title: Genomic profile of pseudomyxoma peritonei analyzed using next-generation sequencing and immunohistochemistry.
abstract: Pseudomyxoma peritonei (PMP) is a relatively rare clinical syndrome characterized by neoplastic epithelial cells growing in the peritoneal cavity and secreting mucinous ascites. Our aim was to explore the molecular events behind this fatal but under-investigated disease. We extracted DNA from 19 appendix-derived PMP tumors and nine corresponding normal tissues, and analyzed the mutational hotspot areas of 48 cancer-related genes by amplicon-based next-generation sequencing (NGS). Further, we analyzed the protein expression of V600E mutated BRAF, MLH1, MSH2, MSH6 and p53 from a larger set of PMP tumors (n = 74) using immunohistochemistry. With NGS, we detected activating somatic KRAS mutations in all of the tumors studied. GNAS was mutated in 63% of the tumors with no marked difference between low-grade and high-grade tumors. Only one (5.3%) tumor showed oncogenic PIK3CA mutation, one showed oncogenic AKT1 mutation, three (15.8%) showed SMAD4 mutations and none showed an APC mutation. P53 protein was aberrantly expressed in higher proportion of high-grade tumors as compared with low-grade ones (31.3 vs. 7.1%, respectively; p = 0.012) and aberrant expression was an independent factor for reduced overall survival (p = 0.002). BRAF V600E mutation was only found in one (1.4%) high-grade tumor by immunohistochemistry (n = 74). All the studied tumors expressed mismatch repair proteins MLH1, MSH2 and MSH6. Our results indicate that KRAS mutations are evident in all and GNAS mutations in most of the PMPs, but BRAF V600E, PIK3CA and APC mutations are rare. Aberrantly expressed p53 is associated with high-grade histology and reduced survival.
authors.affiliation: Genome-Scale Biology Research Program, Research Programs Unit, University of Helsinki, Helsinki, Finland.
authors.forename: Pirjo
authors.initials: P
authors.lastname: Nummela
authors.forename: Lilli
authors.initials: L
authors.lastname: Saarinen
authors.forename: Alexandra
authors.initials: A
authors.lastname: Thiel
authors.forename: Petrus
authors.initials: P
authors.lastname: Järvinen
authors.forename: Rainer
authors.initials: R
authors.lastname: Lehtonen
authors.forename: Anna
authors.initials: A
authors.lastname: Lepistö
authors.forename: Heikki
authors.initials: H
authors.lastname: Järvinen
authors.forename: Lauri A
authors.initials: LA
authors.lastname: Aaltonen
authors.forename: Sampsa
authors.initials: S
authors.lastname: Hautaniemi
authors.forename: Ari
authors.initials: A
authors.lastname: Ristimäki
mesh_terms: D000368:Aged; D014408:Biomarkers, Tumor / Q000235:genetics*; D004252:DNA Mutational Analysis; D005260:Female; D020869:Gene Expression Profiling; D023281:Genomics; D059014:High-Throughput Nucleotide Sequencing; D006801:Humans; D007124:Immunoenzyme Techniques; D008297:Male; D009154:Mutation / Q000235:genetics*; D060787:Neoplasm Grading; D010534:Peritoneal Neoplasms / Q000235:genetics* / Q000401:mortality / Q000473:pathology; D011379:Prognosis; D011553:Pseudomyxoma Peritonei / Q000235:genetics* / Q000401:mortality / Q000473:pathology; D015996:Survival Rate
chemical_list: D014408:Biomarkers, Tumor
keywords: BRAF; GNAS; KRAS; p53; pseudomyxoma peritonei