MicroRNA Expression Levels and Histopathological Features of Colorectal Cancer. 
Non-coding RNAs have opened a new window in cancer biology.  MicroRNAs (miRNAs), as a family of non-coding RNAs, play an important role in the gene regulation.  The aberrant expression of these small molecules has been documented to involve in colorectal cancer (CRC) pathogenesis.  This study aimed to examine the expression of miRNAs in CRC and to correlate their expression levels with histological markers (Ki-67 and CD34).  Tumor tissues and matched normal adjacent tissues were collected from 36 patients with newly diagnosed CRC.  Immunohistochemical (IHC) staining of tumor tissues was performed for Ki-67 (proliferation) and CD34 (angiogenesis) markers, and the immunoexpression staining scores were obtained.  A polyadenylation SYBER Green quantitative real-time PCR technique was used to quantify the expression of a panel of five CRC-related miRNAs (hsa-miR-21, 31, 20a, 133b, and 145).  Histopathological (H) scores and miRNA expression levels were correlated with clinicopathological features including the degree of differentiation, staging, and lymphovascular invasion.  Our results showed the significant difference between the two groups for the expression level of hsa-miR-21, hsa-miR-31, hsa-miR-145, and miR-20a (P < 0.001), but not for hsa-miR-133b (P = 0.57).  Further analysis revealed an inverse significant correlation between hsa-miR-145 and Ki-67 (r = - 0.942, P < 0.001).  While a positive correlation was observed between hsa-miR-21 and Ki-67 (r = 0.920, P < 0.001), and hsa-miR-21 and CD34 (r = 0.981, P < 0.001).  Also, a positive correlation between hsa-miR-31 and Ki-67 (r = 0.913, P < 0.001), hsa-miR-31 and CD34 (r = 0.798, P < 0.05), hsa-miR-20a and Ki-67 (r = 0.871, P < 0.001), and hsa-miR-20a and CD34 (r = 0.890, P < 0.001) was found.  Dysregulation of miRNAs and correlation with molecular histopathology indicate a biological role for miRNAs in various cellular processes including cell proliferation and angiogenesis in CRC development.  On the other hand, the pattern of miRNA expression and its correlation with histological markers are potentially valuable to apply as diagnostic biomarkers for CRC.