The role of RAS oncogene in survival of patients with lung cancer: a systematic review of the literature with meta-analysis

Impact of KRAS and EGFR gene mutations on recurrence and survival in patients with surgically resected lung adenocarcinomas

BACKGROUND

Oncogenic gene mutations observed in lung adenocarcinomas, such as epidermal growth factor receptor (EGFR) and KRAS, have some predictive value for chemotherapeutic drugs or EGFR-tyrosine kinase inhibitors. However, the influence of these gene alterations on patients' prognosis remains controversial.

METHODS

We retrospectively analyzed the tumors of 180 patients with completely resected pathological stage I-III lung adenocarcinoma which harbored either KRAS codon 12 mutation or EGFR gene mutations within exons 18-21 to investigate the impact of these gene mutations on the patients' survival. Gene mutations were detected by established methods.

RESULTS

Of 180 patients, 32 had KRAS codon 12 mutations (KRAS group), 148 had EGFR mutations within exon 18-21 (EGFR group). Pathological stage and operation mode were independent factors for disease-free survival. However, the EGFR group had better overall survival than the KRAS group (P = 0.0271). Cox proportional hazard model revealed pathological stage (P = 0.0001) and presence of EGFR gene mutations (P = 0.0408) were independent factors for overall survival. In survival after tumor recurrence, the EGFR group had a better median survival time (46.7 months) after recurrence than the KRAS group (26.0 months).

CONCLUSIONS

In patients with completely resected lung adenocarcinomas, KRAS and EGFR gene mutation status of tumors was not associated with disease-free survival. However, the presence of an EGFR gene mutation boded well for the patient's overall survival, and thus patients with EGFR mutations have a better prognosis than those with KRAS mutations.

Selective killing of K-ras mutant cancer cells by small molecule inducers of oxidative stress

Activating K-RAS mutations are the most frequent oncogenic mutations in human cancer. Numerous downstream signaling pathways have been shown to be deregulated by oncogenic K-ras. However, to date there are still no effective targeted therapies for this genetically defined subset of patients. Here we report the results of a small molecule, synthetic lethal screen using mouse embryonic fibroblasts derived from a mouse model harboring a conditional oncogenic K-ras(G12D) allele. Among the >50,000 compounds screened, we identified a class of drugs with selective activity against oncogenic K-ras-expressing cells. The most potent member of this class, lanperisone, acts by inducing nonapoptotic cell death in a cell cycle- and translation-independent manner. The mechanism of cell killing involves the induction of reactive oxygen species that are inefficiently scavenged in K-ras mutant cells, leading to oxidative stress and cell death. In mice, treatment with lanperisone suppresses the growth of K-ras-driven tumors without overt toxicity. Our findings establish the specific antitumor activity of lanperisone and reveal oxidative stress pathways as potential targets in Ras-mediated malignancies.

Clinicopathological features of lung adenocarcinoma with KRAS mutations

BACKGROUND

KRAS and epidermal growth factor receptor (EGFR) mutations are thought to play an important role in the carcinogenesis of lung adenocarcinoma. However, clinicopathological findings of KRAS mutated adenocarcinoma cases have not yet been fully clarified. The authors analyzed the relationship between the KRAS mutation and corresponding clinicopathological findings, focusing on nonmucinous and mucinous bronchioloalveolar elements.

METHODS

EGFR and KRAS mutations were detected in DNA samples extracted from 182 surgically resected tissues of lung adenocarcinomas by the Smart Amplification Process. The relations between gene mutation status and clinicopathological features were analyzed. All adenocarcinoma cases were divided into bronchioloalveolar carcinoma (BAC), adenocarcinoma with bronchioloalveolar features, and adenocarcinoma without BAC components (non-BAC). BAC/adenocarcinoma with bronchioloalveolar features tumors were further assessed for the presence of mucinous features.

RESULTS

EGFR and KRAS mutations were found in 76 and 30 cases, respectively. In the KRAS mutant group, BAC/adenocarcinoma with bronchioloalveolar features was found in 22 cases, which included 10 nonmucinous and 12 mucinous tumors. Of 19 cases with mucinous BAC/adenocarcinoma with bronchioloalveolar features, KRAS mutations were detected in 12, but no EGFR mutation was detected. In the KRAS mutant group, BAC/adenocarcinoma with bronchioloalveolar features had significantly earlier pathological stages and more favorable prognoses than did non-BAC. Mucinous BAC/adenocarcinoma with bronchioloalveolar features showed less smoking history than did nonmucinous BAC/adenocarcinoma with bronchioloalveolar features and non-BAC. Furthermore, transversion type KRAS mutations were more common in non-BAC.

CONCLUSIONS

KRAS mutated adenocarcinomas can be divided into BAC/adenocarcinoma with bronchioloalveolar features and non-BAC types. Non-BAC adenocarcinoma is related to smoking history and has a poor prognosis. BAC/adenocarcinoma with bronchioloalveolar features adenocarcinoma, however, has a more favorable prognosis, and mucinous BAC/adenocarcinoma with bronchioloalveolar features has little relationship to smoking history.

Mind-mapping for lung cancer: towards a personalized therapeutics approach

There were over 220,000 people diagnosed with lung cancer and over 160,000 people dying of lung cancer during 2010 alone in the United States. In order to arrive at better control, prevention, diagnosis, and therapeutics for lung cancer, we must be able to personalize the approach towards the disease. Mind-mapping has existed for centuries for physicians to properly think about various "flows" of personalized medicine. We include here the epidemiology, diagnosis, histology, and treatment of lung cancer-in particular, non-small cell lung cancer. As we have new molecular signatures for lung cancer, this is further detailed. This review is not meant to be a comprehensive review, but rather its purpose is to highlight important aspects of lung cancer diagnosis, management, and personalized treatment options.

Analysis of Somatic Mutations in Cancer: Molecular Mechanisms of Activation in the ErbB Family of Receptor Tyrosine Kinases

The ErbB/EGFR/HER family of kinases consists of four homologous receptor tyrosine kinases which are important regulatory elements in many cellular processes, including cell proliferation, differentiation, and migration. Somatic mutations in, or over-expression of, the ErbB family is found in many cancers and is correlated with a poor prognosis; particularly, clinically identified mutations found in non-small-cell lung cancer (NSCLC) of ErbB1 have been shown to increase its basal kinase activity and patients carrying these mutations respond remarkably to the small tyrosine kinase inhibitor gefitinib. Here, we analyze the potential effects of the currently catalogued clinically identified mutations in the ErbB family kinase domains on the molecular mechanisms of kinase activation. Recently, we identified conserved networks of hydrophilic and hydrophobic interactions characteristic to the active and inactive conformation, respectively. Here, we show that the clinically identified mutants influence the kinase activity in distinctive fashion by affecting the characteristic interaction networks.

