NET1 promotes HCC growth and metastasis in vitro and in vivo via activating the Akt signaling pathway

The Effects of miR-22-3p on Differentiation of Human Dental Pulp Stem Cells into Neural Progenitor-Like Cells

Stem cell treatment shows promise in treating conditions such as neurodegenerative disorders and spinal injuries, but its effectiveness is hampered by cell death and apoptosis. Improving the differentiation of MSCs into neural cells could enhance their therapeutic potential. The role of miR-22-3p in human dental pulp stem cells (HDPSCs), a superior alternative to treat neurodegenerative disorders, and its molecular mechanisms during neural differentiation remain elusive. Therefore, we investigated the miR-22-3p transfections during HDPSC differentiation into neural progenitor-like cells (NPCs) and elucidated the molecular processes through transcriptomic analysis. HDPSCs were differentiated into NPCs after transfection with a miR-22-3p mimic and inhibitor; the differentiation process was assessed by cell viability and expression of Nestin protein. mRNA sequencing on days 1, 3, and 7 of the differentiation process identified several differentially expressed genes (DEGs). Cytoscape and functional enrichment analysis pinpointed central hub genes among the DEGs and uniquely expressed genes. miR-22-3p mimic hindered HDPSC differentiation by reducing proliferation and increasing apoptosis. It downregulated genes linked to extracellular matrix, synaptic and vesicle functions, lipid metabolism, JAK-STAT, and cell cycle pathways across all days while activating proteasome and digestion pathways. In contrast, miR-22-3p inhibition boosts NPC proliferation and elevates Nestin neural marker protein expression. Altogether, miR-22-3p disrupts synapse functioning and lipid metabolism pathways, resulting in apoptosis and death. Conversely, inhibiting miR-22-3p enhances neural differentiation and proliferation of HDPSCs, suggesting its potential application in generating a greater quantity of NPCs and neurons.

Multiomics analysis reveals the involvement of NET1 in tumour immune regulation and malignant progression

