Identification of tRF-29-79MP9P9NH525 as a biomarker and tumor suppressor of gastric cancer via regulating KIF14/AKT pathway.

Gastric cancer (GC) is one of the most common malignancies with a poor prognosis. The development of novel biomarkers is of utmost importance to screen patients with GC. Molecular mechanism study of GC may provide a research basis for the development of targeted drugs. We identified tRF-29-79MP9P9NH525 (tRF-29) as a GC-associated tRNA-derived fragment (tRF). The specific hair-pin structure reverse primer and amplification primers were first designed and then applied for tRF-29 quantification. Receiver operator characteristic curve, Kaplan-Meier survival curve, and multivariate Cox analysis were applied to analyze the diagnostic and prognostic values of tRF-29 in GC. Ethynyl-2'-deoxyuridine, cell cloning, Transwell assay, and flow cytometry were used to detect the effects of tRF-29 on proliferation, migration, and cell cycle distribution of GC cells. Xenograft tumor formation in NOD-SCID mice was applied in determining tRF-29's effects on tumor growth. Fluorescence in situ hybridization, dual luciferase reporter assay, Western blot, immunohistochemistry, and RNA-binding protein immunoprecipitation were conducted to explore the molecular mechanism underlying tRF-29 regulating GC development. It was found that tissue tRF-29 showed effective diagnostic efficiency in GC and could discriminate different gastric mucosa. Besides, plasma tRF-29 improved GC diagnostic values of common tumor markers and had prognostic values in GC. tRF-29 was found to suppress proliferation and cell cycle progression. tRF-29 inhibited the growth of xenograft tumors. Mechanically, tRF-29 exerted Kinesin family member 14 (KIF14) mRNA destabilization by combining with argonaute 2 (Ago2) and regulated AKT/P27 pathway. In conclusion, tRF-29 inhibited GC progression by combining with Ago2 and regulated AKT/P27 pathway by silencing KIF14 expression. In normal cells, tRF-29, derived from tRNA-ValACC, targets the 3'UTR region of KIF14 mRNA by forming RNA silencing complex with Ago2. Reduced KIF14 results in less phospholation of AKT. Subsequently, the expression of P27 is increased, while the expression of MMP-2 is decreased. Finally, the cell cycle is arrested, and the cell proliferation is suppressed, as well as the metastasis is inhibited. In gastric cancer cells, due to the downregulated of tRF-29, the expression of KIF14 is increased, thus the cell proliferation and metastasis are promoted via AKT pathway.