Caspase-8 Deficient Osteoblastic Cells Display Alterations in Non-Apoptotic Pathways

GDF10 Regulates Iron-Dependent Lipid Oxidation in Colorectal Cancer Cells Through Interaction With IGF2

BACKGROUND

This study aims to identify genes with a high likelihood of genetic variation, significant expression differences, and prognostic implications in colorectal cancer (CRC) patients. The research also seeks to investigate the role and mechanisms of key genes in CRC through the analysis of health information data and a combination of internal and external experiments.

METHODS

The sequence information of CRC patients was obtained from the Cancer Genome Atlas Program (TCGA) database. Key genes were identified through differential expression analysis, enrichment analysis, interaction analysis, and survival curve analysis. Subsequently, Growth and Differentiation Factor 10 (GDF10) overexpression and knockout cell models were developed to investigate the impact of GDF10 on CRC cells using assays such as CCK8, flow cytometry, Transwell, and subcutaneous tumor formation in nude mice. Mechanistically, the effects of GDF10 and IGF2 genes on autophagy, apoptosis, and ferroptosis were studied by introducing different death pathway inhibitors. Changes in reactive oxygen species (ROS), GSH, and MDA levels in cells following silencing were also assessed. Furthermore, the influence of GDF10 and its interacting protein IGF2 on ferroptosis was evaluated through ELISA and fluorescence staining.

RESULTS

The analysis of patients in the TCGA database revealed that GDF10 expression was low in microsatellite stable (MSS) type and high in microsatellite instability (MSI) type. It was found to interact with IGF2, with low expression associated with a better prognosis. Overexpression of GDF10 was shown to significantly enhance the proliferation and invasion abilities of CRC cells, whereas low expression promoted cell apoptosis. Within the pathways of autophagy, apoptosis, and ferroptosis, low expression of GDF10 primarily regulated ferroptosis in cells. This regulation involved promoting the iron-dependent lipid oxidation process by mediating binding with IGF2, leading to increased concentrations of iron ions and oxidative metabolites in cells. This process also reduced the formation of lipid droplets and inhibited tumor development.

CONCLUSION

GDF10 plays a crucial role in regulating ferroptosis in CRC cells through mediating IGF2 interaction, suggesting it as a promising therapeutic target for CRC.

Caspase-12 affects chondrogenesis in mice

Caspase-12 is a molecule whose functions are still not well understood. Although its expression has been found in various tissues, specific roles have been described in only a few cases. These include the effect of caspase-12 on murine bone cell differentiation during craniofacial development. This work focused on the development of the limbs taking place through endochondral ossification, which precedes the formation of the cartilaginous growth plate. Caspase-12 was described here for the first time in growth plate chondrocytes during physiological development. Using pharmacological inhibition, caspase-12 was found to affect chondrogenesis. Limb-derived micromass cultures showed a significantly increased area of chondrogenic nodules after caspase-12 inhibition and there were changes in gene expression, the most significant of which was the reduction of Mmp9. These data point to potential new functions of caspase-12 in chondrogenesis.

Caspase-9 Is a Positive Regulator of Osteoblastic Cell Migration Identified by diaPASEF Proteomics

Caspase-9 is traditionally considered the initiator caspase of the intrinsic apoptotic pathway. In the past decade, however, other functions beyond initiation/execution of cell death have been described including cell type-dependent regulation of proliferation, differentiation/maturation, mitochondrial, and endosomal/lysosomal homeostasis. As previous studies revealed nonapoptotic functions of caspases in osteogenesis and bone homeostasis, this study was performed to identify proteins and pathways deregulated by knockout of caspase-9 in mouse MC3T3-E1 osteoblasts. Data-independent acquisition-parallel accumulation serial fragmentation (diaPASEF) proteomics was used to compare protein profiles of control and caspase-9 knockout cells. A total of 7669 protein groups were quantified, and 283 upregulated/141 downregulated protein groups were associated with the caspase-9 knockout phenotype. The deregulated proteins were mainly enriched for those associated with cell migration and motility and DNA replication/repair. Altered migration was confirmed in MC3T3-E1 cells with the genetic and pharmacological inhibition of caspase-9. ABHD2, an established regulator of cell migration, was identified as a possible substrate of caspase-9. We conclude that caspase-9 acts as a modulator of osteoblastic MC3T3-E1 cell migration and, therefore, may be involved in bone remodeling and fracture repair.

Inhibition of caspase-8 cascade restrains the osteoclastogenic fate of bone marrow cells

Osteoclasts are multinucleated cells of hematopoietic origin, with a pivotal role in bone development and remodeling. Failure in osteoclast differentiation and activation leads to various bone disorders; thus, attention has focused on a search of molecules involved in osteoclast regulatory pathways. Caspase-8 appears to be an interesting candidate for further exploration, due to its potential function in bone development and homeostasis. Mouse bone marrow cells were differentiated into osteoclasts by RANKL stimulation. Increased activation of caspase-8 and its downstream executioner caspases (caspase-3 and caspase-6) was found during osteoclastogenesis. Subsequent inhibition of caspase-8, caspase-3, or caspase-6, respectively, during osteoclast differentiation showed distinct changes in the formation of TRAP-positive multinucleated cells and reduced expression of osteoclast markers including Acp5, Ctsk, Dcstamp, and Mmp9. Analysis of bone matrix resorption confirmed significantly reduced osteoclast function after caspase inhibition. The results clearly showed the role of caspases in the proper development of osteoclasts and contributed new knowledge about non-apoptotic function of caspases.

How does caspases regulation play role in cell decisions? apoptosis and beyond

Caspases are a family of cysteine proteases, and the key factors behind the cellular events which occur during apoptosis and inflammation. However, increasing evidence shows the non-conventional pro-survival action of apoptotic caspases in crucial processes. These cellular events include cell proliferation, differentiation, and migration, which may appear in the form of metastasis, and chemotherapy resistance in cancerous situations. Therefore, there should be a precise and strict control of caspases activity, perhaps through maintaining the threshold below the required levels for apoptosis. Thus, understanding the regulators of caspase activities that render apoptotic caspases as non-apoptotic is of paramount importance both mechanistically and clinically. Furthermore, the functions of apoptotic caspases are affected by numerous post-translational modifications. In the present mini-review, we highlight the various mechanisms that directly impact caspases with respect to their anti- or non-apoptotic functions. In this regard, post-translational modifications (PTMs), isoforms, subcellular localization, transient activity, substrate availability, substrate selection, and interaction-mediated regulations are discussed.