Neuroepithelial cell transforming gene 1 (NET1) is a member of the Ras homologue family member A (RhoA) subfamily of guanine nucleotide exchange factors and a key protein involved in the activation of Rho guanosine triphosphatases, which act as regulators of cell proliferation, cytoskeletal organization, and cell movement and are crucial for cancer spread. Research has shown that NET1 can regulate the malignant biological functions of tumour cells, such as growth, invasion, and metastasis, and it is closely related to the progression of pancreatic cancer, gastric cancer, and liver cancer. However, the comprehensive role and mechanistic function of NET1 in other types of cancer remain largely unexplored. A deeper understanding of the role of NET1 may provide new insights into the molecular mechanisms of cancer progression and metastasis. This study aims to fill this knowledge gap and provide a more comprehensive understanding of the role of NET1 in cancer biology. The Cancer Genome Atlas and Genotype-Tissue Expression databases were utilized to analyse the differential expression of NET1 in normal and cancer tissues. The prognostic value of NET1 in cancer was evaluated through log-rank tests and Cox regression models. Further analysis was conducted to assess the relationships between NET1 expression and clinical features, as well as its diagnostic value. We investigated potential factors contributing to genetic alterations in NET1 to elucidate the role of NET1 in cancer progression. We also explored the relationships between NET1 and genes associated with epigenetic modifications, oncogenes, and tumour characteristics, such as RNA stemness scores (RNAss), DNA stemness scores (DNAss), the tumour mutation burden (TMB), and microsatellite instability (MSI). Additionally, we analysed the associations between NET1 expression and immune cell infiltration, immunoregulatory genes, and sensitivity to therapeutic drugs. We conducted gene set enrichment analysis to further investigate the signalling pathways that might be affected by changes in NET1. The prognostic value of NET1 in triple-negative breast cancer (TNBC) was further validated using real-world and Gene Expression Omnibus (GEO) data. Finally, through both in vivo and in vitro experiments, we confirmed that the overexpression of NET1 contributed to the malignant progression of TNBC cells, and we explored the potential mechanism by which NET1 regulates malignant biological behaviour through cellular experiments. Our study revealed a higher expression level of NET1 in 18 types of tumour tissues than in their corresponding normal tissues. Specifically, we observed high expression of NET1 in LIHC, LUSC, PAAD, and BRCA tumour tissues, which was associated with a poor prognosis. In terms of gene alterations, "amplification", "mutation", and "deep deletion" were identified as the main types of changes occurring in NET1. Among these, "amplification" was predominantly observed in LIHC, LUSC, PAAD, and BRCA. Furthermore, a significant positive correlation was found between copy number variations and the NET1 expression level in various tumours, including LIHC, LUSC, PAAD, and BRCA. We also discovered that NET1 expression was positively correlated with the expression of genes related to epigenetic modification in almost all types of cancer and was related to the expression levels of numerous oncogenes. In certain tumours, a significant positive correlation was noted between the expression of NET1 and TMB, MSI, DNAss, and RNAss. Intriguingly, in most tumours, NET1 expression was strongly negatively correlated with the levels of infiltrating natural killer cells and M1 macrophages. Moreover, NET1 expression was significantly positively correlated with the expression of immune genes in nearly all types of cancer. An analysis of single-cell data revealed that NET1 was expressed primarily in malignant tumour cells in most tumours, with little to no expression in immune cells. Additionally, the expression level of NET1 was associated with sensitivity to various therapeutic drugs. Data from GEO and real-world studies indicated high expression of NET1 in TNBC tissues, which was correlated with a poor prognosis. Cellular experiments indicated that NET1 could regulate the proliferation, invasion, cell cycle, and apoptosis of TNBC cells. Furthermore, NET1 may mediate the malignant proliferation of tumour cells through the AKT signalling pathway. NET1 can serve as a potential prognostic marker for LIHC, LUSC, PAAD, and BRCA tumours. Real-world data further suggest that NET1 can also serve as a prognostic indicator for TNBC. High expression of NET1 may contribute to the malignant proliferation of TNBC cells, potentially through the AKT signalling pathway. Moreover, NET1 may contribute to the formation of an immunosuppressive microenvironment that can promote tumour progression. Therefore, targeting NET1 may represents a promising approach for inhibiting tumour progression.

Reduced NET1 adversely affects early embryonic development in mice

Neuroepithelial transforming gene 1 (NET1) is a RhoA subfamily-specific guanine/nucleotide-exchange factor that exhibits critical roles in diverse biological processes. However, the functions in mouse preimplantation embryonic development have not yet determined. In the present study we demonstrated that NET1 is a key factor in the outcome of early mouse embryonic development. Immunofluorescence detection showed that NET1 is principally localized to the nucleus during mouse pre-implantation embryonic development. Silencing Net1 at the zygote stage using a specific siRNA impaired the developmental competence of early mouse embryos, and Net1-knockdown (Net1-KD) induced mitotic spindle-assembly defects and chromosomal alignment abnormalities at the first embryonic cleavage. In addition, reduced NET1 exacerbated reactive oxygen species production and DNA lesions in two-cell stage embryos, further augmenting cellular apoptosis in the preimplantation blastocyst. In summary, our data display key roles for NET1 in mitotic spindle assembly, oxidative stress, and DNA damage during early mouse embryonic development.

