Tumor microRNA-29a expression and the risk of recurrence in stage II colon cancer.

Abstract

e14067 Background: To compare the microRNA (miRNA) profiles in the primary tumor of patients with recurrent and non-recurrent colon cancer. Methods: The study population included 110 patients, 51 (46%) with stage I and 59 (54%) with stage II disease, who underwent curative colectomies between 1995-2005 without adjuvant therapy and for whom reliable miR expression data was available. RNA was extracted from formalin-fixed paraffin-embedded tumor samples. Initial profiling, using microarrays, was done in order to identify potential biomarkers of recurrence. The miRNA expression was later verified by quantitative real-time polymerase chain reaction (qRT-PCR). Findings were compared between patients who had a recurrence within 36 months of surgery (bad prognosis group, n=23, 21%) and those who did not (good prognosis group, n=87, 79%) in the entire group and within each stage. Results: In stage I, none of the 903 miRNAs tested showed differential expression between patients with good prognosis compared with those with bad prognosis. In stage II, one miRNA, miR-29a, showed a clear differential expression between the groups (p=0.028). High expression of miR-29a was associated with a longer disease-free survival (DFS), on both univariate and multivariate analyses. Using miR-29a, the positive predictive value for non-recurrence was 94% (2 recurrences among 31 patients). The differential expression of miR-29a was verified by qRT-PCR, showing a similar impact of this miR on DFS. Conclusions: This study demonstrated a significant impact of miR-29a on the risk of recurrence in patients with stage II but not in patients with stage I colon cancer.