International association for the study of lung cancer/american thoracic society/european respiratory society international multidisciplinary classification of lung adenocarcinoma

INTRODUCTION

Adenocarcinoma is the most common histologic type of lung cancer. To address advances in oncology, molecular biology, pathology, radiology, and surgery of lung adenocarcinoma, an international multidisciplinary classification was sponsored by the International Association for the Study of Lung Cancer, American Thoracic Society, and European Respiratory Society. This new adenocarcinoma classification is needed to provide uniform terminology and diagnostic criteria, especially for bronchioloalveolar carcinoma (BAC), the overall approach to small nonresection cancer specimens, and for multidisciplinary strategic management of tissue for molecular and immunohistochemical studies.

METHODS

An international core panel of experts representing all three societies was formed with oncologists/pulmonologists, pathologists, radiologists, molecular biologists, and thoracic surgeons. A systematic review was performed under the guidance of the American Thoracic Society Documents Development and Implementation Committee. The search strategy identified 11,368 citations of which 312 articles met specified eligibility criteria and were retrieved for full text review. A series of meetings were held to discuss the development of the new classification, to develop the recommendations, and to write the current document. Recommendations for key questions were graded by strength and quality of the evidence according to the Grades of Recommendation, Assessment, Development, and Evaluation approach.

RESULTS

The classification addresses both resection specimens, and small biopsies and cytology. The terms BAC and mixed subtype adenocarcinoma are no longer used. For resection specimens, new concepts are introduced such as adenocarcinoma in situ (AIS) and minimally invasive adenocarcinoma (MIA) for small solitary adenocarcinomas with either pure lepidic growth (AIS) or predominant lepidic growth with ≤ 5 mm invasion (MIA) to define patients who, if they undergo complete resection, will have 100% or near 100% disease-specific survival, respectively. AIS and MIA are usually nonmucinous but rarely may be mucinous. Invasive adenocarcinomas are classified by predominant pattern after using comprehensive histologic subtyping with lepidic (formerly most mixed subtype tumors with nonmucinous BAC), acinar, papillary, and solid patterns; micropapillary is added as a new histologic subtype. Variants include invasive mucinous adenocarcinoma (formerly mucinous BAC), colloid, fetal, and enteric adenocarcinoma. This classification provides guidance for small biopsies and cytology specimens, as approximately 70% of lung cancers are diagnosed in such samples. Non-small cell lung carcinomas (NSCLCs), in patients with advanced-stage disease, are to be classified into more specific types such as adenocarcinoma or squamous cell carcinoma, whenever possible for several reasons: (1) adenocarcinoma or NSCLC not otherwise specified should be tested for epidermal growth factor receptor (EGFR) mutations as the presence of these mutations is predictive of responsiveness to EGFR tyrosine kinase inhibitors, (2) adenocarcinoma histology is a strong predictor for improved outcome with pemetrexed therapy compared with squamous cell carcinoma, and (3) potential life-threatening hemorrhage may occur in patients with squamous cell carcinoma who receive bevacizumab. If the tumor cannot be classified based on light microscopy alone, special studies such as immunohistochemistry and/or mucin stains should be applied to classify the tumor further. Use of the term NSCLC not otherwise specified should be minimized.

CONCLUSIONS

This new classification strategy is based on a multidisciplinary approach to diagnosis of lung adenocarcinoma that incorporates clinical, molecular, radiologic, and surgical issues, but it is primarily based on histology. This classification is intended to support clinical practice, and research investigation and clinical trials. As EGFR mutation is a validated predictive marker for response and progression-free survival with EGFR tyrosine kinase inhibitors in advanced lung adenocarcinoma, we recommend that patients with advanced adenocarcinomas be tested for EGFR mutation. This has implications for strategic management of tissue, particularly for small biopsies and cytology samples, to maximize high-quality tissue available for molecular studies. Potential impact for tumor, node, and metastasis staging include adjustment of the size T factor according to only the invasive component (1) pathologically in invasive tumors with lepidic areas or (2) radiologically by measuring the solid component of part-solid nodules.

KRAS gene mutations in lung cancer: particulars established and issues unresolved

Lung cancer, like other cancers, is considered to develop through the accumulation of genetic alterations. Mutation of the KRAS gene is one of the most important events in carcinogenesis of the lung. The KRAS gene, belonging to the RAS gene family, encodes a membrane-bound 21-kd guanosine triphosphate (GTP)-binding protein. Single point mutations in this protein result in continuous activation to transmit excessive signals, promoting a variety of biological events. In lung cancers, the mutations concentrate at codon 12 and mostly affect adenocarcinomas (ADCs). They also affect atypical adenomatous hyperplasia, the precursor of ADCs. Therefore, mutation of the KRAS gene is suggested to confer a growth advantage to airway epithelial cells enabling them to expand clonally early in the development of ADCs. The mutation is also a reliable marker of an unfavorable response to certain molecular-targeting therapies. Furthermore, patients with ADCs affected by mutations have been reported to exhibit a significantly higher risk of postoperative disease recurrence. Thus, the significance of KRAS gene mutations has been investigated extensively. However, not all the details emerged. In this review, particulars that have been established are introduced, and important issues remaining to be resolved are discussed, with special reference to carcinogenesis of the lung.

[Molecular characteristics of lung cancer]

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

Molecular testing in lung cancer: the time is now

In the past few years, we have witnessed a revolution in the molecular understanding of non-small cell lung cancer. Major progress has also been made in the clinic, with the introduction of EGFR-targeted and anti-angiogenic therapies. These advances have led to the development of a multitude of commercially available prognostic and predictive biomarkers. In particular, EGFR mutation and EML4/ALK testing have reached clinical validation and are incorporated into current treatment paradigms. This overview will present the scientific background of the biology of the relevant biomarkers and the studies conducted for their clinical validation. The technical challenges and shortcomings of these assays are also discussed. Furthermore, ongoing biomarker-driven clinical studies and the appropriate clinical use of available tests will be reviewed to assist the clinician with the proper incorporation of molecular testing into the routine care of patients with non-small cell lung cancer.

Personalized Medicine in Non–Small-Cell Lung Cancer: Is KRAS a Useful Marker in Selecting Patients for Epidermal Growth Factor Receptor–Targeted Therapy?

