iASPP suppression mediates terminal UPR and improves BRAF-inhibitor sensitivity of colon cancers

Exploring Anthracycline-Induced Cardiotoxicity from the Perspective of Protein Quality Control

Anthracyclines are effective anticancer drugs; however, their use is restricted because of their dose-dependent, time-dependent and irreversible myocardial toxicity. The mechanism of anthracycline cardiotoxicity has been widely studied but remains unclear. Protein quality control is crucial to the stability of the intracellular environment and, ultimately, to the heart because cardiomyocytes are terminally differentiated. Two evolutionarily conserved mechanisms, autophagy, and the ubiquitin-proteasome system, synergistically degrade misfolded proteins and remove defective organelles. Recent studies demonstrated the importance of these mechanisms. Further studies will reveal the detailed metabolic pathway and metabolic control of the protein quality control mechanism integrated into anthracycline-induced cardiotoxicity. This review provides theoretical support for clinicians in the application and management of anthracyclines.

PANoptosis-related genes function as efficient prognostic biomarkers in colon adenocarcinoma

Background

PANoptosis is a newly discovered cell death type, and tightly associated with immune system activities. To date, the mechanism, regulation and application of PANoptosis in tumor is largely unknown. Our aim is to explore the prognostic value of PANoptosis-related genes in colon adenocarcinoma (COAD).

Methods

Analyzing data from The Cancer Genome Atlas-COAD (TCGA-COAD) involving 458 COAD cases, we concentrated on five PANoptosis pathways from the Molecular Signatures Database (MSigDB) and a comprehensive set of immune-related genes. Our approach involved identifying distinct genetic COAD subtype clusters and developing a prognostic model based on these parameters.

Results

The research successfully identified two genetic subtype clusters in COAD, marked by distinct profiles in PANoptosis pathways and immune-related gene expression. A prognostic model, incorporating these findings, demonstrated significant predictive power for survival outcomes, underscoring the interplay between PANoptosis and immune responses in COAD.

Conclusion

This study enhances our understanding of COAD's genetic framework, emphasizing the synergy between cell death pathways and the immune system. The development of a prognostic model based on these insights offers a promising tool for personalized treatment strategies. Future research should focus on validating and refining this model in clinical settings to optimize therapeutic interventions in COAD.

Pentapeptide PYRAE triggers ER stress-mediated apoptosis of breast cancer cells in mice by targeting RHBDF1-BiP interaction

Reinforced cellular responses to endoplasmic reticulum (ER) stress are caused by a variety of pathological conditions including cancers. Human rhomboid family-1 protein (RHBDF1), a multiple transmembrane protein located mainly on the ER, has been shown to promote cancer development, while the binding immunoglobulin protein (BiP) is a key regulator of cellular unfolded protein response (UPR) for the maintenance of ER protein homeostasis. In this study, we investigated the role of RHBDF1 in maintaining ER protein homeostasis in breast cancer cells. We showed that deleting or silencing RHBDF1 in breast cancer cell lines MCF-7 and MDA-MB-231 caused marked aggregation of unfolded proteins in proximity to the ER. We demonstrated that RHBDF1 directly interacted with BiP, and this interaction had a stabilizing effect on the BiP protein. Based on the primary structural motifs of RHBDF1 involved in BiP binding, we found a pentapeptide (PE5) targeted BiP and inhibited BiP ATPase activity. SPR assay revealed a binding affinity of PE5 toward BiP (Kd = 57.7 μM). PE5 (50, 100, 200 μM) dose-dependently promoted ER protein aggregation and ER stress-mediated cell apoptosis in MCF-7 and MDA-MB-231 cells. In mouse 4T1 breast cancer xenograft model, injection of PE5 (10 mg/kg, s.c., every 2 days for 2 weeks) significantly inhibited the tumor growth with markedly increased ER stress and apoptosis-related proteins in tumor tissues. Our results suggest that the ability of RHBDF1 to maintain BiP protein stability is critical to ER protein homeostasis in breast cancer cells, and that the pentapeptide PE5 may serve as a scaffold for the development of a new class of anti-BiP inhibitors.

FBXO5-mediated RNF183 degradation prevents endoplasmic reticulum stress-induced apoptosis and promotes colon cancer progression

Endoplasmic reticulum (ER) stress induces the unfolded protein response (UPR), and prolonged ER stress leads to cell apoptosis. Despite increasing research in this area, the underlying molecular mechanisms remain unclear. Here, we discover that ER stress upregulates the UPR signaling pathway while downregulating E2F target gene expression and inhibiting the G2/M phase transition. Prolonged ER stress decreases the mRNA levels of E2F2, which specifically regulates the expression of F-Box Protein 5(FBXO5), an F-box protein that functions as an inhibitor of the anaphase-promoting complex/cyclosome (APC/C) ubiquitin ligase complex. Depletion of FBXO5 results in increased ER stress-induced apoptosis and decreased expression of proteins related to PERK/IRE1α/ATF6 signaling. Overexpression of FBXO5 wild-type (not its ΔF-box mutant) alleviates apoptosis and the expression of the C/EBP Homologous Protein (CHOP)/ATF. Mechanistically, we find that FBXO5 directly binds to and promotes the ubiquitin-dependent degradation of RNF183, which acts as a ubiquitin E3 ligase in regulating ER stress-induced apoptosis. Reversal of the apoptosis defects caused by FBXO5 deficiency in colorectal cancer cells can be achieved by knocking down RNF183 in FBXO5-deficient cells. Functionally, we observed significant upregulation of FBXO5 in colon cancer tissues, and its silencing suppresses tumor occurrence in vivo. Therefore, our study highlights the critical role of the FBXO5/RNF183 axis in ER stress regulation and identifies a potential therapeutic target for colon cancer treatment.