Development of a blood-based extracellular vesicle classifier for detection of early-stage pancreatic ductal adenocarcinoma.

BACKGROUND: Pancreatic ductal adenocarcinoma (PDAC) has an overall 5-year survival rate of just 12.5% and thus is among the leading causes of cancer deaths. When detected at early stages, PDAC survival rates improve substantially. Testing high-risk patients can increase early-stage cancer detection; however, currently available liquid biopsy approaches lack high sensitivity and may not be easily accessible. METHODS: Extracellular vesicles (EVs) were isolated from blood plasma that was collected from a training set of 650 patients (105 PDAC stages I and II, 545 controls). EV proteins were analyzed using a machine learning approach to determine which were the most informative to develop a classifier for early-stage PDAC. The classifier was tested on a validation cohort of 113 patients (30 PDAC stages I and II, 83 controls). RESULTS: The training set demonstrates an AUC of 0.971 (95% CI = 0.953-0.986) with 93.3% sensitivity (95% CI: 86.9-96.7) at 91.0% specificity (95% CI: 88.3-93.1). The trained classifier is validated using an independent cohort (30 stage I and II cases, 83 controls) and achieves a sensitivity of 90.0% and a specificity of 92.8%. CONCLUSIONS: Liquid biopsy using EVs may provide unique or complementary information that improves early PDAC and other cancer detection. EV protein determinations herein demonstrate that the AC Electrokinetics (ACE) method of EV enrichment provides early-stage detection of cancer distinct from normal or pancreatitis controls.

Pancreatic cancer is one of the deadliest cancers and it is often detected when it is too late, limiting treatment options and reducing survival rates. Identifying blood-based markers of pancreatic cancer may help us to diagnose it earlier, when it is more treatable. Tiny particles circulating in the blood stream, called extracellular vesicles (EVs), contain useful information about tumors, which can be collected with our innovative technology. In this study, we analyzed markers present within EVs and developed a computational tool using this information to identify people with early-stage pancreatic cancer. With further testing in real-world settings, this approach may prove useful for surveillance and early detection of this deadly disease.

Case Report: Early detection of pancreatic pre-cancer lesion in multimodal approach with exosome liquid biopsy.

Background: The detection of pancreatic ductal adenocarcinoma (PDAC) lesions at pre-cancerous or early-stages is critical to improving patient survival. We have developed a liquid biopsy test (ExoVita®) based on the measurement of protein biomarkers in cancer-derived exosomes. The high sensitivity and specificity of the test for early-stage PDAC has the potential to improve a patient's diagnostic journey in hopes to impact patient outcomes. Methods: Exosome isolation was performed using alternating current electric (ACE) field applied to the patient plasma sample. Following a wash to eliminate unbound particles, the exosomes were eluted from the cartridge. A downstream multiplex immunoassay was performed to measure proteins of interest on the exosomes, and a proprietary algorithm provided a score for probability of PDAC. Results: We describe the case of a 60-year-old healthy non-Hispanic white male with acute pancreatitis who underwent numerous invasive diagnostic procedures that failed to detect radiographic evidence of pancreatic lesions. Following the results of our exosome-based liquid biopsy test showing "High Likelihood of PDAC", in addition to KRAS and TP53 mutations, the patient decided to undergo a robotic pancreaticoduodenectomy (Whipple) procedure. Surgical pathology confirmed the diagnosis of high-grade intraductal papillary mucinous neoplasm (IPMN), which was consistent with the results of our ExoVita® test. The patient's post-operative course was unremarkable. At five-month follow-up, the patient continued to recover well without complications, in addition to a repeat ExoVita test which demonstrated "Low Likelihood of PDAC". Conclusion: This case report highlights how a novel liquid biopsy diagnostic test based on the detection of exosome protein biomarkers allowed early diagnosis of a high-grade precancerous lesion for PDAC and improved patient outcome.

Early-stage multi-cancer detection using an extracellular vesicle protein-based blood test.

