The overexpression of Rab9 promotes tumor progression regulated by XBP1 in breast cancer

The Role of Rab GTPases in the development of genetic and malignant diseases

Small GTPases have been shown to play an important role in several cellular functions, including cytoskeletal remodeling, cell polarity, intracellular trafficking, cell-cycle, progression and lipid transformation. The Ras-associated binding (Rab) family of GTPases constitutes the largest family of GTPases and consists of almost 70 known members of small GTPases in humans, which are known to play an important role in the regulation of intracellular membrane trafficking, membrane identity, vesicle budding, uncoating, motility and fusion of membranes. Mutations in Rab genes can cause a wide range of inherited genetic diseases, ranging from neurodegenerative diseases, such as Parkinson's disease (PD) and Alzheimer's disease (AD) to immune dysregulation/deficiency syndromes, like Griscelli Syndrome Type II (GS-II) and hemophagocytic lymphohistiocytosis (HLH), as well as a variety of cancers. Here, we provide an extended overview of human Rabs, discussing their function and diseases related to Rabs and Rab effectors, as well as focusing on effects of (aberrant) Rab expression. We aim to underline their importance in health and the development of genetic and malignant diseases by assessing their role in cellular structure, regulation, function and biology and discuss the possible use of stem cell gene therapy, as well as targeting of Rabs in order to treat malignancies, but also to monitor recurrence of cancer and metastasis through the use of Rabs as biomarkers. Future research should shed further light on the roles of Rabs in the development of multifactorial diseases, such as diabetes and assess Rabs as a possible treatment target.

Spliced or Unspliced, That Is the Question: The Biological Roles of XBP1 Isoforms in Pathophysiology

X-box binding protein 1 (XBP1) is a member of the CREB/ATF basic region leucine zipper family transcribed as the unspliced isoform (XBP1-u), which, upon exposure to endoplasmic reticulum stress, is spliced into its spliced isoform (XBP1-s). XBP1-s interacts with the cAMP response element of major histocompatibility complex class II gene and plays critical role in unfolded protein response (UPR) by regulating the transcriptional activity of genes involved in UPR. XBP1-s is also involved in other physiological pathways, including lipid metabolism, insulin metabolism, and differentiation of immune cells. Its aberrant expression is closely related to inflammation, neurodegenerative disease, viral infection, and is crucial for promoting tumor progression and drug resistance. Meanwhile, recent studies reported that the function of XBP1-u has been underestimated, as it is not merely a precursor of XBP1-s. Instead, XBP-1u is a critical factor involved in various biological pathways including autophagy and tumorigenesis through post-translational regulation. Herein, we summarize recent research on the biological functions of both XBP1-u and XBP1-s, as well as their relation to diseases.

MiRNA-136-5p Sensitizes Liver Cancer Cells to Docetaxel by Targeting P53 and Enhances Cell Migration

We aimed to explore whether microRNA (miRNA)-136-5p modulates P53 expression, and affects the efficacy of docetaxel treatment for liver cancer. miRNA array screened the differentially expressed miRNAs in biopsy tissues of liver cancer patients, and the expression of miR-136-5p and P53 in tissues and cells by RT-PCR. Following docetaxel treatment, through increased- and decreased-function method, we detected the impact of the miRNA on cell progression, as well as the sensitivity of docetaxel through MTT assay and colony formation experiment. The correlation between miR-136-5p and P53 was evaluated. The expression of miR-136-5p in liver cancer cells is up-regulated, which is consistent with the results of bioinformatics analysis. Further, miR-136-5p overexpression promoted cell proliferation and migration, and sensitized liver cancer cells to docetaxel. Interestingly, P53 was indicated to bind to miR-136-5p, and P53 participated in the up-regulation of MMP10 induced by miR-136-5p. miR-136-5p enhances the sensitivity to docetaxel in liver cancer and thus could be a biomarker for the treatment against liver cancer.

Nde1 is a Rab9 effector for loading late endosomes to cytoplasmic dynein motor complex

Rab9 is mainly located on late endosomes and required for their intracellular transport to trans-Golgi network (TGN). The cytoplasmic dynein motor, together with its regulatory proteins Nde1/Ndel1 and Lis1, controls intracellular retrograde transport of membranous organelles along the microtubule network. How late endosomes are tethered to the microtubule-based motor dynein for their retrograde transport remains unclear. Here, we demonstrate that the guanosine triphosphate (GTP)-bound Rab9A/B specifically uses Nde1/Ndel1 as an effector to interact with the dynein motor complex. We determined the crystal structure of Rab9A-GTP in complex with the Rab9-binding region of Nde1. The functional roles of key residues involved in the Rab9A-Nde1 interaction are verified using biochemical and cell biology assays. Rab9A mutants unable to bind to Nde1 also failed to associate with dynein, Lis1, and dynactin. Therefore, Nde1 is a Rab9 effector that tethers Rab9-associated late endosomes to the dynein motor for their retrograde transport to the TGN.