In patients with metastatic colorectal cancer, the predictive value of KRAS mutational status in the selection of patients for treatment with anti–epidermal growth factor (EGFR) monoclonal antibodies is established. In patients with non–small-cell lung cancer (NSCLC), the utility of determining KRAS mutational status to predict clinical benefit to anti-EGFR therapies remains unclear. This review will provide a brief description of Ras biology, provide an overview of aberrant Ras signaling in NSCLC, and summarize the clinical data for using KRAS mutational status as a negative predictive biomarker to anti-EGFR therapies. Retrospective investigations of KRAS mutational status as a negative predictor of clinical benefit from anti-EGFR therapies in NSCLC have been performed; however, small samples sizes as a result of low prevalence of KRAS mutations and the low rate of tumor sample collection have limited the strength of these analyses. Although an association between the presence of KRAS mutation and lack of response to EGFR tyrosine kinase inhibitors (TKIs) has been observed, it remains unclear whether there is an association between KRAS mutation and EGFR TKI progression-free and overall survival. Unlike colorectal cancer, KRAS mutations do not seem to identify patients who do not benefit from anti-EGFR monoclonal antibodies in NSCLC. The future value of testing for KRAS mutational status may be to exclude the possibility of an EGFR mutation or anaplastic lymphoma kinase translocation or to identify a molecular subset of patients with NSCLC in whom to pursue a drug development strategy that targets the KRAS pathway.

Reflex testing of resected stage I through III lung adenocarcinomas for EGFR and KRAS mutation: report on initial experience and clinical utility at a single center

OBJECTIVE

The genes KRAS and EGFR have emerged as potential targets for therapy in lung adenocarcinoma; mutations in these genes can be found in almost half of patients. In anticipation of the clinical importance of molecularly defined adenocarcinoma subgroups for the treatment of patients with resected stages I through III lung adenocarcinoma, the Memorial Sloan-Kettering Cancer Center (MSKCC) Departments of Surgery and Pathology have collaborated since 2006 to conduct reflex testing of tumor specimens for EGFR and KRAS mutations.

METHODS

Using established methods, the identification of EGFR exon 19 deletions and exon 21 L858R mutations was performed. In samples lacking these 2 sensitizing EGFR mutations, KRAS analysis was done.

RESULTS

We studied a total of 1831 patients who had stage I through IV lung adenocarcinomas and detected 448 KRAS and 364 EGFR mutations. Of these patients, a subset of 855 (78%) patients with stages I through III adenocarcinoma of the lung who underwent curative surgical resection at MSKCC were tested. In patients with early stage disease, 158 EGFR mutations and 207 KRAS mutations were detected.

CONCLUSIONS

The results of the first 3 years of reflex testing at MSKCC reported here demonstrate the feasibility, clinical utility, and potential of this approach. This information allowed for enrollment of patients into clinical trials to explore mutation-specific, directed therapy and led to retrospective studies related to patient outcome. In addition, it may inform selection of chemotherapy for recurrent disease and may help to distinguish multiple primary tumors from metastatic disease.

Tumor and host factors that may limit efficacy of chemotherapy in non-small cell and small cell lung cancer

While chemotherapy provides useful palliation, advanced lung cancer remains incurable since those tumors that are initially sensitive to therapy rapidly develop acquired resistance. Resistance may arise from impaired drug delivery, extracellular factors, decreased drug uptake into tumor cells, increased drug efflux, drug inactivation by detoxifying factors, decreased drug activation or binding to target, altered target, increased damage repair, tolerance of damage, decreased proapoptotic factors, increased antiapoptotic factors, or altered cell cycling or transcription factors. Factors for which there is now substantial clinical evidence of a link to small cell lung cancer (SCLC) resistance to chemotherapy include MRP (for platinum-based combination chemotherapy) and MDR1/P-gp (for non-platinum agents). SPECT MIBI and Tc-TF scanning appears to predict chemotherapy benefit in SCLC. In non-small cell lung cancer (NSCLC), the strongest clinical evidence is for taxane resistance with elevated expression or mutation of class III beta-tubulin (and possibly alpha tubulin), platinum resistance and expression of ERCC1 or BCRP, gemcitabine resistance and RRM1 expression, and resistance to several agents and COX-2 expression (although COX-2 inhibitors have had minimal impact on drug efficacy clinically). Tumors expressing high BRCA1 may have increased resistance to platinums but increased sensitivity to taxanes. Limited early clinical data suggest that chemotherapy resistance in NSCLC may also be increased with decreased expression of cyclin B1 or of Eg5, or with increased expression of ICAM, matrilysin, osteopontin, DDH, survivin, PCDGF, caveolin-1, p21WAF1/CIP1, or 14-3-3sigma, and that IGF-1R inhibitors may increase efficacy of chemotherapy, particularly in squamous cell carcinomas. Equivocal data (with some positive studies but other negative studies) suggest that NSCLC tumors with some EGFR mutations may have increased sensitivity to chemotherapy, while K-ras mutations and expression of GST-pi, RB or p27kip1 may possibly confer resistance. While limited clinical data suggest that p53 mutations are associated with resistance to platinum-based therapies in NSCLC, data on p53 IHC positivity are equivocal. To date, resistance-modulating strategies have generally not proven clinically useful in lung cancer, although small randomized trials suggest a modest benefit of verapamil and related agents in NSCLC.

[K-RAS gene mutations in patients with non-small cell lung cancer]

BACKGROUND AND OBJECTIVE

Recent studies indicated that Non-small cell lung cancer (NSCLC) patients with mutant K-RAS failed to benefit from adjuvant chemotherapy, and the cancer did not respond to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs). These findings indicated that K-RAS gene status can be a biomarker to predict the sensitivity of EGFR TKIs. The aim of this study is to analyze K-RAS gene mutations with NSCLC patients in Cancer Center of Sun Yet-sen University.

METHODS

52 fresh frozen tumor tissues were collected and K-RAS genes were amplified by PCR. Then PCR amplification fragments were sequenced and analyzed.

RESULTS

Somatic mutations in the codon 12 of K-RAS gene in tumors were identified from 2 of 52 (3.8%) patients. There were no relationships among K-RAS gene mutations and gender, pathology, smoking, differentiation and stage.

CONCLUSION

The frequency of K-RAS gene mutations with NSCLC in our center is very low and is similar to that in Asia patients, and is lower than that in Caucasian population.

[The predictive value of EGFR status in non-small cell lung cancer patients treated with EGFR-TKIs]

Epidermal growth factor receptor (EGFR) is a major molecular for target therapy. The epidermal growth factor receptor tyrosine kinase inhibitors (TKIs), gefitinib (Iressa) and erlotinib (Tarceva), are two prospective agents towards non-small cell lung cancer (NSCLC). Multi-center clinical studies showed that there were obvious differences between individuals by the treatment of EGFR-TKIs. EGFR status is the major factor that influences the outcome for the treatment by TKI. Exon mutations and amplification of EGFR molecule are the critical factors that predict good response to TKIs. On the other hand, KRAS mutations indicate the resistant to the TKIs.

