BACKGROUND: Exosomes arise from viable cancer cells and may reflect a different biology than circulating cell-free DNA (cfDNA) shed from dying tissues. We compare exosome-derived DNA (exoDNA) to cfDNA in liquid biopsies of patients with pancreatic ductal adenocarcinoma (PDAC). PATIENTS AND METHODS: Patient samples were obtained between 2003 and 2010, with clinically annotated follow up to 2015. Droplet digital PCR was performed on exoDNA and cfDNA for sensitive detection of KRAS mutants at codons 12/13. A cumulative series of 263 individuals were studied, including a discovery cohort of 142 individuals: 68 PDAC patients of all stages; 20 PDAC patients initially staged with localized disease, with blood drawn after resection for curative intent; and 54 age-matched healthy controls. A validation cohort of 121 individuals (39 cancer patients and 82 healthy controls) was studied to validate KRAS detection rates in early-stage PDAC patients. Primary outcome was circulating KRAS status as detected by droplet digital PCR. Secondary outcomes were disease-free and overall survival. RESULTS: KRAS mutations in exoDNA, were identified in 7.4%, 66.7%, 80%, and 85% of age-matched controls, localized, locally advanced, and metastatic PDAC patients, respectively. Comparatively, mutant KRAS cfDNA was detected in 14.8%, 45.5%, 30.8%, and 57.9% of these individuals. Higher exoKRAS MAFs were associated with decreased disease-free survival in patients with localized disease. In the validation cohort, mutant KRAS exoDNA was detected in 43.6% of early-stage PDAC patients and 20% of healthy controls. CONCLUSIONS: Exosomes are a distinct source of tumor DNA that may be complementary to other liquid biopsy DNA sources. A higher percentage of patients with localized PDAC exhibited detectable KRAS mutations in exoDNA than previously reported for cfDNA. A substantial minority of healthy samples demonstrated mutant KRAS in circulation, dictating careful consideration and application of liquid biopsy findings, which may limit its utility as a broad cancer-screening method.

• Klíčová slova
• KRAS, circulating tumor DNA, exosome, liquid biopsy, pancreatic cancer,
• MeSH
• časná detekce nádoru metody   MeSH
• DNA nádorová krev   genetika   MeSH
• dospělí MeSH
• duktální karcinom pankreatu krev   genetika   patologie   MeSH
• exozómy genetika   MeSH
• Kaplanův-Meierův odhad MeSH
• kvantitativní polymerázová řetězová reakce MeSH
• lidé středního věku MeSH
• lidé MeSH
• mutace MeSH
• nádorové biomarkery krev   genetika   MeSH
• nádory slinivky břišní krev   genetika   patologie   MeSH
• přežití po terapii bez příznaků nemoci MeSH
• proporcionální rizikové modely MeSH
• protoonkogenní proteiny p21(ras) genetika   MeSH
• senioři MeSH
• Check Tag
• dospělí MeSH
• lidé středního věku MeSH
• lidé MeSH
• mužské pohlaví MeSH
• senioři MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• DNA nádorová MeSH
• KRAS protein, human MeSH Prohlížeč
• nádorové biomarkery MeSH
• protoonkogenní proteiny p21(ras) MeSH

The utility of KRAS mutations in plasma circulating cell-free DNA (cfDNA) samples as non-invasive biomarkers for the detection of pancreatic cancer has never been evaluated in a large case-control series. We applied a KRAS amplicon-based deep sequencing strategy combined with analytical pipeline specifically designed for the detection of low-abundance mutations to screen plasma samples of 437 pancreatic cancer cases, 141 chronic pancreatitis subjects, and 394 healthy controls. We detected mutations in 21.1% (N=92) of cases, of whom 82 (89.1%) carried at least one mutation at hotspot codons 12, 13 or 61, with mutant allelic fractions from 0.08% to 79%. Advanced stages were associated with an increased proportion of detection, with KRAS cfDNA mutations detected in 10.3%, 17,5% and 33.3% of cases with local, regional and systemic stages, respectively. We also detected KRAS cfDNA mutations in 3.7% (N=14) of healthy controls and in 4.3% (N=6) of subjects with chronic pancreatitis, but at significantly lower allelic fractions than in cases. Combining cfDNA KRAS mutations and CA19-9 plasma levels on a limited set of case-control samples did not improve the overall performance of the biomarkers as compared to CA19-9 alone. Whether the limited sensitivity and specificity observed in our series of KRAS mutations in plasma cfDNA as biomarkers for pancreatic cancer detection are attributable to methodological limitations or to the biology of cfDNA should be further assessed in large case-control series.

