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 slinivky břišní 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 bez známek 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 slinivky břišní 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

The optimal choice of cancer therapy depends upon analysis of the tumor genome for druggable molecular alterations. The spatial and temporal intratumor heterogeneity of cancers creates substantial challenges, as molecular profile depends on time and site of tumor tissue collection. To capture the entire molecular profile, multiple biopsies from primary and metastatic sites at different time points would be required, which is not feasible for ethical or economic reasons. Molecular analysis of circulating cell-free DNA offers a novel, minimally invasive method that can be performed at multiple time-points and plausibly better represents the prevailing molecular profile of the cancer. Molecular analysis of this cell-free DNA offers multiple clinically useful applications, such as identification of molecular targets for cancer therapy, monitoring of tumor molecular profile in real time, detection of emerging molecular aberrations associated with resistance to particular therapy, determination of cancer prognosis and diagnosis of cancer recurrence or progression.

• Klíčová slova
• Liquid biopsy, advanced cancer, cell-free DNA, personalized medicine, targeted therapy,
• MeSH
• biopsie metody   MeSH
• chemorezistence MeSH
• cílená molekulární terapie MeSH
• diagnostické techniky molekulární MeSH
• DNA nádorová * MeSH
• genetická variace * MeSH
• genomika metody   MeSH
• individualizovaná medicína MeSH
• lidé MeSH
• management nemoci MeSH
• nádorové biomarkery * MeSH
• nádory diagnóza   genetika   mortalita   terapie   MeSH
• prognóza MeSH
• staging nádorů MeSH
• výsledek terapie MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Research Support, N.I.H., Extramural MeSH
• Názvy látek
• DNA nádorová * MeSH
• nádorové biomarkery * MeSH