[A simple look at the molecular biology of lung cancer: K-Ras]

Ras genes encode a family of membrane proteins involved in the regulation of cell growth. Mutations of Ras stimulate cell growth and thus can play a role in carcinogenesis. The search for mutations of Ras is possible by PCR on bronchial biopsies or surgical specimens. They are found in 15 to 20% of non-small cell lung cancers. In the disease's early stage, the presence of a Ras mutation can be a negative predictor of the effectiveness of adjuvant chemotherapy. In the advanced stage of the disease, it is a factor predicting a poor prognosis. Although prospective studies have found no statistically significant negative influence of the presence of a mutation of Ras on the effectiveness of tyrosine kinase inhibitors of EGFR, it is likely that these treatments will be of limited value in this population given the lack of response observed when Ras is mutated. Prospective and functional studies are needed to determine the value of the different mutations observed.

A gene expression signature of RAS pathway dependence predicts response to PI3K and RAS pathway inhibitors and expands the population of RAS pathway activated tumors

Background

Hyperactivation of the Ras signaling pathway is a driver of many cancers, and RAS pathway activation can predict response to targeted therapies. Therefore, optimal methods for measuring Ras pathway activation are critical. The main focus of our work was to develop a gene expression signature that is predictive of RAS pathway dependence.

Methods

We used the coherent expression of RAS pathway-related genes across multiple datasets to derive a RAS pathway gene expression signature and generate RAS pathway activation scores in pre-clinical cancer models and human tumors. We then related this signature to KRAS mutation status and drug response data in pre-clinical and clinical datasets.

Results

The RAS signature score is predictive of KRAS mutation status in lung tumors and cell lines with high (> 90%) sensitivity but relatively low (50%) specificity due to samples that have apparent RAS pathway activation in the absence of a KRAS mutation. In lung and breast cancer cell line panels, the RAS pathway signature score correlates with pMEK and pERK expression, and predicts resistance to AKT inhibition and sensitivity to MEK inhibition within both KRAS mutant and KRAS wild-type groups. The RAS pathway signature is upregulated in breast cancer cell lines that have acquired resistance to AKT inhibition, and is downregulated by inhibition of MEK. In lung cancer cell lines knockdown of KRAS using siRNA demonstrates that the RAS pathway signature is a better measure of dependence on RAS compared to KRAS mutation status. In human tumors, the RAS pathway signature is elevated in ER negative breast tumors and lung adenocarcinomas, and predicts resistance to cetuximab in metastatic colorectal cancer.

Conclusions

These data demonstrate that the RAS pathway signature is superior to KRAS mutation status for the prediction of dependence on RAS signaling, can predict response to PI3K and RAS pathway inhibitors, and is likely to have the most clinical utility in lung and breast tumors.

EP4 upregulation of Ras signaling and feedback regulation of Ras in human colon tissues and cancer cells

Previous studies indicate that COX-2 and prostaglandin E(2) (PGE(2)) receptor subtypes are involved in intestinal carcinogenesis and activation of downstream pathways. In this report, we try to understand the association of PGE(2) receptor and K-ras cellular mechanism during the development of colorectal cancer. We collected 21 colorectal cancer patients and compared the protein expression of tumor tissues and normal mucosa tissues by using immunoblot. Furthermore, we transferred empty vector and pcDNA-K-ras into Ras-HT29 colon cancer cells. Result showed that phosphorylation of Akt and EP(1)/EP(4) were over-expressed in the colorectal tumor tissue. K-ras induces HT29 cells proliferation through the expressions of COX-2, EP1/EP4, pAkt, GSK3beta and increases Tcf transcriptional factor activation. Additionally, Ras protein was suppressed when treated with EP(4) inhibitor in Ras-HT29 cell. In cell cycle assay, K-ras mutation causing cell cycle S phase was prolonged with an increase in the G2/M phase ratio. In conclusion, we suggested that Ras overexpression leads to cell proliferation through activating Ras/PI3K/GSK3beta/EP(4) PGE(2) receptor signals and caused a feedback regulation of Ras by EP4 in colorectal tumor progression.

K-RAS mutation in the screening, prognosis and treatment of cancer

The potential use of K-RAS mutation as a cancer screening biomarker has been investigated for many years. Numerous associations between K-RAS mutation and various cancers have been established, but these associations have not been translated into effective, cost-efficient cancer screening strategies. This lack of progress may be due to the existence of K-RAS mutation in nontumor tissues and/or using detection, rather than quantitation, of K-RAS mutation as the endpoint for cancer risk categorization. K-RAS mutation appears to be a useful prognostic biomarker for colon cancer. Recent progress toward sensitive and quantitative mutation characterization and the successful use of K-RAS mutation in a personalized medicine approach to targeted biological therapy selection are likely to re-direct and expand the use of K-RAS mutation as a cancer biomarker in the near future.

Biological and clinical significance of KRAS mutations in lung cancer: an oncogenic driver that contrasts with EGFR mutation

KRAS and epidermal growth factor receptor (EGFR) are the two most frequently mutated proto-oncogenes in adenocarcinoma of the lung. The occurrence of these two oncogenic mutations is mutually exclusive, and they exhibit many contrasting characteristics such as clinical background, pathological features of patients harboring each mutation, and prognostic or predictive implications. Lung cancers harboring the EGFR mutations are remarkably sensitive to EGFR tyrosine kinase inhibitors such as gefitinib or erlotinib. This discovery has dramatically changed the clinical treatment of lung cancer in that it almost doubled the duration of survival for lung cancer patients with an EGFR mutation. In this review, we describe the features of KRAS mutations in lung cancer and contrast these with the features of EGFR mutations. Recent strategies to combat lung cancer harboring KRAS mutations are also reviewed.

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.

Mixed Adenocarcinomas of the Lung: Place in New Proposals in Classification, Mandatory for Target Therapy

Context.—Lung cancer is one of the most frequent and lethal malignant neoplasms, but knowledge regarding the molecular basis of its pathogenesis is far from complete due to the striking diversity of different forms. The current lung cancer classification (World Health Organization 2004) can efficiently distinguish clinically relevant major subtypes (small cell and non–small cell carcinomas), but its results are partly inadequate when facing prognostic and therapeutic decisions for non–small cell carcinomas, especially for the group of tumors classified as adenocarcinoma. Lung adenocarcinoma comprises a heterogeneous group of tumors characterized by diverse morphologic features and molecular pathogenesis. The category of mixed adenocarcinomas includes most adenocarcinomas (approximately 80%) and, according to World Health Organization criteria, is defined by the occurrence of a mixed array of different patterns (acinar, papillary, bronchioloalveolar, solid with mucin). The histologic recognition of mixed adenocarcinoma is subjective and cannot consistently discriminate between responders and nonresponders to new targeted therapies (eg, tyrosine kinase inhibitors). Diagnostic problems are mainly related to the poor reproducibility of histologic criteria, especially when applied in small biopsies and cytology, and to the difficulty in assigning each form to a precisely defined entity, as needed by updated therapeutic approaches. In this evolving scenario, pathologists face new challenging diagnostic roles that include not only the precise morphologic definition of carcinoma subtypes but also their molecular characterization.

