Evaluation of acute and subacute toxicity of sodium taurodeoxycholate in rats.

Taurodeoxycholate (TDCA) inhibits various inflammatory responses suggesting potential clinical application. However, the toxicity of TDCA has not been evaluated in detail in vivo. We investigated the acute toxicity and 4-week repeated-dose toxicity of TDCA following intravenous infusion under Good Laboratory Practice regulations. In the sighting study of acute toxicity, one of two rats (one male and one female) treated with 300 mg/kg TDCA died with hepatotoxicity, suggesting that the approximate 50% lethal dose of TDCA is 300 mg/kg. Edema and discoloration were observed at the injection sites of tails when rats were infused with 150 mg/kg or higher amount of TDCA once. In 4-week repeated-dose toxicity study, no treatment-related mortality or systemic changes in hematology and serum biochemistry, organ weights, gross pathology, or histopathology were observed. However, the tail injection site showed redness, discharge, hardening, and crust formation along with histopathological changes such as ulceration, edema, fibrosis, and thrombosis when rats were infused with 20 mg/kg TDCA. Taken together, TDCA induced no systemic toxicity or macroscopic lesions at the injection site at a dose of 10 mg/kg/day, which is 33 times higher than the median effective dose observed in a mouse sepsis model. These findings suggest that TDCA might have a favorable therapeutic index in clinical applications.

Nonclinical toxicology studies with sodium taurodeoxycholate: acute and subacute toxicity in dogs.

Sodium taurodeoxycholate (TDCA) has been investigated for various inflammatory disorders such as sepsis. We recently evaluated nonclinical safety profile of TDCA using rats infused intravenously. As a series of preclinical safety investigations, we further conducted toxicity studies with TDCA delivered to dogs via intravenous administration under Good Laboratory Practice regulation in this study. In dose range-finding study (dose escalation study), dogs given with TDCA at a dose of 150 mg/kg showed marked changes in clinical signs, hematology, and serum biochemistry. And biochemical markers of liver damage and local skin lesions were observed following intravenous infusion of 100 mg/kg TDCA, suggesting that 100 mg/kg was chosen as the highest dose of TDCA for 4-week repeated-dose toxicity study using dogs. Despite no treatment-related significant changes in body weight, food consumption, ophthalmoscopy, and urinalysis, skin lesions were observed at the injection site of animals administered with higher than 50 mg/kg of TDCA along with biochemical and histopathological changes associated with liver injury. However, most of off-target effects were found to be reversible since these were recovered after stopping TDCA infusion. These findings indicate that the no-observed-adverse-effect-level (NOAEL) for TDCA in dogs was considered to be 5 mg/kg/d. Taken together, our results provide important toxicological profiles regarding the safe dose of TDCA for drug development or clinical application.

Prognostic factors for the survival of primary molars following pulpotomy with mineral trioxide aggregate: a retrospective cohort study.

OBJECTIVES: The aim of the present study was to evaluate potential factors influencing the success rates of mineral trioxide aggregate (MTA) pulpotomy performed in primary molars. MATERIALS AND METHODS: A total of 347 teeth treated between March 2012 and December 2016 in 258 patients, with a mean age of 5.3 ± 1.7 years, were included in the analysis. Kaplan-Meier analyses were used to analyze were used time to failure. Multivariate Cox regression analysis with shared frailty was used to evaluate the clinical factors associated with failures. RESULTS: The mean (standard deviation) follow-up period was 35.8 (19.6) months. Within 84 months, the survival rate was 87.1%. In multivariate Cox regression, treatment performed in lower primary molars had a lower survival rate than upper primary molars (hazard ratio [HR] = 3.38, P = 0.012). Caries extension below the cemento-enamel junction had more risk of failure (HR = 10.9, P < 0.001). Final restoration using resin-modified glass ionomer or amalgam (direct filling) had a lower survival rate than stainless steel crown (HR = 5.62, P = 0.002). CONCLUSIONS: Clinical variables such as arch type, degree of caries extension, and type of final restoration may affect the survival of primary molars following MTA pulpotomy. CLINICAL RELEVANCE: The results of this study indicate that specific clinical variables can be used to predict the prognosis of MTA pulpotomy in primary teeth, and estimate the risk of treatment failure. Assessments of these variables should be performed in the context of evidence-based clinical decision making.

Deferoxamine Reduces Inflammation and Osteoclastogenesis in Avulsed Teeth.

