Spontaneous miscarriage, the most prevalent complication of early pregnancy, poses substantial risks to maternal health worldwide. Perfluorooctanoic acid (PFOA) is a ubiquitous environmental persistent organic pollutant. Human epidemiological studies have linked PFOA exposure to spontaneous miscarriages, yet the underlying mechanisms have been rarely explored. In this study, we found PFOA exposure induced embryonic absorption in pregnant mice by causing ammonia retention in macrophages. Excessive ammonia disrupted mitochondrial function and compromised lysosomal integrity, which ultimately impaired macrophage function. Furthermore, lysosomal dysfunction reduced secretion of cathepsin B (CTSB) and led to decreased macrophage infiltration and diminished trophoblast invasion. Mechanistically, PFOA exposure led to macrophages ammonia retention by promoting the glutaminolysis through the upregulation of glutaminase (GLS) expression. By downregulating the inhibitor of DNA binding protein 3 (ID3), PFOA enhanced nuclear translocation and DNA-binding affinity of transcription factor 12 (TCF12), which directly activated glutaminase (GLS) transcription to fuel glutamine catabolism. Collectively, our findings delineated a previously unrecognized pathway linking environmental PFOA exposure to spontaneous miscarriage via ammonia-driven macrophage impairment.

Multi-omics data mining reveals macrophage-mediated effects of cathepsin B on esophageal adenocarcinoma risk.

ABSTRACT Clinical treatment of temozolomide (TMZ)‐resistant glioblastoma (GBM) remains a significant challenge. This study aims to develop a multifunctional biomimetic Nano‐AUTAC (BM@pPPD/TMZ) that can selectively degrade β‐catenin via autophagy, thereby overcoming TMZ resistance in GBM. BM@pPPD/TMZ is capable of penetrating the blood‐brain barrier (BBB), targeting GBM lesions via microglia‐derived membrane camouflage, and inducing degradation of β‐catenin through the autophagy‐lysosomal pathway. For improving the selective and efficient degradation of β‐catenin, BM@pPPD/TMZ is functionalized with a tri‐functional peptide comprising a β‐catenin‐binding domain, a cathepsin B (CTSB)‐cleavable GLFG linker, and a phosphatidylserine (PS)‐targeting motif. In the GBM microenvironment, the elevated CTSB triggers linker cleavage, promoting membrane shedding and enhancing the cellular uptake. Meanwhile, the incorporation of the cationic lipid DOTAP promotes autophagosome formation, further facilitating degradation of β‐catenin. Both in vitro and in vivo studies demonstrate that BM@pPPD/TMZ is able to effectively penetrate the BBB and accumulate within tumor lesion, concurrently promoting β‐catenin degradation and MGMT downregulation. This finding provides a promising nanotherapeutic strategy for overcoming TMZ resistance and improving GBM therapeutic efficacy.

Targeted protein degradation (TPD) has arisen as a therapeutic revolution for eliminating disease-relevant proteins, but its tissue-specific delivery remains a critical challenge. Here, we developed an asialoglycoprotein receptor (ASGPR)-based platform for the selective degradation of target proteins in hepatocytes. By conjugating the ASGPR ligand triantennary N-acetylgalactosamine (tri-GalNAc) with a BRD4-targeted proteolysis targeting chimera (PROTAC) via a cathepsin B (CTSB)-cleavable Val-Cit-PABC linker, we generated a prototype GalNAc-PROTAC conjugate, TMU454. TMU454 selectively degraded BRD4 in ASGPR-positive hepatocellular carcinoma cells while sparing ASGPR-negative cancer cells and normal cells. Mechanistic investigations confirmed that TMU454-mediated BRD4 degradation is dependent on the ASGPR-mediated endocytosis, CTSB-mediated linker cleavage, and ubiquitin-proteasome system (UPS). Furthermore, a fluorescein-labeled analogue, TMU670, revealed preferential liver accumulation. Importantly, TMU454 significantly inhibited tumor growth in a Huh7-derived liver cancer xenograft model without apparent systemic toxicity. Collectively, this study establishes a versatile approach for tissue-selective protein degradation and advances targeted therapies for liver cancer.

