PRRX1 isoforms cooperate with FOXM1 to regulate the DNA damage response in pancreatic cancer cells

PRRX1-TOP2A interaction is a malignancy-promoting factor in human malignant peripheral nerve sheath tumours

BACKGROUND

Paired related-homeobox 1 (PRRX1) is a transcription factor in the regulation of developmental morphogenetic processes. There is growing evidence that PRRX1 is highly expressed in certain cancers and is critically involved in human survival prognosis. However, the molecular mechanism of PRRX1 in cancer malignancy remains to be elucidated.

METHODS

PRRX1 expression in human Malignant peripheral nerve sheath tumours (MPNSTs) samples was detected immunohistochemically to evaluate survival prognosis. MPNST models with PRRX1 gene knockdown or overexpression were constructed in vitro and the phenotype of MPNST cells was evaluated. Bioinformatics analysis combined with co-immunoprecipitation, mass spectrometry, RNA-seq and structural prediction were used to identify proteins interacting with PRRX1.

RESULTS

High expression of PRRX1 was associated with a poor prognosis for MPNST. PRRX1 knockdown suppressed the tumorigenic potential. PRRX1 overexpressed in MPNSTs directly interacts with topoisomerase 2 A (TOP2A) to cooperatively promote epithelial-mesenchymal transition and increase expression of tumour malignancy-related gene sets including mTORC1, KRAS and SRC signalling pathways. Etoposide, a TOP2A inhibitor used in the treatment of MPNST, may exhibit one of its anticancer effects by inhibiting the PRRX1-TOP2A interaction.

CONCLUSION

Targeting the PRRX1-TOP2A interaction in malignant tumours with high PRRX1 expression might provide a novel tumour-selective therapeutic strategy.

Paired-related homeobox 1 induces epithelial-mesenchymal transition in oesophageal squamous cancer

BACKGROUND

It is unclear that paired-related homeobox 1 (PRRX1) induces epithelial-mesenchymal transition (EMT) in oesophageal cancer and the specific function of PRRX1 in oesophageal cancer metastasis.

AIM

To assess the significance of PRRX1 expression and investigate the mechanism of EMT in oesophageal cancer metastasis.

METHODS

Detect the expression of PRRX1 by immunohistochemistry in oesophageal tumour tissues and adjacent normal oesophageal tissues; the PRRX1 short hairpin RNA (shRNA) or blank vector lentiviral gene delivery system was transfected into cells; cell proliferation assay, soft agar colony formation assays, cell invasion and migration assays and animal studies were used to observe cells biological characteristics In vitro and in vivo; XAV939 and LiCl were used to alter the activity of Wnt/β-catenin pathway. Immunofluorescence staining and western blot analysis were used to detect protein expression of EMT markers and Wnt/β-catenin pathway.

RESULTS

PRRX1 is expressed at high levels in oesophageal cancer specimens and is closely related to tumour metastasis in patients with oesophageal cancer. Regulation of PRRX1 expression might exert obvious effects on cell proliferation, especially the migration and invasion of oesophageal cancer cells. Moreover, silencing PRRX1 expression using a shRNA produced the opposite effects. In addition, when PRRX1 was overexpressed, inhibition of the Wnt/β-catenin pathway with XAV939 negated the effect of PRRX1 on EMT, whereas when PRRX1 was downregulated, activation of the Wnt/β-catenin pathway with LiCl impaired the effect on EMT.

CONCLUSION

PRRX1 is upregulated in oesophageal cancer is closely correlated with cancer metastasis. Additionally, PRRX1 induces EMT in oesophageal cancer metastasis through activation of Wnt/β-catenin signalling.

Foxm1 haploinsufficiency drives clonal hematopoiesis and promotes a stress-related transition to hematologic malignancy in mice

Clonal hematopoiesis plays a critical role in the initiation and development of hematologic malignancies. In patients with del(5q) myelodysplastic syndrome (MDS), the transcription factor FOXM1 is frequently downregulated in CD34+ cells. In this study, we demonstrated that Foxm1 haploinsufficiency disturbed normal hematopoiesis and conferred a competitive repopulation advantage for a short period. However, it impaired the long-term self-renewal capacity of hematopoietic stem cells, recapitulating the phenotypes of abnormal hematopoietic stem cells observed in patients with MDS. Moreover, heterozygous inactivation of Foxm1 led to an increase in DNA damage in hematopoietic stem/progenitor cells (HSPCs). Foxm1 haploinsufficiency induced hematopoietic dysplasia in a mouse model with LPS-induced chronic inflammation and accelerated AML-ETO9a-mediated leukemogenesis. We have also identified Parp1, an important enzyme that responds to various types of DNA damage, as a target of Foxm1. Foxm1 haploinsufficiency decreased the ability of HSPCs to efficiently repair DNA damage by downregulating Parp1 expression. Our findings suggest that the downregulation of the Foxm1-Parp1 molecular axis may promote clonal hematopoiesis and reduce genome stability, contributing to del(5q) MDS pathogenesis.

