HES1 as an Independent Prognostic Marker in Esophageal Squamous Cell Carcinoma

Expression analysis elucidates the roles of Nicastrin, Notch4, and Hes1 in prognosis and endocrine-therapy resistance in ER-positive breast cancer patients

Background and purpose

Although some proposed mechanisms responsible for tamoxifen resistance have already been present, further study is needed to determine the mechanisms underlying tamoxifen resistance more clearly. The critical role of Notch signaling has been described in promoting resistance in therapeutics, but there is little information about its role in tamoxifen resistance progression.

Experimental approach

In the present study, the expression of Notch pathway genes, including Notch4, nicastrin and the Notch downstream target Hes1 was evaluated using quantitative RT-PCR in 36 tamoxifen-resistant (TAM-R) and 36 tamoxifen-sensitive (TAM-S) patients. Expression data were correlated with the clinical outcome and survival of patients.

Findings/Results

mRNA levels of Notch4 (fold change = 2.7), nicastrin (fold change = 6.71), and Hes1 (fold change= 7.07) were significantly higher in TAM-R breast carcinoma patients compared to sensitive cases. We confirmed all these genes were co-expressed. Hence, it seems that Notch signaling is involved in tamoxifen resistance in our TAM-R patients. Obtained results showed that Hes1, nicastrin, and Notch4 mRNA upregulation was correlated with the N stage. The extracapsular nodal extension was associated with nicastrin and Notch4 overexpression. Moreover, nicastrin overexpression was correlated with perineural invasion. Hes1 upregulation was also associated with nipple involvement. Finally, the Cox regression proportional hazard test revealed that overexpression of nicastrin was an independent worse survival factor.

Conclusion and implications

Presumably, upregulation of the Notch pathway may be involved in tamoxifen resistance in breast cancer patients.

Signaling pathways and their potential therapeutic utility in esophageal squamous cell carcinoma

Esophageal cancer is a complex gastrointestinal malignancy with an extremely poor outcome. Approximately 80% of cases of this malignancy in Asian countries including India are of squamous cell origin, termed Esophageal Squamous Cell Carcinoma (ESCC).The five-year survival rate in ESCC patients is less than 20%. Neo-adjuvant chemo-radiotherapy (NACRT) followed by surgical resection remains the major therapeutic strategy for patients with operable ESCC. However, resistance to NACRT and local recurrence after initial treatment are the leading cause of dismal outcomes in these patients. Therefore, an alternative strategy to promote response to the therapy and reduce the post-operative disease recurrence is highly needed. At the molecular level, wide variations have been observed in tumor characteristics among different populations, nevertheless, several common molecular features have been identified which orchestrate disease progression and clinical outcome in the malignancy. Therefore, determination of candidate molecular pathways for targeted therapy remains the mainstream idea of focus in ESCC research. In this review, we have discussed the key signaling pathways associated with ESCC, i.e., Notch, Wnt, and Nrf2 pathways, and their crosstalk during disease progression. We further discuss the recent developments of novel agents to target these pathways in the context of targeted cancer therapy. In-depth research of the signaling pathways, gene signatures, and a combinatorial approach may help in discovering targeted therapy for ESCC.

Shooting at Moving and Hidden Targets-Tumour Cell Plasticity and the Notch Signalling Pathway in Head and Neck Squamous Cell Carcinomas

Head and Neck Squamous Cell Carcinoma (HNSCC) is often aggressive, with poor response to current therapies in approximately 40-50% of the patients. Current therapies are restricted to operation and irradiation, often combined with a small number of standard-of-care chemotherapeutic drugs, preferentially for advanced tumour patients. Only very recently, newer targeted therapies have entered the clinics, including Cetuximab, which targets the EGF receptor (EGFR), and several immune checkpoint inhibitors targeting the immune receptor PD-1 and its ligand PD-L1. HNSCC tumour tissues are characterized by a high degree of intra-tumour heterogeneity (ITH), and non-genetic alterations that may affect both non-transformed cells, such as cancer-associated fibroblasts (CAFs), and transformed carcinoma cells. This very high degree of heterogeneity likely contributes to acquired drug resistance, tumour dormancy, relapse, and distant or lymph node metastasis. ITH, in turn, is likely promoted by pronounced tumour cell plasticity, which manifests in highly dynamic and reversible phenomena such as of partial or hybrid forms of epithelial-to-mesenchymal transition (EMT), and enhanced tumour stemness. Stemness and tumour cell plasticity are strongly promoted by Notch signalling, which remains poorly understood especially in HNSCC. Here, we aim to elucidate how Notch signal may act both as a tumour suppressor and proto-oncogenic, probably during different stages of tumour cell initiation and progression. Notch signalling also interacts with numerous other signalling pathways, that may also have a decisive impact on tumour cell plasticity, acquired radio/chemoresistance, and metastatic progression of HNSCC. We outline the current stage of research related to Notch signalling, and how this pathway may be intricately interconnected with other, druggable targets and signalling mechanisms in HNSCC.

