The role of RRS1 in breast cancer cells metastasis and AEG-1/AKT/c-Myc signaling pathway.

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Breast cancer is the most common malignant tumor in women. Recurrence, metastasis, and chemotherapy resistance are the main causes of death in breast cancer patients. The inhibition of breast cancer metastasis is of great significance for prolonging its survival. Ribosome biogenesis regulatory protein homolog (RRS1) is overexpressed in breast cancer tissues and is involved in regulating the carcinogenic process of breast cancer cells. However, the exact signaling pathway and molecular mechanism of RRS1 promoting breast cancer metastasis are not fully understood. Hence, the primary objective of our study is to investigate the correlation between RRS1 and breast cancer metastasis. Bioinformatic analysis was used to identify the expression levels and prognostic significance of RRS1 in breast cancer. Lenti-sh RRS1 lentivirus was constructed and employed to downregulate the RRS1 expression in MDA-MB-231 and BT549 cells, which had a high-level expression of RRS1. Subsequently, we assessed the impact of RRS1 downregulation on the proliferation, migration, and invasion of breast cancer cells using CCK-8, apoptosis, and cell cycle by flow cytometry, wound healing test, Transwell migration, and invasion experiments. Moreover, we utilized an in vivo imaging system to examine the metastatic potential of breast cancer cells after RRS1 knockdown. Picrate staining and hematoxylin-eosin staining were employed to evaluate the presence of metastatic lesions. To gain a deeper understanding of the molecular mechanism, we conducted co-immunoprecipitation and western blot. The significant overexpression of RRS1 in breast cancer indicates a worse prognosis, as determined through TCGA databases (p<0.01). Additionally, RRS1 exhibits upregulation in breast cancer (p<0.001), which is tightly linked to the occurrence of lymph node metastasis (p<0.001). Clinical breast cancer tissues and breast cancer cell lines also demonstrated a noteworthy upregulation of RRS1 (p<0.05). Loss-of-function experiment illustrated that the inhibiting of RRS1 expression reduced the rapid proliferation capacity of MDA-MB-231 and BT549 cells and hindered their migration and invasion capabilities (p<0.05). Importantly, the suppression of RRS1 significantly diminished lung metastasis in Balb/c nude mice that were injected with MDA-MB-231 cells (p<0.01). Mechanistically, RRS1 may interact with the AEG-1 to modulate the phosphorylation of AKT at T308 and S473, consequently impeding the activity of c-Myc (p<0.05). To conclude, RRS1 functions as a potential oncogene in breast cancer by leveraging the AEG-1/AKT/c-Myc signaling.