Circular RNA circSIPA1L1 Contributes to Osteosarcoma Progression Through the miR-411-5p/RAB9A Signaling Pathway

Recently, various studies have identified circular RNAs (circRNAs) to play a significant role in tumorigenesis, thereby showing potential as novel tumor biomarkers. circSIPA1L1 is a newly discoveredcircular RNA, which is formed by back-splicing of SIPA1L1 and is found increased in osteosarcoma (OS). Nevertheless, the specific functions of circSIPA1L1 in OS remain unknown. In the present study, circSIPA1L1 was obtained from a previously reported circRNA microarray in the GEO database (GSE96964). Quantitative real-time polymerase chain reaction (qRT-PCR) was employed to assess the mRNA level of circSIPA1L1 in OS cell lines and tissue samples. Bioinformatics analysis, luciferase reporter assays, real-time PCR, RNA pull-down assays and RNA immunoprecipitation (RIP) were employed to verify the binding of circSIPA1L1 with miR-411-5p. Xenograft tumor models were established to identify the role of circSIPA1L1 in vivo. A series of in vitro experiments, such as western blotting, colony formation, transwell assays and anoikis assay were employed to confirm the relationship across circSIPA1L1, miR-411-5p, and RAB9A. Our study confirmed circSIPA1L1 to be upregulated in both human OS samples and OS cell lines. Mechanistically, circSIPA1L1 could serve as a miR-411-5p molecular sponge to increase RAB9A expression, which was confirmed to be a tumor promoter mediating carcinogenesis. Silencing of circSIPA1L1 attenuated the vitality, invasion, migration and proliferation of OS cell lines both in vivo and in vitro. miR-411-5p inhibition or RAB9A overexpression reversed the anti-tumor effects caused by circSIPA1L1 knockdown. Briefly, circSIPA1L1 could function as a driver gene in OS and initiate OS tumorigenesis through the miR-411-5p/RAB9A signaling pathway, which might become a potential therapeutic biomarker for OS treatment.

Rab9 defense against white spot syndrome virus by participation in autophagy in Marsupenaeus japonicas

White spot syndrome virus (WSSV) is the main pathogen of shrimp and has led to considerable economic losses to the shrimp industry around the world. However, so far there are still no effective strategies to address this problem. In this paper, the tissue distribution of Rab9 as well as its defense mechanism against WSSV in Japanese shrimp (Marsupenaeus japonicas) was investigated. The results revealed that Rab9 had a higher expression in hemocyte and gill while expression was lower in heart, muscle, intestine, liver, indicating Rab9 was involved in the innate immune process. The results showed that the Rab9 expression increased when shrimp was challenged with WSSV compared with that of control, while the silence of Rab9 led to the increase of WSSV copies. In order to explore the antiviral mechanism of Rab9, it was demonstrated that the expression level of Rab9 changed during autophagy process, which indicated that Rab9 is participated in the autophagy procedure of shrimp. The fact that autophagy decreased after Rab9 silenced, may also suggest that Rab9 protein could affect autophagy. In short, the results showed Rab9 played a key role in antivirus through regulating autophagy. The results not only enlarge the limited views about molecular mechanism of Rab in invertebrate, but also help to enrich the immunological content in marine invertebrate.

RAB9A Plays an Oncogenic Role in Human Liver Cancer Cells

Background

RAB9, as a member of the Rab GTPase family, is required for the transport of the mannose-6-phosphate receptor (MPR) from late endosomes to trans-Golgi network (TGN). However, the role of RAB9A in tumors, including liver cancer, is still unknown.

Methods

We used pcDNA3.1 plasmid to upregulate the expression of RAB9A in Hep3b cells and used specific shRNA to downregulate the expression of RAB9A in HepG2 cells. Biological functions of RAB9A were performed by CCK-8 assay, colony formation assay, apoptosis analysis, transwell assays, and wound healing assays. Finally, an in-depth mechanism study was performed by western blot.

Results

RAB9A promoted the proliferation and clonality of Hep3b and HepG2 cells. RAB9A also inhibited apoptosis and the activation of mitochondrial apoptotic pathway. In addition, RAB9A promoted the invasion and migration of Hep3b and HepG2 cells. Importantly, RAB9A activated the AKT/mTOR signaling pathway in human liver cancer cells. A double-effect inhibitor (BEZ235) significantly hindered the effect of RAB9A overexpression on the proliferation and invasion of Hep3b cells.

Conclusion

Our data suggest that RAB9A plays a carcinogenic role in human liver cancer progression partially through AKT signaling pathways, suggesting that RAB9A may serve as a potential therapeutic target for liver cancer therapy.