Background: Detecting cancer at early stages significantly increases patient survival rates. Because lethal solid tumors often produce few symptoms before progressing to advanced, metastatic disease, diagnosis frequently occurs when surgical resection is no longer curative. One promising approach to detect early-stage, curable cancers uses biomarkers present in circulating extracellular vesicles (EVs). To explore the feasibility of this approach, we developed an EV-based blood biomarker classifier from EV protein profiles to detect stages I and II pancreatic, ovarian, and bladder cancer. Methods: Utilizing an alternating current electrokinetics (ACE) platform to purify EVs from plasma, we use multi-marker EV-protein measurements to develop a machine learning algorithm that can discriminate cancer cases from controls. The ACE isolation method requires small sample volumes, and the streamlined process permits integration into high-throughput workflows. Results: In this case-control pilot study, comparison of 139 pathologically confirmed stage I and II cancer cases representing pancreatic, ovarian, or bladder patients against 184 control subjects yields an area under the curve (AUC) of 0.95 (95% CI: 0.92 to 0.97), with sensitivity of 71.2% (95% CI: 63.2 to 78.1) at 99.5% (97.0 to 99.9) specificity. Sensitivity is similar at both early stages [stage I: 70.5% (60.2 to 79.0) and stage II: 72.5% (59.1 to 82.9)]. Detection of stage I cancer reaches 95.5% in pancreatic, 74.4% in ovarian (73.1% in Stage IA) and 43.8% in bladder cancer. Conclusions: This work demonstrates that an EV-based, multi-cancer test has potential clinical value for early cancer detection and warrants future expanded studies involving prospective cohorts with multi-year follow-up.

Simultaneous Isolation of Circulating Nucleic Acids and EV-Associated Protein Biomarkers From Unprocessed Plasma Using an AC Electrokinetics-Based Platform.

The power of personalized medicine is based on a deep understanding of cellular and molecular processes underlying disease pathogenesis. Accurately characterizing and analyzing connections between these processes is dependent on our ability to access multiple classes of biomarkers (DNA, RNA, and proteins)-ideally, in a minimally processed state. Here, we characterize a biomarker isolation platform that enables simultaneous isolation and on-chip detection of cell-free DNA (cfDNA), extracellular vesicle RNA (EV-RNA), and EV-associated proteins in unprocessed biological fluids using AC Electrokinetics (ACE). Human biofluid samples were flowed over the ACE microelectrode array (ACE chip) on the Verita platform while an electrical signal was applied, inducing a field that reversibly captured biomarkers onto the microelectrode array. Isolated cfDNA, EV-RNA, and EV-associated proteins were visualized directly on the chip using DNA and RNA specific dyes or antigen-specific, directly conjugated antibodies (CD63, TSG101, PD-L1, GPC-1), respectively. Isolated material was also eluted off the chip and analyzed downstream by multiple methods, including PCR, RT-PCR, next-generation sequencing (NGS), capillary electrophoresis, and nanoparticle size characterization. The detection workflow confirmed the capture of cfDNA, EV-RNA, and EV-associated proteins from human biofluids on the ACE chip. Tumor specific variants and the mRNAs of housekeeping gene PGK1 were detected in cfDNA and RNA isolated directly from chips in PCR, NGS, and RT-PCR assays, demonstrating that high-quality material can be isolated from donor samples using the isolation workflow. Detection of the luminal membrane protein TSG101 with antibodies depended on membrane permeabilization, consistent with the presence of vesicles on the chip. Protein, morphological, and size characterization revealed that these vesicles had the characteristics of EVs. The results demonstrated that unprocessed cfDNA, EV-RNA, and EV-associated proteins can be isolated and simultaneously fluorescently analyzed on the ACE chip. The compatibility with established downstream technologies may also allow the use of the platform as a sample preparation method for workflows that could benefit from access to unprocessed exosomal, genomic, and proteomic biomarkers.

The p40/ARPC1 subunit of Arp2/3 complex performs multiple essential roles in WASp-regulated actin nucleation.

