteins during analysis by mass spectrometry. C-tagged-SH-EGFR was retrovirally transduced into two mutant lung cancer cell lines (HCC827 and PC9), and the core protein complexes were enriched by tandem affinity purification. Tryptically digested peptides were derivatized with iTRAQ and analyzed by higher-energy collision-induced dissociation mass spectrometry. The data revealed that UBS3B is a member of the EGFR core complex in the HCC827 cell line, which was not apparent by standard, unbiased one-dimensional shotgun analysis and collision-induced dissociation. The expression level of UBS3B, however, was 6-10 times lower than that observed in the PC9 cell line. Thus, using iTRAQ in this fashion allows the identification of low-abundance interactors when combined with samples where the same protein has a higher abundance. Ultimately, this approach may uncover proteins that were previously unknown or only suspected as members of core protein complexes.

Rational, biologically based treatment of EGFR-mutant non-small-cell lung cancer

Epidermal growth factor receptor (EGFR)-mutant non-small-cell lung cancer (NSCLC) was first recognized in 2004 as a distinct, clinically relevant molecular subset of lung cancer. The disease has been the subject of intensive research at both the basic scientific and clinical levels, becoming a paradigm for how to understand and treat oncogene-driven carcinomas. Although patients with EGFR-mutant tumours have increased sensitivity to tyrosine kinase inhibitors (TKIs), primary and acquired resistance to these agents remains a major clinical problem. This Review summarizes recent developments aimed at treating and ultimately curing the disease.

Erlotinib at a dose of 25 mg daily for non-small cell lung cancers with EGFR mutations

PURPOSE

The tyrosine kinase inhibitors (TKIs) gefitinib and erlotinib are effective in non-small cell lung cancers (NSCLCs) with epidermal growth factor receptor (EGFR) gene mutations. The usual clinical dose of gefitinib (250 mg/d) is only one third of its maximum tolerated dose, whereas the dose of erlotinib (150 mg/d) is at its maximum tolerated dose. In NSCLC cell lines, both TKIs have similar micromolar inhibitory concentrations. We explored whether erlotinib at 25 mg/d (trough serum concentration similar to gefitinib 250 mg/d) would be efficacious in EGFR-mutated NSCLC.

METHODS

To study the inhibitory concentrations of gefitinib and erlotinib, we exposed EGFR-mutated cell lines (HCC827, H3255, PC-9, and H1975) to increasing concentrations of these TKIs. Further on, we performed a retrospective evaluation of seven patients with advanced EGFR-mutated (exon 19 deletions and L858R) NSCLC that were given erlotinib at 25 mg/d as their first EGFR TKI.

RESULTS

Gefitinib and erlotinib generated similar inhibitory curves across our panel of EGFR-mutated NSCLC cell lines with overlapping mean 50% inhibitory concentration 95% confidence intervals for HCC827, PC-9, and H1975. Both drugs also displayed a high degree of correlation in mean 50% inhibitory concentration (Pearson's r = 0.99, p = 0.0417). Of the seven patients, five patients (71.5%) had partial responses to erlotinib 25 mg/d. Median progression-free survival was 17 months (95% confidence interval, 6-35 months). Toxicities were minimal, with only two (28.5%) patients having a rash and none experiencing (0%) diarrhea.

CONCLUSIONS

In NSCLC cell lines, gefitinib and erlotinib have similar inhibitory profiles. In patients with NSCLC and EGFR-activating mutations, a dose of erlotinib 25 mg/d (equivalent to gefitinib 250 mg/d) leads to impressive response rates and progression-free survival similar to the growing experience with the approved doses of gefitinib (250 mg/d) and erlotinib (150 mg/d). Identifying prospectively the lowest and clinically active dose ranges of erlotinib and gefitinib will help further to personalize care for patients with tumors harboring EGFR mutations.

