N-glycosylated GPNMB ligand independently activates mutated EGFR signaling and promotes metastasis in NSCLC

Glycoprotein nonmetastatic melanoma protein B is regulated by hepatic peroxisome proliferator-activated receptor γ in liver steatosis

Hepatic glycoprotein nonmetastatic melanoma protein B (GPNMB) and nuclear receptor peroxisome proliferator-activated receptor gamma (PPARγ) play essential roles in lipid metabolism. This study aimed to examine the molecular mechanism through which PPARγ controls GPNMB expression in liver steatosis. A microarray database was used to examine the gene expression patterns associated with fatty liver in type 2 diabetic leptin-deficient (ob/ob) mice, as well as in patients with non-alcoholic fatty liver disease (NAFLD) and advanced NAFLD. GPNMB expression significantly increased in the fatty livers of humans and mice. Elevated Gpnmb expression was notably reduced by liver-specific Pparγ knockout (PPARγLKO) in ob/ob mice. Similarly, alcohol-fed mice had increased hepatic Gpnmb levels. Transcriptomic analysis of the human liver samples revealed that Gpnmb expression was markedly higher in patients with fatty liver diseases, including those with NAFLD and alcoholic fatty liver disease, than in controls. Reporter and electrophoretic mobility shift assays confirmed that PPARγ directly enhances Gpnmb transcription via three functional PPARγ-responsive elements within the first intron. In conclusion, these findings suggest that Gpnmb is a novel PPARγ target in liver steatosis.

GPNMB disrupts SNARE complex assembly to maintain bacterial proliferation within macrophages

Xenophagy plays a crucial role in restraining the growth of intracellular bacteria in macrophages. However, the machinery governing autophagosome‒lysosome fusion during bacterial infection remains incompletely understood. Here, we utilize leprosy, an ideal model for exploring the interactions between host defense mechanisms and bacterial infection. We highlight the glycoprotein nonmetastatic melanoma protein B (GPNMB), which is highly expressed in macrophages from lepromatous leprosy (L-Lep) patients and interferes with xenophagy during bacterial infection. Upon infection, GPNMB interacts with autophagosomal-localized STX17, leading to a reduced N-glycosylation level at N296 of GPNMB. This modification promotes the degradation of SNAP29, thus preventing the assembly of the STX17-SNAP29-VAMP8 SNARE complex. Consequently, the fusion of autophagosomes with lysosomes is disrupted, resulting in inhibited cellular autophagic flux. In addition to Mycobacterium leprae, GPNMB deficiency impairs the proliferation of various intracellular bacteria in human macrophages, suggesting a universal role of GPNMB in intracellular bacterial infection. Furthermore, compared with their counterparts, Gpnmbfl/fl Lyz2-Cre mice presented decreased Mycobacterium marinum amplification. Overall, our study reveals a previously unrecognized role of GPNMB in host antibacterial defense and provides insights into its regulatory mechanism in SNARE complex assembly.

GPNMB and ATP6V1A interact to mediate microglia phagocytosis of multiple types of pathological particles

Pronounced elevation of glycoprotein non-metastatic melanoma B (GPNMB) is a common phenomenon in a variety of brain diseases, but the expression patterns, functions, and molecular signaling of GPNMB have not been well studied. Here, we showed that pathological factors, including neuronal degeneration caused by seizures, caspase-3-induced neuronal apoptosis, neuronal debris, and β-amyloid, induced "on-demand" GPNMB expression in hippocampal microglia. Genetic ablation of GPNMB did not affect acute seizures but worsened chronic epileptogenesis. We found that GPNMB functioned in phagocytosis, deficiency of which resulted in defects in both phagocytic engulfment and degradation. GPNMB could be internalized into cells, where it wrapped engulfed pathogenic particles and presented them to lysosomes through interaction with lysosomal vacuolar-type proton ATPase catalytic subunit A (ATP6V1A). Activating ATP6V1A was able to rescue GPNMB-deficiency-caused phagocytosis impairment. Thus, microglial GPNMB-ATP6V1A might be a common treatment target of a batch of chronic neurological disorders, and clearing the degenerative neurons might be more valuable than reserving them to protect the brain.

MSC-sEVs exacerbate senescence by transferring bisecting GlcNAcylated GPNMB

BACKGROUND

The senescence of bone marrow mesenchymal stem cells (BMMSCs) is increasingly recognized as a critical factor contributing to the pathophysiology of age-related diseases. Recent studies suggest that small extracellular vesicles (sEVs) derived from the serum of elderly individuals may play a pivotal role in promoting BMMSC senescence. Glycoprotein non-metastatic melanoma protein B (GPNMB), a type I transmembrane glycoprotein, is upregulated during cellular senescence and can regulate stem cell ageing. However, the precise mechanisms by which GPNMB influences BMMSCs senescence remain poorly understood. Understanding this relationship could provide valuable insights into therapeutic strategies for enhancing BMMSCs function and mitigating age-related degeneration.