The Arp2/3 complex is a conserved seven-subunit actin-nucleating machine activated by WASp (Wiskott Aldrich syndrome protein). Despite its central importance in a broad range of cellular processes, many critical aspects of the mechanism of the Arp2/3 complex have yet to be resolved. In particular, some of the individual subunits in the complex have not been assigned clear functional roles, including p40/ARPC1. Here, we dissected the structure and function of Saccharomyces cerevisiae p40/ARPC1, which is encoded by the essential ARC40 gene, by analyzing 39 integrated alleles that target its conserved surfaces. We identified three distinct sites on p40/ARPC1 required for function in vivo: one site contacts p19/ARPC4, one contacts p15/ARPC5, and one site resides in an extended structural "arm" of p40/ARPC1. Using a novel strategy, we purified the corresponding lethal mutant Arp2/3 complexes from yeast and compared their actin nucleation activities. Lethal mutations at the contact with p19/ARPC4 specifically impaired WASp-induced nucleation. In contrast, lethal mutations at the contact with p15/ARPC5 led to unregulated ("leaky") nucleation in the absence of WASp. Lethal mutations in the extended arm drastically reduced nucleation, and the same mutations disrupted the ability of the purified p40/ARPC1 arm domain to bind the VCA domain of WASp. Together, these data indicate that p40/ARPC1 performs at least three distinct, essential functions in regulating Arp2/3 complex-mediated actin assembly: 1) suppression of spontaneous nucleation by the Arp2/3 complex, which requires proper contacts with p15/ARPC5; 2) propagation of WASp activation signals via contacts with p19/ARPC2; and 3) direct facilitation of actin nucleation through interactions of the extended arm with the VCA domain of WASp.

Twinfilin is an actin-filament-severing protein and promotes rapid turnover of actin structures in vivo.

Working in concert, multiple actin-binding proteins regulate the dynamic turnover of actin networks. Here, we define a novel function for the conserved actin-binding protein twinfilin, which until now was thought to function primarily as a monomer-sequestering protein. We show that purified budding yeast twinfilin (Twf1) binds to and severs actin filaments in vitro at pH below 6.0 in bulk kinetic and fluorescence microscopy assays. Further, we use total internal reflection fluorescence (TIRF) microscopy to demonstrate that Twf1 severs individual actin filaments in real time. It has been shown that capping protein directly binds to Twf1 and is required for Twf1 localization to cortical actin patches in vivo. We demonstrate that capping protein directly inhibits the severing activity of Twf1, the first biochemical function ascribed to this interaction. In addition, phosphatidylinositol (4,5)-bisphosphate [PtdIns(4,5)P2] inhibits Twf1 filament-severing activity. Consistent with these biochemical activities, a twf1Delta mutation causes reduced rates of cortical actin patch turnover in living cells. Together, our data suggest that twinfilin coordinates filament severing and monomer sequestering at sites of rapid actin turnover and is controlled by multiple regulatory inputs.

Coordinated regulation of actin filament turnover by a high-molecular-weight Srv2/CAP complex, cofilin, profilin, and Aip1.

BACKGROUND: Dynamic remodeling of the actin cytoskeleton requires rapid turnover of actin filaments, which is regulated in part by the actin filament severing/depolymerization factor cofilin/ADF. Two factors that cooperate with cofilin are Srv2/CAP and Aip1. Human CAP enhances cofilin-mediated actin turnover in vitro, but its biophysical properties have not been defined, and there has been no in vivo evidence reported for its role in turnover. Xenopus Aip1 forms a cofilin-dependent cap at filament barbed ends. It has been unclear how these diverse activities are coordinated in vivo. RESULTS: Purified native yeast Srv2/CAP forms a high molecular weight structure comprised solely of actin and Srv2. The complex is linked to actin filaments via the SH3 domain of Abp1. Srv2 complex catalytically accelerates cofilin-dependent actin turnover by releasing cofilin from ADP-actin monomers and enhances the ability of profilin to stimulate nucleotide exchange on ADP-actin. Yeast Aip1 forms a cofilin-dependent filament barbed end cap, disrupted by the cof1-19 mutant. Genetic analyses show that specific combinations of activities mediated by cofilin, Srv2, Aip1, and capping protein are required in vivo. CONCLUSIONS: We define two genetically and biochemically separable functions for cofilin in actin turnover. One is formation of an Aip1-cofilin cap at filament barbed ends. The other is cofilin-mediated severing/depolymerization of filaments, accelerated indirectly by Srv2 complex. We show that the Srv2 complex is a large multimeric structure and functions as an intermediate in actin monomer processing, converting cofilin bound ADP-actin monomers to profilin bound ATP-actin monomers and recycling cofilin for new rounds of filament depolymerization.

Effects of blocking buffers and plasma proteins on the protein C biosensor performance.

