HER3 genomic gain and sensitivity to gefitinib in advanced non-small-cell lung cancer patients

A Phase I, First-in-Human Study of GSK2849330, an Anti-HER3 Monoclonal Antibody, in HER3-Expressing Solid Tumors

BACKGROUND

GSK2849330, an anti-HER3 monoclonal antibody that blocks HER3/Neuregulin 1 (NRG1) signaling in cancer cells, is engineered for enhanced antibody-dependent cellular cytotoxicity and complement-dependent cytotoxicity. This phase I, first-in-human, open-label study assessed the safety, pharmacokinetics (PK), pharmacodynamics, and preliminary activity of GSK2849330 in patients with HER3-expressing advanced solid tumors.

PATIENTS AND METHODS

Patients with various tumor types were prospectively selected for HER3 expression by immunohistochemistry; a subset was also screened for NRG1 mRNA expression. In the dose-escalation phase, patients received GSK2849330 1.4-30 mg/kg every 2 weeks, or 3 mg/kg or 30 mg/kg weekly, intravenously (IV). In the dose-expansion phase, patients received 30 mg/kg GSK2849330 IV weekly.

RESULTS

Twenty-nine patients with HER3-expressing cancers, of whom two expressed NRG1, received GSK2849330 (dose escalation: n = 18, dose expansion: n = 11). GSK2849330 was well tolerated. No dose-limiting toxicities were observed. The highest dose, of 30 mg/kg weekly, expected to provide full target engagement, was selected for dose expansion. Treatment-emergent adverse events (AEs) were mostly grade 1 or 2. The most common AEs were diarrhea (66%), fatigue (62%), and decreased appetite (31%). Dose-proportional plasma exposures were achieved, with evidence of HER3 inhibition in paired tissue biopsies. Of 29 patients, only 1 confirmed partial response, lasting 19 months, was noted in a patient with CD74-NRG1-rearranged non-small cell lung cancer (NSCLC).

CONCLUSION

GSK2849330 demonstrated a favorable safety profile, dose-proportional PK, and evidence of target engagement, but limited antitumor activity in HER3-expressing cancers. The exceptional response seen in a patient with CD74-NRG1-rearranged NSCLC suggests further exploration in NRG1-fusion-positive cancers.

IMPLICATIONS FOR PRACTICE

This first-in-human study confirms that GSK2849330 is well tolerated. Importantly, across a variety of HER3-expressing advanced tumors, prospective selection by HER3/NRG1 expression alone was insufficient to identify patients who could benefit from treatment with this antibody-dependent cell-mediated cytotoxicity- and complement-dependent cytotoxicity-enhanced anti-HER3 antibody. The only confirmed durable response achieved was in a patient with CD74-NRG1-rearranged lung cancer. This highlights the potential utility of screening for NRG1 fusions prospectively across tumor types to enrich potential responders to anti-HER3 agents in ongoing trials.

HER3 expression and MEK activation in non-small-cell lung carcinoma

Aim:

We explore HER3 expression in lung adenocarcinoma (adeno-NSCLC) and identify potential mechanisms of HER3 expression.

Materials & methods:

Tumor samples from 45 patients with adeno-NSCLC were analyzed. HER3 and HER2 expression were identified using immunohistochemistry and bioinformatic interrogation of The Cancer Genome Atlas (TCGA).

Results:

HER3 was highly expressed in 42.2% of cases. ERBB3 copy number did not account for HER3 overexpression. Bioinformatic analysis of TCGA demonstrated that MEK activity score (a surrogate of functional signaling) did not correlate with HER3 ligands. ERBB3 RNA expression levels were significantly correlated with MEK activity after adjusting for EGFR expression.

Conclusion:

HER3 expression is common and is a potential therapeutic target by virtue of frequent overexpression and functional downstream signaling.

HER3 expression is common in adeno-NSCLC and is a potential therapeutic target by virtue of frequent overexpression and functional downstream signaling.

MiR-519d targets HER3 and can be used as a potential serum biomarker for non-small cell lung cancer

Development of specific serum biomarkers is essential to improve diagnosis and prognosis of non-small cell lung cancer (NSCLC). Here, we show that serum and tissue levels of miR-519d are significantly decreased in NSCLC patients. The low expression of miR-519d is associated with lymph node metastases, clinical stage, and a poor prognosis in NSCLC patients. In addition, ROC analysis demonstrated that the serum miR-519d levels can distinguish NSCLC patients from healthy controls. MiR-519d inhibits proliferation, migration, and invasion by lung cancer cells, indicating that it may function as a tumor suppressor in lung cancer. Furthermore, our data demonstrate that HER3 is a target gene of miR-519d in lung cancer cells, and show that by targeting HER3, miR-519d inhibits the PI3K/Akt pathway. These findings demonstrate that the miR-519d levels are decreased in serum and tumor tissues of NSCLC patients, and indicate that miR-519d regulates NSCLC progression by targeting HER3. MiR-519d could potentially serve as a novel serum biomarker for NSCLC.

An HER3-targeting antibody-drug conjugate incorporating a DNA topoisomerase I inhibitor U3-1402 conquers EGFR tyrosine kinase inhibitor-resistant NSCLC

EGFR tyrosine kinase inhibitors (TKIs) are standard therapy for EGFR-mutant non-small cell lung cancer (NSCLC); however, these tumours eventually acquire chemoresistance. U3-1402 is an anti-HER3 antibody-drug conjugate with a novel topoisomerase I inhibitor, DXd. In the current study, we evaluated the anticancer efficacy of U3-1402 in EGFR-mutant NSCLC cells with acquired resistance to EGFR-TKIs. HCC827GR5 and PC9AZDR7 are EGFR-TKI-resistant clones for gefitinib and osimertinib, respectively. U3-1402 alone or in combination with the EGFR-TKI erlotinib demonstrated potent anticancer efficacy in HCC827GR5 cells using an in vitro growth inhibition assay and in vivo xenograft mouse model. U3-1402 induced apoptosis in HCC827GR5 cells accompanying phosphorylation of histone H2A.X, a marker of DNA damage, but did not block HER3/PI3K/AKT signalling. Further, we found using flow cytometry that the cell surface HER3 expression level in HCC827GR5 cells was twice that found in HCC827 cells, indicating internalization of U3-1402 was increased in resistant cells. In addition, administration of U3-1402 notably repressed growth of EGFR-TKI osimertinib-resistant PC9AZDR7 xenograft tumours, and that PC9AZDR7 cells expressed five times greater cell surface HER3 than PC9 cells. Furthermore, using immunofluorescent microscopy, HER3 was observed predominantly in the nucleus of PC9 cells, but was localized in the cytoplasm of PC9AZDR7 cells. This finding indicates that altered trafficking of the HER3-U3-1402 complex may accelerate linker payload cleavage by cytoplasmic lysosomal enzymes, resulting in DNA damage. Our results indicate that administration of U3-1402 alone or in combination with an EGFR-TKI may have potential as a novel therapy for EGFR-TKI-resistant EGFR-mutant NSCLC.

