| Background:The carcinogenesis of malignant tumors is resulted from the interaction between genomes and environmental factors.Only 2%of genomes are protein-encoding ones,and the majority belong to non-coding genes.Among the latter subtype,those with a transcript length longer than 200 nt and lack of an open reading frame are known as long non-coding RNAs(lncRNAs).Existing lines of evidence have shown that lncRNAs are widely involved in tumor development and progression.Our previous data have demonstrated the tumor-suppressor role of DUXAP8 in pancreatic cancer by downregulating KLF2 and P21.It is reported that highly expressed LINC00460 in gastric cancer accelerates cell cycle transitions by inhibiting the transcription of CCNG2.Gastric cancer is one of the most prevalent digestive system cancers.In China,over 80%of gastric cancer are diagnosed as progressive stage and their prognosis is relatively poor because effective diagnostic,therapeutic and prognostic markers are lacked.Zhang et al.have identified biological functions of LINC01446 in glioblastoma.Its potential involvement in the development of gastric cancer,however,reamians unclear.We explore the biological functions of LINC01446 in gastric cancer cells and the underlying molecular mechanism,aiming to provide references for clinical diagnosis and treatment of gastric cancer.Methods:(1)Genomic information of LINC01446 and its protein-encoding ability were predicted by bioinformatic tools.The full-length sequence of LINC01446 in gastric cancer cell lines was identified using RACE technology.(2)Differential levels of LINC01446 in gastric cancer tissues and normal ones from TCGA database were analyzed by paired Student’s t test,which were further verified in 100 pairs of gastric cancer specimens and paracancerous ones by qRT-PCR.(3)Chi-square test was applied to assess the correlation between LINC01446 level and pathological indexes of gastric cancer patients.The prognostic potential of LINC01446 in gastric cancer was assessed by analyzing gastric cancer data from TCGA database and follow-up data of recruited 100 patients in our center.(4)After over expression or knockdown of LINC01446,the influences of LINC01446 on proliferation,apoptosis,migration and invasion of gastric cancer cells in vitro were examined.(5)Xenograft mouse models were performed by administrating gastric cancer cells with LINC01446 knockdown in nude mice,followed by determining the influences of LINC01446 on proliferation,migration and invasion in vivo.(6)The influences of silenced LINC01446 on biological functions of primary gastric cancer cells isolated from clinical specimens were explored.(7)Subcellular distribution of LINC01446 in gastric cancer was determined using cytoplasmic and nuclear fractionation kit and FISH.(8)The interaction between LINC01446 and the histone demethylase LSD1 was verified through bioinformatic prediction,RIP and RNA-pull down assay.(9)After knockdown of LSD1,cell proliferation,migration and invasion of GC in vitro were detected.(10)After knockdown of LINC01446,potential changes of downstream genes were determined by RNA transcriptome sequencing,which were further verified by qRT-PCR and Western blotting.(11)The influences of overexpressed RASD1 on proliferation,migration and invasion of gastric cancer cells in vitro were detected.(12)Regulatory effects of LINC01446 on the LSD1/RASD1 axis were examined by ChIP,immunohistochemistry and rescue experiments.Results:(1)LINC01446 was ocated on human chromosome 7p12.1,containing 6 exons.It had 8 transcripts and among them,LINC01446-vl was 3,484 bp long.(2)Compared with normal or paracancerous tissues from TCGA database and those collected in our center,LINC01446 and LSD1 were unregulated in gastric cancer tissues,whilst RASD1 was downregulated.Moreover,high level of LINC01446 was unfavorable to the prognosis of gastric cancer.(3)Knockdown of LINC01446 inhibited proliferation,migration and invasion of GC cells,and induced apoptosis in vitro.Overexpression of LINC01446 yielded the opposite results.(4)In vivo knockdown of LINC01446 inhibited tumorigenecity of gastric cancer in nude mice.In lung metastasis of gastric cancer mice through tail vein administration,in vivo knockdown of LINC01446 inhibited lung metastasis of gastric cancer.(5)Significantly changed downstream genes after knockdown of LINC01446 were enriched in cell proliferation,migration and invasion.(6)Through recruiting LSD1 to the promoter region of RASD1,LINC01446 inhibited the transcription activity of RASD1 by catalyzing demetylation of H3K4me2,this triggering proliferation,migration and invasion of GC cells.Conclusions:(1)LINC01446 is unregulated in gastric cancer tissues than that of normal ones,and in addition,it predicts a poor prognosis of gastric cancer.Therefore,LINC01446 is closely linked to the development of gastric cancer.(2)LINC01446 stimulates proliferation,migration and invasion of GC cells,but inhibits apoptosis.(3)Through binding the histone LSD1,LINC01446 downregulates the tumor-suppressor gene RASD1 at the transcription level,thus exerting the oncogenic role in gastric cancer.(4)LINC01446/LSD1/RASD1 axis is of great significance in the development of gastric cancer. |
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