MAEL Cancer-Testis Antigen as a Diagnostic Marker in Primary Stages of Gastric Cancer with Helicobacter pylori Infection

PURPOSE

Gastric cancer (GC) is the third leading cause of cancer related deaths in the world. Cancer testis antigens (CTAs) are involved in tumor progression of various cancers. These markers have not any expression or minimally expression in normal tissues, highlighting them as efficient methods for molecular targeted therapy. In the present study, we assessed the role of MAEL as a CTA in biology of GC and risk of Helicobacter Pylori (H pylori) infection.

METHODS

Levels of MAEL mRNA expression in 80 GC tumor tissues were compared to their corresponding normal margins using the real-time polymerase chain reaction.

RESULTS

There was a significant correlation between MAEL expression and tumor stage (p = 0.050). There were also significant correlations between MAEL expression and tumor grade (p = 0.015) and depth of invasion (p = 0.030) among the H pylori negative cases.

CONCLUSIONS

MAEL is probably associated with aggressiveness of primary-stage tumors and can be introduced as an efficient marker for the early detection and also H pylori infected tumors in GC patients.

SOX2/SALL4 stemness axis modulates Notch signaling genes to maintain self-renewal capacity of esophageal squamous cell carcinoma

Stemness phenotype is considered as the centerpiece of cancer biology due to its potential in conventional chemo-radiotherapy resistance and tumor recurrence after clinical intervention. This feature in tumor mass belongs to activation of core regulatory stemness factors and different cell signaling pathways in cancer stem cells. We aimed in this study to elucidate contribution of Notch signaling pathway in stemness state of esophageal squamous cell carcinoma (ESCC) through their relevance with stem cell markers SOX2 and SALL4. 50 ESCC tumor and related margin normal tissues were considered and categorized based on SOX2/SALL4 expression pattern, and mRNA levels of Notch signaling genes including ligands, receptors, target genes, and transcriptional coactivator were analyzed in the selected groups using qRT-PCR. Concomitant overexpression of stem cell markers SOX2 and SALL4 in ESCCs upregulated the involved genes in Notch signaling pathway. Upregulation of Notch pathway genes associated with depth of tumor invasion and lymph node metastasis of ESCC. Based on biological function of SOX2 and SALL4 axis in stemness state potential, our results may suggest contribution of Notch signaling pathway in self-renewal capacity of ESCCs, as well as invasion and metastasis of the disease. To the best of our knowledge, this is the first report elucidating the crosstalk between SOX2/SALL4 stemness factors and Notch signaling pathway in cancer research.

TWIST1 correlates with Notch signaling pathway to develop esophageal squamous cell carcinoma

Notch signaling pathway mediates different biological processes including stem cell self-renewal, progenitor cell fate decision, and terminal differentiation. TWIST1 plays a key role in tumor development and metastasis through inducing epithelial-mesenchymal transition (EMT). Expression of the core transcriptional complex of Notch pathway and its target genes, as well as TWIST1 overexpression, are closely related to the aggressive clinicopathological variables of esophageal squamous cell carcinoma (ESCC). Here we aimed to functionally elucidate probable crosstalk between TWIST1 and Notch pathway in ESCCs. Correlation between TWIST1 and Notch target genes was analyzed in 50 ESCCs and corresponding normal tissues. Using retroviral system, enforced expression of TWIST1 was established in ESCC line KYSE-30 cells and expression of Notch signaling genes was assessed. Significant correlation between TWIST1 and HEY1/HEY2 expression was found in different pathological variable of ESCC poor prognosis. Induced expression of TWIST1 in KYSE-30 cells caused a noteworthy increase of Notch pathway genes expression revealing regulatory role of TWIST1 on Notch signaling genes in the cells. Based on existed correlations between expression of TWIST1 and Notch pathway genes in different pathological features of ESCC patients, as well as KYSE-30 cell line, we may extrapolate that TWIST1 is involved in aggressiveness of the disease through regulation of Notch signaling genes. To the best of knowledge, this is the first report describing the impact of TWIST1 on Notch cascade genes in ESCC.