hSSB1 (NABP2/OBFC2B) modulates the DNA damage and androgen-induced transcriptional response in prostate cancer

BACKGROUND

Activation and regulation of androgen receptor (AR) signaling and the DNA damage response impact the prostate cancer (PCa) treatment modalities of androgen deprivation therapy (ADT) and radiotherapy. Here, we have evaluated a role for human single-strand binding protein 1 (hSSB1/NABP2) in modulation of the cellular response to androgens and ionizing radiation (IR). hSSB1 has defined roles in transcription and maintenance of genome stability, yet little is known about this protein in PCa.

METHODS

We correlated hSSB1 with measures of genomic instability across available PCa cases from The Cancer Genome Atlas (TCGA). Microarray and subsequent pathway and transcription factor enrichment analysis were performed on LNCaP and DU145 prostate cancer cells.

RESULTS

Our data demonstrate that hSSB1 expression in PCa correlates with measures of genomic instability including multigene signatures and genomic scars that are reflective of defects in the repair of DNA double-strand breaks via homologous recombination. In response to IR-induced DNA damage, we demonstrate that hSSB1 regulates cellular pathways that control cell cycle progression and the associated checkpoints. In keeping with a role for hSSB1 in transcription, our analysis revealed that hSSB1 negatively modulates p53 and RNA polymerase II transcription in PCa. Of relevance to PCa pathology, our findings highlight a transcriptional role for hSSB1 in regulating the androgen response. We identified that AR function is predicted to be impacted by hSSB1 depletion, whereby this protein is required to modulate AR gene activity in PCa.

CONCLUSIONS

Our findings point to a key role for hSSB1 in mediating the cellular response to androgen and DNA damage via modulation of transcription. Exploiting hSSB1 in PCa might yield benefits as a strategy to ensure a durable response to ADT and/or radiotherapy and improved patient outcomes.

PRRX1 promotes colorectal cancer stemness and chemoresistance via the JAK2/STAT3 axis by targeting IL-6

Background

Stemness acquirement is one of the hallmarks of cancer and the major reason for the chemoresistance and poor prognosis of colorectal cancer (CRC). Previous research has revealed the stimulatory role of paired related homeobox 1 (PRRX1) on CRC metastasis. However, the role of PRRX1 in stemness acquirement and chemoresistance of CRC is still not clear.

Methods

A retrospective cohort study was performed to investigate the relationship between PRRX1 expression and multiple clinicopathological characteristics of CRC patients. The functional effects of PRRX1 on stemness and chemoresistance of CRC cells were validated by in vitro and in vivo assays. Gene set enrichment analysis (GSEA) and JASPAR software were performed to predict the underlying mechanisms. Enzyme-linked immunosorbent assay (ELISA), Western blot, immunofluorescence, and dual-luciferase reporter assays were used to confirm the PRRX1-mediated signaling and its downstream factors.

Results

The expression of PRRX1 was up-regulated in CRC tissues and cell lines compared to normal epithelial tissues and cell lines. High expression of PRRX1 was tightly associated with the metastasis, chemoresistance, and poor prognosis of CRC patients. Additionally, PRRX1 significantly promoted the proliferation, viability, stemness, and chemoresistance of CRC cells, as well as the activation of the interleukin-6 (IL-6)/JAK2/STAT3 axis. Inhibiting the expression of IL-6 dramatically eliminated the effects of PRRX1 on CRC cell stemness and chemoresistance.

Conclusions

PRRX1 plays a vital role in the stemness and chemoresistance of CRC cells via JAK2/STAT3 signaling by targeting IL-6. Further, PRRX1 may be a valid biomarker for predicting the effect of chemotherapy and prognosis of CRC patients.

