Lung cancer in never smokers: molecular profiles and therapeutic implications

Significance of smoking history and FDG uptake for pathological N2 staging in clinical N2-negative non-small-cell lung cancer

BACKGROUND

This study was conducted to evaluate whether smoking history and the standardized uptake value (SUV) of 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG) uptake are associated with unexpected pathological N2 status (pN2) in non-small-cell lung cancer (NSCLC).

PATIENTS AND METHODS

We analyzed the data of 220 patients who underwent surgical resection with clinical N2-negative status on computed tomography (CT) and positron emission tomography (PET)-CT. The maximum SUV of primary tumor was chosen for logistic analysis.

RESULTS

Seventy-two patients (33%) had never smoked. The SUV ranged from 1.0 to 29.0 (median 9.1). In univariate analysis, adenocarcinomas (P = 0.019), female gender (P = 0.010), N1 on CT (P = 0.025), and N1 PET-CT (P = 0.001) were associated with a high probability of pN2. The proportion of pN2 in never smokers was higher than in ever smokers (26% versus 10% respectively; P = 0.002). The SUV remained on a multivariate logistic model (odds ratio 1.1; 95% confidence interval 1.0-1.2; P = 0.010) and it had a better predictive value in never smokers than in ever smokers (P = 0.017).

CONCLUSIONS

This study indicates an association between smoking history and pN2 in clinically negative N2 NSCLC. The different roles of FDG uptake were also suggested based on smoking history.

Genomic aberrations in lung adenocarcinoma in never smokers

Background

Lung cancer in never smokers would rank as the seventh most common cause of cancer death worldwide.

Methods and Findings

We performed high-resolution array comparative genomic hybridization analysis of lung adenocarcinoma in sixty never smokers and identified fourteen new minimal common regions (MCR) of gain or loss, of which five contained a single gene (MOCS2, NSUN3, KHDRBS2, SNTG1 and ST18). One larger MCR of gain contained NSD1. One focal amplification and nine gains contained FUS. NSD1 and FUS are oncogenes hitherto not known to be associated with lung cancer. FISH showed that the amplicon containing FUS was joined to the next telomeric amplicon at 16p11.2. FUS was over-expressed in 10 tumors with gain of 16p11.2 compared to 30 tumors without that gain. Other cancer genes present in aberrations included ARNT, BCL9, CDK4, CDKN2B, EGFR, ERBB2, MDM2, MDM4, MET, MYC and KRAS. Unsupervised hierarchical clustering with adjustment for false-discovery rate revealed clusters differing by the level and pattern of aberrations and displaying particular tumor characteristics. One cluster was strongly associated with gain of MYC. Another cluster was characterized by extensive losses containing tumor suppressor genes of which RB1 and WRN. Tumors in that cluster frequently harbored a central scar-like fibrosis. A third cluster was associated with gains on 7p and 7q, containing ETV1 and BRAF, and displayed the highest rate of EGFR mutations. SNP array analysis validated copy-number aberrations and revealed that RB1 and WRN were altered by recurrent copy-neutral loss of heterozygosity.

Conclusions

The present study has uncovered new aberrations containing cancer genes. The oncogene FUS is a candidate gene in the 16p region that is frequently gained in never smokers. Multiple genetic pathways defined by gains of MYC, deletions of RB1 and WRN or gains on 7p and 7q are involved in lung adenocarcinoma in never smokers.

Associations between polymorphisms in DNA repair genes and TP53 mutations in non-small cell lung cancer

This study was conducted to identify genetic factors predisposing to TP53 mutations in patients with non-small cell lung cancer (NSCLC). A comprehensive panel of potentially functional single nucleotide polymorphisms (SNPs) in DNA repair genes was evaluated in relation to TP53 mutations. Thirty-seven SNPs in 28 DNA repair genes were genotyped by a sequenome mass spectrometry-based genotyping assay in 173 NSCLCs and the associations with TP53 mutations in the entire coding exons (exons 2-11), including splicing sites of the gene, were analyzed. Four SNPs (XPA rs1800975, OGG1 rs1052133, ADPRT rs1136410, and NBS1 rs1805794) were significantly associated with the prevalence of TP53 mutations in multivariate analysis for each SNP. When the 4 SNPs were combined, the prevalence of TP53 mutations was increased as the number of bad genotypes increased (P(trend)=0.001). Patients with 3 and 4 bad genotypes had a significantly higher frequency of TP53 mutations than those with 0-1 bad genotypes (adjusted odds ratio=5.18, 95% confidence interval=1.51-17.81, P=0.01 and adjusted odds ratio=18.26, 95% confidence interval=2.87-116.09, P=0.002, respectively). These findings suggest that the 4 SNPs may modulate the occurrence of TP53 mutations and contribute to lung carcinogenesis. However, larger studies are required to confirm our findings in other ethnic populations.