METHODS

In this study, we conducted comprehensive in vitro experiments to elucidate the effects of sEVs isolated from the serum of elderly donors on the senescence of BMMSCs. We employed advanced proteomic analysis to quantify the expression levels of GPNMB in both BMMSCs and sEVs. Statistical methods were utilized to investigate the correlations between GPNMB expression, glycosylation modifications, and established senescence markers.

RESULTS

Our findings demonstrate a robust positive correlation between the expression of GPNMB in BMMSCs and sEVs and the induction of cellular senescence. Notably, we observed that elevated levels of GPNMB, particularly those bearing bisecting N-acetylglucosamine (GlcNAc) modifications, significantly enhance the senescent phenotype of BMMSCs. Furthermore, we identified the bisecting GlcNAc modification at the Asn 249 residue of GPNMB as a critical determinant for its senescence-promoting function.

CONCLUSIONS

This study elucidates the substantial role of sEVs derived from mesenchymal stem cells in exacerbating BMMSC senescence through mechanisms that are critically dependent on the presence of bisecting GlcNAcylated GPNMB. These insights emphasize the necessity of targeting glycosylation modifications of GPNMB in the design of novel senolytic therapies aimed at mitigating cellular ageing and its associated pathologies.

Diverse perspectives on proteomic posttranslational modifications to address EGFR-TKI resistance in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is the main histological subtype of lung cancer. For locally advanced and advanced NSCLC, epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI)-targeted therapy has been the first choice for NSCLC patients with EGFR mutations. TKIs, as targeted drugs, inhibit kinase activity and autophosphorylation by competitively binding to the ATP binding site of the EGFR tyrosine kinase domain, which blocks the signal transduction mediated by EGFR and thus inhibits the proliferation of tumor cells. However, drug resistance to TKIs is inevitable. EGFR is also a highly glycosylated receptor tyrosine kinase, and a wide range of crosstalk occurs between phosphorylation and glycosylation. Therefore, can the phosphorylation state be altered by glycosylation to improve drug resistance? In this review, we summarize phosphorylation, glycosylation and the crosstalk between these processes as well as the current research status and methods. We also summarize the autophosphorylation and glycosylation sites of the EGFR protein and their crosstalk. By exploring the relationship between EGFR glycosylation and autophosphorylation in targeted TKI therapy, we find that research on EGFR glycosylation is crucial for targeted NSCLC treatment and will become a research direction for identifying potential targets related to regulating TKI drug sensitivity.

Identification of GPNMB in endometrial cancer based on pan-cancer analysis and in vitro validation

BACKGROUND

GPNMB is a type I transmembrane protein, and emerging evidence supports the relationship between GPNMB and cancers.

OBJECTIVE

Through a comprehensive pan-cancer analysis, we examined the expression levels, prognostic significance, and mutation profiles of GPNMB in different cancer types. Subsequently, utilizing in vitro experiments, we elucidated the impact of GPNMB in endometrial cancer (EC).

METHODS

TIMER2, GEPIA2, UALCAN and cBioPortal were used to analyze the expression pattern, prognostic values, and mutation status of GPNMB. HEC-1B and Ishikawa cells were used to conduct in vitro analyses of GPNMB overexpression. GeneMANIA and TIMER2 were used to evaluate the potential functions and correlations between GPNMB expression and tumor-infiltrating immune cells in EC.

RESULTS

GPNMB was found to be highly expressed in multiple cancers, where it was associated with poor prognosis. Additionally, GPNMB was downregulated at both mRNA and protein levels in EC. Overexpression of GPNMB inhibited the proliferation, migration, and invasion of HEC-1B and Ishikawa cells. Functional analysis showed that GPNMB was enriched in pathways associated with regulation of plasma lipoprotein particle levels. The expression of GPNMB was positively connected with B cell, CD8+ T cell, CD4+ T cell, Macrophage, Neutrophil, and Dendritic cell levels.

CONCLUSION

Through pan-cancer analysis, we identified the antitumor effect of GPNMB in EC and predicted the potential mechanisms between GPNMB expression and EC.

