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, VEGA, HGNC, Ensembl, GeneCard, Gene
Protein:prospero homeobox protein 1
Source:NCBIAccessed: 25 June, 2015


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

Cancer Overview

Research Indicators

Publications Per Year (1990-2015)
Graph generated 25 June 2015 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.

  • Vesicular Transport Proteins
  • Disease Progression
  • DNA Methylation
  • Cancer DNA
  • Tumor Suppressor Proteins
  • beta Catenin
  • Breast Cancer
  • Cell Proliferation
  • Mutation
  • Chromosome 1
  • Cancer RNA
  • Gene Expression Profiling
  • Pancreatic Cancer
  • Integrins
  • Cell Line
  • Lymphangiogenesis
  • Endothelial Cells
  • Messenger RNA
  • Angiogenesis
  • Vascular Endothelial Growth Factor Receptor-3
  • Immunohistochemistry
  • Oligonucleotide Array Sequence Analysis
  • Cancer Gene Expression Regulation
  • Colorectal Cancer
  • CpG Islands
  • Liver Cancer
  • Tumor Suppressor Gene
  • Colonic Neoplasms
  • Phenotype
  • Tumor Markers
  • Sensitivity and Specificity
  • Western Blotting
  • Homeodomain Proteins
  • Staging
  • Hepatocellular Carcinoma
  • Lymphatic Metastasis
  • U937 Cells
  • Vascular Endothelial Growth Factor D
  • Base Sequence
  • cdc25 Phosphatases
  • Apoptosis
Tag cloud generated 25 June, 2015 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)

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] 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):1957-73 [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] 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.

Zhu SH, Shan CJ, Wu ZF, Xu SZ
Proliferation of small cell lung cancer cell line reduced by knocking-down PROX1 via shRNA in lentivirus.
Anticancer Res. 2013; 33(8):3169-75 [PubMed] Related Publications
The present study aimed to find whether PROX1 is expressed in small cell lung cancer (SCLC) cell lines, and whether PROX1 knockdown with shRNA via lentivirus resulted in decreased cell proliferation. SCLC cell lines H69, H82, H187 and H889 were selected for the study. PROX1 mRNA and protein levels were determined with real-time reverse-transcription polymerase chain reaction(RT-PCR) and western blot, respectively. The localization and distribution of PROX1 was mapped by immunocytochemistry with a specific antibody. Three pairs of shRNA were selected from a pool of shRNA pairs, and packaged into lentivirus particles to infect the above cell lines. The non-target sequence (NT) and a house-keeping gene, glyceraldehyde 3 phosphate dehydrogenase (GAPDH), were employed as controls. SCLC cell proliferation rates were measured with bromine deoxyuridine (BrdU) incorporation method. The results indicated levels of that PROX1 mRNA were detected in SCLC cell lines in the following rank order H69>H889>H187>H82. A similar profile for PROX1 protein expression was captured. The majority of PROX1 was concentrated at the cell nucleus. H69 was selected to represent the above SCLC cell lines. The PROX1 level in H69 cells was successfully reduced with shRNA lentivirus, and the cell proliferation rate of infected H69 cells was dramatically reduced by 20-50%. Hence, it is concluded that PROX1 expression in SCLC cell line is high, and can be reduced with shRNA lentivirus, thereby reducing the cell proliferation rate.

