LncRNA-encoded Polypeptide ASRPS Inhibits Triple-negative Breast Cancer Angiogenesis

Background:Breast cancer has become the most common cancer worldwide.Triple-negative breast cancer(TNBC)does not express the three most common breast cancer(BC)markers,estrogen receptor(ER),progesterone receptor,and HER2/neu oncogene(HER2).TNBC accounts for 15%of all BCs,but it is the most aggressive subtype of BC and is associated with worst prognosis and overall survival.However,few studies have been reported about the difference between triple-negative breast cancer and other non-TNBC.In human genome,only 1-2%of the region could transcript to protein-coding mRNA,most of the transcripts are non-coding RNA.LncRNA(long non-coding RNA)is a subtype of non-coding RNA,which contains more than 200 nucleotides.Numerous lncRNAs have been shown to regulate cancer progression through chromosomal modification,epigenetic modification,transcriptional regulation,and alternative splicing regulation.However,the regulatory role of lncRNAs in TNBC is still litter known.Therefore,it is necessary to explore the regulatory mechanism of lncRNA in triple-negative breast cancer.Methods:(1)We identified TNBC-specific lncRNAs from The Cancer Genome Atlas(TCGA)database and predicted the lncRNAs with coding potential using the GWIPS-viz dataset.(2)We identified target lncRNA from candidate lncRNAs by qPCR、Polysome profiling.(3)We verified that LINC00908 contains small ORFs encoding a 60-aa functional polypeptide by western blotting and immunofluorescence staining.(4)Using ChIP assay and dual-luciferase reporter assay,we proved that ERa directly regulated LINC00908 transcription.(5)Using Co-immunoprecipitation and LC-MS/MS,we investigated the target and mechanism of the polypeptide in TNBC.(6)Through performed ChIP assay,luciferase reporter assays and western blotting,we explored the downsteam signaling pathway of the polypeptide.(7)We performed a series of experiments in vitro to study the function of polypeptides,such as tube formation assay,cell migration and wound healing assay,sprouting assay,etc.(8)Using mouse xenograft breast cancer model and mouse spontaneous BC model,we showed that the polypeptide acted as an antitumor peptide.Results:Our study identified an lncRNAs——LINC00908,which is low expressed in triplenegative breast cancer,from TCGA database and found that it can encode a 60-amino acid micropeptide called ASRPS(a small regulatory peptide of STAT3),which can inhibit the angiogenesis in TNBC.We suggest that ASRPS is a potential prognostic marker and therapeutic target for TNBC.