Combinatory effect of BRCA1 and HERC2 expression on outcome in advanced non-small-cell lung cancer.

BACKGROUND: BRCA1 is a main component of homologous recombination and induces resistance to platinum in preclinical models. It has been studied as a potential predictive marker in lung cancer. Several proteins modulate the function of BRCA1. The E3 ubiquitin ligase HERC2 facilitates the assembly of the RNF8-UBC13 complex to recruit BRCA1 to DNA damage sites. The combined analysis of multiple components of the pathway leading to the recruitment of BRCA1 at DNA damage sites has the potentiality to improve the BRCA1 predictive model. METHODS: We retrospectively analyzed 71 paraffin-embedded tumor samples from advanced non-small-cell lung cancer patients treated with first-line platinum based chemotherapy and measured the mRNA expression levels of BRCA1, RNF8, UBC13 and HERC2 using real-time PCR. The mRNA expression was categorized using median value as cut-off point. RESULTS: The median progression-free survival of all 71 patients was 7.2 months whereas the median overall survival of the study population was 10.7 months. Among patients with low BRCA1 expression, the median PFS was 7.4 months in the presence of low HERC2 levels and 5.9 months for patients expressing high HERC2 levels (p = 0.01). The median OS was 15.3 months for patients expressing low levels of both genes and 7.4 months for those with low BRCA1 but high HERC2 (p = 0.008). The multivariate analysis showed that among patients with Eastern Cooperative Oncology Group performance status 0-1, the combined low expression of both BRCA1 and HERC2 clearly reduced the risk of progression (p = 0.03) and of death (p = 0.004). CONCLUSIONS: These findings confirm the potentiality of integrated DNA repair components analysis in predicting the sensitivity to platinum in lung cancer. The study indicates a predictive role for HERC2 mRNA expression and paves the way for further refinement of the BRCA1 predictive model.

Plasma mRNA expression levels of BRCA1 and TS as potential predictive biomarkers for chemotherapy in gastric cancer.

OBJECTIVE: Personalized chemotherapy based on predictive biomarkers can maximize efficacy. However, tumor tissue obtained at the time of initial diagnosis will not reflect genetic alterations observed at the time of disease progression. We have examined whether plasma mRNA levels can be a surrogate for tumor levels in predicting chemosensitivity. METHODS: In 150 gastric cancer patients, mRNA levels of BRCA1 and TS were assessed in plasma and paired tumor tissue. The Mann-Whitney U-test was used to compare mRNA expression levels between tumor samples exhibiting in vitro sensitivity or resistance to docetaxel and pemetrexed. All statistical tests were two-sided. RESULTS: There were significant correlations between plasma and tumor mRNA levels of BRCA1 (rho = 0.696, P < 0.001) and TS (rho = 0.620, P < 0.001). BRCA1 levels in plasma (docetaxel-sensitive: 1.25; docetaxel-resistant: 0.50, P < 0.001) and tumor (docetaxel-sensitive: 8.81; docetaxel-resistant: 4.88, P < 0.001) were positively associated with docetaxel sensitivity. TS levels in plasma (pemetrexed-sensitive: 0.90; pemetrexed-resistant: 1.82, P < 0.001) and tumor (pemetrexed-sensitive: 6.56; pemetrexed-resistant: 16.69, P < 0.001) were negatively associated with pemetrexed sensitivity. CONCLUSIONS: Plasma mRNA expression levels mirror those in the tumor and may have a promising role as potential predictive biomarkers for chemotherapy.

The impact of EGFR T790M mutations and BIM mRNA expression on outcome in patients with EGFR-mutant NSCLC treated with erlotinib or chemotherapy in the randomized phase III EURTAC trial.

