High Level of Legumain Was Correlated With Worse Prognosis and Peritoneal Metastasis in Gastric Cancer Patients

Cancer Cell Secreted Legumain Promotes Gastric Cancer Resistance to Anti-PD-1 Immunotherapy by Enhancing Macrophage M2 Polarization

The interaction between cancer cells and immune cells plays critical roles in gastric cancer (GC) progression and immune evasion. Forced legumain (LGMN) is one of the characteristics correlated with poor prognosis in gastric cancer patients. However, the role of gastric-cancer-secreted LGMN (sLGMN) in modulating the tumor immune microenvironment and the biological effect on the immune evasion of gastric cancer remains unclear. In this study, we found that forced expression of sLGMN in gastric cancer serum correlates with increased M2 macrophage infiltration in GC tissues and predicted resistance to anti-PD-1 immunotherapy. Mechanistically, gastric cancer cells secrete LGMN via binding to cell surface Integrin αvβ3, then activate Integrin αvβ3/PI3K (Phosphatidylinositol-4,5-bisphosphate3-kinase)/AKT (serine/threonine kinase)/mTORC2 (mammalian target of rapamycin complex 2) signaling, promote metabolic reprogramming, and polarize macrophages from the M1 to the M2 phenotype. Either blocking LGMN, Integrin αv, or knocking out Integrin αv expression and abolishing the LGMN/Integrin αvβ3 interaction significantly inhibits metabolic reprogramming and polarizes macrophages from the M1 to the M2 phenotype. This study reveals a critical molecular crosstalk between gastric cancer cells and macrophages through the sLGMN/Integrinαvβ3/PI3K/AKT/mTORC2 axis in promoting gastric cancer immune evasion and resistance to anti-PD-1 immunotherapy, indicating that the sLGMN/Integrinαvβ3/PI3K/AKT/mTORC2 axis may act as a promising therapeutic target.

Investigation of prognostic values of immune infiltration and LGMN expression in the microenvironment of osteosarcoma

BACKGROUND

Osteosarcoma (OS), the most common primary malignant bone tumor, predominantly affects children and young adults and is characterized by high invasiveness and poor prognosis. Despite therapeutic advancements, the survival rate remains suboptimal, indicating an urgent need for novel biomarkers and therapeutic targets. This study aimed to investigate the prognostic significance of LGMN expression and immune cell infiltration in the tumor microenvironment of OS.

METHODS

We performed an integrative bioinformatics analysis utilizing the GEO and TARGET-OS databases to identify differentially expressed genes (DEGs) associated with LGMN in OS. We conducted Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and Gene Set Enrichment Analysis (GSEA) to explore the biological pathways and functions. Additionally, we constructed protein-protein interaction (PPI) networks, a competing endogenous RNA (ceRNA) network, and applied the CIBERSORT algorithm to quantify immune cell infiltration. The diagnostic and prognostic values of LGMN were evaluated using the area under the receiver operating characteristic (ROC) curve and Cox regression analysis. Furthermore, we employed Consensus Clustering Analysis to explore the heterogeneity within OS samples based on LGMN expression.

RESULTS

The analysis revealed significant upregulation of LGMN in OS tissues. DEGs were enriched in immune response and antigen processing pathways, suggesting LGMN's role in immune modulation within the TME. The PPI and ceRNA network analyses provided insights into the regulatory mechanisms involving LGMN. Immune cell infiltration analysis indicated a correlation between high LGMN expression and increased abundance of M2 macrophages, implicating an immunosuppressive role. The diagnostic AUC for LGMN was 0.799, demonstrating its potential as a diagnostic biomarker. High LGMN expression correlated with reduced overall survival (OS) and progression-free survival (PFS). Importantly, Consensus Clustering Analysis identified two distinct subtypes of OS, highlighting the heterogeneity and potential for personalized medicine approaches.

CONCLUSIONS

Our study underscores the prognostic value of LGMN in osteosarcoma and its potential as a therapeutic target. The identification of LGMN-associated immune cell subsets and the discovery of distinct OS subtypes through Consensus Clustering Analysis provide new avenues for understanding the immunosuppressive TME of OS and may aid in the development of personalized treatment strategies. Further validation in larger cohorts is warranted to confirm these findings.