Conditional Overexpression of Net1 Enhances the Trans-Differentiation of Lgr5+ Progenitors into Hair Cells in the Neonatal Mouse Cochlea

Sensorineural hearing loss is mainly caused by damage to hair cells (HC), which cannot be regenerated spontaneously in adult mammals once damaged. Cochlear Lgr5+ progenitors are characterised by HC regeneration capacity in neonatal mice, and we previously screened several new genes that might induce HC regeneration from Lgr5+ progenitors. Net1, a guanine nucleotide exchange factor, is one of the screened new genes and is particularly active in cancer cells and is involved in cell proliferation and differentiation. Here, to explore in vivo roles of Net1 in HC regeneration, Net1loxp/loxp mice were constructed and crossed with Lgr5CreER/+ mice to conditionally overexpress (cOE) Net1 in cochlear Lgr5+ progenitors. We observed a large number of ectopic HCs in Lgr5CreER/+Net1loxp/loxp mouse cochlea, which showed a dose-dependent effect. Moreover, the EdU assay was unable to detect any EdU+/Sox2+ supporting cells, while lineage tracing showed significantly more regenerated tdTomato+ HCs in Lgr5CreER/+Net1loxp/loxptdTomato mice, which indicated that Net1 cOE enhanced HC regeneration by inducing the direct trans-differentiation of Lgr5+ progenitors rather than mitotic HC regeneration. Additionally, qPCR results showed that the transcription factors related to HC regeneration, including Atoh1, Gfi1 and Pou4f3, were significantly upregulated and are probably the mechanism behind the HC regeneration induced by Net1. In conclusion, our study provides new evidence for the role of Net1 in enhancing HC regeneration in the neonatal mouse cochlea.

Tdh3 and Rom2 are functional modulators of a conserved condensate-resident RNA-binding protein, Scd6, in Saccharomyces cerevisiae

Arginine-glycine-glycine motif proteins play a crucial role in determining mRNA fate. Suppressor of clathrin deficiency 6 (Scd6) is a conserved arginine-glycine-glycine motif containing ribonucleoprotein (RNP) condensate-resident, translation repressor, and decapping activator protein in Saccharomyces cerevisiae. Identifying protein factors that can modulate Scd6 function is critical to understanding the regulation of mRNA fate by Scd6. In this study, using an approach that combined mRNA tethering assay with flow cytometry, we screened 50 genes for their role in modulating the translation repression activity of Scd6. We identified 8 conserved modulators with human homologs. Of these, we further characterized in detail guanine nucleotide exchange factor Rho1 multicopy suppressor 2 (Rom2) and glycolytic enzyme triose phosphate dehydrogenase 3 (Tdh3), which, respectively, impede and promote translation repression activity of Scd6. Our study reveals that Rom2 negatively regulates the arginine methylation of Scd6 and antagonizes its localization to P-bodies. Tdh3, on the other hand, promotes Scd6 interaction with Hmt1, thereby promoting the arginine methylation of Scd6 and enhanced eIF4G1 interaction, which is known to promote its repression activity. Identifying these novel modulators provides exciting new insights into the role of a metabolic enzyme of the glycolytic pathway and guanine nucleotide exchange factor implicated in the cell wall integrity pathway in regulating Scd6 function and, thereby, cytoplasmic mRNA fate.

NET1 is a critical regulator of spindle assembly and actin dynamics in mouse oocytes

BACKGROUND

Neuroepithelial transforming gene 1 (NET1) is a RhoA subfamily guanine nucleotide exchange factor that governs a wide array of biological processes. However, its roles in meiotic oocyte remain unclear. We herein demonstrated that the NET1-HACE1-RAC1 pathway mediates meiotic defects in the progression of oocyte maturation.

METHODS

NET1 was reduced using a specific small interfering RNA in mouse oocytes. Spindle assembly, chromosomal alignment, the actin cap, and chromosomal spreads were visualized by immunostaining and analyzed under confocal microscopy. We also applied mass spectroscopy, and western blot analysis for this investigation.

RESULTS

Our results revealed that NET1 was localized to the nucleus at the GV stage, and that after GVBD, NET1 was localized to the cytoplasm and predominantly distributed around the chromosomes, commensurate with meiotic progression. NET1 resided in the cytoplasm and significantly accumulated on the spindle at the MI and MII stages. Mouse oocytes depleted of Net1 exhibited aberrant first polar body extrusion and asymmetric division defects. We also determined that Net1 depletion resulted in reduced RAC1 protein expression in mouse oocytes, and that NET1 protected RAC1 from degradation by HACE1, and it was essential for actin dynamics and meiotic spindle formation. Importantly, exogenous RAC1 expression in Net1-depleted oocytes significantly rescued these defects.

