The molecular epidemiology of most EGFR and KRAS mutations in lung cancer remains unclear.
We genotyped 3026 lung adenocarcinomas for the major EGFR (exon 19 deletions and L858R) and KRAS (G12, G13) mutations and examined correlations with demographic, clinical and smoking history data.
EGFR mutations were found in 43% of never smokers (NS) and in 11% of smokers. KRAS mutations occurred in 34% of smokers and in 6% of NS. In patients with smoking histories up to 10 pack-years, EGFR predominated over KRAS. Among former smokers with lung cancer, multivariate analysis showed that, independent of pack-years, increasing smoking-free years raise the likelihood of EGFR mutation. NS were more likely than smokers to have KRAS G>A transition mutation (mostly G12D) (58% vs. 20%, p=0.0001). KRAS G12C, the most common G>T transversion mutation in smokers, was more frequent in women (p=0.007) and these women were younger than men with the same mutation (median 65 vs. 69, p=0.0008) and had smoked less.
The distinct types of KRAS mutations in smokers vs. NS suggest that most KRAS-mutant lung cancers in NS are not due to secondhand smoke exposure. The higher frequency of KRAS G12C in women, their younger age, and lesser smoking history together support a heightened susceptibility to tobacco carcinogens.
lung cancer; tobacco; EGFR; KRAS; molecular epidemiology
Mutations in the mitochondrial genome (mtgenome) have been associated with cancer and many other disorders. These mutations can be point mutations or deletions, or admixtures (heteroplasmy). The detection of mtDNA mutations in body fluids using resequencing microarrays, which are more sensitive than other sequencing methods, could provide a strategy to measure mutation loads in remote anatomical sites.
We determined the mtDNA mutation load in the entire mitochondrial genome of 26 individuals with different early stage cancers (lung, bladder, kidney) and 12 heavy smokers without cancer. MtDNA was sequenced from three matched specimens (blood, tumor and body fluid) from each cancer patient and two matched specimens (blood and sputum) from smokers without cancer. The inherited wildtype sequence in the blood was compared to the sequences present in the tumor and body fluid, detected using the Affymetrix Genechip® Human Mitochondrial Resequencing Array 1.0 and supplemented by capillary sequencing for noncoding region.
Using this high-throughput method, 75% of the tumors were found to contain mtDNA mutations, higher than in our previous studies, and 36% of the body fluids from these cancer patients contained mtDNA mutations. Most of the mutations detected were heteroplasmic. A statistically significantly higher heteroplasmy rate occurred in tumor specimens when compared to both body fluid of cancer patients and sputum of controls, and in patient blood compared to blood of controls. Only 2 of the 12 sputum specimens from heavy smokers without cancer (17%) contained mtDNA mutations. Although patient mutations were spread throughout the mtDNA genome in the lung, bladder and kidney series, a statistically significant elevation of tRNA and ND complex mutations was detected in tumors.
Our findings indicate comprehensive mtDNA resequencing can be a high-throughput tool for detecting mutations in clinical samples with potential applications for cancer detection, but it is unclear the biological relevance of these detected mitochondrial mutations. Whether the detection of tumor-specific mtDNA mutations in body fluidsy this method will be useful for diagnosis and monitoring applications requires further investigation.
The aim of the current study was to determine the clinical significance according to the subtypes of epidermal growth factor receptor (EGFR) mutations and presence of KRAS mutations in operable non-small-cell lung cancer (NSCLC). We sequenced exons 18-21 of the EGFR tyrosine kinase domain and examined mutations in codons 12 and 13 of KRAS in tissues of patients with NSCLC who had undergone surgical resection. EGFR mutations were more frequent in never-smokers than smokers (33% vs. 14%, respectively; p=0.009) and in females than in males (31% vs. 16%, respectively; p=0.036). Mutations in exon 18-19 and 20-21 were found in 10 and 22 patients, respectively. Never-smokers and broncho-alveolar cell carcinoma features were positively associated with a mutation in exon 18-19 (p=0.027 and 0.016, respectively). The five-year survival rate in patients with a mutation in exons 18-19 (100%) was higher than that in patients without such mutation (47%; p=0.021). KRAS mutations were found in 16 patients (12%) and were not related to the overall survival (p=0.742). Patients with an EGFR mutation in exons 18-19 had better survival than patients without such mutation. Subtypes of EGFR mutations may be prognostic factors in patients undergoing curative resection.
Carcinoma, Non-small-cell Lung; Receptor, Epidermal Growth Factor; Genes, Ras; Mutation
Mitochondrial DNA (mtDNA) mutations are reported in different tumors. However, there is no information on the temporal development of the mtDNA mutations/content alteration and their extent in normal and abnormal mucosa continuously exposed to tobacco smoke in lung cancer patients.
