LARP6 promotes carcinogenic features of triple negative breast cancer cell line by directly modulating alternative splicing of associated genes [RNA-Seq]
Purpose: Triple-negative breast cancer (TNBC) has the highest mortality rate of all breast cancer subtypes and currently lacks effective targeted therapies. LARP6 is an RNA-binding protein associated with cancer promotion, but its mechanism of action in TNBC remains unclear. Methods: Firstly, Western blot (WB) was used to detect the expression level of LARP6 protein in TNBC cell lines. The effects of LARP6 overexpression on TNBC cell proliferation and invasion were determined through Cell Counting Kit-8 (CCK-8) and Transwell experiments. Next, RNA sequencing (RNA-seq) and improved RNA immunoprecipitation and sequencing (iRIP-seq) were performed to analyze LARP6-bound and regulated differentially expressed genes (DEGs) and alternative splicing (AS) events in MDA-MB-231 cells. Finally, RT-qPCR and RIP-qPCR were used for confirmation. Result:Our study found that the overexpressed LARP6 TNBC cell lines significantly promoted thetumor cell proliferation and invasion of cancer (P<0.05). RNA-seq showed that LARP6 overexpression alteredaffected the expression levels of 171 genes, whileand combined with iRIP-seq, it revealedshowed that only EGR1 and LARP6 were bounddirectly bind to by the LARP6 protein, indicating. This shows that LARP6 hasis a weak ability to bind to and regulate differential expression of in regulating genes expression. However, the number of regulatedrelated alternative splicing evensgenes (RASEGs) was upwards ofreached more than 1000, and the correspondingthese genes (RASGs) were mainly enriched in important pathways such as DNA repair and cellular response to DNA damage stimulus. In addition, bassaed on  binding peak calling of iRIP-seq in both IP samples,Through analysis of binding peaks, we found that there were 321 overlapping binding peaks in both IP samples between IP1 and IP2 samples awere identified, in whichnd the genes they were mainly concentrated in the post-transcriptional regulatory pathway, and it was also found that LARP6 might tend to bind motif. The top 5 binding motifs were obtained using HOMER, among which CGACGAG was the binding motifsequence that appeared simultaneously in both IP groups. The intersection of binding peak-related genes andwith RASGs suggestedrevealed that LARP6 could bind to 16 genes and regulate their alternative splicing, thus playing an important role in TNBC progression. directly bind to LARP6, most of which were related to cell proliferation, invasion and drug resistance. Conclusion: We revealed the mechanism that LARP6 promotes TNBC by directly regulating the AS of related genes, which provides a new clue for the targeted therapy of TNBC. Overall design: In order to clarify the mechanism of LARP6 promoting triple negative breast cancer, RNA-seq and iRip-seq techniques were used to determine the RNA binding targets and motifs of LARP6 in MDA-MB-231 cells, which is helpful to understand the regulation mechanism of LARP6RNA splicing level in triple negative breast cancer and provides a basis for further understanding the role of LARP6 in various biological processes.