Protein C (PC) deficiency can lead to abnormal thrombus formation in blood vessels, obstructing oxygen and nutrient transport to various organs or tissues. Quantifying PC amount in blood plasma usually takes long time, is difficult and expensive due to its low concentration and other homologous proteins in it. A fiber-optic immunosensor has been under development for several years for the PC real-time assay. In this study, blocking buffers have been examined to reduce the noise caused by non-specific adsorption. Ethanolamine was found to reduce the noise significantly. The effect of various PC homologues (factors II, VII, IX, and X) on the biosensor performance was investigated. The sensor showed little cross reactivity with these homologues. Human serum albumin (HSA) in the sample decreased the signal intensity. However, PC could be still quantified in samples with HSA at the physiological level.

Direct regulation of Arp2/3 complex activity and function by the actin binding protein coronin.

Mechanisms for activating the actin-related protein 2/3 (Arp2/3) complex have been the focus of many recent studies. Here, we identify a novel mode of Arp2/3 complex regulation mediated by the highly conserved actin binding protein coronin. Yeast coronin (Crn1) physically associates with the Arp2/3 complex and inhibits WA- and Abp1-activated actin nucleation in vitro. The inhibition occurs specifically in the absence of preformed actin filaments, suggesting that Crn1 may restrict Arp2/3 complex activity to the sides of filaments. The inhibitory activity of Crn1 resides in its coiled coil domain. Localization of Crn1 to actin patches in vivo and association of Crn1 with the Arp2/3 complex also require its coiled coil domain. Genetic studies provide in vivo evidence for these interactions and activities. Overexpression of CRN1 causes growth arrest and redistribution of Arp2 and Crn1p into aberrant actin loops. These defects are suppressed by deletion of the Crn1 coiled coil domain and by arc35-26, an allele of the p35 subunit of the Arp2/3 complex. Further in vivo evidence that coronin regulates the Arp2/3 complex comes from the observation that crn1 and arp2 mutants display an allele-specific synthetic interaction. This work identifies a new form of regulation of the Arp2/3 complex and an important cellular function for coronin.

Sensing performance of protein C immuno-biosensor for biological samples and sensor minimization.

Protein C (PC) is an important anticoagulant and antithrombotic agent in human blood plasma. PC deficiency can result in clotting complications that interfere with oxygen and nutrient transport. A fiber-optic biosensor is being developed to provide real time diagnosis of PC deficiency. The PC sensor was tested to quantify PC level in human plasma. The signal intensity obtained from the plasma sample was 30% of the buffered sample, possibly due to the increased viscosity. The feasibility of monitoring PC level in animal cell culture broth and animal milk was tested. For the cell culture broth, 80% of signal was observed. However, the decrease was consistent over the sensing range. For whole and 1:100 diluted bovine milk, the signals were 60 and 78% of buffered sample, respectively. The biosensor length was reduced from 12.5 to 6 cm with sufficient sensitivity. To increase the sensor reusability, various elution buffers were applied after each sensing. Triethylamine elution buffer provided the best sensor regeneration capability and increased the number of assays from 2.5 to 7 times for 6 cm fibers.

Assay procedure optimization of a rapid, reusable protein C immunosensor for physiological samples.

A fiber-optic immunosensor for quantifying the protein C (PC) amount in a plasma sample is being developed to provide accurate, fast, cost-effective diagnosis of heterozygous PC deficiency (0.5-2.5 microg ml(-1)). As a progress report on the sensor development, this paper focuses on optimizations of vanous assay steps. These include: (1) the primary antibody concentration; (2) the effect of the primary antibody leaching on the sensitivity; (3) the fluorophore to secondary antibody ratio; and (4) the sample and secondary antibody incubation times. The optimal primary antibody concentration for the PC sensor was determined to be 65 microg ml(-1); its leaching was minor, stabilized within 3 days, and the sensor sensitivity change after 30 days of storage was minor; sample and secondary antibody incubation times were reduced from 10 to 5 and from 5 to 3 min, respectively, while maintaining a reasonable signal-to-noise level. The immunosensor was also tested with (5) human serum albumin and human plasma and (6) with and without convective flow. High viscosity of human plasma decreased signal intensity, but clear signal discrimination was possible in the concentration range of interest. (7) Application of convective flow increased the signal intensity by increasing PC mass transport rate to the sensor surface. The optimized PC immunosensor provides a smaller (100 microl sample chamber) and faster (10-15 min) tool for PC detection in human plasma.