Droplet Digital PCR as a Molecular Tool for the Detection of the EGFR T790M Mutation in NSCLC Patients with the EGFR Activating Mutations.

Background: Almost 50% of NSCLC patients who initially show a successful response to tyrosine kinase inhibitors targeted therapy (TKI therapy) eventually develop acquired EGFR T790M mutation. The T790M secondary mutation can cause resistance to the targeted therapy and disease relapse. Since this mutation can be present at very low frequencies in liquid biopsy samples, droplet digital PCR (ddPCR), due to its high sensitivity, has opened the possibility for minimally invasive monitoring of the disease during TKI targeted therapy. Materials and methods: For this study, a total of 45 plasma samples from NSCLC patients with previously detected EGFR-activating mutations were analyzed. Extracted circulating free DNA was amplified and examined for the presence of T790M mutation using ddPCR technology. For the data analysis, QuantaSoft Software was used. Results: Of 45 tested plasma samples, a total of 14 samples were identified as positive for the T790M mutation. The same samples eventually showed the presence of T790M mutation in FFPE. Droplet digital PCR showed its great advantage in high sensitivity detection of rare allele variants. Our ddPCR assay detected T790M mutant allele in frequencies from 0.1%. The average number of droplets generated by ddPCR was 9571. Conclusion: Monitoring of the T790M mutation has an important role in the examination of the effects of the prescribed TKI therapy. Since monitoring of potential changes during TKI therapy requires repeated sampling, our results showed that ddPCR technology has made it possible to use liquid biopsy as an adequate minimally invasive alternative for single nucleotide polymorphisms (SNP) detection.

Bosnian population data for the 15 STR loci in the Power Plex 16 kit.

The PowerPlex 16 amplification kit was used for the analysis of allele frequencies for the 15 STR loci (D3S1358, TH01, D21S11, D18S51, Penta E, D5S818, D13S317, D7S820, D16S539, CSF1PO, Penta D, VWA, D8S1179, TPOX and FGA) in unrelated, autochthonous healthy adults from Bosnia ( n=123 for TH01, Penta E, D16S539, CSF1PO, Penta D and TPOX, n=210 for D3S1358, D21S11, D18S51, D5S818, D13S317, D7S820, VWA, D8S1179 and FGA). The agreement with HWE was confirmed for all loci with the exception of Penta D (based on the chi(2)-test only). The combined power of discrimination (PD) and the combined power of exclusion (PE) for the 15 studied loci were 0.999999999999999997 and 0.999999, respectively.

[Optimization of HIV diagnosis using the RT-PCR (gag) method with various dilutions of cDNA and MgCl2 molarity]. / Optimizacija HIV-RT-PCR (GAG) metoda koristenjem razlicitih razrjedenja cDNA i MgCl2 molariteta.

Lack of optimum conditions for PCR can lead to absence of desired PCR products, undefined multiplication and appearance of unwanted products. So, the use of PCR aiming to generate large amounts of target nucleic acid sequences, may be so called "double-edged sword". The important parameters in optimisation of PCR methodology are annealing temperatures, Mg++ concentration and different dilutions of target sequences. In our optimization experiments of HIV-RT-PCR (GAG) method we used HIV positive plasma specimens for extraction of RNA and production of cDNA by reverse transcriptase. Different cDNA dilution (10(-1)-10(-10)) and MgCl2 molarity (1.25 mM; 1.5 mM; 5.0 mM) we used for first round (GAG1 and GAG4 outer primers) and second round PCR (GAG2 and GAG3 inner primers). Optimal results after 3% NuSieve agarose gel electrophoresis and detection of 413 pb PCR products were obtained with 1.25 mM MgCl2 and cDNA dilution 10(-1) and 10(-2). So the main aim of PCR optimisation is the achievement of optimal primer template binding and primer extension.