title: [Molecular analysis of sporadic colon cancer].
abstract: BACKGROUND
  In Chile, colorectal cancer (CRC) is often diagnosed in late stages. Thus, surgical treatment must be complemented with chemotherapy. KRAS mutations and microsatellite instability have been detected in these tumors. However, the response to treatment in patients without KRAS mutations varies and requires a better understanding.
  
  
  OBJECTIVE
  To determine the frequency and distribution of somatic point mutations in KRAS, BRAF and PIK3CA genes and microsatellite instability status (MSI) in patients with colon cancer (CC).
  
  
  METHODS
  A prospective observational study of patients undergoing surgery for colon cancer. Tumor-derived DNA was analyzed by polymerase chain reaction (PCR) for the most frequent mutations of KRAS, BRAF and PIK3CA. PCR was also used to analyze MSI.
  
  
  RESULTS
  Fifty-eight patients with sporadic CC were analyzed, 16 showed KRAS mutations (G12R, G12D, G12V, G13D) and out of the 42 patients that did not show any mutation, 10 had mutations in BRAF (V600E) and PIK3CA (E542K, E545D, E545K, Q546E, H1047R). BRAF mutations alone or in combination with PIK3CA mutations were observed in 27% of high MSI tumors and in 2% of tumors without instability (p < 0.049). A higher percentage of high MSI tumors were located in the right colon (p < 0.001), and showed BRAF mutation (p < 0.020).
  
  
  CONCLUSIONS
  The highest percentage of high MSI and BRAF mutations was observed in the right colon. Therefore, this study suggests the presence of different molecular features between right and left colon tumors that should be considered when defining the therapeutic management.
authors.forename: Claudia
authors.initials: C
authors.lastname: Hurtado
authors.forename: Ana María
authors.initials: AM
authors.lastname: Wielandt
authors.forename: Alejandro J
authors.initials: AJ
authors.lastname: Zárate
authors.forename: Udo
authors.initials: U
authors.lastname: Kronberg
authors.forename: Magdalena
authors.initials: M
authors.lastname: Castro
authors.forename: Ken
authors.initials: K
authors.lastname: Yamagiwa
authors.forename: Takashi
authors.initials: T
authors.lastname: Ito
authors.forename: Yoshinobu
authors.initials: Y
authors.lastname: Eishi
authors.forename: Luis
authors.initials: L
authors.lastname: Contreras
authors.forename: Francisco
authors.initials: F
authors.lastname: López-Köstner
mesh_terms: D000230:Adenocarcinoma / Q000235:genetics* / Q000503:physiopathology; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D058534:Class I Phosphatidylinositol 3-Kinases; D003110:Colonic Neoplasms / Q000235:genetics* / Q000503:physiopathology; D004252:DNA Mutational Analysis; D005260:Female; D005784:Gene Amplification; D006801:Humans; D008297:Male; D053842:Microsatellite Instability; D008875:Middle Aged; D060885:Multiplex Polymerase Chain Reaction; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics*; D017354:Point Mutation / Q000235:genetics*; D011446:Prospective Studies; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics*; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics*
chemical_list: C117307:KRAS protein, human; D019869:Phosphatidylinositol 3-Kinases; D058534:Class I Phosphatidylinositol 3-Kinases; C484760:PIK3CA protein, human; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; D016283:Proto-Oncogene Proteins p21(ras)