Gene Summary

Gene:PROX1; prospero homeobox 1
Summary:The protein encoded by this gene is a member of the homeobox transcription factor family. Members of this family contain a homeobox domain that consists of a 60-amino acid helix-turn-helix structure that binds DNA and RNA. The protein encoded by this gene is conserved across vertebrates and may play an essential role during development. Altered levels of this protein have been reported in cancers of different organs, such as colon, brain, blood, breast, pancreas, liver and esophagus. Alternative splicing results in multiple transcript variants. [provided by RefSeq, Jul 2012]
Databases:OMIM, HGNC, Ensembl, GeneCard, Gene
Protein:prospero homeobox protein 1
Source:NCBIAccessed: 01 September, 2019


What does this gene/protein do?
Show (67)

Cancer Overview

Research Indicators

Publications Per Year (1994-2019)
Graph generated 01 September 2019 using data from PubMed using criteria.

Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

  • Liver Cancer
  • Squamous Cell Carcinoma
  • Tumor Suppressor Proteins
  • Biomarkers, Tumor
  • Chromosome 1
  • Cell Line
  • Vascular Endothelial Growth Factor D
  • Angiogenesis
  • Transcription
  • Vascular Endothelial Growth Factor Receptor-3
  • Cell Movement
  • Immunohistochemistry
  • Phenotype
  • Lymphangiogenesis
  • Lymphatic Metastasis
  • Neoplasm Invasiveness
  • Cancer Gene Expression Regulation
  • HEK293 Cells
  • Hepatocellular Carcinoma
  • Messenger RNA
  • Cell Differentiation
  • Cell Proliferation
  • Western Blotting
  • Disease Progression
  • Risk Factors
  • Endothelial Cells
  • Oligonucleotide Array Sequence Analysis
  • DNA Methylation
  • Neoplasm Metastasis
  • Breast Cancer
  • Mutation
  • Staging
  • Vesicular Transport Proteins
  • Gene Expression Profiling
  • Carcinoma
  • Pancreatic Cancer
  • Homeodomain Proteins
  • Gene Knockdown Techniques
  • Colorectal Cancer
  • raf Kinases
  • Base Sequence
Tag cloud generated 01 September, 2019 using data from PubMed, MeSH and CancerIndex

Specific Cancers (4)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: PROX1 (cancer-related)

Rudzińska M, Grzanka M, Stachurska A, et al.
Molecular Signature of Prospero Homeobox 1 (PROX1) in Follicular Thyroid Carcinoma Cells.
Int J Mol Sci. 2019; 20(9) [PubMed] Free Access to Full Article Related Publications
The prospero homeobox 1 (PROX1) transcription factor is a product of one of the lymphangiogenesis master genes. It has also been suggested to play a role in carcinogenesis, although its precise role in tumour development and metastasis remains unclear. The aim of this study was to gain more knowledge on the PROX1 function in thyroid tumorigenesis. Follicular thyroid cancer-derived cells-CGTH-W-1-were transfected with PROX1-siRNA (small interfering RNA) and their proliferation, cell cycle, apoptosis and motility were then analysed. The transcriptional signature of

Ueta K, Otowa Y, Kakeji Y, Hirashima M
PROX1 Is Associated with Cancer Progression and Prognosis in Gastric Cancer.
Anticancer Res. 2018; 38(11):6139-6145 [PubMed] Related Publications
BACKGROUND: It was recently reported that expression of prospero homeobox protein-1 (PROX1) is correlated with the prognosis of esophageal cancer and colorectal cancer. However, its correlation with gastric cancer is unclear.
MATERIALS AND METHODS: Our study analyzed the effect of PROX1 knockdown on the migration, invasion and proliferation of the MKN45 human gastric cancer cell line. The correlation between PROX1 expression levels and clinicopathological factors were also analyzed in tumor samples from 99 patients with gastric cancer.
RESULTS: Migration, invasion and proliferation were significantly reduced in MKN45 cells with PROX1 knockdown. PROX1 expression was detected in gastric cancer tissues at various levels. PROX1 expression levels were positively correlated with cancer stage, N factor, lymphatic vascular invasion, and vascular invasion in patients with gastric cancer. Analysis of overall and recurrence-free survival indicated that high PROX1 expression was significantly correlated with poor prognosis.
CONCLUSION: PROX1 can be an indicator of poor prognosis and a molecular target for gastric cancer treatment.

Shen Y, Xia E, Bhandari A, et al.
LncRNA PROX1-AS1 promotes proliferation, invasion, and migration in papillary thyroid carcinoma.
Biosci Rep. 2018; 38(5) [PubMed] Free Access to Full Article Related Publications
Evidence has been provided that long noncoding RNAs (LncRNAs) play major roles in affecting essential physiological processes, and many of which seem to have functional roles in tumorigenesis and progression. However, the intrinsic molecular mechanism of LncRNAs acting on papillary thyroid carcinoma is not well understood. In the present study, we found that PROX1-AS1 levels were obviously increased in thyroid cancer cells compared with the normal thyroid epithelial cells. Knockdown of PROX1-AS1 gene expression by siRNA could inhibit cell proliferation. Subsequently, we also observed that silencing PROX1-AS1 might inhibit invasion and migration of thyroid cancer cell lines via modulating the expression of epithelial-mesenchymal transition related proteins. In conclusion, our study indicated that LncRNA PROX1-AS1 could promote papillary thyroid carcinoma development and might serve as a potential targeting marker for papillary thyroid carcinoma.

Kim YJ, Yoo JE, Jeon Y, et al.
Suppression of PROX1-mediated TERT expression in hepatitis B viral hepatocellular carcinoma.
Int J Cancer. 2018; 143(12):3155-3168 [PubMed] Related Publications
Somatic mutations in the telomerase reverse transcriptase (TERT) promoter are related to telomerase activation and frequently occur at two hot spots located at -124 and -146 bp relative to the start codon in various cancers. Here, we investigated the occurrence and implications of genetic alterations in the TERT promoter in hepatitis B viral hepatocellular carcinoma (B viral HCC). TERT promoter mutations, especially -124C>T, clearly enhanced transcriptional activity in HCC cell lines. In contrast, TERT mRNA expression was lower in B viral HCC patients with TERT promoter mutations than in those without. We identified prospero homeobox protein 1 (PROX1) as a novel transcriptional activator of TERT; this protein was shown to have particularly strong binding affinity for the mutant TERT promoter. However, stable expression of the hepatitis B virus X (HBx) protein inhibited PROX1-mediated TERT expression in vitro. Our data suggest that TERT promoter mutations can enhance the promoter activity in HCC cell lines expressing PROX1 but are not the predominant mechanism of TERT upregulation in B viral HCC patients, based on the inhibition of PROX1-dependent transcriptional activation by HBx.