TGF-beta IL-6 axis mediates selective and adaptive mechanisms of resistance to molecular targeted therapy in lung cancer

The epidermal growth-factor receptor (EGFR) tyrosine kinase inhibitor erlotinib has been proven to be highly effective in the treatment of nonsmall cell lung cancer (NSCLC) harboring oncogenic EGFR mutations. The majority of patients, however, will eventually develop resistance and succumb to the disease. Recent studies have identified secondary mutations in the EGFR (EGFR T790M) and amplification of the N-Methyl-N'-nitro-N-nitroso-guanidine (MNNG) HOS transforming gene (MET) oncogene as two principal mechanisms of acquired resistance. Although they can account for approximately 50% of acquired resistance cases together, in the remaining 50%, the mechanism remains unknown. In NSCLC-derived cell lines and early-stage tumors before erlotinib treatment, we have uncovered the existence of a subpopulation of cells that are intrinsically resistant to erlotinib and display features suggestive of epithelial-to-mesenchymal transition (EMT). We showed that activation of TGF-beta-mediated signaling was sufficient to induce these phenotypes. In particular, we determined that an increased TGF-beta-dependent IL-6 secretion unleashed previously addicted lung tumor cells from their EGFR dependency. Because IL-6 and TGF-beta are prominently produced during inflammatory response, we used a mouse model system to determine whether inflammation might impair erlotinib sensitivity. Indeed, induction of inflammation not only stimulated IL-6 secretion but was sufficient to decrease the tumor response to erlotinib. Our data, thus, argue that both tumor cell-autonomous mechanisms and/or activation of the tumor microenvironment could contribute to primary and acquired erlotinib resistance, and as such, treatments based on EGFR inhibition may not be sufficient for the effective treatment of lung-cancer patients harboring mutant EGFR.

Steroid receptor coactivator-3 expression in lung cancer and its role in the regulation of cancer cell survival and proliferation

Steroid receptor coactivator-3 (SRC-3) is a histone acetyltransferase and nuclear hormone receptor coactivator, located on 20q12, which is amplified in several epithelial cancers and well studied in breast cancer. However, its possible role in lung cancer pathogenesis is unknown. We found SRC-3 to be overexpressed in 27% of non-small cell lung cancer (NSCLC) patients (n = 311) by immunohistochemistry, which correlated with poor disease-free (P = 0.0015) and overall (P = 0.0008) survival. Twenty-seven percent of NSCLCs exhibited SRC-3 gene amplification, and we found that lung cancer cell lines expressed higher levels of SRC-3 than did immortalized human bronchial epithelial cells (HBEC), which in turn expressed higher levels of SRC-3 than did cultured primary human HBECs. Small interfering RNA-mediated downregulation of SRC-3 in high-expressing, but not in low-expressing, lung cancer cells significantly inhibited tumor cell growth and induced apoptosis. Finally, we found that SRC-3 expression is inversely correlated with gefitinib sensitivity and that SRC-3 knockdown results in epidermal growth factor receptor tyrosine kinase inhibitor-resistant lung cancers becoming more sensitive to gefitinib. Taken together, these data suggest that SRC-3 may be an important oncogene and therapeutic target for lung cancer.

Lung cancer cell lines as tools for biomedical discovery and research

Lung cancer cell lines have made a substantial contribution to lung cancer translational research and biomedical discovery. A systematic approach to initiating and characterizing cell lines from small cell and non-small cell lung carcinomas has led to the current collection of more than 200 lung cancer cell lines, a number that exceeds those for other common epithelial cancers combined. The ready availability and widespread dissemination of the lines to investigators worldwide have resulted in more than 9000 citations, including multiple examples of important biomedical discoveries. The high (but not perfect) genomic similarities between lung cancer cell lines and the lung tumor type from which they were derived provide evidence of the relevance of their use. However, major problems including misidentification or cell line contamination remain. Ongoing studies and new approaches are expected to reveal the full potential of the lung cancer cell line panel.

