G protein pathway suppressor 2 suppresses gastric cancer by destabilizing epidermal growth factor receptor

Sculponeatin A induces mitochondrial dysfunction in non-small cell lung cancer through WWP2-mediated degradation of mitochondrial STAT3

BACKGROUND AND PURPOSE

The phosphorylation of signal transducer and activator of transcription 3 (STAT3) monomer at S727 promotes its mitochondrial localisation and regulates mitochondrial function, thus exerting a protective effect on tumour cells. However, no inhibitor drugs targeting mitochondrial STAT3 (mitoSTAT3) or S727-STAT3 phosphorylation have been identified. Here, we report a novel diterpenoid extracted from Isodon sculponeatus, sculponeatin A (sptA), induces mitochondrial dysfunction in non-small cell lung cancer (NSCLC) by targeting mitoSTAT3 degradation.

EXPERIMENTAL APPROACH

xCELLigence real-time cell analysis assay and high-content analysis were performed to measure cytotoxicity. Mitochondrial function was assessed by transmission electron microscopy, mitochondrial permeability transition pore opening and Seahorse cellular flux assays. The effects of sptA on the upstream signalling pathway of mitochondrial dysfunction were measured by Western blot, gene alterations and other approaches. Immunofluorescence and live cell imaging were performed to visualise the expression and position of mitoSTAT3. Nude mice and zebrafish were modelled with subcutaneous xenografts. Pharmacokinetics of sptA were examined in rats. Drug toxicity was evaluated in zebrafish.

KEY RESULTS

sptA inhibited mitochondrial respiration in NSCLC cells. sptA induced mitochondrial dysfunction by promoting the degradation of mitoSTAT3. sptA promoted WW domain containing E3 ubiquitin protein ligase 2 (WWP2)-mediated ubiquitination and degradation of mitoSTAT3 through direct binding. sptA inhibited tumour growth in vivo. Evaluation of drug toxicity in zebrafish showed that overdose of sptA may cause heart damage.

CONCLUSIONS AND IMPLICATIONS

These findings suggest that pharmacological targeting the degradation of mitoSTAT3 by sptA may provide therapeutic benefits against NSCLC.

Pan-cancer analysis of Methyltransferase-like 16 (METTL16) and validated in colorectal cancer

Human Methyltransferase-like 16(METTL16) is an independent N6-methyladenosine (m6A) methyltransferase. Previous studies have proven METTL16 been linked with some types of cancers. However, comparative studies of the relevance of METTL16 across diverse tumors remain sparse. We comprehensively investigated the effect of METTL16 expression on tumor prognosis across human malignancies by analyzing multiple cancer-related databases like Tumor Immune Estimation Resource (TIMER) and human protein atlas (HPA). Bioinformatics data indicated that METTL16 was overexpressed in most of these human malignancies and was significantly associated with the prognosis of patients with cancer, especially in colorectal cancer (CRC). Subsequently, In vitro experiments, the utility of METTL16 that downregulation of its expression could result in reduced proliferation and migration of CRC cells. Our findings reveal novel insights into METTL16 expression and its biological functions in diverse cancer types, indicating that METTL16 could serve as a prognostic biomarker and plays an important role in colorectal cancer.

G protein pathway suppressor 2 suppresses aerobic glycolysis through RACK1-mediated HIF-1α degradation in breast cancer