Surrogate Predictive Biomarkers for Response to Anti-EGFR Agents: State of the Art and Challenges

The epidermal growth factor receptor (EGFR) plays a key role in cancer development and progression in several human malignancies including non-small cell lung cancer (NSCLC). Several strategies aimed at inhibiting the EGFR have been investigated in the last years, including the use of small tyrosine kinase inhibitors (TKIs) directed against the intracellular domain of the receptor and monoclonal antibodies targeting its extracellular portion. Subgroups of patients who are more likely to respond to TKIs have been identified based on both clincal and biological features. Never-smoking history has emerged as the most relevant clinical characteristic predictive of response to TKIs in NSCLC, while presence of drug-sensitive EGFR mutations and EGFR gene gain represent critical biological variables associated with an improved outcome for patients exposed to these agents. Recent studies have highlighted the existence of biological factors involved in intrinsic and acquired resistance to TKIs, including k-ras, HER-2 and EGFR exon 20 mutations. Increasing knowledge of EGFR biology and drug-receptor interactions will allow to identify individuals who are likely to derive a clinical benefit from the proposed targeted therapy, sparing refractory patients expensive and potentially toxic treatment.

Circulating heregulin level is associated with the efficacy of patritumab combined with erlotinib in patients with non-small cell lung cancer

OBJECTIVES

Patritumab is a fully human anti-human epidermal growth factor receptor 3 (HER3) antibody that blocks activation by its ligand, heregulin (HRG). Preclinical studies have demonstrated the efficacy of patritumab in aberrantly high HRG-expressing non-small cell lung cancer (NSCLC). In the phase II randomized, placebo-controlled double-blind study HERALD (n=212 patients with NSCLC), patritumab plus erlotinib did not improve progression-free survival (PFS) compared with placebo plus erlotinib. The current study examined whether soluble HRG (sHRG) level in serum correlated with the efficacy of patritumab plus erlotinib.

MATERIALS AND METHODS

Serum was obtained from participants prior to treatment (n=202). sHRG level was measured using a validated quantitative immune assay, and correlations with survival were blindly assessed.

RESULTS

sHRG level was various (-1346-11,772pg/mL). Participants were divided into the sHRG-high or -low subgroups at the concentration defining near the third quartile, 980pg/mL. Patritumab plus erlotinib significantly improved PFS relative to placebo in the sHRG-high subgroup (n=46, hazard ratio 0.42 [0.19-0.96], p=0.0327). In contrast, the HRG-low subgroup (n=148) had no improvement in PFS with patritumab.

CONCLUSION

sHRG seems to be a predictive biomarker for the efficacy of patritumab plus erlotinib in NSCLC patients.

Estrogen receptor alpha gene amplification in breast cancer: 25 years of debate

Twenty-five years ago, Nembrot and colleagues reported amplification of the estrogen receptor alpha gene (ESR1) in breast cancer, initiating a broad and still ongoing scientific debate on the prevalence and clinical significance of this genetic aberration, which affects one of the most important genes in breast cancer. Since then, a multitude of studies on this topic has been published, covering a wide range of divergent results and arguments. The reported prevalence of this alteration in breast cancer ranges from 0% to 75%, suggesting that ESR1 copy number analysis is hampered by technical and interpreter issues. To date, two major issues related to ESR1 amplification remain to be conclusively addressed: (1) The extent to which abundant amounts of messenger RNA can mimic amplification in standard fluorescence in situ hybridization assays in the analysis of strongly expressed genes like ESR1, and (2) the clinical relevance of ESR1 amplification: Such relevance is strongly disputed, with data showing predictive value for response as well as for resistance of the cancer to anti-estrogen therapies, or for subsequent development of cancers in the case of precursor lesions that display amplification of ESR1. This review provides a comprehensive summary of the various views on ESR1 amplification, and highlights explanations for the contradictions and conflicting data that could inform future ESR1 research.

Overcoming drug resistance to receptor tyrosine kinase inhibitors: Learning from lung cancer

There are various receptor tyrosine kinase (TK)-targeted drugs that are currently used in the treatment of patients with non-small cell lung cancer (NSCLC). Among them, the epidermal growth factor receptor (EGFR) TK inhibitors (TKIs) are the most extensively studied. Receptor TKIs including EGFR TKIs have shown dramatic therapeutic efficacies in malignant tumors, which harbor activating mutations in the EGFR gene. However, within 1 or 2years after treatment, patients harboring these mutations often develop resistance to TKI therapy. This review article is aimed at drawing attention to the fact that we must first understand how receptor TKI resistance is acquired to develop strategies for overcoming resistance to TKIs. Furthermore, an insight into the specific molecules or signaling pathways that mediate resistance is a key factor for understanding and overcoming acquired drug resistance. Finally, we present our views on the continuing battle against "drug resistance," and provide further guidelines and strategies on how to minimize the development of drug-resistant tumors.

Is there a role for epidermal growth factor receptor tyrosine kinase inhibitors in epidermal growth factor receptor wild-type non-small cell lung cancer?

Non-small cell lung cancer (NSCLC) is the most common type of lung cancer with a world-wide annual incidence of around 1.3 million. The majority of patients are diagnosed with advanced disease and survival remains poor. However, relevant advances have occurred in recent years through the identification of biomarkers that predict for benefit of therapeutic agents. This is exemplified by the efficacy of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors for the treatment of EGFR mutant patients. These drugs have also shown efficacy in unselected populations but this point remains controversial. Here we have reviewed the clinical data that demonstrate a small but consistent subgroup of EGFR wild-type patients with NSCLC that obtain a clinical benefit from these drugs. Moreover, we review the biological rationale that may explain this benefit observed in the clinical setting.

Anti-HER3 monoclonal antibody patritumab sensitizes refractory non-small cell lung cancer to the epidermal growth factor receptor inhibitor erlotinib

Human epidermal growth factor receptor (HER) 3 is aberrantly overexpressed and correlates with poor prognosis in non-small cell lung cancer (NSCLC). Patritumab is a monoclonal antibody against HER3 that has shown promising results in early-phase clinical trials, but an optimal target population for the drug has yet to be identified. In the present study, we examined whether heregulin, a HER3 ligand that is also overexpressed in a subset of NSCLC, can be used as a biomarker to predict the antitumorigenic efficacy of patritumab and whether the drug can overcome the epidermal growth factor receptor tyrosine kinase inhibitor (EGFR TKI) resistance induced by heregulin. Patritumab sensitivity was associated with heregulin expression, which, when abolished, resulted in the loss of HER3 and AKT activation and growth arrest. Furthermore, heregulin overexpression induced EGFR TKI resistance in NSCLC cells harbouring an activating EGFR mutation, while HER3 and AKT activation was maintained in the presence of erlotinib in heregulin-overexpressing, EGFR-mutant NSCLC cells. Sustained HER3-AKT activation was blocked by combining erlotinib with either anti-HER2 or anti-HER3 antibody. Notably, heregulin was upregulated in tissue samples from an NSCLC patient who had an activating EGFR mutation but was resistant to the TKI gefitinib. These results indicate that patritumab can overcome heregulin-dependent EGFR inhibitor resistance in NSCLC in vitro and in vivo and suggest that it can be used in combination with EGFR TKIs to treat a subset of heregulin-overexpressing NSCLC patients.