Role of MAML1 in targeted therapy against the esophageal cancer stem cells

Background

Esophageal cancer is the sixth-leading cause of cancer-related deaths worldwide. Cancer stem cells (CSCs) are the main reason for tumor relapse in esophageal squamous cell carcinoma (ESCC). The NOTCH pathway is important in preservation of CSCs, therefore it is possible to target such cells by targeting MAML1 as the main component of the NOTCH transcription machinery.

Methods

In present study we isolated the CD44+ ESCC CSCs and designed a MAML1-targeted therapy to inhibit the NOTCH signaling pathway. CSCs were isolated using magnetic cell sorting utilizing the CD44 cell surface marker. Several stem cell markers were analyzed in the levels of protein and mRNA expression. The isolated CSCs were characterized in vivo in NUDE mice. Biological role of MAML1 was assessed in isolated CD44+ CSCs. A drug resistance assay was also performed to assess the role of MAML1 in CD44+ CSCs with 5FU resistance.

Results

The CD44+ CSCs had ability to form tumors in NUDE mice. MAML1 silencing caused a significant decrease (p = 0.019) and ectopic expression caused a significant increase in migration of CD44+ CSCs (p = 0.012). Moreover, MAML1 silencing and ectopic expression significantly increased and decreased 5FU resistance, respectively (p < 0.05). MAML1 silencing significantly increased the number of cells in G1 phase (p = 0.008), and its ectopic expression significantly increased the number of CD44+ CSCS in S phase (p = 0.037).

Conclusions

MAML1 may be utilized for targeted therapy with a low side effect to eliminate the CD44+ CSCs through inhibition of canonical NOTCH pathway in ESCC patients.

MAML1 regulates EMT markers expression through NOTCH-independent pathway in breast cancer cell line MCF7

Tumor relapse is the main cause of breast cancer related deaths and metastasis due to epithelial-mesenchymal transition (EMT) having a critical role in this process. MAML1 is the main co activator of NOTCH signaling pathway and its role in EMT remains unknown. In this study, this role was evaluated through overexpression and knockdown study of MAML1 in MCF7 and MDA-MB-231 cells. MAML1 overexpression up regulated the epithelial and down regulated the mesenchymal markers. In addition, MAML1 silencing decreased epithelial and increased mesenchymal markers. Notch inhibition using γ-secretase inhibitor resulted in increased E-cadherin expression. MAML1 ectopic expression, further increased E-cadherin expression with inhibition of NOTCH signaling. Wound healing assay showed that MAML1 overexpression decreases the rate of migration, while MAML1 silencing increases this rate significantly. In conclusion, our data indicated that MAML1 negatively regulates EMT markers expression in breast cancer cells.

Correlation between SALL4 stemness marker and bone morphogenetic protein signaling genes in esophageal squamous cell carcinoma

SALL4, as a stemness marker, plays a key role in the maintenance of pluripotency and self-renewal of cancer stem cells. To elucidate probable linkage between SALL4 stemness marker and bone morphogenetic protein (BMP) cell signaling pathway, we aimed to analyze the expression levels of the related genes in esophageal squamous cell carcinoma (ESCC) patients. Tumoral and corresponding margin normal tissues from 50 treatment-naive ESCC patients were subjected for expression analysis using relative comparative real-time reverse transcription polymerase chain reaction. There were significant correlations between SALL4 mRNA and BMP signaling target genes expression including SIZN1, VENTX, and DIDO1 (P < 0.01). Tight associations of gene expression were observed in primary stages of tumor progression (stages I/II), and the invaded tumors to the adventitia (T3/T4). Furthermore, significant correlations between the expression of BMP signaling target genes were observed (P < 0.01). SALL4 may play role in tumorigenesis and tumor cell invasiveness of ESCC through correlation with BMP signaling genes.

WNT and NOTCH signaling pathways as activators for epidermal growth factor receptor in esophageal squamous cell carcinoma

Background

Esophageal squamous cell carcinoma (ESCC) is the most common histological type of esophageal cancer, with a poor prognosis. Deregulation of WNT and NOTCH signaling pathways is important in ESCC progression, which can be due to either malfunction of their components or crosstalk with other pathways. Therefore, identification of new crosstalk between such pathways may be effective to introduce new strategies for targeted therapy of cancer. A correlation study was performed to assess the probable interaction between growth factor receptors and WNT/NOTCH pathways via the epidermal growth factor receptor (EGFR) and Musashi1 (MSI1), respectively.