Aberrant transcription factors in the cancers of the pancreas

Transcription factors (TFs) are essential for proper activation of gene set during the process of organogenesis, differentiation, lineage specificity. Reactivation or dysregulation of TFs regulatory networks could lead to deformation of organs, diseases including various malignancies. Currently, understanding the mechanism of oncogenesis became necessity for the development of targeted therapeutic strategy for different cancer types. It is evident that many TFs go awry in cancers of the pancreas such as pancreatic ductal adenocarcinoma (PDAC) and pancreatic neuroendocrine neoplasms (PanNENs). These mutated or dysregulated TFs abnormally controls various signaling pathways in PDAC and PanNENs including RTK, PI3K-PTEN-AKT-mTOR, JNK, TGF-β/SMAD, WNT/β-catenin, SHH, NOTCH and VEGF which in turn regulate different hallmarks of cancer. Aberrant regulation of such pathways have been linked to the initiation, progression, metastasis, and resistance in pancreatic cancer. As of today, a number of TFs has been identified as crucial regulators of pancreatic cancer and a handful of them shown to have potential as therapeutic targets in pre-clinical and clinical settings. In this review, we have summarized the current knowledge on the role and therapeutic usefulness of TFs in PDAC and PanNENs.

PRRX1 Is a Novel Prognostic Biomarker and Facilitates Tumor Progression Through Epithelial–Mesenchymal Transition in Uveal Melanoma

Uveal melanoma (UM) is the most common primary intraocular malignancy in adults. UM develops and is sustained by inflammation and immunosuppression from the tumor microenvironment (TME). This study sought to identify a reliable TME-related biomarker that could provide survival prediction and new insight into therapy for UM patients. Based on clinical characteristics and the RNA-seq transcriptome data of 80 samples from The Cancer Genome Atlas (TCGA) database, PRRX1 as a TME- and prognosis-related gene was identified using the ESTIMATE algorithm and the LASSO–Cox regression model. A prognostic model based on PRRX1 was constructed and validated with a Gene Expression Omnibus (GEO) dataset of 63 samples. High PRRX1 expression was associated with poorer overall survival (OS) and metastasis-free survival (MFS) in UM patients. Comprehensive results of the prognostic analysis showed that PRRX1 was an independent and reliable predictor of UM. Then the results of immunological characteristics demonstrated that higher expression of PRRX1 was accompanied by higher expression of immune checkpoint genes, lower tumor mutation burden (TMB), and greater tumor cell infiltration into the TME. Gene set enrichment analysis (GSEA) showed that high PRRX1 expression correlated with angiogenesis, epithelial–mesenchymal transition (EMT), and inflammation. Furthermore, downregulation of PRRX1 weakened the process of EMT, reduced cell invasion and migration of human UM cell line MuM-2B in vitro. Taken together, these findings indicated that increased PRRX1 expression is independently a prognostic factor of poorer OS and MFS in patients with UM, and that PRRX1 promotes malignant progression of UM by facilitating EMT, suggesting that PRRX1 may be a potential target for UM therapy.

Deregulation of Transcription Factor Networks Driving Cell Plasticity and Metastasis in Pancreatic Cancer

Pancreatic cancer is a very aggressive disease with 5-year survival rates of less than 10%. The constantly increasing incidence and stagnant patient outcomes despite changes in treatment regimens emphasize the requirement of a better understanding of the disease mechanisms. Challenges in treating pancreatic cancer include diagnosis at already progressed disease states due to the lack of early detection methods, rapid acquisition of therapy resistance, and high metastatic competence. Pancreatic ductal adenocarcinoma, the most prevalent type of pancreatic cancer, frequently shows dominant-active mutations in KRAS and TP53 as well as inactivation of genes involved in differentiation and cell-cycle regulation (e.g. SMAD4 and CDKN2A). Besides somatic mutations, deregulated transcription factor activities strongly contribute to disease progression. Specifically, transcriptional regulatory networks essential for proper lineage specification and differentiation during pancreas development are reactivated or become deregulated in the context of cancer and exacerbate progression towards an aggressive phenotype. This review summarizes the recent literature on transcription factor networks and epigenetic gene regulation that play a crucial role during tumorigenesis.