Objective.—To use a comprehensive critical analysis reconciling the overwhelming variety of biologic, morphologic, molecular, and clinical data to define new classification schemes for lung adenocarcinoma.

Data Sources.—Scientific literature and personal data were used.

Conclusions.—A new classification approach should redefine lung adenocarcinoma heterogeneity reconciling classic morphology, immunophenotypic and molecular features of neoplastic cells, and also relevant information provided by stem cell biology. This approach, which has been already successfully applied in World Health Organization classification of other tumors, could improve the recognition of new reproducible profiles for adenocarcinomas, more closely and reproducibly related to clinical features and response to specific therapies, limiting the use of “wastebasket” categories such as mixed adenocarcinoma.

Clinical outcome of patients with non-small cell lung cancer receiving front-line chemotherapy according to EGFR and K-RAS mutation status

BACKGROUND

Somatic mutations in EGFR and K-RAS may predict for sensitivity and resistance to EGFR tyrosine kinase inhibitors (TKIs). Whether EGFR and K-RAS mutations could also predict clinical outcome of non-small cell lung cancer (NSCLC) patients following front-line chemotherapy has not yet been established.

PATIENTS AND METHODS

One hundred and sixty-two chemotherapy-naïve patients with locally advanced/metastatic NSCLC who received front-line chemotherapy were included in this retrospective study and their clinical outcome data was analyzed according to EGFR and K-RAS mutation status of their tumors.

RESULTS

Classical activating EGFR and K-RAS mutations were found in 8.2 and 22.6% of patients respectively and were not associated with patients' clinicopathological characteristics. Patients with classical EGFR mutations had a higher probability of response to front-line chemotherapy as compared to those with wild type EGFR (p=0.023). Multivariate analysis showed that the presence of activating EGFR mutations was an independent factor associated with response to front-line chemotherapy (HR=4.85; 95% CI: 1.13-20.83, p=0.034). K-RAS mutation status was not associated with response to front-line chemotherapy. The presence of activating EGFR but not of K-RAS mutations was associated with a significantly higher overall survival compared to patients without mutations treated with platinum-based front-line chemotherapy (p=0.043).

CONCLUSIONS

The data indicate that EGFR mutation status could be predictive for response to cytotoxic front-line chemotherapy in patients with NSCLC. Additional prospective studies are needed in order to validate this observation and to define whether these patients should be preferentially treated with front-line TKIs or chemotherapy.

The mitogen-activated protein/extracellular signal-regulated kinase kinase 1/2 inhibitor AZD6244 (ARRY-142886) enhances the radiation responsiveness of lung and colorectal tumor xenografts

PURPOSE

Novel molecularly targeted agents, given in combination with radiotherapy, have the potential to increase tumor response rates and the survival of patients with lung cancer. AZD6244 is a potent and selective inhibitor of mitogen-activated protein kinase (MAPK) kinase 1/2 (MEK1/2), a critical enzyme within the MAPK/extracellular signal-regulated kinase (ERK) signaling pathway that regulates the proliferation and survival of tumor cells.

EXPERIMENTAL DESIGN

This study examined the potential benefit of combining AZD6244 with fractionated radiotherapy using human lung and colon carcinoma xenograft models.

RESULTS

AZD6244 reduced ERK phosphorylation in Calu-6 lung cancer cells in vitro. Administration of AZD6244 for 10 days (25 mg/kg twice daily p.o.) inhibited the tumor growth of Calu-6 xenografts, with regrowth occurring on cessation of drug treatment. When fractionated tumor-localized radiotherapy (5 x 2 Gy) was combined with AZD6244 treatment, the tumor growth delay was enhanced significantly when compared with either modality alone, and this effect was also seen in a colon tumor model. We examined the effect of inhibiting MEK1/2 on the molecular responses to hypoxia, a potential interaction that could contribute to radioresponsiveness. AZD6244 reduced hypoxia-inducible factor-specific transactivation in vivo, shown using Calu-6 dual clone cells that stably express a Firefly luciferase gene under the control of a hypoxia-driven promoter. Furthermore, hypoxia-inducible factor-1 alpha, GLUT-1, and vascular endothelial growth factor levels were reduced by AZD6244, and there was a significant decrease in vascular perfusion in the tumors given combination treatment when compared with the other treatment groups.

CONCLUSIONS

These data provide support for the clinical development of AZD6244 in combination with radiotherapy and indicate a potential role for AZD6244 in inhibiting the tumor hypoxia response.

Somatic EGFR mutations and efficacy of tyrosine kinase inhibitors in NSCLC

Early clinical studies of tyrosine kinase inhibitors (TKIs) that target the EGFR in patients with advanced non-small-cell lung cancer (NSCLC) showed that some patients experienced rapid, durable, complete or partial responses. These data were the basis for attempts to identify specific subgroups of patients who would further benefit from these agents. The discovery of somatic mutations in EGFR that correlated with sensitivity to TKIs identified a plausible explanation for these observations. Clinical and pathological factors such as female sex, never having smoked, Asian origin and adenocarcinoma histology correlate with the presence of EGFR mutations and objective responses to TKIs in patients with NSCLC. Recent studies in metastatic colorectal cancer highlighted that somatic mutations in KRAS represent a negative predictor of response to anti-EGFR monoclonal antibodies; KRAS mutations also represent an important mechanism of resistance to TKIs in NSCLC. Many large clinical studies are currently investigating the predictive and prognostic value of EGFR mutational status and other candidate biomarkers. We summarize the literature and present an overview of the field of anti-EGFR therapy in NSCLC, focusing on the influence of somatic EGFR mutations on selection of patients for TKI therapy and the influence of EGFR pathway regulation.

Expression of the receptor tyrosine kinase EphA2 is increased in smokers and predicts poor survival in non-small cell lung cancer

PURPOSE

Up-regulation of the receptor tyrosine kinase EphA2 has been shown in several epithelial cancers. Epidermal growth factor receptor (EGFR) and K-Ras have been reported to regulate EphA2 in several in vitro models, but this regulation has never been examined in tumors from patients. Because of the established importance of EGFR and K-Ras mutations in non-small cell lung cancer (NSCLC), we investigated the relationship between these mutations and EphA2 in this cancer type. The significance of EphA2 expression was further examined by testing for correlation with other clinical parameters.

EXPERIMENTAL DESIGN

EphA2 expression was analyzed by immunohistochemistry in tissue microarray format using surgically resected NSCLC specimens (n = 279). EGFR and K-Ras mutation status was determined for most specimens. The correlation between EphA2 expression and EGFR or K-Ras mutation status was examined, along with several clinicopathologic variables of the tumors. The effects of increasing EGFR and K-Ras activity on EphA2 expression and activity were examined in two cell lines.

