The oncogenic microRNAs miR-21and miR-31 negatively regulate tumor-suppressor genes. Toiyama and colleagues conducted a series of studies to assess their potential as serum biomarkers in colorectal cancer.
Screening in medium from two colorectal cancer cell lines and serum analysis in 12 patients with colorectal cancer and 12 controls showed that miR-21 was secreted from colorectal cancer cell lines and upregulated in serum of patients with colorectal cancer, but no significant difference was observed in serum miR-31 expression between patients with colorectal cancer and control subjects.
In a validation cohort consisting of 186 patients with colorectal cancer, another 60 patients with colorectal cancer who had undergone curative surgery, 43 patients with advanced adenoma, and 53 control subjects, serum miR-21 levels were significantly elevated in preoperative serum from patients with colorectal cancer and those with adenomas (both P < .001). Further, miR-21 expression was significantly decreased in postoperative serum from patients with colorectal cancer who had undergone curative surgery (P < .001). Serum miR-21 levels distinguished both adenoma patients (area under the curve [AUC] 0.81) and colorectal cancer patients (AUC 0.92) from control subjects.
Analysis of matched sera and primary colorectal cancer tumor tissue from 166 patients showed that high miR-21 expression in serum and tissue was significantly associated with tumor size, distant metastasis, and poor survival, with serum miR-21 level being an independent prognostic marker (hazard ratio = 4.12, P = .03). The investigators concluded, “Serum miR-21 is a promising biomarker for the early detection and prognosis of [colorectal cancer].” ■
Toiyama Y, et al: J Natl Cancer Inst. May 23, 2013 (early release online).