Discovery of Potent and Novel Dual PARP/BRD4 Inhibitors for Efficient Treatment of Pancreatic Cancer

Targeting poly(ADP-ribose) polymerase1/2 (PARP1/2) is a promising strategy for the treatment of pancreatic cancer with breast cancer susceptibility gene (BRCA) mutation. Inducing the deficiency of homologous recombination (HR) repair is an effective way to broaden the indication of PARP1/2 inhibitor for more patients with pancreatic cancer. Bromodomain-containing protein 4 (BRD4) repression has been reported to elevate HR deficiency. Therefore, we designed, synthetized, and optimized a dual PARP/BRD4 inhibitor III-16, with a completely new structure and high selectivity against PARP1/2 and BRD4. III-16 showed favorable synergistic antitumor efficacy in pancreatic cancer cells and xenografts by arresting cell cycle progression, inhibiting DNA damage repair, and promoting autophagy-associated cell death. Moreover, III-16 reversed Olaparib-induced acceleration of cell cycle progression and recovery of DNA repair. The advantages of III-16 over Olaparib suggest that dual PARP/BRD4 inhibitors are novel and promising agents for the treatment of advanced pancreatic cancer.

Circular RNA Paired-Related Homeobox 1 Promotes Gastric Carcinoma Cell Progression via Regulating MicroRNA-665/YWHAZ Axis

BACKGROUND

Gastric carcinoma (GC) is a ubiquitous malignant tumor worldwide. Circular RNA paired-related homeobox 1 (circ-PRRX1), one kind of non-coding RNAs, has been reported to act as a promoter in tumor growth. This study aims to explore the effects of circ-PRRX1 on proliferation, apoptosis, and metastasis in GC and the underlying regulatory mechanisms.

METHODS

The expression of circ-PRRX1, miR-665, and tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein zeta (YWHAZ) mRNA was analyzed by quantitative real-time polymerase chain reaction (qRT-PCR). Western blot was used to analyze YWHAZ protein expression. 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2-Htetrazolium bromide (MTT), flow cytometry, and transwell assay were carried out to assess the viability, apoptosis, migration, and invasion in GC cells. The interaction between miR-665 and circ-PRRX1 or YWHAZ was predicted by StarBase v2.0 and identified by dual-luciferase reporter system. Xenograft mouse model was employed to determine the effects of circ-PRRX1 knockdown on GC growth in vivo.

RESULTS

Compared with normal tissues and cells, circ-PRRX1 and YWHAZ levels were upregulated, and miR-665 was downregulated in GC tissues and cells. Functionally, circ-PRRX1 knockdown inhibited the viability, migration, and invasion and promoted apoptosis in GC cells, whereas anti-miR-665 abolished these effects. Mechanistically, circ-PRRX1 was confirmed as a sponge of miR-665 to regulate YWHAZ expression. Xenograft mouse model suggested that circ-PRRX1 knockdown reduced GC cells growth in vivo.

CONCLUSION

Circ-PRRX1 knockdown suppressed GC development by targeting miR-665 to inhibit YWHAZ expression, and the potential molecular mechanism may provide a theoretical basis for GC therapy.

The Prognostic Value of the DNA Repair Gene Signature in Head and Neck Squamous Cell Carcinoma

Purpose

To construct a prognostic signature composed of DNA repair genes to effectively predict the prognosis of patients with head and neck squamous cell carcinoma (HNSCC).

Methods

After downloading the transcriptome and clinical data of HNSCC from the Cancer Genome Atlas (TCGA), 499 patients with HNSCC were equally divided into training and testing sets. In the training set, 13 DNA repair genes were screened using univariate proportional hazard (Cox) regression analysis and least absolute shrinkage and selection operator (LASSO) Cox regression analysis to construct a risk model, which was validated in the testing set.

Results

In the training and testing sets, there were significant differences in the clinical outcomes of patients in the high- and low-risk groups showed by Kaplan-Meier survival curves (P < 0.001). Univariate and multivariate Cox regression analyses showed that the risk score had independent prognostic predictive ability (P < 0.001). At the same time, the immune cell infiltration, immune score, immune-related gene expression, and tumor mutation burden (TMB) of patients with HNSCC were also different between the high- and low-risk groups (P < 0.05). Finally, we screened several chemotherapeutics for HNSCC, which showed significant differences in drug sensitivity between the high- and low-risk groups (P < 0.05).

Conclusion

This study constructed a 13-DNA-repair-gene signature for the prognosis of HNSCC, which could accurately and independently predict the clinical outcome of the patient. We then revealed the immune landscape, TMB, and sensitivity to chemotherapy drugs in different risk groups, which might be used to guide clinical treatment decisions.