Miettinen M, Wang Z, Sarlomo-Rikala M, et al.
ERG expression in epithelioid sarcoma: a diagnostic pitfall.
Am J Surg Pathol. 2013; 37(10):1580-5 [PubMed] Free Access to Full Article Related Publications
ERG transcription factor is constitutively expressed in endothelial cells. Because benign and malignant vascular endothelia retain the ERG expression, ERG is considered a useful marker for angiosarcomas and related tumors. ERG is also expressed in a subset of prostate carcinomas and Ewing sarcomas due to ERG-involved translocations; therefore, this marker is also of high interest in the study of these malignancies. In this study, we evaluated 109 epithelioid sarcomas for ERG expression, on the basis of an initial observation of an ERG-positive case. We also studied expression of other endothelial antigens in epithelioid sarcoma. ERG was expressed in 38% of epithelioid sarcomas (41/109), usually with a uniform nuclear staining, similar to that seen in angiosarcomas. However, all epithelioid sarcomas were negative for ERG gene rearrangement indicating that ERG expression is not likely related to ERG-involving translocations in epithelioid sarcoma. Other endothelial markers, CD31, claudin 5, and Prox1, were absent in epithelioid sarcomas. The only exception was a pulmonary metastasis of epithelioid sarcoma showing focal CD31 expression, which probably resulted from antigen adsorption onto tumor cell surfaces. However, podoplanin was commonly (7/9) expressed in epithelioid sarcoma; therefore, this marker is not useful in distinguishing epithelioid sarcoma from angiosarcoma. INI1/SMARCB1 gene product was absent in all epithelioid sarcomas (considered here a definitional feature) but was absent from only 1 epithelioid angiosarcoma, indicating its relative specificity for epithelioid sarcoma in this differential diagnostic setting. ERG expression is fairly common in epithelioid sarcoma and should be recognized as a diagnostic pitfall in the differential diagnosis of epithelioid sarcoma and epithelioid angiosarcoma. General lack of endothelial cell-specific markers in epithelioid sarcoma helps in this distinction.

Ghasemi R, Ghaffari SH, Momeny M, et al.
Multitargeting and antimetastatic potentials of silibinin in human HepG-2 and PLC/PRF/5 hepatoma cells.
Nutr Cancer. 2013; 65(4):590-9 [PubMed] Related Publications
Hepatocellular carcinoma (HCC) is the most common sort of primary liver malignancy with poor prognosis. This study aimed at examining the effects of silibinin (a putative antimetastatic agent) on some transcriptional markers mechanistically related to HCC recurrence and metastasis in HepG-2 [hepatitis B virus (HBV)-negative and P53 intact) and PLC/PRF/5 (HBV-positive and P53 mutated) cells. The expression of 27 genes in response to silibinin was evaluated by real-time RT-PCR. The MMP gelatinolytic assay and microculture tetrazolium test (MTT) were tested. Silibinin was capable of suppressing the transcriptional levels of ANGPT2, ATP6L, CAP2, CCR6, CCR7, CLDN-10, cortactin, CXCR4, GLI2, HK2, ID1, KIAA0101, mortalin, PAK1, RHOA, SPINK1, and STMN1 as well as the enzymatic activity of MMP-2 but promoted the transcripts of CREB3L3, DDX3X, and PROX1 in both cells. Some significant differences between the cells in response to silibinin were detected that might be related to the differences of the cells in terms of HBV infection and/or P53 mutation, suggesting the possible influence of silibinin on HCC through biological functions of these 2 prognostic factors. In conclusion, our findings suggest that silibinin could potentially function as a multitargeting antimetastatic agent and might provide new insights for HCC therapy particularly for HBV-related and/or P53-mutated HCCs.

Molinský J, Klánová M, Maswabi B, et al.
In vivo growth of mantle cell lymphoma xenografts in immunodeficient mice is positively regulated by VEGF and associated with significant up-regulation of CD31/PECAM1.
Folia Biol (Praha). 2013; 59(1):26-31 [PubMed] Related Publications
Mantle cell lymphoma (MCL) is an aggressive lymphoma subtype with dismal prognosis. New treatments are needed to improve outcome of relapsed/ refractory disease. Recently, several drugs targeting at least partially the process of angiogenesis have been successfully tested in the therapy of MCL. Molecular mechanisms that regulate MCL-induced angiogenesis and that might represent potential new druggable targets remain, however, incompletely understood. We established two mouse models of human MCL by subcutaneous xenotransplantation of JEKO-1 and HBL-2 cell lines into immunodeficient mice. Histological analyses of xenografts confirmed their neovascularization. The growth of xenografts was significantly suppressed by single-agent therapy with bevacizumab, monoclonal antibody targeting vascular endothelial growth factor (VEGF). Subsequently, we analysed expression of 94 angiogenesis related genes in ex vivo isolated JEKO-1 and HBL-2 cells compared to in vitro growing cells using TaqMan low-density arrays. The most up-regulated genes in both JEKO-1 and HBL-2 xenografts were genes encoding platelet/endothelial cell-adhesion molecule (CD31/PECAM1), VEGF receptor 1 (FLT1), hepatocyte growth factor (HGF), angiogenin (ANG) and transcription factor PROX1. The most downregulated genes in both JEKO-1 and HBL-2 xenografts were midkine (MDK) and ephrine B2 (EPHB2). In summary, our results demonstrate an important role of angiogenesis in the biology of MCL and provide preclinical evidence of potent anti-MCL activity of bevacizumab. In addition, gene expression profiling of 94 angiogenesis-related targets revealed several in vivo up-regulated and down-regulated transcripts. The most differentially expressed target in both MCL tumours was CD31/PECAM1. Whether any of these molecules might represent a potential druggable target in MCL patients remains to be elucidated.