Hypoxia-driven protease legumain promotes immunosuppression in glioblastoma

Glioblastoma (GBM) is a hypoxic and "immune-cold" tumor containing rich stromal signaling molecules and cell populations, such as proteases and immunosuppressive tumor-associated macrophages (TAMs). Here, we seek to profile and characterize the potential proteases that may contribute to GBM immunosuppression. Legumain (LGMN) emerges as the key protease that is highly enriched in TAMs and transcriptionally upregulated by hypoxia-inducible factor 1-alpha (HIF1α). Functionally, the increased LGMN promotes TAM immunosuppressive polarization via activating the GSK-3β-STAT3 signaling pathway. Inhibition of macrophage HIF1α and LGMN reduces TAM immunosuppressive polarization, impairs tumor progression, enhances CD8+ T cell-mediated anti-tumor immunity, and synergizes with anti-PD1 therapy in GBM mouse models. Thus, LGMN is a key molecular switch connecting two GBM hallmarks of hypoxia and immunosuppression, providing an actionable therapeutic intervention for this deadly disease.

Data-Independent Acquisition Mass Spectrometry Analysis of FFPE Rectal Cancer Samples Offers In-Depth Proteomics Characterization of the Response to Neoadjuvant Chemoradiotherapy

Locally advanced rectal cancer (LARC) presents a challenge in identifying molecular markers linked to the response to neoadjuvant chemoradiotherapy (nCRT). This study aimed to utilize a sensitive proteomic method, data-independent mass spectrometry (DIA-MS), to extensively analyze the LARC proteome, seeking individuals with favorable initial responses suitable for a watch-and-wait approach. This research addresses the unmet need to understand the response to treatment, potentially guiding personalized strategies for LARC patients. Post-treatment assessment included MRI scans and proctoscopy. This research involved 97 LARC patients treated with intense chemoradiotherapy, comprising radiation and chemotherapy. Out of 97 LARC included in this study, we selected 20 samples with the most different responses to nCRT for proteome profiling (responders vs. non-responders). This proteomic approach shows extensive proteome coverage in LARC samples. The analysis identified a significant number of proteins compared to a prior study. A total of 915 proteins exhibited differential expression between the two groups, with certain signaling pathways associated with response mechanisms, while top candidates had good predictive potential. Proteins encoded by genes SMPDL3A, PCTP, LGMN, SYNJ2, NHLRC3, GLB1, and RAB43 showed high predictive potential of unfavorable treatment outcome, while RPA2, SARNP, PCBP2, SF3B2, HNRNPF, RBBP4, MAGOHB, DUT, ERG28, and BUB3 were good predictive biomarkers of favorable treatment outcome. The identified proteins and related biological processes provide promising insights that could enhance the management and care of LARC patients.

Metformin regulates autophagy via LGMN to inhibit choriocarcinoma

Choriocarcinoma has the problem of chemotherapy insensitivity and recurrence. Metformin may be a promising candidate to restrict choriocarcinoma progress because of its indirect and direct beneficial role on inhabitations of cancer cells without severe adverse side effects. In this study, metformin pressed the proliferation and invasion of choriocarcinoma JAR cells in vitro and the growth of the JAR subcutaneous xenografts in vivo. The high throughput sequencing and bioinformatics technology identified the low expression of legumain (LGMN) in lysosomal pathway caused by metformin, which was upregulated in human choriocarcinoma tissues compared with the early pregnancy tissues. As elevating metformin concentration and treatment time, the mRNA and protein expression of LGMN both depressed in two choriocarcinoma cell lines (JAR and JEG-3). LGMN was involved in metformin-mediated inhibition of cell proliferation and invasion. Furthermore, metformin induced autophagy via inhibiting LGMN through AKT/mTOR/LC3II signaling pathway of choriocarcinoma. Autophagy inhibitor could depress metformin-induced autophagy and improve cell proliferation and invasion ability dropped by metformin, while autophagy inducer could partially reverse the change of cell proliferation and invasion modulated by combination of metformin and LGMN overexpression. These results indicated that metformin inhibited cell proliferation and invasion ability by inducing autophagy in a LGMN-dependent manner so as to play a role in the treatment of choriocarcinoma.

