USP39 promotes malignant proliferation and angiogenesis of renal cell carcinoma by inhibiting VEGF-A165b alternative splicing via regulating SRSF1 and SRPK1

Abstract

Background The benefit of targeted therapy for renal cell carcinoma (RCC) is largely crippled by drug resistance. Rapid disease progression and poor prognosis occur in patients with drug resistance. New treatments demand prompt exploration for clinical therapies. Ubiquitin-specific peptidase 39 (USP39) serves as the pro-tumor factor in several previous studies of other malignant tumors. To investigate the function and mechanism of USP39 in promoting malignant proliferation and angiogenesis of RCC. Methods We applied ONCOMINE database to analyze the correlation between USP39 expression level and the clinical characteristics of RCC. USP39 knockdown or overexpression plasmids were transfected into 786-O and ACHN cells. The HUVEC received cell supernatants of 786-O and ACHN cells with knockdown or overexpression USP39.The effect of USP39 on RCC was evaluated by MTT assay, cell cycle analysis, colony formation assay and tubule formation assay. The interaction between USP39 and VEGF-A alternative splicing was assessed by affinity purification and mass spectrometry, co-immunoprecipitation and Western blot assays. Results The mRNA expression level of USP39 in RCC was significantly higher than that in normal renal tissue (P < 0.001), and negatively correlated with the survival rate of RCC patients (P < 0.01). Silencing of USP39 in 786-O and ACHN cells inhibited cell proliferation and colony formation, and induced S phase arrest. USP39 overexpression significantly increased the number of tubules (P < 0.05) and branches (P < 0.01) formed by HUVEC cells, and USP39 knockdown produced an opposite effect (P < 0.05). The USP39 (101–565) fragment directly mediated its binding to SRSF1 and SRPK1, and promoted the phosphorylation of SRSF1 to regulate VEGF-A alternative splicing. USP39 knockdown upregulated the expression of VEGF-A165b, and USP39 overexpression downregulated the expression of VEGF-A165b significantly (both P < 0.05). Conclusion USP39 acted as a pro-tumor factor by motivating the malignant biological processes of RCC, probably through inhibiting VEGF-A165b alternative splicing and regulating SRSF1 and SRPK1. USP39 may prove to be a potential therapeutic target for RCC. Graphic abstract

The Role of the VEGF Family in Atherosclerosis Development and Its Potential as Treatment Targets

“…Also, in AECs and macrophages derived from HFD mice, VEGF-A splicing isoforms were shifted to pro-angiogenic VEGF165 [60]. The endogenous balance of pro/anti-angiogenic VEGF-A splice isoforms is regulated by serine/arginine-rich splicing factor protein kinase 1, which binds to the VEGF-A mRNA and produce VEGF165 [61] (Figure 4). Also, lncRNA NORAD plays an essential role in vascular endothelial cell injury and atherosclerosis development.…”

The Immunohistochemical Expression of the Serine and Arginine-Rich Splicing Factor 1 (SRSF1) Is a Predictive Factor of the Recurrence of Basal Cell Carcinoma: A Preliminary Study on a Series of 52 Cases

“…SRSF1 is a splicing factor that also plays a proto-oncogene role by stimulating angiogenesis, cell growth, and cell proliferation [21][22][23]. Its oncogenic role has been characterized in numerous human cancers [12][13][14][15][16][17][18][21][22][23]. It has been found to be downregulated in unaffected brain parenchyma, as compared to human glioblastoma tissue, where it appears to influence tumor angiogenesis by stimulating the formation of the proangiogenic form of the vascular endothelial growth factor A (VEGFA) [14].…”

“…SRSF1 also exhibits several oncogenic functions, including the stimulation of angiogenesis, cell growth, and cell proliferation [12][13][14]. It has been found to be upregulated in numerous human malignancies, such as glioblastoma and breast carcinoma, as well as lung and colorectal cancer [12][13][14][15][16]. Recently, our research group also reported the poor prognostic role of SRSF1 in adult diffuse gliomas, prostate cancer, and mesotheliomas [17,18].…”

“…The serine and arginine-rich splicing factor 1 (SRSF1) is an RNA-binding protein involved in both canonical and alternative mRNA splicing [12,13]. SRSF1 also exhibits several oncogenic functions, including the stimulation of angiogenesis, cell growth, and cell proliferation [12][13][14].…”

“…The serine and arginine-rich splicing factor 1 (SRSF1) is an RNA-binding protein involved in both canonical and alternative mRNA splicing [12,13]. SRSF1 also exhibits several oncogenic functions, including the stimulation of angiogenesis, cell growth, and cell proliferation [12][13][14]. It has been found to be upregulated in numerous human malignancies, such as glioblastoma and breast carcinoma, as well as lung and colorectal cancer [12][13][14][15][16].…”