Integrating molecular diagnostics into anticancer drug discovery

In the 1990s, the breast cancer drug trastuzumab (Herceptin; Genentech/Roche)--an antibody specific for human epidermal growth factor receptor 2 (HER2; also known as ERBB2)--was approved based on trials in which HER2 expression levels were used to select patients in clinical trials. This provided support for analogous efforts for drugs that target the epidermal growth factor receptor (EGFR). However, the development of these drugs, such as cetuximab (Erbitux; Bristol-Myers Squibb/Lilly) and gefitinib (Iressa; AstraZeneca), has revealed that EGFR expression is an insufficient and unreliable biomarker to select patients for EGFR-targeted therapies in both lung and colon cancer. Indeed, evidence on patient populations that are likely to respond to such therapies, on the basis of specific mutations in proteins of the targeted pathway, has only recently been clinically validated and incorporated into some of the drug labels. This article highlights lessons learned from the development of the first drugs targeting the EGFR family and discusses strategies to decrease the risk of failure in clinical development by more effectively integrating molecular diagnostics into anticancer drug discovery.

Knockdown of ZEB1, a master epithelial-to-mesenchymal transition (EMT) gene, suppresses anchorage-independent cell growth of lung cancer cells

We found that among four master epithelial-to-mesenchymal transition (EMT)-inducing genes (ZEB1, SIP1, Snail, and Slug) ZEB1expression was most significantly correlated with the mesenchymal phenotype (high Vimentin and low E-cadherin expression) in non-small cell lung cancer (NSCLC) cell lines and tumors. Furthermore, ZEB1 knockdown with RNA interference in three NSCLC cell lines with high ZEB1 expression suppressed to varying degrees mass culture growth and liquid colony formation but in all cases dramatically suppressed soft agar colony formation. In addition, ZEB1 knockdown induced apoptosis in one of the three lines, indicating that the growth inhibitory effects of ZEB1 knockdown occurs in part through the activation of the apoptosis pathway. These results suggest that inhibiting ZEB1 function may be an attractive target for NSCLC therapeutic development.

Epidermal growth factor receptor tyrosine kinase inhibitors as first-line treatment in advanced nonsmall-cell lung cancer

PURPOSE OF REVIEW

Classic activating mutations in the form of deletions in exon 19 or a missense mutation L858R in the tyrosine kinase domain of the epidermal growth factor receptor (EGFR) predict dramatic responses to EGFR tyrosine kinase inhibitors such as gefitinib and erlotinib. We review here the clinical benefits of targeted therapy with erlotinib and gefitinib in white and Asian nonsmall-cell lung cancer patients.

RECENT FINDINGS

Two separate analyses of pooled data from small phase II prospective studies show that therapy with gefitinib and erlotinib induces responses in over 70% of nonsmall-cell lung cancer patients harboring classic EGFR mutations, with progression-free survival ranging from 9 to 13 months and median survival of around 23 months. Two separate studies in white and Asian patients have recently confirmed that these subgroups of patients attain response rates of 70% with erlotinib and gefitinib, including complete responses, progression-free survival of up to 14 months, and median survival of up to 27 months. The serial monitoring of EGFR mutations in the blood will permit the assessment of molecular responses and be an important tool for the surveillance of clinical progression.

SUMMARY

Nonsmall-cell lung cancer with EGFR mutations constitute a new entity with a unique opportunity for further refinement of different genetic subgroups among patients with EGFR mutations, requiring different personalized treatment strategies. Despite the impressive outcomes attained with EGFR tyrosine kinase inhibitors, patients with EGFR mutations at present require continuous treatment, and only a fraction of these patients will reach sustainable long-term survival.

EGFR mutations and the terminal respiratory unit

Considerable knowledge has accumulated about mutations of the epidermal growth factor receptor (EGFR)-tyrosine kinase domain since these were first identified in 2004. Patients with nonsmall cell lung cancer with this mutation show dramatic clinical responses to treatment with EGFR-tyrosine kinase inhibitors, whose effectiveness has been established recently in large clinical trials. Most of the mechanisms responsible for resistance to treatment, which most responders experience eventually, have been elucidated, and methods to overcome resistance have been developed. In addition to the clinical benefit, understanding EGFR mutations sheds new light on the molecular and pathological aspects of this adenocarcinoma subset, which include frequent development in nonsmokers or females, and particular clusters within the molecular classification in lung cancer. In contrast to the involvement of EGFR mutations in the early stage of lung adenocarcinoma development, EGFR amplification is superimposed on the progression to invasive cancer. In this review, I summarize the clinicopathological characteristics of EGFR mutations in lung cancer. I also provide an overview of the current understanding of the lung adenocarcinoma subset harboring EGFR mutations with special reference to the molecular classification of lung cancer and the novel concept of the "terminal respiratory unit."