GPNMB Expression Associates with Inferior Prognosis in Patients with Small Cell Lung Cancer

Purpose: Small cell lung cancer (SCLC) is widely recognized for its propensity for early and frequent metastases, which contribute to its status as a refractory malignancy. While the high expression of GPNMB in SCLC is well-documented, the precise correlation between GPNMB expression and the prognosis of SCLC remains undetermined. Methods: HTG Edge-seq was used to screen the differential gene expression between primary SCLC lesions and paired metastatic lymph nodes (LN). The plasma concentration of GPNMB was measured using enzyme-linked immunosorbent assay (ELISA). The relationship between GPNMB concentration and clinical characteristics, as well as overall survival (OS) was assessed. One-to-one propensity score matching (PSM) was performed to reduce bias from confounding factors between groups. The invasive, migratory, proliferative, and apoptotic abilities of SCLC cells were evaluated using migration and matrigel invasion assays, CCK8 assay and flow cytometry respectively. Results: GPNMB exhibited a significant up-regulation in LN compared to primary SCLC lesions as determined by HTG Edge-seq. Furthermore, patients with extensive disease demonstrated a significantly elevated plasma GPNMB concentration compared to those with local disease (P = 0.043). Additionally, patients with a high baseline plasma GPNMB level exhibited a shorter OS (10.32 vs. 16.10 months, P = 0.0299). Following PSM analysis, the statistical significance of the difference between the two groups persisted (9.43 vs. 15.27 months, P = 0.0146). Notably, both univariate and multivariate analyses confirmed that higher expression of GPNMB served as an independent biomarker for OS before PSM (P = 0.033, HR = 2.304) and after PSM (P = 0.003, HR = 6.190). Additionally, our study revealed that the inhibition of GPNMB expression through the use of siRNA effectively diminished the metastatic and proliferative capabilities of SCLC. Furthermore, this inhibition resulted in an enhanced ability to induce apoptosis. Conclusions: In light of our findings, it can be inferred that the expression of GPNMB is linked to metastasis and an unfavorable prognosis, thus suggesting its potential as a novel therapeutic target in the treatment of SCLC.

Variant Analysis of miRNA Regulatory Genes in 35 Sporadic Lung Carcinoma Tumors

Lung cancer is one of the cancer types with the highest mortality worldwide. The most frequently mutated genes known to be clinically important in lung cancers are EGFR, BRAF, and KRAS genes. Therefore, the therapeutic agents developed are directed against variants that cause over-activation of the EGFR-KRAS-BRAF-BRAF-MEK/ERK signalling pathway. However, different responses of patients to Tyrosine Kinase Inhibitors (TKIs) suggest that new prognostic biomarkers should be defined and epigenetic mechanisms may be related to this situation.

METHODS

In this study, sequence analyses of AGO2, DICER, and DROSHA genes involved in miRNA biogenesis and EGFR, KRAS, and BRAF genes were performed in 35 patients with sporadic lung cancer.

RESULTS

We found variations in genes involved in miRNA biogenesis that have not been previously reported in the literature. In addition, we found 4 different variants in the EGFR gene that have been described in the literature. In addition, a statistically significant association was found between the presence of mutations in at least one of the genes involved in miRNA biogenesis and metastasis (p:0.02).

CONCLUSIONS

In conclusion, genomic dysregulation of key miRNA biogenesis genes may be one of the possible reasons for the differential response of patients to therapeutic agents and the development of metastasis in EGFR wild type tumours.

Single-cell transcriptome sequencing-based analysis: probing the mechanisms of glycoprotein NMB regulation of epithelial cells involved in silicosis

Chronic exposure to silica can lead to silicosis, one of the most serious occupational lung diseases worldwide, for which there is a lack of effective therapeutic drugs and tools. Epithelial mesenchymal transition plays an important role in several diseases; however, data on the specific mechanisms in silicosis models are scarce. We elucidated the pathogenesis of pulmonary fibrosis via single-cell transcriptome sequencing and constructed an experimental silicosis mouse model to explore the specific molecular mechanisms affecting epithelial mesenchymal transition at the single-cell level. Notably, as silicosis progressed, glycoprotein non-metastatic melanoma protein B (GPNMB) exerted a sustained amplification effect on alveolar type II epithelial cells, inducing epithelial-to-mesenchymal transition by accelerating cell proliferation and migration and increasing mesenchymal markers, ultimately leading to persistent pulmonary pathological changes. GPNMB participates in the epithelial-mesenchymal transition in distant lung epithelial cells by releasing extracellular vesicles to accelerate silicosis. These vesicles are involved in abnormal changes in the composition of the extracellular matrix and collagen structure. Our results suggest that GPNMB is a potential target for fibrosis prevention.

