An increasing number of studies have demonstrated that circular RNAs (circRNAs) can regulate gene expression through interacting with microRNAs. In this study, we analyzed the expression of antisense to CDR1as in colorectal cancer (CRC). CDR1as had a higher expression in CRC tissues compared to adjacent, normal mucosa and was positively associated with tumor size, T stage, lymph node metastasis, and poor overall survival (OS). Downregulation of CDR1as suppressed CRC cell proliferation and invasion and increased microRNA-7 (miR-7) expression. Intriguingly, ectopic expression of miR-7 in CRC cells consistently inhibited proliferation and invasion, and the miR-7 inhibitor was able to rescue the function of CDR1as knockdown. Mechanistic studies demonstrated that CDR1as silencing suppressed EGFR and IGF-1R expression, which could be partially blocked by the miR-7 inhibitor. Finally, positive correlations between CDR1as expression and EGFR and IGF-1R expression were observed in CRC samples. Thus, given the importance of CDR1as in blocking miR-7 and positively regulating EGFR and IGF-1R, dysregulated CDR1as expression may play an important role in CRC progression.

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Purpose: For stage II colon cancer, the efficacy of postoperative adjuvant chemotherapy remains controversial. It is well known that tumor-associated macrophages (TAMs) are important in tumor progression. In this study, TAMs were investigated as prognostic and predictive biomarkers for the efficacy of adjuvant chemotherapy for stage II colon cancer after radical resection. Experimental Design: This study enrolled two independent cohorts of consecutive patients from one medical center with pathologic stage II colon cancer after radical resections. Macrophages were detected using IHC staining of CD68 and CD206. Infiltration densities of CD68 þ TAMs, CD206 þ TAMs, and ratio of CD206 þ TAMs/CD68 þ TAMs (CD206/CD68 ratio) were calculated as prognostic and predictive biomarkers. Results: The primary and validation cohorts consisted of 521 and 314 patients, respectively. In both cohorts, high CD206/CD68 ratio was significantly associated with poor disease-free survival (DFS) and overall survival (OS). As an independent risk factor, CD206/CD68 ratio also had significantly better prognostic efficacy than CD68 þ TAM density, CD206 þ TAM density, and traditional clinicopathologic highrisk factors. Moreover, adjuvant chemotherapy significantly improved DFS and OS for patients with high CD206/CD68 ratio but not for those with low CD206/CD68 ratio. The interaction analyses were also significant for DFS. In subgroup analysis, CD206/CD68 ratio was still a significant predictor for adjuvant chemotherapy for patients in traditional high-risk group of recurrence (significant interaction for DFS). Conclusions: For stage II colon cancer, CD206/CD68 ratio is a better prognostic and predictive biomarker for postoperative adjuvant chemotherapy. Together with clinicopathologic high-risk factors, it will aid in precision treatment.