Methods

Levels of MSI1/EGFR mRNA expression in tumor tissues from 48 ESCC patients were compared to their corresponding normal tissues using real-time polymerase chain reaction.

Results

There was a significant correlation between EGFR and MSI1 expression (p = 0.05). Moreover, there was a significant correlation between EGFR/MSI1 expression and grade of tumor differentiation (p = 0.02).

Conclusion

This study confirms a direct correlation between MSI1 and EGFR and may support the important role of MSI1 in activation of EGFR through NOTCH/WNT pathways in ESCC.

Contribution of KCTD12 to esophageal squamous cell carcinoma

Background

It has been shown that the expression of potassium channel tetramerization domain containing 12 (KCTD12) as a regulator of GABAB receptor signaling is reversely associated with gastrointestinal stromal tumors. In present study we examined the probable role of KCTD12 in regulation of several signaling pathways and chromatin remodelers in esophageal squamous cell carcinoma (ESCC).

Methods

KCTD12 ectopic expression was done in KYSE30 cell line. Comparative quantitative real time PCR was used to assess the expression of stem cell factors and several factors belonging to the WNT/NOTCH and chromatin remodeling in transfected cells in comparison with non-transfected cells.

Results

We observed that the KCTD12 significantly down regulated expression of NANOG, SOX2, SALL4, KLF4, MAML1, PYGO2, BMI1, BRG1, MSI1, MEIS1, EGFR, DIDO1, ABCC4, ABCG2, and CRIPTO1 in transfected cells in comparison with non-transfected cells. Migration assay showed a significant decrease in cell movement in ectopic expressed cells in comparison with non-transfected cells (p = 0.02). Moreover, KCTD12 significantly decreased the 5FU resistance in transfected cells (p = 0.01).

Conclusions

KCTD12 may exert its inhibitory role in ESCC through the suppression of WNT /NOTCH, stem cell factors, and chromatin remodelers and can be introduced as an efficient therapeutic marker.

MAML1 and TWIST1 co-overexpression promote invasion of head and neck squamous cell carcinoma

AIMS

Head and neck squamous cell carcinoma (HNSCC) is the seventh most common cancer worldwide with considerable morbidity and mortality. Invasion and metastasis of HNSCC is a complex process involving multiple molecules and signaling pathways. Twist Family BHLH Transcription Factor 1 (TWIST1) and Mastermind-like 1 (MAML1) are essential in induction of epithelial-mesenchymal transition through direct regulation of implicated molecules in cellular adhesion, migration and invasion. Our aim in this study was to assess the clinical significance of MAML1 and TWIST1 expression in HNSCC, and elucidate the probable correlation between these genes to exhibit their possible associations with progression and metastasis of the disease.

METHODS

The gene expression profile of MAML1 and TWIST1 was assessed in fresh tumoral compared to distant tumor-free tissues of 55 HNSCC patients using quantitative real-time Polymerase chain reaction (PCR).

RESULTS

Significant overexpression of MAML1 and TWIST1 mRNA was observed in 49.1% and 38.2% (P ˂ 0.05) of tumor specimens, respectively. Overexpression of MAML1 was associated with vascular invasion (P = 0.048). Concomitant overexpression of MAML1 and TWIST1 was significantly correlated to each other (P = 0.004). Co-overexpression of the genes was significantly correlated to the various clinicopathological indices of poor prognosis including depth of tumor invasion (P < 0.01), lymphatic invasion and grade of tumor cell differentiation (P < 0.05).

CONCLUSIONS

Significant correlation between MAML1 and TWIST1 in HNSCC was revealed. This study was the first report elucidating MAML1 clinical relevance in HNSCC. These new findings suggest an oncogenic role for concomitant expression of MAML1 and TWIST1 genes in HNSCC invasion and metastasis.

The notch pathway is activated in neoplastic progression in esophageal squamous cell carcinoma

