miR-138 is commonly down-regulated in primary colorectal cancer tissues and colon cancer cell lines. (A) Levels of miR-138 in 36 primary colorectal tumors compared with their adjacent normal tissues. The miR-138 level is normalized to RNU6B, and the P value indicated a significant difference in miR-138 level between paired samples. (B) The expression level of miR-138 in eight colon cancer cell lines and normal colon tissues (n = 8) by quantitative RT-PCR with RNU6B as an internal control. *P < 0.05, **P < 0.01.