The Regulatory Role of PRRX1 in Cancer Epithelial-Mesenchymal Transition

PRRX1 (paired related homeobox 1), a member of the paired homeobox family, exhibits an important role in tumor. It is closely correlated to the occurrence of epithelial-mesenchymal transition (EMT). PRRX1 is an important transcription factor regulating EMT and plays an important role in tumor progression. In the process of tumor metastasis, PRRX1 mainly regulates the occurrence of EMT in tumor cells through TGF-β signaling pathway, Wnt/β-catenin signaling pathway and Notch signaling pathway. PRRX1 is not only closely related to the tumor cell stemness but also involved in miRNA regulation of EMT. Therefore, PRRX1 may be a target for inhibiting the proliferation, metastasis and stemness of tumor cells. The current review provides a systemic profile of the regulatory role of PRRX1 in cancer epithelial-mesenchymal transition.

Prrx1 promotes stemness and angiogenesis via activating TGF-β/smad pathway and upregulating proangiogenic factors in glioma

Glioma is one of the most lethal cancers with highly vascularized networks and growing evidences have identified glioma stem cells (GSCs) to account for excessive angiogenesis in glioma. Aberrant expression of paired-related homeobox1 (Prrx1) has been functionally associated with cancer stem cells including GSCs. In this study, Prrx1 was found to be markedly upregulated in glioma specimens and elevated Prrx1 expression was inversely correlated with prognosis of glioma patients. Prrx1 potentiated stemness acquisition in non-stem tumor cells (NSTCs) and stemness maintenance in GSCs, accompanied with increased expression of stemness markers such as SOX2. Prrx1 also promoted glioma angiogenesis by upregulating proangiogenic factors such as VEGF. Consistently, silencing Prrx1 markedly inhibited glioma proliferation, stemness, and angiogenesis in vivo. Using a combination of subcellular proteomics and in vitro analyses, we revealed that Prrx1 directly bound to the promoter regions of TGF-β1 gene, upregulated TGF-β1 expression, and ultimately activated the TGF-β/smad pathway. Silencing TGF-β1 mitigated the malignant behaviors induced by Prrx1. Activation of this pathway cooperates with Prrx1 to upregulate the expression of stemness-related genes and proangiogenic factors. In summary, our findings revealed that Prrx1/TGF-β/smad signal axis exerted a critical role in glioma stemness and angiogeneis. Disrupting the function of this signal axis might represent a new therapeutic strategy in glioma patients.

ERN1 knockdown modifies the effect of glucose deprivation on homeobox gene expressions in U87 glioma cells

OBJECTIVE

The aim of the present investigation was to study the expression of genes encoding homeobox proteins ZEB2 (zinc finger E-box binding homeobox 2), TGIF1 (TGFB induced factor homeobox 1), SPAG4 (sperm associated antigen 4), LHX1 (LIM homeobox 1), LHX2, LHX6, NKX3-1 (NK3 homeobox 1), and PRRX1 (paired related homeobox 1) in U87 glioma cells in response to glucose deprivation in control glioma cells and cells with knockdown of ERN1 (endoplasmic reticulum to nucleus signaling 1), the major pathway of the endoplasmic reticulum stress signaling, for evaluation of it possible significance in the control of glioma growth through ERN1 signaling and chemoresistance.

METHODS

The expression level of homeobox family genes was studied in control (transfected by vector) and ERN1 knockdown U87 glioma cells under glucose deprivation condition by real-time quantitative polymerase chain reaction.

RESULTS

It was shown that the expression level of ZEB2, TGIF1, PRRX1, and LHX6 genes was up-regulated in control glioma cells treated by glucose deprivation. At the same time, the expression level of three other genes (NKX3-1, LHX1, and LHX2) was down-regulated. Furthermore, ERN1 knockdown of glioma cells significantly modified the effect glucose deprivation condition on the expression almost all studied genes. Thus, treatment of glioma cells without ERN1 enzymatic activity by glucose deprivation condition lead to down-regulation of the expression level of ZEB2 and SPAG4 as well as to more significant up-regulation of PRRX1 and TGIF1 genes. Moreover, the expression of LHX6 and NKX3-1 genes lost their sensitivity to glucose deprivation but LHX1 and LHX2 genes did not change it significantly.

CONCLUSIONS

The results of this investigation demonstrate that ERN1 knockdown significantly modifies the sensitivity of most studied homeobox gene expressions to glucose deprivation condition and that these changes are a result of complex interaction of variable endoplasmic reticulum stress related and unrelated regulatory factors and contributed to glioma cell growth and possibly to their chemoresistance.