The Notch signaling pathway is integral to normal human development and homeostasis and has a deterministic function on cell differentiation. Recent studies suggest aberrant Notch signaling may contribute to neoplastic progression by an increase in stem cell survival, chemoresistance, and the promotion of epithelial-to-mesenchymal transition. The goals of our study were to determine, utilizing quantitative technologies, the expression of activated Notch 1 in esophageal squamous cell carcinoma (SCC) and to determine the relationship between Notch 1 expression and various clinicopathologic parameters. Immunohistochemical staining for Notch intracellular domain (NICD) was performed on 60 consecutive cases of esophageal squamous cell carcinoma, 42 cases of benign esophageal squamous epithelium, and 13 cases of eosinophilic esophagitis diagnosed in our department from 2007 through 2015, and exact nuclear staining and nuclear characteristics were graded using the Vectra imaging system. Clinicopathologic data (gender, age at diagnosis, smoking status, tumor grade, tumor stage, tumor location, and survival) were collected for each SCC case and these were correlated with NICD staining. Cases of esophageal SCC demonstrated significantly higher NICD staining compared to cases of benign and reactive esophageal epithelium (P=.003 and .005, respectively). Among cases of esophageal SCC, nuclear NICD staining was significantly correlated with both tumor grade and stage. Following classification and regression tree analysis, esophageal SCC patients with increased NICD expression were found to be more likely to die from their disease than those with lower levels of expression. Taken together, the findings suggest that increased Notch 1 may contribute to the development and aggressiveness of esophageal SCC.

Overexpressed PTOV1 associates with tumorigenesis and progression of esophageal squamous cell carcinoma

PTOV1 has been demonstrated to play an extensive role in many types of cancers. This study takes the first step to clarify the potential relationship between esophageal squamous cell carcinoma and PTOV1 expression and highlight the link between PTOV1 and the tumorigenesis, progression, and prognosis of esophageal squamous cell carcinoma. PTOV1 expression was detected by quantitative reverse transcription polymerase chain reaction and western blotting or immunohistochemical staining in esophageal squamous cell carcinoma cell lines, esophageal squamous cell carcinoma tissues, and its paired adjacent non-cancerous tissues. Moreover, we have analyzed the relationship between PTOV1 expression and clinicopathological features of esophageal squamous cell carcinoma. Survival analysis and Cox regression analysis were used to assess its prognostic significance. We found that PTOV1 expression was significantly higher in the esophageal squamous cell carcinoma cell lines and tissues at messenger RNA level (p < 0.001) and protein level (p < 0.001). Gender, tumor size, or differentiation was tightly associated with the PTOV1 expression. Lymph node involvement (p < 0.001) and TNM stage (p < 0.001) promoted a high PTOV1 expression. A prognostic significance of PTOV1 was also found by Log-rank method, and the overexpression of PTOV1 was related to a shorter OS and DFS. Multiple Cox regression analysis indicated overexpressed PTOV1 as an independent indicator for adverse prognosis. In conclusion, this study takes the lead to demonstrate that the overexpressed PTOV1 plays a vital role in the tumorigenesis and progression of esophageal squamous cell carcinoma, and it is potentially a valuable prognostic predicator and new chemotherapeutic target for esophageal squamous cell carcinoma.

Role of MAML1 and MEIS1 in Esophageal Squamous Cell Carcinoma Depth of Invasion

Homeobox (HOX) transcription factors and NOTCH signaling pathway are critical regulators of stem cell functions, cell fate in development and homeostasis of gastrointestinal tissues. In the present study, we analyzed cross talk between NOTCH pathway and HOX genes through assessment of probable correlation betweenMAML1 and MEIS1 as the main transcription factor of NOTCH pathway and enhancer of HOX transcriptional machinery, respectively in esophageal squamous cell carcinoma (ESCC) patients. Fifty one ESCC cases were enrolled to assess the levels of Meis1 and Maml1 mRNA expression using real-time polymerase chain reaction (PCR). Only 3 out of 51 (5.9%) cases had MEIS1/MAML1 under expression and 2/51 (3.9%) cases had MEIS1/MAML1over expression. Nine out of 51 samples (17.6%) have shown MEIS1 under expression and MAML1 over expression. There was a significant correlation between MAML1and MEIS1mRNA expressions (p ≤ 0.05). There were significant correlations between MEIS1 under/MAML1 over expressed cases and tumor location (p = 0.05), tumor depth of invasion (p = 0.011), and sex (p = 0.04). Our results showed that MEIS1 may have a negative role in regulation of MAML1expression during the ESCC progression.

Role of Msi1 and MAML1 in Regulation of Notch Signaling Pathway in Patients with Esophageal Squamous Cell Carcinoma

PURPOSE

Developmental pathways such as Wnt and Notch are involved in different cellular functions from the cell cycle regulation to self-renewal. Therefore, aberrations in these pathways may cause tumorigenesis. Msi1 has a critical regulatory role for the Wnt and Notch pathways. In the present study, we have assessed the probable correlation between the Msi1 and MAML1 in esophageal squamous cell carcinoma (ESCC) progression and metastasis.