We examined the pattern of mtDNA alteration (mtDNA mutation and content index) in 25 airway mucosal biopsies, corresponding tumors and normal lymph nodes obtained from three patients with primary lung cancers. In addition, we examined the pattern of mtDNA mutation in corresponding tumors and normal lymph nodes obtained from eight other patients with primary lung cancers. The entire 16.5 kb mitochondrial genome was sequenced on Affymetrix Mitochip v2.0 sequencing platform in every sample. To examine mtDNA content index, we performed real-time PCR analysis.
The airway mucosal biopsies obtained from three lung cancer patients were histopathologically negative but exhibited multiple clonal mtDNA mutations detectable in the corresponding tumors. One of the patients was operated twice for the removal of tumor from the right upper and left lower lobe respectively within a span of two years. Both of these tumors exhibited twenty identical mtDNA mutations. MtDNA content increased significantly (P<0.001) in the lung cancer and all the histologically negative mucosal biopsies except one compared to the control lymph node.
Our results document the extent of massive clonal patches that develop in lifetime smokers and ultimately give rise to clinically significant cancers. These observations shed light on the extent of disease in the airway of smokers traceable through mtDNA mutation. MtDNA mutation could be a reliable tool for molecular assessment of respiratory epithelium exposed to continuous smoke as well as disease detection and monitoring. Functional analysis of the pathogenic mtDNA mutations may be useful to understand their role in lung tumorigenesis.
The present study aims at understanding the timing and nature of mitochondrial DNA (mtDNA) alterations in urothelial cell carcinoma (UCC) and their detection in urine sediments. The entire 16.5 kb mitochondrial genome was sequenced in matched normal lymphocytes, tumor and urine sediments from 31 UCC patients and compared with different clinical stages and histological grades. The mtDNA content index was examined in all the specimens. Sixty five percent (20/31) of the patients harbored at least 1 somatic mtDNA mutation. A total of 25 somatic mtDNA mutations were detected, which were more frequent in the respiratory complex coding regions (Complex-I, III, IV and V) of the mtDNA and significantly affected respiratory complex-III compared to the other complexes (P=0.021–0.039). Compared to stage Ta, mtDNA mutation was higher in stage T1 and significantly higher in stage T2 (P=0.01) patients. MtDNA mutation was also significantly higher (P=0.04) in stage T2 compared to stage T1 patients. Ninety percent (18/20) of the patients harboring mtDNA mutation in the tumor also had mutation in their urine sediments. Eighty percent (20/25) of the tumor-associated mtDNA mutations was detectable in the urine sediments. Compared to the normal lymphocytes, the mtDNA content increased significantly in the tumor (P=0.0013) and corresponding urine sediments (P=0.0025) in 19/25 (76%) patients analyzed. Our results indicate that mtDNA alterations occur frequently in progressive stages of UCC patients and are readily detectable in the urine sediments. MtDNA mutations appear to provide a promising tool for developing early detection and monitoring strategies for UCC patients.
Urothelial cell carcinoma; mitochondria; mtDNA alteration; urine detection
This study was designed to determine the relationship of cigarette smoking to the frequency and qualitative differences among KRAS mutations in lung adenocarcinomas from Korean patients.
Materials and Methods
Detailed smoking histories were obtained from 200 consecutively enrolled patients with lung adenocarcinoma according to a standard protocol. EGFR (exons 18 to 21) and KRAS (codons 12/13) mutations were determined via direct-sequencing.
The incidence of KRAS mutations was 8% (16 of 200) in patients with lung adenocarcinoma. KRAS mutations were found in 5.8% (7 of 120) of tumors from never-smokers, 15% (6 of 40) from former-smokers, and 7.5% (3 of 40) from current-smokers. The frequency of KRAS mutations did not differ significantly according to smoking history (p=0.435). Never-smokers were significantly more likely than former or current smokers to have a transition mutation (G→A or C→T) rather than a transversion mutation (G→T or G→C) that is known to be smoking-related (p=0.011). In a Cox regression model, the adjusted hazard ratios for the risk of progression with epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) were 0.24 (95% CI, 0.14-0.42; p<0.001) for the EGFR mutation and 1.27 (95% CI, 0.58-2.79; p=0.537) for the KRAS mutation.
Cigarette smoking did not influence the frequency of KRAS mutations in lung adenocarcinomas in Korean patients, but influenced qualitative differences in the KRAS mutations.
EGFR; KRAS; pulmonary adenocarcinoma; cigarette smoking; EGFR-tyrosine kinase inhibitors
We hypothesize that among patients with lung cancers the KRAS/EGFR mutation profile and overall survival of “collegiate smokers” (former smokers who smoked between 101 lifetime cigarettes and 5 pack years) are distinct from those of never smokers and former smokers with ≥ 15 pack years.