ESR1 amplification in breast cancer by optimized RNase FISH: frequent but low-level and heterogeneous

Prevalence of ESR1 amplification in breast cancer is highly disputed and discrepancies have been related to different technical protocols and different scoring approaches. In addition, pre-mRNA artifacts have been proposed to influence outcome of ESR1 FISH analysis. We analyzed ESR1 gene copy number status combining an improved RNase FISH protocol with multiplex ligation-dependent probe amplification (MLPA) after laser microdissection. FISH showed a high prevalence of ESR1 gains and amplifications despite RNase treatment but MLPA did not confirm ESR1 copy number increases detected by FISH in more than half of cases. We suggest that the combination of the ESR1-specific intra-tumor heterogeneity and low-level copy number increase accounts for these discrepancies.

Gefitinib: re-emerging from the shadows

SUMMARY In the past decade, the identification of mutations in the EGFR gene and the sensitivity of activating mutations to EGF receptor–tyrosine kinase inhibitors has improved survival in a subset of non-small-cell lung cancer patients. Over 70% of patients with EGFR mutations have a response to gefitinib therapy. Gefitinib, a first-generation EGF receptor–tyrosine kinase inhibitor, is well tolerated and continues to be widely used. However, eventually most patients develop resistance to gefitinib. This article reviews the pharmacology of gefitinib and summarizes the clinical trials that have resulted in its current day indications.

Frequent overexpression of ErbB--receptor family members in brain metastases of non-small cell lung cancer patients

The ErbB receptor family has been implicated in brain metastases (BM) formation in various cancer types and specific targeted therapies are available. We investigated the overexpression of EGFR, HER2 and HER3 in BM of non-small cell lung cancer (NSCLC) patients to get a better insight on pathobiology of BM and potential drugable targets. We performed immunohistochemical analysis of EGFR, HER2 and HER3 on tissue microarrays of 131 NSCLC-BM. Fifty-one of 131 (38.9%) specimens were considered as positive for EGFR overexpression, 12/131 (9.2%) for HER2 and 27/131 (20.6%) for HER3 respectively. Sixty-nine of 131 (52.7%) of the cases showed overexpression of at least one marker. Four of 131 (3.1%) were positive for all three markers. Strong correlation was observed between HER2 and HER3 overexpression (p = 0.009; Chi-square test after Bonferroni-Holmes correction). No statistically significant correlation of EGFR, HER2 or HER3 overexpression with clinico-pathological parameters including overall survival times was observed. We observed overexpression of ErbB receptor family members, which represent established therapeutic targets in various primary tumours, in approximately half of NSCLC-BM. Further studies should investigate the role of the ErbB pathway in development of and as a therapeutic target in BM of NSCLC patients.

Oncogenes in non-small-cell lung cancer: emerging connections and novel therapeutic dynamics

Non-small-cell lung cancer is a heterogeneous disease that is difficult to treat. Through efforts to define the molecular mechanisms involved in lung oncogenesis, molecularly targeted approaches for patients with lung cancer have now reached the clinical arena. Despite elucidation of some molecular mechanisms of lung carcinogenesis, prognosis for patients remains poor. This Review aims to highlight the functional associations between key oncogenes that drive lung tumorigenesis and are distinct targetable molecules. Oncogenes are defined by acquisition of mutations, which results in a dominant gain-of-function of the targeted protein. In this situation, a single mutated allele is sufficient to induce malignant transformation. Importantly, tumours become addicted to particular genetic alterations that cause oncogene activation and the continued expression of the signalling. An increasing amount of evidence sustains the rationale for targeting of oncogenic pathways rather than a single oncogene. A clear priority for both researchers and clinicians is to better understand the complexity of biological networks underlying lung cancer pathogenesis. This paradigmatic shift in tailoring therapies should effectively improve outcomes for patients.

Decreased expression of C-erbB-2 and CXCR4 in breast cancer after primary chemotherapy

Background

Biological molecular markers such as proto-oncogene erbB-2 (HER-2/neu, c-erbB-2), the CXC chemokine receptor 4 (CXCR4), estrogen receptor (ER), Proliferating Cell Nuclear Antigen (PCNA), DNA topoisomerase II (topo II), P-glycoprotein (P-gp) and glutathione S-transferase (GST) were observed for changes after administration of neochemotherapy and whether these protein expression changes were correlated with response to chemotherapy.

Methods

Sixty-four patients with primary breast cancer who had undergone neo-adjuvant chemotherapy were enrolled in the present study. The expressions of C-erbB-2, CXCR4 and ER-α were measured by immunohistochemistry (IHC) on full tissue sections and on tissue microarrays (TMAs). PCNA, TopoII, P-gp and GST were measured by IHC on TMAs. On the other hand, CXCR4, C-erbB-2 and ER-α expressions were detected using western blot analysis to 16 pairs of fresh preoperative core biopsies. The final surgical specimens were obtained from patients with breast carcinoma who received neo-adjuvant chemotherapy and obtained a partial response (PR).

Results

Our data demonstrated that the levels of C-erbB-2, CXCR4 and ER-α in patients decreased after they received neo-adjuvant chemotherapy on full tissue sections and on TMAs. The PCNA level was down-regulated after receiving neo-adjuvant chemotherapy, and no significant change was observed for TopoII, P-gp and GST. The levels of C-erbB-2, CXCR4 and ER-α were also down-regulated after neo-adjuvant chemotherapy was administered, as detected by western blot. In addition, the change expressions of C-erbB-2 and CXCR4 in specimens tended to be correlated with pathological change to neo-adjuvant chemotherapy on full tissue sections and on TMAs in a Pearson chi-square analysis.

Conclusions

As demonstrated in our study, after breast cancer patients were treated with neo-adjuvant systemic therapy, decreased expressions of C-erbB2, ER-α and CXCR4 were observed. Down-regulated expressions of c-erbB-2 and CXCR4 may be a novel mechanism of chemotherapy; the changes of these objective markers may be useful in evaluating the clinical response of neo-adjuvant chemotherapy in breast cancer.

