Qualitative and quantitative analysis of carcinogenic mutations in circulating tumor DNA (ctDNA) plays a unique role in the early screening and precise diagnosis of cancer. Herein, we introduced an electrochemical-enrichment assisted amplification refractory mutation system-quantitative real-time PCR (EC-ARMS-qPCR) assay to detect the BRAF V600E carcinogenic mutation of thyroid cancer in plasma samples. Cell-free DNA (cfDNA) were firstly enriched by an electric field-driven adsorption and desorption process, and then ctDNA in cfDNA were analyzed by a designed allele-specific qPCR assay. The EC-ARMS-qPCR assay provides good sensitivity and specificity for the identification of single nucleotide polymorphisms (SNPs) of BRAF V600E mutant ctDNA in a complex system, which can detect as low as 2 BRAF V600E mutant copies in Tris buffer and 25 BRAF V600E mutant copies in Tris buffer containing 50% plasma with a allele frequency of 0.01% (i.e., mutant-to-wild-type ratio of 1: 9999). The assay was assessed in plasma samples of patients with papillary thyroid cancer (PTC) and benign thyroid nodule (TN). The EC-ARMS-qPCR assay detected 40.74% and 10.00% BRAF V600E mutation ctDNA in plasma samples of 54 PTC patients and 20 TN patients, respectively. The overall concordance between BRAF V600E mutant ctDNA by EC-ARMS-qPCR assay and BRAF V600E mutant of matched pathological tissue genes by fine needle aspiration biopsy (FNAB) is 73.08%, suggesting that the EC-ARMS-qPCR assay is appropriate for detecting carcinogenic mutations in liquid biopsy samples.
Highly accurate analysis of single-nucleotide polymorphisms (SNPs) plays an important role in both disease diagnostics and personalized medicine development. In this work, a DNA microarray-based resonance light scattering (RLS) assay has been developed for multiplexed detection of papillary thyroid carcinoma (PTC) related mutation points including BRAFV600E (t1m), NRAS codon 61 (t2m), TERT promoter g.1295228 (t31m) and TERT promoter g.1295250 (t32m) with high sensitivity and selectivity by the attachment of polyvalent ssDNA modified 13 nm gold nanoparticles (ssDNAs@GNPs) followed by silver deposition for signal enhancement. The microarray-based RLS assay provides a detection limit (S/N = 3) at the sub-nanomolar level for the target ssDNAs and determines allele frequencies as low as 0.2% for t1m, 0.2% for t2m, 0.5% for t31m, and 0.5% for t32m in the cocktail of target ssDNAs, respectively. The practicability of the DNA microarray-based RLS assay is demonstrated by profiling of t2m in 50 clinical thyroid tissue samples of PTC patients, and satisfactory results are obtained.
Background Identifying the high recurrence group of patients with early-stage papillary thyroid cancer (PTC) is the greatest challenge in the management of this disease. It has been noted that B-type Rafkinase (BRAF) V600E mutation and programmed death ligand 1 (PD-L1) are associated in PTC and highly expressed in PTC, correlating in PTC as potential prognostic biomarkers. However, whether they can be used to predict the aggressiveness and recurrence of early PTC remains unclear. Methods Clinicopathological data of 137 patients with early PTC [tumor-node-metastasis (TNM) stage I–II] who underwent surgery in Zhejiang Cancer Hospital between 2008 and 2010 were retrospectively analyzed. BRAF V600E mutation and PD-L1 was detected by immunohistochemistry. The median follow-up time was 136 months (interquartile range 5.8). The presence of tumor confirmed by imaging or pathology or lymph node metastasis was considered as tumor recurrence. The association of both alone and in combination with clinicopathological features and recurrence was statistically analyzed respectively. The risk of recurrence was assessed using Cox regression models. Results Most of the 137 early PTC were female (78.1%). The mean age was 43.2±12.1 years. The median tumor size was 1.4 cm; 14 patients developed recurrence during follow-up period; 56 patients (40.9%) were detected positive for BRAF V600E mutation; 76 patients (55.5%) were detected positive for PD-L1. Patients with both BRAF V600E mutation and PD-L1 expression had larger tumors (P=0.038), were more likely to have extrathyroidal invasion (P=0.045), and had a lower rate of cervical lymph node metastasis (P=0.046). The recurrence rate was 17.5% (7/40) in patients with BRAF V600E mutation and PD-L1 double expression compared to 8.9% (4/45) in patients with BRAF V600E mutation and PD-L1 double negative [hazard ratio (HR) =1.267; 95% CI: 0.841–1.909; P=0.257]. Survival curves showed flatter recurrence-free survival (RFS) curves in positive BRAF V600E mutation only and PD-L1 expression only, whereas decreased sharply in positive expression of both BRAF V600E mutation and PD-L1; however, the differences were not significant (P>0.05). Conclusions The combination of BRAF V600E mutation and PD-L1 to identify group at higher risk of recurrence in early PTC has insufficient clinical evidence and should be used with caution in the clinical management of PTC.
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