Spectrum of LKB1, EGFR, and KRAS mutations in chinese lung adenocarcinomas

INTRODUCTION

Somatic LKB1 mutations are found in lung adenocarcinomas at different frequencies in Caucasian and East Asian (Japanese and Korean) populations. This study was designed to characterize the frequency of LKB1 mutations, their relationship to EGFR and KRAS mutations, and their associated clinicopathologic characteristics in Chinese patients.

METHODS

Two hundred thirty-nine lung adenocarcinomas consecutively collected from October 2007 to July 2009 were dissected into 3 to 4 small (3 mm) pieces for histopathological analyses of tumor content. Genomic DNA and/or cDNA from 86 samples with more than 70% tumor content were used for sequencing of LKB1 (exons 1-9), EGFR (exons 18-21), and KRAS (exon 2). LKB1 germline mutation status was determined by sequencing of genomic DNA from matched histologically distant lung tissues that are histologically normal.

RESULTS

6.9% of lung adenocarcinomas harbored LKB1 somatic mutations. A total of 10.5% of patients had an LKB1 germline polymorphism, F354L. Interestingly, in two of these patients, tumors displayed loss of heterozygosity at this allele. EGFR kinase domain and KRAS mutations were found in 66.3% and 2.3% of Chinese lung adenocarcinomas, respectively. Concurrent LKB1 and EGFR somatic mutations were observed in one patient. Both KRAS-mutant tumors harbored LKB1 mutations.

CONCLUSIONS

These data provide important clinical and molecular characteristics of lung adenocarcinomas from Chinese patients.

cIAP2 upregulated by E6 oncoprotein via epidermal growth factor receptor/phosphatidylinositol 3-kinase/AKT pathway confers resistance to cisplatin in human papillomavirus 16/18-infected lung cancer

PURPOSE

Inhibitors of antiapoptosis protein (IAP) have been implicated in the resistance to cisplatin. Therefore, verifying which pathway is involved in cIAP2 upregulation may be helpful in finding a feasible pathway inhibitor to increase the chemotherapeutic efficacy in human papillomavirus (HPV)-infected lung cancer.

EXPERIMENTAL DESIGN

Specific inhibitors of different pathways were used to verify which pathway is involved in cIAP2 transcription. cIAP2 promoter fragments with various deletions and/or mutations were constructed by site-directed mutagenesis. cIAP2, epidermal growth factor receptor (EGFR), and phospho-AKT (p-AKT) expressions in 136 lung tumors were evaluated by immunohistochemistry.

RESULTS

Our data show that two NF-κB (-209 to -200 and -146 to -137) and one CREB (cyclic AMP-responsive element binding protein; -52 to -42) binding sites in cIAP2 promoter region were responsible for cIAP2 upregulated by E6 in TL-1 cells. Moreover, CREB was phosphorylated by EGFR/phosphatidylinositol 3-kinase (PI3K) pathway. To test the involvement of cIAP2 on cisplatin resistance, IC(50) was lowered to 8.6 μmol/L in TL-1 cells with cIAP2 short hairpin RNA (shRNA) transfection and compared with 39.7 μmol/L in TL-1 cells with nonspecific shRNA. Pretreatment with EGFR or PI3K inhibitor in TL-1 cells diminished the resistance to cisplatin. Among the tumor groups, cIAP2 expression correlated significantly with HPV16/18 E6, EGFR, and p-AKT. We followed up 46 of 136 patients who had tumor recurrence and/or metastasis and underwent chemotherapy. Tumors with cIAP2-positive immunostaining were associated with a poorer tumor response to chemotherapy compared with those with negative immunostaining.

CONCLUSIONS

cIAP2 upregulated by E6 via EGFR/PI3K/AKT cascades may contribute to cisplatin resistance, revealing that the EGFR or PI3K inhibitor combined with cisplatin may improve the chemotherapeutic efficacy in HPV-infected lung cancer.

Gender-related disparities in non-small cell lung cancer

Epidemiological studies clearly outline some disparities in cancer onset, progression as well as prognosis and therapeutic response between sexes. In particular, in lung cancer, the leading cause of cancer death, at least in Western countries, a gender disparity appears now to emerge, especially for non-small cell lung cancer (NSCLC). Such a disparity is apparently due to a variety of mechanisms, ranging from genetic and epigenetic differences to gender-specific lifestyle as well as to behavioral causes and, clearly, to sex hormones activity. Here we briefly recapitulate gender differences in terms of risk factors, histopathological features and pathogenetic mechanisms in NSCLC, and hypothesize that a gender-oriented pharmacology could beneficially impact on innovative therapeutic strategies.

Identification of a novel biomarker, SEMA5A, for non-small cell lung carcinoma in nonsmoking women

BACKGROUND

Although cigarette smoking is the major risk factor for lung cancer, only 7% of female lung cancer patients in Taiwan have a history of smoking. The genetic mechanisms of carcinogenesis in nonsmokers are unclear, but semaphorins have been suggested to play a role as lung tumor suppressors. This report is a comprehensive analysis of the molecular signature of nonsmoking female lung cancer patients in Taiwan, with a particular focus on the semaphorin gene family.