Liu Y, Zhang JB, Qin Y, et al.
PROX1 promotes hepatocellular carcinoma metastasis by way of up-regulating hypoxia-inducible factor 1α expression and protein stability.
Hepatology. 2013; 58(2):692-705 [PubMed] Related Publications
UNLABELLED: Hepatocellular carcinoma (HCC) is one of the most common cancers and the third leading cause of death from cancer worldwide. HCC has a very poor prognosis because of tumor invasiveness, frequent intrahepatic spread, and extrahepatic metastasis. The molecular mechanism of HCC invasiveness and metastasis is poorly understood. The homeobox protein PROX1 is required for hepatocyte migration during mouse embryonic liver development. In this study, we show that high PROX1 protein expression in primary HCC tissues is associated with significantly worse survival and early tumor recurrence in postoperative HCC patients. Knockdown of PROX1 expression in HCC cells inhibited cell migration and invasiveness in vitro and HCC metastasis in nude mice while overexpression of PROX1 in HCC cells promoted these processes. PROX1's pro-metastasis activity is most likely attributed to its up-regulation of hypoxia-inducible factor 1α (HIF-1α) transcription and stabilization of HIF-1α protein by recruiting histone deacetylase 1 (HDAC1) to prevent the acetylation of HIF-1α, which subsequently induces an epithelial-mesenchymal transition response in HCC cells. We further demonstrated the prognostic value of using the combination of PROX1 and HDAC1 levels to predict postoperative survival and early recurrence of HCC.
CONCLUSION: PROX1 is a critical factor that promotes HCC metastasis.

Masuzawa M, Masuzawa M, Hamada Y, et al.
Establishment and characterization of a novel lymphangiosarcoma cell line (MO-LAS) compared with the hemangiosarcoma cell line (ISO-HAS).
Cancer Med. 2012; 1(1):39-46 [PubMed] Free Access to Full Article Related Publications
The concept of "lymphangiosarcoma" remains obscure. Therefore, we reported a patient with lymphangiosarcoma, resistant to immunotherapy. The patient presented with impressive and discriminative features: clinically an ill-defined edematous lesion with lymphorrhea and pathologically atypical vascular channel formation without extravasation of blood, clearly distinguished from common angiosarcoma with hemorrhage. From this case, a lymphangiosarcoma cell line, MO-LAS, was established and its characteristics were compared with the hemangiosarcoma cell line, ISO-HAS. Flow cytometric analysis revealed that MO-LAS was negative for factor VIII-related antigen, but positive for CD31, D2-40, NZ-1, and vascular endothelial growth factor receptor-3 (VEGFR-3), similar to ISO-HAS. However, MO-LAS expressed a much higher level of homeobox gene PROX1, indicating a lymphatic phenotype, compared with ISO-HAS. Furthermore, MO-LAS showed a much lesser expression of oncogenes and much lower sensitivity against lymphokine-activated killer (LAK) cells. Lymphangiosarcoma may be difficult to recognize by the immune system. Conclusively, the establishment of MO-LAS, a novel angiosarcoma cell line bearing lymphatic characters, strongly suggests the entity of lymphangiosarcoma.