Tumor suppressive microRNA-485-5p targets PRRX1 in human skin melanoma cells, regulating epithelial-mesenchymal transition and apoptosis

Melanoma is one of the most aggressive skin cancers. Existing evidence has reported the aberrant expression of microRNAs (miRNAs) in melanoma, but their putative targets and underlying downstream effects remain to be further understood. Herein, we explored the suppressive role of miR-485-5p in melanoma progression. Initial bioinformatics analyses showed that the PRRX1 gene was differentially expressed in melanoma, while miR-485-5p was predicted to be a potential regulatory miRNA binding to PRRX1 mRNA. We confirmed that PRRX1 was upregulated, while miR-485-5p was downregulated in human melanoma samples compared with adjacent normal skin tissues. We then showed that PRRX1 was a target gene of miR-485-5p by dual-luciferase reporter gene assay. Moreover, a reduction in the expression of PRRX1 and downregulation of important proteins of the transforming growth factor-beta (TGFβ) signaling pathway was observed after miR-485-5p overexpression. Furthermore, miR-485-5p overexpression or PRRX1 knockdown suppressed epithelial-mesenchymal transition, cell viability, migration, and invasion, and promoted cell apoptosis in melanoma cells. Our study demonstrates the tumor-suppressive functions of miR-485-5p in the development of human melanoma, providing a potential target for therapy.

Fork head box M1 regulates vascular endothelial growth factor-A expression to promote the angiogenesis and tumor cell growth of gallbladder cancer

BACKGROUND

Gallbladder cancer (GBC) is an aggressive type of biliary tract cancer that lacks effective therapeutic targets. Fork head box M1 (FoxM1) is an emerging molecular target associated with tumor progression in GBC, and accumulating evidence suggests that vascular endothelial growth factor (VEGF) promotes various tumors by inducing neoangiogenesis.

AIM

To investigate the role of FoxM1 and the angiogenesis effects of VEGF-A in primary GBC.

METHODS

Using immunohistochemistry, we investigated FoxM1 and VEGF-A expression in GBC tissues, paracarcinoma tissues and cholecystitis tissues. Soft agar, cell invasion, migration and apoptosis assays were used to analyze the malignant phenotype influenced by FoxM1 in GBC. Kaplan-Meier survival analysis was performed to evaluate the impact of FoxM1 and VEGF-A expression in GBC patients. We investigated the relationship between FoxM1 and VEGF-A by regulating the level of FoxM1. Next, we performed MTT assays and Transwell invasion assays by knocking out or overexpressing VEGF-A to evaluate its function in GBC cells. The luciferase assay was used to reveal the relationship between FoxM1 and VEGF-A. BALB/c nude mice were used to establish the xenograft tumor model.

RESULTS

FoxM1 expression was higher in GBC tissues than in paracarcinoma tissues. Furthermore, the high expression of Foxm1 in GBC was significantly correlated with a malignant phenotype and worse overall survival. Meanwhile, high expression of FoxM1 influenced angiogenesis; high expression of FoxM1 combined with high expression of VEGF-A was related to poor prognosis. Attenuated FoxM1 significantly suppressed cell proliferation, transfer and invasion in vitro. Knockdown of FoxM1 in GBC cells reduced the expression of VEGF-A. Luciferase assay showed that FoxM1 was the transcription factor of VEGF-A, and knockdown VEGF-A in FoxM1 overexpressed cells could partly reverse the malignancy phenotype of GBC cells. In this study, we found that FoxM1 was involved in regulation of VEGF-A expression.

CONCLUSION

FoxM1 and VEGF-A overexpression were associated with the prognosis of GBC patients. FoxM1 regulated VEGF-A expression, which played an important role in the progression of GBC.

Mesenchymal Plasticity Regulated by Prrx1 Drives Aggressive Pancreatic Cancer Biology

BACKGROUND & AIMS

Pancreatic ductal adenocarcinoma (PDAC) is characterized by a fibroblast-rich desmoplastic stroma. Cancer-associated fibroblasts (CAFs) have been shown to display a high degree of interconvertible states including quiescent, inflammatory, and myofibroblastic phenotypes; however, the mechanisms by which this plasticity is achieved are poorly understood. Here, we aim to elucidate the role of CAF plasticity and its impact on PDAC biology.