PURPOSE: Concomitant genetic alterations could account for transient clinical responses to tyrosine kinase inhibitors of the EGF receptor (EGFR) in patients harboring activating EGFR mutations. EXPERIMENTAL DESIGN: We have evaluated the impact of pretreatment somatic EGFR T790M mutations, TP53 mutations, and Bcl-2 interacting mediator of cell death (BCL2L11, also known as BIM) mRNA expression in 95 patients with EGFR-mutant non-small-cell lung cancer (NSCLC) included in the EURTAC trial (trial registration: NCT00446225). RESULTS: T790M mutations were detected in 65.26% of patients using our highly sensitive method based on laser microdissection and peptide-nucleic acid-clamping PCR, which can detect the mutation at an allelic dilution of 1 in 5,000. Progression-free survival (PFS) to erlotinib was 9.7 months for those with T790M mutations and 15.8 months for those without, whereas among patients receiving chemotherapy, it was 6 and 5.1 months, respectively (P < 0.0001). PFS to erlotinib was 12.9 months for those with high and 7.2 months for those with low/intermediate BCL2L11 expression levels, whereas among chemotherapy-treated patients, it was 5.8 and 5.5 months, respectively (P = 0.0003). Overall survival was 28.6 months for patients with high BCL2L11 expression and 22.1 months for those with low/intermediate BCL2L11 expression (P = 0.0364). Multivariate analyses showed that erlotinib was a marker of longer PFS (HR = 0.35; P = 0.0003), whereas high BCL2L11 expression was a marker of longer PFS (HR = 0.49; P = 0.0122) and overall survival (HR = 0.53; P = 0.0323). CONCLUSIONS: Low-level pretreatment T790M mutations can frequently be detected and can be used for customizing treatment with T790M-specific inhibitors. BCL2L11 mRNA expression is a biomarker of survival in EGFR-mutant NSCLC and can potentially be used for synthetic lethality therapies.

Signaling pathways modulating dependence of lung cancer on mutant epidermal growth factor receptor and mechanisms of intrinsic and acquired resistance to tyrosine kinase inhibitors.

A new era in lung cancer targeted therapy arrived with the discovery of a subset of lung adenocarcinomas harboring activating mutations of the epidermal growth factor receptor (EGFR), whose tyrosine kinase activity can be selectively blocked by small molecule pharmaceuticals referred as tyrosine kinase inhibitors (TKIs). This was the starting point for a less toxic and more effective treatment strategy for a disease that has historically presented as chemorefractory and highly lethal. In spite of this progress, only 80% of the patients treated with this class of compounds will obtain a clinical benefit, of variable magnitude and duration, with remaining patients being primarily refractory to the treatment. Moreover, responding tumors will eventually develop acquired resistance to TKIs and progress to more advanced stages. In this review we summarize the current knowledge with regard to the mechanisms leading to tumor regression and the modifiers of this primary response that determine significant variability in sensitivity of tumors harboring EGFR activating mutations, ranging from complete remission to primary refractoriness. We also analyze the mechanisms of secondary resistance and the strategies the scientific community is exploring in order to overcome these barriers.

The predictive value of 53BP1 and BRCA1 mRNA expression in advanced non-small-cell lung cancer patients treated with first-line platinum-based chemotherapy.

Platinum-based chemotherapy is the standard first-line treatment for non-oncogene- addicted non-small cell lung cancers (NSCLCs) and the analysis of multiple DNA repair genes could improve current models for predicting chemosensitivity. We investigated the potential predictive role of components of the 53BP1 pathway in conjunction with BRCA1. The mRNA expression of BRCA1, MDC1, CASPASE3, UBC13, RNF8, 53BP1, PIAS4, UBC9 and MMSET was analyzed by real-time PCR in 115 advanced NSCLC patients treated with first-line platinum-based chemotherapy. Patients expressing low levels of both BRCA1 and 53BP1 obtained a median progression-free survival of 10.3 months and overall survival of 19.3 months, while among those with low BRCA1 and high 53BP1 progression-free survival was 5.9 months (P less than 0.0001) and overall survival was 8.2 months (P=0.001). The expression of 53BP1 refines BRCA1-based predictive modeling to identify patients most likely to benefit from platinum-based chemotherapy.