Chang TM, Hung WC
The homeobox transcription factor Prox1 inhibits proliferation of hepatocellular carcinoma cells by inducing p53-dependent senescence-like phenotype.
Cancer Biol Ther. 2013; 14(3):222-9 [PubMed] Free Access to Full Article Related Publications
The homeobox transcription factor Prox1 is highly expressed in adult hepatocytes and is involved in the regulation of bile acid synthesis and gluconeogenesis in the liver by interacting with other transcriptional activators or repressors. Recent studies showed that Prox1 could inhibit proliferation of hepatocellular carcinoma (HCC) cells and reduced Prox1 expression was associated with poor prognosis of HCC patients. However, the underlying mechanism by which Prox1 attenuates HCC growth is still unclear. In this study, we demonstrated that Prox1 induced senescence-like phenotype of HCC cells to reduce cell proliferation. Our results indicated that the tumor suppressor p53 is a key mediator of Prox1-induced growth suppression because Prox1 only induced senescence-like phenotype in HCC cells harboring wild type p53. In addition, knockdown of p53 by shRNA reversed the effect of Prox1. However, chromatin immunoprecipitation assay did not demonstrate the direct binding of Prox1 to proximal promoter of human p53 gene suggesting Prox1 might not directly activate p53 transcription. We found that Prox1 suppressed Twist expression in HCC cells and subsequently relieved its inhibition on p53 gene transcription. The involvement of Twist in the regulation of p53 by Prox1 was supported by the following evidence: (1) Prox1 inhibited Twist expression and promoter activity; (2) knockdown of Twist in SK-HEP-1 cells upregulated p53 expression and (3) ectopic expression of Twist counteracted Prox1-induced p53 transcription and senescence-like phenotype. We also indentified an E-box located at p53 promoter which is required for Twist to inhibit p53 expression. Finally, our animal experiment confirmed that Prox1 suppressed HCC growth in vivo. Collectively, we conclude that Prox1 suppresses proliferation of HCC cells via inhibiting Twist to trigger p53-dependent senescence-like phenotype.

Lu MH, Huang CC, Pan MR, et al.
Prospero homeobox 1 promotes epithelial-mesenchymal transition in colon cancer cells by inhibiting E-cadherin via miR-9.
Clin Cancer Res. 2012; 18(23):6416-25 [PubMed] Related Publications
PURPOSE: Prospero homeobox 1 (PROX1) has been shown to function as a tumor suppressor in various types of cancer. However, it promotes colon cancer progression. The aim of this study is to clarify the underlying mechanism by which PROX1 regulates tumorigenicity of colon cancer.
EXPERIMENTAL DESIGN: Association of PROX1 and clinicopathological features was studied by immunohistochemical staining. Pri-miR-9-2 and miR-9 were detected by quantitative real-time PCR. Assays of cell invasion, adhesion, and matrix metalloproteinase activity were used to study PROX1-mediated epithelial-mesenchymal transition (EMT).
RESULTS: PROX1 was overexpressed in 43% (59/136) of colon cancer tissues and its expression was correlated with E-cadherin downregulation (P = 0.00005), advanced tumor staging (P = 0.005), and lymph node metastasis (P = 0.000009). Enforced expression of PROX1 in DLD-1 cells caused downregulation of E-cadherin and integrins and attenuated cell adhesion. These cells showed increase of matrix metalloproteinase activity and invasive ability. Conversely, knockdown of PROX1 in SW620 cells restored E-cadherin protein expression and reduced invasiveness. Unexpectedly, repression of E-cadherin by PROX1 was not mediated by transcriptional inhibition. We found that PROX1 bound to miR-9-2 promoter and triggered its expression to suppress E-cadherin 3'UTR reporter activity and protein expression. Anti-miR-9 restored E-cadherin in SW620 cells, whereas precursor miR-9 inhibited E-cadherin in PROX1-knockdown cells. The miR-9 level was higher in tumor tissues with high PROX1/low E-cadherin than that of tumor tissues with low PROX1/high E-cadherin.
CONCLUSIONS: Our results provide mechanistic insights by which PROX1 promotes EMT and colon cancer progression. Targeting of PROX1-mediated oncogenic activity may be helpful for the treatment of colon cancer.