Agnihotri NS, Astekar M
The role of novel prognostic markers PROX1 and FOXC2 in carcinogenesis of oral squamous cell carcinoma.
J Exp Ther Oncol. 2018; 12(3):171-184 [PubMed] Related Publications
objective: Oral squamous cell carcinoma is the most common malignant tumor of the head and neck regions and accounts for more than 90% of cancers in the oral cavity. The angiogenesis, lymphangiogenesis and epithelial mesenchymal transition are known to be pivotal for tumor progression and metastasis. In the last decade, much data has been generated concerning the molecular mechanisms of angiogenesis, lymphangiogenesis and its significance in pathological conditions. The main angiogenic and lymphangiogenic factors have been identified as vascular endothelial growth factor A (VEGF-A), vascular endothelial growth factor receptor 2 (VEGFR-2), forkhead box (FOX) C2 while vascular endothelial growth factor C/D (VEGF-C/D), vascular endothelial growth factor receptor 3 (VEGFR-3), Prospero homeobox 1 (PROX1), LYVE-1, podoplanin, Tie/Angioprotein (Ang) 2 and EphrinB2 respectively. PROX1 is a mammalian homologue of Drosophilia homeobox protein, prospero and important for the embryonic development of many mammalian tissues. It has been suggested that it plays various tissue dependent functional roles, which reflects both oncogenic potential and a tumor suppressive role. The exact role in OSCC remains controversial. FOXC2 is a transcription factor belongs to large family of protein, forkhead box. It has been shown to be involved in cancer angiogenesis, proliferation and metastasis through its induction of epithelial-to-mesenchymal transition while its significance in OSCC remains unknown. Based on these data, this article reviews the role of novel prognostic factors PROX1 and FOXC2 in carcinogenesis of OSCC so that they might be considered as an attractive therapeutic target for both tumor associated blood vessels, lymphatic vessels and tumor cells.

Fristiohady A, Milovanovic D, Krieger S, et al.
12(S)-HETE induces lymph endothelial cell retraction in vitro by upregulation of SOX18.
Int J Oncol. 2018; 53(1):307-316 [PubMed] Related Publications
Metastasising breast cancer cells communicate with adjacent lymph endothelia, intravasate and disseminate through lymphatic routes, colonise lymph nodes and finally metastasize to distant organs. Thus, understanding and blocking intravasation may attenuate the metastatic cascade at an early step. As a trigger factor, which causes the retraction of lymph endothelial cells (LECs) and opens entry ports for tumour cell intravasation, MDA-MB231 breast cancer cells secrete the pro-metastatic arachidonic acid metabolite, 12S-hydroxy-5Z,8Z,10E,14Z-eicosatetraenoic acid [12(S)-HETE]. In the current study, treatment of LECs with 12(S)-HETE upregulated the expression of the transcription factors SRY-related HMG-box 18 (SOX18) and prospero homeobox protein 1 (PROX1), which determine endothelial development. Thus, whether they have a role in LEC retraction was determined using a validated intravasation assay, small interfering RNA mediated knockdown of gene expression, and mRNA and protein expression analyses. Specific inhibition of SOX18 or PROX1 significantly attenuated in vitro intravasation of MDA-MB231 spheroids through the LEC barrier and 12(S)-HETE-triggered signals were transduced by the high and low affinity receptors, 12(S)-HETE receptor and leukotriene B4 receptor 2. In addition, the current findings indicate that there is crosstalk between SOX18 and nuclear factor κ-light-chain-enhancer of activated B cells, which was demonstrated to contribute to MDA-MB231/lymph endothelial intravasation. The present data demonstrate that the endothelial-specific and lymph endothelial-specific transcription factors SOX18 and PROX1 contribute to LEC retraction.

Nair RM, Balla MM, Khan I, et al.
In vitro characterization of CD133
BMC Cancer. 2017; 17(1):779 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Retinoblastoma (Rb), the most common childhood intraocular malignant tumor, is reported to have cancer stem cells (CSCs) similar to other tumors. Our previous investigation in primary tumors identified the small sized cells with low CD133 (Prominin-1) and high CD44 (Hyaluronic acid receptor) expression to be putative Rb CSCs using flow cytometry (FSC
METHODS: The cultured Rb Y79 cells were evaluated for surface markers by flow cytometry and CD133 sorted cells (CD133
RESULTS: Rb Y79 cell line shared the profile (CD133, CD90, CXCR4 and ABCB1) of primary tumors except for CD44 expression. The CD133
CONCLUSIONS: This study validates the observation from our earlier primary tumor study that CSC properties in Rb Y79 cell line are endowed within the CD133

