Detection of Circulating Tumor Cells in Resectable Pancreatic Ductal Adenocarcinoma: A Prospective Evaluation as a Prognostic Marker

Abstract

Circulating tumor cells (CTCs) are useful biomarkers of many solid tumors, but are infrequently detected in early stage pancreatic ductal adenocarcinomas (PDACs). The first drainage of pancreatic venous blood flow come to portal vein and pass through the liver, and they finally go out for peripheral blood. We thought that comparing CTCs from portal vein and peripheral blood could enable us to understand the clinical meaning of CTCs from each different site in PDACs. Therefore, we aimed to determine 1) whether CTCs could be reliably identified in early stages (operable) of PDACs, 2) if there are any differences in the detected number of CTC in portal vein blood and peripheral blood, and 3) whether CTCs can be sensitive biomarkers for the prognosis of resectable PDAC patients. Newly diagnosed PDAC patients who underwent operation with curative intention between 2013 and 2015 were prospectively enrolled. Blood draws from portal and peripheral vein ran through the microfabricated porous filter, and anti-epithelial cell adhesion molecule (EpCAM) and anti-Plectin-1 antibodies were used for CTC identification. Baseline clinical characteristics, tumor characteristics, treatment, and clinical outcomes were assessed. The clinical stages of the 32 enrolled patients were as follows: IA/IB 1 (3.1%); IIA 9 (28.1%); IIB 17 (53.1%); III 5 (15.6%). Twenty-seven patients (84.4%) received R0 resection, while five patients (15.6%) received R1 resection. EpCAM+ CTCs were detected in 20 portal blood (62.5%) and 22 peripheral blood (68.8%). Plectin-1+ CTCs were identified in 14 portal blood (43.8%) and 16 peripheral blood (50%). Plectin-1-expressing CTCs were picked from CTC platform (microfabricated porous filter) and we could find out all KRAS mutation. Patients with detectable EpCAM+ CTC less than one in peripheral blood showed longer overall survival (OS) compared to patients with detectable CTCs more than one (35.5 months vs. 16.0 months). EpCAM and Plectin-1 successfully identified CTCs at the early stage of PDACs. Also, the number of CTCs could be a prognostic marker for survival in resectable PDACs.

Plectin in Cancer: From Biomarker to Therapeutic Target

“…In lieu of traditional tumor tissue biopsy, which is invasive and only provides a static representation of the tumor, liquid biopsies are non-invasive and can present real-time insights throughout the course of disease [ 108 ]. Hence, Song et al evaluated plectin as a marker of circulating tumor cells (CTCs) from portal vein and peripheral blood samples of early-stage PDAC patients [ 109 ]. They were able to identify plectin-positive CTCs in 43.8% and 50% of portal blood and peripheral blood samples, respectively.…”

“…They were able to identify plectin-positive CTCs in 43.8% and 50% of portal blood and peripheral blood samples, respectively. Moreover, no plectin-positive CTCs were detected in samples from healthy volunteers [ 109 ]. However, the number of plectin-positive CTCs did not relate to disease staging, nor did it show a significant association with overall survival [ 109 ].…”

“…Moreover, no plectin-positive CTCs were detected in samples from healthy volunteers [ 109 ]. However, the number of plectin-positive CTCs did not relate to disease staging, nor did it show a significant association with overall survival [ 109 ]. Thus, expanded analysis of patients at varying PDAC stages could elucidate if and how plectin-positive CTCs change during PDAC carcinogenesis.…”

Clinical Significance of Circulating Tumor Cells in Unresectable Pancreatic Ductal Adenocarcinomas

“…We previously reported that healthy subjects had negligible CTC counts (mean, 0 CTCs/7.5 mL; median, 0 CTCs/7.5 mL; range, 0-5 CTCs/7.5mL of blood) when EpCAM and CK antibodies were used to detect CTCs (23, 24). Recently, we have also showed the specificity of Plectin-1 to capture CTCs in PDAC (22). In twenty-eight blood samples (3ml/each) from healthy donors, there was no single positive staining of Plectin-1 for CTCs in 17 samples (61%), and 11 healthy donors (39%) had 0.3∼0.7 CTCs per ml of blood (Mean±SD, 0.16±0.21 CTC/ml; Median 0.00 CTC/ml) ( Supplementary Figure 2 ).…”

“…Moreover, Plectin-1 distinguished PDAC from benign inflammatory diseases, like chronic pancreatitis (21). Recently, we have reported that captured PDAC CTCs were confirmed using Plectin-1 detection antibody as well as EpCAM antibody with KRAS mutation (22). Here, we examined whether Plectin-1 combined with EpCAM could improve CTC detection and the Plectin-1 positive PDAC CTCs can be used as prognostic biomarkers.…”