[LncRNA DRAIC regulates the proliferation, apoptosis, migration and invasion of lung adenocarcinoma cells by targeting let-7i-5p].

Objective: To investigate the effects of lncRNA DRAIC on proliferation, apoptosis, migration and invasion of lung adenocarcinoma cells and its mechanism. Methods: Reverse transcription-quantitative real-time polymerase chain reaction (RT-qPCR) was used to detect the expression of DRAIC in lung cancer tissues and corresponding adjacent normal tissues of 40 patients with lung adenocarcinoma who underwent surgery in Tangshan People's Hospital from 2019 to 2020. Lung adenocarcinoma cells A549 and H1299 were cultured in vitro and divided into si-NC group, si-DRAIC group, miR-NC group, let-7i-5p mimics group, si-DRAIC+ inhibitor-NC group, and si-DRAIC+ let-7i-5p inhibitor group. CCK-8 method and clone formation experiment were used to detect cell proliferation. Flow cytometry was used to detect cell apoptosis. Transwell array was used to detect the cell migration and invasion. Western blot was used to detect the protein expressions of Caspase-3, Caspase-9, Bcl-2 and Bax. The double luciferase reporter gene experiment was used to verify the regulatory relationship between DRAIC and let-7i-5p. Independent sample t test was used for comparison between two groups, one-way ANOVA was used for comparison between multiple groups, and Pearson correlation analysis was used for correlation analysis. Results: Compared with adjacent tissues, the expression level of DRAIC in lung adenocarcinoma tissues increased ( P <0.05), but the expression level of let-7i-5p decreased ( P <0.05). The expression levels of DRAIC and let-7i-5p in lung adenocarcinoma tissues were negatively correlated ( r =-0.737, P <0.05). The absorbance value of A549 and H1299 cells in the si-DRAIC group at 48, 72 and 96 hours were lower than those in the si-NC group ( P <0.05), the number of clones formed [(91.00±6.08 vs. 136.67±6.51); (50.67±1.53 vs. 76.67±4.51)], the number of migration [(606.67±31.34 vs. 960.00±33.06); (483.33±45.96 vs. 741.67±29.67)], the number of invasion [(185.00±8.19 vs. 447.33±22.05); (365.00±33.87 vs. 688.00±32.97)] were lower than those in the si-NC group ( P <0.05). However, the apoptosis rates of cells [(13.43±2.79)% vs. (4.53±0.42)%; (23.77±1.04)% vs. (6.60±1.42)%] were higher than those in the si-NC group ( P <0.05). The protein expressions of Caspase-3, Caspase-9 and Bax in si-DRAIC group were higher than those in si-NC group, and the protein expression of Bcl-2 was lower than that in si-NC group ( P <0.05). DRAIC is located in the cytoplasm. DRAIC targeted and negatively regulated the expression of let-7i-5p. The absorbance values of A549 and H1299 cells in the let-7i-5p mimics group at 48, 72 and 96 hours were lower than those in the miR-NC group ( P <0.05), the number of clones formed [(131.33±14.47 vs. 171.33±6.11); (59.33±4.93 vs. 80.33±7.09)], the number of migration [(137.67±3.06 vs. 579.33±82.03); (425.00±11.14 vs. 669.33±21.13)], the number of invasion [(54.00±4.36 vs. 112.67±11.59); (80.00±4.58 vs. 333.33±16.80)] were lower than those in the miR-NC group ( P <0.05). However, the apoptosis rates of cells [(14.57±1.10)% vs. (6.97±1.11)%; (23.97±0.42)% vs. (7.07±1.21)%] were higher than those in the miR-NC group ( P <0.05). The protein expressions of Caspase-3, Caspase-9 and Bax in let-7i-5p mimics group were higher than those in miR-NC group, and the protein expression of Bcl-2 was lower than that in miR-NC group ( P <0.05). The absorbance values of A549 and H1299 cells in the si-DRAIC+ let-7i-5p inhibitor group at 48, 72 and 96 hours were higher than those in the si-DRAIC+ inhibitor-NC group ( P <0.05), the number of clones formed [(82.00±5.29 vs. 59.00±5.57); (77.67±4.93 vs. 41.33±7.57)], the number of migration [(774.33±35.81 vs. 455.67±19.04); (569.67±18.72 vs. 433.67±16.77)], the number of invasion [(670.33±17.21 vs. 451.00±17.52); (263.67±3.06 vs. 182.33±11.93)] were higher than those in the si-DRAIC+ inhibitor-NC group ( P <0.05). However, the apoptosis rates of cells [(7.73±0.45)% vs. (19.13±1.50)%; (8.00±0.53)% vs. (28.40±0.53)%] were lower than those in the si-NC group ( P <0.05). The protein expressions of Caspase-3, Caspase-9 and Bax in si-DRAIC+ let-7i-5p inhibitor group were higher than those in si-DRAIC+ inhibitor-NC group, and the protein expression of Bcl-2 was lower than that in si-DRAIC+ inhibitor-NC group ( P <0.05). Conclusion: DRAIC is highly expressed in lung adenocarcinoma, and DRAIC promotes the proliferation, migration and invasion of lung adenocarcinoma cells and inhibits apoptosis by targeting let-7i-5p.