Morton LM, Sampson JN, Armstrong GT, et al.
Genome-Wide Association Study to Identify Susceptibility Loci That Modify Radiation-Related Risk for Breast Cancer After Childhood Cancer.
J Natl Cancer Inst. 2017; 109(11) [PubMed] Free Access to Full Article Related Publications
Background: Childhood cancer survivors treated with chest-directed radiotherapy have substantially elevated risk for developing breast cancer. Although genetic susceptibility to breast cancer in the general population is well studied, large-scale evaluation of breast cancer susceptibility after chest-directed radiotherapy for childhood cancer is lacking.
Methods: We conducted a genome-wide association study of breast cancer in female survivors of childhood cancer, pooling two cohorts with detailed treatment data and systematic, long-term follow-up: the Childhood Cancer Survivor Study and St. Jude Lifetime Cohort. The study population comprised 207 survivors who developed breast cancer and 2774 who had not developed any subsequent neoplasm as of last follow-up. Genotyping and subsequent imputation yielded 16 958 466 high-quality variants for analysis. We tested associations in the overall population and in subgroups stratified by receipt of lower than 10 and 10 or higher gray breast radiation exposure. We report P values and pooled per-allele risk estimates from Cox proportional hazards regression models. All statistical tests were two-sided.
Results: Among survivors who received 10 or higher gray breast radiation exposure, a locus on 1q41 was associated with subsequent breast cancer risk (rs4342822, nearest gene PROX1 , risk allele frequency in control subjects [RAF controls ] = 0.46, hazard ratio = 1.92, 95% confidence interval = 1.49 to 2.44, P = 7.09 × 10 -9 ). Two rare variants also showed potentially promising associations (breast radiation ≥10 gray: rs74949440, 11q23, TAGLN , RAF controls = 0.02, P = 5.84 × 10 -8 ; <10 gray: rs17020562, 1q32.3, RPS6KC1 , RAF controls = 0.0005, P = 6.68 × 10 -8 ). Associations were restricted to these dose subgroups, with consistent findings in the two survivor cohorts.
Conclusions: Our study provides strong evidence that germline genetics outside high-risk syndromes could modify the effect of radiation exposure on breast cancer risk after childhood cancer.

Volk-Draper LD, Hall KL, Wilber AC, Ran S
Lymphatic endothelial progenitors originate from plastic myeloid cells activated by toll-like receptor-4.
PLoS One. 2017; 12(6):e0179257 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Myeloid-derived lymphatic endothelial cells (M-LECP) are induced by inflammation and play an important role in adult lymphangiogenesis. However, the mechanisms driving M-LECP differentiation are currently unclear. We previously showed that activation of Toll-like receptor-4 (TLR4) induces myeloid-lymphatic transition (MLT) of immortalized mouse myeloid cells. Here the goals were to assess the potential of different TLR4 ligands to induce pro-lymphatic reprogramming in human and mouse primary myeloid cells and to identify transcriptional changes regulating this process.
METHODOLOGY/PRINCIPAL FINDINGS: Human and mouse myeloid cells were reprogrammed to the lymphatic phenotype by TLR4 ligands including lipopolysaccharide (LPS), recombinant high mobility group box 1 protein (HMGB1), and paclitaxel. TLR4 induced similar MLT in cells from mice of different strains and immune status. Commonly induced genes were detected by transcriptional profiling in human and mouse myeloid cells from either immunocompetent or immunodeficient mice. Shared trends included: (1) novel expression of lymphatic-specific markers vascular endothelial growth factor receptor-3 (VEGFR-3), lymphatic vessel endothelial hyaluronan receptor-1 (LYVE-1) and podoplanin (PDPN) largely absent prior to induction; (2) lack of notable changes in blood vessel-specific markers; (3) transient expression of VEGFR-3, but sustained increase of vascular endothelial growth factor-C (VEGF-C) and a variety of inflammatory cytokines; (4) dependency of VEGFR-3 upregulation and other LEC genes on NF-κB; and (5) novel expression of lymphatic-specific (e.g., PROX1) and stem/progenitor (e.g., E2F1) transcription factors known for their roles in adult and embryonic vascular formation. M-LECP generated by TLR4 ligands in vitro were functional in vivo as demonstrated by significantly increased lymphatic vessel density and lymphatic metastasis detected in orthotopic breast cancer models.
CONCLUSIONS/SIGNIFICANCE: We established a novel TLR4-dependent protocol for in vitro production of functionally competent M-LECP from primary human or mouse myeloid cells and identified many potential regulators of this process. This information can be further exploited for research and therapeutic purposes.

Bhat S, Kabekkodu SP, Varghese VK, et al.
Aberrant gene-specific DNA methylation signature analysis in cervical cancer.
Tumour Biol. 2017; 39(3):1010428317694573 [PubMed] Related Publications
Multicomponent molecular modifications such as DNA methylation may offer sensitive and specific cervical intraepithelial neoplasia and cervical cancer biomarkers. In this study, we tested cervical tissues at various stages of tumor progression for 5-methylcytosine and 5-hydroxymethylcytosine levels and also DNA promoter methylation profile of a panel of genes for its diagnostic potential. In total, 5-methylcytosine, 5-hydroxymethylcytosine, and promoter methylation of 33 genes were evaluated by reversed-phase high-performance liquid chromatography, enzyme-linked immunosorbent assay based technique, and bisulfate-based next generation sequencing. The 5-methylcytosine and 5-hydroxymethylcytosine contents were significantly reduced in squamous cell carcinoma and receiver operating characteristic curve analysis showed a significant difference in (1) 5-methylcytosine between normal and squamous cell carcinoma tissues (area under the curve = 0.946) and (2) 5-hydroxymethylcytosine levels among normal, squamous intraepithelial lesions and squamous cell carcinoma. Analyses of our next generation sequencing results and data from five independent published studies consisting of 191 normal, 10 low-grade squamous intraepithelial lesions, 21 high-grade squamous intraepithelial lesions, and 335 malignant tissues identified a panel of nine genes ( ARHGAP6, DAPK1, HAND2, NKX2-2, NNAT, PCDH10, PROX1, PITX2, and RAB6C) which could effectively discriminate among the various groups with sensitivity and specificity of 80%-100% (p < 0.05). Furthermore, 12 gene promoters (ARHGAP6, HAND2, LHX9, HEY2, NKX2-2, PCDH10, PITX2, PROX1, TBX3, IKBKG, RAB6C, and DAPK1) were also methylated in one or more of the cervical cancer cell lines tested. The global and gene-specific methylation of the panel of genes identified in our study may serve as useful biomarkers for the early detection and clinical management of cervical cancer.