Replacement and inflammatory resorption are serious complications associated with the delayed replantation of avulsed teeth. In this study, we aimed to assess whether deferoxamine (DFO) can suppress inflammation and osteoclastogenesis in vitro and attenuate inflammation and bone resorption in a replanted rat tooth model. Cell viability and inflammation were evaluated in RAW264.7 cells. Osteoclastogenesis was confirmed by tartrate-resistant acid phosphatase staining, reactive oxygen species (ROS) measurement, and quantitative reverse transcriptase-polymerase chain reaction in teeth exposed to different concentrations of DFO. In vivo, molars of 31 six-week-old male Sprague-Dawley rats were extracted and stored in saline (n = 10) or DFO solution (n = 21) before replantation. Micro-computed tomography (micro-CT) imaging and histological analysis were performed to evaluate inflammation and root and alveolar bone resorption. DFO downregulated the genes related to inflammation and osteoclastogenesis. DFO also reduced ROS production and regulated specific pathways. Furthermore, the results of the micro-CT and histological analyses provided evidence of the decrease in inflammation and hard tissue resorption in the DFO group. Overall, these results suggest that DFO reduces inflammation and osteoclastogenesis in a tooth replantation model, and thus, it has to be further investigated as a root surface treatment option for an avulsed tooth.

Intranuclear Delivery of Nuclear Factor-Kappa B p65 in a Rat Model of Tooth Replantation.

After avulsion and replantation, teeth are at risk of bone and root resorption. The present study aimed to demonstrate that the intra-nuclear transducible form of transcription modulation domain of p65 (nt-p65-TMD) can suppress osteoclast differentiation in vitro, and reduce bone resorption in a rat model of tooth replantation. Cell viability and nitric oxide release were evaluated in RAW264.7 cells using CCK-8 assay and Griess reaction kit. Osteoclast differentiation was evaluated using quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and tartrate-resistant acid phosphatase (TRAP) staining. Thirty-two maxillary rat molars were extracted and stored in saline (n = 10) or 10 µM nt-p65-TMD solution (n = 22) before replantation. After 4 weeks, specimens were scored according to the inflammatory pattern using micro-computed tomography (CT) imaging and histological analyses. nt-p65-TMD treatment resulted in significant reduction of nitric oxide release and osteoclast differentiation as studied using PCR and TRAP staining. Further, micro-CT analysis revealed a significant decrease in bone resorption in the nt-p65-TMD treatment group (p < 0.05). Histological analysis of nt-p65-TMD treatment group showed that not only bone and root resorption, but also inflammation of the periodontal ligament and epithelial insertion was significantly reduced. These findings suggest that nt-p65-TMD has the unique capabilities of regulating bone remodeling after tooth replantation.

Heimann-Bielschowsky phenomenon and hypotropic DVD in case of monocular vision loss: a case report.

BACKGROUND: The Heimann-Bielschowsky phenomenon (HBP) is an underrecognized condition characterized by slow, pendular, vertical oscillations of the eye accompanying monocular vision loss. Hypotropic dissociated vertical deviation (DVD) is another rare condition induced by asymmetric visual input. This report documents a rare case of HBP with hypotropic DVD. CASE PRESENTATION: This report describes a case of a 58-year-old woman with HBP and hypotropic DVD, having suffered monocular vision loss in the left eye due to blunt trauma at the age of 10. Preoperatively, she was orthophoric at near fixation and demonstrated an intermittent, slow hypotropia of the left eye upon distance fixation that never rose above the midline. She underwent a 7 mm recession of the inferior rectus muscle in the left eye. After surgery, intermittent, downward drifts became constant vertical oscillations at both distance and near fixation. CONCLUSIONS: This case describes the clinical manifestation of an eye movement disorder related to prolonged monocular vision loss.

Effect of Heat and Sonic Vibration on Penetration of a Flowable Resin Composite Used as a Pit and Fissure Sealant.

OBJECTIVE: To evaluate penetration of a flowable resin composite into fissures using three different application methods: (1) conventional, (2) heat, and (3) sonic vibration. STUDY DESIGN: Forty-five sound maxillary third molars were divided randomly into three groups (n=15 per group). The occlusal surfaces of the teeth were etched and flowable resin composites were applied into the fissure using the assigned application method. The crowns were sectioned and examined with an optical microscope to assess penetration. In addition, three-point flexural strength was analyzed. RESULTS: The sonic vibration group exhibited significantly greater penetration into the fissure compared with the other test groups (p<0.001). The heat group exhibited greater penetration into the fissure compared with the conventional group (p=0.003). However, three-point flexural strength was similar among all groups (p>0.05). CONCLUSIONS: Sonic vibration and heat increased penetration into fissures. Notably, sonic vibration exhibited the greatest penetration. We found that the application method did not influence the three-point flexural strength.

