Magnetic resonance molecular imaging of extradomain B fibronectin enables detection of pancreatic ductal adenocarcinoma metastasis

Abstract

Extradomain-B Fibronectin (EDB-FN) is an oncomarker that can be visualized with magnetic resonance molecular imaging (MRMI) to detect pancreatic ductal adenocarcinoma (PDAC) metastasis. In this study, we sought to assess the expression of EDB-FN in clinical samples of PDAC and to evaluate MRMI of PDAC metastasis with an EDB-FN-specific gadolinium-based contrast agent (MT218) in an orthotopic KPC-GFP-Luc mouse model. EDB-FN expression was evaluated in PDAC tissue samples through immunohistochemistry. RNA-Seq data obtained from the GEPIA2 project was evaluated to demonstrate EDB-FN expression in large patient cohorts. FLASH-3D MRI at 3 T of the KPC-GFP-Luc metastasis model was performed following injection of MT218. Tumor enhancement in MR images was correlated to postmortem distribution of KPC-GFP-Luc tumors using fluorescent and bright-field cryo-imaging and anatomical landmarks. EDB-FN immunohistochemical staining scores of human metastatic tumor stroma, (2.17 ± 0.271), metastatic tumor parenchyma (2.08 ± 0.229), primary tumor stroma (1.61 ± 0.26), and primary tumor parenchyma (1.61 ± 0.12) were significantly (p < 0.0001) higher than normal pancreas stroma (0.14 ± 0.10) and normal pancreas parenchyma (0.14 ± 0.14). EDB-FN mRNA expression in tumors is 4.98 log₂(TPM + 1) and 0.18 log₂(TPM + 1) in normal tissue (p < 0.01). A mouse model of EDB-FN rich PDAC metastasis exhibited T₁-weighted contrast to noise (CNR) changes of 21.80 ± 4.34 in perimetastatic regions and 8.38 ± 0.79 in metastatic regions identified through cryo-imaging, significantly higher (p < 0.05) than CNR changes found in normal liver (-6.43 ± 0.92), mesentery (2.24 ± 0.92), spleen (-3.06 ± 2.38) and intestine (1.08 ± 2.15). We conclude that EDB-FN is overexpressed in metastatic and primary PDAC tumors and MRMI with MT218 enables the detection of metastatic and perimetastatic tissues.

Keywords: Extracellular matrix; Extradomain B fibronectin; Magnetic resonance molecular imaging; Metastasis; Pancreatic cancer; Targeted MRI contrast agent.