The role of microvesicles as biomarkers in the screening of colorectal neoplasm

Abstract

Background: Colorectal cancer (CRC) is the second cause of cancer death worldwide. The role of circulating microvesicles as a screening tool is a novel, yet effective approach that warrants prioritised research.

Methods: In a two-gate diagnostic accuracy study, 35 patients with benign colorectal polyps (BCRP) (n = 16) and colorectal cancer (CRC) (n = 19) were compared to 17 age-matched healthy controls. Total annexin-V positive microvesicles and sub-populations positive for selected biomarkers relevant to bowel neoplasm were evaluated in patients' plasma using flow cytometry. Statistical methods including factor analysis utilising two component factors were performed to obtain optimal diagnostic accuracy of microvesicles in identifying patients with colorectal neoplasms.

Results: Total plasma microvesicles, and sub-populations positive for CD31, CD42a, CD31+/CD42a-, EPHB2, ICAM and LGR5 (component factor-1) were able to identify patients with BCRP and CRC with a receiver operator curve (AUC) accuracy of a 100% (95% CI: 100%-100%) and 95% (95% CI: 88%-100%), respectively. To identify patients with BCRP, a cut-off point value of component factor-1761 microvesicles/μl demonstrated a 100% sensitivity, specificity and negative predictive value (NPV) and a 93% positive predictive value (PPV). To identify patients with CRC, a cut-off value of component factor-1 ³ 439 microvesicles/μl demonstrated a 100% sensitivity, specificity and NPV and a 65% PPV. CEA+ microvesicles sub-population were significantly (p < 0.02) higher in CRC in comparison to BCRP.

Conclusions: Microvesicles as biomarkers for the early and accurate detection of CRC is a simple and effective tool that yields a potential breakthrough in clinical management.

Keywords: benign colorectal polyps; bowel screening; colorectal cancer; microvesicles.