Genetic and biochemical alterations in non-small cell lung cancer

Despite significant advances in the detection and treatment of lung cancer, it causes the highest number of cancer-related mortality. Recent advances in the detection of genetic alterations in patient samples along with physiologically relevant animal models has yielded a new understanding of the molecular etiology of lung cancer. This has facilitated the development of potent and specific targeted therapies, based on the genetic and biochemical alterations present in the tumor, especially non-small-cell lung cancer (NSCLC). It is now clear that heterogeneous cell signaling pathways are disrupted to promote NSCLC, including mutations in critical growth regulatory proteins (K-Ras, EGFR, B-RAF, MEK-1, HER2, MET, EML-4-ALK, KIF5B-RET, and NKX2.1) and inactivation of growth inhibitory pathways (TP53, PTEN, p16, and LKB-1). How these pathways differ between smokers and non-smokers is also important for clinical treatment strategies and development of targeted therapies. This paper describes these molecular targets in NSCLC, and describes the biological significance of each mutation and their potential to act as a therapeutic target.

Identification of biomarkers in human head and neck tumor cell lines that predict for in vitro sensitivity to gefitinib

Potential biomarkers were identified for in vitro sensitivity to the epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor gefitinib in head and neck cancer. Gefitinib sensitivity was determined in cell lines, followed by transcript profiling coupled with a novel pathway analysis approach. Eleven cell lines were highly sensitive to gefitinib (inhibitor concentration required to give 50% growth inhibition [GI(50)] < 1 microM), three had intermediate sensitivity (GI(50) 1-7 microM), and six were resistant (GI(50) > 7 microM); an exploratory principal component analysis revealed a separation between the genomic profiles of sensitive and resistant cell lines. Subsequently, a hypothesis-driven analysis of Affymetrix data (Affymetrix, Inc., Santa Clara, CA, USA) revealed higher mRNA levels for E-cadherin (CDH1); transforming growth factor, alpha (TGF-alpha); amphiregulin (AREG); FLJ22662; EGFR; p21-activated kinase 6 (PAK6); glutathione S-transferase Pi (GSTP1); and ATP-binding cassette, subfamily C, member 5 (ABCC5) in sensitive versus resistant cell lines. A hypothesis-free analysis identified 46 gene transcripts that were strongly differentiated, seven of which had a known association with EGFR and head and neck cancer (human EGF receptor 3 [HER3], TGF-alpha, CDH1, EGFR, keratin 16 [KRT16], fibroblast growth factor 2 [FGF2], and cortactin [CTTN]). Polymerase chain reaction (PCR) and enzyme-linked immunoabsorbant assay analysis confirmed Affymetrix data, and EGFR gene mutation, amplification, and genomic gain correlated strongly with gefitinib sensitivity. We identified biomarkers that predict for in vitro responsiveness to gefitinib, seven of which have known association with EGFR and head and neck cancer. These in vitro predictive biomarkers may have potential utility in the clinic and warrant further investigation.

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.

Cytoskeleton alterations in melanoma: aberrant expression of cortactin, an actin-binding adapter protein, correlates with melanocytic tumor progression

Cortactin is a multidomain actin-binding protein important for the functions of cytoskeleton by regulating cortical actin dynamics. It is involved in a diverse array of basic cellular functions. Tumorigenesis and tumor progression involves alterations in actin cytoskeleton proteins. We sought to study the role of cortactin in melanocytic tumor progression using immunohistochemistry on human tissues. The results reveal quantitative differences between benign and malignant lesions. Significantly higher cortactin expression is found in melanomas than in nevi (P<0.0001), with levels greater in metastatic than in invasive melanomas (P<0.05). Qualitatively, tumor tissues often show aberrant cortactin localization at the cell periphery, corresponding to its colocalization with filamentous actin in cell cortex of cultured melanoma cells. This suggests an additional level of protein dysregulation. Furthermore, in patients with metastatic disease, high-level cortactin expression correlates with poor disease-specific survival. Our data, in conjunction with outcome data on several other types of human cancers and experimental data from melanoma cell lines, supports a potential role of aberrant cortactin expression in melanoma tumor progression and a rational for targeting key elements of actin-signaling pathway for developmental therapeutics in melanomas.

Chromosomal and genomic changes in lung cancer

Lung cancer is a complex spectrum of diseases characterized by extensive genomic instability, which can be detected among both histological subtypes and different foci within a tumor. Conventional and cutting edge investigative technologies have uncovered scores of genomic changes in individual specimens that have been used to characterize specific molecular subtypes. Oncogenes with predominant roles in lung cancer include EGFR, MYC and RAS family members, PIK3CA, NKX2-1 and ALK; tumor suppressor genes include TP53, RB1, CDKN2, and a cluster of genes mapped at 3p. MicroRNA regulators also have been linked to lung cancer. The functional role of the recurrent genomic changes in lung tumors has been explored, which has led to a better understanding of cell growth, differentiation and apoptotic pathways. Additionally, this knowledge has supported the development of novel therapeutics and translational tools for selection of patients for personalized therapy.

HER3 is required for the maintenance of neuregulin-dependent and -independent attributes of malignant progression in prostate cancer cells

HER3 (ERBB3) is a catalytically inactive pseudokinase of the HER receptor tyrosine kinase family, frequently overexpressed in prostate and other cancers. Aberrant expression and mutations of 2 other members of the family, EGFR and HER2, are key carcinogenic events in several types of tumors, and both are well- validated therapeutic targets. In this study, we show that HER3 is required to maintain the motile and invasive phenotypes of prostate (DU-145) and breast (MCF-7) cancer cells in response to the HER3 ligand neuregulin-1 (NRG-1), epidermal growth factor (EGF) and fetal bovine serum. Although MCF-7 breast cancer cells appeared to require HER3 as part of an autocrine response induced by EGF and FBS, the response of DU-145 prostate cancer cells to these stimuli, while requiring HER3, did not appear to involve autocrine stimulation of the receptor. DU-145 cells required the expression of HER3 for efficient clonogenicity in vitro in standard growth medium and for tumorigenicity in immunodeficient mice. These observations suggest that prostate cancer cells derived from tumors that overexpress HER3 are dependent on its expression for the maintenance of major attributes of neoplastic aggressiveness, with or without cognate ligand stimulation.

Pathogenesis of lung cancer signalling pathways: roadmap for therapies

Lung cancer is the major cancer killer worldwide, and 5-yr survival is extremely poor (<or=15%), accentuating the need for more effective therapeutic strategies. Significant advances in lung cancer biology may lead to customised therapy based on targeting specific genes and pathways. The main signalling pathways that could provide roadmaps for therapy include the following: growth promoting pathways (Epidermal Growth Factor Receptor/Ras/PhosphatidylInositol 3-Kinase), growth inhibitory pathways (p53/Rb/P14(ARF), STK11), apoptotic pathways (Bcl-2/Bax/Fas/FasL), DNA repair and immortalisation genes. Epigenetic changes in lung cancer contribute strongly to cell transformation by modifying chromatin structures and the specific expression of genes; these include DNA methylation, histone and chromatin protein modification, and micro-RNA, all of which are responsible for the silencing of tumour suppressor genes while enhancing expression of oncogenes. The genetic and epigenetic pathways involved in lung tumorigenesis differ between smokers and nonsmokers, and are tools for cancer diagnosis, prognosis, clinical follow-up and targeted therapies.

