Dataset Information

Polymorphisms in intron 1 of the EGFR gene in non-small cell lung cancer patients.

ABSTRACT: The epidermal growth factor receptor (EGFR) gene is highly polymorphic and its expression and activity may be affected by various polymorphisms. There have been several studies examining associations between EGFR polymorphisms and clinical outcome of lung cancer therapy; however, the underlying mechanism is largely unknown. The present study investigated EGFR polymorphism status and its correlation with clinicopathological features in Japanese non-small cell lung cancer (NSCLC) patients. We investigated 5 polymorphisms in the EGFR gene (-216G/T, -191C/A, 8227G/A, D994D and R497K) in 274 surgically-treated NSCLC patients. TaqMan single nucleotide polymorphism (SNP) genotyping assays and a PCR-based assay were used to analyze these polymorphisms. In our cohort of patients we did not find any evidence of the -191C/A polymorphism. Our results showed that the patients with the 8227GA or AA type in intron 1 had a significantly better prognosis with the anti-EGFR therapy than the patients with the GG type (p=0.0448) in terms of recurrence of lung cancer. No significant association was observed between 3 other SNPs (-216G/T, D994D and R497K) and clinicopathological features. The EGFR 8227G/A polymorphism in intron 1 may be associated with clinical outcome in NSCLC patients treated with EGFR tyrosine kinase inhibitors.

SUBMITTER: Shitara M

PROVIDER: S-EPMC3493703 | biostudies-literature | 2012 Nov

REPOSITORIES: biostudies-literature

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Polymorphisms in intron 1 of the EGFR gene in non-small cell lung cancer patients.

Shitara Masayuki M Sasaki Hidefumi H Yokota Keisuke K Okuda Katsuhiro K Hikosaka Yu Y Moriyama Satoru S Yano Motoki M Kawaguchi Tomoya T Kubo Akihito A Takada Minoru M Kitahara Naoto N Okumura Meinoshin M Matsumura Akihide A Iuchi Keiji K Fujii Yoshitaka Y

Experimental and therapeutic medicine 20120823 5

The epidermal growth factor receptor (EGFR) gene is highly polymorphic and its expression and activity may be affected by various polymorphisms. There have been several studies examining associations between EGFR polymorphisms and clinical outcome of lung cancer therapy; however, the underlying mechanism is largely unknown. The present study investigated EGFR polymorphism status and its correlation with clinicopathological features in Japanese non-small cell lung cancer (NSCLC) patients. We inve ...[more]