We collected age, sex, stage, survival, and smoking history for patients evaluated from 2004 to 2009 with advanced stage lung cancers and known KRAS/EGFR status. Mutation profile and overall survival were compared using Fisher’s exact test and log-rank test, respectively.
Data were available for 852 patients with advanced stage lung cancers with known KRAS/EGFR status. 6% were “collegiate smokers”, 36% were never smokers, and 30% were former smokers with ≥ 15 pack years. The mutation profile of “collegiate smokers” (15% KRAS mutations, 27% EGFR mutations) was distinct from those of never smokers (p < .001) and former smokers with ≥ 15 pack years (p < .001)and not significantly different from those of former smokers with 5 to 15 pack years (p = 0.9). Median overall survival for “collegiate smokers” was 25 months, compared to 32 months for never smokers (p = 0.4), 33 months for former smokers with 5–15 pack years (p = 0.48),and 21 months for former smokers with ≥ 15 pack years (p = 0.63).
“Collegiate smokers” with advanced stage lung cancers represent a distinct subgroup of patients with a higher frequency of KRAS mutations and lower frequency of EGFR mutations compared to never smokers. These observations reinforce the recommendation for routine mutation testing for all patients with lung cancers and that no degree of tobacco exposure is safe.
Collegiate Smokers; non-small cell lung cancers; epidermal growth factor receptor mutation; KRAS mutation
Background. In lung adenocarcinoma, the frequency of KRAS mutations is ethnicity dependent with a higher proportion in African Americans and white Caucasians than in Asians. The prevalence of these mutations among North Africans patients is unknown. The objective of this study was to report the frequency and spectrum of KRAS mutations in a group of Moroccan lung adenocarcinoma patients. Methods. Tumor specimens from 117 Moroccan patients with lung adenocarcinoma were selected to determine frequency and spectrum of KRAS mutations. KRAS mutations in codons 12 and 13 of exon 2 were analyzed using conventional DNA sequencing. Results. The overall frequency of the KRAS mutations was 9% (11/117). In the population with KRAS mutations, there was a trend towards more male (P = 0.06) and more smokers (P = 0.08) compared to patients with wild type KRAS. KRAS mutations were located at codon 12 in 10 out of 11 patients (91%). The G12C mutation was the most frequent KRAS mutation (73%). Conclusion. This is the first study to date examining the frequency and spectrum of KRAS mutations in lung adenocarcinomas in North African and Arab populations. KRAS mutation frequency in Moroccan patients was comparable with the frequency observed in East-Asian population. KRAS mutations are more likely observed in males and smokers and to be transversions. Further studies, in larger numbers of patients, are needed to confirm these findings.
Inherited susceptibility to lung cancer is understudied. Never smokers are an important subgroup of patients enriched for tumors harboring oncogene aberrations in the EGFR and ALK genes. We aimed to better characterize the incidence of family history of lung cancer among never smokers with NSCLC.
Clinicopathologic data, tumor genotype, family history of cancer, and specifically family history of lung cancer from 230 consecutive never smokers was retrospectively compiled and analyzed.
In our cohort, the median age was 56 years, 67% were women, 75% were white, 59% had advanced NSCLC and 87% had adenocarcinoma histology. In these tumors, 98/230 (42%) had an EGFR mutation, 17/155 (11%) had KRAS mutations and 27/127 (21%) had an ALK translocation. Family history of any cancer was common (57%) and specific family history of lung cancer was present in 42/230 cases (18%). The percentage of cases with family history of lung cancer was higher in the EGFR mutated versus EGFR wild-type NSCLCs. Out of the cases with a family history of any cancer, 22/53 (41.5%) EGFR mutated, 1/5 (20%) KRAS mutated and 3/19 (15.5%) ALK translocated cohorts had a family history of lung cancer. The ratio of family history of lung cancer to family history of cancer was significantly higher in the EGFR mutated cohort when compared to the ALK translocated plus KRAS mutated cohorts (p=0.039).