Lung cancer in never smokers: molecular profiles and therapeutic implications

The majority of lung cancers are caused by long term exposure to the several classes of carcinogens present in tobacco smoke. Although a significant fraction of lung cancers in never smokers may also be attributable to tobacco, many such cancers arise in the absence of detectable tobacco exposure, and may follow a very different cellular and molecular pathway of malignant transformation. Recent studies summarized here suggest that lung cancers arising in never smokers have a distinct natural history, profile of oncogenic mutations, and response to targeted therapy. The majority of molecular analyses of lung cancer have focused on genetic profiling of pathways responsible for metabolism of primary tobacco carcinogens. Limited research has been conducted evaluating familial aggregation and genetic linkage of lung cancer, particularly among never smokers in whom such associations might be expected to be strongest. Data emerging over the past several years show that lung cancers in never smokers are much more likely to carry activating mutations of the epidermal growth factor receptor (EGFR), a key oncogenic factor and direct therapeutic target of several newer anticancer drugs. EGFR mutant lung cancers may represent a distinct class of lung cancers, enriched in the never-smoking population, and less clearly linked to direct tobacco carcinogenesis. These insights followed initial testing and demonstration of efficacy of EGFR-targeted drugs. Focused analysis of molecular carcinogenesis in lung cancers in never smokers is needed, and may provide additional biologic insight with therapeutic implications for lung cancers in both ever smokers and never smokers.

The detection of chromosomal aneusomy by fluorescence in situ hybridization in sputum predicts lung cancer incidence

Lung cancer usually is disseminated (advanced) and has a poor prognosis at diagnosis. Current and former smokers are at a high risk for lung cancer and are candidates for prevention and early detection strategies. Sputum is a potential source of biomarkers that might determine either lung cancer risk or the presence of early lung cancer, but no current sputum test is sufficiently sensitive and specific for effective screening. We used fluorescence in situ hybridization (FISH) to measure chromosomal aneusomy (CA) in sputum samples collected prospectively from 100 incident lung cancer cases and 96 controls (matched on age, gender, and date of collection) nested within an ongoing high-risk cohort. The CA-FISH assay was aimed at four DNA targets: epidermal growth factor receptor, MYC, 5p15, and CEP 6. The sensitivity of a positive CA-FISH assay (abnormal for two or more of the four markers) for lung cancer was substantially higher for samples collected within 18 months (76% sensitivity) than for samples collected more than 18 months (31%) before lung cancer diagnosis. Sensitivity was higher for squamous cell cancers (94%) than for other histologic types (69%). CA-FISH specificity based on samples collected within 18 months before diagnosis was 88%. The adjusted odds ratio (OR) of lung cancer for specimens collected within 18 months before a cancer diagnosis was higher for the CA-FISH assay [OR, 29.9; 95% confidence interval (95% CI), 9.5-94.1] than for previously studied ORs of cytologic atypia (OR, 1.8; 95% CI, 1.3-2.6) and gene promoter methylation (OR, 6.5; 95% CI, 1.2-35.5). Whether CA-FISH is an indicator of extreme risk for incident lung cancer or detects exfoliated cancer cells is unknown. The apparent promise of CA-FISH in sputum for assessing lung cancer risk and/or for lung cancer early detection now needs to be validated in a clinical screening trial.

Pharmacogenomic discovery using cell-based models

Quantitative variation in response to drugs in human populations is multifactorial; genetic factors probably contribute to a significant extent. Identification of the genetic contribution to drug response typically comes from clinical observations and use of classic genetic tools. These clinical studies are limited by our inability to control environmental factors in vivo and the difficulty of manipulating the in vivo system to evaluate biological changes. Recent progress in dissecting genetic contribution to natural variation in drug response through the use of cell lines has been made and is the focus of this review. A general overview of current cell-based models used in pharmacogenomic discovery and validation is included. Discussion includes the current approach to translate findings generated from these cell-based models into the clinical arena and the use of cell lines for functional studies. Specific emphasis is given to recent advances emerging from cell line panels, including the International HapMap Project and the NCI60 cell panel. These panels provide a key resource of publicly available genotypic, expression, and phenotypic data while allowing researchers to generate their own data related to drug treatment to identify genetic variation of interest. Interindividual and interpopulation differences can be evaluated because human lymphoblastoid cell lines are available from major world populations of European, African, Chinese, and Japanese ancestry. The primary focus is recent progress in the pharmacogenomic discovery area through ex vivo models.

