The potential of PIK3CA, KRAS, BRAF, and APC hotspot mutations as a non-invasive detection method for colorectal cancer.

BACKGROUND: Early diagnosis of colorectal cancer (CRC) can lead to prompt treatment modalities. Circulating cell-free DNA (cfDNA) analysis provides an alternative non-invasive procedure for the study of the molecular profiles of the corresponding tumor tissue. In this study, we aimed to investigate PIK3CA, KRAS, BRAF, and APC hotspot mutations in CRC tumor tissue, besides evaluating the diagnostic performance of KRAS, BRAF, and PIK3CA mutations in the plasma cfDNA. METHOD: Primary CRC tissue samples and paired plasma samples were collected from 70 patients. After DNA extraction, PCR-direct sequencing was used to screen for mutations in PIK3CA exon 9 and APC exon 15 in tumor tissues. Amplification Refractory Mutation System (ARMS)-quantitative PCR (qPCR) was used to evaluate KRAS codon 12 and 13, BRAF V600E, and PIK3CA exon 9 hotspot mutations. RESULTS: PIK3CA exon 9 hotspot mutations were detected in 47.1% of tumor tissues and 20% of paired plasma cfDNA samples by ARMS-qPCR method, while Sanger sequencing did not identify any mutation in PIK3CA exon 9. The KRAS exon 2 mutations were detected in 71.4% and 34.3% of tumor tissue samples and paired plasma cfDNA respectively. BRAF V600E mutation was observed in 17.1% and 4.3% of tissue DNA and plasma cfDNA respectively. A panel of PIK3CA, KRAS, and BRAF showed a sensitivity of 61% and a specificity of 100% (AUC = 0.803). APC hotspot mutations were observed in 76.8% of CRC tissue samples. APC mutations were not analyzed in the plasma samples. The co-existence of KRAS/PIK3CA/APC gene mutations encompassed the highest frequency among all combinations of mutations. BRAF and PIK3CA mutations were significantly more frequent in older patients. CONCLUSION: We demonstrated that a panel consisting of PIK3CA, KRAS, and BRAF mutations showed good diagnostic performance for detecting CRC in the plasma cfDNA.

Hypermethylated RASSF1 and SLC5A8 promoters alongside BRAFV600E mutation as biomarkers for papillary thyroid carcinoma.

Circulating cell-free DNA (cfDNA) has been considered as a diagnostic source to track genetic and epigenetic alterations in cancer. We aimed to study mutation in addition to the methylation status in the promoter regions of RASSF1 and SLC5A8 genes in tissues and circulating free DNA samples of patients affected with papillary thyroid carcinoma (PTC) and thyroid nodules as controls. BRAFV600E mutation was studied by ARMS-scorpion real-time polymerase chain reaction method in 57 PTC and 45 thyroid nodule cases. Methylation status of RASSF1 and SLC5A8 promoter regions was analyzed by methylation-specific high-resolution melting curve analysis. BRAFV600E mutation was found in 39 (68.4%) out of 57 PTC tissue samples, while in 33 (49.1%) cases of cfDNA, this mutation was detected. The frequency of BRAFV600E mutation in cfDNA was significantly different between metastatic and nonmetastatic PTC cases (22 of 33 PTC cases vs. 5 of 34 thyroid nodule samples). Methylation levels of three promoter regions of SLC5A8 and proximal promoter region of RASSF1 was significantly different between PTC and thyroid nodule cases in both cfDNA and tissue DNA. In addition, the methylation status of these two genes in tissue DNA was reflected in methylation status observed in cfDNA. This study confirmed that BRAFV600E mutation is better for discrimination between papillary thyroid carcinoma and thyroid nodules. On the other hand, hypermethylation in the more proximal promoter regions to RASSF1 and SLC5A8 genes showed higher sensitivity and more acceptable specificity for this discrimination.