5’tiRNA-Pro-TGG,a novel tRNA halve,promotes oncogenesis in sessile serrated lesions and serrated pathway of colorectal cancer

BACKGROUND Transfer RNA(tRNA)-derived small RNAs(tsRNAs)are small fragments that form when tRNAs severe.tRNA halves(tiRNAs),a subcategory of tsRNA,are involved in the oncogenic processes of many tumors.However,their specific role in sessile serrated lesions(SSLs),a precancerous lesion often observed in the colon,has not yet been elucidated.AIM To identify SSL-related tiRNAs and their potential role in the development of SSLs and serrated pathway of colorectal cancer(CRC).METHODS Small-RNA sequencing was conducted in paired SSLs and their adjacent normal control(NC)tissues.The expression levels of five SSL-related tiRNAs were validated by q-polymerase chain reaction.Cell counting kit-8 and wound healing assays were performed to detect cell proliferation and migration.The target genes and sites of tiRNA-1:33-Pro-TGG-1(5′tiRNA-Pro-TGG)were predicted by TargetScan and miRanda algorithms.Metabolism-associated and immune-related pathways were analyzed by single-sample gene set enrichment analysis.Functional analyses were performed to establish the roles of 5′tiRNA-Pro-TGG based on the target genes.RESULTS In total,we found 52 upregulated tsRNAs and 28 downregulated tsRNAs in SSLs compared to NC.The expression levels of tiRNA-1:33-Gly-CCC-2,tiRNA-1:33-Pro-TGG-1,and tiRNA-1:34-Thr-TGT-4-M25′tiRNAs were higher in SSLs than those in NC,while that of 5′tiRNA-Pro-TGG was associated with the size of SSLs.It was demonstrated that 5′tiRNAPro-TGG promoted cell proliferation and migration of RKO cell in vitro.Then,heparanase 2(HPSE2)was identified as a potential target gene of 5′tiRNA-Pro-TGG.Its lower expression was associated with a worse prognosis in CRC.Further,lower expression of HPSE2 was observed in SSLs compared to normal controls or conventional adenomas and in BRAF-mutant CRC compared to BRAF-wild CRC.Bioinformatics analyses revealed that its low expression was associated with a low interferonγresponse and also with many metabolic pathways such as riboflavin,retinol,and cytochrome p450 drug metabolism pathways.CONCLUSION tiRNAs may profoundly impact the development of SSLs.5′tiRNA-Pro-TGG potentially promotes the progression of serrated pathway CRC through metabolic and immune pathways by interacting with HPSE2 and regulating its expression in SSLs and BRAF-mutant CRC.In the future,it may be possible to use tiRNAs as novel biomarkers for early diagnosis of SSLs and as potential therapeutic targets in serrated pathway of CRC.