KRAS and BRAF mutations and MSI status in precursor lesions of colorectal cancer detected by colonoscopy

Abstract

Abstract. Colorectal cancer (CRC) is one of the most frequent cancers worldwide. Adenoma is the main precursor lesion and, recently, the serrated polyps were described as a group of colorectal lesions with malignant potential. The morphologic and biologic characterizations of serrated polyps remain limited. The aim of the present study was to determine the frequency of KRAS and BRAF mutations and microsatellite instability (MSI) in CRC precursor lesions, to evaluate the association between molecular, pathologic and morphologic alterations in precursor lesions and to compare with the alterations detected in CRC. A series of 342 precursor lesions were removed from 155 patients during colonoscopy. After morphologic classification, molecular analysis was performed in 103 precursor lesions, and their genetic profile compared with 47 sporadic CRCs. Adenomas were the main precursor lesions (70.2%). Among the serrated polyps, the main precursor lesion was hyperplastic polyps (HPs) (82.4%), followed by sessile serrated adenomas (12.7%) and traditional serrated adenomas (2.0%). KRAS mutations were detected in 13.6% of the precursor lesions, namely in adenomas and in HPs, but in no serrated adenoma. BRAF mutations were found in 9 (8.7%) precursor lesions, mainly associated with serrated polyps and absent in adenomas (P<0.001). High MSI (MSI-H) was absent in precursor lesions. In the 47 CCR cases, 46.8% exhibited KRAS mutation, 6.5% BRAF mutations and 10.6% MSI-H. This study confirms the role of KRAS and BRAF mutations in CRC carcinogenesis, a crucial step in implementing CRC screening strategies.

The metabolic microenvironment of melanomas: Prognostic value of MCT1 and MCT4

“…46 Briefly, serially 10 mm thick unstained sections of paraffin blocks were sectioned and one H&E section was first evaluated by a pathologist to confirm the diagnosis and used for identification and selection of the areas of interest, which were macrodissected into a microfuge tube using a sterile needle (BD PrecisionGlide, BD, #305165). The macrodissected tissue was deparaffinized by a serial wash with xylol and ethanol (100%-70%-50%).…”

Absence of microsatellite instability andBRAF(V600E) mutation in testicular germ cell tumors

“…DNA was obtained from FFPE tissue sections representative of tumor pathology as previously described (Martinho et al, 2009a, b;Yamane et al, 2014), with minor modifications. Briefly, 10 lm thick unstained sections of paraffin blocks were sectioned and one H&E section was used for identification and selection of the tumor area, which was then macrodissected into a microfuge tube using a sterile needle (Neolus, 25G -0.5 mm).…”

“…The BRAF primers used were: 5 0 -TCA-TAATGCTTGCTCTGATAGGA-3 0 (sense) and 5 0 -GGCCAAAAATT-TAATCAGTGGA-3 0 (antisense) (Basto et al, 2005;Martinho et al, 2009a,b;Yamane et al, 2014). The PCR was performed with a Veriti thermocycler (Applied Biosystems) and products were evaluated by electrophoresis in 1% agarose gel.…”

“…Hotspot regions (exon 15) of the oncogene BRAF (codon 600) were analyzed by polymerase chain reaction (PCR), followed by direct sequencing, as previously described by our group (Basto et al, 2005;Martinho et al, 2009a,b;Yamane et al, 2014).…”

“…Microsatellite instability evaluation was performed using multiplex PCR for five quasimonomorphic mononucleotide repeat markers (NR-27, NR-21, NR-24, BAT-25, and BAT-26) as previously described (Viana-Pereira et al, 2011;Campanella et al, 2014;Yamane et al, 2014). Briefly, each antisense primer was end-labeled with a fluorescent dye: FAM (6-carboxyfluorescein) for BAT-26 and NR-21, VIC (2 0 -chloro-7 0 -phenyl-1,4-dichloro-6-carboxyfluorescein) for and NED (2,7,4, for NR-24.…”