A germline mutation in Rab43 gene identified from a cancer family predisposes to a hereditary liver-colon cancer syndrome

Large-scale omics data reveal the cooperation of mutation-circRNA-miRNA-target gene network in liver cancer oncogenesis

Aims: Clarifying the initial trigger of the differentially expressed genes in cancers helps researchers understand the cellular system as a whole network. Materials & methods: We retrieve the transcriptome and translatome of tumor and normal tissues from ten liver cancer patients and define differentially expressed genes and tumor-specific mutations. We associate the oncogenesis with the mutations by target prediction and experimental verification. Results: Upregulated genes have tumor-specific mutations in 3'UTRs that abolish the binding of miRNAs. For downregulated genes, their corresponding miRNAs are mutually targeted by two circRNAs, with mutations in base-pairing regions. Transfection experiments support the oncogenic role of these mutations. Conclusions: The tumor-specific mutations serve as the initial trigger of liver cancer. The mutation-circRNA-miRNA-target gene chain is completed.

Rab family of small GTPases: an updated view on their regulation and functions

The Rab family of small GTPases regulates intracellular membrane trafficking by orchestrating the biogenesis, transport, tethering, and fusion of membrane-bound organelles and vesicles. Like other small GTPases, Rabs cycle between two states, an active (GTP-loaded) state and an inactive (GDP-loaded) state, and their cycling is catalyzed by guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs). Because an active form of each Rab localizes on a specific organelle (or vesicle) and recruits various effector proteins to facilitate each step of membrane trafficking, knowing when and where Rabs are activated and what effectors Rabs recruit is crucial to understand their functions. Since the discovery of Rabs, they have been regarded as one of the central hubs for membrane trafficking, and numerous biochemical and genetic studies have revealed the mechanisms of Rab functions in recent years. The results of these studies have included the identification and characterization of novel GEFs, GAPs, and effectors, as well as post-translational modifications, for example, phosphorylation, of Rabs. Rab functions beyond the simple effector-recruiting model are also emerging. Furthermore, the recently developed CRISPR/Cas technology has enabled acceleration of knockout analyses in both animals and cultured cells and revealed previously unknown physiological roles of many Rabs. In this review article, we provide the most up-to-date and comprehensive lists of GEFs, GAPs, effectors, and knockout phenotypes of mammalian Rabs and discuss recent findings in regard to their regulation and functions.

Cancer-driving mutations and variants of components of the membrane trafficking core machinery

The core machinery for vesicular membrane trafficking broadly comprises of coat proteins, RABs, tethering complexes and SNAREs. As cellular membrane traffic modulates key processes of mitogenic signaling, cell migration, cell death and autophagy, its dysregulation could potentially results in increased cell proliferation and survival, or enhanced migration and invasion. Changes in the levels of some components of the core machinery of vesicular membrane trafficking, likely due to gene amplifications and/or alterations in epigenetic factors (such as DNA methylation and micro RNA) have been extensively associated with human cancers. Here, we provide an overview of association of membrane trafficking with cancer, with a focus on mutations and variants of coat proteins, RABs, tethering complex components and SNAREs that have been uncovered in human cancer cells/tissues. The major cellular and molecular cancer-driving or suppression mechanisms associated with these components of the core membrane trafficking machinery shall be discussed.

RAB43 Promotes Gastric Cancer Cell Proliferation and Metastasis via Regulating the PI3K/AKT Signaling Pathway

Background

Ras-related GTP-binding protein 43 (RAB43) plays a key part in the progression of many human cancers. However, the role and functional mechanisms of RAB43 in gastric cancer (GC) remain unknown.

Purpose

To elucidate the function and mechanism of RAB43 in the progression of GC.

Patients and Methods

One hundred patients with histologically confirmed GC were recruited for this study. Tumor samples and GC cell lines were used to detect RAB43 levels. Cell Counting Kit8 (CCK8) and colony formation assays were used to analyze cell proliferation. Cell migration and invasion ability were examined by wound healing and transwell assays. Western blot assays and quantitative real‑time PCR (qRT-PCR) were performed to examine related mRNA and protein expression. In vivo experiments were used to examine the effect of RAB43.

Results

Patients with RAB43-positive tumors had worse overall survival than patients with RAB43-negative tumors. Downregulation of RAB43 significantly inhibited cell proliferation and cell metastasis. In contrast, RAB43 overexpression promoted proliferation and metastasis in normal gastric epithelial GES‑1 cells. In vivo studies confirmed that RAB43 promoted tumor growth. In addition, the knockdown of RAB43 significantly inhibited cell proliferation and metastasis via phosphatidylinositol-3-kinases/protein-serine-threonine kinase (PI3K/AKT) pathway.

Conclusion

RAB43 promotes GC cells proliferation and migration in vivo and in vitro and probably served as a novel potential therapeutic biomarker for GC.