Determinants of response to epidermal growth factor receptor tyrosine kinase inhibition in squamous cell carcinoma of the head and neck

Dramatic responses to epidermal growth factor receptor (EGFR) tyrosine kinase (TK) inhibitors may be seen in non-small cell lung cancers (NSCLCs) with a sensitizing mutation of the EGFR TK domain. It is not known how to predict response in patients with squamous cell carcinoma of the head and neck (SCCHN), where EGFR TK mutations are less frequent and where response rates in unselected patients are disappointing. We have characterized the intrinsic sensitivity of a panel of 18 SCCHN cell lines to gefitinib, an EGFR TK inhibitor, and have investigated correlations between putative markers of response and intrinsic sensitivity. Induction of G1 arrest was only seen in cell lines with GI(50) < 1 microM. Expression of EGFR, by three techniques, correlated with sensitivity to gefitinib. ERB-B2 expression appeared to influence sensitivity to gefitinib but ERB-B3 expression did not. While EGFR tyrosine kinase mutations were not detected, EGFR gene amplification was confirmed by fluorescence in situ hybridization in the most sensitive cell line. The number of cytosine adenine dinucleotide repeats in intron 1 of the EGFR gene did not correlate with sensitivity. E-cadherin expression was detected in cell lines with a range of sensitivities, whereas amphiregulin was secreted predominantly by sensitive cell lines. MET expression was an independent predictor of sensitivity to gefitinib, although neither expression nor phosphorylation of insulin-like growth factor 1 receptor correlated with intrinsic resistance. Breast receptor kinase (BRK) was more highly expressed in the sensitive cell lines, but siRNA knockdown of neither BRK nor MET affected sensitivity. Our data suggest that overexpression of EGFR and multiple related cell surface receptors may be associated with sensitivity to gefitinib and that differences between our data and the literature highlight that biomarkers of response are tumour type- and cell line-dependent.

Theme: Oncology - Molecular mechanisms determining the efficacy of EGF receptor-specific tyrosine kinase inhibitors help to identify biomarker candidates

Non-small-cell lung cancer is a major subtype of lung cancer, which is the most common and fatal cancer in the world. Gefitinib (Iressa™) and later erlotinib (Tarceva™), specific tyrosine kinase inhibitors for EGF receptors (EGFRs), have been demonstrated to be effective for some non-small-cell lung cancer patients and used in clinics as pioneers of molecule-based targeted drugs for cancer. There has been an urgent need to develop biomarkers and to select appropriate patients who should benefit from treatment with these drugs because of the high sensitivity of target cancer cells. However, problems of acquired resistance after long-term treatment with these drugs have been recognized. Emerging evidence indicates that the efficacy of these drugs is partly dependent on somatic mutations in the EGFR. In this review, we summarize recent understandings of the molecular mechanisms that determine the efficacy of EGFR–tyrosine kinase inhibitors. Towards the end of this article, we discuss recent ongoing projects validating potential biomarkers and future prospects.

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

Background

Deregulation of EGFR signaling is common in non-small cell lung cancers (NSCLC) and this finding led to the development of tyrosine kinase inhibitors (TKIs) that are highly effective in a subset of NSCLC. Mutations of EGFR (mEGFR) and copy number gains (CNGs) of EGFR (gEGFR) and HER2 (gHER2) have been reported to predict for TKI response. Mutations in KRAS (mKRAS) are associated with primary resistance to TKIs.

Methodology/Principal Findings

We investigated the relationship between mutations, CNGs and response to TKIs in a large panel of NSCLC cell lines. Genes studied were EGFR, HER2, HER3 HER4, KRAS, BRAF and PIK3CA. Mutations were detected by sequencing, while CNGs were determined by quantitative PCR (qPCR), fluorescence in situ hybridization (FISH) and array comparative genomic hybridization (aCGH). IC50 values for the TKIs gefitinib (Iressa) and erlotinib (Tarceva) were determined by MTS assay. For any of the seven genes tested, mutations (39/77, 50.6%), copy number gains (50/77, 64.9%) or either (65/77, 84.4%) were frequent in NSCLC lines. Mutations of EGFR (13%) and KRAS (24.7%) were frequent, while they were less frequent for the other genes. The three techniques for determining CNG were well correlated, and qPCR data were used for further analyses. CNGs were relatively frequent for EGFR and KRAS in adenocarcinomas. While mutations were largely mutually exclusive, CNGs were not. EGFR and KRAS mutant lines frequently demonstrated mutant allele specific imbalance i.e. the mutant form was usually in great excess compared to the wild type form. On a molar basis, sensitivity to gefitinib and erlotinib were highly correlated. Multivariate analyses led to the following results:

 1. mEGFR and gEGFR and gHER2 were independent factors related to gefitinib sensitivity, in descending order of importance.

 2. mKRAS was associated with increased in vitro resistance to gefitinib.

Conclusions/Significance

Our in vitro studies confirm and extend clinical observations and demonstrate the relative importance of both EGFR mutations and CNGs and HER2 CNGs in the sensitivity to TKIs.

ErbB-3 expression is associated with E-cadherin and their coexpression restores response to gefitinib in non-small-cell lung cancer (NSCLC)

BACKGROUND

Epidermal growth factor receptor (EGFR) inhibitors are effective in a subset of patients with non-small-cell lung cancer (NSCLC). We previously showed that E-cadherin expression associates with gefitinib activity. Here, we correlated the expressions of ErbB-3 and E-cadherin in NSCLC tumors and cell lines, their effect on response to gefitinib, and induction of both by the histone deacetylase (HDAC) inhibitors vorinostat and SNDX-275.

METHODS

Real-time RT-PCR was carried out on RNA isolated from 91 fresh-frozen NSCLC samples and from 21 NSCLC lines. Protein expression was evaluated with western blot and flow cytometry. Apoptosis was assessed using vibrant apoptosis assay.

RESULTS

Expressions of E-cadherin and ErbB-3 correlated significantly in primary tumors (r = 0.38, P < 0.001) and in cell lines (r = 0.88, P < 0.001). Cotransfection of ErbB-3 and E-cadherin in a gefitinib-resistant cell line showed enhanced apoptotic response to gefitinib. vorinostat and SNDX-275 induced ErbB-3 and E-cadherin in gefitinib-resistant cell lines. When gefitinib-resistant lines were treated with vorinostat and gefitinib, synergistic effects were detected in four of the five lines tested.

CONCLUSION

ErbB-3 and E-cadherin are coexpressed and induced by HDAC inhibitors. For tumors with low ErbB-3 and E-cadherin expressions, the combination of HDAC and EGFR-tyrosine kinase inhibitors increased expression of both genes and produced more than additive apoptotic effect.