PMID: 23226726

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Project description:BackgroundThe epidermal growth factor receptor (EGFR) gene is the prototype member of the type I receptor tyrosine kinase (TK) family and plays a pivotal role in cell proliferation and differentiation. There are three well described polymorphisms that are associated with increased protein production in experimental systems: a polymorphic dinucleotide repeat (CA simple sequence repeat 1 [CA-SSR1]) in intron one (lower number of repeats) and two single nucleotide polymorphisms (SNPs) in the promoter region, -216 (G/T or T/T) and -191 (C/A or A/A). The objective of this study was to examine distributions of these three polymorphisms and their relationships to each other and to EGFR gene mutations and allelic imbalance (AI) in non-small cell lung cancers.Methods and findingsWe examined the frequencies of the three polymorphisms of EGFR in 556 resected lung cancers and corresponding non-malignant lung tissues from 336 East Asians, 213 individuals of Northern European descent, and seven of other ethnicities. We also studied the EGFR gene in 93 corresponding non-malignant lung tissue samples from European-descent patients from Italy and in peripheral blood mononuclear cells from 250 normal healthy US individuals enrolled in epidemiological studies including individuals of European descent, African-Americans, and Mexican-Americans. We sequenced the four exons (18-21) of the TK domain known to harbor activating mutations in tumors and examined the status of the CA-SSR1 alleles (presence of heterozygosity, repeat number of the alleles, and relative amplification of one allele) and allele-specific amplification of mutant tumors as determined by a standardized semiautomated method of microsatellite analysis. Variant forms of SNP -216 (G/T or T/T) and SNP -191 (C/A or A/A) (associated with higher protein production in experimental systems) were less frequent in East Asians than in individuals of other ethnicities (p < 0.001). Both alleles of CA-SSR1 were significantly longer in East Asians than in individuals of other ethnicities (p < 0.001). Expression studies using bronchial epithelial cultures demonstrated a trend towards increased mRNA expression in cultures having the variant SNP -216 G/T or T/T genotypes. Monoallelic amplification of the CA-SSR1 locus was present in 30.6% of the informative cases and occurred more often in individuals of East Asian ethnicity. AI was present in 44.4% (95% confidence interval: 34.1%-54.7%) of mutant tumors compared with 25.9% (20.6%-31.2%) of wild-type tumors (p = 0.002). The shorter allele in tumors with AI in East Asian individuals was selectively amplified (shorter allele dominant) more often in mutant tumors (75.0%, 61.6%-88.4%) than in wild-type tumors (43.5%, 31.8%-55.2%, p = 0.003). In addition, there was a strong positive association between AI ratios of CA-SSR1 alleles and AI of mutant alleles.ConclusionsThe three polymorphisms associated with increased EGFR protein production (shorter CA-SSR1 length and variant forms of SNPs -216 and -191) were found to be rare in East Asians as compared to other ethnicities, suggesting that the cells of East Asians may make relatively less intrinsic EGFR protein. Interestingly, especially in tumors from patients of East Asian ethnicity, EGFR mutations were found to favor the shorter allele of CA-SSR1, and selective amplification of the shorter allele of CA-SSR1 occurred frequently in tumors harboring a mutation. These distinct molecular events targeting the same allele would both be predicted to result in greater EGFR protein production and/or activity. Our findings may help explain to some of the ethnic differences observed in mutational frequencies and responses to TK inhibitors.

Project description:BackgroundThe rapid aging of the population in Japan has been accompanied by an increased rate of surgery for lung cancer among elderly patients. It is thus an urgent priority to map out a treatment strategy for elderly patients with primary lung cancer. Although surgical resection remains standard treatment for early stage non-small-cell lung cancer (NSCLC), it is now essential to confirm the status of epidermal growth factor receptor (EGFR) gene mutations when planning treatment strategies. Furthermore, several studies have reported that EGFR mutations are an independent prognostic marker in NSCLC. However, the relations between age group and the molecular and pathological characteristics of NSCLC remain unclear. We studied the status of EGFR mutations in elderly patients with NSCLC and examined the relations of EGFR mutations to clinicopathological factors and outcomes according to age group.MethodsA total of 388 consecutive patients with NSCLC who underwent complete tumor resection in our hospital from 2006 through 2008 were studied retrospectively. Formalin-fixed, paraffin-embedded tissue sections were used to isolate DNA from carcinoma lesions. Mutational analyses of EGFR gene exons 19, 20, and 21 and KRAS gene exons 12 and 13 were performed by loop-hybrid mobility shift assay, a highly sensitive polymerase chain reaction-based method.ResultsEGFR mutations were detected in 185 (47.7%) and KRAS mutations were detected in 33 (8.5%) of the 388 patients. EGFR mutations were found in a significantly higher proportion of patients younger than 80 years (younger group; 178/359, 49.6%) than in patients 80 years or older (older group; 7/29, 24.1%) (P = 0.008). In contrast, KRAS mutations were more common in the older group (6/29, 20.7%) than in the younger group (27/359, 7.5%) (P = 0.014). The older group showed a trend toward a higher rate of 5-year overall survival among elderly patients with EGFR mutations (100%) than among those with wild-type EGFR (66.2%), but the difference was not significant.ConclusionsOur results suggest that the EGFR status of patients with NSCLC differs between patients 80 years or older and those younger than 80 years. EGFR mutation status might be a prognostic marker in elderly patients with completely resected NSCLC.

Dataset Information

Polymorphisms in intron 1 of the EGFR gene in non-small cell lung cancer patients.

Publications

Polymorphisms in intron 1 of the EGFR gene in non-small cell lung cancer patients.

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