Family history of lung cancer is common in never smokers with NSCLC, and there seems to be a particular link in families in which the proband has an EGFR mutated tumor when compared to ALK translocated or KRAS mutated tumors. Further study of families with EGFR-mutated NSCLC may yield insights into the pathogenesis of this tumor type.
lung cancer; non-small-cell lung cancer; family history; never smokers; epidermal growth factor receptor; EGFR; anaplastic lymphoma kinase; ALK; KRAS
DNA alterations in mitochondria are believed to play a role in carcinogenesis and are found in smoking-related cancers. We sought to replicate earlier findings for the association of smoking with increased mitochondrial DNA (mtDNA) content in buccal cells and further hypothesized that there would be an increased number of somatic mtDNA mutations in smokers. Buccal cells and blood lymphocytes were studied from 42 healthy smokers and 30 non-smokers. Temporal temperature gradient electrophoresis screening and sequencing was used to identify mtDNA mutations. The relative mtDNA content was determined by real-time polymerase chain reaction. Assuming that mtDNA in lymphocytes represents the inherited sequence, it was found that 31% of smokers harbored at least one somatic mtDNA mutation in buccal cells with a total of 39 point mutations and 8 short deletions/insertions. In contrast, only 23% of non-smokers possessed mutations with a total of 10 point mutations and no insertions/deletions detected. mtDNA somatic mutation density was higher in smokers (0.68/10 000 bp per person) than in non-smokers (0.2/10 000 bp per person). There was a statistically significant difference in the pattern of homoplasmy and heteroplasmy mutation changes between smokers and non-smokers. Whereas non-smokers had the most mutations in D-loop region (70%), smokers had mutations in both messenger RNA encoding gene (36%) and D-loop region (49%). The mean ratio of buccal cells to lymphocytes of mtDNA content in smokers was increased (2.81) when compared with non-smokers (0.46). These results indicate that cigarette smoke exposure affects mtDNA in buccal cells of smokers. Additional studies are needed to determine if mitochondrial mutation assays provide new or complementary information for estimating cigarette smoke exposure at the cellular level or as a cancer risk biomarker.
EGFR mutations underlie the sensitivity of lung cancers to erlotinib and gefitinib and can occur in any patient with this illness. Here we examine the frequency of EGFR mutations in smokers and men.
We determined the frequency of EGFR mutations and characterized their association with cigarette smoking status and male sex.
We tested 2,142 lung adenocarcinoma specimens for the presence of EGFR exon 19 deletions and L858R. EGFR mutations were found in 15% of tumors from former smokers (181 of 1,218; 95% CI, 13% to 17%), 6% from current smokers (20 of 344; 95% CI, 4% to 9%), and 52% from never smokers (302 of 580; 95% CI, 48% to 56%; P < .001 for ever v never smokers). EGFR mutations in former or current smokers represented 40% of all those detected (201 of 503; 95% CI, 36% to 44%). EGFR mutations were found in 19% (157 of 827; 95% CI, 16% to 22%) of tumors from men and 26% (346 of 1,315; 95% CI, 24% to 29%) of tumors from women (P < .001). EGFR mutations in men represented 31% (157 of 503; 95% CI, 27% to 35%) of all those detected.
A large number of EGFR mutations are found in adenocarcinoma tumor specimens from men and people who smoked cigarettes. If only women who were never smokers were tested, 57% of all EGFR mutations would be missed. Testing for EGFR mutations should be considered for all patients with adenocarcinoma of the lung at diagnosis, regardless of clinical characteristics. This strategy can extend the use of EGFR tyrosine kinase inhibitors to the greatest number individuals with the potential for substantial benefit.
Epidermal growth factor receptor (EGFR) mutations are common in lung adenocarcinomas of never smokers, while KRAS mutations are more frequent among heavy smokers. Different clinicopathological and biological characteristics may, therefore, exist in lung adenocarcinoma according to smoking status. In the present study, a retrospective review was performed using 521 patients with surgically resected lung adenocarcinomas. The clinicopathological factors of age, gender, pathological tumor size, nodal status, lymphatic permeation and blood vessel invasion and the EGFR and KRAS mutation spectra were compared between never and heavy smokers. EGFR mutations were detected in 233 (45%) patients, while KRAS mutations were detected in 56 (11%) patients. EGFR-mutated adenocarcinomas had a higher prevalence of females in the never smokers compared with the heavy smokers (P<0.001). KRAS-mutated adenocarcinomas had a higher prevalence of females (P<0.001) and showed less frequent vascular invasion (P=0.018) in the never smokers compared with the heavy smokers. Minor EGFR mutations, excluding exon 21 L858R and exon 19 deletions, were more common in heavy smokers than never smokers (P=0.055). KRAS G to A transition was more common in never smokers, while KRAS G to T and G to C transversions were more common in heavy smokers (P=0.036). The clinicopathological characteristics and the spectra of the EGFR and KRAS mutations in lung adenocarcinoma were different between the never and heavy smokers. Further large-scale studies are required to evaluate the efficacy of molecular targeting agents with consideration to specific EGFR and KRAS mutations.