Chang TM, Hung WC
Transcriptional repression of TWIST1 gene by Prospero-related homeobox 1 inhibits invasiveness of hepatocellular carcinoma cells.
FEBS Lett. 2012; 586(20):3746-52 [PubMed] Related Publications
Prospero-related homeobox 1 (PROX1) is important for liver development and down-regulation of this transcription factor in hepatocellular carcinoma (HCC) is associated with poor prognosis. We find that PROX1 expression is inversely correlated with the expression of epithelial-mesenchymal regulator TWIST1 in HCC cell lines and tumor tissues. We demonstrate that PROX1 directly binds to proximal promoter of TWIST1 gene to repress its transcription and inhibits its downstream target gene AKT2 expression which leads to reduction of cell migration and invasion. Moreover, PROX1 attenuates lung metastasis of HCC in vivo. These results support an anti-metastatic role of PROX1 via inhibiting TWIST1.

Aguilar B, Choi I, Choi D, et al.
Lymphatic reprogramming by Kaposi sarcoma herpes virus promotes the oncogenic activity of the virus-encoded G-protein-coupled receptor.
Cancer Res. 2012; 72(22):5833-42 [PubMed] Free Access to Full Article Related Publications
Kaposi sarcoma, the most common cancer in HIV-positive individuals, is caused by endothelial transformation mediated by the Kaposi sarcoma herpes virus (KSHV)-encoded G-protein-coupled receptor (vGPCR). Infection of blood vascular endothelial cells (BEC) by KSHV reactivates an otherwise silenced embryonic program of lymphatic differentiation. Thus, Kaposi sarcoma tumors express numerous lymphatic endothelial cell (LEC) signature genes. A key unanswered question is how lymphatic reprogramming by the virus promotes tumorigenesis leading to Kaposi sarcoma formation. In this study, we present evidence that this process creates an environment needed to license the oncogenic activity of vGPCR. We found that the G-protein regulator RGS4 is an inhibitor of vGPCR that is expressed in BECs, but not in LECs. RGS4 was downregulated by the master regulator of LEC differentiation PROX1, which is upregulated by KSHV and directs KSHV-induced lymphatic reprogramming. Moreover, we found that KSHV upregulates the nuclear receptor LRH1, which physically interacts with PROX1 and synergizes with it to mediate repression of RGS4 expression. Mechanistic investigations revealed that RGS4 reduced vGPCR-enhanced cell proliferation, migration, VEGF expression, and Akt activation and suppressed tumor formation induced by vGPCR. Our findings resolve long-standing questions about the pathologic impact of KSHV-induced reprogramming of host cell identity, and they offer biologic and mechanistic insights supporting the hypothesis that a lymphatic microenvironment is more favorable for Kaposi sarcoma tumorigenesis.

Elsir T, Smits A, Lindström MS, Nistér M
Transcription factor PROX1: its role in development and cancer.
Cancer Metastasis Rev. 2012; 31(3-4):793-805 [PubMed] Related Publications
The homeobox gene PROX1 is critical for organ development during embryogenesis. The Drosophila homologue, known as prospero has been shown to act as a tumor suppressor by controlling asymmetric cell division of neuroblasts. Likewise, alterations in PROX1 expression and function are associated with a number of human cancers including hematological malignancies, carcinomas of the pancreas, liver and the biliary system, sporadic breast cancer, Kaposiform hemangioendothelioma, colon cancer, and brain tumors. PROX1 is involved in cancer development and progression and has been ascribed both tumor suppressive and oncogenic properties in a variety of different cancer types. However, the exact mechanisms through which PROX1 regulates proliferation, migration, and invasion of cancer cells are by large unknown. This review provides an update on the role of PROX1 in organ development and on its emerging functions in cancer, with special emphasis on the central nervous system and glial brain tumors.