Aerobic glycolysis has been recognized as a hallmark of human cancer. G protein pathway suppressor 2 (GPS2) is a negative regulator of the G protein-MAPK pathway and a core subunit of the NCoR/SMRT transcriptional co-repressor complex. However, how its biological properties intersect with cellular metabolism in breast cancer (BC) development remains poorly elucidated. Here, we report that GPS2 is low expressed in BC tissues and negatively correlated with poor prognosis. Both in vitro and in vivo studies demonstrate that GPS2 suppresses malignant progression of BC. Moreover, GPS2 suppresses aerobic glycolysis in BC cells. Mechanistically, GPS2 destabilizes HIF-1α to reduce the transcription of its downstream glycolytic regulators (PGK1, PGAM1, ENO1, PKM2, LDHA, PDK1, PDK2, and PDK4), and then suppresses cellular aerobic glycolysis. Notably, receptor for activated C kinase 1 (RACK1) is identified as a key ubiquitin ligase for GPS2 to promote HIF-1α degradation. GPS2 stabilizes the binding of HIF-1α to RACK1 by directly binding to RACK1, resulting in polyubiquitination and instability of HIF-1α. Amino acid residues 70-92 aa of the GPS2 N-terminus bind RACK1. A 23-amino-acid-long GPS2-derived peptide was developed based on this N-terminal region, which promotes the interaction of RACK1 with HIF-1α, downregulates HIF-1α expression and significantly suppresses BC tumorigenesis in vitro and in vivo. In conclusion, our findings indicate that GPS2 decreases the stability of HIF-1α, which in turn suppresses aerobic glycolysis and tumorigenesis in BC, suggesting that targeting HIF-1α degradation and treating with peptides may be a promising approach to treat BC.

Inhibition of K63 ubiquitination by G-Protein pathway suppressor 2 (GPS2) regulates mitochondria-associated translation

G-Protein Pathway Suppressor 2 (GPS2) is an inhibitor of non-proteolytic K63 ubiquitination mediated by the E2 ubiquitin-conjugating enzyme Ubc13. Previous studies have associated GPS2-mediated restriction of ubiquitination with the regulation of insulin signaling, inflammatory responses and mitochondria-nuclear communication across different tissues and cell types. However, a detailed understanding of the targets of GPS2/Ubc13 activity is lacking. Here, we have dissected the GPS2-regulated K63 ubiquitome in mouse embryonic fibroblasts and human breast cancer cells, unexpectedly finding an enrichment for proteins involved in RNA binding and translation on the outer mitochondrial membrane. Validation of selected targets of GPS2-mediated regulation, including the RNA-binding protein PABPC1 and translation factors RPS1, RACK1 and eIF3M, revealed a mitochondrial-specific strategy for regulating the translation of nuclear-encoded mitochondrial proteins via non-proteolytic ubiquitination. Removal of GPS2-mediated inhibition, either via genetic deletion or stress-induced nuclear translocation, promotes the import-coupled translation of selected mRNAs leading to the increased expression of an adaptive antioxidant program. In light of GPS2 role in nuclear-mitochondria communication, these findings reveal an exquisite regulatory network for modulating mitochondrial gene expression through spatially coordinated transcription and translation.

The role of CBL family ubiquitin ligases in cancer progression and therapeutic strategies

The CBL (Casitas B-lineage lymphoma) family, as a class of ubiquitin ligases, can regulate signal transduction and activate receptor tyrosine kinases through various tyrosine kinase-dependent pathways. There are three members of the family: c-CBL, CBL-b, and CBL-c. Numerous studies have demonstrated the important role of CBL in various cellular pathways, particularly those involved in the occurrence and progression of cancer, hematopoietic development, and regulation of T cell receptors. Therefore, the purpose of this review is to comprehensively summarize the function and regulatory role of CBL family proteins in different human tumors, as well as the progress of drug research targeting CBL family, so as to provide a broader clinical measurement strategy for the treatment of tumors.

GPS2 ameliorates cigarette smoking-induced pulmonary vascular remodeling by modulating the ras-Raf-ERK axis

BACKGROUND

Mitogen-activated protein kinase (MAPK)signaling-mediated smoking-associated pulmonary vascular remodeling (PVR) plays an important role in the pathogenesis of group 3 pulmonary hypertension (PH). And G protein pathway suppressor 2 (GPS2) could suppress G-protein signaling such as Ras and MAPK, but its role in cigarette smoking -induced PVR (CS-PVR) is unclear.

METHODS

An in vivo model of smoke-exposed rats was constructed to assess the role of GPS2 in smoking-induced PH and PVR. In vitro, the effects of GPS2 overexpression and silencing on the function of human pulmonary arterial smooth cells (HPASMCs) and the underlying mechanisms were explored.