lung cancer; adenocarcinoma; smoking; epidermal growth factor receptor; KRAS; mutation
Mutations of the epidermal growth factor receptor (EGFR) in patients with non-small cell lung cancer (NSCLC) were identified by re-sequencing all exons of this gene to evaluate the frequencies of EGFR gene mutation and identify rare or novel EGFR mutations. A total of 55 NSCLC samples from 55 patients were included in the study. Genomic DNA was extracted and exons 1–28 of the EGFR gene were sequenced to identify mutations. The cDNA of the EGFR gene with P848L and T790M double mutants was constructed by introducing point mutations into the wild-type EGFR vector using a site-directed mutagenesis kit. Among the 55 patients with NSCLC, 8 patients carried mutations of the EGFR gene. Notably, of the mutation-harboring patients with a pathological type of adenocarcinoma, 6 were non-smokers. The in vitro study demonstrated that the P848L mutant had a similar response to that of the wild-type EGFR after gefitinib treatment, and the P848L and T790M double mutant exhibited high resistance to gefitinib. These EGFR mutations preferentially occurred in lung adenocarcinoma patients, most of whom were non-smokers. In the in vitro study, P848L mutant EGFR had a similar response as the wild-type EGFR to gefitinib treatment, suggesting that lung cancer patients with a rare mutation of EGFR, such as the P848L mutation, do not respond to gefitinib treatment.
non-small cell lung cancer; epidermal growth factor receptor; mutation; functional study
We report the results of whole genome and transcriptome sequencing of tumor and adjacent normal tissue samples from 17 patients with non-small cell lung carcinoma (NSCLC). We identified 3,726 point mutations and over 90 indels in the coding sequence, with an average mutation frequency more than 10-fold higher in smokers than in never-smokers. Novel alterations in genes involved in chromatic modification and DNA repair pathways were identified along with DACH1, CFTR, RELN, ABCB5, and HGF. Deep digital sequencing revealed diverse clonality patterns in both never smokers and smokers. All validated EFGR and KRAS mutations were present in the founder clones, suggesting possible roles in cancer initiation. Analysis revealed 14 fusions including ROS1 and ALK as well as novel metabolic enzymes. Cell cycle and JAK-STAT pathways are significantly altered in lung cancer along with perturbations in 54 genes that are potentially targetable with currently available drugs.
Although TP53 mutations have been widely studied in lung cancer, the majority of studies have focused on exons 5-8 of the gene. In addition, TP53 mutations in Korean patients with lung cancers have not been investigated. We searched for mutations in the entire coding exons, including splice sites of the gene, in Korean patients with non-small cell lung cancer (NSCLC). Mutations of the gene were determined by direct sequencing in 176 NSCLCs. Sixty-nine mutations (62 different mutations) were identified in 65 tumors. Of the 62 mutations, 12 were novel mutations. TP53 mutations were more frequent in males, ever-smokers and squamous cell carcinomas than in females, never-smokers and adenocarcinomas, respectively (all comparisons, P<0.001). Missense mutations were most common (52.2%), but frameshift, nonsense, and splice-site mutations were frequently observed at frequencies of 18.8%, 15.9% and 10.1%, respectively. Of the 69 mutations, 9 (13.0%) were found in the oligomerization domain. In addition, the proportion of mutations in the oligomerization domain was significantly higher in adenocarcinomas than in squamous cell carcinomas (23.5% vs. 2.9%, P=0.01). Our study provides clinical and molecular characteristics of TP53 mutations in Korean patients with NSCLCs.
Lung Neoplasms; Mutation; Genes, p53
We previously demonstrated that stage IIIB/IV non-small cell lung cancer (NSCLC) never smokers lived 50% longer than former/current smokers. This observation persisted after adjusting for age, performance status, and gender. We hypothesized that smoking-dependent differences in the distribution of driver mutations might explain differences in prognosis between these subgroups.
We reviewed 293 never smokers and 382 former/current smokers with lung adenocarcinoma who underwent testing for EGFR and KRAS mutations and rearrangements in ALK between 2009 and 2010. Clinical outcomes and patient characteristics were collected. Survival probabilities were estimated using the Kaplan-Meier method. Group comparison was performed with log-rank tests and Cox proportional hazards methods.
While the overall incidence of these mutations was nearly identical (55% never smokers vs. 57% current/former smokers, p=0.48), there were significant differences in the distribution of mutations between these groups: EGFR mutations- 37% never smokers vs. 14% former/current smokers (p<0.0001); KRAS mutations- 4% never smokers vs. 43% former/current smokers (p<0.0001); ALK rearrangements- 12% never smokers vs. 2% former/current smokers (p<0.0001). Among never smokers and former/current smokers, prognosis differed significantly by genotype. Patients harboring KRAS mutations demonstrated the poorest survival. Smoking status, however, had no influence on survival within each genotype.