Xu X, Wan X, Wei X
PROX1 promotes human glioblastoma cell proliferation and invasion via activation of the nuclear factor-κB signaling pathway.
Mol Med Rep. 2017; 15(2):963-968 [PubMed] Related Publications
Prospero homeobox protein 1 (PROX1) is highly expressed in high-grade malignant astrocytic gliomas. However, the role of PROX1 in the pathogenesis of glioblastoma multiforme (GBM) remains unclear. The present study overexpressed PROX1 in human GBM cell lines and examined its effects on cell growth, tumorigenesis, and invasiveness. In addition, the involvement of the nuclear factor‑κB (NF‑κB) signaling pathway in the action of PROX1 was examined. It was identified that overexpression of PROX1 significantly increased the proliferation and colony formation of glioblastoma cells, compared with empty vector‑transfected controls. Furthermore, ectopic expression of PROX1 promoted the growth of GBM xenograft tumors. Western blot analysis revealed that PROX1 overexpression induced nuclear accumulation of NF‑κB p65 and upregulated the expression levels of the NF‑κB responsive genes cyclin D1 and matrix metallopeptidase 9. An NF‑κB reporter assay demonstrated that PROX1‑overexpressing glioblastoma cells had significantly greater NF‑κB‑dependent reporter activities compared with empty vector‑transfected controls. Transfection of a dominant inhibitor of κBα mutant into PROX1‑overexpressing cells significantly impaired their proliferation and invasion capacities, which was accompanied by reduced levels of nuclear NF‑κB p65. Collectively, these data indicated that PROX1 serves an oncogenic role in GBM and promotes cell proliferation and invasiveness potentially via activation of the NF‑κB signaling pathway. Therefore, PROX1 may represent a potential target for the treatment of GBM.

Roodakker KR, Elsir T, Edqvist PD, et al.
PROX1 is a novel pathway-specific prognostic biomarker for high-grade astrocytomas; results from independent glioblastoma cohorts stratified by age and IDH mutation status.
Oncotarget. 2016; 7(45):72431-72442 [PubMed] Free Access to Full Article Related Publications
PROX1 is a transcription factor with an essential role in embryonic development and determination of cell fate. In addition, PROX1 has been ascribed suppressive as well as oncogenic roles in several human cancers, including brain tumors. In this study we explored the correlation between PROX1 expression and patient survival in high-grade astrocytomas. For this purpose, we analyzed protein expression in tissue microarrays of tumor samples stratified by patient age and IDH mutation status. We initially screened 86 unselected high-grade astrocytomas, followed by 174 IDH1-R132H1 immunonegative glioblastomas derived from patients aged 60 years and older enrolled in the Nordic phase III trial of elderly patients with newly diagnosed glioblastoma. Representing the younger population of glioblastomas, we studied 80 IDH-wildtype glioblastomas from patients aged 18-60 years. There was no correlation between PROX1 protein and survival for patients with primary glioblastomas included in these cohorts. In contrast, high expression of PROX1 protein predicted shorter survival in the group of patients with IDH-mutant anaplastic astrocytomas and secondary glioblastomas. The prognostic impact of PROX1 in IDH-mutant 1p19q non-codeleted high-grade astrocytomas, as well as the negative findings in primary glioblastomas, was corroborated by gene expression data extracted from the Cancer Genome Atlas. We conclude that PROX1 is a new prognostic biomarker for 1p19q non-codeleted high-grade astrocytomas that have progressed from pre-existing low-grade tumors and harbor IDH mutations.

Wang B, Huang J, Zhou J, et al.
DAB2IP regulates EMT and metastasis of prostate cancer through targeting PROX1 transcription and destabilizing HIF1α protein.
Cell Signal. 2016; 28(11):1623-30 [PubMed] Related Publications
Prospero-related homeobox 1 (PROX1) is an essential regulator in lymphangiogenesis and has been implicated in both oncogenic and tumor-suppressive functions in many types of human cancers. However, the role of PROX1 in prostate cancer (PCa) remains poorly understood. In this study, based on different PCa cell lines and knockout mice, we showed that PROX1 could be suppressed by DAB2IP, a novel member of the Ras GTPase-activating protein family and a critical player in control of epithelial-mesenchymal transition (EMT) and PCa metastasis. Mechanistically, PROX1 overexpression in DAB2IP-deficient PCa cells could enhance the accumulation of HIF1α protein by inhibiting ubiquitin pathway and then consequently induce an EMT response, which is characterized by repression of E-cadherin, up-regulation of vimentin and matrix metallopeptidases (MMPs) and enhancement of cell migration. Together, our data provides a new insight into mechanism that DAB2IP regulates EMT and PCa metastasis, especially points out the potential roles of its downstream PROX1/HIF1α signaling in a unique non-skeletal metastasis of PCa.

Nguyen-Vu T, Wang J, Mesmar F, et al.
Estrogen receptor beta reduces colon cancer metastasis through a novel miR-205 - PROX1 mechanism.
Oncotarget. 2016; 7(27):42159-42171 [PubMed] Free Access to Full Article Related Publications
Colon cancer is a common cause of cancer death in the Western world. Accumulating evidence supports a protective role of estrogen via estrogen receptor beta (ERβ) but the mechanism of action is not known. Here, we elucidate a molecular mechanism whereby ERβ represses the oncogenic prospero homebox 1 (PROX1) through the upregulation of miR-205. We show that PROX1 is a potential target of miR-205 and that in clinical specimens from The Cancer Genome Atlas data, ERβ and miR-205 are decreased in colorectal cancer tissue compared to non-tumorous colon, while PROX1 levels are increased. Through mechanistic studies in multiple colorectal cancer cell lines, we show that ERβ upregulates miR-205, and that miR-205 targets and represses PROX1 through direct interaction with its 3'UTR. Through the generation of intestine-specific ERβ knockout mice, we establish that this pathway is correspondingly regulated in normal intestinal epithelial cells in vivo. Functionally, we demonstrate that miR-205 decreases cell proliferation and decreases migratory and invasive potential of colon cancer cells, leading to a reduction of micrometastasis in vivo. In conclusion, ERβ in both normal and cancerous colon epithelial cells upregulates miRNA-205, which subsequently reduces PROX1 through direct interaction with its 3'UTR. This results in reduced proliferative and metastatic potential of the cells. Our study proposes a novel pathway that may be exploited using ERβ-selective agonists and/or miR-205-replacement therapy in order to improve preventive and therapeutic approaches against colon cancer.