The emerging role of XBP1 in cancer

X-box binding protein 1 (XBP1) is a unique basic-region leucine zipper (bZIP) transcription factor whose dynamic form is controlled by an alternative splicing response upon disturbance of homeostasis in the endoplasmic reticulum (ER) and activation of the unfolded protein response (UPR). XBP1 was first distinguished as a key regulator of major histocompatibility complex (MHC) class II gene expression in B cells. XBP1 communicates with the foremost conserved signalling component of the UPR and is essential for cell fate determination in response to ER stress (ERS). Here, we review recent advances in our understanding of this multifaceted translation component in cancer. In this review, we briefly discuss the role of XBP1 mediators in the UPR and the transcriptional function of XBP1. In addition, we describe how XBP1 operates as a key factor in tumour progression and metastasis. We mainly review XBP1's expression, function and prognostic value in research on solid tumours. Finally, we discuss multiple approaches, especially those involving XBP1, that overcome the immunosuppressive effect of the UPR in cancer that could potentially be useful as antitumour therapies.

FOXO3/TRIM22 axis abated the antitumor effect of gemcitabine in non-small cell lung cancer via autophagy induction

Background

Non-small cell lung cancer (NSCLC) accounts for more than 80% of the total lung cancer and gemcitabine (GEM)-based chemotherapy is the first-line therapeutic approach for NSCLC treatment. Owing to acquired chemo-resistance, the prognosis of NSCLC patients receiving GEM treatment is still poor.

Methods

Dysregulation of mRNAs in GEM-resistant (GR) NSCLC cells comparing to parental cells were profiled by analyzing GSEA6914 datasets from GEO database. Additionally, qRT-PCR were performed on clinically collected patient serum samples and transplanted tumor tissues and GEM-resistant (GR)/sensitive (GS) cell lines. In order to explore the functional role of tripartite motif protein 22 (TRIM22), gain and loss-of-function cell models were constructed in A549 and A549/GR respectively. MTT and Annexin V-FITC/propidium iodide (PI) staining assay were carried out to access the response to GEM of A549 and A549/GR cells. Observation of RFP-LC3 puncta and western blot detection of autophagy markers were used to evaluate autophagy. Bi-luciferase reporter assay was used to confirm the transcriptional regulatory relationship. Rescue experiments were carried out to confirm the FOXO3/TRIM22 regulatory axis in GEM susceptibility.

Results

TRIM22 was significantly upregulated in GR patient serum samples, transplanted tumor tissues and NSCLC cells which was negatively transcriptional regulated by FOXO3. TRIM22 overexpression attenuated the sensitivity of A549 to GEM and its depletion promoted the sensitivity of A549/GR to GEM. Additionally, TRIM22 promoted GEM-induced pro-survival autophagy to protected NSCLC cells from apoptosis.

Conclusions

TRIM22 was significantly upregulated in GR lung adenocarcinoma cell line A549 which is negatively transcriptional regulated by FOXO3. Due to the enhancement of pro-survival autophagy induced by TRIM22, the A549 cells became less sensitive to GEM. This study may provide a basis for screening target of liquid biopsy for predicting GEM sensitivity in NSCLC.

Rab GTPases: Emerging Oncogenes and Tumor Suppressive Regulators for the Editing of Survival Pathways in Cancer

The Rab GTPase family of proteins are mediators of membrane trafficking, conferring identity to the cell membranes. Recently, Rab and Rab-associated factors have been recognized as major regulators of the intracellular positioning and activity of signaling pathways regulating cell growth, survival and programmed cell death or apoptosis. Membrane trafficking mediated by Rab proteins is controlled by intracellular localization of Rab proteins, Rab-membrane interactions and GTP-activation processes. Aberrant expression of Rab proteins has been reported in multiple cancers such as lung, brain and breast malignancies. Mutations in Rab-coding genes and/or post-translational modifications in their protein products disrupt the cellular vesicle trafficking network modulating tumorigenic potential, cellular migration and metastatic behavior. Conversely, Rabs also act as tumor suppressive factors inducing apoptosis and inhibiting angiogenesis. Deconstructing the signaling mechanisms modulated by Rab proteins during apoptosis could unveil underlying molecular mechanisms that may be exploited therapeutically to selectively target malignant cells.

Knockdown of Rab9 Suppresses the Progression of Gastric Cancer Through Regulation of Akt Signaling Pathway

Rabs have been reported to be involved in the carcinogenesis process and in the progression of cancer. However, it is unclear whether or not Rab9 is associated with the development of cancer. In the present study, we aimed to investigate the role of Rab9 in the biological functions of gastric cancer cells. The gastric cancer cell lines AGS and MKN45 were transfected with siRNA-Rab9 to block the expression of Rab9. The cell viability, proliferation, migration, invasion, and apoptosis were examined using Cell Count Kit-8, colony formation, wound healing, Transwell, and flow cytometry assays, respectively. Our data showed that silencing of Rab9 significantly inhibited the viability, proliferation, migration, and invasion abilities of AGS and MKN45 cells. Moreover, transfection with siRab9 promoted the rate of apoptosis in AGS and MKN45 cells through regulating the Bcl-2-Bax axis and the Caspase cascade. We also found that silencing of Rab9 inhibited activation of the Akt signaling pathway by downregulating the phosphorylation level of Akt. In conclusion, our data suggest that Rab9 plays an oncogenic role in the progression of gastric cancer, providing a potential target for the treatment of gastric cancer.