Erlotinib resistance in lung cancer cells mediated by integrin ß1/Src/Akt-driven bypass signaling.

EGF receptor (EGFR) kinase inhibitors, including gefitinib and erlotinib, exert potent therapeutic efficacy in non-small cell lung cancers harboring EGFR-activating mutations. However, most patients ultimately develop resistance to these drugs. Here, we report a novel mechanism of acquired resistance to EGFR tyrosine kinase inhibitors and the reversal of which could improve clinical outcomes. In erlotinib-resistant lung cancer cells harboring activating EGFR mutations that we established, there was increased expression of Src, integrin ß1, α2, and α5 along with enhanced cell adhesion activity. Interestingly, RNAi-mediated silencing of integrin ß1 restored erlotinib sensitivity and reduced activation of Src and Akt after erlotinib treatment. Furthermore, Src silencing inhibited Akt phosphorylation and cell growth, with this inhibitory effect further augmented by erlotinib treatment. Increased expression of integrin ß1, α5, and/or α2 was also observed in refractory tumor samples from patients with lung cancer treated with erlotinib and/or gefitinib. Together, our findings identify the integrin ß1/Src/Akt signaling pathway as a key mediator of acquired resistance to EGFR-targeted anticancer drugs.

BRCA1, LMO4, and CtIP mRNA expression in erlotinib-treated non-small-cell lung cancer patients with EGFR mutations.

INTRODUCTION: Lung adenocarcinoma patients harboring EGFR activating mutations attain improved progression-free survival (PFS) with treatment with epidermal growth factor receptor tyrosine kinase inhibitors. However, patients ultimately relapse, indicating that other genetic factors could influence outcome in such patients. We hypothesized that PFS could be influenced by the expression of genes in DNA repair pathways. METHODS: We examined the mRNA expression of C terminus-binding protein-interacting protein and Lin11, Isl-1, and Mec-3 domain only 4 (LMO4) in pretreatment tumor samples from 91 erlotinib-treated advanced non-small-cell lung cancer patients with EGFR mutations in whom breast cancer gene 1 (BRCA1) expression and the concomitant presence of the EGFR T790M mutation had previously been assessed. Gene expression was analyzed by polymerase chain reaction, using ß-actin as endogenous gene. Results were correlated with PFS and overall survival. RESULTS: In patients with low LMO4 levels, PFS was 13 months, whereas it was not reached for those with high LMO4 levels (p = 0.03). In patients with low levels of both BRCA1 and LMO4, PFS was 19 months whereas it was not reached in those with low BRCA1 and high LMO4 mRNA levels (p = 0.04). In patients with high BRCA1 and low LMO4 levels, PFS was 8 months, whereas it was 18 months in those with high levels of both genes (p = 0.03). CONCLUSIONS: Low BRCA1 and high LMO4 levels were associated with longer PFS to erlotinib. Baseline assessment of BRCA1 and LMO4 mRNA expression can help predict outcome to erlotinib.

KRAS mutations in lung cancer.

Epidermal growth factor receptor (EGFR) gene mutations and increased EGFR copy numbers have been associated with a favorable response to EGFR tyrosine kinase inhibitors (TKI) in patients with non-small-cell lung cancer (NSCLC), and several markers have been identified that predict response to treatment. Lung adenocarcinomas also harbor activating mutations in the downstream GTPase, v-Ki-ras2 Kirsten rat sarcoma viral oncogene (KRAS), and mutations in EGFR and KRAS appear to be mutually exclusive. Even though KRAS mutations were identified in NSCLC tumors more than 20 years ago, we have only just begun to appreciate the clinical value of determining KRAS tumor status. Recent studies indicate that patients with mutant KRAS tumors fail to benefit from adjuvant chemotherapy and do not respond to EGFR inhibitors. There is a clear need for therapies specifically developed for patients with KRAS-mutant NSCLC. In this review, we summarize the clinical and pathologic characteristics of patients with NSCLC and with KRAS mutations, describe work that explores the predictive and prognostic influence of KRAS mutations, and provide an overview of the "synthetic lethal" interactions and current approaches to targeting KRAS-mutant NSCLC.