Changing the Angulation of the Tooth Germ in the Bony Crypt: A Case Report.

An ankylosed primary molar may cause rotation or ectopic impaction of succedaneous premolar. When conventional treatment modalities such as observation, surgical exposure with or without orthodontic traction, and autotransplantation are not possible, the simple surgical relocation method could be an alternative treatment option for a lingually rotated premolar during the tooth germ stage before opting to extraction. In the case reported herein, the lingually rotated permanent mandibular second premolar tooth germ was surgically relocated within its bony crypt. Continued root development and spontaneous eruption were observed without complications during the 3.5-year follow-up period.

Genetic analysis of non-syndromic familial multiple supernumerary premolars.

OBJECTIVE: Supernumerary teeth, a term describing a condition where patients have an abnormally large number of teeth, can be associated with non-syndromic or syndromic phenotypes. PDGFRs are cell surface tyrosine kinase receptors, and are involved in several aspects of tooth development. The purpose of this study was to identify causative genes of familial supernumerary teeth and the molecular pathogenesis of tooth number abnormalities through genetic analysis of a family that showed supernumerary premolars in two successive generations. MATERIAL AND METHODS: We recruited a Korean family with supernumerary premolars and performed mutational analyses to identify the underlying molecular genetic aetiology. RESULTS: Targeted exome sequencing identified a missense mutation in PDGFRB (c.C2053T, p.R685C). Sanger sequencing confirmed that three affected individuals in the patient's family were heterozygous for the mutation. CONCLUSIONS: This is the first report of a Korean family that carries a PDGFRB mutation potentially responsible for supernumerary premolars. Our results demonstrate the power of next-generation sequencing in rapidly determining the genetic aetiology of numerical tooth abnormalities.

Clinical Assessment of a New Caries Activity Test Using Dental Plaque Acidogenicity in Children under Three Years of Age.

OBJECTIVES: The aim of this study was to assess the validity of a new caries activity test that uses dental plaque acidogenicity in children with deciduous dentition. STUDY DESIGN: Ninety-two children under the age of three years old underwent clinical examination using the dft index and examinations with two caries activity tests. Plaque samples for the new Cariview(®) test and the saliva sample for the conventional Dentocult SM(®) test were collected, incubated, and scored according to each manufacturers' instruction. The data were analysed using ANOVA and Spearman correlation analyses to evaluate the relationships between the test results and the caries experience. RESULTS: The mean dft index of all of the subjects was 4.73, and 17.4% of the subjects were caries-free. The levels of caries risk based on the new Cariview test score significantly increased with the caries experience (p < 0.01). The test results revealed a stronger correlation with caries indices (dft and dt index) than the conventional SM colony counting method (r = 0.43, r = 0.39, p < 0.01). CONCLUSIONS: The new caries activity test to analyse the acidogenic potential of whole microorganisms from dental plaques can be used to evaluate caries risk in children with deciduous teeth.

Mutagenicity and tumor-promoting effects of Tiglium seed extract via PKC and MAPK signaling pathways.

Tiglium seed is a seed of mature Croton Tiglium Linne containing croton oils, which have been traditionally used as laxative or purgative. As it contains phorbol derivatives, we investigated the mutagenicity and tumor-promoting activity of Tiglium seed. Tiglium seed extract produced the mutagenic responses in five Salmonella typhimurium strains in Ames assay, whereas it did not alter the frequencies of chromosomal aberrations or micronuclei, indicating that it exerted the mutagenic potential, not clastogenicity. Accompanied with phosphorylation of connexin43 (Cx43) and extracellular signal-regulated kinases 1/2 (ERK1/2), Tiglium seed extract inhibited gap junctional intercellular communication (GJIC) associated with tumor-promoting potential. Importantly, these effects were blocked by a protein kinase C (PKC) inhibitor or mitogen-activated protein kinase (MAPKs) inhibitors, suggesting that Tiglium seed-induced GJIC inhibition was regulated by phosphorylation of Cx43 via PKC and MAPKs signaling. In conclusion, Tiglium seed has mutagenicity, possibly linking to tumor-promoting potential through the dysfunction of GJIC.

