MicroRNA Expression Signatures Associated With BRAF-Mutated Versus KRAS-Mutated Colorectal Cancers

Medicine (Baltimore). 2016 Apr;95(15):e3321. doi: 10.1097/MD.0000000000003321.

Abstract

BRAF and KRAS genes are known to play a similar role in the activation of RAS-RAF-MEK-ERK signaling pathway in colorectal tumorigenesis. However, BRAF-mutated colorectal cancers (CRCs) have distinct clinicopathologic characteristics different from those of the KRAS mutated ones as in comparison the BRAF-mutated CRCs are associated with a much worse prognosis for the afflicted patients. This study aimed to determine the different miRNA expression signatures associated with BRAF-mutated CRCs in comparison to KRAS-mutated ones, and to identify the specific miRNAs possibly mediating the aggressive phenotype of the BRAF-mutated CRCs. We screened 535 formalin-fixed paraffin-embedded CRC tissue samples for the BRAF V600E mutation, and selected 7 BRAF-mutated and 7 KRAS-mutated CRCs that were tumor size, stage, and microsatellite status-matched. Affymetrix GeneChip® miRNA 4.0 Array was used for detection of miRNA expression differences in the selected samples. We validated the array results by quantitative reverse transcription polymerase chain reaction (qRT-PCR) for selected miRNAs. A total of 10 differentially expressed (DE) miRNAs associated with BRAF-mutated CRCs were obtained, including miR-31-5p, miR-877-5p, miR-362-5p, and miR-425-3p. miR-31-5p showed the highest fold change (8.3-fold) among all of the miRNAs analyzed. From the analyses of GO biological processes, the DE-miRNAs were functionally relevant to cellular proliferation such as positive regulation of gene expression (P = 1.26 × 10(-10)), transcription (P = 9.70 × 10(-10)), and RNA metabolic process (P = 1.97 × 10(-9)). Bioinformatics analysis showed that the DE-miRNAs were significantly enriched in cancer-associated pathways including neutrophin signaling (P = 6.84 × 10(-5)), pathways in cancer (P = 0.0016), Wnt signaling (P = 0.0027), and MAPK signaling pathway (P = 0.0036). Our results suggest that the DE-miRNAs in BRAF-mutated CRCs in comparison to KRAS-mutated CRCs are implicated in the aggressive phenotype of the BRAF-mutated CRCs. Further experimental validation is required to confirm these results.

Publication types

  • Comparative Study
  • Observational Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Carcinogenesis / genetics
  • Cell Proliferation / genetics
  • Colorectal Neoplasms* / genetics
  • Colorectal Neoplasms* / pathology
  • Female
  • Gene Expression Profiling / methods
  • Gene Expression Regulation, Neoplastic
  • Humans
  • Male
  • MicroRNAs / genetics*
  • Middle Aged
  • Mutation
  • Neoplasm Staging
  • Prognosis
  • Proto-Oncogene Proteins B-raf / genetics*
  • Proto-Oncogene Proteins p21(ras) / genetics*
  • Signal Transduction
  • Tumor Burden

Substances

  • KRAS protein, human
  • MicroRNAs
  • BRAF protein, human
  • Proto-Oncogene Proteins B-raf
  • Proto-Oncogene Proteins p21(ras)