EGFR mutations and HER2/3 protein expression and clinical outcome in Chinese advanced non-small cell lung cancer patients treated with gefitinib

BACKGROUND

To assess the role of various epidermal growth factor receptor (EGFR) mutations and HER2/3 protein expression as predictive markers of responsiveness to gefitinib therapy in Chinese patients with advanced non-small cell lung cancer (NSCLC).

METHODS

A total of 106 Chinese NSCLC patients who had failed at least one chemotherapy regimen received gefitinib 250 mg once daily. All the 106 tumors from these patients were screened for mutations in the EGFR exons 18-24, and 84 tumors were studied by immunohistochemistry for HER2/3 expression and correlated with clinical treatment outcome.

RESULTS

Patients with EGFR mutations had a significantly higher overall response rate (ORR), longer time to progression (TTP) and overall survival (OS) compared with those with wild-type receptor. No difference in ORR was observed between patients with exon 19 deletion and patients with other EGFR mutations. ORR in HER2-positive patients was significantly higher than in the HER2-negative group, irrespective of EGFR mutational status, and a trend for better ORR was observed for HER3-positive patients. HER2 and HER3 expression levels were not associated with any difference in terms of TTP and OS. Nevertheless, when considering the subgroups of non-responders to gefitinib, median TTP in patients with mutated EGFR was significantly longer than in those with no mutations (8.0 vs. 3.0 months, P = 0.0065). EGFR-mutated patients had no significant difference in ORR, TTP and OS according to HER2 and/or HER3 expression.

CONCLUSIONS

EGFR mutations are effective predictors for gefitinib efficacy in Chinese patients with advanced NSCLC. HER2 and HER3 expression does not provide any additional information for selecting patients most likely to benefit from gefitinib treatment.

HER3 is a determinant for poor prognosis in melanoma

PURPOSE

The epidermal growth factor receptor family member HER3 is overexpressed in diverse human cancers and has been associated with poor prognosis in breast, lung, and ovarian cancer. However, the relevance of HER3 with regard to its prognostic significance and function in primary melanoma and metastases remains largely elusive.

EXPERIMENTAL DESIGN

HER3 protein expression was analyzed immunohistochemically using tissue microarrays of 130 primary melanoma and 87 metastases relative to established clinical variables. The possibility of an influence of HER3 on melanoma cell proliferation, migration, invasion, and chemotherapy-induced apoptosis was studied in human melanoma cell lines.

RESULTS

We show that HER3 is frequently expressed in malignant melanoma and metastases at elevated levels. High HER3 expression may serve as a prognostic marker because it correlates with cell proliferation, tumor progression, and reduced patient survival. Suppression of HER3 expression by RNA interference reduces melanoma cell proliferation, migration, and invasion in vitro. In addition, down-regulation of HER3 synergistically enhances dacarbazine-induced apoptosis. Moreover, monoclonal antibodies specific for the extracellular portion of HER3 efficiently block heregulin-induced proliferation, migration, and invasion of melanoma cell lines.

CONCLUSION

Our results provide novel insights into the role of HER3 in melanoma and point out new possibilities for therapeutic intervention.

The ERBB3 receptor in cancer and cancer gene therapy

ERBB3, a member of the epidermal growth factor receptor (EGFR) family, is unique in that its tyrosine kinase domain is functionally defective. It is activated by neuregulins, by other ERBB and nonERBB receptors as well as by other kinases, and by novel mechanisms. Downstream it interacts prominently with the phosphoinositol 3-kinase/AKT survival/mitogenic pathway, but also with GRB, SHC, SRC, ABL, rasGAP, SYK and the transcription regulator EBP1. There are likely important but poorly understood roles for nuclear localization and for secreted isoforms. Studies of ERBB3 expression in primary cancers and of its mechanistic contributions in cultured cells have implicated it, with varying degrees of certainty, with causation or sustenance of cancers of the breast, ovary, prostate, certain brain cells, retina, melanocytes, colon, pancreas, stomach, oral cavity and lung. Recent results link high ERBB3 activity with escape from therapy targeting other ERBBs in lung and breast cancers. Thus a wide and centrally important role for ERBB3 in cancer is becoming increasingly apparent. Several approaches for targeting ERBB3 in cancers have been tested or proposed. Small inhibitory RNA (siRNA) to ERBB3 or AKT is showing promise as a therapeutic approach to treatment of lung adenocarcinoma.

Acquired resistance to erlotinib in A-431 epidermoid cancer cells requires down-regulation of MMAC1/PTEN and up-regulation of phosphorylated Akt

Erlotinib (Tarceva), an epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor, has clinical activity in advanced lung cancer, but disease that initially responds to erlotinib eventually progresses. The mechanism of this acquired resistance is unclear. We established two erlotinib-resistant pools of A-431 cells, a well-characterized epidermoid cancer cell line that constitutively overexpresses EGFR and is sensitive to erlotinib, by continuous exposure to erlotinib over a 6-month period. The extent of EGFR gene amplification or mutation of the EGFR tyrosine kinase domain was not altered in the resistant cells. Intracellular erlotinib concentrations, determined by liquid chromatography-tandem mass spectrometry, were almost the same in all three cell lines. Immunoprecipitation with EGFR antibody followed by detection with phosphotyrosine antibody revealed that erlotinib effectively reduced EGFR phosphorylation in both parental cells and resistant cells. Erlotinib induced mutated in multiple advanced cancers 1/phosphatase and tensin homologue (MMAC1/PTEN) and suppressed phosphorylated Akt (Ser(473)) but not in the erlotinib-resistant cells. Overexpression of MMAC1/PTEN by transfection with Ad.MMAC1/PTEN or by pharmacologic suppression of Akt activity restored erlotinib sensitivity in both resistant pools. Further, transfection of parental A-431 cells with constitutively active Akt was sufficient to cause resistance to erlotinib. We propose that acquired erlotinib resistance associated with MMAC1/PTEN down-regulation and Akt activation could be overcome by inhibitors of signaling through the phosphatidylinositol 3-kinase pathway.

Mutations of the epidermal growth factor receptor gene and related genes as determinants of epidermal growth factor receptor tyrosine kinase inhibitors sensitivity in lung cancer

Recent discovery of mutations in the tyrosine kinase domain of the epidermal growth factor receptor (EGFR) gene in lung adenocarcinoma greatly stimulated biomarker research on predictive factors for EGFR tyrosine kinase inhibitors (TKI), such as gefitinib and erlotinib. Although patients with activating mutations of the EGFR generally respond to EGFR TKIs very well, it is natural to assume that there is no sole determinant, considering great complexity and redundancy of the EGFR pathway. Subsequently, roles of different types of EGFR mutations or mutations of genes that are members of the EGFR pathway such as KRAS and HER2 have been evaluated. In this review, we summarize the recent findings about how mutations of the EGFR and related genes affect sensitivity to EFGR-TKIs. We also discuss molecular mechanisms of acquired resistance to EGFR-TKIs that is almost inevitable in EGFR-TKI therapy. The door for genotype-based treatment of lung cancer is beginning to open, and through these efforts, it will be possible to slow the progression of lung cancer and eventually, to decrease mortality from lung cancer.

