Introduction: Breast cancer (BC) is one of the most prevalent malignancies in women and its incidence has increased steadily over recent years (0.3% per year). However, the mechanism of BC tumorigenesis remains elaborate elucidation. With the aid of RNA sequencing technology, we discovered that immortalization-upregulated protein (IMUP ) is overexpressed in BC tissues compared to normal breast tissues. Our study is to understand the role of IMUP  in BC.
Methods: We validated the upregulation of IMUP  from multiple public databases. By using quantitative real-time polymerase chain reaction (qRT-PCR), we proved that IMUP  is overexpressed in BC tissues and cell lines. We performed proliferation, migration, invasion and apoptosis assays to explore the function of IMUP  in BC cell lines (MCF-7 and MDA-MB-231). Besides, we investigated the effect of IMUP  silencing on epithelial–mesenchymal transition using Western blotting and qRT-PCR.
Results and Discussion: We validated that IMUP  expression in BC tissues and cell lines is higher than that in the normal control group. The clinical analysis showed that IMUP  is associated with lymph node metastasis and the outcome of neoadjuvant taxol-based therapy. The loss of function assay demonstrated that, with silencing IMUP , the capacities of proliferation, migration, and invasion of BC cell lines were impaired, while the apoptosis rate of cells increased. Meanwhile, the downregulation of IMUP  could hinder the procession of epithelial–mesenchymal transition.
Conclusion: Our study proved that IMUP  plays a vital role in BC and acts as a potential target and marker in future therapy.
Keywords: immortalization-upregulated protein, IMUP, breast cancer, BC, progression, epithelial–mesenchymal transition, EMT