CK-coated magnetic-based beads as a tool to isolate circulating tumor cells (CTCs) in human tumors.

Circulating tumor cells (CTCs) can be detected in the blood of many cancer patients and play a key role in metastasis. In addition, after the development of technologies with the necessary sensitivity and reproducibility, the diagnostic potential of these cells is being actively explored. Recently, the U.S. Food and Drug Administration has approved the CellSearch(®) System, based on magnetic beads coated with epithelial cell-adhesion molecule (EpCAM) antibody. Despite its usefulness, this system can miss CTCs that lose epithelial antigens due to the epithelial-mesenchymal transition and, in the case of advanced NSCLC, CTCs positivity can be demonstrated only in 30-50% of patients. In an effort to overcome these drawbacks, new methods are being developed. In this study, we have evaluated CK-coated beads as a system to isolate CTCs from lung cancer patients in the clinical setting, and have evaluated if they can be a useful source of material for genetic testing. We were able to identify CTCs in 17 of the 30 patients included in the study (57%), with a range of 1 to 7 cells. In two of them, we found only CTCs with an EMT pattern. CTC positivity seemed to correlate with the clinical history of the malignancy. CTCs could be detected in more than 80% of stage III-IV lung cancer patients at presentation or in blood samples taken immediately after surgery. The percentage dropped to 13% in patients responding to chemotherapy or TKIs, raising again to 57% after tumor progression. Finally, we tested the CTCs isolated from 8 patients for EGFR and k-ras mutations, but gene amplification was successful only in the 3 patients with 4 or more CTCs.

Comprehensive molecular screening: from the RT-PCR to the RNA-seq.

Up to now, the analysis of the mRNA expression in tumoral and non-tumoral has been conducted via RT-PCR. It is considered to be the gold standard for measuring the number of copies of specific cDNA targets. The application of RT-PCR has demonstrated that levels of RNA transcripts stratify patients and predict outcomes in a variety of diseases, providing the basis for several important clinical tests. However, the inherent variability in the quality of any quantitative PCR data makes it difficult to replicate and the analysis is time consuming in the laboratory for the analysis of one gene. Moreover, comparing expression levels across different experiments is often difficult and can require complicated normalization methods. Many techniques have been developed over the years but without good clinical applications. A new, simple and effective way to measure transcriptome composition and to discover new exons or genes is by the RNA-seq. Some advantages of this technique are high reproducibility, the large dynamic range, requirement of less sample RNA, and the ability to detect novel transcripts, alternative splicing, even in the absence of a sequenced genome. However, this RNA-Seq technique will not likely replace current RT-PCR methods, but will be complementary depending on the needs and the resources of the clinic and the laboratory as the results of the RNA-Seq will identify those genes that need to then be examined using RT-PCR methods. The application of the two complementary technologies in the routine analysis of cancer laboratories would be useful in characterizing patients and would assist oncologists in making clinical decisions, as it allows us to identify all molecular characteristics of the tumor.

ALK and ROS1 as a joint target for the treatment of lung cancer: a review.

