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Siqi Liu, Xin Sun, Na Liu, Fangcai Lin Department of Breast Surgery, Beijing Electric Power Hospital, Beijing, 100071, People’s Republic of ChinaCorrespondence: Fangcai Lin, Beijing Electric Power Hospital, Beijing, 100071, People’s Republic of China, Email bjdltgyx@163.comBackground: Insulin-like growth factor 2 mRNA-binding protein 2 (IGF2BP2), an RNA-binding protein with N6-methyladenosine (m6A) reader function, is associated with the poor prognosis of various tumors, including triple-negative breast cancer (TNBC). Small nuclear ribonucleoprotein D1 polypeptide (SNRPD1), a spliceosome member, exerts diagnostic and therapeutic functions in breast cancer by regulating the cell cycle and is a potential therapeutic target. However, the interaction between IGF2BP2 and SNRPD1 in the progression of TNBC remain unclear.Objective: This study aimed to investigate the interaction between IGF2BP2 and SNRPD1 in TNBC and elucidate the underlying mechanisms.Methods: Quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot were used to detect the expression levels of SNRPD1 and IGF2BP2 in human normal breast cells (MCF10A) and TNBC cells (MDA-MB-231). MDA-MB-231 cells were transfected with SNRPD1 interference or overexpression vectors, or co-transfected with SNRPD1 interference and IGF2BP2 overexpression vectors simultaneously. Cell viability, apoptosis, and invasion were assessed using MTT, flow cytometry, and Transwell assays. RNA stability, m6A levels, and the interaction between SNRPD1 and IGF2BP2 were evaluated using qRT-PCR, methylated RNA immunoprecipitation, and RIP assays.Results: SNRPD1 was significantly up-regulated in TNBC cells, promoting cell viability and invasion while inhibiting apoptosis. IGF2BP2 was also up-regulated in TNBC cells and enhanced SNRPD1 mRNA stability via m6A modification. Furthermore, IGF2BP2 overexpression reversed the anti-tumor effect of SNRPD1 knockdown.Conclusion: IGF2BP2 and SNRPD1 were significantly highly expressed in TNBC cells. IGF2BP2 might enhance the stability and protein expression of SNRPD1 through m6A-dependent mechanisms, potentially contributing to the progression of TNBC.Keywords: triple-negative breast cancer, IGF2BP2, SNRPD1, m6A-dependent

Abstract Background Cancers harboring spliceosome mutations are highly sensitive to additional perturbations on the spliceosome that leads to the development of onco-therapeutics targeting the spliceosome and opens novel opportunities for managing aggressive tumors lacking effective treatment options such as triple negative breast cancers. Being the core spliceosome associated proteins, SNRPD1 and SNRPE have been both proposed as therapeutic targets for breast cancer management. Yet, their differences regarding their prognostic and therapeutic use as well as roles during carcinogenesis are largely unreported. Methods We conducted in silico analysis at gene expression and genetic levels to differentiate the clinical relevance of SNRPD1 and SNRPE, and explored their differential functionalities and molecular mechanistic associations with cancer in vitro. Results We showed that high SNRPD1 gene expression was prognostic of poor breast cancer survival whereas SNRPE was not. The SNRPD1 expression quantitative trait loci, rs6733100, was found independently prognostic of breast cancer survival using TCGA data. Silencing either SNRPD1 or SNRPE independently suppressed the growth of breast cancer cells, but decreased migration was only observed in SNRPD1-silenced cells. Knocking down SNRPD1 but not SNRPE triggers doxorubicin resistance in triple negative breast cancer cells. Gene enrichment and network analyses revealed the dynamic regulatory role of SNRPD1 on cell cycle and genome stability, and the preventive role of SNRPE against cancer stemness that may neutralize its promotive role on cancer cell proliferation. Conclusion Our results differentiated the functionalities of SNRPD1 and SNRPE at both prognostic and therapeutic levels, and preliminarily explained the driving mechanism that requires additional explorations and validations.

Abstract Background SNRPD1 is a spliceosome-associated protein and has previously been implicated with important roles in cancer development. Methods Through analyzing the differential expression patterns and clinical association of splicing associated genes among tumor and tumor adjacent samples across different tumors and among different breast cancer subtypes, we identify the tumor promotive role of SNRPD1 using multiple publicly available datasets. Through pathway, gene ontology enrichment analysis and network construction, we linked the onco-therapeutic role of SNRPD1 with cell cycle. Via a series of experimental studies including knockdown assay, qPCR, western blotting, cell cycle, drug response assay, we confirmed the higher expression of SNPRD1 at both gene and protein expression levels in triple negative breast cancer cells, as well as its roles in promoting cell cycle and chemotherapy response. Results Our study revealed that SNRPD1 over-expression was significantly associated with genes involved in cell cycle, cell mitosis and chromatin replication, and silencing SNRPD1 in breast cancer cells could lead to halted tumor cell growth and cell cycle arrest at the G0/G1 stage. We also found that triple negative breast cancer cells with reduced SNRPD1 expression lost certain sensitivity to doxorubicin whereas luminal cancer cells did not. Conclusions Our results suggested the prognostic value of SNRPD1 on breast cancer survival, its potential as the therapeutic target halting cell cycle progression for breast cancer control, and warranted special attention on the combined use of doxorubicin and drugs targeting SNRPD1.