Never smokers and former/current smokers with lung adenocarcinomas are not homogeneous subgroups. Each is made up of individuals whose tumors have a unique distribution of driver mutations which are associated with different prognoses, irrespective of smoking history.
non-small cell lung cancer; adenocarcinoma; EGFR; KRAS; ALK; never smoker
Activating mutations in Epidermal Growth Factor Receptor (EGFR) are common in lung adenocarcinoma of never smokers but are rare in other types of cancer. Here we have analysed mutations in exons 19 to 21 of EGFR and in exons 19 and 20 of the EGFR homolog HER2 in 54 cases of Esophageal Squamous Cell Carcinomas (ESCC) from patients recruited in Kashmir, India, a region of high incidence for this cancer. We report the detection of 3 mutations (6%) in the ATP-binding regulatory loops of the tyrosine kinase domain of EGFR (deletion 746–750, P753L, G719D). No mutation was found in HER2. This is the first report of activating EGFR mutations in ESCC, of the same type as those detected in lung adenocarcinoma of never-smokers. This suggests that a small proportion of ESCC patients in this high incidence area may benefit from treatment with EGFR tyrosine kinase inhibitors.
EGFR; Mutations; Esophageal Cancer; Kashmir
We previously showed that 90% (47 of 52; 95% CI, 0.79 to 0.96) of lung adenocarcinomas from East Asian never-smokers harbored well-known oncogenic mutations in just four genes: EGFR, HER2, ALK, and KRAS. Here, we sought to extend these findings to more samples and identify driver alterations in tumors negative for these mutations.
We have collected and analyzed 202 resected lung adenocarcinomas from never smokers seen at Fudan University Shanghai Cancer Center. Since mutations were mutually exclusive in the first 52 examined, we determined the status of EGFR, KRAS, HER2, ALK, and BRAF in stepwise fashion as previously described. Samples negative for mutations in these 5 genes were subsequently examined for known ROS1 fusions by RT-PCR and direct sequencing.
152 tumors (75.3%) harbored EGFR mutations, 12 (6%) had HER2 mutations, 10 (5%) had ALK fusions all involving EML4 as the 5′ partner, 4 (2%) had KRAS mutations, and 2 (1%) harbored ROS1 fusions. No BRAF mutation were detected.
The vast majority (176 of 202; 87.1%, 95% CI: 0.82 to 0.91) of lung adenocarcinomas from never smokers harbor mutant kinases sensitive to available TKIs. Interestingly, patients with EGFR mutant patients tend to be older than those without EGFR mutations (58.3 Vs 54.3, P = 0.016) and patient without any known oncogenic driver tend to be diagnosed at a younger age (52.3 Vs 57.9, P = 0.013). Collectively, these data indicate that the majority of never smokers with lung adenocarcinoma could benefit from treatment with a specific tyrosine kinase inhibitor.
African Americans have higher incidence and poorer response to lung cancer treatment compared with Caucasians. However, the underlying molecular mechanisms for the significant ethnic difference are not known. The present study examines the ethnic differences in the type and frequency of MET proto-oncogene (MET) mutation in lung cancer and correlated them with other frequently mutated genes such as epidermal growth factor receptor (EGFR), KRAS2, and TP53.
Using tumor tissue genomic DNA from 141 Asian, 76 Caucasian, and 66 African American lung cancer patients, exons coding for MET and EGFR were PCR amplified, and mutations were detected by sequencing. Mutation carriers were further screened for KRAS2 and TP53 mutations. Functional implications of important MET mutations were explored by molecular modeling and hepatocyte growth factor binding studies.
Unlike the frequently encountered somatic mutations in EGFR, MET mutations in lung tumors were germline. MET-N375S, the most frequent mutation of MET, occurred in 13% of East Asians compared with none in African Americans. The frequency of MET mutations was highest among male smokers and squamous cell carcinoma. The MET-N375S mutation seems to confer resistance to MET inhibition based on hepatocyte growth factor ligand binding, molecular modeling, and apoptotic susceptibility to MET inhibitor studies.
MET in lung cancer tissues contained nonsynonymous mutations in the semaphorin and juxtamembrane domains but not in the tyrosine kinase domain. All the MET mutations were germline. East Asians, African-Americans, and Caucasians had different MET genotypes and haplotypes. MET mutations in the semaphorin domain affected ligand binding.