Human Papillomavirus Infection and EGFR Exon 20 Insertions in Sinonasal Inverted Papilloma and Squamous Cell Carcinoma

This study aimed to clarify the roles of high-risk human papillomavirus (HR-HPV) infection and epidermal growth factor receptor (EGFR) exon 20 mutations in sinonasal inverted papilloma (IP) and sinonasal squamous cell carcinoma (SNSCC). Samples were collected from 20 cases with IP, 7 with IP and squamous cell carcinoma (IP-SCC), and 20 with SNSCC and examined for HPV infection and EGFR exon 20 mutations. Low- or high-risk HPV DNA was observed in 25% of IP, 57.1% of IP-SCC, and 35% of SNSCC cases. Transcriptionally active HR-HPV infections in IP-SCC and SNSCC, accompanied by p16 overexpression, were observed in 28.5% and 25% of cases, respectively. Heterozygous EGFR exon 20 amino acid insertions (ex20ins), located between amino acids 768-774, were observed in 45% of IP, 28.5% of IP-SCC, and 0% of SNSCC and chronic sinusitis cases. EGFR phosphorylation sites were located at tyrosine (Y) 845, Y1068, Y1086, and Y1197 and induced PI3K/AKT/mTOR activation. The phosphorylation pattern of EGFR with ex20ins resembled that of HPV-related SNSCC and oropharyngeal cancer. The transcriptionally active HR-HPV infection and ex20ins might be responsible for the pathogenesis of IP-SCC cases with different fashions. Since IP-SCC might be a multifactorial disease, further investigation is needed to understand IP-SCC etiology.

Construction of a prognostic model for radical esophagectomy based on immunohistochemical prognostic markers combined with clinicopathological factors

Esophageal squamous cell carcinoma (ESCC) has a poor prognosis and lacks effective biomarkers to evaluate prognosis and treatment. Glycoprotein nonmetastatic melanoma protein B (GPNMB) is a protein highly expressed in ESCC tissues screened by isobaric tags for relative and absolute quantitation proteomics, which has significant prognostic value in a variety of malignant tumors, but its relationship with ESCC remains unclear. By immunohistochemical staining of 266 ESCC samples, we analyzed the relationship between GPNMB and ESCC. To explore how to improve the ability of ESCC prognostic assessment, we established a prognostic model of GPNMB and clinicopathological features. The results suggest that GPNMB expression is generally positive in ESCC tissues and is significantly associated with poorer differentiation, more advanced American Joint Council on Cancer (AJCC) stage, and higher tumor aggressiveness (P < .05). Multivariate Cox analysis indicated that GPNMB expression was an independent risk factor for ESCC patients. A total of 188 (70%) patients were randomly selected from the training cohort and the four variables were automatically screened by stepwise regression based on the AIC principle: GPNMB expression, nation, AJCC stage and nerve invasion. Through the weighted term, we calculate the risk score of each patient, and by drawing the receiver operating characteristic curve, we show that the model has good prognostic evaluation performance. The stability of the model was verified by test cohort. Conclusion: GPNMB is a prognostic marker consistent with the characteristics of tumor therapeutic targets. For the first time, we constructed a prognostic model combining immunohistochemical prognostic markers and clinicopathological features in ESCC, which showed higher prognostic efficacy than AJCC staging system in predicting the prognosis of ESCC patients in this region.

Glycoprotein non-metastatic melanoma B interacts with epidermal growth factor receptor to regulate neural stem cell survival and differentiation

The functional recovery following spinal cord injury (SCI) remains a challenge clinically. Among the proteins interacted with the glycoprotein non-metastatic melanoma B (GPNMB), epidermal growth factor receptor (EGFR) during activation is able to promote the proliferation of neural stem cells (NSCs) in the spinal cord. We investigated the roles of GPNMB and EGFR in regulating the survival and differentiation of the NSCs. By overexpression and short-hairpin RNA-mediated knockdown of GPNMB in the NSCs, GPNMB promoted cell viability and differentiation by increasing the expressions of βIII tubulin and CNPase (2',3'-cyclic nucleotide 3-phosphodiesterase). Using co-immunoprecipitation, we found that EGFR interacted with GPNMB. Furthermore, EGFR had a similar effect as GPNMB on promoting cell viability and differentiation. Overexpression of EGFR reversed the decrease in viability and differentiation caused by the knockdown of GPNMB, and vice versa. Last but not least, we tested the effect of GPNMB and EGFR on several intracellular pathways and found that GPNMB/EGFR modulated the phosphorylated (p)-c-Jun N-terminal kinase (JNK)1/2/JNK1/2 ratio and the p-nuclear factor κB (NF-κB p65)/NF-κB p65 ratio. In sum, our findings demonstrate the interaction between GPNMB and EGFR that regulates cell bioprocesses, with the hope to provide a new strategy of SCI therapy.

