MicroRNA-638 inhibits cell proliferation by targeting phospholipase D1 in human gastric carcinoma

MicroRNAs （miRNAs） are a type of small non-coding RNAs that are often play important roles in carcinogene- sis, but the carcinogenic mechanism of miRNAs is still unclear. This study will investigate the function and the mechanism of miR-638 in carcinoma （GC）. The expres- sion of miR-638 in GC and the DNA copy number of miR- 638 were detected by real-time PCR. The effect of miR-638 on cell proliferation was measured by counting kit-8 assay. Different assays, including bioinformatics algo- rithms （TargetScan and miRanda）, luciferase report assay and Western blotting, were used to identify the target gene of miR-638 in GC. The expression of miR-638 target gene in clinical CRC tissues was also validated by immunohistochemical assay. From this research, we found that miR-638 was downregulated in GC tissues compared with corresponding noncancerous tissues （NCTs）, and the DNA copy number of miR-638 was lower in GC than NCTs, which may induce the corresponding downregulation of miR-638 in GC. Ectopic expression of miR-638 inhibited GC cell growth in vitro. Subsequently, we identified that PLD1 is the target gene of miR-638 in GC, and silencing PLD1 expression phenocopied the inhibitory effect of miR-638 on GC cell proliferation. Fur- thermore, we observed that PLD1 was overexpressed inGC tissues, and high expression of PLDt in GC predicted poor overall survival. In summary, we revealed that miR- 638 functions as a tumor suppressor in GC through inhibiting PLDI.