Huan Jinliang, Liu Xiaojun, Wang Na, Mu Yuxin, Li Ling, Du Yiqun
Department of General Surgery, Shanghai Eighth People's Hospital, Affiliated Hospital of Jiangsu University, No. 8, Caobao Road, Shanghai, 200235, China.
Department of Medical Oncology, Fudan University Shanghai Cancer Center, No. 4333, Kangxin Road, Shanghai, 201318, China.
Biol Direct. 2024 Dec 20;19(1):131. doi: 10.1186/s13062-024-00578-8.
Ribosomal RNA processing 9 (RRP9) is a specific component of the U3 small nucleolar ribonucleoprotein (U3 snoRNP), which is involved in physiological processes and pathological disorders. The purpose of the current study was to investigate the biological roles of RRP9 in breast cancer (BC) progression.
The expression levels of RRP9 in human BC were assessed by immunohistochemical (IHC) staining, qPCR assay and Western blot. Cells were transfected with shRNA plasmids to regulate RRP9 expression. The functional roles were explored by Celigo cell counting assay, colony formation assay, flow cytometry and Transwell assays, as well as construction of Xenograft tumor model. Furthermore, interaction between RRP9 and JUN was determined by Co-immunoprecipitation (Co-IP) assay, protein stability assay, and ubiquitination assay.
RRP9 expression was substantially upregulated in BC tissues and was positively associated with lymph node metastasis and poor prognosis. Functional experiments indicated that RRP9 depletion inhibited BC progression both in vitro and in vivo. Using a prime-view human gene expression array and IPA, JUN was identified as a potential downstream target of RRP9. Mechanistically, RRP9 interacted with the JUN protein, and RRP9 deletion decreased JUN protein stability by accelerating JUN ubiquitination and led to JUN degradation via MDM2. Moreover, the regulatory effects of RRP9 on BC cell phenotypes were attenuated by JUN knockdown or the AKT signalling pathway activator SC79.
In conclusion, this study revealed the crucial role of RRP9 in BC progression and its probable novel mechanism, suggesting that RRP9 may be a promising candidate for the treatment of BC.
核糖体RNA加工9（RRP9）是U3小核仁核糖核蛋白（U3 snoRNP）的一个特定组成部分，其参与生理过程和病理紊乱。本研究的目的是探讨RRP9在乳腺癌（BC）进展中的生物学作用。
通过免疫组织化学（IHC）染色、qPCR检测和蛋白质免疫印迹法评估RRP9在人乳腺癌中的表达水平。用shRNA质粒转染细胞以调节RRP9表达。通过Celigo细胞计数法、集落形成试验、流式细胞术和Transwell试验以及构建异种移植肿瘤模型来探索其功能作用。此外，通过免疫共沉淀（Co-IP）试验、蛋白质稳定性试验和泛素化试验确定RRP9与JUN之间的相互作用。
RRP9表达在乳腺癌组织中显著上调，且与淋巴结转移和预后不良呈正相关。功能实验表明，RRP9缺失在体外和体内均抑制乳腺癌进展。使用初筛人类基因表达芯片和IPA，JUN被确定为RRP9的潜在下游靶点。机制上，RRP9与JUN蛋白相互作用，RRP9缺失通过加速JUN泛素化降低JUN蛋白稳定性，并导致JUN通过MDM2降解。此外，JUN敲低或AKT信号通路激活剂SC79减弱了RRP9对乳腺癌细胞表型的调节作用。
总之，本研究揭示了RRP9在乳腺癌进展中的关键作用及其可能的新机制，表明RRP9可能是治疗乳腺癌的一个有前景的候选靶点。