Yoshimatsu Y, Miyazaki H, Watabe T
Roles of signaling and transcriptional networks in pathological lymphangiogenesis.
Adv Drug Deliv Rev. 2016; 99(Pt B):161-171 [PubMed] Related Publications
Lymphangiogenesis, the generation of new lymphatic vessels, plays important roles in cancer metastasis. Outstanding progress during the past decade has dramatically increased the novel knowledge and insights of the mechanisms underlying the generation of new lymphatic vessels, the roles of transcription factors and lymphangiogenic growth factors during physiological development and pathological processes such as cancer and inflammation. Furthermore, an understanding of the molecular consequences during tumor lymphangiogenesis has provided chances to develop better diagnostic and therapeutic approaches that aim to limit the progression of cancer. In this article, we will explain the current knowledge of how lymphatic function is altered in various pathological conditions including cancer progression.

Ishii J, Yazawa T, Chiba T, et al.
PROX1 Promotes Secretory Granule Formation in Medullary Thyroid Cancer Cells.
Endocrinology. 2016; 157(3):1289-98 [PubMed] Related Publications
Mechanisms of endocrine secretory granule (SG) formation in thyroid C cells and medullary thyroid cancer (MTC) cells have not been fully elucidated. Here we directly demonstrated that PROX1, a developmental homeobox gene, is transcriptionally involved in SG formation in MTC, which is derived from C cells. Analyses using gene expression databases on web sites revealed that, among thyroid cancer cells, MTC cells specifically and highly express PROX1 as well as several SG-forming molecule genes. Immunohistochemical analyses showed that in vivo MTC and C cells expressed PROX1, although follicular thyroid cancer and papillary thyroid cancer cells, normal follicular cells did not. Knockdown of PROX1 in an MTC cells reduced SGs detected by electron microscopy, and decreased expression of SG-related genes (chromogranin A, chromogranin B, secretogranin II, secretogranin III, synaptophysin, and carboxypeptidase E). Conversely, the introduction of a PROX1 transgene into a papillary thyroid cancer and anaplastic thyroid cancer cells induced the expression of SG-related genes. Reporter assays using the promoter sequence of chromogranin A showed that PROX1 activates the chromogranin A gene in addition to the known regulatory mechanisms, which are mediated via the cAMP response element binding protein and the repressor element 1-silencing transcription factor. Furthermore, chromatin immunoprecipitation-PCR assays demonstrated that PROX1 binds to the transcriptional regulatory element of the chromogranin A gene. In conclusion, PROX1 is an important regulator of endocrine SG formation in MTC cells.

Park KJ, Cho SB, Park YL, et al.
Prospero homeobox 1 mediates the progression of gastric cancer by inducing tumor cell proliferation and lymphangiogenesis.
Gastric Cancer. 2017; 20(1):104-115 [PubMed] Related Publications
BACKGROUND: Prospero homeobox 1 (PROX1) functions as a tumor suppressor gene or an oncogene in various cancer types. However, the distinct function of PROX1 in gastric cancer is unclear. We determined whether PROX1 affected the oncogenic behavior of gastric cancer cells and investigated its prognostic value in patients with gastric cancer.
METHODS: A small interfering RNA against PROX1 was used to silence PROX1 expression in gastric cancer cell lines AGS and SNU638. Expression of PROX1 in gastric cancer tissues was investigated by performing immunohistochemistry. Apoptosis, proliferation, angiogenesis, and lymphangiogenesis were determined by performing the TUNEL assay and immunohistochemical staining for Ki-67, CD34, and D2-40.
RESULTS: PROX1 knockdown induced apoptosis by activating cleaved caspase-3, caspase-7, caspase-9, and poly(ADP-ribose) polymerase, and by decreasing the expression of anti-apoptotic proteins Bcl-2 and Bcl-xL. PROX1 knockdown also suppressed tumor cell proliferation. In addition, PROX1 knockdown decreased lymphatic endothelial cell invasion and tube formation and the expression of vascular endothelial growth factor (VEGF)-C and -D and cyclooxygenase (COX)-2. However, PROX1 knockdown only decreased umbilical vein endothelial cell invasion, not tube formation. The mean Ki-67 labeling index and lymphatic vessel density value of PROX1-positive tumors were significantly higher than those of PROX1-negative tumors. However, no significant difference was observed between PROX1 expression and apoptotic index or microvessel density. PROX1 expression was significantly associated with age, cell differentiation, lymph node metastasis, cancer stage, and poor survival.
CONCLUSIONS: These results indicate that PROX1 mediates the progression of gastric cancer by inducing tumor cell proliferation and lymphangiogenesis.

Choi D, Ramu S, Park E, et al.
Aberrant Activation of Notch Signaling Inhibits PROX1 Activity to Enhance the Malignant Behavior of Thyroid Cancer Cells.
Cancer Res. 2016; 76(3):582-93 [PubMed] Free Access to Full Article Related Publications
Papillary thyroid cancer (PTC) is one of the most common endocrine malignancies associated with significant morbidity and mortality. Although multiple studies have contributed to a better understanding of the genetic alterations underlying this frequently arising disease, the downstream molecular effectors that impact PTC pathogenesis remain to be further defined. Here, we report that the regulator of cell fate specification, PROX1, becomes inactivated in PTC through mRNA downregulation and cytoplasmic mislocalization. Expression studies in clinical specimens revealed that aberrantly activated NOTCH signaling promoted PROX1 downregulation and that cytoplasmic mislocalization significantly altered PROX1 protein stability. Importantly, restoration of PROX1 activity in thyroid carcinoma cells revealed that PROX1 not only enhanced Wnt/β-catenin signaling but also regulated several genes known to be associated with PTC, including thyroid cancer protein (TC)-1, SERPINA1, and FABP4. Furthermore, PROX1 reexpression suppressed the malignant phenotypes of thyroid carcinoma cells, such as proliferation, motility, adhesion, invasion, anchorage-independent growth, and polyploidy. Moreover, animal xenograft studies demonstrated that restoration of PROX1 severely impeded tumor formation and suppressed the invasiveness and the nuclear/cytoplasmic ratio of PTC cells. Taken together, our findings demonstrate that NOTCH-induced PROX1 inactivation significantly promotes the malignant behavior of thyroid carcinoma and suggest that PROX1 reactivation may represent a potential therapeutic strategy to attenuate disease progression.