RESULTS

GPS2 expression was downregulated in rat pulmonary arteries (PAs) and HPASMCs after CS exposure. More importantly, CS-exposed rats with GPS2 overexpression had lower right ventricular systolic pressure (RVSP), right ventricular hypertrophy index (RVHI), and wall thickness (WT%) than those without. And enhanced proliferation and migration of HPASMCs induced by cigarette smoking extract (CSE) can be evidently inhibited by overexpressed GPS2. Besides, GPS2siRNA significantly enhanced the proliferation, and migration of HPASMCs as well as activated Ras and Raf/ERK signaling, while these effects were inhibited by zoledronic acid (ZOL). In addition, GPS2 promoter methylation level in rat PAs and HPASMCs was increased after CS exposure, and 5-aza-2-deoxycytidine (5-aza) inhibited CSE-induced GPS2 hypermethylation and downregulation in vitro.

CONCLUSIONS

GPS2 overexpression could improve the CS-PVR, suggesting that GPS2 might serve as a novel therapeutic target for PH-COPD in the future.

Polyphyllin VII induces autophagy-dependent ferroptosis in human gastric cancer through targeting T-lymphokine-activated killer cell-originated protein kinase

T-lymphokine-activated killer cell-originated protein kinase (TOPK) is a serine-threonine kinase that is overexpressed in gastric cancer (GC) and promotes tumor progression. Polyphyllin VII (PPVII), a pennogenin isolated from the rhizomes of Paris polyphylla, shows anticancer effects. Here, we explored the antitumor activity and mechanism of PPVII in GC. Ferroptosis was detected by transmission electron microscope, malondialdehyde, and iron determination assays. Autophagy and its upstream signaling pathway were detected by Western blot, and gene alterations. The binding of PPVII and TOPK was examined through microscale thermophoresis and drug affinity responsive target stability assays. An in vivo mouse model was performed to evaluate the therapeutic of PPVII. PPVII inhibits GC by inducing autophagy-mediated ferroptosis. PPVII promotes the degradation of ferritin heavy chain 1, which is responsible for autophagy-mediated ferroptosis. PPVII activates the Unc-51-like autophagy-activating kinase 1 (ULK1) upstream of autophagy. PPVII inhibits the activity of TOPK, thereby weakening the inhibition of downstream ULK1. PPVII stabilizes the dimer of the inactive form of TOPK by direct binding. PPVII inhibits tumor growth without causing obvious toxicity in vivo. Collectively, this study suggests that PPVII is a potential agent for the treatment of GC by targeting TOPK to activate autophagy-mediated ferroptosis.

Sculponeatin A promotes the ETS1-SYVN1 interaction to induce SLC7A11/xCT-dependent ferroptosis in breast cancer

BACKGROUND

E26 transformation specificity-1 (ETS1) is a transcription factor that is overexpressed in breast cancer (BC) and promotes tumor progression. Sculponeatin A (stA), a new diterpenoid extracted from Isodon sculponeatus, has no reported antitumor mechanism.

PURPOSE

Here, we explored the antitumor activity of stA in BC and further clarified its mechanism.

METHODS

Ferroptosis was detected by flow cytometric, glutathione, malondialdehyde, and iron determination assays. The effect of stA on the upstream signaling pathway of ferroptosis was detected by Western blot, gene expression, gene alterations and other approaches. The binding of stA and ETS1 was examined through a microscale thermophoresis assay and a drug affinity responsive target stability assay. An in vivo mouse model experiment was performed to evaluate the therapeutic and potential mechanism of stA.

RESULTS

stA exhibits therapeutic potential in BC by inducing SLC7A11/xCT-dependent ferroptosis. stA decreases the expression of ETS1, which is responsible for xCT-dependent ferroptosis in BC. stA inhibits the transcriptional expression of xCT by directly binding to the ETS domain of the ETS1 protein. In addition, stA promotes proteasomal degradation of ETS1 by triggering ubiquitin ligase synoviolin 1 (SYVN1)-mediated ubiquitination. The K318 site of ETS1 mediates ubiquitination of ETS1 by SYVN1. In a mouse model, stA inhibits tumor growth without causing obvious toxicity.

CONCLUSION

Taken together, the results confirm that stA promotes the ETS1-SYVN1 interaction to induce ferroptosis in BC mediated by ETS1 degradation. stA is expected to be used in research of candidate drugs for BC and drug design based on ETS1 degradation.