TRPM7 Is Essential for RANKL-Induced Osteoclastogenesis.

The transient receptor potential melastatin type 7 (TRPM7) channel is a widely expressed non-selective cation channel with fusion to the C-terminal alpha kinase domain and regarded as a key regulator of whole body Mg(2+) homeostasis in mammals. However, the roles of TRPM7 during osteoclastogenesis in RAW264.7 cells and bone marrow-derived monocyte/macrophage precursor cells (BMMs) are not clear. In the present study, we investigate the roles of TRPM7 in osteoclastogenesis using methods of small interfering RNA (siRNA), RT-PCR, patch-clamp, and calcium imaging. RANKL (receptor activator of NF-κB ligand) stimulation did not affect the TRPM7 expression and TRPM7-mediated current was activated in HEK293, RAW264.7, and BMM cells by the regulation of Mg(2+). Knock-down of TRPM7 by siTRPM7 reduced intracellular Ca(2+) concentration ([Ca(2+)](i)) increases by 0 mM [Mg(2+)](e) in HEK293 cells and inhibited the generation of RANKL-induced Ca(2+) oscillations in RAW264.7 cells. Finally, knock-down of TRPM7 suppressed RANKL-mediated osteoclastogenesis such as activation and translocation of NFATc1, formation of multinucleated cells, and the bone resorptive activity, sequentially. These results suggest that TRPM7 plays an essential role in the RANKL-induced [Ca(2+)](i) oscillations that triggers the late stages of osteoclastogenesis.

CTTN Overexpression Confers Cancer Stem Cell-like Properties and Trastuzumab Resistance via DKK-1/WNT Signaling in HER2 Positive Breast Cancer.

BACKGROUND: Despite the therapeutic success of trastuzumab, HER2 positive (HER2+) breast cancer patients continue to face significant difficulties due to innate or acquired drug resistance. In this study we explored the potential role of CTTN in inducing trastuzumab resistance of HER2+ breast cancers. METHODS: Genetic changes of CTTN and survival of HER2+ breast cancer patients were analyzed in multiple breast cancer patient cohorts (METABRIC, TCGA, Kaplan-Meier (KM) plotter, and Hanyang University cohort). The effect of CTTN on cancer stem cell activity was assessed using the tumorsphere formation, ALDEFLUOR assay, and by in vivo xenograft experiments. CTTN-induced trastuzumab resistance was assessed by the sulforhodamine B (SRB) assay, colony formation assays, and in vivo xenograft model. RNA-seq analysis was used to clarify the mechanism of trastuzumab resistance conferred by CTTN. RESULTS: Survival analysis indicated that CTTN overexpression is related to a poor prognosis in HER2+ breast cancers (OS, p = 0.05 in the Hanyang University cohort; OS, p = 0.0014 in KM plotter; OS, p = 0.008 and DFS, p = 0.010 in METABRIC). CTTN overexpression-induced cancer stem cell-like characteristics in experiments of tumorsphere formation, ALDEFLUOR assays, and in vivo limiting dilution assays. CTTN overexpression resulted in trastuzumab resistance in SRB, colony formation assays, and in vivo xenograft models. Mechanistically, the mRNA and protein levels of DKK-1, a Wnt antagonist, were downregulated by CTTN. Treatment of the ß-catenin/TCF inhibitor reversed CTTN-induced cancer stem cell-like properties in vitro. Combination treatment with trastuzumab and ß-catenin/TCF inhibitor overcame trastuzumab resistance conferred by CTTN overexpression in in vitro colony formation assays. CONCLUSIONS: CTTN activates DKK-1/Wnt/ß-catenin signaling to induce trastuzumab resistance. We propose that CTTN is a novel biomarker indicating a poor prognosis and a possible therapeutic target for overcoming trastuzumab resistance.

Biocompatibility and mineralization potential of new calcium silicate cements.