Rearrangements of the anaplastic lymphoma kinase (ALK) have been described in multiple malignancies, including non-small cell lung cancer (NSCLC). ALK fusions have gain of function properties while activating mutations in wild-type ALK can also occur within the tyrosine kinase domain. ALK rearrangements define a new molecular subtype of NSCLC that is exquisitely sensitive to ALK inhibition. Crizotinib, an orally available small molecule ATP-mimetic compound which was originally designed as a MET inhibitor, was recognized to have "off-target" anti-ALK activity and has been approved in the USA for the treatment of patients with ALK-positive NSCLC. Chromosomal rearrangements involving the ROS1 receptor tyrosine kinase have also been recently described in NSCLC, while crizotinib is currently under clinical trial in this molecular subset of NSCLC patients. The basic approaches of any computer aided drug design work in terms of structure and ligand based drug design. Details of each of these approaches should be covered with an emphasis on utilizing both in order to develop multi-targeted small-molecule kinase inhibitors. Such multi-targeted tyrosine kinase inhibitors can have antiproliferative activity against both ROS1and ALK rearranged NSCLC. Herein, we highlight the importance of targeting these proteins and the advances in optimizing more potent and selective ALK and ROS1 kinase inhibitors.

Adaptive resistance to targeted therapies in cancer.

It is widely acknowledged that there is a need for molecular profiling in non-small-cell lung cancer. For example, treatment based on EGFR mutation status has attained successful results. However, in spite of excellent initial response to oral EGFR tyrosine kinase inhibitors (TKIs), progression-free survival is still limited. Current research has focused mostly on acquired resistance mechanisms, such as overexpression of AXL and loss of the Mediator MED12. In this review, in contrast, we discuss adaptive, rather than acquired, resistance. Adaptive resistance can occur almost immediately after starting targeted therapy through a rapid rewiring of cancer cell signaling. By losing ERK negative feedback on receptor tyrosine kinase (RTK) expression, cancer cells are exposed to the stimuli of several ligands, and the ensuing activation of several RTKs reprograms all the canonical signaling pathways. The overexpression of several RTKs was observed in breast cancer cell lines treated with a MEK inhibitor and in BRAF(V600E) melanoma cell lines treated with BRAF inhibitors. This rebound effect of overexpression of several RTKs, including ERBB3, also occurs in lung cancers driven by Kras or EGFR mutations when treated with MEK, PI3K or dual PI3K/mTOR inhibitors. Synthetic lethality can be effectively induced by co-targeting these overexpressed RTKs. We speculate that in patients with EGFR mutations, adaptive resistance occurs in a significant proportion of patients. Rebiopsies performed hours after starting treatment with EGFR TKIs can identify which RTKs are overexpressed after treatment. Efficient co-targeting of these RTKs can induce synthetic lethality and help overcome the limited effect of EGFR TKI monotherapy.

Activation of the AXL kinase causes resistance to EGFR-targeted therapy in lung cancer.

Human non-small cell lung cancers (NSCLCs) with activating mutations in EGFR frequently respond to treatment with EGFR-targeted tyrosine kinase inhibitors (TKIs), such as erlotinib, but responses are not durable, as tumors acquire resistance. Secondary mutations in EGFR (such as T790M) or upregulation of the MET kinase are found in over 50% of resistant tumors. Here, we report increased activation of AXL and evidence for epithelial-to-mesenchymal transition (EMT) in multiple in vitro and in vivo EGFR-mutant lung cancer models with acquired resistance to erlotinib in the absence of the EGFR p.Thr790Met alteration or MET activation. Genetic or pharmacological inhibition of AXL restored sensitivity to erlotinib in these tumor models. Increased expression of AXL and, in some cases, of its ligand GAS6 was found in EGFR-mutant lung cancers obtained from individuals with acquired resistance to TKIs. These data identify AXL as a promising therapeutic target whose inhibition could prevent or overcome acquired resistance to EGFR TKIs in individuals with EGFR-mutant lung cancer.

Pharmacogenetics of EGFR in lung cancer: perspectives and clinical applications.