METHODS

Levels of Msi1 and MAML1 mRNA expression in 51 ESCC patients were compared to the normal tissues using real-time polymerase chain reaction (PCR).

RESULTS

Nine out of 51 (17.6 %) cases had Msi1/MAML1 overexpression, and there was a significant correlation between such overexpressed cases and tumor location (p = 0.013).

CONCLUSIONS

We showed that there is not any direct correlation and feedback between the Msi1 and MAML1 in ESCC patients.

HES1 mRNA expression is associated with survival in sinonasal squamous cell carcinoma

OBJECTIVE

In squamous cell carcinoma of the pharynx and larynx, NOTCH1 downstream signaling has been shown to be activated. The NOTCH1 signaling pathway has not been examined in detail for sinonasal squamous cell carcinomas (SNSCCs). The aim of this study was to evaluate NOTCH1 signaling by mRNA expression analysis and to examine the occurrence of NOTCH1 mutations in SNSCC.

STUDY DESIGN

In a retrospective study, we analyzed tissues from 44 SNSCCs and 56 head and neck squamous cell carcinomas (HNSCCs) at other locations. Expression of NOTCH1, NOTCH3, HES1, HEY1, and JAG1 mRNA were measured by using quantitative real-time polymerase chain reaction (q-rtPCR). In SNSCC, NOTCH1 mutations were evaluated with sequencing of seven selected exons.

RESULTS

Expression of NOTCH1, HEY1, and JAG1 at the mRNA level were significantly higher in tumor tissue compared with normal tissue. In SNSCC, the subgroup of patients with high expression (5th quintile) of HES1 mRNA was associated with better survival (P = .04); however these patients with high expression of HES1 mRNA had also a more favorable tumor stage and grade and more unfavorable resections representing potential confounders.

CONCLUSIONS

Key components of NOTCH1 are upregulated at the mRNA level in HNSCCs. The mechanism, clinical significance, and potential therapeutic options should therefore be further evaluated.

Does Notch play a tumor suppressor role across diverse squamous cell carcinomas?

The role of Notch pathway in tumorigenesis is highly variable. It can be tumor suppressive or pro‐oncogenic, typically depending on the cellular context. Squamous cell carcinoma (SCC) is a cancer of the squamous cell, which can occur in diverse human tissues. SCCs are one of the most frequent human malignancies for which the pathologic mechanisms remain elusive. Recent genomic analysis of diverse SCCs identified marked levels of mutations in NOTCH1, implicating Notch signaling pathways in the pathogenesis of SCCs. In this review, evidences highlighting NOTCH's role in different types of SCCs are summarized. Moreover, based on accumulating structural information of the NOTCH receptor, the functional consequences of NOTCH1 gene mutations identified from diverse SCCs are analyzed, emphasizing loss of function of Notch in these cancers. Finally, we discuss the convergent view on an intriguing possibility that Notch may function as tumor suppressor in SCCs across different tissues. These mechanistic insights into Notch signaling pathways will help to guide the research of SCCs and development of therapeutic strategies for these cancers.

Inhibition of Notch3 prevents monocrotaline-induced pulmonary arterial hypertension

It has been shown that activation of Notch3 signaling is involved in the development of pulmonary arterial hypertension (PAH) by stimulating pulmonary arteries remodeling, while the molecular mechanisms underlying this are still largely unknown. The aims of this study are to address these issues. Monocrotaline dramatically increased right ventricle systolic pressure to 39.0 ± 2.6 mmHg and right ventricle hypertrophy index to 53.4 ± 5.3% (P < 0.05 versus control) in rats, these were accompanied with significantly increased proliferation and reduced apoptosis of pulmonary vascular cells as well as pulmonary arteries remodeling. Treatment of PAH model with specific Notch inhibitor DAPT significantly reduced right ventricle systolic pressure to 26.6 ± 1.3 mmHg and right ventricle hypertrophy index to 33.5 ± 2.6% (P < 0.05 versus PAH), suppressed proliferation and enhanced apoptosis of pulmonary vascular cells as well as inhibited pulmonary arteries remodeling. Our results further indicated that level of Notch3 protein and NICD3 were increased in MCT-induced model of PAH, this was accompanied with elevation of Skp2 and Hes1 protein level and reduction of P27Kip1. Administration of rats with DAPT-prevented MCT induced these changes. Our results suggest that Notch3 signaling activation stimulated pulmonary vascular cells proliferation by Skp2-and Hes1-mediated P27Kip1 reduction, and Notch3 might be a new target to treat PAH.