Background/purpose: As calcium silicate cements (CSCs) have been successfully used in various types of vital pulp therapy, many new CSC products have been developed. The aim of this study was to evaluate the biocompatibilities and mineralization potential of new CSC. The experimental materials were NeoMTA Plus and EndoSequence Root Repair Material-Fast Set Putty (ERRM-FS) which were compared to ProRoot MTA. Materials and methods: In vitro, the effects of the new CSC on stem cells were evaluated. Each CSC was prepared for cell viability testing, alkaline phosphatase (ALP) assay, and calcium ion release assay. In vivo, the exposed pulp model was used for the partial pulpotomy procedure. Thirty-six teeth were treated with three materials: ProRoot MTA, NeoMTA Plus, or ERRM-FS. After four weeks, the teeth were extracted and processed for histologic analysis. Dentin bridge formation, pulp inflammation, and odontoblastic cell layer were evaluated and the area of newly formed calcific barrier of each group was measured. Results: Three CSCs demonstrated similar cell viability on stem cells and the levels of ALP and calcium release were not significantly different between tested materials. ProRoot MTA and ERRM-FS showed better tissue healing process than NeoMTA Plus after partial pulpotomy, in terms of quality of calcific barrier and pulp inflammation. The outcomes from measuring newly formed calcific area demonstrated no significant differences between the materials. Conclusion: NeoMTA Plus and ERRM-FS displayed similar biocompatibilities and mineralization potential compared to ProRoot MTA. Therefore, these new CSCs can be used as desirable alternatives to ProRoot MTA.

General gene expression patterns and stemness of the gingiva and dental pulp.

BACKGROUND/PURPOSE: Due to the unique properties of healing processes and cellular differentiation, the gingiva and dental pulp have attracted attention as a potential source of mesenchymal stem cells (MSCs). The purpose of this study was to obtain molecular-level information on these tissues in terms of their function and differentiation processes and investigate stemness. MATERIALS AND METHODS: Healthy gingival tissues were collected from patients (n = 9; aged 7-12 years) who underwent simple surgical procedures, and normal dental pulp tissues were obtained from patients (n = 25; aged 11-25 years) undergoing tooth extraction for orthodontic reasons. Complementary DNA microarray, qRT-qPCR, and immunohistochemical staining were performed to assess general and MSC gene expression patterns. RESULTS: In the gingival tissue, genes related to keratinization, the formation of epithelial cells and ectoderm, and immune and/or inflammatory responses were highly expressed. Meanwhile, in the dental pulp tissue, genes related to ion transport, neuronal development and axon guidance, bone and enamel mineralization, extracellular matrix organization, and angiogenesis were highly expressed. When focusing on the expression of MSC genes, induced pluripotent stem (iPS) cell genes, such as Sox2, c-Myc, and KLF4, were expressed at higher levels in the gingival tissue, whereas dental stem cell genes, such as NT5E and VCAM1, were expressed in dental pulp tissue. CONCLUSION: We found different general and MSC gene expression patterns between the gingival and dental pulp tissue. These results have implications for future regenerative medicine, considering the application of gingival tissue as a potential source of iPS cells.

Establishment of efficacy and safety assessment of human adipose tissue-derived mesenchymal stem cells (hATMSCs) in a nude rat femoral segmental defect model.

Human adipose tissue-derived mesenchymal stem cell (hATMSC) have emerged as a potentially powerful tool for bone repair, but an appropriate evaluation system has not been established. The purpose of this study was to establish a preclinical assessment system to evaluate the efficacy and safety of cell therapies in a nude rat bone defect model. Segmental defects (5 mm) were created in the femoral diaphyses and transplanted with cell media (control), hydroxyapatite/tricalcium phosphate scaffolds (HA/TCP, Group I), hATMSCs (Group II), or three cell-loading density of hATMSC-loaded HA/TCP (Group III-V). Healing response was evaluated by serial radiography, micro-computed tomography and histology at 16 weeks. To address safety-concerns, we conducted a GLP-compliant toxicity study. Scanning electron microscopy studies showed that hATMSCs filled the pores/surfaces of scaffolds in a cell-loading density-dependent manner. We detected significant increases in bone formation in the hATMSC-loaded HA/TCP groups compared with other groups. The amount of new bone formation increased with increases in loaded cell number. In a toxicity study, no significant hATMSC-related changes were found in body weights, clinical signs, hematological/biochemical values, organ weights, or histopathological findings. In conclusion, hATMSCs loaded on HA/TCP enhance the repair of bone defects and was found to be safe under our preclinical efficacy/safety hybrid assessment system.

Modifications of Rect-Spring to Enhance the Engagement of Ectopically Entrapped Molars with 2 Case Reports.

The Rect-spring appliance, used for the management of ectopically erupting molars, shows weak retention on mesially tilted molars. We present three modifications of the appliance for better engagement and their advantages. We describe cases of two 7-year-old patients with ectopically erupting maxillary first molars with a 2.2 mm and 2.5 mm depth of entrapment, respectively. The modified Rect-spring (mRS) was inserted between the ectopically erupting first molar and adjacent primary second molar, and exerted a distalization force with an interproximal wedging effect at the same time. After 3 months, the ectopically erupting first molars were successfully brought into proper occlusion. No discomfort was reported. The mRS is suitable for various locking cases except for severely tilted molars without requiring any laboratory procedures. We suggest it as the first choice for unlocking the first molars.