RESULTS

EphA2 expression was detected in >90% of tumor samples. Expression of EphA2 was positively correlated with activated EGFR but not with EGFR mutations. EphA2 expression was increased in patients harboring K-Ras mutations. EphA2 expression was positively correlated with a history of smoking, and high EphA2 scores predicted poorer progression-free and overall survivals.

CONCLUSIONS

EphA2 expression in NSCLC is associated with K-Ras mutations, EGFR activation, smoking history, and poor prognosis. EphA2 expression is up-regulated in the context of EGFR or K-Ras activation. The potential of EphA2 as a therapeutic target for NSCLC should be further investigated.

Detection of K-Ras mutations in tumour samples of patients with non-small cell lung cancer using PNA-mediated PCR clamping

Non-small cell lung cancers (NSCLC), in particular adenocarcinoma, are often mixed with normal cells. Therefore, low sensitivity of direct sequencing used for K-Ras mutation analysis could be inadequate in some cases. Our study focused on the possibility to increase the detection of K-Ras mutations in cases of low tumour cellularity. Besides direct sequencing, we used wild-type hybridisation probes and peptide-nucleic-acid (PNA)-mediated PCR clamping to detect mutations at codons 12 and 13, in 114 routine consecutive NSCLC frozen surgical tumours untreated by targeted drugs. The sensitivity of the analysis without or with PNA was 10 and 1% of tumour DNA, respectively. Direct sequencing revealed K-Ras mutations in 11 out of 114 tumours (10%). Using PNA-mediated PCR clamping, 10 additional cases of K-Ras mutations were detected (21 out of 114, 18%, P<0.005), among which five in samples with low tumour cellularity. In adenocarcinoma, K-Ras mutation frequency increased from 7 out of 55 (13%) by direct sequencing to 15 out of 55 (27%) by clamped-PCR (P<0.005). K-Ras mutations detected by these sensitive techniques lost its prognostic value. In conclusion, a rapid and sensitive PCR-clamping test avoiding macro or micro dissection could be proposed in routine analysis especially for NSCLC samples with low percentage of tumour cells such as bronchial biopsies or after neoadjuvant chemotherapy.

Prognostic implication of EGFR, KRAS, and TP53 gene mutations in a large cohort of Japanese patients with surgically treated lung adenocarcinoma

INTRODUCTION

Although mutation of the epidermal growth factor receptor (EGFR) gene is predictive for the response to EGFR-tyrosine kinase inhibitor, its prognostic impact for patients without EGFR-tyrosine kinase inhibitor treatment remains controversial. We examined for EGFR, KRAS or TP53 mutations in a consecutive large cohort of patients with lung adenocarcinoma, and evaluated their prognostic impact.

METHODS

We analyzed 397 patients with lung adenocarcinoma who underwent potentially curative pulmonary resection. Total ribonucleic acid was extracted and direct sequencing of each gene was performed after reverse transcription-polymerase chain reaction.

RESULTS

We found that 196 patients (49%) had EGFR mutations. Of these, 83 were exon 19 deletions (42%) and 92 were L858R (47%). Univariate analysis showed that patients with EGFR mutations survived for a longer period than those without mutations (p = 0.0046). However, there was no difference in overall survival between the patients with exon 19 deletion and those with L858R (p = 0.4144). Patients with KRAS mutations or TP53 mutations tended to survive for a shorter period (p = 0.2183 and 0.0230, respectively). Multivariate analysis using the Cox proportional hazards model revealed that smoking status (p = 0.0310) and disease stage (p < 0.0001) were independent prognostic factors. However, none of the gene mutations was independent prognostic factors (EGFR, p = 0.3225; KRAS, p = 0.8500; TP53, p = 0.3191).

CONCLUSIONS

EGFR, KRAS, and TP53 gene mutations were not independently associated with the prognosis for Japanese patients with surgically treated lung adenocarcinoma.

Prognostic value of KRAS mutations and Ki-67 expression in stage I lung adenocarcinomas

The purpose of the present study was to establish accurate prognostic markers to predict the post-operative recurrence of stage I lung adenocarcinomas (ADC). One-hundred and ninety cases of stage I ADC were examined for KRAS mutations and Ki-67 expression, and their associations with disease recurrence were analyzed. KRAS-mutated cases showed a significantly higher risk of recurrence than cases without mutations (5-year disease-free survival (DFS) 61.0% vs. 85.8%, P=0.017: adjusted Hazard ratio (HR) 4.55, 95% Confidence Interval (CI) 1.61-12.82, P=0.004). Ki-67 high-expressers (labeling index >10%) also showed a higher risk of recurrence than low-expressers (5-year DFS 68.7% vs. 93.2%, P<0.001: adjusted HR 3.84, 95% CI 1.18-12.45, P=0.025). Ki-67 high-expressers with KRAS mutations showed an additional higher risk of recurrence compared to low-expressers without mutations (5-year DFS 37.5% vs. 93.3%, P<0.001: adjusted HR 16.82, 95% CI 3.77-74.98, P<0.001) and their 5-year DFS was nearly equivalent to that of stage II non-small cell lung cancer (NSCLC) in our facility (37.5% vs. 37.2% for stage II NSCLC, p=0.577). The combined use of KRAS status and Ki-67 expression level could be an excellent prognostic marker to predict the post-operative recurrence of stage I ADC.

K-ras mutation predictive significance in platinum based chemotherapeutic protocols in patients with advanced non-small cell lung cancer

Beckground/Aim. K-ras oncogene is mutated in about 20% of lung cancer. The purpose of this study was to investigate the predictive significance for therapeutic response of K-ras mutations in advanced non-small cell lung cancer (NSCLC) patients. Methods. Bronchial aspirate samples were assessed prior to platinum-based chemotherapy start in 39 patients with stage IIIb or IV NSCLC. K-ras mutations at codons 12 and 13 were analyzed by single strand conformation polymorphisam (SSCP) and allele specific oligonucleozide hybridisation of polymerase chain reaction (PCR) of the patient's DNA present in bronchial aspirate. After two cycles of chemotherapy the patients were subjected to response evaluation. Results. Of 39 patients 10 (25.5%) demonstrated K-ras mutations, while 29 (74.4%) patients had not. There were no significant differences between these two groups of patients with respect to baseline patient characteristics. Partial response to the therapy had 16 (41%), no changes 14 (36%), and progressive disease 9 (23%) patients. There was a tendency to higher response rate for patients without K-ras mutations versus those with mutations, but not statistically significant (p = 0.14). Conclusion. There was no significant predictive value for therapeutic response of K-ras mutations for advanced non-small cell lung cancer.