CONCLUSIONS

Our results suggest that NET1 exhibits multiple roles in spindle stability and actin dynamics during mouse oocyte meiosis.

Cell-in-Cell-Mediated Entosis Reveals a Progressive Mechanism in Pancreatic Cancer

BACKGROUND & AIMS

Pancreatic ductal adenocarcinoma (PDAC) is a deadly malignancy with high intratumoral heterogeneity. There is a lack of effective therapeutics for PDAC. Entosis, a form of nonapoptotic regulated cell death mediated by cell-in-cell structures (CICs), has been reported in multiple cancers. However, the role of entosis in PDAC progression remains unclear.

METHODS

CICs were evaluated using immunohistochemistry and immunofluorescence staining. The formation of CICs was induced by suspension culture. Through fluorescence-activated cell sorting and single-cell RNA sequencing, entosis-forming cells were collected and their differential gene expression was analyzed. Cell functional assays and mouse models were used to investigate malignant phenotypes. Clinical correlations between entosis and PDAC were established by retrospective analysis.

RESULTS

Entosis was associated with an unfavorable prognosis for patients with PDAC and was more prevalent in liver metastases than in primary tumors. The single-cell RNA sequencing results revealed that several oncogenes were up-regulated in entosis-forming cells compared with parental cells. These highly entotic cells demonstrated higher oncogenic characteristics in vitro and in vivo. NET1, neuroepithelial cell transforming gene 1, is an entosis-related gene that plays a pivotal role in PDAC progression and is correlated with poor outcomes.

CONCLUSIONS

Entosis is correlated with PDAC progression, especially in liver metastasis. NET1 is a newly validated entosis-related gene and a molecular marker of poor outcomes. PDAC cells generate a highly aggressive subpopulation marked by up-regulated NET1 via entosis, which may drive PDAC progression.

Cancer invasion and metastasis: Insights from murine pubertal mammary gland morphogenesis

Cancer invasion and metastasis accounts for the majority of cancer related mortality. A better understanding of the players that drive the aberrant invasion and migration of tumors cells will provide critical targets to inhibit metastasis. Postnatal pubertal mammary gland morphogenesis is characterized by highly proliferative, invasive, and migratory normal epithelial cells. Identifying the molecular regulators of pubertal gland development is a promising strategy since tumorigenesis and metastasis is postulated to be a consequence of aberrant reactivation of developmental stages. In this review, we summarize the pubertal morphogenesis regulators that are involved in cancer metastasis and revisit pubertal mammary gland transcriptome profiling to uncover both known and unknown metastasis genes. Our updated list of pubertal morphogenesis regulators shows that most are implicated in invasion and metastasis. This review highlights molecular linkages between development and metastasis and provides a guide for exploring novel metastatic drivers.

Src stimulates Abl-dependent phosphorylation of the guanine exchange factor Net1A to promote its cytosolic localization and cell motility

