Expression analysis and implication of Rab1A in gastrointestinal relevant tumor

Role of the Mosaic Cisternal Maturation Machinery in Glycan Synthesis and Oncogenesis

Tumorigenesis is associated with the deregulation of multiple processes, among which the glycosylation of lipids and proteins is one of the most extensively affected. However, in most cases, it remains unclear whether aberrant glycosylation is a cause, a link in the pathogenetic chain, or a mere consequence of tumorigenesis. In other cases, instead, studies have shown that aberrant glycans can promote oncogenesis. To comprehend how aberrant glycans are generated it is necessary to clarify the underlying mechanisms of glycan synthesis at the Golgi apparatus, which are still poorly understood. Important factors that determine the glycosylation potential of the Golgi apparatus are the levels and intra-Golgi localization of the glycosylation enzymes. These factors are regulated by the process of cisternal maturation which transports the cargoes through the Golgi apparatus while retaining the glycosylation enzymes in the organelle. This mechanism has till now been considered a single, house-keeping and constitutive function. Instead, we here propose that it is a mosaic of pathways, each controlling specific set of functionally related glycosylation enzymes. This changes the conception of cisternal maturation from a constitutive to a highly regulated function. In this new light, we discuss potential new groups oncogenes among the cisternal maturation machinery that can contribute to aberrant glycosylation observed in cancer cells. Further, we also discuss the prospects of novel anticancer treatments targeting the intra-Golgi trafficking process, particularly the cisternal maturation mechanism, to control/inhibit the production of pro-tumorigenic glycans.

Mycobacterium tuberculosis PE_PGRS20 and PE_PGRS47 Proteins Inhibit Autophagy by Interaction with Rab1A

Autophagy is a fundamental cellular process that has important roles in innate and adaptive immunity against a broad range of microbes. Many pathogenic microbes have evolved mechanisms to evade or exploit autophagy. It has been previously demonstrated that induction of autophagy can suppress the intracellular survival of mycobacteria, and several PE_PGRS family proteins of Mycobacterium tuberculosis have been proposed to act as inhibitors of autophagy to promote mycobacterial survival. However, the mechanisms by which these effectors inhibit autophagy have not been defined. Here, we report detailed studies of M. tuberculosis deletion mutants of two genes, pe_pgrs20 and pe_pgrs47, that we previously reported as having a role in preventing autophagy of infected host cells. These mutants resulted in increased autophagy and reduced intracellular survival of M. tuberculosis in macrophages. This phenotype was accompanied by increased cytokine production and antigen presentation by infected cells. We further demonstrated that autophagy inhibition by PE_PGRS20 and PE_PGRS47 resulted from canonical autophagy rather than autophagy flux inhibition. Using macrophages transfected to express PE_PGRS20 or PE_PGRS47, we showed that these proteins inhibited autophagy initiation directly by interacting with Ras-related protein Rab1A. Silencing of Rab1A in mammalian cells rescued the survival defects of the pe_pgrs20 and pe_pgrs47 deletion mutant strains and reduced cytokine secretion. To our knowledge, this is the first study to identify mycobacterial effectors that directly interact with host proteins responsible for autophagy initiation.

IMPORTANCE Tuberculosis is a significant global infectious disease caused by infection of the lungs with Mycobacterium tuberculosis, which then resides and replicates mainly within host phagocytic cells. Autophagy is a complex host cellular process that helps control intracellular infections and enhance innate and adaptive immune responses. During coevolution with humans, M. tuberculosis has acquired various mechanisms to inhibit host cellular processes, including autophagy. We identified two related M. tuberculosis proteins, PE_PGRS20 and PE_PGRS47, as the first reported examples of specific mycobacterial effectors interfering with the initiation stage of autophagy. Autophagy regulation by these PE_PGRS proteins leads to increased bacterial survival in phagocytic cells and increased autophagic degradation of mycobacterial antigens to stimulate adaptive immune responses. A better understanding of how M. tuberculosis regulates autophagy in host cells could facilitate the design of new and more effective therapeutics or vaccines against tuberculosis.