METHODS

Sixty pairs of tumor and adjacent normal lung tissue specimens were analyzed by using Affymetrix U133plus2.0 expression arrays. Differentially expressed genes in tumor tissues were identified by a paired t test and validated by reverse transcriptase-PCR and immunohistochemistry. Functional analysis was conducted by using Ingenuity Pathway Analysis as well as gene set enrichment analysis and sigPathway algorithms. Kaplan-Meier survival analyses were used to evaluate the association of SEMA5A expression and clinical outcome.

RESULTS

We identified 687 differentially expressed genes in non-small cell lung carcinoma (NSCLC). Many of these genes, most notably the semaphorin family, were participants in the axon guidance signaling pathway. The downregulation of SEMA5A in tumor tissue, both at the transcriptional and translational levels, was associated with poor survival among nonsmoking women with NSCLC.

CONCLUSIONS

In summary, several semaphorin gene family members were identified as potential therapeutic targets, and SEMA5A may be useful as a prognostic biomarker for NSCLC, which may also be gender specific in Taiwanese patients.

IMPACT

A novel biomarker for NSCLC is identified.

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: a call to action

The causative association between tobacco use and lung cancer is a well-established fact. However, lung cancer also occurs, at surprisingly high rates, in lifelong never smokers. In fact, lung cancer in never smokers is among the leading causes of cancer-related mortality. This CCR Focus summarizes recent data, identifies knowledge deficits, and suggests future research directions with regard to this critically important subset of lung cancer patients.

Lung cancer biomarkers: FISHing in the sputum for risk assessment and early detection

This perspective on Varella-Garcia et al. (beginning on p. 447 in this issue of the journal) discusses the role of sputum-based biomarkers in the risk assessment and early detection of lung cancer. The importance of the detection of sputum epithelial chromosomal aneusomy by fluorescence in situ hybridization (FISH) as a potential risk or early-detection biomarker is discussed in the context of other biomarkers and models in lung carcinogenesis. The presently reported findings on FISH in sputum cells are an important contribution worthy of further investigation in defined clinical settings.

Tobacco, Genetic Susceptibility and Lung cancer

Exposure to tobacco smoke is an established risk factor for lung cancer, although a possible role for genetic susceptibility in the development of lung cancer has been inferred from familial clustering of the disease and segregation analysis. Findings of familial aggregation and statistical evidence for a major susceptibility gene have led to the search for high penetrant, rare, single genes and low penetrant, high frequency susceptibility genes for lung cancer. The relatively small number of linkage studies conducted to date, have identified potential lung cancer susceptibility loci on chromosomes 6q, 12p, and 19q. A variety of studies have examined single nucleotide polymorphisms of several low penetrant, high frequency genes encoding for enzymes involved in the metabolism of carcinogens and DNA damage repair, as likely candidate susceptibility genes. These studies have produced somewhat conflicting findings and, when significant, only modest associations have been reported. Relatively few studies have looked for potential gene-environment interactions, explored associations between two or more genetic polymorphisms or evaluated interactions between genetic polymorphisms and endogenous risk factors. Few large scale genome wide association studies conducted recently have provided evidence that common variation on chromosome 15q25.1, 5p15.33 and 6p21.33 influences lung cancer risk and cancer types with strong environmental risk factors. It is hoped that newer research strategies, selecting candidate genes within pathways and genotype at multiple markers within a gene, employing new technologies, may allow complete coverage of the variation within candidate genes in multiple pathways and to unravel the genetic susceptibility to lung cancer. This knowledge could, in turn, be used to identify persons at risk, to individualize treatments such as chemoprevention, to personalize harms of smoking and to motivate cessation.

Lung cancer in never smokers: clinical epidemiology and environmental risk factors

More than 161,000 lung cancer deaths are projected to occur in the United States in 2008. Of these, an estimated 10 to 15% will be caused by factors other than active smoking, corresponding to 16,000 to 24,000 deaths annually. Thus lung cancer in never smokers would rank among the most common causes of cancer mortality in the United States if considered as a separate category. Slightly more than half of the lung cancers caused by factors other than active smoking occur in never smokers. As summarized in the accompanying article, lung cancers that occur in never smokers differ from those that occur in smokers in their molecular profile and response to targeted therapy. These recent laboratory and clinical observations highlight the importance of defining the genetic and environmental factors responsible for the development of lung cancer in never smokers. This article summarizes available data on the clinical epidemiology of lung cancer in never smokers, and several environmental risk factors that population-based research has implicated in the etiology of these cancers. Primary factors closely tied to lung cancer in never smokers include exposure to known and suspected carcinogens including radon, second-hand tobacco smoke, and other indoor air pollutants. Several other exposures have been implicated. However, a large fraction of lung cancers occurring in never smokers cannot be definitively associated with established environmental risk factors, highlighting the need for additional epidemiologic research in this area.