Down-regulation of USP22 reduces cell stemness and enhances the sensitivity of pancreatic cancer cells to cisplatin by inactivating the Wnt/β-catenin pathway

Fundamental insights and molecular interactions in pancreatic cancer: Pathways to therapeutic approaches

The gastrointestinal tract can be affected by a number of diseases that pancreatic cancer (PC) is a malignant manifestation of them. The prognosis of PC patients is unfavorable and because of their diagnosis at advanced stage, the treatment of this tumor is problematic. Owing to low survival rate, there is much interest towards understanding the molecular profile of PC in an attempt in developing more effective therapeutics. The conventional therapeutics for PC include surgery, chemotherapy and radiotherapy as well as emerging immunotherapy. However, PC is still incurable and more effort should be performed. The molecular landscape of PC is an underlying factor involved in increase in progression of tumor cells. In the presence review, the newest advances in understanding the molecular and biological events in PC are discussed. The dysregulation of molecular pathways including AMPK, MAPK, STAT3, Wnt/β-catenin and non-coding RNA transcripts has been suggested as a factor in development of tumorigenesis in PC. Moreover, cell death mechanisms such as apoptosis, autophagy, ferroptosis and necroptosis demonstrate abnormal levels. The EMT and glycolysis in PC cells enhance to ensure their metastasis and proliferation. Furthermore, such abnormal changes have been used to develop corresponding pharmacological and nanotechnological therapeutics for PC.

RNF220 promotes gastric cancer growth and stemness via modulating the USP22/wnt/β-catenin pathway

Gastric cancer (GC) is a prevalent malignancy that seriously threatens the health and life of patients. Although Ring finger 220 (RNF220) has been demonstrated to participate in the development of various cancers, its role and mechanism in GC remain undiscovered. The expression of RNF220 was determined by The Cancer Genome Atlas (TCGA) database and Western blot. Additionally, the overall survival (OS) and post-progression survival (PPS) were analyzed based on the levels of RNF220 in the TCGA database. The role and mechanism of RNF220 in growth and stemness were investigated using cell counting kit-8, colony formation, sphere-formation, co-immunoprecipitation, and Western blot experiments. Furthermore, the role of RNF220 was investigated in a xenografted mouse model. The expression of RNF220 was found to be upregulated in GC, which predicted unfavorable OS and PPS in patients with GC. Knockdown of RNF220 reduced cell viability, colony numbers, numbers of spheres formation, and the relative protein levels of Nanog, Sox2, and Oct4 in both AGS and MKN-45 cells. Moreover, overexpression of RNF220 increased cell viability and the numbers of spheres formation in MKN-45 cells. Mechanistically, RNF220 bound to USP22, and interference of RNF220 downregulated the Wnt/β-catenin axis via USP22, which was confirmed by the overexpression of USP22 in both cell lines. Furthermore, silencing of RNF220 significantly decreased tumor volume and weight, the level of Ki-67, and the relative protein levels of USP22, β-catenin, c-myc, Nanog, Sox2, and Oct4. Taken together, downregulation of RNF220 suppressed GC cell growth and stemness by downregulating the USP22/Wnt/β-catenin axis.

Non-coding RNA-based therapeutics in cancer therapy: An emphasis on Wnt/β-catenin control

Non-coding RNA transcripts are RNA molecules that have mainly regulatory functions and they do not encode proteins. microRNAs (miRNAs), lncRNAs and circRNAs are major types of this family and these epigenetic factors participate in disease pathogenesis, especially cancer that their abnormal expression may lead to cancer progression. miRNAs and lncRNAs possess a linear structure, whereas circRNAs possess ring structures and high stability. Wnt/β-catenin is an important factor in cancer with oncogenic function and it can increase growth, invasion and therapy resistance in tumors. Wnt upregulation occurs upon transfer of β-catenin to nucleus. Interaction of ncRNAs with Wnt/β-catenin signaling can determine tumorigenesis. Wnt upregulation is observed in cancers and miRNAs are able to bind to 3'-UTR of Wnt to reduce its level. LncRNAs can directly/indirectly regulate Wnt and in indirect manner, lncRNAs sponge miRNAs. CircRNAs are new emerging regulators of Wnt and by its stimulation, they increase tumor progression. CircRNA/miRNA axis can affect Wnt and carcinogenesis. Overall, interaction of ncRNAs with Wnt can determine proliferation rate, migration ability and therapy response of cancers. Furthermore, ncRNA/Wnt/β-catenin axis can be utilized as biomarker in cancer and for prognostic applications in patients.

Histone Modifications Represent a Key Epigenetic Feature of Epithelial-to-Mesenchyme Transition in Pancreatic Cancer

Pancreatic cancer is one of the most lethal malignant diseases due to its high invasiveness, early metastatic properties, rapid disease progression, and typically late diagnosis. Notably, the capacity for pancreatic cancer cells to undergo epithelial-mesenchymal transition (EMT) is key to their tumorigenic and metastatic potential, and is a feature that can explain the therapeutic resistance of such cancers to treatment. Epigenetic modifications are a central molecular feature of EMT, for which histone modifications are most prevalent. The modification of histones is a dynamic process typically carried out by pairs of reverse catalytic enzymes, and the functions of these enzymes are increasingly relevant to our improved understanding of cancer. In this review, we discuss the mechanisms through which histone-modifying enzymes regulate EMT in pancreatic cancer.

Protein degradation: expanding the toolbox to restrain cancer drug resistance

Despite significant progress in clinical management, drug resistance remains a major obstacle. Recent research based on protein degradation to restrain drug resistance has attracted wide attention, and several therapeutic strategies such as inhibition of proteasome with bortezomib and proteolysis-targeting chimeric have been developed. Compared with intervention at the transcriptional level, targeting the degradation process seems to be a more rapid and direct strategy. Proteasomal proteolysis and lysosomal proteolysis are the most critical quality control systems responsible for the degradation of proteins or organelles. Although proteasomal and lysosomal inhibitors (e.g., bortezomib and chloroquine) have achieved certain improvements in some clinical application scenarios, their routine application in practice is still a long way off, which is due to the lack of precise targeting capabilities and inevitable side effects. In-depth studies on the regulatory mechanism of critical protein degradation regulators, including E3 ubiquitin ligases, deubiquitylating enzymes (DUBs), and chaperones, are expected to provide precise clues for developing targeting strategies and reducing side effects. Here, we discuss the underlying mechanisms of protein degradation in regulating drug efflux, drug metabolism, DNA repair, drug target alteration, downstream bypass signaling, sustaining of stemness, and tumor microenvironment remodeling to delineate the functional roles of protein degradation in drug resistance. We also highlight specific E3 ligases, DUBs, and chaperones, discussing possible strategies modulating protein degradation to target cancer drug resistance. A systematic summary of the molecular basis by which protein degradation regulates tumor drug resistance will help facilitate the development of appropriate clinical strategies.