Karol SE, Mattano LA, Yang W, et al.
Genetic risk factors for the development of osteonecrosis in children under age 10 treated for acute lymphoblastic leukemia.
Blood. 2016; 127(5):558-64 [PubMed] Free Access to Full Article Related Publications
Osteonecrosis is a dose-limiting toxicity in the treatment of pediatric acute lymphoblastic leukemia (ALL). Prior studies on the genetics of osteonecrosis have focused on patients ≥10 years of age, leaving the genetic risk factors for the larger group of children <10 years incompletely understood. Here, we perform the first evaluation of genetic risk factors for osteonecrosis in children <10 years. The discovery cohort comprised 82 cases of osteonecrosis and 287 controls treated on Children's Oncology Group (COG) standard-risk ALL protocol AALL0331 (NCT00103285,, with results tested for replication in 817 children <10 years treated on COG protocol AALL0232 (NCT00075725, The top replicated single nucleotide polymorphisms (SNPs) were near bone morphogenic protein 7 [BMP7: rs75161997, P = 5.34 × 10(-8) (odds ratio [OR] 15.0) and P = .0498 (OR 8.44) in the discovery and replication cohorts, respectively] and PROX1-antisense RNA1 (PROX1-AS1: rs1891059, P = 2.28 × 10(-7) [OR 6.48] and P = .0077 [OR 3.78] for the discovery and replication cohorts, respectively). The top replicated nonsynonymous SNP, rs34144324, was in a glutamate receptor gene (GRID2, P = 8.65 × 10(-6) [OR 3.46] and P = .0136 [OR 10.8] in the discovery and replication cohorts, respectively). In a meta-analysis, the BMP7 and PROX1-AS1 variants (rs75161997 and rs1891059, respectively) met the significance threshold of <5 × 10(-8). Top replicated SNPs were enriched in enhancers active in mesenchymal stem cells, and analysis of annotated genes demonstrated enrichment in glutamate receptor and adipogenesis pathways. These data may provide new insights into the pathophysiology of osteonecrosis.

Yu EJ, Kim SH, Kim HJ, et al.
Positive regulation of β-catenin-PROX1 signaling axis by DBC1 in colon cancer progression.
Oncogene. 2016; 35(26):3410-8 [PubMed] Free Access to Full Article Related Publications
Aberrant activation of Wnt/β-catenin pathway contributes to colorectal cancer (CRC) progression. However, little is known about regulatory mechanisms of the β-catenin activity in cancer progression. Here we investigated the role of DBC1, which was recently reported as a negative regulator of SIRT1 and a transcriptional coactivator, in the regulation of Wnt/β-catenin signaling. We identified the genome-wide targets of DBC1 and found that loss of DBC1 inhibits the expression of β-catenin target genes including PROX1, a transcription factor linked to CRC progression. Mechanistically, DBC1 stabilizes LEF1-β-catenin interaction by inhibiting SIRT1-mediated β-catenin deacetylation, thereby enhancing LEF1-β-catenin complex formation and long-range chromatin looping at the PROX1 locus. Furthermore, DBC1 is also required for the transcriptional activity of PROX1, suggesting that DBC1 has a dual function in regulating β-catenin-PROX1 signaling axis: as a coactivator for both β-catenin and PROX1. Importantly, loss of DBC1 inhibited growth and tumorigenic potential of colon cancer cells, and DBC1 expression correlated with shorter relapse-free survival in patients with advanced CRC. Our results firmly establish DBC1 as a critical positive regulator of β-catenin-PROX1 signaling axis and a key factor in β-catenin-PROX1-mediated CRC progression.

Yokobori T, Bao P, Fukuchi M, et al.
Nuclear PROX1 is Associated with Hypoxia-Inducible Factor 1α Expression and Cancer Progression in Esophageal Squamous Cell Carcinoma.
Ann Surg Oncol. 2015; 22 Suppl 3:S1566-73 [PubMed] Related Publications
BACKGROUND: Transcription factor prospero homeobox 1 (PROX1) has been identified as a master regulator of lymphangiogenesis associated with metastasis. Although PROX1 expression has been investigated in several cancers, its clinical significance remains controversial and needs further validation. In this study, we investigated the clinical and functional significance of PROX1 and PROX1 regulator hypoxia-inducible factor 1α (HIF1α) in esophageal squamous cell carcinoma (ESCC).
METHODS: A total of 117 samples from ESCC patients were analyzed for PROX1, HIF1α, and E-cadherin expression by immunohistochemistry; correlation with clinicopathological characteristics was determined. PROX1 function was evaluated in PROX1 small interfering RNA (siRNA)-transfected human ESCC cells in vitro by assessing cell proliferation and migration.
RESULTS: PROX1 expression was higher in ESCC than in normal tissues. Patients with higher PROX1 expression (n = 26) had increased nuclear accumulation of HIF1α (p = 0.004) and more advanced metastasis, both lymph node (N factor; p = 0.09) and hematogenous (M factor; p = 0.04), than those with lower PROX1 expression (n = 91). In addition, high PROX1 and HIF1α expression correlated with low levels of E-cadherin, an epithelial cell marker. Analysis of overall and cancer-specific survival indicated that elevated PROX1 expression was significantly correlated with poor prognosis (p = 0.0064). PROX1 downregulation in ESCC cells inhibited cellular proliferation and migration (p < 0.05). Hypoxia restored PROX1 levels that were reduced by PROX1-specific siRNA.
CONCLUSION: Our data suggest that high expression of PROX1 in ESCC could be used as an indicator of poor prognosis, and that PROX1 is a promising candidate molecular target for ESCC treatment.

Lin F, Li Y, Yan S, et al.
MicroRNA-181a inhibits tumor proliferation, invasiveness, and metastasis and is downregulated in gastric cancer.
Oncol Res. 2015; 22(2):75-84 [PubMed] Related Publications
MicroRNAs (miRNAs) play crucial roles in the development and progression of human cancers, including gastric cancer. The discovery of miRNAs may provide a new and powerful tool for studying the mechanism, diagnosis, and treatment of gastric cancer. Here we show that miR-181a levels were significantly downregulated in gastric cancer tissues compared with the adjacent normal regions in 80 paired samples. Moreover, the lower levels of miR-181a were associated with the pM or pTNM stage in clinical gastric cancer patients. In addition, the ectopic expression of miR-181a in the gastric cancer cell line HGC-27 inhibited cell proliferation, cell migration, and invasion by directly interacting with the mRNA encoding the oncogenic factor Prox1. Taken together, our results indicate that miR-181a might act as a tumor suppressor in gastric cancer, which may provide a novel diagnostic and therapeutic option for human gastric cancer in the near future.