Up-regulation of collagen type V alpha 2 (COL5A2) promotes malignant phenotypes in gastric cancer cell via inducing epithelial-mesenchymal transition (EMT)

Recent studies have reported that collagen type V alpha 2 (COL5A2) is a hub gene and associated with the prognosis of gastric cancer (GC) patients, playing an important role in GC. In this study, we aim to fathom out the biological roles of COL5A2 and its relevant mechanism in GC. Oncomine, gene expression profiling interactive analysis, and UALCAN were used to explore the effects of COL5A2 on GC. Cell counting kit-8 assay, colony formation assay, and transwell assay were conducted to investigate the biological behaviors of GC cell lines AGS and SGC-7901. Quantitative reverse transcription polymerase chain reaction and western blot were performed to determine gene and protein expressions. COL5A2 expression was up-regulated and negatively correlated with survival percentage of GC patients. COL5A2 expression was notably elevated in high stage and high grade of GC. Down-regulation of COL5A2 inhibited proliferation, migration, and invasion of AGS and SGC-7901 cells. COL5A2 induced epithelial-mesenchymal transition (EMT) by promoting the expressions of mesenchymal markers (SNAI1, SNAI2, TWIST, VIM, and MMP2), thereby facilitating the malignant phenotypes of GC. COL5A2 plays an oncogenic role in GC and has potential to predict the progression and prognosis of GC patients.

Development of a Promising 18F-Radiotracer for PET Imaging Legumain Activity In Vivo

Legumain has been found overexpressed in several cancers, which serves as an important biomarker for cancer diagnosis. In this research, a novel fluorine-18 labeled radioactive tracer [18F]SF-AAN targeting legumain was designed and synthesized for positron emission tomography (PET) imaging. Nonradioactive probe [19F]SF-AAN was obtained through chemical and solid phase peptide synthesis. After a simple one-step 18F labeling, the radiotracer [18F]SF-AAN was obtained with a high radiochemical conversion rate (>85%) and radiochemical purity (99%) as well as high molar activity (12.77 ± 0.50 MBq/nmol). The targeting specificity of [18F]SF-AAN for detecting legumain activity was investigated systematically in vitro and in vivo. In vitro cellular uptake assay showed that the uptake of [18F]SF-AAN in legumain-positive MDA-MB-468 cells was twice as much as that in legumain-negative PC-3 cells at 4 h. In vivo PET imaging revealed that the tumor uptake of [18F]SF-AAN in MDA-MB-468 tumor-bearing mice was about 2.7 times of that in PC-3 tumor-bearing mice at 10 min post injection. The experimental results indicated that [18F]SF-AAN could serve as a promising PET tracer for detecting the legumain expression sensitively and specifically, which would be beneficial for the diagnosis of legumain-related diseases.

Lysosomal peptidases – Intriguing roles in cancer progression and neurodegeneration

Lysosomal peptidases are hydrolytic enzymes capable of digesting waste proteins that are targeted to lysosomes via endocytosis and autophagy. Besides intracellular protein catabolism, they play more specific roles in several other cellular processes and pathologies, either within lysosomes, upon secretion into the cell cytoplasm or extracellular space, or bound to the plasma membrane. In cancer, lysosomal peptidases are generally associated with disease progression, as they participate in crucial processes leading to changes in cell morphology, signaling, migration, and invasion, and finally metastasis. However, they can also enhance the mechanisms resulting in cancer regression, such as apoptosis of tumor cells or antitumor immune responses. Lysosomal peptidases have also been identified as hallmarks of aging and neurodegeneration, playing roles in oxidative stress, mitochondrial dysfunction, abnormal intercellular communication, dysregulated trafficking, and the deposition of protein aggregates in neuronal cells. Furthermore, deficiencies in lysosomal peptidases may result in other pathological states, such as lysosomal storage disease. The aim of this review was to highlight the role of lysosomal peptidases in particular pathological processes of cancer and neurodegeneration and to address the potential of lysosomal peptidases in diagnosing and treating patients.

The Mechanism of Asparagine Endopeptidase in the Progression of Malignant Tumors: A Review

Asparagine endopeptidase (AEP), also called legumain, is currently the only known cysteine protease that specifically cleaves peptide bonds in asparaginyl residue in the mammalian genome. Since 2003, AEP has been reported to be widely expressed in a variety of carcinomas and is considered a potential therapeutic target. In the following years, researchers intensively investigated the substrates of AEP and the mechanism of AEP in partial tumors. With the identification of substrate proteins such as P53, integrin αvβ3, MMP-2, and MMP-9, the biochemical mechanism of AEP in carcinomas is also more precise. This review will clarify the probable mechanisms of AEP in the progression of breast carcinoma, glioblastoma, gastric carcinoma, and epithelial ovarian carcinoma. This review will also discuss the feasibility of targeted therapy with AEP inhibitor (AEPI) in these carcinomas.