Rhein is a lipophilic anthraquinone extensively found in medicinal herbs. Emerging evidence suggests that rhein has significant antitumor effects, supporting its potential use as an antitumor agent. The IL6/STAT3 signaling pathway has been suggested as an attractive target for the discovery of novel cancer therapeutics. The human pancreatic cancer cell lines AsPC-1, Patu8988T, BxPC-3 and PANC-1, and immunodeficient mice were chosen as models to study the effects of rhein. The potent antiproliferative and proapoptotic effects of rhein were examined by cell viability, cellular morphology, apoptosis and colony formation assays. The STAT3 luciferase report assay, immunostaining analysis and Western blot analysis revealed the inhibition of the IL6/STAT3 signaling axis. Apoptosis was induced by adjunctive use of rhein with epidermal growth factor receptor (EGFR) inhibitors in pancreatic cancer cells as verified by cell apoptosis analysis and changes in the expression level of apoptotic/anti-apoptotic proteins BCL-2, BAX, Caspase 3 and Cl-PARP. Suppression of the phosphorylation of STAT3 and EGFR were also observed as a result of the treatment with a combination of rhein and EGFR inhibitors. Most interestingly, it was found that rhein considerably sensitized cells to erlotinib, thus suppressing tumor growth in PANC-1 and BxPC-3 xenograft models. The in vivo anti-tumor effect was associated with increased apoptosis and combined inhibition of the STAT3 and EGFR pathways in tumor remnants. Rhein sensitizes human pancreatic cancer cells to EGFR inhibitors through inhibition of STAT3. Taken together, the results indicate that rhein offers a novel blueprint for pancreatic cancer therapy, particularly when combined with EGFR inhibitors.

Signal transducer and activator of transcription 3 (STAT3) is an oncogene, which upregulates in approximately 70% of human cancers. Autophagy is an evolutionarily conserved process which maintains cellular homeostasis and eliminates damaged cellular components. Moreover, the STAT3 signaling pathway, which may be triggered by cancer cells, has been implicated in the autophagic process. In this study, we found that the anthelmintic flubendazole exerts potent antitumor activity in three human colorectal cancer (CRC) cell lines and in the nude mouse model. The inhibition of cell proliferation in vitro by flubendazole was evaluated using a clonogenic assay and the MTT assay. Western blot analysis, flow cytometry analysis, siRNA growth experiment and cytoplasmic and nuclear protein extraction were used to investigate the mechanisms of inhibiting STAT3 signaling and activation of autophagy induced by flubendazole. Additionally, the expression of STAT3 and mTOR was analyzed in paired colorectal cancer and normal tissues collected from clinical patients. Flubendazole blocked the IL6-induced nuclear translocation of STAT3, which led to inhibition of the transcription of STAT3 target genes, such as MCL1, VEGF and BIRC5. In addition, flubendazole also reduced the expression of P-mTOR, P62, BCL2, and upregulated Beclin1 and LC3-I/II, which are major autophagy-related genes. These processes induced potent cell apoptosis in CRC cells. In addition, flubendazole displayed a synergistic effect with the chemotherapeutic agent 5-fluorouracil in the treatment of CRC. Taken together, these results indicate that flubendazole exerts antitumor activities by blocking STAT3 signaling and inevitably affects the autophagy pathway. Flubendazole maybe a novel anticancer drug and offers a distinctive therapeutic strategy in neoadjuvant chemotherapy of CRC.

The balance of ubiquitination and deubiquitination plays diverse roles in regulating protein stability and cellular homeostasis. Deubiquitinating enzymes catalyze the hydrolysis and removal of ubiquitin chains from target proteins and play critical roles in various disease processes, including cancer, immune responses to viral infections and neurodegeneration. This article aims to summarize roles of the deubiquitinating enzyme ubiquitin-specific protease 25 (USP25) in disease onset and progression. Previous studies have focused on the role of USP25 in antiviral immunity and neurodegenerative diseases. Recently, however, as the structural similarities and differences between USP25 and its homolog USP28 have become clear, mechanisms of action of USP25 in cancer and other diseases have been gradually revealed.

Introduction: This study is aimed to explore the effects of Adenosine A2a receptors (A2aR) on hypoxia-induced pulmonary hypertension (HPH) via mitochondrial ATP-sensitive potassium channels (MitoKATP) in vivo and in vitro.Material and methods: Using wild-type (WT) and A2aR-deficient (A2aR-/-) mice; hypoxic pulmonary artery smooth muscle cells (PASMCs) were induced by a 24-hours hypoxia exposure. Mice and PASMCs were treated with the A2aR agonist CGS21680, MitoKATP blocker 5-hydroxydecanoic acid sodium salt (5HD), or MitoKATP agonist diazoxide. Mitochondrial morphology was observed by electron microscopy. The mitochondrial membrane potential (Δψm); invasive hemodynamic parameters; right ventricular (RV) hypertrophy index; pulmonary arterial remodeling index; proliferative and apoptotic indexes; protein expression levels of A2aR, Bax, Bcl-2, and Caspase-9; and release of cytochrome C from the mitochondria to the cytoplasm were measured.Results: In vitro, hypoxia induced the opening of MitoKATP. The up-regulation of A2aR reduced the opening of MitoKATP, and the blocking of MitoKATP or activating A2aR promoted mitochondria-dependent apoptosis of PASMCs. In vivo, compared with WT mice, A2aR-/- mice displayed increased RV systolic pressure, RV hypertrophy index, and pulmonary arterial remodeling index. The expression levels of Bax, cytochrome C, and Caspase-9 were higher and Bcl-2 expression was lower in A2aR-/- mice than in WT mice. CGS21680 could reverse hypoxia-induced hemodynamic changes, RV hypertrophy, and pulmonary arterial remodeling as well as abnormal proliferation and apoptosis resistance in WT mice with pulmonary hypertension (PH).Conclusions: A2aR induced the mitochondrial-dependent apoptosis pathway and inhibited PASMC proliferation by blocking MitoKATP, thereby inhibiting pulmonary vascular structural remodeling and reducing PH.