METHODS

To investigate the role of mesenchymal plasticity in PDAC progression, we generated a PDAC mouse model in which CAF plasticity is modulated by genetic depletion of the transcription factor Prrx1. Primary pancreatic fibroblasts from this mouse model were further characterized by functional in vitro assays. To characterize the impact of CAFs on tumor differentiation and response to chemotherapy, various coculture experiments were performed. In vivo, tumors were characterized by morphology, extracellular matrix composition, and tumor dissemination and metastasis.

RESULTS

Our in vivo findings showed that Prrx1-deficient CAFs remain constitutively activated. Importantly, this CAF phenotype determines tumor differentiation and disrupts systemic tumor dissemination. Mechanistically, coculture experiments of tumor organoids and CAFs showed that CAFs shape the epithelial-to-mesenchymal phenotype and confer gemcitabine resistance of PDAC cells induced by CAF-derived hepatocyte growth factor. Furthermore, gene expression analysis showed that patients with pancreatic cancer with high stromal expression of Prrx1 display the squamous, most aggressive, subtype of PDAC.

CONCLUSIONS

Here, we define that the Prrx1 transcription factor is critical for tuning CAF activation, allowing a dynamic switch between a dormant and an activated state. This work shows that Prrx1-mediated CAF plasticity has significant impact on PDAC biology and therapeutic resistance.

Identification of prognostic biomarkers associated with stromal cell infiltration in muscle-invasive bladder cancer by bioinformatics analyses

Muscle-invasive bladder cancer (MIBC) is one of the common malignant tumors. Patients with MIBC still have high tumor recurrence and progression rates after surgery. Bioinformatics analysis of stromal infiltration-related genes in the tumor microenvironment (TME) of MIBC patients was performed in this study to determine the major stromal cells types and biomarkers for their progression and poor prognosis. The ESTIMATE algorithm was applied to evaluate the stromal score and immune score of samples from MIBC patients in The Cancer Genome Atlas (TCGA) and found that stromal score was closely related to the clinical characteristics of the patients. The Gene Set Enrichment Analysis (GSEA) further revealed that stromal cells were involved in biological processes such as activation of leukocytes and positive regulation of cell migration during MIBC progression, as well as PI3K-Akt, MAPK, and Rap1 signaling pathways. Five hub genes related to prognosis, including ACTA2, COL5A1, DCN, LUM, and PRRX1 were identified by the Weighted Gene Co-Expression Network Analysis (WGCNA), Protein-Protein Interaction (PPI), survival analysis, and Oncomine, Gene Expression Omnibus (GEO) database validation. Besides, we identified five stromal cell types associated with overall survival time, among which chondrocytes and fibroblasts were identified as the major stromal cell types through correlation analysis. Finally, the Receiver Operating Characteristic (ROC) curve and immunohistochemistry were used to verify the diagnostic value and expression of hub genes in different invasive tumors. In summary, we investigated the biological behavior of stromal cells in the TME of MIBC to promote tumor progression obtained hub genes associated with progression and poor prognosis and identified the main stromal cells types in the TME.

PRRX1 isoform PRRX1A regulates the stemness phenotype and epithelial-mesenchymal transition (EMT) of cancer stem-like cells (CSCs) derived from non-small cell lung cancer (NSCLC)

Backgrounds

The 2 isoforms of paired-related homeobox 1 (PRRX1), PRRX1A and PRRX1B, are critical in regulating several kinds of cancers, and figure prominently in the maintenance of stemness and progression of epithelial-mesenchymal transition (EMT). However their differential expression in non-small cell lung cancer (NSCLC) clinical samples and exact regulatory roles in cancer stem-like cells (CSCs) remain unknown.

Methods

In vitro and in vivo experiments were employed to investigate the molecular mechanism. Using CSCs, mouse models, and clinical tissues, we obtained a general picture of the relatively higher level of PRRX1A compared to PRRX1B, and PRRX1A thus promoting EMT and maintaining stemness of CSCs.

Results

PRRX1A but not PRRX1B was upregulated in lung cancer tissues and was positively correlated with TGF-β expression. In CSCs, overexpressed PRRX1A promoted malignant behaviors via transcriptional activation of TGF-β depending on TGF-β/TGF-βR signaling pathway. PRRX1A knockdown decreased self-renewal capacity accompanied by a decrease in stemness factor expression independent of the TGF-β/TGF-βR signaling pathway. Furthermore, PRRX1A was found to tightly bind to and stabilize SOX2. PRRX1A promoted sphere formation not only by enhancing stemness via stabilizing SOX2 but also by promoting cell proliferation.