Zhao Y, Guo S, Sun J, et al.
Methylcap-seq reveals novel DNA methylation markers for the diagnosis and recurrence prediction of bladder cancer in a Chinese population.
PLoS One. 2012; 7(4):e35175 [PubMed] Free Access to Full Article Related Publications
PURPOSE: There is a need to supplement or supplant the conventional diagnostic tools, namely, cystoscopy and B-type ultrasound, for bladder cancer (BC). We aimed to identify novel DNA methylation markers for BC through genome-wide profiling of BC cell lines and subsequent methylation-specific PCR (MSP) screening of clinical urine samples.
EXPERIMENTAL DESIGN: The methyl-DNA binding domain (MBD) capture technique, methylCap/seq, was performed to screen for specific hypermethylated CpG islands in two BC cell lines (5637 and T24). The top one hundred hypermethylated targets were sequentially screened by MSP in urine samples to gradually narrow the target number and optimize the composition of the diagnostic panel. The diagnostic performance of the obtained panel was evaluated in different clinical scenarios.
RESULTS: A total of 1,627 hypermethylated promoter targets in the BC cell lines was identified by Illumina sequencing. The top 104 hypermethylated targets were reduced to eight genes (VAX1, KCNV1, ECEL1, TMEM26, TAL1, PROX1, SLC6A20, and LMX1A) after the urine DNA screening in a small sample size of 8 normal control and 18 BC subjects. Validation in an independent sample of 212 BC patients enabled the optimization of five methylation targets, including VAX1, KCNV1, TAL1, PPOX1, and CFTR, which was obtained in our previous study, for BC diagnosis with a sensitivity and specificity of 88.68% and 87.25%, respectively. In addition, the methylation of VAX1 and LMX1A was found to be associated with BC recurrence.
CONCLUSIONS: We identified a promising diagnostic marker panel for early non-invasive detection and subsequent BC surveillance.

Foskolou IP, Stellas D, Rozani I, et al.
Prox1 suppresses the proliferation of neuroblastoma cells via a dual action in p27-Kip1 and Cdc25A.
Oncogene. 2013; 32(8):947-60 [PubMed] Related Publications
Neuroblastoma is a pediatric tumor that originates from precursor cells of the sympathetic nervous system with less than 40% long-term survival in children diagnosed with high-risk disease. These clinical observations underscore the need for novel insights in the mechanisms of malignant transformation and progression. Accordingly, it was recently reported that Prox1, a homeobox transcription regulator, is expressed in higher levels in human neuroblastoma with favorable prognosis. Consistently, we have recently shown that Prox1 exerts a strong antiproliferative effect on neural precursor cells during embryonic development. Thus, Prox1 is a candidate gene with a critical role in suppressing malignant neuroblastoma transformation. Here, we provide evidence that Prox1 strongly suppresses the proliferation of mouse and human neuroblastoma cell lines and blocks the growth of neuroblastoma tumors in SCID mice. Conversely, short hairpin RNA (shRNA) -mediated knockdown of basal Prox1 expression significantly induces proliferation, genomic instability and the ability of neuroblastoma cells to form tumors. Mechanistically, analysis of an inducible Prox1-overexpressing Neuro2A cell line indicates that Prox1 is sufficient to suppress CyclinD1, CyclinA and CyclinB1, consistent with a role in cell cycle arrest. Surprisingly, Prox1 strongly induces CyclinE1 expression in the same system despite its action on blocking cell cycle progression, which could account for the context dependent oncogenic function of Prox1. Most importantly, Prox1 was sufficient to decrease Cdc25A and induce p27-Kip1, but not p21-Cip1 or p53. By alleviating the Prox1 action in Cdc25A and p27-Kip1 expression, we were able to rescue its effect on cell cycle arrest. Together these data suggest that Prox1 negatively regulates neuroblastoma carcinogenesis through suppression of Cdc25A and induction of p27-Kip1 to counteract CyclinE1 overexpression and block cell cycle progression. Furthermore, these observations render Prox1 a candidate target for the treatment of neuroblastoma tumors.

