Fig 2: BAP1 suppresses PI3K‐Akt pathway by stabilizing PTEN. (A) The differentially expressed genes (fold change: 2, adjusted P‐value: 0.05) from GEO dataset (accession ID: GSE23035) were subjected to KEGG pathway enrichment analysis by DAVID. (B) The protein levels of BAP1 in cancer cell lines P69, M12, DU145, BPH1, PC3, and HeLa were analyzed by western blotting. (C) Western blotting analysis for endogenous PTEN and p‐Akt (Ser473) in HeLa cells transfected with HA‐BAP1WT or HA‐BAP1C91S. PTEN bands were quantified by ImageJ software. (D) Western blotting analysis for endogenous PTEN, BAP1, and p‐Akt (Ser473) in DU145 and HeLa stable cells with BAP1 knockdown. (E) Western blotting analysis for endogenous PTEN and BAP1 in the indicated PCa stable cell lines. (F) The mRNA levels of PTEN in HeLa cells transfected with BAP1WT or BAP1C91S were analyzed by qRT–PCR. (G) The mRNA levels of PTEN in U2OS cells from GEO database (GSE23035) were analyzed by Limma package. (H, I) The half‐life of endogenous PTEN protein was determined in BAP1 overexpressed HeLa cells (H) and BAP1‐knockdown DU145 cells (I) with treatment of CHX (100 μg·mL−1) for the indicated time points. The asterisk indicated nonspecific band. All above experiments were repeated at least 3 times, and representative images were shown.

Fig 3: BAP1 deubiquitinates PTEN. (A) Lysates from 293T cells transfected with Flag‐PTEN, Myc‐Ubiquitin together with an increasing amount of BAP1 were immunoprecipitated with anti‐Flag antibody, and followed by western blotting analysis with anti‐Myc antibody. (B) Lysates from 293T cells transfected with Flag‐PTEN, Myc‐Ubiquitin together with BAP1WT or mutant BAP1C91S were immunoprecipitated with anti‐Flag antibody under denaturing condition, and followed by western blotting analysis with anti‐Myc antibody. (C) Lysates from HeLa cells transfected with wild‐type BAP1 or mutant BAP1C91S were immunoprecipitated with anti‐PTEN antibody, and followed by western blotting analysis with anti‐ubiquitin antibody. (D‐E) Lysates from 293T cells transfected with Flag‐PTEN, Myc‐Ubiquitin together with full‐length HA‐BAP1, truncated HA‐BAP11‐240 (D) or HA‐BAP1ΔNLS (E) were immunoprecipitated with anti‐Flag antibody under denaturing condition, and followed by western blotting analysis with anti‐Myc antibody. (F) Ubiquitinated PTEN was purified from 293T cells transfected with Flag‐PTEN and Myc‐Ubiquitin, and then incubated with purified GST‐BAP1 from E. coli. PTEN ubiquitination level was detected by western blotting with anti‐Myc antibody. All above experiments were repeated at least 3 times.

Fig 4: Evaluation of the effect on AP cell growth inhibition and the underlying mechanisms by MTT assay and cell cycle determination, respectively. (A) Results of the MTT assay showed that the AP-AR42J cells transfected with PTEN displayed the lowest cell viability, indicating that overexpression of PTEN could inhibit the proliferation of AP-AR42J cells. (B) Quantitative analysis of the ability of PTEN inhibited proliferation of AP-AR42J cells. (C) Cell cycles of AP-AR42J cells post transfected with various genes (including scramble-shRNA, PTEN-shRNA, pCDH, and PTEN RNA) confirmed that PTEN inhibited the growth of APAR42J cells mainly by blocking the G1 phase of cells. The experiments above were repeated three times. *P < 0.05 versus pCDH.

Fig 5: Effect of SCU on PTEN expression in HepG2 cells. (a) SCU induces PTEN protein level in HepG2 cells. Cells were treated with SCU (0, 25, 50, and 100 μM) for 48 h. (b) Effect of PTEN inhibitor and SCU-induced PTEN level in HepG2 cells. Cells were treated with or without 80 μM of PTEN inhibitor: SF1670 and 100 μM of SCU for 48 h. (c) Representative immunofluorescence image images of expression of PTEN were evaluated at 0 and 100 μM (scale bars = 100 μm). The results obtained from three independent experiments were expressed as mean ± standard deviation (SD) compared with the control group. * p < 0.05.