ErbB3 mRNA expression correlated with specific clinicopathologic features of Japanese lung cancers

BACKGROUND

ErbB3 is a member of the epidermal growth factor receptor (EGFR) family of tyrosine kinase. A previous report has suggested that overexpression of ErbB3 protein was associated with lung cancer recurrence. Other reports suggested that high ErbB3 protein expression was associated with shorter survival in advanced non-small-cell lung carcinomas (NSCLC). The relationship between the erbB3 mRNA expression and EGFR mutation has not been reported. In this study, we have investigated the erbB3 mRNA levels in reference to clinicopathologic data and EGFR mutation status in Japanese lung cancer specimens.

MATERIALS AND METHODS

This study included 192 surgically removed NSCLC cases operated at Nagoya City University Hospital. The erbB3 mRNA levels were quantified by real-time polymerase chain reaction using LightCycler (Roche Molecular Biochemicals, Mannheim, Germany).

RESULTS

The erbB3/glyceraldehydes-3-phosphatate dehydrogenase levels were significantly higher in female than in male (P < 0.0001), higher in nonsmoker than in smoker (P = 0.0007), higher in adenocarcinoma than in other types of lung cancers (P < 0.0001), and higher in well-differentiated than in less-differentiated subtypes (P = 0.0304). The erbB3/glyceraldehydes-3-phosphatate dehydrogenase levels were significantly higher in patients with EGFR gene mutation than in patients without mutation (P = 0.0124).

CONCLUSIONS

The present study suggests that increased expression of erbB3 may play an additional role in NSCLC especially in female, nonsmoker, adenocarcinoma, and with EGFR gene mutation. Further studies on large sample sizes would help to determine if erbB3 expression is a clinically useful tool to further define patients who will benefit from EGFR TKIs.

EGFR and HER2 gene copy number and response to first-line chemotherapy in patients with advanced non-small cell lung cancer (NSCLC)

BACKGROUND

A critical point in designing clinical trials comparing chemotherapy with epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) in patients with non-small cell lung cancer (NSCLC) is the expected benefit with standard chemotherapy in presence of biological features indicative of TKI sensitivity. The aim of this study was to assess whether EGFR and HER2 gene copy number and Akt activation are associated with response to first-line chemotherapy.

METHODS

Tumor samples from 190 patients with NSCLC were analyzed. EGFR and HER2 gene copy number were evaluated by fluorescence in situ hybridization in 185 and 184 cases, respectively. Akt activation was assessed by immunohistochemistry (n = 176). Additional biomarkers included EGFR DNA sequencing (n = 65), and EGFR immunohistochemistry (n = 185).

RESULTS

Response rate was not associated with EGFR, HER2, and P-Akt status, irrespective of the method used for biomarker assessment. Among patients with EGFR gene mutations, response to chemotherapy was observed only in individuals with exon 19 deletion (response rate: 46.6% versus 0%, p = 0.02). Among the 190 patients analyzed, 123 received a treatment with a TKI as second- or third-line therapy. When assessed by fluorescence in situ hybridization or DNA sequencing, EGFR-positive patients seemed to be more sensitive to TKIs than to chemotherapy in terms of response rate and time to progression, whereas in EGFR-negative patients, response rate and time to progression favored chemotherapy.

CONCLUSION

This study suggested that EGFR expression and gene copy number, HER2 gene copy number, and P-Akt expression are not associated with response to first-line chemotherapy in NSCLC. Prospective phase III trials should compare standard chemotherapy with a TKI in selected NSCLC.

A translational view of the molecular pathogenesis of lung cancer

Molecular genetic studies of lung cancer have revealed that clinically evident lung cancers have multiple genetic and epigenetic abnormalities, including DNA sequence alterations, copy number changes, and aberrant promoter hypermethylation. Together, these abnormalities result in the activation of oncogenes and inactivation of tumor-suppressor genes. In many cases these abnormalities can be found in premalignant lesions and in histologically normal lung bronchial epithelial cells. Findings suggest that lung cancer develops through a stepwise process from normal lung epithelial cells towards frank malignancy, which usually occurs as a result of cigarette smoking. Lung cancer has a high morbidity because it is difficult to detect early and is frequently resistant to available chemotherapy and radiotherapy. New, rationally designed early detection, chemoprevention, and therapeutic strategies based on the growing understanding of the molecular changes important to lung cancer are under investigation. For example, methylated tumor DNA sequences in sputum or blood are being investigated for early detection screening, and new treatments that specifically target molecules such as vascular endothelial growth factor and the epidermal growth factor receptor are becoming available. Meanwhile, global gene expression signatures from individual tumors are showing potential as prognostic and therapeutic indicators, such that molecular typing of individual tumors for therapy selection is not far away. Finally, the recent development of a model system of immortalized human bronchial epithelial cells, along with a paradigm shift in the conception of cancer stem cells, promises to improve the situation for patients with lung cancer. These advances highlight the translation of molecular discoveries on lung cancer pathogenesis from the laboratory to the clinic.

The impact of epidermal growth factor receptor gene status on gefitinib-treated Japanese patients with non-small-cell lung cancer

We investigated the relationships between genetic factors and clinical outcome in Japanese non-small-cell lung cancer (NSCLC) patients treated with gefitinib. Ninety-eight NSCLC patients who had been treated with gefitinib, were screened for mutations in epidermal growth factor receptor (EGFR) exons 18-21, KRAS exon2, and polymorphisms including the CA simple sequence repeat in intron1 (CA-SSR1) and single nucleotide polymorphisms in the promoter region (-216G/T and -191C/A), using a PCR-based assay and direct sequencing. The EGFR copy number status was also evaluated using a fluorescence in situ hybridization assay. EGFR and KRAS mutations were found in 38 (38.8%) and 8 (8.2%) of the 98 patients, respectively. A high EGFR copy number status was identified in 31 (41.3%) of the 75 assessable patients. Drug-sensitive EGFR mutations limited to exon19 deletions and L858R were independent predictive factors of a stronger sensitivity to gefitinib (p = 0.0002), the overall survival (OS) (p = 0.0036), and prolonged progression-free survival (PFS) (p < 0.0001). The EGFR copy number status was not related to a sensitivity to gefitinib and prolonged OS and PFS. Regarding polymorphisms, patients with a short CA-SSR1 showed a prolonged OS as compared with those with a long length in patients with a drug-sensitive EGFR mutation, although this difference was not significant (p = 0.13). Thus, drug-sensitive EGFR mutations predict a favorable clinical outcome and a high EGFR copy number may not be related to clinical benefits in gefitinib-treated Japanese patients with NSCLC. Our findings also suggest that the CA-SSR1 length may influence the clinical outcome in patients with a drug-sensitive EGFR mutation.