The neuroepithelial cell transforming gene 1 (Net1) is a guanine nucleotide exchange factor for the small GTPase RhoA that promotes cancer cell motility and metastasis. Two isoforms of Net1 exist, Net1 and Net1A, both of which are sequestered in the nucleus in quiescent cells to prevent aberrant RhoA activation. Many cell motility stimuli drive cytosolic relocalization of Net1A, but mechanisms controlling this event are not fully understood. Here, we demonstrate that epithelial growth factor stimulates protein kinase Src- and Abl1-dependent phosphorylation of Net1A to promote its cytosolic localization. We show that Abl1 efficiently phosphorylates Net1A on Y373, and that phenylalanine substitution of Y373 prevents Net1A cytosolic localization. Furthermore, we found that Abl1-driven cytosolic localization of Net1A does not require S52, which is a phosphorylation site of a different kinase, c-Jun N-terminal kinase, that inhibits nuclear import of Net1A. However, we did find that MKK7-stimulated cytosolic localization of Net1A does require Y373. We also demonstrate that aspartate substitution at Y373 is sufficient to promote Net1A cytosolic accumulation, and expression of Net1A Y373D potentiates epithelial growth factor-stimulated RhoA activation, downstream myosin light chain 2 phosphorylation, and F-actin accumulation. Moreover, we show that expression of Net1A Y373D in breast cancer cells also significantly increases cell motility and Matrigel invasion. Finally, we show that Net1A is required for Abl1-stimulated cell motility, which is rescued by expression of Net1A Y373D, but not Net1A Y373F. Taken together, this work demonstrates a novel mechanism controlling Net1A subcellular localization to regulate RhoA-dependent cell motility and invasion.

A cellular senescence-related classifier based on a tumorigenesis- and immune infiltration-guided strategy can predict prognosis, immunotherapy response, and candidate drugs in hepatocellular carcinoma

BACKGROUND

Cellular senescence plays an irreplaceable role in tumorigenesis, progression, and tumor microenvironment (TME) remodeling. However, to date, there is limited research delineating the landscape of cellular senescence in hepatocellular carcinoma (HCC), and an improved understanding on the interaction of tumor-associated cellular senescence with HCC prognosis, TME, and response to immunotherapy is warrant.

METHODS

Tumorigenic and immune infiltration-associated senescence genes were determined by weighted gene co-expression network analysis (WGCNA) and the Estimation of STromal and Immune cells in MAlignant Tumor tissues using Expression data (ESTIMATE) algorithm, and subsequently, a prognostic scoring model (named TIS) was constructed using multiple survival analysis algorithms to classify the senescence-related subtypes of HCC. Gene set enrichment analysis (GSEA) and gene set variation analysis (GSVA) were conducted to identify the distinct hallmark pathways between high- and low-risk subtypes. Additionally, we carried out correlation analyses for TIS and clinical traits, senescence-associated secretory phenotype (SASP), immune infiltration and evasion, immune checkpoint factors, drug response, and immunotherapeutic efficacy. External experimental validation was conducted to delineate the association of CPEP3 (a TIS gene) with HCC phenotypes through assays of proliferation, colony formation, and invasion.

RESULTS

A five-gene TIS, composed of NET1, ATP6V0B, MMP1, GTDC1, and CPEB3, was constructed and validated using TCGA and ICGC datasets, respectively, and showed a highly robust and plausible signature for overall survival (OS) prediction of HCC in both training and validation cohorts. Patients in the TIS-high group were accompanied by worse OS, activation of carcinogenetic pathways, infiltration of immunosuppressive cells, exclusion of effector killing cells, overexpression of immunomodulatory genes and SASP, and unsatisfied response to immunotherapy. In response to anticancer drugs, patients in the TIS-high group exhibited enhanced susceptibility to several conventional chemotherapeutic agents (5-fluorouracil, docetaxel, doxorubicin, gemcitabine, and etoposide), as well as several inhibitors of pathways involved in cellular senescence (cell-cycle inhibitors, bromodomain and extraterminal domain family (BET) inhibitors, PI3K-AKT pathway inhibitors, and multikinase inhibitors). Additionally, four putative drugs (palbociclib, JAK3 inhibitor VI, floxuridine, and lestaurtinib) were identified as potential compounds for patients in the TIS-high group. Notably, in vitro functional validation showed that CPEB3 knockdown boosted the phenotypes of proliferation, clonogenicity, and invasion in HCC cells, whereas CPEB3 overexpression attenuated these phenotypes.

CONCLUSIONS

Our study provides comprehensive clues demonstrating the role of novel TIS in predicting HCC prognosis, immunotherapeutic response, and candidate drugs. This work highlights the significance of tumorigenesis- and immune infiltration-related cellular senescence in cancer therapy.