KRAS mutational testing in the selection of patients for EGFR-targeted therapies

The small-molecule epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors and the anti-EGFR monoclonal antibodies have proven activity in lung and colorectal adenocarcinomas, respectively, but only a small fraction of patients exhibit significant responses. The observation that only a minority of patients respond to EGFR-targeted therapies, in combination with their toxicity and high costs, has driven the search for molecular markers predictive of response. The main focus of the present review is the recent discovery that mutations in the KRAS oncogene constitute a negative predictive marker in this clinical setting, namely that their presence can be used to predict which patients are unlikely to benefit from treatment with EGFR-directed therapy.

Regression of drug-resistant lung cancer by the combination of rosiglitazone and carboplatin

PURPOSE

Current therapy for lung cancer involves multimodality therapies. However, many patients are either refractory to therapy or develop drug resistance. KRAS and epidermal growth factor receptor (EGFR) mutations represent some of the most common mutations in lung cancer, and many studies have shown the importance of these mutations in both carcinogenesis and chemoresistance. Genetically engineered murine models of mutant EGFR and KRAS have been developed that more accurately recapitulate human lung cancer. Recently, using cell-based experiments, we showed that platinum-based drugs and the antidiabetic drug rosiglitazone (PPARgamma ligand) interact synergistically to reduce cancer cell and tumor growth. Here, we directly determined the efficacy of the PPARgamma/carboplatin combination in these more relevant models of drug resistant non-small cell lung cancer.

EXPERIMENTAL DESIGN

Tumorigenesis was induced by activation of either mutant KRAS or EGFR. Mice then received either rosiglitazone or carboplatin monotherapy, or a combination of both drugs. Change in tumor burden, pathology, and evidence of apoptosis and cell growth were assessed.

RESULTS

Tumor burden remained unchanged or increased in the mice after monotherapy with either rosiglitazone or carboplatin. In striking contrast, we observed significant tumor shrinkage in mice treated with these drugs in combination. Immunohistochemical analyses showed that this synergy was mediated via both increased apoptosis and decreased proliferation. Importantly, this synergy between carboplatin and rosiglitazone did not increase systemic toxicity.

CONCLUSIONS

These data show that the PPARgamma ligand/carboplatin combination is a new therapy worthy of clinical investigation in lung cancers, including those cancers that show primary resistance to platinum therapy or acquired resistance to targeted therapy.

Molecular systems biology of ErbB1 signaling: bridging the gap through multiscale modeling and high-performance computing

The complexity in intracellular signaling mechanisms relevant for the conquest of many diseases resides at different levels of organization with scales ranging from the subatomic realm relevant to catalytic functions of enzymes to the mesoscopic realm relevant to the cooperative association of molecular assemblies and membrane processes. Consequently, the challenge of representing and quantifying functional or dysfunctional modules within the networks remains due to the current limitations in our understanding of mesoscopic biology, i.e., how the components assemble into functional molecular ensembles. A multiscale approach is necessary to treat a hierarchy of interactions ranging from molecular (nm, ns) to signaling (microm, ms) length and time scales, which necessitates the development and application of specialized modeling tools. Complementary to multiscale experimentation (encompassing structural biology, mechanistic enzymology, cell biology, and single molecule studies) multiscale modeling offers a powerful and quantitative alternative for the study of functional intracellular signaling modules. Here, we describe the application of a multiscale approach to signaling mediated by the ErbB1 receptor which constitutes a network hub for the cell's proliferative, migratory, and survival programs. Through our multiscale model, we mechanistically describe how point-mutations in the ErbB1 receptor can profoundly alter signaling characteristics leading to the onset of oncogenic transformations. Specifically, we describe how the point mutations induce cascading fragility mechanisms at the molecular scale as well as at the scale of the signaling network to preferentially activate the survival factor Akt. We provide a quantitative explanation for how the hallmark of preferential Akt activation in cell-lines harboring the constitutively active mutant ErbB1 receptors causes these cell-lines to be addicted to ErbB1-mediated generation of survival signals. Consequently, inhibition of ErbB1 activity leads to a remarkable therapeutic response in the addicted cell lines.

Biomarkers in lung cancer: from early detection to novel therapeutics and decision making

Lung cancer remains a significant cause of mortality worldwide. While advances in therapy continue to be made, the overall prognosis for patients diagnosed with lung cancer remains poor. Historically, markers such as age, performance status and disease stage have been used to risk-stratify patients and guide therapeutic decisions. These parameters provide some useful information, but more sensitive markers are clearly needed. Molecular and genetic studies have identified several such markers, which appear to play critical roles in carcinogenesis and affect patient outcomes. This article reviews a number of biomarkers that have been identified in lung cancer, and their prognostic and predictive roles.

Effect of disrupting seven-in-absentia homolog 2 function on lung cancer cell growth

BACKGROUND

Hyperactivated epidermal growth factor receptor (EGFR) and/or RAS signaling drives cellular transformation and tumorigenesis in human lung cancers, but agents that block activated EGFR and RAS signaling have not yet been demonstrated to substantially extend patients' lives. The human homolog of Drosophila seven-in-absentia--SIAH-1 and SIAH-2--are ubiquitin E3 ligases and conserved downstream components of the RAS pathway that are required for mammalian RAS signal transduction. We examined whether inhibiting SIAH-2 function blocks lung cancer growth.

METHODS

The antiproliferative and antitumorigenic effects of lentiviral expression of anti-SIAH-2 molecules (ie, a dominant-negative protease-deficient mutant of SIAH-2 [SIAH-2(PD)] and short hairpin RNA [shRNA]-mediated gene knockdown against SIAH-2) were assayed in normal human lung epithelial BEAS-2B cells and in human lung cancer BZR, A549, H727, and UMC11 cells by measuring cell proliferation rates, by assessing MAPK and other activated downstream components of the RAS pathway by immunoblotting, assessing apoptosis by terminal deoxynucleotidyltransferase-mediated UTP end-labeling (TUNEL) assay, quantifying anchorage-independent cell growth in soft agar, and assessing A549 cell-derived tumor growth in athymic nude mice (groups of 10 mice, with two injections of 1 x 10(6) cells each at the dorsal left and right scapular areas). All statistical tests were two-sided.