Epidermal growth factor receptor inhibition in lung cancer: the evolving role of individualized therapy

Non-small cell lung cancer (NSCLC) is the major cause of cancer-related deaths in the USA and worldwide. Most patients present with advanced disease, and treatment options for these patients are generally limited to platinum-based chemotherapy and a few targeted therapies. Targeted agents currently in use for NSCLC inhibit oncogenic receptor tyrosine kinase pathways, such as the epidermal growth factor receptor (EGFR) pathway. While current EGFR-targeted agents, including erlotinib and gefitinib, may result in dramatic responses, they demonstrate efficacy in only a fraction of patients, and resistance to these agents frequently develops. In order to select patients most likely to benefit from blockade of EGFR pathways, investigators have focused on identifying molecular correlates of response to anti-EGFR therapy. New strategies to minimize the risk of resistance to EGFR inhibition have been employed in the development of next-generation EGFR tyrosine kinase inhibitors, such as PF00299804 and BIBW 2992; these include irreversibility of target binding, inhibition of multiple EGFR family receptors, and/or simultaneous inhibition of EGFR and other oncogenic pathways.

A chemical and phosphoproteomic characterization of dasatinib action in lung cancer

We describe a strategy to comprehend signaling pathways active in lung cancer cells and targeted by dasatinib employing chemical proteomics to identify direct interacting proteins combined with immunoaffinity purification of tyrosine phosphorylated peptides corresponding to activated tyrosine kinases. We identified nearly 40 different kinase targets of dasatinib. These include SFK members (LYN, SRC, FYN, LCK, YES), non-receptor tyrosine kinases (FRK, BRK, ACK), and receptor tyrosine kinases (Ephrin receptors, DDR1, EGFR). Using quantitative phosphoproteomics we identified peptides corresponding to autophosphorylation sites of these tyrosine kinases that are inhibited in a concentration-dependent manner by dasatinib. Using drug resistant gatekeeper mutants, we show that SFK kinases, particularly SRC and FYN, as well as EGFR are relevant targets for dasatinib action. The combined mass spectrometry based approach described here provides a system-level view of dasatinib action in cancer cells and suggests both functional targets and rationale combinatorial therapeutic strategies.

Efficacy of erlotinib for brain and leptomeningeal metastases in patients with lung adenocarcinoma who showed initial good response to gefitinib

INTRODUCTION

The efficacy of high-dose (1250 mg/d) gefitinib for the treatment of leptomeningeal metastasis in a patient with lung cancer harboring a mutation in the epidermal growth factor receptor (EGFR) gene was previously reported. We speculate that erlotinib, instead of high dose of gefitinib, may be also effective for the treatment of central nervous system (CNS) lesions, as trough serum concentration of erlotinib is nine times higher than that of gefitinib.

PATIENTS AND METHODS

Patients with lung cancer in whom CNS lesions developed after an initial good response to gefitinib for extra CNS lesions were enrolled in the study. Tumor response, performance status, neurologic symptoms, and survival were retrospectively evaluated.

RESULTS

All seven patients had EGFR mutations in their primary tumors except one patient. The median interval between gefitinib withdrawal and erlotinib administration was 5 days. Three patients showed partial response, three had stable disease, and one had progressive disease. Performance status and symptoms improved in five patients. The overall survival from the initiation of erlotinib treatment ranged from 15 to 530 days (median, 88 days).

CONCLUSIONS

Erlotinib was a reasonable option for the treatment of CNS diseases that appeared after a good initial response of extra CNS disease to gefitinib.