Lung cancer is a lethal disease, and most cases have already disseminated at the time of diagnosis. Driver mutations in the EGFR tyrosine kinase domain (mainly deletions in exon 19 and L858R mutation in exon 21) have been identified in lung adenocarcinomas, mostly in never smokers, at frequencies of 20-60%. The EGFR tyrosine kinase inhibitors (TKIs) gefitinib or erlotinib attain a response rate of 70% and progression-free survival of 9-13 months, although there are subgroups of patients with long-lasting remissions. No significant correlation between EGFR overexpression and response to treatment has been found, while controversial results have been reported regarding EGFR gene amplification. The pretreatment presence of the T790M mutation, initially identified as an acquired resistance mutation to treatment with EGFR TKIs, has also been reported and may indicate a genetically distinct disease. Finally, other genetic factors, such as mRNA expression of BRCA1 and components of the NF-κB pathway, can modulate response to EGFR TKIs in EGFR-mutated patients.

mRNA expression levels and genetic status of genes involved in the EGFR and NF-κB pathways in metastatic non-small-cell lung cancer patients.

BACKGROUND: Metastatic non-small-cell lung cancer (NSCLC) has a dismal prognosis. EGFR is overexpressed or mutated in a large proportion of cases. Downstream components of the EGFR pathway and crosstalk with the NF-κB pathway have not been examined at the clinical level. We explored the prognostic significance of the mRNA expression of nine genes in the EGFR and NF-κB pathways and of BRCA1 and RAP80 in patients in whom EGFR and K-ras gene status had previously been determined. In addition, NFKBIA and DUSP22 gene status was also determined. METHODS: mRNA expression of the eleven genes was determined by QPCR in 60 metastatic NSCLC patients and in nine lung cancer cell lines. Exon 3 of NFKBIA and exon 6 of DUSP22 were analyzed by direct sequencing. Results were correlated with outcome to platinum-based chemotherapy in patients with wild-type EGFR and to erlotinib in those with EGFR mutations. RESULTS: BRCA1 mRNA expression was correlated with EZH2, AEG-1, Musashi-2, CYLD and TRAF6 expression. In patients with low levels of both BRCA1 and AEG-1, PFS was 13.02 months, compared to 5.4 months in those with high levels of both genes and 7.7 months for those with other combinations (P=0.025). The multivariate analysis for PFS confirmed the prognostic role of high BRCA1/AEG-1 expression (HR, 3.1; P=0.01). Neither NFKBIA nor DUSP22 mutations were found in any of the tumour samples or cell lines. CONCLUSIONS: The present study provides a better understanding of the behaviour of metastatic NSCLC and identifies the combination of BRCA1 and AEG-1 expression as a potential prognostic model.

mRNA expression of BRCA1, PIAS1, and PIAS4 and survival after second-line docetaxel in advanced gastric cancer.

Breast cancer susceptibility gene 1 (BRCA1) has a central role in chemotherapy-induced DNA damage response. The protein inhibitor of activated STAT (PIAS) family of proteins, PIAS1 and PIAS4, are also necessary for adequate DNA damage repair. To further understand the role of BRCA1 in DNA repair, we examined the mRNA expression of these genes in 133 advanced (stage III-IV) gastric cancer patients using quantitative reverse transcription polymerase chain reaction. All P values were two-sided. The median overall survival was 12.5 months (95% confidence interval [CI] = 9.8 to 13.4 months). Among 59 patients receiving second-line docetaxel, the median overall survival was 25.8 months (95% CI = 9.2 to 42.4 months) for patients with high BRCA1 expression, 19.1 months (95% CI = 3.4 to 34.8 months) for those with intermediate expression, and 9.5 months (95% CI = 8.7 to 10.2 months) for those with low expression (P = .0062). The risk of mortality was higher in patients with low BRCA1 levels compared with high BRCA1 levels (hazard ratio of death = 2.49, 95% CI = 1.03 to 5.97, P = .037). Survival in patients receiving second-line docetaxel-based chemotherapy showed a similar trend with PIAS1 and PIAS4 mRNA expression levels, although the associations for PIAS4 were not statistically significant.

Fifth Educational Symposium of the Spanish Lung Cancer Group: report on the Molecular Biology Workshop.

