Energy stress promotes P-bodies formation via lysine-63-linked polyubiquitination of HAX1.

Energy stress, characterized by the reduction of intracellular ATP, has been implicated in various diseases, including cancer. Here, we show that energy stress promotes the formation of P-bodies in a ubiquitin-dependent manner. Upon ATP depletion, the E3 ubiquitin ligase TRIM23 catalyzes lysine-63 (K63)-linked polyubiquitination of HCLS1-associated protein X-1 (HAX1). HAX1 ubiquitination triggers its liquid‒liquid phase separation (LLPS) and contributes to P-bodies assembly induced by energy stress. Ubiquitinated HAX1 also interacts with the essential P-body proteins, DDX6 and LSM14A, promoting their condensation. Moreover, we find that this TRIM23/HAX1 pathway is critical for the inhibition of global protein synthesis under energy stress conditions. Furthermore, high HAX1 ubiquitination, and increased cytoplasmic localization of TRIM23 along with elevated HAX1 levels, promotes colorectal cancer (CRC)-cell proliferation and correlates with poor prognosis in CRC patients. Our data not only elucidate a ubiquitination-dependent LLPS mechanism in RNP granules induced by energy stress but also propose a promising target for CRC therapy.

COPS5 and LASP1 synergistically interact to downregulate 14-3-3σ expression and promote colorectal cancer progression via activating PI3K/AKT pathway.

Overexpression of LIM and SH3 protein 1 (LASP1) is required for colorectal cancer (CRC) development and progression. Here, C-Jun activation domain-binding protein-1 (Jab1), also known as COP9 signalosome subunit 5 (COPS5), was verified as a new LASP1-interacting protein through yeast two-hybrid assay. The role of COPS5 in LASP1-mediated CRC progression remains unknown. GST pull-down assay indicated that the SH3 domain of LASP1 could directly bind to MPN domain of COPS5. In vitro gain- and loss-of-function analyses revealed the stimulatory role of COPS5 on CRC cell proliferation, migration and invasion. Endogenous overexpression of COPS5 could also enhance the homing capacity of CRC cells in vivo. Further analysis showed that COPS5 and LASP1 synergistically interact to stimulate the ubiquitination and degradation of 14-3-3σ and promote colorectal cancer progression via PI3K/Akt dependent signaling pathway. Clinically, the expression of COPS5 was studied in CRC tissues and it is associated with CRC differentiation, metastasis and poor prognosis. The colocalization of LASP1 and COPS5 was demonstrated in both nonmetastatic and metastatic CRC tissues. A positive correlation was found between the expression of LASP1 and COPS5 while a negative correlation existed between 14-3-3σ and COPS5/LASP1 in most CRC samples. A combination of COPS5 and LASP1 tends to be an independent prognostic indicator for CRC patients, and this is also suitable for CRC without lymph node metastasis. The current research has further advanced our understanding on the complicated molecular mechanism underlying LASP1-mediated CRC progression, which hopefully will contribute to the development of novel diagnostic and therapeutic strategies in CRC.

Gut microbiota-stimulated cathepsin K secretion mediates TLR4-dependent M2 macrophage polarization and promotes tumor metastasis in colorectal cancer.

Metastasis is a complex process that requires the interaction between tumor cells and their microenvironment. As an important regulator of intestinal microenvironment, gut microbiota plays a significant role in the initiation and progression of colorectal cancer (CRC), but the underlying mechanisms remain elusive. In this study, a metastasis-related secretory protein cathepsin K (CTSK) was identified as a vital mediator between the imbalance of intestinal microbiota and CRC metastasis. We implanted MC38 cells into the cecal mesentry of antibiotic-treated mice with intragastrically administration of E. coli to mimic gut microbiota imbalance. The bigger primary tumors and more liver metastatic foci were detected in the E. coli group accompanied with high LPS secretion and CTSK overexpression compared with that in the control group. CTSK contributes to the aggressive phenotype of CRC cells both in vitro and in vivo. Silencing CTSK or administration of Odanacatib, a CTSK-specific inhibitor, totally abolished the CTSK-enhanced migration and motility of CRC cells. Interestingly, the tumor-secreted CTSK could bind to toll-like receptor 4 (TLR4) to stimulate the M2 polarization of tumor-associated macrophages (TAMs) via an mTOR-dependent pathway. Recombinant CTSK could neither stimulate CRC growth and metastasis, nor induce M2 macrophage polarization in TRL4-/- mice. Meanwhile, CTSK could stimulate the secretion of cytokines by M2 TAMs including IL10 and IL17, which, in turn, promote the invasion and metastasis of CRC cells through NFκB pathway. Clinically, overexpression of CTSK in human CRC tissues is always accompanied with high M2 TAMs in the stroma, and correlated with CRC metastasis and poor prognosis. Our current research identified CTSK as a mediator between the imbalance of gut microbiota and CRC metastasis. More importantly, we illustrated a CTSK-mediated-positive feedback loop between CRC cells and TAMs during metastasis, prompting CTSK as a novel predictive biomarker and feasible therapeutic target for CRC.

MicroRNA-105 is involved in TNF-α-related tumor microenvironment enhanced colorectal cancer progression.

TNF-α is a central proinflammatory cytokine contributing to malignant tumor progression in tumor microenvironment. In this study, we found the upregulation of miR-105 in colorectal cancer was associated with aggressive phenotype, and the enhanced expression of miR-105 was required for TNF-α-induced epithelial-mesenchymal transition (EMT). The expression of miR-105 was remarkably stimulated by TNF-α in a time-dependent manner using real-time qPCR analysis. Inhibition of miR-105 remarkably weakened the aggressive effects of TNF-α through preventing the activation of NF-κB signaling and the initiation of EMT. Furthermore, miR-105 was demonstrated directly targeted on the 3'-UTRs of RAP2C, a Rap2 subfamily of small GTP-binding protein. Consistently, suppression of RAP2C stimulated the role of miR-105, which dramatically promoted the invasion and metastasis of CRC cells. Thalidomide, a TNF-α and NF-κB inhibitor, significantly weakened the metastasis and homing capacity of miR-105-overexpressed CRC cells in nude mice. Our investigation initiatively illustrated the modulatory role of miR-105 in TNF-α-induced EMT and further CRC metastasis. We also offer a better understanding of TNFα-induced metastasis and suggest an effective therapeutic strategy against CRC metastasis.