Lung cancer cell lines: Useless artifacts or invaluable tools for medical science?

Multiple cell lines (estimated at 300-400) have been established from human small cell (SCLC) and non-small cell lung cancers (NSCLC). These cell lines have been widely dispersed to and used by the scientific community worldwide, with over 8000 citations resulting from their study. However, there remains considerable skepticism on the part of the scientific community as to the validity of research resulting from their use. These questions center around the genomic instability of cultured cells, lack of differentiation of cultured cells and absence of stromal-vascular-inflammatory cell compartments. In this report we discuss the advantages and disadvantages of the use of cell lines, address the issues of instability and lack of differentiation. Perhaps the most important finding is that every important, recurrent genetic and epigenetic change including gene mutations, deletions, amplifications, translocations and methylation-induced gene silencing found in tumors has been identified in cell lines and vice versa. These "driver mutations" represented in cell lines offer opportunities for biological characterization and application to translational research. Another potential shortcoming of cell lines is the difficulty of studying multistage pathogenesis in vitro. To overcome this problem, we have developed cultures from central and peripheral airways that serve as models for the multistage pathogenesis of tumors arising in these two very different compartments. Finally the issue of cell line contamination must be addressed and safeguarded against. A full understanding of the advantages and shortcomings of cell lines is required for the investigator to derive the maximum benefit from their use.

Clinical outcomes in non-small-cell lung cancer patients with EGFR mutations: pooled analysis

Non-small-cell lung cancer (NSCLC) with mutations in the epidermal growth factor receptor (EGFR) is a distinct subgroup of NSCLCs that is particularly responsive to EGFR tyrosine-kinase inhibitors (TKIs). A weighted pooled analysis of available studies was performed to evaluate clinical outcome in patients with EGFR-mutated NSCLC who were treated with chemotherapy or EGFR TKIs. Median progression-free survival (PFS) times were pooled from prospective or retrospective studies that evaluated chemotherapy or single-agent EGFR TKIs (erlotinib or gefitinib) in patients with NSCLC and EGFR mutations. Among the studies identified for inclusion in the analysis, 12 evaluated erlotinib (365 patients), 39 evaluated gefitinib (1069 patients) and 9 evaluated chemotherapy (375 patients). Across all studies, the most common EGFR mutations were deletions in exon 19 and the L858R substitution in exon 21. In the weighted pooled analysis, the overall median PFS was 13.2 months with erlotinib, 9.8 months with gefitinib and 5.9 months with chemotherapy. Using a two-sided permutation, erlotinib and gefitinib produced a longer median PFS versus chemotherapy, both individually (P= 0.000 and P= 0.002, respectively) and as a combined group (EGFR TKI versus chemotherapy, P= 0.000). EGFR TKIs appear to be the most effective treatment for patients with advanced EGFR-mutant NSCLC. Ongoing prospective trials comparing the efficacy of first-line chemotherapy and EGFR TKIs in EGFR-mutant disease should provide further insight into the most appropriate way to treat this specific group of patients.

[Molecular diagnostics in lung carcinoma for therapy stratification]

Lung cancer is the most common tumor-related cause of death in western industrialized countries, despite continuous improvement in both diagnostic and therapeutic approaches. Since epidermal growth factor receptor (EGFR) is overexpressed in 80% of cases of non-small cell lung carcinoma, mediating important carcinogenic properties such as cell-cycle progression, apoptosis, angiogenesis and metastasis, it is considered a relevant target in novel specific therapies. This has lead to the development of the low-molecular EGFR tyrosine kinase inhibitors (EGFR-TKI) Gefitinib and Erlotinib. Predicting which patients will respond to an EGFR-targeted therapy is of particular clinical interest. Recent studies show a significantly better response and prolonged progression-free survival in patients with EGFR-mutated tumors, even when used as first-line therapy. Moreover, genetic mutations which correlate to primary EGFR-TKI resistance (e.g. KRAS) or produce secondary resistance to known TKI (e.g. EGFR mutation T790 M or MET amplification) have meanwhile been explained. Predictive diagnosis of these mutations using histological material is becoming increasingly important for patient stratification and will soon be indispensable not only for lung cancer.