Conclusions

PRRX1A, but not PRRX1B, was demonstrated to have important roles in the regulation of the stemness and metastatic potential of lung cancer, which suggests the potential application of PRRX1A in cancer treatment.

RAC1 Involves in the Radioresistance by Mediating Epithelial-Mesenchymal Transition in Lung Cancer

Radiation therapy is a common and acceptable approach for lung cancer. Although the benefit of ionizing radiation (IR) is well-established, cancer cells can still survive via pro-survival and metastasis signaling pathways. Ras related C3 botulinum toxin substrate1 (RAC1), a member of Rho family GTPases, plays important roles in cell migration and survival. In the present study, we investigated the effects of RAC1 on the survival of lung cancer cells treated with irradiation. The results showed RAC1 is overexpressed in lung cancer cells and promoted cell proliferation and survival. Furthermore, IR induced RAC1 expression and activity via the activation of PI3K/AKT signaling pathway, and then enhancing cell proliferation, survival, migration and metastasis and increasing levels of epithelial-to-mesenchymal transition (EMT) markers, which facilitated the cell survival and invasive phenotypes. In addition, overexpression of RAC1 attenuated the efficacy of irradiation, while inhibition of RAC1 enhanced sensitivity of irradiation in xenograft tumors in vivo. Collectively, we further found that RAC1 enhanced radioresistance by promoting EMT via targeting the PAK1-LIMK1-Cofilins signaling in lung cancer. Our finding provides the evidences to explore RAC1 as a therapeutic target for radioresistant lung cancer cells.

Pre-metastatic niche triggers SDF-1/CXCR4 axis and promotes organ colonisation by hepatocellular circulating tumour cells via downregulation of Prrx1

Background

Circulating tumour cells (CTCs), especially mesenchymal CTCs, are important determinants of metastasis, which leads to most recurrence and mortality in hepatocellular carcinoma (HCC). However, little is known about the underlying mechanisms of CTC colonisation in pre-metastatic niches.

Methods

Detection and classification of CTCs in patients were performed using the CanPatrol™ system. A lentiviral vector expressing Prrx1-targeting shRNA was constructed to generate a stable HCC cell line with low expression of Prrx1. The effect of Prrx1 knockdown on stemness, migration, and drug resistance of the cell line was assessed, including involvement of SDF-1/CXCR4 signalling. Promising clinical applications of an inhibitor of STAT3 tyrosine phosphorylation, C188–9, and specific blockade with CXCR4 antibody were explored.

Results

The number of mesenchymal CTCs in blood was closely associated with tumour recurrence or metastasis. Pre-metastatic niche-derived SDF-1 could downregulate Prrx1, which induced the stemness, drug resistance, and increased expression of CXCR4 in HCC cells through the STAT3 pathway in vitro. In vivo, mice bearing tumours of Prrx1 low-expressing cells had significantly shorter survival. In xenograft tumours and clinical samples, loss of Prrx1 was negatively correlated with increased expression of CXCR4 in lung metastatic sites compared with that in the primary foci.

Conclusions

These findings demonstrate that decreased expression of Prrx1 stimulates SDF-1/CXCR4 signalling and contributes to organ colonisation with blood CTCs in HCC. STAT3 inhibition and specific blockade of CXCR4 have clinical potential as therapeutics for eliminating organ metastasis in advanced HCC.

EMT and Stemness-Key Players in Pancreatic Cancer Stem Cells

Metastasis and tumor progression are the major cause of death in patients suffering from pancreatic ductal adenocarcinoma. Tumor growth and especially dissemination are typically associated with activation of an epithelial-to-mesenchymal transition (EMT) program. This phenotypic transition from an epithelial to a mesenchymal state promotes migration and survival both during development and in cancer progression. When re-activated in pathological contexts such as cancer, this type of developmental process confers additional stemness properties to specific subsets of cells. Cancer stem cells (CSCs) are a subpopulation of cancer cells with stem-like features that are responsible for the propagation of the tumor as well as therapy resistance and cancer relapse, but also for circulating tumor cell release and metastasis. In support of this concept, EMT transcription factors generate cells with stem cell properties and mediate chemoresistance. However, their role in pancreatic ductal adenocarcinoma metastasis remains controversial. As such, a better characterization of CSC populations will be crucial in future development of therapies targeting these cells. In this review, we will discuss the latest updates on the mechanisms common to pancreas development and CSC-mediated tumor progression.