• Klíčová slova
• KRAS mutations, cell-free DNA, pancreatic cancer detection, plasma,
• MeSH
• antigen CA-19-9 krev   MeSH
• cirkulující nádorová DNA krev   genetika   MeSH
• duktální karcinom pankreatu krev   genetika   patologie   MeSH
• fenotyp MeSH
• frekvence genu MeSH
• genetická predispozice k nemoci MeSH
• lidé středního věku MeSH
• lidé MeSH
• mutace * MeSH
• mutační analýza DNA MeSH
• nádorové biomarkery krev   genetika   MeSH
• nádory slinivky břišní krev   genetika   patologie   MeSH
• pilotní projekty MeSH
• prediktivní hodnota testů MeSH
• protoonkogenní proteiny p21(ras) krev   genetika   MeSH
• reprodukovatelnost výsledků MeSH
• senioři MeSH
• staging nádorů MeSH
• studie případů a kontrol MeSH
• Check Tag
• lidé středního věku MeSH
• lidé MeSH
• mužské pohlaví MeSH
• senioři MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• multicentrická studie MeSH
• validační studie MeSH
• Geografické názvy
• Česká republika MeSH
• Slovenská republika MeSH
• Názvy látek
• antigen CA-19-9 MeSH
• cirkulující nádorová DNA MeSH
• KRAS protein, human MeSH Prohlížeč
• nádorové biomarkery MeSH
• protoonkogenní proteiny p21(ras) MeSH

AIM: To establish an optimum combination of molecular markers resulting in best overall diagnostic sensitivity and specificity for evaluation of suspicious pancreatic mass. METHODS: Endoscopic ultrasound (EUS)-guided fine needle aspiration cytology (FNA) was performed on 101 consecutive patients (63 males, 38 females, 60 +/- 12 years; 81 with subsequently diagnosed pancreatic cancer, 20 with chronic pancreatitis) with focal pancreatic mass. Samples were evaluated on-site by an experienced cytopathologist. DNA was extracted from Giemsa stained cells selected by laser microdissection and the presence of K-ras, p53 and p16 somatic mutations was tested by cycling-gradient capillary electrophoresis (CGCE) and single-strand conformation polymorphism (SSCP) techniques. In addition, allelic losses of tumor suppressor genes p16 (INK4, CDKN2A) and DPC4 (MADH4, SMAD4) were detected by monitoring the loss of heterozygosity (LOH) at 9p and 18q, respectively. RESULTS: Sensitivity and specificity of EUS-guided FNA were 75% and 85%, positive and negative predictive value reached 100%. The remaining 26% samples were assigned as inconclusive. Testing of molecular markers revealed sensitivity and specificity of 70% and 100% for K-ras mutations (P < 0.001), 24% and 90% for p53 mutations (NS), 13% and 100% for p16 mutations (NS), 85% and 64% for allelic losses at 9p (P < 0.001) and 78% and 57% for allelic losses at 18q (P < 0.05). When tests for different molecular markers were combined, the best results were obtained with K-ras + LOH at 9p (92% and 64%, P < 0.001), K-ras + LOH at 18q (92% and 57%, P < 0.001), and K-ras + LOH 9q + LOH 18q (96% and 43%, P < 0.001). When the molecular markers were used as complements to FNA cytology to evaluate inconclusive samples only, the overall sensitivity of cancer detection was 100% in all patients enrolled in the study. CONCLUSION: EUS-guided FNA cytology combined with screening of K-ras mutations and allelic losses of tumor suppressors p16 and DPC4 represents a very sensitive approach in screening for pancreatic malignancy. Molecular markers may find its use particularly in cases where FNA cytology has been inconclusive.

• MeSH
• chronická pankreatitida diagnóza   genetika   patologie   MeSH
• diagnostické techniky molekulární * MeSH
• dospělí MeSH
• elektroforéza kapilární MeSH
• endosonografie * MeSH
• inhibitor p16 cyklin-dependentní kinasy genetika   MeSH
• lidé středního věku MeSH
• lidé MeSH
• lidské chromozomy, pár 18 * MeSH
• lidské chromozomy, pár 9 * MeSH
• mutace MeSH
• nádorové biomarkery genetika   MeSH
• nádorový supresorový protein p53 genetika   MeSH
• nádory slinivky břišní diagnóza   genetika   patologie   MeSH
• polymorfismus konformace jednovláknové DNA MeSH
• prediktivní hodnota testů MeSH
• protein Smad4 genetika   MeSH
• protoonkogenní proteiny p21(ras) genetika   MeSH
• regulace genové exprese u nádorů MeSH
• senioři nad 80 let MeSH
• senioři MeSH
• senzitivita a specificita MeSH
• tenkojehlová biopsie metody   MeSH
• ztráta heterozygozity MeSH
• Check Tag
• dospělí MeSH
• lidé středního věku MeSH
• lidé MeSH
• mužské pohlaví MeSH
• senioři nad 80 let MeSH
• senioři MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• hodnotící studie MeSH
• Názvy látek
• inhibitor p16 cyklin-dependentní kinasy MeSH
• nádorové biomarkery MeSH
• nádorový supresorový protein p53 MeSH
• protein Smad4 MeSH
• protoonkogenní proteiny p21(ras) MeSH
• SMAD4 protein, human MeSH Prohlížeč
• TP53 protein, human MeSH Prohlížeč