The EML4-ALK fusion gene has been recently identified in a small subset of non-small cell lung cancer (NSCLC) patients who respond positively to ALK inhibitors. The characteristics of the EML4-ALK fusion gene in Chinese patients with NSCLC are poorly understood. Here, we report on the prevalence of EML4-ALK, EGFR status and KRAS mutations in 208 Chinese patients with NSCLC. EGFR mutations were found in 24.5% (51/208) of patients. In concordance with previous reports, these mutations were identified at high frequencies in females (47.5% vs 15.0% in males; P<0.05); never-smokers (42.3% vs 13.9% in smokers; P<0.05), and adenocarcinoma patients (44.2% vs 8.0% in non-adenocarcinoma patients; P<0.05). There were only 2.88% (6/208) patients with KRAS mutations in our study group. We identified 7 patients who harbored the EML4-ALK fusion gene (3.37%, 7/208), including 4 cases with variant 3 (57.1%), 2 with variant 1, and 1 with variant 2. All positive cases corresponded to female patients (11.5%, 7/61). Six of the positive cases were non-smokers (7.69%, 6/78). The incidence of EML4-ALK translocation in female, non-smoking adenocarcinoma patients was as high as 15.2% (5/33). No EGFR/KRAS mutations were detected among the EML4-ALK positive patients. Pathological analysis showed no difference between solid signet-ring cell pattern (4/7) and mucinous cribriform pattern (3/7) in ALK-positive patients. Immunostaining showed intratumor heterogeneity of ALK rearrangement in primary carcinomas and 50% (3/6) of metastatic tumors with ALK-negative staining. Meta-analysis demonstrated that EML4-ALK translocation occurred in 4.84% (125/2580) of unselected patients with NSCLC, and was also predominant in non-smoking patients with adenocarcinoma. Taken together, EML4-ALK translocations were infrequent in the entire NSCLC patient population, but were frequent in the NSCLC subgroup of female, non-smoker, adenocarcinoma patients. There was intratumor heterogeneity of ALK rearrangement in primary carcinomas and at metastatic sites.
Our previous study revealed that 90% (47 of 52; 95% CI: 0.79–0.96) of Chinese never-smokers with lung adenocarcinoma harbor known oncogenic driver mutations in just four genes: EGFR, ALK, HER2, and KRAS. Here, we examined the status of known driver mutations specifically in female never-smokers with lung adenocarcinoma.
Tumors were genotyped for mutations in EGFR, KRAS, ALK, HER2, and BRAF. Data on age, stage, tumor differentiation, histological subtypes, and molecular alterations were recorded from 349 resected lung adenocarcinomas from female never-smokers. We further compared the clinicopathological parameters according to mutational status of these genes.
Two hundred and sixty-six (76.2%) tumors harbored EGFR mutations, 16 (4.6%) HER2 mutations, 15 (4.3%) EML4-ALK fusions, seven (2.0%) KRAS mutations, and two (0.6%) BRAF mutations. In univariate analysis, patients harboring EGFR mutations were significantly older (p<0.001), whereas patients harboring HER2 mutations were significantly younger (p=0.036). Higher prevalence of KRAS (p=0.028) and HER2 (p=0.021) mutations was found in invasive mucinous adenocarcinoma (IMA). The frequency of EGFR mutations was positively correlated with acinar predominant tumors (p=0.002). Multivariate analysis revealed that older age at diagnosis (p=0.013) and acinar predominant subtype (p=0.005) were independent predictors of EGFR mutations. Independent predictors of HER2 mutations included younger age (p=0.030) and IMA (p=0.017). IMA (p=0.006) and poor differentiation (p=0.028) were independently associated with KRAS mutations.
The frequency of driver mutations in never-smoking female lung adenocarcinoma varies with histological subtypes and age at diagnosis. These data have implications for both clinical trial design and therapeutic strategies.
Lung adenocarcinoma; Female; Never smoker; EGFR mutation; HER2 mutation; Acinar; Mucinous; Age
Mitochondrial DNA (mtDNA) mutations were reported in primary head and neck squamous cell carcinoma (HNSCC) patients. However, very little information is available on the mtDNA mutation pattern in the histologically negative surgical margins and tumors of HNSCC patients who experienced tumor recurrence. The present study aimed at understanding the nature and timing of mtDNA mutation in histologically negative margins, and tumors in HNSCC patients who developed local recurrence during the follow ups. The entire 16.5-kb mitochondrial genome was sequenced in matched normal lymphocytes, histologically normal margins, and tumors of 50 recurrent HNSCC patients. The mtDNA mutations were then compared with clinical parameters. Forty-eight percent (24 of 50) patients harbored at least one somatic mtDNA mutation in the tumor, and a total of 37 somatic mtDNA mutations were detected. The mtDNA mutations were mostly heteroplasmic in nature and nucleotide transitions (A↔G; T↔C). Forty-six percent of the mutations (17 of 37) were detected in the tumors and were also detectable in the corresponding histologically normal margin of the patients. The mtDNA mutations involved both coding and noncoding regions of the mtDNA. Majority (9 of 17, 53%) of the noncoding mutations involved tRNAs. Seventy-five percent (15 of 20) of the coding mtDNA mutations were nonsynonymous in nature and mainly affected cytochrome c oxidase (Complex IV), frequently altered in different human mitochondrial diseases including cancer. Analysis of mtDNA mutation could be an invaluable tool for molecular assessment of histologically negative margins and as well for monitoring HNSCC patients with locoregional recurrences.