Liu Y, Ye X, Zhang JB, et al.
PROX1 promotes hepatocellular carcinoma proliferation and sorafenib resistance by enhancing β-catenin expression and nuclear translocation.
Oncogene. 2015; 34(44):5524-35 [PubMed] Related Publications
Aberrant activation of the Wnt/β-catenin pathway is frequent in hepatocellular carcinoma (HCC) and contributes to HCC initiation and progression. This abnormal activation may result from somatic mutations in the genes of the Wnt/β-catenin pathway and/or dysregulation of the Wnt/β-catenin pathway. The mechanism for the latter remains poorly understood. Prospero-related homeobox 1 (PROX1) is a downstream target of the Wnt/β-catenin pathway in human colorectal cancer and elevated PROX1 expression promotes malignant progression. However, the Wnt/β-catenin pathway does not regulate PROX1 expression in the liver and HCC cells. Here we report that PROX1 promotes HCC cell proliferation in vitro and tumor growth in HCC xenograft mice. PROX1 and β-catenin levels are positively correlated in tumor tissues as well as in cultured HCC cells. PROX1 can upregulate β-catenin transcription by stimulating the β-catenin promoter and enhance the nuclear translocation of β-catenin in HCC cells, which leads to the activation of the Wnt/β-catenin pathway. Moreover, we show that increase in PROX1 expression renders HCC cells more resistant to sorafenib treatment, which is the standard therapy for advanced HCC. Overall, we have pinpointed PROX1 as a critical factor activating the Wnt/β-catenin pathway in HCC, which promotes HCC proliferation and sorafenib resistance.

Rodrigues MF, de Oliveira Rodini C, de Aquino Xavier FC, et al.
PROX1 gene is differentially expressed in oral cancer and reduces cellular proliferation.
Medicine (Baltimore). 2014; 93(28):e192 [PubMed] Free Access to Full Article Related Publications
Homeobox genes are a family of transcription factors that play a pivotal role in embryogenesis. Prospero homeobox 1 (PROX1) has been shown to function as a tumor suppressor gene or oncogene in various types of cancer, including oral squamous cell carcinoma (OSCC). We have previously identified PROX1 as a downregulated gene in OSCC. The aim of this study is to clarify the underlying mechanism by which PROX1 regulates tumorigenicity of OSCC cells. PROX1 mRNA and protein expression levels were first investigated in 40 samples of OSCC and in nontumor margins. Methylation and amplification analysis was also performed to assess the epigenetic and genetic mechanisms involved in controlling PROX1 expression. OSCC cell line SCC9 was also transfected to stably express the PROX1 gene. Next, SCC9-PROX1-overexpressing cells and controls were subjected to proliferation, differentiation, apoptosis, migration, and invasion assays in vitro. OSCC samples showed reduced PROX1 expression levels compared with nontumor margins. PROX1 amplification was associated with better overall survival. PROX1 overexpression reduces cell proliferation and downregulates cyclin D1. PROX1-overexpressing cells also exhibited reduced CK18 and CK19 expression and transcriptionally altered the expression of WISP3, GATA3, NOTCH1, and E2F1. Our results suggest that PROX1 functions as a tumor suppressor gene in oral carcinogenesis.

Ragusa S, Cheng J, Ivanov KI, et al.
PROX1 promotes metabolic adaptation and fuels outgrowth of Wnt(high) metastatic colon cancer cells.
Cell Rep. 2014; 8(6):1957-1973 [PubMed] Related Publications
The Wnt pathway is abnormally activated in the majority of colorectal cancers, and significant knowledge has been gained in understanding its role in tumor initiation. However, the mechanisms of metastatic outgrowth in colorectal cancer remain a major challenge. We report that autophagy-dependent metabolic adaptation and survival of metastatic colorectal cancer cells is regulated by the target of oncogenic Wnt signaling, homeobox transcription factor PROX1, expressed by a subpopulation of colon cancer progenitor/stem cells. We identify direct PROX1 target genes and show that repression of a pro-apoptotic member of the BCL2 family, BCL2L15, is important for survival of PROX1(+) cells under metabolic stress. PROX1 inactivation after the establishment of metastases prevented further growth of lesions. Furthermore, autophagy inhibition efficiently targeted metastatic PROX1(+) cells, suggesting a potential therapeutic approach. These data identify PROX1 as a key regulator of the transcriptional network contributing to metastases outgrowth in colorectal cancer.

Taban O, Cimpean AM, Raica M, Olariu S
PROX1 expression in gastric cancer: from hypothesis to evidence.
Anticancer Res. 2014; 34(7):3439-46 [PubMed] Related Publications
BACKGROUND: PROX1 is involved in cancer development and progression as both a tumor suppressor and oncogene. Immunohistochemical (IHC) PROX1 nuclear expression is a widely accepted pattern. Scattered data reported PROX1 IHC cytoplasmic expression in different tumors, including gastric cancer but it is not clear if this holds true.
MATERIALS AND METHODS: Evaluation of the cytoplasmic expression of PROX1 in normal gastric mucosa and gastric cancer was performed by IHC followed by RNAscope, an in situ hybridization-based method for detecting PROX1 mRNA amplification on paraffin-embedded samples and to evaluate its clinical impact.
RESULTS: Twenty five out of 48 cases of gastric cancer showed PROX1 nuclear and cytoplasmic immunohistochemical expression. Twelve out of these 20 cases positive for PROX1 on IHC (54.5%) had PROX1 mRNA gene amplification. The overlapping of PROX1 cytoplasmic expression assessed by immunohistochemistry and cytoplasmic RNAscope amplification was statistically significant (p=0.031). PROX1 mRNA gene amplification correlated with tumor grade (p=0.05) and regional lymph node metastasis as well (p=0.033). No significant correlation was obtained between PROX1 and histopathology, tumor size or distal metastasis.
CONCLUSION: A significant correlation was found between IHC and RNAscope PROX1 expression in the cytoplasm of normal and gastric cancer cells. This strongly supports its validation as a true expression on immunohistochemistry. A strong correlation between PROX1 mRNA amplification and regional lymph node metastasis supports its implications in cancer spreading and metastasis and sustains its utility, not only as a lymphatic marker, but also as a potential tumor marker in various tumor types, including gastric cancer.