Exposure to ultraviolet (UV) radiation is known to cause acute skin damage and inflammation, yet the underlying molecular mechanisms and cellular damage involved in this process remain poorly understood. In this study, we provide compelling evidence that UV-induced fibroblast pyroptosis not only triggers a cascade of macrophage inflammatory responses but also could represents a important mechanism in the pathogenesis of acute sunburn. We further investigate the intricate interplay between pyroptotic fibroblasts (Pyr-Fbs) and macrophages, elucidating the resultant alterations in macrophage phenotypes and the subsequent inflammatory cascade. At the molecular level, our study reveals a significant upregulation of cathepsin B (CTSB) expression in fibroblasts upon UV exposure. Furthermore, we demonstrated that utilization of skin microneedles (MNs) loaded antisense oligonucleotides (ASO) targeting Ctsb enables controlled release, effectively mitigating the detrimental effects of UV-induced damage and inflammation. Importantly, our findings highlight the critical role of CTSB in regulating the activity of the NLRP3 inflammasome through its binding to the leucine-rich repeat (LRR) domain, thereby modulating the progression of pyroptosis and subsequent macrophage-driven inflammation. Overall, our findings shed new light on the significance of CTSB in UV-induced Pyr-Fbs and propose a promising clinical treatment strategy involving ASO therapy delivered via MNs.

The existing diagnostic methods of diabetic foot ulcer (DFU) complicated with peripheral vascular disease (PVD) lack sufficient potential for early identification, which leads to slow wound healing, amputation and even death. Thus, this study aimed to explore the potential serum biomarkers of DFU complicated with PVD. A target gene of DFU complicated with PVD was identified using single-cell transcriptome analysis. The immunohistochemistry, ELISA, clinical correlation analysis, tubulogenesis assay, CCK8 assay, and scratch assay were used to verify the correlation between this target gene and DFU complicated with PVD. The ELISA experiment was used to detect the target gene in serum. In this study, the result of PPI in single-cell transcriptomes showed that cathepsin B (CTSB) was enriched in vascular endothelial cells of DFU. The immunohistochemistry and ELISA results revealed that CTSB was highly expressed in the tissues and serum of patients with the combination of DFU and PVD, and this expression increased with the increase of the Wagner grade of DFU. Clinical correlation analysis indicated that CTSB expression is positively correlated with the clinical indicators of the combination of DFU and PVD. Knockdown of CTSB promoted tubulogenesis, proliferation and migration of vascular endothelial cells and overexpression of CTSB has the opposite effect. CTSB, a secretory protein, can be detected as a diagnostic biomarker in serum. Therefore, this study suggested that CTSB can be used as a potential serum diagnostic biomarker for DFU complicated with PVD, which is helpful for the early diagnosis of this disease, prognosis monitoring and adjustment of treatment plans.

Intestinal ischemia‑reperfusion (I/R) injury is a clinical condition that leads to severe intestinal damage, inflammation and oxidative stress. While cathepsin B (CTSB) has been implicated in these pathophysiological processes, its precise role in mediating I/R‑induced injury remains poorly understood. The present study aimed to elucidate how CTSB knockdown influences oxidative stress, inflammatory responses and the integrity of the intestinal epithelial barrier in intestinal epithelial Caco‑2 cells subjected to I/R injury. To identify key genes implicated in I/R injury, a comprehensive analysis was conducted using differential expression profiling and protein‑protein interaction network analysis of the GSE37013 dataset. To simulate I/R damage in vitro, an oxygen‑glucose deprivation/reoxygenation (OGD/R) model was employed in Caco‑2 cells. Subsequently, inflammation was induced by stimulating the cells with lipopolysaccharide (LPS) and adenosine triphosphate (ATP). To investigate the role of CTSB in this context, small interfering RNA was utilized to knock down CTSB expression. In vitro assays were then performed to evaluate NLR family pyrin domain‑containing 3 (NLRP3) inflammasome activation, oxidative stress levels, inflammatory cytokine production and cell survival. The results revealed that intestinal tissues from the I/R group in the GSE37013 dataset showed markedly higher CTSB expression, and the Caco‑2 cells subjected to OGD/R model resulted in a considerable increase in CTSB expression. However, the expression levels of tight junction proteins were enhanced, cell survival was improved and lactate dehydrogenase release was reduced by CTSB knockdown. This reduction in CTSB levels also reduced malondialdehyde levels, and alleviated oxidative stress by increasing the activities of glutathione peroxidase and superoxide dismutase. Furthermore, pro‑inflammatory cytokine production was reduced, and NLRP3 inflammasome activation was inhibited by CTSB knockdown, although a modest increase was still observed after LPS + ATP stimulation. Notably, although CTSB knockdown significantly reduced the inflammatory response, LPS + ATP stimulation still elicited a modest reversal in cytokine levels, suggesting that a CTSB‑independent pathway of inflammatory activation may exist. In conclusion, CTSB knockdown effectively mitigates I/R injury by reducing inflammation, preserving barrier integrity and alleviating oxidative stress, positioning CTSB as a promising therapeutic target. Future work should validate these findings in in vivo models and explore CTSB‑targeted therapies to improve clinical outcomes in I/R‑related diseases.

