Jacob S. Ankeny

Circulating tumour cells as a biomarker for diagnosis and staging in pancreatic cancer

Background:Current diagnosis and staging of pancreatic ductal adenocarcinoma (PDAC) has important limitations and better biomarkers are needed to guide initial therapy. We investigated the performance of circulating tumour cells (CTCs) as an adjunctive biomarker at the time of disease presentation.Methods:Venous blood (VB) was collected prospectively from 100 consecutive, pre-treatment patients with PDAC. Utilising the microfluidic NanoVelcro CTC chip, samples were evaluated for the presence and number of CTCs. KRAS mutation analysis was used to compare the CTCs with primary tumour tissue. CTC enumeration data was then evaluated as a diagnostic and staging biomarker in the setting of PDAC.Results:We found 100% concordance for KRAS mutation subtype between primary tumour and CTCs in all five patients tested. Evaluation of CTCs as a diagnostic revealed the presence of CTCs in 54/72 patients with confirmed PDAC (sensitivity=75.0%, specificity=96.4%, area under the curve (AUROC)=0.867, 95% CI=0.798–0.935, and P<0.001). Furthermore, a cut-off of ⩾3 CTCs in 4 ml VB was able to discriminate between local/regional and metastatic disease (AUROC=0.885; 95% CI=0.800–0.969; and P<0.001).Conclusion:CTCs appear to function well as a biomarker for diagnosis and staging in PDAC.

Improving pancreatic cancer diagnosis using circulating tumor cells: prospects for staging and single-cell analysis

Pancreatic cancer (PC) is the fourth most common cause of cancer-related death in the USA, primarily due to late presentation coupled with an aggressive biology. The lack of adequate biomarkers for diagnosis and staging confound clinical decision-making and delay potentially effective therapies. Circulating tumor cells (CTCs) are a promising new biomarker in PC. Preliminary studies have demonstrated their potential clinical utility, and newer CTC isolation platforms have the potential to provide clinicians access to tumor tissue in a reliable, real-time manner. Such a ‘liquid biopsy’ has been demonstrated in several cancers, and small studies have demonstrated its potential applications in PC. This article reviews the available literature on CTCs as a biomarker in PC and presents the latest innovations in CTC research as well as their potential applications in PC.

Reality of Single Circulating Tumor Cell Sequencing for Molecular Diagnostics in Pancreatic Cancer

To understand the potential and limitations of circulating tumor cell (CTC) sequencing for molecular diagnostics, we investigated the feasibility of identifying the ubiquitous KRAS mutation in single CTCs from pancreatic cancer (PC) patients. We used the NanoVelcro/laser capture microdissection CTC platform, combined with whole genome amplification and KRAS Sanger sequencing. We assessed both KRAS codon-12 coverage and the degree that allele dropout during whole genome amplification affected the detection of KRAS mutations from single CTCs. We isolated 385 single cells, 163 from PC cell lines and 222 from the blood of 12 PC patients, and obtained KRAS sequence coverage in 218 of 385 single cells (56.6%). For PC cell lines with known KRAS mutations, single mutations were detected in 67% of homozygous cells but only 37.4% of heterozygous single cells, demonstrating that both coverage and allele dropout are important causes of mutation detection failure from single cells. We could detect KRAS mutations in CTCs from 11 of 12 patients (92%) and 33 of 119 single CTCs sequenced, resulting in a KRAS mutation detection rate of 27.7%. Importantly, KRAS mutations were never found in the 103 white blood cells sequenced. Sequencing of groups of cells containing between 1 and 100 cells determined that at least 10 CTCs are likely required to reliably assess KRAS mutation status from CTCs.

Metabolic exploitation of the sialic acid biosynthetic pathway to generate site-specifically labeled antibodies