Epidermal growth factor receptor mutations in lung cancer

The development and clinical application of inhibitors that target the epidermal growth factor receptor (EGFR) provide important insights for new lung cancer therapies, as well as for the broader field of targeted cancer therapies. We review the results of genetic, biochemical and clinical studies focused on somatic mutations of EGFR that are associated with the phenomenon of oncogene addiction, describing 'oncogenic shock' as a mechanistic explanation for the apoptosis that follows the acute treatment of susceptible cells with kinase inhibitors. Understanding the genetic heterogeneity of epithelial tumours and devising strategies to circumvent their rapid acquisition of resistance to targeted kinase inhibitors are essential to the successful use of targeted therapies in common epithelial cancers.

Epidermal growth factor receptor tyrosine kinase inhibitors for the treatment of non-small-cell lung cancer: results and open issues

The medical treatment of non-small-cell lung cancer (NSCLC) has progressively changed since the introduction of "targeted therapy". The development of one of these molecular drug categories, e. g., the epidermal growth factor receptor (EGFR) tyrosine-kinase (TK) selective inhibitors, such as the orally active gefitinib and erlotinib, offers an interesting new opportunity. The clinical response rates obtained with their employment in unselected patient populations only account for approximately 10%. Because of this, over the last two years numerous studies have been performed in order to identify the patient subsets that could better benefit from these agents. Not only patient characteristics and clinical-pathological features, such as never-smoking status, female gender, East Asian origin, adenocarcinoma histology, bronchioloalveolar subtype, but also molecular findings, such as somatic mutations in the EGFR gene, emerge as potentially useful prognostic and predictive factors in advanced NSCLC. Further, specifically designed clinical trials are still needed to completely clarify these and other open issues that are reviewed in this paper, in order to clarify all the interesting findings available in the clinical practice.

Which biomarker predicts benefit from EGFR-TKI treatment for patients with lung cancer?

Subsets of patients with non-small cell lung cancer respond remarkably well to small molecule tyrosine kinase inhibitors (TKI) specific for epidermal growth factor receptor (EGFR) such as gefitinib or erlotinib. In 2004, it was found that EGFR mutations occurring in the kinase domain are strongly associated with EGFR-TKI sensitivity. However, subsequent studies revealed that this relationship was not perfect and various predictive markers have been reported. These include EGFR gene copy numbers, status of ligands for EGFR, changes in other HER family genes or molecules downstream to EGFR including KRAS or AKT. In this review, we would like to review current knowledge of predictive factors for EGFR-TKI. As all but one phase III trials failed to show a survival advantage of the treatment arm involving EGFR-TKIs, it is necessary to select patients by these biomarkers in future clinical trials. Through these efforts, it would be possible to individualise EGFR-TKI treatment for patients suffering from lung cancer.

Epidermal Growth Factor Receptor Activation: How Exon 19 and 21 Mutations Changed Our Understanding of the Pathway

The discovery of epidermal growth factor receptor (EGFR) mutations in never-smokers has been the most relevant finding ever in non–small cell lung cancer. When patients whose tumors bear the sensitizing mutations are treated with the tyrosine kinase inhibitors gefitinib or erlotinib, we witness response rates and durations never before reported, including complete responses. At the same time, the presence of EGFR mutations has raised numerous new questions, tantalizing data, and new challenges for treatment. This is particularly true as we try to generalize the findings in lung cancer to other malignancies. The indiscriminate use of gefitinib or erlotinib in the general lung cancer population results in meager survival benefit for patients. Similarly, the tyrosine kinase inhibitors have limited activity in a variety of tumor types with EGFR overexpression. This has led to the question of whether EGFR remains a viable target in patients other than those whose tumors contain mutations, and whether the modest activity of cetuximab in colorectal cancer and head and neck cancer represents all that we can expect from inhibition of this pathway in the absence of mutation. Mechanisms of pathway activation other than mutation have been discovered in recent years, and include overexpression mediated by gene amplification or by amplification of a dinucleotide repeat in the EGFR promoter, mutation of an extracellular region on EGFR generating a mutant protein termed EGFRvIII, and enhanced signaling due to heterodimerization with other members of the EGFR family, particularly overexpression of HER2/HER3. The extent to which these paths to EGFR activation will confer sensitivity to the tyrosine kinase inhibitors or to EGFR monoclonal antibodies is being explored. Thus far, published clinical data suggest that there is little room for the administration of gefitinib or erlotinib in the absence of EGFR mutations. The five articles in this edition of CCR Focus will address the various mechanisms of EGFR pathway activation and provide insight into the potential for translation into clinical relevance.

Inactivation of Akt by the epidermal growth factor receptor inhibitor erlotinib is mediated by HER-3 in pancreatic and colorectal tumor cell lines and contributes to erlotinib sensitivity

Signaling through the receptor for epidermal growth factor receptor (EGFR) is frequently deregulated in solid tumors. Erlotinib (Tarceva, OSI-774, OSI Pharmaceuticals, Inc., Melville, NY) is a low molecular weight, orally bioavailable inhibitor of the EGFR that has been approved for both non-small cell lung cancer and pancreatic cancers. Previous studies have indicated that sensitivity to EGFR antagonists correlated with HER-3 signaling for non-small cell lung cancer. Herein, we have sought to understand the signaling pathways that mediate erlotinib sensitivity for pancreatic and colorectal cancers. In a panel of 12 pancreatic tumor cell lines, we find that EGFR is coexpressed with HER-3 in all cell lines sensitive to erlotinib but not in insensitive cell lines. Erlotinib can block HER-3 phosphorylation in these sensitive cell lines, suggesting that HER-3 is transactivated by EGFR. Knockdown of HER-3 in BxPC3, an erlotinib-sensitive pancreatic tumor cell line, results in inhibition of the phosphorylation for both Akt and S6 and is associated with a decrease in cell proliferation and reduced sensitivity to erlotinib. Therefore, EGFR transactivation of HER-3 mediates Akt signaling and can contribute to erlotinib sensitivity for pancreatic tumors. We extended our analysis to a panel of 13 colorectal tumor cell lines and find that, like pancreatic, HER-3 is coexpressed with EGFR in the most erlotinib-sensitive cell lines but not in erlotinib-insensitive cell lines. These studies suggest that HER-3 could be used as a biomarker to select patients who are most likely to respond to erlotinib therapy.

Lung cancer genetics and pharmacogenomics

Epidermal growth factor receptor (EGFR)-targeted therapies have demonstrated remarkable success in a small subset of non-small cell lung cancer patients. The mechanism of response has been an area of active research, with somatic mutation in a number of genes in the EGFR signal transduction pathway and copy number alterations of genes of the EGFR family as candidates contributing towards response. Continuing studies should help determine an appropriate biomarker or combination of biomarkers that can be used to predict response to this class of therapy.