Combination of serum human satellite RNA and miR-21-5p levels as a biomarker for pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) has a poor prognosis due to the diffi-culty of its diagnosis. Because human satellite II (HSATII) RNA, a satellite repeat RNA, is highly and specifically expressed in human PDAC, the serum HSATII RNA level may be a biomarker of PDAC. To measure the serum HSATII RNA level with high sensitivity and reproducibility, we previously developed a convenient method, tandem repeat amplification by nuclease protection (TRAP) combined with droplet digital PCR (ddPCR). Here, we refined the original method by simul-taneously measuring the serum miR-21-5p level to enhance the detection of PDAC. The resulting PDAC-Index, constructed using serum HSATII RNA and miR-21-5p levels, discriminated patients with PDAC with high accuracy. We veri-fied the clinical usefulness of the PDAC-Index as a supportive test in difficult-to -diagnose cases. The PDAC-Index has satisfactory diagnostic performance and may routinely be applied for detecting PDAC.

Automated summary

Pancreatic ductal adenocarcinoma (PDAC) is difficult to diagnose and has a poor prognosis. Human satellite II (HSATII) RNA, highly expressed in human PDAC, may serve as a biomarker for PDAC. We developed a convenient method, tandem repeat amplification by nuclease protection (TRAP) combined with droplet digital PCR (ddPCR), to measure serum HSATII RNA level with high sensitivity and reproducibility. By simultaneously measuring serum miR-21-5p level, we refined the method and constructed a PDAC-Index that accurately discriminates PDAC patients. The PDAC-Index was clinically validated as a supportive test in challenging diagnostic cases and showed satisfactory diagnostic performance for routine PDAC detection.