Abstract Glioblastoma (GBM), the most common malignant primary brain tumor in adults, has a median survival of 15 months and 5-year survival rate of only 6.9%. Standard of care, including radiation and chemotherapy, can induce cellular senescence in the brain. The senescence-associated secretory phenotype (SASP) significantly affects glioma microenvironment as these secreted factors exhibit both anti-and pro-tumorigenic effects. However, it is currently unknown whether senescence in the surrounding GBM microenvironment could be beneficial or detrimental to tumor outcomes. Using cell-specific proteomics, we identified upregulation of cathepsin B (CTSB) expression in patient-derived brain tumor initiating cells (BTICs) co-cultured with human fetal neural progenitor cells (NPCs). In matched patient tumor biopsies, sequencing of lateral ventricle (LV)-proximal regions revealed increased CTSB expression compared to LV-distal counterparts. Remarkably, LV-proximal GBMs induced a senescent phenotype and reduced differentiation in subventricular zone (SVZ) NPCs through CTSB secretion. We hypothesize that senescent NPCs in the SVZ contribute to a pro-tumorigenic microenvironment that promotes tumor aggressiveness in LV-proximal GBM. To model this in vitro, senescence was induced in NPCs using recombinant CTSB (100 nM) and hydrogen peroxide (250 µM, 2 hours). Treated NPCs showed increased β-galactosidase activity and increased expression of SASP factors IL-1α, IL-6, and CTSB. Senescent NPCs significantly increased BTIC migration and proliferation (p<0.05) both in co-culture and through conditioned media, suggesting this effect may be mediated by soluble factors. These findings support the hypothesis that senescent NPCs promote BTIC malignancy in LV-proximal GBM and identify CTSB as a potential mediator of this interaction.

Abstract BACKGROUND: Glioblastoma (GBM) is a highly heterogeneous and aggressive brain cancer, classified into classical (CL), proneural (PN) and mesenchymal (ME). ME GBMs are characterized by higher levels of tumor-associated macrophage (TAM) infiltration, which drives immunosuppression and tumor progression. This study investigates whether macrophage gene signatures can serve as prognostic biomarkers across GBM subtypes. METHODS: RNA-seq data from 288 GBM patients in The Cancer Genome Atlas (TCGA) were analysed. Macrophage-related gene sets were curated from MSigDB and evaluated using pairwise Gene Set Enrichment Analysis (GSEA). The gene set CUI_DEVELOPING_HEART_C8_MACROPHAGE (275 genes), derived from single-cell RNA-seq of fetal macrophages, was most enriched in ME GBMs and selected for survival analysis. Kaplan-Meier analysis using median stratification identified the five most prognostic genes, which were then evaluated using Cox regression. RESULTS: Distinct macrophage profiles were observed: ME GBMs were TAM-rich, with mixed M1/M2 characteristics; CL GBMs displayed enrichment in tissue-resident macrophage subsets (e.g. APOE+); while PN GBMs were not enriched. High expression of RETN (Resistin), LSP1 (Lymphocyte-specific protein 1) and CTSB (Cathepsin B) was significantly associated with poor survival in both univariate and multivariate Cox models across all subtypes (RETN: HR = 1.036, p = 0.0088; LSP1: HR = 1.017, p = 0.0104; CTSB: HR = 1.001, p = 0.0094). High-expression groups had shorter median survival (357-375 days vs 448-466 days) and lower 2-year overall survival (16.2-17.9% vs 30.1-32.5%). These genes contribute to TAM-driven immunosuppression: RETN dampens anti-tumor immunity, LSP1 promotes macrophage chemotaxis and CTSB facilitates invasion and immune evasion. CONCLUSION: RETN, LSP1 and CTSB are robust prognostic biomarkers in GBM. While CTSB has been linked to invasion and mesenchymal transition in gliomas, RETN and LSP1 have emerged as modulators of immunosuppression. These genes are promising candidates for TAM-targeted therapies against glioblastoma and patient prognostication across subtypes.

