Objective  To analyze the expression profile of miR-222 in gastric cancer and identify its target so as to lay necessary basis for research on the function of miR-222 in the initiation and development of gastric cancer.   Methods  Ten paired gastric cancer and adjacent nontumor gastric mucosa tissues were obtained from pathologically-identified patients of Xinqiao Hospital (Chongqing). The total RNA was extracted by Trizol reagent with homogenizers. Real-time PCR was performed to detect the relative level of miR-222. The potential target of miR-222 was predicted by using 3 currently available prediction programs

including TargetScan

MICROCOSM

and PicTar. FOS was chosen because it was predicted by all the 3 programs. The 3′UTR sequence of FOS was obtained by chemical synthesis. This fragment was then cloned into the pMIR-REPORT and pMIR-GFP-REPORT

FOS was validated as a target of miR-222 by diversity assay of luciferase activity and GFP expression. Western blot analysis was performed to assay if Fos was down-regulated by miR-222 at the translational level.   Results  miR-222 was upregulated in 70% gastric cancer tissues (7/10). It was found miR-222 had potential conservative target seeding sites of FOS in various species including human beings by above-mentioned 3 prediction programs. It was proved that miR-222 targeted to FOS at mRNA level by luciferase assay and GFP repression experiments

and FOS was also suppressed by miR-222 at protein level.   Conclusion  miR-21 may serve as a biomarker for gastric cancer

and miR-222 may play a role in gastric cancer by targeting FOS.