Genome-wide CRISPR knockout screening identified G protein pathway suppressor 2 as a novel tumor suppressor for uveal melanoma metastasis

PURPOSE

Uveal melanoma (UM) is the most common intraocular malignant tumor in adults. Due to the lack of effective treatments for metastatic UM, the survival of UM has not changed over the past 3 decades. Therefore, it is important to identify essential genes regulating the metastasis of UM.

METHODS

In this study, a genome-wide CRISPR knockout screen in an orthotopic mouse model of UM was performed to identify the regulatory genes conferring the metastatic phenotype. Loss-of-function analyses were performed to explore the function of G protein pathway suppressor 2 (GPS2) in UM metastasis in vitro and in vivo. RNA sequencing was performed to investigate the molecular mechanism underlying the function of GPS2 as a tumor suppressor in UM.

RESULTS

Among the highest-ranking genes, we found several validated tumor suppressors, such as SHPRH, GPS2, PRPH2, and hsa-mir-1229; GPS2 was chosen as the candidate gene for further studies. GPS2 was lower expressed in the tumor tissues of UM patients. Furthermore, knocking-down GPS2 promoted the proliferation and metastatic abilities of UM cells both in vivo and in vitro. Finally, analysis of the transcriptome data revealed that silencing GPS2 upregulates oncogenic signaling pathways MAPK and PI3K-Akt, and in the meantime downregulates tumor suppressor signaling pathway Slit/Robo in UM cells.

CONCLUSION

Altogether, our study proved that the GPS2 gene functions as a tumor suppressor and might be a novel potential therapeutic target for UM treatment.

G Protein Subunit Gamma 5 Is a Prognostic Biomarker and Correlated with Immune Infiltrates in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the malignancies with an extremely inferior prognosis in the abdominal cavity, making it essential to develop more effective biomarkers for HCC. Although GNG5 has been linked to increased patient survival in a variety of human malignancies, no evidence has been found for its involvement in the development of HCC yet. Our study first analyzed the expression and prognosis of GNG5 in HCC using The Cancer Genome Atlas database (TCGA database) with the Gene Expression Omnibus database (GEO database) and found that GNG5 has a potential oncogenic role. Based on survival analysis, the clinical importance and prognostic value of the GNG5 gene were studied. Relying on tumor Immune Estimation Resource database (TIMER database), we analyzed the correlation between the GNG5 gene and HCC Immune infiltration cells. GNG5 expression levels were significantly higher in HCC tissues compared to normal liver tissues. HCC patients with high GNG5 expression had significantly reduced overall survival time and affected multiple immune cell infiltrates. Additionally, KEGG functional enrichment analysis indicated the PI3K-Akt signaling pathway as the most promising carcinogenic pathway associated with GNG5. This is the first comprehensive revelation of GNG5 as a possible new biological marker associated with immune infiltration in HCC. Additionally, it holds promise as an emerging target for HCC immunotherapy.

Inhibitory role of proguanil on the growth of bladder cancer via enhancing EGFR degradation and inhibiting its downstream signaling pathway to induce autophagy

A major reason for the high mortality of patients with bladder cancer (BC) is that chemotherapy and surgery are only effective for very limited patients. Thus, developing novel treatment options becomes an urgent need for improving clinical outcomes and the quality of life for BC patients. Here, we demonstrated that proguanil significantly inhibited the growth of BC in vitro and in vivo. Importantly, our results indicated that the sensitivity of BC cells to proguanil is positively correlated with the expression of epidermal growth factor receptor (EGFR). Mechanistically, proguanil specifically targeted EGFR and promoted EGFR binding to Caveolin-1, enhanced its endocytosis in a Clathrin-independent manner, and then recruited c-Cbl to promote EGFR ubiquitination and degradation through the lysosomal pathway. Further studies suggested that proguanil induced autophagy by destabilizing EGFR and inhibiting its downstream signaling pathway. Thus, this study reveals the novel mechanism of proguanil on anticancer activity and implies the potential benefits of this drug in the treatment of BC.