Background Qing-Re-Xiao-Zheng-Yi-Qi formula (QRXZYQF), based on the "Shen-Luo-Zheng-Jia" principles of traditional Chinese medicine, has been reported to reduce 24-hour urinary total protein in diabetic kidney disease (DKD) patients, slow disease progression, and improve podocyte injury. This study aims to explore the mechanisms of QRXZYQF in improving podocyte injury. Methods Diabetes was induced in male C57BL/6J mice by intraperitoneal injection of streptozotocin (STZ). After 12 weeks of QRXZYQF, blood glucose, blood urea nitrogen, serum creatinine, microalbumin, and the urinary albumin-to-creatinine ratio (UACR) were monitored. Renal pathological changes were evaluated using hematoxylin and eosin (H&E), Masson, and periodic acid–Schiff (PAS) staining. RNA sequencing (RNA-Seq) was performed to identify differences in renal mRNA expression and enrichment pathways. The involvement of autophagy–lysosomal and NOD-like receptor pathways was examined by western blotting and immunofluorescence in renal tissues and cultured podocytes. Results Following 12 weeks of QRXZYQF, renal function improved and ECM accumulation and glomerulosclerosis were markedly reduced. Subsequently, RNA-Seq analysis showed that the autophagy–lysosomal and NOD-like receptor signaling pathways were the potential pathways involved in the mechanism of QRXZYQF. Moreover, QRXZYQF reduced the levels of NLRP3, apoptosis-associated speck-like protein (ASC), as well as Caspase-1 in vitro. Furthermore, we performed interventions using the lysosomal membrane-permeabilizing agent (L-leucyl-L-leucine-O-methylester) and found that QRXZYQF inhibits NLRP3 overexpression by protecting lysosomal membranes and preventing the leakage of Cathepsin B (CB) into the cytoplasm. Conclusions QRXZYQF inhibits NLRP3-mediated podocyte pyroptosis by stabilizing lysosomal membranes, providing insights into its protective mechanism and potential therapeutic targets for DKD.

Honokiol ameliorates hepatic fibrosis by inducing lysosomal membrane permeabilization and impairing lipophagy in hepatic stellate cells.

Although antiviral therapy has improved quality of life, around 50% of people with HIV (PWH) experience neurodegeneration and cognitive decline. This is prompted in part by the migration of HIV-infected monocyte-derived macrophages (MDMs) to the brain, leading to neuronal death. Previous studies in our lab have shown that HIV-infected MDMs secrete cathepsin B (CATB), which is a pro-inflammatory neurotoxic enzyme that is reduced by the addition of cannabinoid receptor-2 (CB2R) agonist JWH-133 to cell cultures. In this study, we aimed to identify the proteins secreted (secretome) by HIV-infected macrophages exposed to JWH-133 and quantify them using tandem mass tag (TMT) mass spectrometry. Frozen 13-day MDM supernatants from (1) an MDM negative control; (2) HIV+MDM, and (3) HIV+MDM-JWH-133 were compared in triplicate by mass spectrometry (LC/MS/MS) and analyzed for protein identification. Subsequently, the same samples were labeled by TMT labeling and quantified by LC/MS/MS. After a database search, 528 proteins were identified from all groups. Thereafter, proteins with more than three unique peptides and more than 10% coverage were selected for protein identification. Venn diagrams revealed one unique protein secreted by MDM-HIV, 10 unique proteins in HIV+MDM-JWH-133, and 15 common proteins in the three groups. CATB was unique to HIV+MDM. HIV+MDM exposed to JWH-133 showed proteins related to metabolism, cell organization, antiviral activity, and stress response. TMT analysis revealed 1454 proteins with abundance for statistical analysis based on FC ≥ |1.5| and p-value ≤ 0.05, of which Ruvb-like 1 and Hornerin decreased significantly with JWH-133 treatment. Both proteins stimulate HIV replication. In addition, HIV infection upregulated proteins associated with pathways of viral latency that were inhibited by JWH-133. In conclusion, JWH-133 treatment in HIV-infected macrophages leads to the secretion of antiviral host factors and decreases the secretion of proviral, inflammatory, and neurotoxic host factors.