The majority of non-small-cell lung cancer (NSCLC) patients present with locally advanced (35%) or metastatic disease (40%); in this setting, it is of the utmost importance to balance efficacy with toxicity. However, with platinum combinations, survival has reached a "plateau", with median overall survival times of a mere 10-12 months, making it mandatory to search for new strategies and to identify more effective treatment. Molecular characteristics can be more informative than clinical features in predicting clinical benefit, and the identification of molecular markers can help define subgroups of patients who are likely to respond to different treatments, thus avoiding unnecessary toxicities and costs and providing the maximum benefit to each patient. Here we review research on biomarker assessment that was presented during the Molecular Biology Workshop held in Palma de Mallorca on 25 November 2010, during the Fifth Educational Symposium of the Spanish Lung Cancer Group.

FAS and NF-κB signalling modulate dependence of lung cancers on mutant EGFR.

Human lung adenocarcinomas with activating mutations in EGFR (epidermal growth factor receptor) often respond to treatment with EGFR tyrosine kinase inhibitors (TKIs), but the magnitude of tumour regression is variable and transient. This heterogeneity in treatment response could result from genetic modifiers that regulate the degree to which tumour cells are dependent on mutant EGFR. Through a pooled RNA interference screen, we show that knockdown of FAS and several components of the NF-κB pathway specifically enhanced cell death induced by the EGFR TKI erlotinib in EGFR-mutant lung cancer cells. Activation of NF-κB through overexpression of c-FLIP or IKK (also known as CFLAR and IKBKB, respectively), or silencing of IκB (also known as NFKBIA), rescued EGFR-mutant lung cancer cells from EGFR TKI treatment. Genetic or pharmacologic inhibition of NF-κB enhanced erlotinib-induced apoptosis in erlotinib-sensitive and erlotinib-resistant EGFR-mutant lung cancer models. Increased expression of the NF-κB inhibitor IκB predicted for improved response and survival in EGFR-mutant lung cancer patients treated with EGFR TKI. These data identify NF-κB as a potential companion drug target, together with EGFR, in EGFR-mutant lung cancers and provide insight into the mechanisms by which tumour cells escape from oncogene dependence.

Pretreatment EGFR T790M mutation and BRCA1 mRNA expression in erlotinib-treated advanced non-small-cell lung cancer patients with EGFR mutations.

PURPOSE: Advanced non-small-cell lung cancer (NSCLC) patients harboring epidermal growth factor receptor (EGFR) mutations (deletion in exon 19 or L858R) show an impressive progression-free survival of 14 months when treated with erlotinib. However, the presence of EGFR mutations can only imperfectly predict outcome. We hypothesized that progression-free survival could be influenced both by the pretreatment EGFR T790M mutation and by components of DNA repair pathways. EXPERIMENTAL DESIGN: We assessed the T790M mutation in pretreatment diagnostic specimens from 129 erlotinib-treated advanced NSCLC patients with EGFR mutations. The expression of eight genes and two proteins involved in DNA repair and four receptor tyrosine kinases was also examined. RESULTS: The EGFR T790M mutation was observed in 45 of 129 patients (35%). Progression-free survival was 12 months in patients with and 18 months in patients without the T790M mutation (P = 0.05). Progression-free survival was 27 months in patients with low BRCA1 mRNA levels, 18 months in those with intermediate levels, and 10 months in those with high levels (P = 0.02). In the multivariate analysis, the presence of the T790M mutation (HR, 4.35; P = 0.001), intermediate BRCA1 levels (HR, 8.19; P < 0.0001), and high BRCA1 levels (HR, 8.46; P < 0.0001) emerged as markers of shorter progression-free survival. CONCLUSIONS: Low BRCA1 levels neutralized the negative effect of the T790M mutation and were associated with longer progression-free survival to erlotinib. We advocate baseline assessment of the T790M mutation and BRCA1 expression to predict outcome and provide alternative individualized treatment to patients based on T790M mutations and BRCA1 expression.