Lack of a universal site-specific conjugation methodology for antibodies limits their potential to be developed as tumor-specific imaging agents or targeted therapeutics. A potential mechanism for site-specific conjugation involves utilization of the conserved N-glycosylation site in the CH2 domain. We sought to develop an antibody with an altered azido-sugar at this site whereby site-specific label could be added. The HB8059 hybridoma was cultured with peracetylated N-azidoacetlymannosamine (Ac4ManNAz). The resulting azido-sugar antibody was conjugated to phosphine-polyethylene glycol (PEG3)-biotin via a modified Staudinger reaction. Biochemical and functional characterization of the biotinylated antibody was performed. The azido-sugar antibody was also labeled with DyLight-650-Phosphine and injected into mice harboring pancreatic cancer xenografts. The tumors were dissected and imaged utilizing an IVIS fluorescent camera. The antibody was successfully produced in 100 μM Ac4ManNAz. The biotinylated antibody demonstrated a 50 kDa heavy and 25 kDa light chain on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, but demonstrated a single band at 50 kDa on western blot. Treatment with a N-linked glycosidase extinguished the band. Flow cytometry demonstrated antigen-specific binding of CA19-9-positive cells and the antibody localized to the antigen-positive tumor in vivo. We successfully produced an antibody with an azido-sugar at the conserved CH2 glycosylation site. We were able to utilize this azide to label the antibody with biotin or fluorescent label and demonstrate that the label is added in a site-specific manner to the heavy chain, N-linked glycosylation site. Finally, we demonstrated functionality of our antibody for in vitro and in vivo targeting of pancreatic cancer cells.

Circulating Tumor Cells in Gastrointestinal Cancer: Current Practices and Future Directions

GI cancers are the leading cause of cancer-related death worldwide primarily due to a combination of late presentation and aggressive biology. The lack of adequate biomarkers for screening, diagnosis, staging, and prognosis confounds clinical decision-making and delays potentially effective therapies. Circulating tumor cells (CTCs) are a new biomarker with particular promise in GI cancers, potentially offering clinicians and researchers real-time access to tumor tissue in a reliable, safe, and cost-effective manner. Preliminary studies have investigated the potential clinical utility of CTCs for all GI cancer types with promising results. Furthermore, advances in single cell analytics have been successfully applied to CTCs, allowing for exciting new clinical and research applications. In this chapter, we will review the current state of CTC research in GI cancers as well as the potential future applications that are currently being developed.

Abstract 3070: Capture, isolation, and mutational analysis of single pancreatic circulating tumor cells using NanoVelcro technology

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Introduction: Circulating tumor cells (CTCs) have been developed as a biomarker in several cancers, but not in pancreatic cancer (PDAC). The available clinical technology for CTC study, CellSearch, suffers from limited ability to perform molecular analysis. We sought to evaluate a novel microfluidic NanoVelcro technology coupled to laser micro-dissection (LMD), for CTC capture and single cell analysis of KRAS mutations to confirm tumor origin of captured CTCs. Methods: NanoVelcro utilizes a nano-spun polymer fiber, modified with streptavidin, to capture CTCs using biotinylated antibodies. The system was optimized with the CFPAC-1 (EpCAM+, KRAS G12 to V) cell line spiked into healthy donor blood. Patient samples were collected from 2 mL peripheral venous blood and run at the optimized flow rate of 1mL/hr. CTCs were defined by size (≥ 10 µm) and immuno-staining pattern (DAPI+/CK+/CD45-). Using LMD, single cells were isolated and subjected to whole genome amplification followed by PCR of KRAS exon 1 and subsequent Sanger Sequencing. Results: The NanoVelcro system allowed for detection of mutant KRAS in isolated CFPAC-1 cells. 6 CTCs were then isolated from a known KRAS G12 to V mutant patient and 3/6 (50.0%) captured CTCs were found to have KRAS G12 to V mutations while normal WBCs from the same patient contained wild-type KRAS. Conclusions: The microfluidic NanoVelcro technology demonstrated capture of pancreatic CTCs and may prove useful in the development of CTCs as a biomarker in PDAC. Application of LMD enabled single cell KRAS mutational analysis confirming cancer origin of isolated CTCs and supporting our current PDAC CTC identification criteria based on immuno-staining. This promising technology, combined with LMD, opens the door for molecular characterization of CTCs, thus providing insight into the biology of metastasis while potentially revealing molecular targets for therapeutics. Citation Format: Jacob S. Ankeny, Shuang Hou, Millicent Lin, Matthew Frias, Hank OuYang, Min Song, Matthew M. Rochefort, Mark D. Girgis, Hsian-Rong Tseng, James S. Tomlinson. Capture, isolation, and mutational analysis of single pancreatic circulating tumor cells using NanoVelcro technology. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3070. doi:10.1158/1538-7445.AM2014-3070