Spatial heterogeneity in epithelial to mesenchymal transition properties of circulating tumor cells associated with distant recurrence in pancreatic cancer patients

BACKGROUND: The spatial heterogeneity of epithelial to mesenchymal transition (EMT)-related circulating tumor cells (CTCs) within the circulatory system and its potential clinical relevance remain unclear in pancreatic cancer (PC) patients. We aimed to map the distribution of EMT-related CTCs along the spreading pathway and investigate the prognostic significance due to the potential spatial heterogeneity in the count and phenotypic properties of CTCs. METHODS: Both portal vein (PoV) and peripheral vein (PV) blood samples were collected from 39 PC patients. CTCs were isolated by using a CD45 negative enrichment method, and EMT-related phenotypes in CTCs were analyzed by 4-channel immunofluorescence. The correlations of CTCs with patient characteristics and recurrence-free survival (RFS) were analyzed. RESULTS: Both the number {median CTC total count, 10 [6–16] in PoV vs. 5 [1–7] in PV per mL, P<0.0001} and EMT status of CTCs [median mesenchymal CTC (M-CTC) percentage, 0.33 (0.13–0.52) in PoV vs. 0.2 (0–0.4) in PV, P=0.0211] showed significant spatial heterogeneity during dissemination from the PoV to the PV. Univariate analysis adjusting for patient age and sex revealed that CTC total count and M-CTC percentage in PoV samples could be risk factors for RFS in PC patients (P=0.003 and P=0.001, respectively), and ROC curve analysis found that both of these factors had good performance in distinguishing patients with early distant recurrence (within 6 months), with the optimal cut-off values of 14 cells/mL (AUROC =0.893, sensitivity =0.857, specificity =0.813, P=0.001) and 0.545 (AUROC =0.795, sensitivity =0.714, specificity =0.906, P=0.016), respectively. CONCLUSIONS: Multivascular assessment of EMT-related CTCs suggested profound dynamic alterations in total count and phenotypes during dissemination, and the spatial heterogeneity of CTCs in circulation could help establish novel prognosis markers in PC patients.