More than 80% of patients with pancreatic cancer are diagnosed with either locally advanced or metastatic disease that is associated with a poor survival rate. Researchers at Duke University compared the secretomes of pancreatic cancer samples versus normal pancreatic cells with the aim of simultaneously identifying differentially secreted proteins and developing the reagents needed to detect them. They used an iterative selection process known as Systematic Evolution of Ligands by Exponential Enrichment (SELEX) to identify protein-binding RNA aptamer that can differentiate between the sera of pancreatic cancer and samples from healthy patients by binding to molecules selectively secreted by cancerous cells.
Partha Ray, Ph.D., post-doctoral fellow, presented data that led to the identification of several RNA aptamers that differentially bind the secretome of pancreatic cancer cells compared to normal pancreatic cells. One of these aptamers, M9-5, demonstrated specific binding in 20 of 22 patients with pancreatic cancer and 0 of 20 controls. He also showed that M9-5 binding decreases in samples from patients with reduced tumor burden and proposed the utility of this biomarker to monitor response to therapy.
The researchers identified the target for M9-5 as cyclophilin B, a secreted protein that had not previously been associated with pancreatic cancer. A cyclophilin B ELISA can detect quantifiable differences between sera from patients with or without pancreatic cancer.