OBJECTIVE: MicroRNA-221 (miR-221), which is located on chromosome X, is an oncogenic microRNA that is involved in several human malignancies. This study aimed to characterize the role of miR-221 in the initiation and malignant progression of gastric cancer. METHODS: The level of miR-221 expression in 92 pairs of primary gastric tumour tissue and adjacent nontumour tissue was quantified by real-time reverse transcription—polymerase chain reaction. The relationship between the miR-221 level and clinicopathological features was explored. RESULTS: MiR-221 was up-regulated in 88% (81/92) of gastric cancer tissue samples compared with their paired adjacent nontumour tissue samples. High expression of miR-221 showed a significant correlation with advanced tumour—node—metastasis stage, local invasion and lymphatic metastasis. Univariate and multivariate Cox proportional hazard regression analyses revealed that miR-221 overexpression was an unfavourable prognostic factor for overall survival in patients with gastric cancer. CONCLUSIONS: These findings suggest that miR-221 is a novel prognostic indicator in gastric cancer and may be a potential target for diagnosis and gene therapy.
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