ABSTRACT
Colorectal cancer is the third most common cancer in the world. Non-coding RNA especially miRNAs have important regulatory roles in cancer. miRNAs are small non coding RNA 21-23 nucleotides long which have different levels of expression between tumors and normal tissues. This study was designed to compare expression level of miRNA-21 between Iranian population colorectal cancer tissues and normal tissue. This case-control study has performed in medical genetics department of Tehran University of Medical Sciences from January to November 2013. We used 35 samples. The samples were isolated from tumor and adjacent normal tissues of colon. Thirty-five samples were divided into different groups according to cliniopathologic features including tumor size [>4 and <4 cm], metastasis [+ and -] and stage. After small RNA extraction from tissues by small RNA purification kit the quality and quantity of extracted RNA was determined using spectrophotometry. cDNAs were synthesized and real-time polymerase chain reaction carried out. Finally expression levels were statistically analyzed by LinRegPCR and REST software. miRNA-21 expression ratio in stages I, II and III were 1/804 and 4/574, respectively, the increase from stage III was statistically significant [P= 0.037]. The expression were also studied according to different clinicopathologic status of colon cancer, tumor size [>4 and <4 cm] and metastatic [+ and -], miRNA-21 over expressed in both groups, however the increase was not statistically significant. In this study, we found miR-21 over-expression in advanced stage in tumoral tissue comparing with normal adjacent tissue. This means perhaps in the future it would be possible to use miRNA-21 as an informative prognostic biomarker to guide for better treatment strategies for colorectal cancer patients. Our findings also indicate that miRNA-21 is a promising new molecular target for designing novel therapeutic strategies to control colorectal cancer