Prognostic Value of GPNMB, EGFR, p-PI3K, and Ki-67 in Patients with Esophageal Squamous Cell Carcinoma

Background. GPNMB is a newly discovered tumour-promoting factor that may promote tumour cell progression by activating the PI3K/AKT pathway by EGFR. However, there are insufficient studies about GPNMB in ESCC. This study investigated the relationship between GPNMB and EGFR/PI3K pathway genes in ESCC. Methods. The expression levels of GPNMB, EGFR, p-PI3K, and Ki-67 were examined using immunohistochemistry. Statistical analysis was done by SPSS 22.0 and R. Results. GPNMB mRNA expression is higher in ESCC compared with paracancerous tissues. The expression of EGFR, PIK3CA, PIK3CB, and AKT1 was increased in GPNMB upregulated samples. GPNMB expression was positively correlated with EGFR, p-PI3K, and Ki-67 expression. GPNMB was expressed higher in the AJCC III stage, lymph node metastasis, and moderately poorly differentiated patients. EGFR was higher expressed in patients with vascular invasion; p-PI3K expression in Kazak was higher than that in Han; Ki-67 expression was higher in $\text{tumour}\text{size}\ge 3\text{cm}$ . Patients with high expression of GPNMB, p-PI3K, and Ki-67 had worse OS. p-PI3K, Ki-67, nerve invasion, and lymphatic metastasis were independent risk factors, and postoperative adjuvant therapy was a protective factor in ESCC. Conclusion. As a tumour-promoting factor, GPNMB is expected to be a potential target for ESCC.

Abnormal sialylation and fucosylation of saliva glycoproteins: Characteristics of lung cancer-specific biomarkers

Dysregulated surface glycoproteins play an important role in tumor cell proliferation and progression. Abnormal glycosylation of these glycoproteins may activate tumor signal transduction and lead to tumor development. The tumor microenvironment alters its molecular composition, some of which regulate protein glycosylation biosynthesis. The glycosylation of saliva proteins in lung cancer patients is different from healthy controls, in which the glycans of cancer patients are highly sialylated and hyperfucosylated. Most studies have shown that O-glycans from cancer are truncated O-glycans, while N-glycans contain fucoses and sialic acids. Because glycosylation analysis is challenging, there are few reports on how glycosylation of saliva proteins is related to the occurrence or progression of lung cancer. In this review, we discussed glycoenzymes involved in protein glycosylation, their changes in tumor microenvironment, potential tumor biomarkers present in body fluids, and abnormal glycosylation of saliva or lung glycoproteins. We further explored the effect of glycosylation changes on tumor signal transduction, and emphasized the role of receptor tyrosine kinases in tumorigenesis and metastasis.

N-glycosylated GPNMB ligand independently activates mutated EGFR signaling and promotes metastasis in NSCLC

Lung cancer is the leading cause of cancer‐related death worldwide. As well as the identified role of epidermal growth factor receptor (EGFR), its association with driver mutations has improved the therapeutics for patients with lung cancer harboring EGFR mutations. These patients usually display shorter overall survival and a higher tendency to develop distant metastasis compared with those carrying the wild‐type EGFR. Nevertheless, the way to control mutated EGFR signaling remains unclear. Here, we performed membrane proteomic analysis to determine potential components that may act with EGFR mutations to promote lung cancer malignancy. Expression of transmembrane glycoprotein non‐metastatic melanoma protein B (GPNMB) was positively correlated with the status of mutated EGFR in non‐small‐cell lung cancer (NSCLC). This protein was not only overexpressed but also highly glycosylated in EGFR‐mutated, especially EGFR‐L858R mutated, NSCLC cells. Further examination showed that GPNMB could activate mutated EGFR without ligand stimulation and could bind to the C‐terminus of EGFR, assist phosphorylation at Y845, turn on downstream STAT3 signaling, and promote cancer metastasis. Moreover, we also found that Asn134 (N134) glycosylation of GPNMB played a crucial role in this ligand‐independent regulation. Depleting N134‐glycosylation on GPNMB could dramatically inhibit binding of GPNMB to mutated EGFR, blocking its downstream signaling, and ultimately inhibiting cancer metastasis in NSCLC. Clarifying the role of N‐glycosylated GPNMB in regulating the ligand‐independent activation of mutated EGFR may soon give new insight into the development of novel therapeutics for NSCLC.