Targeting epidermal growth factor receptor (EGFR) through tyrosine kinase inhibitors (TKI) is a successful therapeutic strategy in non-small cell lung cancer. However, the response to TKI therapy depends on specific activating and acquired mutations in the tyrosine kinase domain of the EGFR gene. Therefore, confirming the EGFR status of patients is crucial, not only for determining the eligibility, but also for monitoring the emergence of mutations in patients under TKI therapy. In this study, our aim was to develop a cost effective, yet sensitive, technique that allows the detection of therapeutically-relevant EGFR hotspot mutations at isothermal conditions in a non-invasive manner. Previously, we developed an allele-specific loop-mediated isothermal amplification (AS-LAMP) assay for screening germline and somatic de novo T790M EGFR mutation in lung cancer patients. In this study, we used cell free DNA as a template in AS-LAMP assay (CF-LAMP) for non-invasive detection of two hotspot EGFR mutations (T790M, and L858R) and compared its efficiency with ultrasensitive droplet digital PCR (ddPCR) assay. The results of CF-LAMP assay were consistent with those obtained in ddPCR assay, indicating the robustness of the method. CF-LAMP may serve as a valuable and cost-effective alternative for liquid biopsy techniques used in molecular diagnosis of non-small cell lung cancer.

INTRODUCTION: Targeted therapy using specific inhibitors against tyrosine kinases (TKs) is a paradigm in non-small-cell lung cancer management. However, the success of TK inhibitor (TKI) therapy depends on certain activating or acquired mutations, which render sensitivity or resistance to TKIs in the patients. The acquisition of epidermal growth factor receptor (EGFR) T790M point mutation is the most common mechanism of resistance to TKI in non-small cell lung cancer. A number of molecular strategies are now available for molecular testing of non-small cell lung cancers. However, almost all of them are cost-intensive and laborious and require high-end advanced equipment. Thus, assays that are rapid, simple, and cost-effective, yet sensitive, are most ideal in clinical settings for screening such therapeutically relevant mutations. MATERIALS AND METHODS: Allele-specific loop-mediated isothermal amplification assay (AS-LAMP), which is a variant of the original LAMP assay, is a promising diagnostic technique for screening single-nucleotide polymorphisms. Using commercially available plasmid constructs as template DNA, AS-LAMP assay for EGFR T790M mutation was optimized with six different sets of reaction mixture containing varying concentrations of buffer and primers. The results of AS-LAMP assay were further validated by ultrasensitive droplet digital polymerase chain reaction. RESULTS: Only one of the six sets of reaction mixture could accurately distinguish between wild type and mutated DNA, indicating that the primers and buffer are the two most critical components that determine the accuracy of AS-LAMP. The optimized AS-LAMP assay was further used to screen germ line and somatic T790M mutations in non-small cell lung cancer using blood and tissue samples collected from patients. CONCLUSION: Development of an accurate and rapid diagnostic assay that can detect resistant mutations without the need for sequencing is highly useful for clinicians in deciding on the eligibility of patients for TKI therapy. Considering its several inherent advantages, AS-LAMP assay could become an effective molecular tool for screening baseline or acquired EGFR T790M mutations in non-small cell lung cancer patients.

Background: Oral Squamous Cell Carcinoma (OSCC) is the most widely reported cancer worldwide. Liquid biopsy, a method that relies on identification of tumor-associated cells and/or cell free nucleic acids from body fluids is becoming increasingly popular in cancer diagnostics. The aim of the study was to evaluate the feasibility of Oral Rub and Rinse (ORR) technique in determining the genetic changes in common biomarkers of oral cancer such as TP53 using DNA obtained from saliva of oral cancer patients. Methods: A total of 15 oral cancer patients were recruited in the study and pre-surgical saliva samples were collected using the ORR technique. Tissue samples included in the study were obtained during the surgical excision of the cancerous oral lesion. Genomic DNA was isolated from the salivary cell plug and the tissues and the TP53 gene was amplified by PCR. The PCR products of all the exons of TP53 (Exons 2 to 11) were electrophoresed on agarose gel, purified and sequenced by Sanger method. The obtained sequences were compared with the reference sequence of TP53 gene. Statistical analysis used: Descriptive statistics were used and reported as frequency and percentage. Results: Capillary sequencing of TP53 gene from tissue DNA revealed the presence of codon 72 c.215C>G (p.Pro72Arg) polymorphism in 10 patients (67%) and a heterozygous mutation at codon 172 c.514 G>T (p.Val172Phe) in 2 patients (13%). Among the 10 samples that showed codon 72 polymorphism, matched salivary DNA was available for 6 samples and 4 out of these showed same genetic change at codon 72. Similarly, of the 3 samples that showed codon 172 mutation, matched salivary DNA was available for 1 sample and the mutation status was identical. Conclusion: The results suggest a potential for clinical applications of ORR technique as an alternative to invasive tissue biopsy for detection of genetic changes in candidate biomarkers in oral cancer.