RAB1A regulates glioma cellular proliferation and invasion via the mTOR signaling pathway and epithelial-mesenchymal transition

Aim: We aimed at investigating the mechanism of RAB1A proliferation and invasion in gliomas. Materials & methods: Genome-wide expression profile data and immunohistochemistry were analyzed to assess RAB1A expression in gliomas. The Transwell assay, wound healing assay, brain slice coculture model, cellular fluorescence and intracranial xenograft model of nude mice were used to determine the proliferation and invasion of glioma cells. Results & conclusion: RAB1A was highly expressed in gliomas compared with normal brain tissue. The overall survival time of glioma patients with high RAB1A expression was significantly shortened. RAB1A regulated the activity of RAC1 by inhibiting the mTOR signaling pathway, affecting actin polymerization, cell morphology and cell polarity. RAB1A downregulation inhibited the epithelial-mesenchymal transition, proliferation and invasion of glioma cells.

Loss of DAB2IP Contributes to Cell Proliferation and Cisplatin Resistance in Gastric Cancer

Objective

Resistance to chemotherapeutic drugs, such as cisplatin, has been one of the major problems adversely affecting the clinical prognosis of patients with gastric cancer (GC). Disabled Homolog 2-Interacting Protein (DAB2IP) status is one of the major factors involved in sensitivity to chemotherapy in multiple cancer types. In the present study, we aimed to investigate the potential roles of DAB2IP in GC cell proliferation and cisplatin resistance.

Materials and Methods

DAB2IP expression was detected in human GC tissues using immunohistochemistry (IHC). The role of DAB2IP in regulating GC cell proliferation and cisplatin resistance was explored by genetic manipulation. Western blot analysis was used to determine the molecular signaling to explain the mechanism of the observed DAB2IP effects in GC.

Results

DAB2IP expression was downregulated in human GC tissues and low DAB2IP expression predicted poor prognosis. Moreover, our data provided evidence that DAB2IP upregulation impaired cell proliferation property and sensitized GC cells to cisplatin while DAB2IP depletion possessed the opposite effects. Mechanistically, we showed that DAB2IP could inhibit the phosphorylation and activation of protein kinase B (AKT) and extracellular signal-regulated kinase (ERK), and the enhanced proliferation ability induced by DAB2IP knockdown was greatly impaired after incubation with AKT or ERK inhibitor.

Conclusion

DAB2IP modulates GC cell proliferation and sensitivity to cisplatin potentially via regulation of AKT and ERK signaling pathway, indicating that DAB2IP may serve as a potential prognostic biomarker and therapeutic target for treatment of GC.

Clinical value and potential association of Rab1A and FoxM1 aberrant expression in colorectal cancer

Colorectal carcinoma (CRC) is one of the most common malignancies with a dismal 5-year survival rate. Our recent study indicated that Rab1A expression was closely related to GLI1 expression. A previous study shows that aberrant overexpression of GLI1 promotes colorectal cancer metastasis via FoxM1 overexpression. However, the potential correlation between Rab1A and FoxM1 in CRC remains elusive. Immunohistochemistry was performed to investigate the association of the expression of Rab1A and FoxM1 and to determine the prognosis in 135 CRC tissue and adjacent normal tissues. Using Oncomine datasets, we found that Rab1A and FoxM1 mRNA were obviously upregulated in CRC tissues compared to normal tissues. Additionally, the expression of Rab1A and FoxM1 was significantly higher in CRC tissues than that in normal tissues. Rab1A expression was positively correlated with FoxM1 expression in CRC, especially in TNM stage III. In addition, Rab1A and FoxM1 overexpression was found to be significantly correlated with poor prognosis in CRC patients. Besides, both high expression of Rab1A and FoxM1 led to a worse prognosis than anyone low group, and both low expression of Rab1A and FoxM1 had a better prognosis than the anyone low group. Therefore, Rab1A and FoxM1 play crucial roles and could be used as clinical biomarkers in CRC.