Abstract:

Background and purpose: tRNA-derived fragments (tRF) are a kind of short non-coding RNA (14-30 nt) that influences the course of cancer. This study aimed to investigate the molecular pathways that might underlie the effects of tRF-Pro-CGG on the biological behavior of mouse pancreatic cancer cells. Methods: Real-time fluorescence quantitative polymerase chain reaction (RTFQ-PCR) was used to assess the expression of tRF-Pro-CGG in mouse pancreatic cancer cell lines pan02 and LTPA, human pancreatic cancer cell line Capan-2, and normal pancreatic cells HPDE6-C7. tRF-Pro-CGG overexpression in pan02 cells and LTPA cell suppression were achieved through lentiviral transfection, and RTFQ-PCR and Western blot were used to determine overexpression and knockdown effects. Cell counting kit-8 (CCK-8) was used to detect cell proliferation. Transwell assays were used to detect cell migration and invasion ability. The effect of tRF-Pro-CGG on the growth and metastasis of pancreatic cancer transplantation tumors in nude mice model was investigated. H-E staining was used to observe the histopathological structure of transplantation tumors. Western blot was used to detect the expression and phosphorylation of proliferation-related protein Ki-67 and metastasis-related proteins. Western blot was used to assess the expressions of cadherin, vimentin, phosphoinositide 3-kinase/protein kinase B (PI3K/AKT) pathway protein and phosphorylation in transplanted tumor tissues. Results: tRF-Pro-CGG expression was lowest in the mouse pancreatic cancer cell line pan02. Both mRNA and protein expression levels of tRF-Pro-CGG were significantly increased (P <0.01) after transfection of tRF-Pro-CGG mimics in pan02 cells, and cell proliferation ability (P<0.01), cell migration (P<0.001) and invasion ability (P<0.001) were significantly reduced. A significant decrease in the volume (P<0.01) and weight (P<0.001) of transplanted tumors in nude mice was observed, and significant necrotic and apoptotic cells in transplanted tumor were identified. In transplanted tumor tissues of nude mice, the Ki-67 proliferatien index and expression of vimentin were significantly decreased (P<0.001), while E-cadherin was increased (P<0.001). The expressions of PI3K, P-PI3K, AKT and P-AKT were significantly decreased (P<0.001). There was no significant difference in the number of liver metastases from pancreatic cancer (P>0.05). The mouse pancreatic cancer cell line LTPA had the greatest level of tRF-Pro-CGG expression. The mRNA and protein expression levels of tRF-Pro-CGG were significantly reduced (P<0.01) after transfection of tRF-Pro-CGG inhibitor in LTPA cells. The proliferation ability of cells was significantly increased (P<0.01), the migration of cells (P<0.001) and invasive ability (P<0.001) were significantly increased. The volume (P<0.01) and weight (P<0.01) of transplanted tumors in nude mice were significantly increased, and a limited proportion of necrotic and apoptotic cells were seen in nude mice tumor tissues implanted. In the transplanted tumor tissues of nude mice, the Ki-67 proliferation index and expression of vimentin were significantly increased (P<0.001), while E-cadherin was decreased (P<0.001). The expressions of PI3K, P-PI3K, AKT, and P-AKT were significantly increased (P<0.001). There was no difference in the number of liver metastases from pancreatic cancer (P>0.05). Conclusion: Overexpression of tRF-Pro-CGG reduced pancreatic cancer cell proliferation, migration and invasion in mice, slowed the formation of pancreatic cancer transplanted tumors in nude mice, and decreased Ki-67 proliferation index and expression of vimentin and PI3K/AKT phosphorylation levels. The PI3K/AKT signaling pathway may be regulated by tRF-Pro-CGG, which may suppress the development of pancreatic cancer.

Key words: Pancreatic cancer, tRNA-derived fragments-Pro-CGG, Proliferation, Migration, Invasion, Tumor transplantation model in nude mice