Background: Recent studies have shown that miR-199a-5p plays opposite roles in cancer initiation and progression\r\nof different cancer types, acting as oncogene for some cancer types but as tumor suppressor gene for others.\r\nHowever, the role and molecular mechanism of miR-199a-5p in gastric cancer are largely unknown.\r\nMethods: In this study, miR-199a-5p expression level in gastric cancer was first analyzed by qPCRand then validated\r\nin 103 gastric cancer patients by in situ hybridization (ISH). Gastric cancer cell lines were transfected with\r\nmiR-199a-5p inhibitor and mimic, and underwent in vitro transwell assays. Target genes (klotho) were identified\r\nusing Luciferase reporter assay. Immunohistochemical staining was also used to investigate on how miR-199a-5p\r\nregulates the tumour-suppressive effects of klotho in gastric cancer.\r\nResults: In our present study, we found that miR-199a-5p level was significantly increased in gastric cancer tissues\r\ncompared to paired normal tissues. We observed that miR-199a-5p could promote migration and invasion of gastric\r\ncancer cells. In situ hybridization of miR-199a-5p also confirmed that higher miR-199a-5p expression level was\r\nassociated with increased likelihood of lymph node metastasis and later TNM stage. Luciferase reporter assay and\r\nimmunohistochemistry revealed that klotho might be the downstream target of miR-199a-5p.\r\nConclusions: Our present study suggests that miR-199a-5p acts as an oncogene in gastric cancer and functions by\r\ntargeting klotho.
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