Giardia duodenalis (G. duodenalis) is a prevalent intestinal protozoan parasite responsible for causing diarrhea, particularly in children and travelers. Although many infections are asymptomatic, they can result in severe malnutrition and cognitive developmental impairments in pediatric populations. Giardia lamblia virus (GLV) is a protozoan virus that specifically infects G. duodenalis. This virus is characterized by its non-segmented, non-enveloped double-stranded RNA structure and contains essential proteins such as RNA-dependent RNA polymerase (RdRp) and capsid protein (GLVCP). While the interactions between RdRp and host proteins have been extensively investigated, the function of GLVCP remains largely unexplored. In this study, we employed various methodologies, including mass spectrometry, co-immunoprecipitation (Co-IP), and bimolecular fluorescence complementation (BiFC), to identify and characterize the interactions between GLVCP and host proteins of G. duodenalis. Furthermore, we validated these interactions using CRISPR/dCas9 gene editing and protein overexpression techniques. Our research revealed that an uncharacterized protein (UCP) containing a glycosyltransferase-stabilizing (Gtf2) domain interacts with GLVCP. Under GLV influence, UCP modulates GlcNAc-mediated O-glycosylation and regulates multiple proteins that are involved in different pathways, such as ABC transporters, Malate Dehydrogenase (MDH), and cathepsin B (CTSB), creating a favorable intracellular environment to viral survival. Our findings provide crucial insights into the GLV life cycle and underscore the intricate interactions between the parasite and the virus. These results could inform the development of novel strategies for controlling Giardia infections and their associated diseases.IMPORTANCEOur research has elucidated novel regulatory mechanisms between GLV and G. duodenalis, highlighting the complex interactions involving GLVCP and a host protein (UCP, a characterized protein containing a Gtf2 domain). This interaction enhances host GlcNAc-mediated O-glycosylation, inhibits ATP transport, and promotes the cleavage of GLVCP by cathepsin B, thereby facilitating the uncoating and release of the viral genome. These findings deepen our understanding of the GLV life cycle and fill gaps in our knowledge of the intricate dynamics between protozoan viruses and their hosts, providing valuable insights for the development of innovative strategies to control Giardia infections.

Recent studies show that methyltransferase-like 1 (METTL1)-mediated internal messenger ribonucleic acid (mRNA) N7-methylguanosine (m7G) modification has a unique role in cancer metastasis. Here, we aimed to uncover the role of METTL1-mediated internal mRNA m7G in controlling fibroblast-like synoviocytes' (FLSs') functions in rheumatoid arthritis (RA). FLSs were separated from patients with active established RA. Western blot, immunohistochemistry, and immunofluorescence were used to measure protein expression in synovium. The Boyden chamber was used to detect cell migration and invasion. m7G RNA immunoprecipitation sequencing was performed to seek the potential target of METTL1. Dual-luciferase reporter gene assay was used to investigate the m⁷G-dependent regulation of cathepsin B (CTSB) by METTL1. The protein translation efficiency was detected by polysome profiling. METTL1 heterozygous knockout or intra-articular injection of METTL1 short hairpin ribonucleic acid adenovirus (Adv-shRNA-METTL1) was used to inhibit arthritis in RA models. We observed increased levels of METTL1 and internal mRNA m7G in FLSs and synovial tissues from patients with RA. METTL1 knockdown or overexpression decreased or increased the migration and invasion of RA FLSs. Synovial METTL1 level was positively correlated with the disease activity score on 28 joints-erythrocyte sedimentation rate scores in patients with RA. METTL1 knockdown in vivo mitigated the severity of arthritis in RA animal models. Mechanistically, we probed that METTL1 promotes the aggressive action of RA FLSs through regulating the translation efficiency of the internal mRNA m7G modification of CTSB. CTSB knockdown also suppressed the aggression of RA FLSs. Our findings reveal an important role of METTL1-mediated internal mRNA m7G modification in promoting synovial aggression of RA, suggesting that METTL1 might be a potential target for therapy of RA, even other dysregulated FLS-associated diseases.

