CircSP3 promotes ccRCC progression and sunitinib resistance via encoding SP3- 461aa to stabilize MYH9 and activate the PI3K-AKT pathway

Background: In recent years, the potential of circular RNAs to encode proteins has garnered significant attention, rendering them a prominent subject of interest. The expression patterns and functional significance of protein-coding circRNAs in clear cell renal cell carcinoma (ccRCC) have yet to be fully elucidated. Thus, the primary objective of this study was to investigate the role of circSP3 in the advancement of ccRCC. Methods: : The clinical significance of circSP3 was assessed through various analytical techniques, including heatmap analysis, RT-qPCR, and RNA-seq in both ccRCC tissues and cells. To further understand the role of circSP3 in ccRCC, several experimental assays were conducted, including colony formation, EdU incorporation, CCK-8 assay, migration, and invasion assays. Additionally, immunoprecipitation, LC-MS/MS, Ubiquitination assay, and site-mutagenesis were employed to investigate the interaction and translation of circSP3. Results: : CircSP3 was overexpressed and acted as an oncogene in ccRCC. High circSP3 expression is correlated with a high TNM stage. (P = 0.024). circSP3 was mainly located in the cytoplasm. which include an IRES sequence that could bind with the ribosome to initiate the translation process. CircSP3 encodes a novel 461-amino acid peptide referred to as SP3-461aa, which promotes the proliferation, migration, and invasion of ccRCC. SP3-461aa protects the MYH9 protein from proteasomal degradation. Moreover, SMYD2 regulates circSP3 expression by methylating TP53 to suppress DHX9 expression. SP3-461aa played a pivotal role in mediating the oncogenic effects of circSP3 by interacting with the MYH9 protein and activating the VEGFA/PI3K-AKT pathway. Furthermore, SP3-461aa was found to enhance sunitinib resistance in vitro and in vivo. Conclusions: : These findings suggested that circSP3 plays an important role in ccRCC development and could be a potential biomarker for the treatment and prognosis of ccRCC.