The Piston Elastic: A Novel Device for Treating Entrapped Ectopic Permanent Molars.

Ectopic eruption of the permanent molar may absorb the distal root of the primary second molar and may result in a decreased arch length or delayed eruption of the permanent tooth, requiring timely treatment. Therefore, we devised an effective and convenient method to unlock the entrapped tooth using a novel device called a "piston-elastic". This case report aims to explain the design and clinical application of this piston-elastic and to describe successful cases. Three patients (aged 6, 13, and 16 years) with ectopically erupted maxillary and mandibular molars, respectively, were treated with a piston-elastic. It was bound to the locked molar to improve the eruption path. After a certain time period, the repulsive force pushed the surface of the adjacent tooth, improving the eruption path of the entrapped tooth. The piston-elastic is a novel device that simply and effectively changes the direction of eruption of ectopically entrapped molars. As it can be manufactured and attached to the chair side, impression acquisition on a model cast and laboratory procedures are unnecessary. Compared to existing methods, the piston-elastic can be easily produced and delivered, causes little irritation, and is inexpensive.

In Vivo Evaluation of Decellularized Human Tooth Scaffold for Dental Tissue Regeneration.

Conventional root canal treatment may result in loss of tooth vitality, which can lead to unfavorable treatment outcomes. Notably, a ceased tooth development of immature permanent teeth with open apices, regeneration of periodontal ligaments (PDL), and pulp is highly expected healing process. For regeneration, the scaffold is one of the critical components that carry biological benefits. Therefore, this study evaluated a decellularized human tooth as a scaffold for the PDL and pulp tissue regeneration. A tooth scaffold was fabricated using an effective decellularization method as reported in previous studies. PDL stem cells (PDLSCs) and dental pulp stem cells (DPSCs) obtained from human permanent teeth were inoculated onto decellularized scaffolds, then cultured to transplant into immunosuppressed mouse. After 9 weeks, PDLSCs and DPSCs that were inoculated onto decellularized tooth scaffolds and cultured in an in vivo demonstrated successful differentiation. In PDLSCs, a regeneration of the cementum/PDL complex could be expected. In DPSCs, the expression of genes related to revascularization and the hard tissue regeneration showed the possibility of pulp regeneration. This study suggested that the potential possible application of decellularized human tooth could be a scaffold in regeneration PDL and pulp tissue along with PDLSCs and DPSCs, respectively, as a novel treatment method.

NSD3-Induced Methylation of H3K36 Activates NOTCH Signaling to Drive Breast Tumor Initiation and Metastatic Progression.

Histone methyltransferase NSD3 is frequently dysregulated in human cancers, yet the epigenetic role of NSD3 during cancer development remains elusive. Here we report that NSD3-induced methylation of H3K36 is crucial for breast tumor initiation and metastasis. In patients with breast cancer, elevated expression of NSD3 was associated with recurrence, distant metastasis, and poor survival. In vivo, NSD3 promoted malignant transformation of mammary epithelial cells, a function comparable to that of HRAS. Furthermore, NSD3 expanded breast cancer-initiating cells and promoted epithelial-mesenchymal transition to trigger tumor invasion and metastasis. Mechanistically, the long isoform (full-length transcript) of NSD3, but not its shorter isoform lacking a catalytic domain, cooperated with EZH2 and RNA polymerase II to stimulate H3K36me2/3-dependent transactivation of genes associated with NOTCH receptor cleavage, leading to nuclear accumulation of NICD and NICD-mediated transcriptional repression of E-cadherin. Furthermore, mice harboring primary and metastatic breast tumors with overexpressed NSD3 showed sensitivity to NOTCH inhibition. Together, our findings uncover the critical epigenetic role of NSD3 in the modulation of NOTCH-dependent breast tumor progression, providing a rationale for targeting the NSD3-NOTCH signaling regulatory axis in aggressive breast cancer. SIGNIFICANCE: This study demonstrates the functional significance of histone methyltransferase NSD3 in epigenetic regulation of breast cancer stemness, EMT, and metastasis, suggesting NSD3 as an actionable therapeutic target in metastatic breast cancer.