Correlation of genes associated with drug response to prognosis of large cell lung carcinoma

Reliable detection of rare mutations in EGFR gene codon L858 by PNA-LNA PCR clamp in non-small cell lung cancer

PNA-LNA PCR clamp real-time PCR method represents allele-specific approach to mutation analysis of EGFR gene in NSCLC. Due to its unique design, it is characterized by exceptionally high specificity and sensitivity but also allows detection of rare or not specifically-targeted EGFR mutations within examined exons, otherwise undetectable by other mutation-specific fluorescent probes. We herein present two cases of rare mutations revealed by PNA-LNA PCR clamping of NSCLC samples referred for routine EGFR gene molecular diagnostics. In one, the EGFR gene L858 codon mutation was detected by standard PNA-LNA PCR clamping, subsequently reconfirmed and characterized by direct sequencing of allele specific amplification products as the missense mutation c.2572C>A (p.L858M) paired with L861Q mutation on the same allele (in cis). In the second sample, low quality FFPE material from pleural biopsy, c.2573C>T missense mutation (p.L858P) was revealed. Still, repeated DNA analysis by PNA-LNA PCR clamp and direct sequencing demonstrated low level of mutant allele existing in a total allele pool suggesting rather artifactual c.2572C>T transition, a phenomenon quite frequent in low-volume FFPE samples upon fixation procedures. In conclusion, superior sensitivity and unique design of PNA-LNA PCR clamping are crucial for its excellent diagnostic effectiveness. As we demonstrated, the method allows detecting rare EGFR mutations, although it increases the risk of detection of a very low signal, e.g., generated by a small pool of mutated allele. Therefore, applicability of PNA-LNA PCR clamp product for the direct sequencing reevaluation is of key importance enabling reliable validation of results.

Relationship between epidermal growth factor receptor gene mutation and copy number in Chinese patients with non-small cell lung cancer

Epidermal growth factor receptor (EGFR) gene mutation and copy number are useful predictive markers that guide the selection of non-small cell lung cancer (NSCLC) patients for EGFR-targeting therapy. This study aimed to investigate the correlation between EGFR gene mutation and copy number and clinicopathologic characteristics of Chinese patients with NSCLC. NSCLC specimens collected from 205 patients between November 2009 and January 2011 were selected to detect EGFR gene mutations with real-time polymerase chain reaction (RT-PCR) and to detect EGFR gene copy number with fluorescence in situ hybridization (FISH). EGFR mutations primarily occurred in females, non-smokers, and patients with adenocarinomas (all P < 0.001). Tissues from 128 (62%) patients were FISH-positive for EGFR, including 37 (18%) with gene amplification and 91 (44%) with high polysomy. EGFR gene mutation was correlated with FISH-positive status (R = 0.340, P < 0.001). Multivariate analysis showed that not smoking (OR = 5.910, 95% CI = 2.363–14.779, P < 0.001) and having adenocarcinoma (OR = 0.122, 95% CI = 0.026–0.581, P = 0.008) were favorable factors for EGFR gene mutation. These results show a high frequency of EGFR FISH positivity in NSCLC tissues from Chinese patients and a significant relevance between EGFR gene mutations and FISH-positive status. Among the FISH-positive samples, EGFR gene mutation occurred more frequently in samples with gene amplification compared to those with high polysomy, suggesting that EGFR mutation and gene amplification should be used as clinical decision parameters to predict response to EGFR-targeting therapy.

Molecular pathology of lung cancer: key to personalized medicine

The majority of lung adenocarcinoma patients with epidermal growth factor receptor- (EGFR) mutated or EML4-ALK rearrangement-positive tumors are sensitive to tyrosine kinase inhibitors. Both primary and acquired resistance in a significant number of those patients to these therapies remains a major clinical problem. The specific molecular mechanisms associated with tyrosine kinase inhibitor resistance are not fully understood. Clinicopathological observations suggest that molecular alterations involving so-called 'driver mutations' could be used as markers that aid in the selection of patients most likely to benefit from targeted therapies. In this review, we summarize recent developments involving the specific molecular mechanisms and markers that have been associated with primary and acquired resistance to EGFR-targeted therapy in lung adenocarcinomas. Understanding these mechanisms may provide new treatment avenues and improve current treatment algorithms.