RAB6A functions as a critical modulator of the stem-like subsets in cholangiocarcinoma.

RAB6A is a member of RAB GTPase family and plays an important role in the targeted transport of neurotrophic receptors and inflammatory cytokines. RAB6A-mediated secretory pathway is involved in many physiological and pathological processes. Defects in RAB6A-mediated secretory pathway may lead to the development of many diseases, including cancer. However, its role in cholangiocarcinoma (CCA) has not yet been revealed. We explored the regulatory role of RAB6A in the stem-like subsets of CCA. We showed that RAB6A knockdown (KD) impedes cancer stem cells (CSCs) properties and epithelial-mesenchymal transition in vitro and that suppression of RAB6A inhibits tumor growth in vivo. We screened target cargos of RAB6A in CCA cells and identified a extracellular matrix component as the target cargo. RAB6A binds directly to OPN, and RAB6A KD suppressed OPN secretion and inhibited the interaction between OPN and αV integrin receptor. Moreover, RAB6A KD inhibited the AKT signaling pathway, which is a downstream effector of the integrin receptor signaling. In addition, shRNA targeting OPN blocked endogenous expression of OPN and consequently weakened CSCs properties in RAB6A-formed spheres. Similarly, inhibitor of AKT signaling, MK2206 also impedes oncogenic function of RAB6A in the stem-like subsets of CCA cells. In conclusion, our findings showed that RAB6A sustains CSCs phenotype maintenance by modulating the secretion of OPN and consequentially activating the downstream AKT signaling pathway. Targeting the RAB6A/OPN axis may be an effective strategy for CCA therapy.

FBXO31 sensitizes cancer stem cells-like cells to cisplatin by promoting ferroptosis and facilitating proteasomal degradation of GPX4 in cholangiocarcinoma.

BACKGROUND & AIMS: Cholangiocarcinoma (CCA) is a malignant tumour originating from the biliary epithelium that easily infiltrates, metastasizes and recurs. The deficiency of FBXO31 facilitates the initiation and progression of several types of cancer. However, the involvement of FBXO31 in CCA progression has remained unclear. METHODS: qRT-PCR was used to detect the expression of FBXO31 in CCA. The biological functions of FBXO31 were confirmed in vivo and in vitro. Sphere formation and flow cytometry were used to identify the stem cell properties of CCA. RESULTS: FBXO31 is downregulated in CCA and that deficiency of FBXO31 is associated with the TNM stage of CCA. Functional studies showed FBXO31 inhibits cell growth, migration, invasion, cancer stem cell (CSC) properties and epithelial-mesenchymal transition (EMT) in vitro and impedes tumour growth in vivo. In addition, overexpression of FBXO31 increases the cisplatin (CDDP) sensitivity of CCA cells. RNA-sequencing analysis revealed that FBXO31 is involved in redox biology and metal ion metabolism in CCA cells during CDDP treatment. Further studies revealed that FBXO31 enhances ferroptosis induced by CDDP in CCA and CSC-like cells. FBXO31 enhances ubiquitination of glutathione peroxidase 4 (GPX4), which leads to proteasomal degradation of GPX4. Moreover, overexpression of GPX4 compromises the promoting effects of FBXO31 on CDDP-induced ferroptosis in CCA and CSC-like cells. CONCLUSIONS: Our studies indicate that FBXO31 functions as a tumour suppressor in CCA and sensitizes CSC-like cells to CDDP by promoting ferroptosis and facilitating the proteasomal degradation of GPX4.

Intestinal Barrier Function and Neurodegenerative Disease.

Neurodegenerative diseases are caused by the loss of neurons and/or their myelin sheaths, which deteriorate over time and become dysfunctional. Alzheimer's disease, Parkinson's disease, and multiple sclerosis are among the most prominent neurodegenerative diseases that affect millions of older adults worldwide. Despite extensive research over several decades, controversies still surround the etiology of neurodegenerative diseases, and many of them remain incurable. Meanwhile, an increasing number of new mechanistic studies related to the microbiota-gut-brain axis have emerged, among which the relationship between the function of the intestinal barrier and neurodegenerative diseases has received widespread attention. As one of the first lines of defense between the body and the external environment, the impaired function of the intestinal barrier is closely related to the development of neurodegenerative pathologies. Among them, the microbiota-gut-brain axis disorder characterized by intestinal barrier disruption mainly includes impaired function of the intestinal microbial barrier, chemical barrier, mechanical barrier, and immune barrier. This review focuses on the structure and molecular mechanisms of the various layers of the intestinal barrier as well as their relationship with neurodegenerative lesions. In recent years, intestinal barrier repair therapies have provided new ideas for the studied disease treatment modalities. We believe that a better understanding of the role of the intestinal barrier in neurodegenerative diseases would provide new insights for the development of viable therapeutic strategies for patients.