A Structural and Functional Perspective of Death Receptor 6

A Novel Systemic siDR6 Delivery System Based on DP7-C for the Treatment of Metastatic Lung Cancer

Background

The treatment of metastatic lung cancer, a common complication of many primary cancers, has historically been a significant clinical challenge. Once lung metastasis occurs, patients' survival is often significantly shortened. Therefore, prevention and treatment of lung metastases is an important aspect of cancer treatment. In this study, a simple, low-toxicity, cholesterol-modified cationic cell-penetrating peptide DP7 (DP7-C), in combination with siDR6 was used for intravenous administration for the treatment of lung metastases.

Methods

Initially, clinical databases were analyzed to determine the expression levels of death receptor 6 (DR6) in metastatic tumors and the correlation between DR6 expression and patient survival times. The DP7-C/siDR6 micelles were prepared by a self-assembly method. By cultivating 293T, B16F10 and LL2 cells, the in vitro experiments were performed to assess the transfection efficiency, safety and anti-cancer ability of DP7-C/siDR6, while its targeting efficiency and prevention of lungs were investigated by mouse experiments. Furthermore, the therapeutic efficacy of DP7-C/siDR6 was demonstrated in the LL2 model of lung cancer in situ, the B16F10 model of artificial lung metastasis, and the 4T1 model of spontaneous lung metastasis.

Results

The clinical data analysis revealed that DR6 was highly expressed in the majority of metastatic tumors and that patients with high DR6 expression exhibited significantly shorter survival times. The DP7-C/siDR6 showed high transfection efficiency, and it could inhibit tumor cell growth by suppressing the STAT3 signaling pathway. Subsequent mouse experiments demonstrated that intravenous administration of DP7-C/siDR6 resulted in efficient lung targeting. The inhibition of DR6 expression on lung endothelial cells was found to prevent metastasis-induced primary necrosis of lung endothelial cells, thereby preventing tumor metastasis. And the DP7-C/siDR6 treatment showed excellent therapeutic efficacy in the tumor models.

Conclusion

The systemic delivery of DP7-C micelles carrying siDR6 provide an alternative therapeutic strategy to halt cancer lung metastasis.

DR6 Augments Colorectal Cancer Cell Growth, Invasion, and Stemness by Activating AKT/NF-κB Pathway

This study aims to elucidate the role and mechanisms of Death Receptor 6 (DR6), a member of the tumor necrosis factor receptor superfamily, in the malignant progression of colorectal cancer (CRC). The association of DR6 expression levels and CRC patient survival was examined using the CRC cohort data from GEPIA database. The functional role of DR6 in CRC cells was investigated by performing loss-of-function and gain-of-function experiments based on CCK-8 proliferation assay, transwell migration and invasion assay, and sphere-forming assays. Xenograft model of CRC cells in nude mouse was established to evaluate the impact of DR6 knockdown on CRC tumorigenesis. Elevated expression of DR6 was correlated with an unfavorable prognosis in CRC patients. In vitro functional assays demonstrated that silencing DR6 considerably suppressed the proliferation, migration, invasion, and stemness of CRC cells, whereas its overexpression showed an opposite effect. DR6 knockdown also attenuated tumor formation of CRC cells in the nude mice. Mechanistically, silencing DR6 reduced the phosphorylation of AKT and NF-κB in CRC cells, and the treatment with an AKT activator (SC79) abrogated the inhibitory effects of DR6 knockdown on the malignant features of CRC cells. Our data suggest that DR6 contributes to the malignant progression of CRC by activating AKT/NF-κB pathway, indicating its clinical potential as a prognostic marker and therapeutic target for CRC.

Immune activation of the p75 neurotrophin receptor: implications in neuroinflammation

Despite structural similarity with other tumor necrosis factor receptor superfamily (TNFRSF) members, the p75 neurotrophin receptor (p75NTR, TNFR16) mediates pleiotropic biological functions not shared with other TNFRs. The high level of p75NTR expression in the nervous system instead of immune cells, its utilization of co-receptors, and its interaction with soluble dimeric, rather than soluble or cell-tethered trimeric ligands are all characteristics which distinguish it from most other TNFRs. Here, we compare these attributes to other members of the TNFR superfamily. In addition, we describe the recent evolutionary adaptation in B7-1 (CD80), an immunoglobulin (Ig) superfamily member, which allows engagement to neuronally-expressed p75NTR. B7-1-mediated binding to p75NTR occurs in humans and other primates, but not lower mammals due to specific sequence changes that evolved recently in primate B7-1. This discovery highlights an additional mechanism by which p75NTR can respond to inflammatory cues and trigger synaptic elimination in the brain through engagement of B7-1, which was considered to be immune-restricted. These observations suggest p75NTR does share commonality with other immune co-modulatory TNFR family members, by responding to immunoregulatory cues. The evolution of primate B7-1 to bind and elicit p75NTR-mediated effects on neuronal morphology and function are discussed in relationship to immune-driven modulation of synaptic actions during injury or inflammation.