Miyazaki H, Yoshimatsu Y, Akatsu Y, et al.
Expression of platelet-derived growth factor receptor β is maintained by Prox1 in lymphatic endothelial cells and is required for tumor lymphangiogenesis.
Cancer Sci. 2014; 105(9):1116-23 [PubMed] Free Access to Full Article Related Publications
The lymphatic system plays important roles not only in the physiological processes, such as maintenance of tissue fluid homeostasis, but also in pathological processes including the lymph node metastasis of tumor cells. Therefore, understanding of the molecular mechanisms underlying lymphatic vessel formation is crucial. Previous studies have shown that proliferation and migration of lymphatic endothelial cells (LECs) are activated by multiple types of signals mediated by tyrosine kinase receptors such as vascular endothelial growth factor receptor (VEGFR) 3. Although signals mediated by platelet-derived growth factor receptor β (PDGFRβ) have been implicated in lymphangiogenesis, the mechanisms explaining how PDGFRβ expression is maintained in LECs remain to be fully elucidated. In the present study, we show that PDGFRβ expression in LECs is maintained by Prox1 transcription factor. Knockdown of Prox1 expression in human dermal LECs decreased the expression of PDGFRβ, leading to the lowered migration of human dermal LECs towards PDGF-BB. Furthermore, we found that PDGF signals play important roles in inflammatory lymphangiogenesis in a chronic aseptic peritonitis model. Intraperitoneal administration of imatinib, a potent inhibitor of PDGFRβ, and transduction of PDGFRβ/Fc chimeric protein by an adenoviral system both reduced inflammatory lymphangiogenesis induced by thioglycollate in mice. We also found that the expression of PDGFRβ/Fc reduced tumor lymphangiogenesis in a BxPC3 human pancreatic cancer xenograft model. These findings suggest that PDGFRβ is one of the key mediators of lymphatic vessel formation acting downstream of Prox1.

Lv T, Liu Y, Zhang J, et al.
Impact of an altered PROX1 expression on clinicopathology, prognosis and progression in renal cell carcinoma.
PLoS One. 2014; 9(5):e95996 [PubMed] Free Access to Full Article Related Publications
The transcription factor PROX1 (prospero homeobox 1) has a critical role in the development of various organs, and has been implicated in both oncogenic and tumor-suppressive functions in human cancers. However, the role of PROX1 in the development of renal cell carcinomas (RCCs) has not yet been studied. Here, we reported that PROX1 expression was decreased in human RCC tissues compared with adjacent normal tissues. In RCC tissues, however, poorly differentiated RCC expressed higher PROX1 levels compared with well-differentiated RCC. In addition, the PROX1 immunostaining levels were positively correlated with tumor nuclear grade and lymph node metastasis. Further, high PROX1 expression indicated poor survival for patients. These findings imply that in the different developmental stages of RCC, PROX1 may exert distinct functions according to the specific microenvironment of tumor. Moreover, in vitro experiments revealed that PROX1 overexpression enhanced the proliferation and migration of RCC cells; conversely, PROX1 depletion by siRNA attenuated the proliferation and migration of RCC cells. Collectively, these observations suggest that PROX1 plays an important role in RCC development and progression, and PROX1 may be a novel target for prevention and treatment of RCC.

Wang L, Yuan W, Geng S, et al.
Expression of lymphatic markers in angiokeratomas.
J Cutan Pathol. 2014; 41(7):576-81 [PubMed] Related Publications
BACKGROUND: The term angiokeratoma refers to a group of unrelated diseases with similar histopathologic features. Four clinical variants of angiokeratoma have been described. However, it is not known whether some variants of angiokeratoma are of lymphatic origin, and an immunohistochemical study of lymphatic markers has not been previously performed.
METHODS: We performed an immunohistochemical study of angiokeratomas using lymphatic markers. Fifteen cases of angiokeratoma corporis diffusum, 10 cases of Fordyce angiokeratoma, 10 cases of Mibelli angiokeratoma and 10 cases of solitary angiokeratoma were examined by immunohistochemical analysis using CD31, D2-40, Prox1 and Wilms' tumor 1 (WT-1).
RESULTS: The vessels of angiokeratoma corporis diffusum, Fordyce angiokeratoma and solitary angiokeratoma were usually focally positive for D2-40 and positive for Prox1, whereas the vessels of Mibelli angiokeratoma were negative for D2-40 and positive for Prox1.
CONCLUSIONS: The results suggest lymphatic derivation of angiokeratoma corporis diffusum, Fordyce angiokeratoma and solitary angiokeratoma. However, the derivation of Mibelli angiokeratoma could not be determined based on the present immunohistochemical results.

Hirakawa S, Detmar M, Karaman S
Lymphatics in nanophysiology.
Adv Drug Deliv Rev. 2014; 74:12-8 [PubMed] Related Publications
Lymphatic vessels are essential for fluid transport and tissue homeostasis. Recent discoveries identified several genes, including Prox1 and VEGF-C, which are required for the lymphatic vessel development in physiological conditions as well as under pathological conditions such as chronic inflammation and tumor progression. Lymphatic vessels show morphological structures that are distinct between the initial lymphatic vessels and collectors, reflecting their respective functions of fluid absorption and transport. These differential structures are crucial for the physiological function of lymphatic vasculature. VEGF-A-mediated chronic inflammation impairs the fundamental structure of the initial lymphatic vessels, leading to delayed transport of nano-scaled fluorescence tracers. This article discusses recent findings that have clarified the biological function of lymphatic vessels in physiological and pathological settings. Assessments of the lymphatic function at nano-scale levels address the major contribution of lymphatic vessels to the kinetics of drug delivery and excretion.

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