title: Prognostic significance of alterations in KRAS isoforms KRAS-4A/4B and KRAS mutations in colorectal carcinoma.
abstract: Somatic KRAS mutation is an early well-known event in colorectal carcinogenesis but a complete understanding of RAS function and dysfunction in colorectal cancer is still to come. Our aim was to study the incidence of KRAS mutation; KRAS splice variants: KRAS4A and KRAS4B; and their relationships with various clinico-pathological characteristics in colorectal cancer (CRC).In this study, 285 CRC cases were analysed for KRAS mutation by direct DNA sequencing followed by immunohistochemical analysis after validation with real-time PCR assay, to study the protein expression of KRAS4A and -4B isoforms. KRAS gene mutations were seen in 80/285 CRCs (28.1%) and of the mutated cases, the majority of the mutations were seen in codon 12 (81.2%) as opposed to codon 13 (18.8%). CRCs with KRAS mutations were associated with a poor overall survival (p = 0.0009). Furthermore, KRAS mutations at codon 12 were associated with a poor overall survival of 64.4% at 5 years compared with a 5-year overall survival of 75.8% and 78.2% with codon 13 mutation and absence of KRAS mutations, respectively (p = 0.0025). KRAS4A protein expression was predominantly seen in the cytoplasm, while KRAS4B protein was nuclear. KRAS4A overexpression was significantly associated with left colon, histology subtype of adenocarcinoma, p27kip1, and cleaved caspase3 expression. Interestingly, KRAS4A overexpression was associated with a better overall survival (p = 0.0053). On the other hand, KRAS4B overexpression (33.2%) was significantly associated with larger tumour size (p = 0.0234) and inversely correlated with p27kip1 protein (p = 0.0159). Both KRAS mutation and KRAS4A were independent prognostic markers in a multivariate analysis with age, gender, stage, differentiation, and MSI status. Our results highlight the differential role of KRAS isoforms in CRC, their utility as a prognostic biomarker, and underline the importance of KRAS alterations as a potential therapeutic target for CRC.
authors.affiliation: Human Cancer Genomic Research, Research Center, King Faisal Specialist Hospital and Research Centre, Riyadh 11211, Saudi Arabia.
authors.forename: Jehad
authors.initials: J
authors.lastname: Abubaker
authors.forename: Prashant
authors.initials: P
authors.lastname: Bavi
authors.forename: Wael
authors.initials: W
authors.lastname: Al-Haqawi
authors.forename: Mehar
authors.initials: M
authors.lastname: Sultana
authors.forename: Sayer
authors.initials: S
authors.lastname: Al-Harbi
authors.forename: Nasser
authors.initials: N
authors.lastname: Al-Sanea
authors.forename: Alaa
authors.initials: A
authors.lastname: Abduljabbar
authors.forename: Luai H
authors.initials: LH
authors.lastname: Ashari
authors.forename: Samar
authors.initials: S
authors.lastname: Alhomoud
authors.forename: Fouad
authors.initials: F
authors.lastname: Al-Dayel
authors.forename: Shahab
authors.initials: S
authors.lastname: Uddin
authors.forename: Khawla S
authors.initials: KS
authors.lastname: Al-Kuraya
mesh_terms: D000230:Adenocarcinoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D002288:Adenocarcinoma, Mucinous / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D000236:Adenoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D000328:Adult; D001483:Base Sequence; D014408:Biomarkers, Tumor / Q000235:genetics* / Q000378:metabolism; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D004252:DNA Mutational Analysis / Q000379:methods; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism; D008297:Male; D053842:Microsatellite Instability; D008875:Middle Aged; D009154:Mutation; D009367:Neoplasm Staging; D016133:Polymerase Chain Reaction / Q000379:methods; D011379:Prognosis; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000378:metabolism; D016283:Proto-Oncogene Proteins p21(ras); D016019:Survival Analysis; D046888:Tissue Array Analysis / Q000379:methods; D018631:ras Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: D014408:Biomarkers, Tumor; C117307:KRAS protein, human; D020033:Protein Isoforms; D011518:Proto-Oncogene Proteins; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins