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Abstract Background Hepatocellular carcinoma (HCC) is a common type of malignant tumor where the prognosis is dismal. Circular RNA (CircRNA) is a novel RNA that regulates downstream gene transcription and translation to influence the progression of HCC. However, the regulatory relationship that exists between E3 ligases, which is a class of post-translational modifying proteins, and circRNA remains unclear. Methods Based on the E3 ubiquitin ligase in the competitive endogenous RNA (ceRNA) network, a circRNA-regulated E3 ubiquitin ligase signature (CRE3UL) was developed. A CRE3UL signature was created using the least absolute shrinkage and selection operator (Lasso) and Cox regression analysis and merged it with clinicopathologic characteristics to generate a nomogram for prognosis prediction. The pRRophetic algorithm was utilized and immunological checkpoints were analyzed to compare the responses of patients in the high-risk group (HRG) and low-risk group (LRG) to targeted therapy and immunotherapy. Finally, experimental research will further elucidate the relationship between E3 ubiquitin ligase signature and HCC. Results HRG patients were found to have a worse prognosis than LRG patients. Furthermore, significant variations in prognosis were observed among different subgroups based on various clinical characteristics. The CRE3UL signature was identified as being an independent prognostic indicator. The nomogram that combined clinical characteristics and the CRE3UL signature was found to accurately predict the prognosis of HCC patients and demonstrated greater clinical utility than the current TNM staging approach. According to anticancer medication sensitivity predictions, the tumors of HRG patients were more responsive to gefitinib and nilotinib. From immune-checkpoint markers analysis, immunotherapy was identified as being more probable to assist those in the HRG. Conclusions We found a significant correlation between the CRE3UL signature and the tumor microenvironment, enabling precise prognosis prediction for HCC patients. Additionally, a nomogram was developed that performs well in predicting the overall survival (OS) of HCC patients. This provides valuable guidance for clinicians in devising specific personalized treatment strategies. Graphical Abstract

Abstract Background The role of the membrane-associated RING-CH (MARCH) family in carcinogenesis has been widely studied, but the member of this family, RNF173, has not yet been thoroughly explored in the context of hepatocellular carcinoma (HCC). Methods With the use of an HCC tissue microarray and IHC staining, we aim to determine the differential expression of RNF173 in HCC patients and its clinical significance. The biological role of RNF173 is investigated through in vitro and in vivo experiments. RNA sequencing, mass spectrometry, and immunoprecipitation are performed to uncover the underlying mechanism of RNF173's impact on the development of HCC. Results The mRNA and protein levels of RNF173 were significantly lower in HCC tissues than in normal tissues. HCC patients with low RNF173 expression had shorter overall survival and recurrence-free survival, and RNF173 was significantly correlated with tumor number, tumor capsule, tumor differentiation, and BCLC stage. In addition, in vitro and in vivo experiments showed that RNF173 downregulation exacerbated tumor progression, including migration, invasion, and proliferation. GRB2 is a key molecule in the RAF/MEK/ERK pathway. RNF173 inhibits the RAF/MEK/ERK signaling by ubiquitinating and degrading GRB2, thereby suppressing HCC cell proliferation, invasion and migration. Combining clinical samples, we found that HCC patients with high RNF173 and low GRB2 expression had the best prognosis. Conclusion RNF173 inhibits the invasion and metastasis of HCC by ubiquitinating and degrading GRB2, thereby suppressing the RAF/MEK/ERK signaling pathway. RNF173 is an independent risk factor for the survival and recurrence of HCC patients. RNF173 may serve as a novel prognostic molecule and potential therapeutic target for HCC. Video Abstract Graphical Abstract Graphical abstract Model of RNF173 on RAF/MEK/ERK signaling. RNF173 knockdown resulted in impaired ubiquitination and degradation of GRB2, leading to the activation of the RAF/MEK/ERK signaling pathway and promotion of invasion and metastasis in HCC cells.