LncRNA PVT1 promotes bladder cancer progression by forming a positive feedback loop with STAT5B.

BACKGROUND: Plasmacytoma Variant Translocation 1 (LncRNA PVT1) and signal transducer and activator of transcription 5B (STAT5B) play important roles in various cancers, but their interaction in bladder cancer (BC) remains unclear. PURPOSE: We aimed to explore the interaction between lncRNA PVT1 and STAT5B in BC tumorigenesis and find potential drugs for BC. METHODS: The association of the expression of lncRNA PVT1 and STAT5B to the prognosis of BC patients was evaluated via bioinformatic analysis. Loss- and gain-of-function assays were performed to determine the biological functions of lncRNA PVT1 and STAT5B. Quantitative real time polymerase chain reaction, Western blot, immunohistochemistry, and immunofluorescence were used to detect lncRNA PVT1 and STAT5B expression. Fluorescence in situ hybridization, RNA pull-down and RNA immunoprecipitation assays were conducted to determine the regulatory effect of lncRNA PVT1 on STAT5B. The transcriptional effect of STAT5B on lncRNA PVT1 gene was determined using luciferase reporter assay, chromatin immunoprecipitation and DNA-affinity precipitation assays. Connectivity Map analysis was used to screen anticancer drugs. RESULTS: LncRNA PVT1 and STAT5B enhance the expression of each other and promote the malignant phenotypes in BC, including cell viability and invasion. lncRNA PVT1 stabilizes STAT5B by decreasing ubiquitination, enhances STAT5B phosphorylation, and promotes the translocation to the nucleus of STAT5B to trigger further carcinogenesis activities. In the nucleus, STAT5B activates the transcription of lncRNA PVT1 by binding directly to its promoter region, leading to a positive feedback. Tanespimycin effectively abated the oncogenic effect. CONCLUSIONS: We first identified the lncRNA PVT1/STAT5B positive feedback loop for bladder carcinogenesis, and found a potentially effective drug for BC.

Exosomes from PYCR1 knockdown bone marrow mesenchymal stem inhibits aerobic glycolysis and the growth of bladder cancer cells via regulation of the EGFR/PI3K/AKT pathway.

Bladder cancer (BC) is a heterogeneous disease, and pyrroline­5­carboxylate reductase 1 (PYCR1) can promote the proliferation and invasion of BC cells and accelerate BC progression. In the present study, si­PYCR1 was loaded into bone marrow mesenchymal stem cell (BMSC)­derived exosomes (Exos) in BC. First, PYCR1 levels in BC tissues/cells were assessed, and cell proliferation, invasion, and migration were evaluated. Aerobic glycolysis levels (glucose uptake, lactate production, ATP production, and the expression of relevant enzymes) and the EGFR/PI3K/AKT pathway phosphorylation levels were determined. PYCR1­EGFR interactions were examined by co­immunoprecipitation experiments. RT4 cells transfected with oe­PYCR1 were treated with EGFR inhibitor CL­387785. Exos were loaded with si­PYCR1 and identified, followed by an assessment of their effects on aerobic glycolysis and malignant cell behaviors. Nude mouse models of xenograft tumors were established by injecting mice with Exo­si­PYCR1 and Exo­si­PYCR1. PYCR1 was upregulated in BC cells, with the highest expression observed in T24 cells and the lowest expression in RT4 cells. Following PYCR1 knockdown, the malignant behaviors of T24 cells and aerobic glycolysis were decreased, while PYCR1 overexpression in RT4 cells averted these trends. PYCR1 interacted with EGFR, and CL­387785 inhibited the EGFR/PI3K/AKT pathway and attenuated the effects of PYCR1 overexpression on RT4 cells but had no effect on PYCR1 expression. Exo­si­PYCR1 showed stronger inhibitory effects on aerobic glycolysis and on the malignant behaviors of T24 cells than si­PYCR1. Exo­si­PYCR1 blocked xenograft tumor growth and had good biocompatibility. Briefly, PYCR1 knocking loaded by BMSC­derived Exos suppressed aerobic glycolysis and BC growth via the PI3K/AKT pathway by binding to EGFR.

SENP3 affects the expression of PYCR1 to promote bladder cancer proliferation and EMT transformation by deSUMOylation of STAT3.

Abnormal activation of signal transducer and activator of transcription 3 (STAT3) has been found in various types of human cancers, including bladder cancer (BC). In our study, we examined the regulation of STAT3 post-translational modifications (PTMs) and found that SENP3 is high in bladder cancer. Sentrin/SUMO-specific protease3 (SENP3) and STAT3 were highly expressed in BC tissues when compared with tissue adjacent to carcinoma. SENP3 induced STAT3 protein level and p-STAT3 translocating into nuclear through deSUMOylation of STAT3. Further, nuclear STAT3, as a transcriptional activity factor, promoted pyrroline-5-carboxylate reductase 1 PYCR1 gene and protein level by interacting with the promoter of (PYCR1). Next, we found that knockdown of PYCR1 inhibited Epithelial to mesenchymal transition of bladder cancer, and simultaneously mitigated the carcinogenic effects of STAT3. In vitro, STAT3 knockdown in bladder cancer cells inhibited cell proliferation, migration, and invasion. In contrast, SENP3 overexpression reversed these effects. In all, results lend novel insights into the regulation of STAT3, which has key roles in bladder cancer progression.