HCC, which ranks third in terms of cancer-related mortality on a global scale, has an alarmingly high recurrence rate within 5 years, mainly owing to uncontrolled proliferation and metastasis[8]. Additionally, prognosis prediction is considerably more challenging due to the substantial heterogeneity of HCC and the presence of numerous risk factors[37]. Therefore, efforts should be undertaken to fully comprehend the mechanism and identify the targets of HCC progression. SNRPB2 is involved in pre-mRNA splicing as a component of the spliceosome, and has been reported to be closely linked to the drug resistance of ixazomib on multiple myeloma cells[16, 17]. However, the role of SNRPB2 and its related regulatory mechanisms in cancers are still largely unknown, and the precise mechanism of SNRPB2 in the progression of HCC remains unexplored. Here, we thoroughly investigated the expression, prognostic and diagnostic value, effect on tumorigenesis and ferroptosis, corresponding ceRNA regulatory axis, and the specific role in the sorafenib resistance of SNRPB2 in HCC.
As a critical component of the splicesome, SNRPB2 has been proven to exhibit a higher expression level and be associated with poor outcomes in multiple myeloma patients[17], while the SNRPB2 expression profile in cancers still remains largely unknown, and the expression level and clinical implications of SNRPB2 in HCC also remain elusive. In this study, we initially assessed the level of SNRPB2 expression in pan-cancer to find that SNRPB2 was upregulated in most cancer types. Then, we showed SNRPB2 significantly overexpressed in HCC relative to normal liver tissue by employing TCGA + GTEx, GEO, and HPA, and the results of RT-qPCR, western blot, and IHC on clinical HCC tissues further demonstrated it. In addition, Kaplan-Meier plotter indicated that OS, DSS, and PFI were unfavorable in HCC patients with elevated SNRPB2 expression, which was further supported by the survival analysis of HCC patients from Zhuzhou Central Hospital. Elevated SNRPB2 expression was an independent risk factor for OS in HCC, as determined by cox regression analysis. Moreover, the ROC curve analysis demonstrated SNRPB2's superior HCC diagnostic ability. Taken together, SNRPB2 is overexpressed and exhibits great prognostic and diagnostic values in HCC.
A recent study indicated that knockdown of SNRPB2 may result in inhibition of aggressive behavior in multiple myeloma cells[17]. However, the precise impact of SNRPB2 expression on the malignant phenotype of HCC is still unknown. Here, we identified that SNRPB2 deletion effectively reduced the proliferation, colony formation, and migration of HCC cells in vitro, and the prevention of tumor growth was further confirmed using xenograft nude mouse model with SNRPB2 knockdown. Conclusively, these findings indicate that SNRPB2 could facilitate the development of HCC.
Ferroptosis is a newly identified type of non-apoptotic iron-dependent cell death mediated by lipid peroxidation[38]. It is believed that inducing ferroptosis decelerates the progression of tumors[39, 40]. Several clinical and preclinical medications, such as RSL-3 and sorafenib, have been shown to trigger ferroptosis and have anti-tumor effects in HCC[41]. In this study, we discovered that SNRPB2 was critical in ferroptosis-related pathways, including “Ferroptosis”, “Oxidative stress response”, “Iron ion homeostasis” and “Glutathione metabolic process” as determined by GSEA. The colony formation experiment showed that the depletion of SNRPB2 decreased the clonogenic potential of HCC cells treated with RSL-3. And IHC tset indicated that 4-HNE, an indicator of ferroptosis, was negatively associated with SNRPB2 expression. In addition, the CCK8 analysis revealed that inhibiting SNRPB2 increased ferroptosis of HCC cells. Moreover, SNRPB2 deletion decreased GSH while increasing lipid ROS and ferrous iron. In conclusion, our study is the first to show that SNRPB2 is an essential regulator of ferroptosis and could be potentially targeted for the elimination of HCC cells.
LncRNAs, functioning as ceRNAs, play a crucial role in HCC carcinogenesis by modulating downstream mRNAs expression via target miRNA sequestration[21, 42]. Growing evidence indicates that aberrant ceRNA regulation closely associates with ferroptosis in cancer cells, such as LINC00336 inhibits ferroptosis promoted by miR-6852 in lung carcinoma when used as a ceRNA[43], and the NEAT1-miR-362-3p-MIOX axis is crucial in HCC ferroptosis initiation[21]. Here, we first demonstrated that SNRPB2 was regulated by the SNHG4/miR-204-5p axis through public database prediction, correlation analysis, luciferase reporter assays, and RT-qPCR. In addition, biological function experiments revealed that suppression of proliferation, colony formation, and cell migration of HepG2 cells with SNRPB2 deletion was reversed by the overexpression of SNHG4. Moreover, enhanced SNHG4 could rescue HCC cell ferroptosis as indicated by the reduced cell death, lipid ROS level and ferrous iron and increased GSH in SNRPB2 knockdown HepG2 cells. Together, our findings suggest that SNRPB2 is regulated by the SNHG4/miR-204-5p axis, and SNHG4 could reverse the tumor suppression and ferroptosis triggering induced by deletion of SNRPB2, as a ceRNA of miR-204-5p.
Sorafenib resistance continues to be a treatment obstacle and is associated with a poor prognosis in HCC[44]. Consequently, a thorough understanding of the fundamental mechanism that underlies sorafenib resistance in HCC could potentially improve the effectiveness of chemotherapy and direct clinical medication. Herein, we revealed that SNRPB2 was elevated in SR HCC cells by bioinformatics analysis and detection of the SNRPB2 expression level in SR HepG2 cells. Additionally, CCK8 assays demonstrated that SNRPB2 deletion increased the sensitivity of HCC cells to sorafenib. Moreover, flow cytometry analysis indicated that deletion of SNRPB2 raised the lipid ROS level of HepG2 cells treated with sorafenib, indicating SNRPB2 may contribute to the sorafenib resistance through inhibiting ferroptosis of HCC cells. Last, we used drug sensitivity analysis and molecular binding prediction to reveal the potential of targeting SNRPB2 to improve the likelihood of unfavorable prognosis in HCC. These findings suggest that SNRPB2 is expected to be a novel potential molecular therapeutic target for enhancing life quality and sorafenib resistance in HCC patients.
In conclusion, our study indicated that elevated SNRPB2 expression is an independent prognostic risk factor in HCC. Additionally, we demonstrated that SNRPB2 accelerates HCC progression by inhibiting ferroptosis. Moreover, the SNHG4/miR-204-5p axis could regulate SNRPB2 to reverse the tumor inhibition induced by the deletion of SNRPB2. Furthermore, we discovered that SNRPB2 has a role in sorafenib resistance in HCC. Thus, SNRPB2 could be a promising target for HCC treatment (Fig. 7I). However, the specific molecular mechanism and signaling pathways of SNRPB2 regulating ferroptosis and sorafenib resistance have not been investigated in this study, which could be our next research direction.