RESULTS

SIAH-2 deficiency in human lung cancer cell lines reduced MAPK signaling and statistically significantly inhibited cell proliferation compared with those in SIAH-proficient cells (P < .001) and increased apoptosis (TUNEL-positive A549 cells 3 days after lentivirus infection: SIAH-2(PD) vs control, 30.1% vs 0.0%, difference = 30.1%, 95% confidence interval [CI] = 23.1% to 37.0%, P < .001; SIAH-2-shRNA#6 vs control shRNA, 27.9% vs 0.0%, difference = 27.9%, 95% CI = 23.1% to 32.6%, P < .001). SIAH-2 deficiency also reduced anchorage-independent growth of A549 cells in soft agar (mean number of colonies: SIAH-2(PD) vs control, 124.7 vs 57.3, difference = 67.3, 95% CI = 49.4 to 85.3, P < .001; shRNA-SIAH-2#6 vs shRNA control: 27.0 vs 119.7, difference = 92.7, 95% CI = 69.8 to 115.5, P < .001), and blocked the growth of A549 cell-derived tumors in nude mice (mean tumor volume on day 36 after A549 cell injection: SIAH-2(PD) infected vs uninfected, 191.0 vs 558.5 mm(3), difference = 367.5 mm(3), 95% CI = 237.6 to 497.4 mm(3), P < .001; SIAH-2(PD) infected vs control infected, 191.0 vs 418.3 mm(3), difference = 227.5 mm(3), 95% CI = 87.4 to 367.1 mm(3), P = .003; mean resected tumor weight: SIAH-2(PD) infected vs uninfected, 0.12 vs 0.48 g, difference = 0.36 g, 95% CI = 0.23 to 0.50 g, P < .001; SIAH-2(PD) infected vs control infected, 0.12 vs 0.29 g, difference = 0.17 g, 95% CI = 0.04 to 0.31 g, P = .016).

CONCLUSIONS

SIAH-2 may be a viable target for novel anti-RAS and anticancer agents aimed at inhibiting EGFR and/or RAS-mediated tumorigenesis.

The impact of additional prognostic factors on survival and their relationship with the anatomical extent of disease expressed by the 6th Edition of the TNM Classification of Malignant Tumors and the proposals for the 7th Edition

PURPOSE

To identify, in the international staging database of the International Association for the Study of Lung Cancer, those prognostic factors that were significant and independent of clinical stage.

MATERIAL AND METHODS

From the data submitted to the staging data base concerning 100,869 patients, cases were selected for which all the following variables were available: clinical stage, age, gender, performance status (PS), and histologic cell types. For non-small cell lung cancer (NSCLC), 12,428 patients were assessable, and for SCLC, 6609 patients were available for this study. Methods used were Cox regression analyses and recursive partitioning and amalgamation analyses.

RESULTS

PS appeared to be a very important prognostic factor for survival in addition to clinical stage. Age and gender were other independent significant variables; For NSCLC and SCLC separately, recursive partitioning and amalgamation allowed the identification of four groups of patients with differing prognoses. In advanced NSCLC (stage IIIB / IV), some routine laboratory tests (mainly white blood cells and hypercalcaemia) were also found to be significant prognostic variables. In SCLC, albumin was an independent biologic prognostic factor.

CONCLUSION

In addition to stage, PS and, to a lesser extent, age and gender seem to be important prognostic factors for survival in lung cancer. Although this data was obtained from the largest series ever used for such an analysis in lung cancer, these prognostic factors and models require confirmation in the prospective study already planned by the International Association for the Study of Lung Cancer Lung Cancer Staging Project.

Cis-acting genomic elements of the Pas1 locus control Kras mutability in lung tumors

The Pas1 locus is the major tumor modifier of lung tumorigenesis in mouse inbred strains. Of six genes contained in a conserved haplotype, three (Casc1, Kras and Ifltd1) have been proposed as Pas1 candidates, but mechanistic evidence is sparse. Herein, we examined urethane-induced lung tumorigenesis in a new mouse model developed by replacing the Kras gene with an Hras gene in the susceptible A/J-type Pas1 locus and crossing these mice with either C57BL/6J or A/J mice. Heterozygous mice carrying the Hras-replacement gene were more susceptible than wild-type mice to lung carcinogenesis, indicating that Hras replacement not only compensates for Kras functions, but is more active. Indeed, most lung tumors carried a Gln61Leu mutation in the Hras-replacement gene, whereas no mutations were observed in the endogenous Hras gene. Thus, the context of the Kras locus determined mutability of ras genes. In mice carrying the Hras-replacement gene, the mutation frequency affecting the wild-type Kras gene was much higher when this gene was located in the A/J type than in the C57BL/6J-type Pas1 locus (12 versus 0%, -log P=5.0). These findings identify cis-acting elements in the Pas1 locus as the functional components controlling genetic susceptibility to lung tumorigenesis by modulating mutability of the Kras gene.

Role of network branching in eliciting differential short-term signaling responses in the hypersensitive epidermal growth factor receptor mutants implicated in lung cancer

We study the effects of EGFR inhibition in wild-type and mutant cell lines upon tyrosine kinase inhibitor TKI treatment through a systems level deterministic and spatially homogeneous model to help characterize the hypersensitive response of the cancer cell lines harboring constitutively active mutant kinases to inhibitor treatment. By introducing a molecularly resolved branched network systems model (the molecular resolution is introduced for EGFR reactions and interactions in order to distinguish differences in activation between wild-type and mutants), we are able to quantify differences in (1) short-term signaling in downstream ERK and Akt activation, (2) the changes in the cellular inhibition EC50 associated with receptor phosphorylation (i.e., 50% inhibition of receptor phosphorylation in the cellular context), and (3) EC50 for the inhibition of activated downstream markers ERK-(p) and Akt-(p), where (p) denotes phosphorylated, upon treatment with the inhibitors in cell lines carrying both wild-type and mutant forms of the receptor. Using the branched signaling model, we illustrate a possible mechanism for preferential Akt activation in the cell lines harboring the oncogenic mutants of EGFR implicated in non-small-cell lung cancer and the enhanced efficacy of the inhibitor erlotinib especially in ablating the cellular Akt-(p) response. Using a simple phenomenological model to describe the effect of Akt activation on cellular decisions, we discuss how this preferential Akt activation is conducive to cellular oncogene addiction and how its disruption can lead to dramatic apoptotic response and hence remarkable inhibitor efficacies. We also identify key network nodes of our branched signaling model through sensitivity analysis as those rendering the network hypersensitive to enhanced ERK-(p) and Akt-(p); intriguingly, the identified nodes have a strong correlation with species implicated in oncogenic transformations in human cancers as well as in drug resistance mechanisms identified for the inhibitors in non-small-cell lung cancer therapy.

Prognostic versus predictive value of biomarkers in oncology

Numerous options are currently available for tumour typing. This has raised intense interest in the elucidation of prognostic and predictive markers. A prognostic biomarker provides information about the patients overall cancer outcome, regardless of therapy, whilst a predictive biomarker gives information about the effect of a therapeutic intervention. A predictive biomarker can be a target for therapy. Amongst the genes that have proven to be of relevance are well-known markers such as ER, PR and HER2/neu in breast cancer, BCR-ABL fusion protein in chronic myeloid leukaemia, c-KIT mutations in GIST tumours and EGFR1 mutations in NSCLC. Several reasons for the difficult elucidation of new markers will be addressed including the involvement of cellular pathways in tumour biology instead of single genes and interference in disease outcome as a result of anticancer therapies. Future perspectives for the development of prognostic and predictive markers will be given.