EGFR genotyping is now standard in the management of advanced lung adenocarcinoma, as this biomarker predicts marked benefit from treatment with EGFR tyrosine kinase inhibitors (TKIs). EGFR exon 19 insertions are a poorly described family of EGFR mutations, and their association with EGFR TKI-sensitivity in lung adenocarcinoma is uncertain.
Patients with lung cancers harboring EGFR exon 19 insertions were studied. The predicted effects of the insertions on the structure of the EGFR protein were examined, and EGFR exon 19 insertions were introduced into Ba/F3 cells to assess oncogenicity and in vitro sensitivity to EGFR TKIs. In patients receiving TKI, response magnitude was assessed with serial computed tomography (CT) measurement.
Twelve tumors harboring EGFR exon 19 insertions were identified; patients were predominately female (92%) and never-smokers (75%). The 11 specimens available for full sequencing all demonstrated an 18 bp insertion that resulted in the substitution of a Pro for Leu at residue 747. The mutant EGFR transformed the Ba/F3 cells, which were then sensitive to EGFR TKI. Six patients with measurable disease received TKI and 5 had a response on serial CT.
EGFR exon 19 insertions are a newly appreciated family of EGFR TKI-sensitizing mutations, and patients with tumors harboring these mutations should be treated with EGFR-TKI. While these mutations may be missed through the use of some mutation-specific assays, the addition of PCR product size analysis to multi-gene assays allows sensitive detection of both exon 19 insertion and deletion mutations.
Recent evidence suggests that the observed clinical distinctions between lung tumors in smokers and never smokers (NS) extend beyond specific gene mutations, such as EGFR, EML4-ALK, and KRAS, some of which have been translated into targeted therapies. However, the molecular alterations identified thus far cannot explain all of the clinical and biological disparities observed in lung tumors of NS and smokers. To this end, we performed an unbiased genome-wide, comparative study to identify novel genomic aberrations that differ between smokers and NS.
High resolution whole genome DNA copy number profiling of 69 lung adenocarcinomas from smokers (n = 39) and NS (n = 30) revealed both global and regional disparities in the tumor genomes of these two groups. We found that NS lung tumors had a greater proportion of their genomes altered than those of smokers. Moreover, copy number gains on chromosomes 5q, 7p, and 16p occurred more frequently in NS. We validated our findings in two independently generated public datasets. Our findings provide a novel line of evidence distinguishing genetic differences between smoker and NS lung tumors, namely, that the extent of segmental genomic alterations is greater in NS tumors. Collectively, our findings provide evidence that these lung tumors are globally and genetically different, which implies they are likely driven by distinct molecular mechanisms.
Germline polymorphisms may confer susceptibility to lung cancer in never smokers, but studies in the US have been limited by the low number of cases seen at single institutions. We hypothesized that we could use the Internet to bolster accrual of appropriate patients.
We established an Internet-based protocol to collect blood and information from patients throughout the U.S. To illustrate the power of this approach, we used these samples, plus additional cases and age-matched controls from Memorial Sloan-Kettering Cancer Center (New York, NY) and the Aichi Cancer Center (Nagoya, Japan), to analyze germline DNA for genetic variants reportedly associated with lung cancer susceptibility. The genotypes for the polymorphisms rs763317 (intron 1) and T790M (exon 20) in the EGFR gene were determined by direct sequencing, and CHRNA3 nicotinic acetylcholine receptor SNPs (rs8034191 and rs1051730) were genotyped as part of a pilot genome-wide association study.
We successfully analyzed germline DNA from 369 cases, including 45 obtained via the Internet, and 342 controls. A germline EGFR T790M variant was identified in 2 (0.54%, 95% CI: 0.21%–1.29%) of the 369 cases, and in none of the 292 controls (p=0.208). No difference was observed in EGFR rs763317 frequency between cases and controls. Similarly, neither CHRNA3 rs8034191 nor rs1051730 was associated with lung cancer risk.
The Internet provides a way to recruit patients throughout the country for minimal risk studies. This approach could be used to facilitate studies of germline polymorphisms in specific groups of patients with cancer.
Non-small cell lung cancer; EGFR; never smoker; genetic susceptibility; Internet