Aflatoxin B1 (AFB1), a potent mycotoxin, induces nephrotoxicity through previously unrecognized crosstalk between pyroptosis and apoptosis. Using in vivo and in vitro renal injury models, we demonstrate that AFB1 impairs mitophagy, leading to an excessive level of reactive oxygen species (ROS) accumulation. This ROS surge triggers lysosomal membrane permeabilization (LMP) and cathepsin B (CTSB)-dependent activation of the NOD-like receptor protein 3 (NLRP3) inflammasome, initiating caspase-1-mediated pyroptosis via gasdermin D N-terminal (GSDMD-N) pore formation. Importantly, AFB1 also induces cardiolipin translocation to the mitochondrial outer membrane, where pyroptosis-derived GSDMD-N is recruited to form mitochondrial pores. This results in cytochrome c (Cyt-c) release and activation of a caspase-dependent noncanonical apoptotic cascade distinct from the classical apoptotic pathway. These findings establish GSDMD-N-mediated mitochondrial damage as a molecular bridge linking pyroptosis to apoptosis in AFB1 nephrotoxicity and highlight GSDMD-N inhibition as a promising therapeutic strategy. Given AFB1's persistence and bioaccumulation in the food chain, these mechanistic insights provide a molecular basis for developing targeted interventions to mitigate its health risks in agricultural production and food safety.

Multi-omics analysis of ketogenic diet-mediated neural repair in spinal cord injury: Targeting of lysosomal autophagy through CTSB/LAMP2 regulation.

Low-grade chronic inflammatory stimulation alleviates α‑syn accumulation in Parkinson's disease by activating autophagy to promote neuronal survival in the Thy1-h[A30P]α-syn mouse model.

Screening and validation of Galectin3-interacting proteins from Japanese flounder (Paralichthys olivaceus).

The progression and mechanisms of drug resistance in prostate cancer are highly complex, with the ferroptosis pathway playing a critical role. We utilized multi-omics Mendelian randomization (MR) to assess the genetic causal link between ferroptosis gene/protein expression and prostate cancer, investigating potential mediation by 731 immune cell types. Furthermore, differential expression analysis, immune infiltration analysis, single-cell RNA sequencing, gene set enrichment analysis (GSEA), and drug prediction were integrated for multidimensional validation and mechanistic insight. Our results identified cathepsin B (CTSB) as a key causal risk factor associated with iron death in the development of prostate cancer (odds ratio (OR) > 1, p < 0.01). Colocalization analysis (SNP.PP.H4 > 0.95) ruled out confounding biases. Mediation MR analysis revealed that CTSB partially mediates its carcinogenic effects by regulating various immune cells, such as PD-L1 + monocytes and CD45 + T cells (OR > 1, p < 0.05). Further analysis indicated that CTSB gene/protein expression was highly expressed in normal prostate basal epithelial cells and myeloid cells, while it was downregulated in tumor tissues and neoplastic epithelial cells (p < 0.05). Notably, its expression was positively correlated with the infiltration of multiple immune cell types (cor > 0, p < 0.05). GSEA demonstrated that high CTSB expression was significantly enriched in pro-cancer pathways, including epithelial-mesenchymal transition, angiogenesis, inflammatory response, and apoptosis (normalized enrichment score (NES) > 2, false discovery rate (FDR) < 0.001). Drug prediction analyses suggested that targeting CTSB (e.g., with bortezomib) in combination with immunotherapy may represent a novel therapeutic strategy. This study provides the first evidence of the causal role of iron death-immune interactions in prostate cancer, offering new targets for precision treatment.

Cathepsin B (CTSB), a lysosomal cysteine protease, plays pivotal roles in cellular homeostasis and pathology, including cancer progression. This study investigates the regulatory interplay between CTSB and Stefin A (STFA), an endogenous inhibitor of cysteine proteases, in renal and prostate cancer cells. Using plasmid-based overexpression and silencing systems, we demonstrated that overexpressing STFA significantly reduces CTSB activity and protein levels, while silencing STFA leads to elevated CTSB activity and expression in cancer cells but not in non-cancerous cells (embryonic kidney cells-Hek293T and endothelial cells-EA.hy926). Furthermore, STFA modulates the subcellular distribution of CTSB, with STFA overexpression reducing nuclear CTSB levels and silencing inducing cytoplasmic accumulation in cancer cells. Colocalization analysis confirms a direct interaction between STFA and CTSB, highlighting the spatial coordination necessary for effective protease inhibition. These findings underscore the critical role of the CTSB-STFA axis in maintaining proteolytic balance and suggest potential therapeutic strategies targeting this interaction in renal carcinoma and other cancers.