Newman B, Lose F, Kedda MA, et al.
Possible genetic predisposition to lymphedema after breast cancer.
Lymphat Res Biol. 2012; 10(1):2-13 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Known risk factors for secondary lymphedema only partially explain who develops lymphedema following cancer, suggesting that inherited genetic susceptibility may influence risk. Moreover, identification of molecular signatures could facilitate lymphedema risk prediction prior to surgery or lead to effective drug therapies for prevention or treatment. Recent advances in the molecular biology underlying development of the lymphatic system and related congenital disorders implicate a number of potential candidate genes to explore in relation to secondary lymphedema.
METHODS AND RESULTS: We undertook a nested case-control study, with participants who had developed lymphedema after surgical intervention within the first 18 months of their breast cancer diagnosis serving as cases (n=22) and those without lymphedema serving as controls (n=98), identified from a prospective, population-based, cohort study in Queensland, Australia. TagSNPs that covered all known genetic variation in the genes SOX18, VEGFC, VEGFD, VEGFR2, VEGFR3, RORC, FOXC2, LYVE1, ADM, and PROX1 were selected for genotyping. Multiple SNPs within three receptor genes, VEGFR2, VEGFR3, and RORC, were associated with lymphedema defined by statistical significance (p<0.05) or extreme risk estimates (OR <0.5 or >2.0).
CONCLUSIONS: These provocative, albeit preliminary, findings regarding possible genetic predisposition to secondary lymphedema following breast cancer treatment warrant further attention for potential replication using larger datasets.

Ramani P, Norton A, Somerville MS, May MT
PROX1 lymphatic density correlates with adverse clinicopathological factors, lymph node metastases and survival in neuroblastomas.
J Neurooncol. 2012; 108(3):375-83 [PubMed] Related Publications
Increased lymphatic density correlates with lymph node metastases and survival in some epithelial cancers. The transcription factor, Prospero-related homeobox-gene 1, PROX1, plays an important role in the differentiation and proliferation of the lymphatic and nervous systems. We studied the clinicopathological significance of PROX1 expression in neuroblastomas (NBs) as the majority of patients have lymphatic and/or haematogenous metastases at diagnosis. PROX1-immunostained lymphatic vessels were present in 40/69 (58%) of NBs and 1/6 benign ganglioneuromas (GNs). Lymphatic density (LD) counts were significantly increased in NBs from patients with unfavourable clinical and pathological factors, and with distant lymph node metastases (LNM). Lymphatic invasion (LI) by tumoral emboli was present in 27/40 (68%) of NBs. A significantly higher proportion of LI was seen in undifferentiated/poorly-differentiated, (UD/PD) compared with differentiated NBs. LI was increased in NBs from patients with advanced-stage and high-risk group. Nuclear-PROX1 expression in tumoral cells was present in 35/69 (51%) NBs but was absent in all GNs. PROX1 expression was significantly higher in UD/PD compared with differentiated NBs. It was also higher in NBs with all adverse clinicopathological and biological variables. LI, PROX1 cellular expression and high LD correlated with a shorter overall survival and event-free survival (EFS). Multivariable Cox regression analysis showed that the effect of LD on both OS and EFS was independent of mitosis-karyorrhexis index and MYCN amplification. Increased LD, LI and cellular expression correlated with adverse factors in NBs. Increased LD correlated with LNM suggesting that PROX1 contributes to neuroblastoma progression and lymphatic spread.

Rauch TA, Wang Z, Wu X, et al.
DNA methylation biomarkers for lung cancer.
Tumour Biol. 2012; 33(2):287-96 [PubMed] Related Publications
Changes in DNA methylation patterns are an important characteristic of human cancer including lung cancer. In particular, hypermethylation of CpG islands is a signature of malignant progression. Methylated CpG islands are promising diagnostic markers for the early detection of cancer. However, the full extent and sequence context of DNA hypermethylation in lung cancer has remained unknown. We have used the methylated CpG island recovery assay and high-resolution microarray analysis to find hypermethylated CpG islands in squamous cell carcinomas (SCC) and adenocarcinomas of the lung. Each tumor contained several hundred hypermethylated CpG islands. In an initial microarray screen, 36 CpG islands were methylated in five of five (=100%) of the SCC tumors tested and 52 CpG islands were methylated in at least 75% of the adenocarcinomas tested (n=8). Using sodium-bisulfite-based approaches, 12 CpG islands (associated with the BARHL2, EVX2, IRX2, MEIS1, MSX1, NR2E1, OC2, OSR1, OTX1, PAX6, TFAP2A, and ZNF577 genes) were confirmed to be methylated in 85% to 100% of the squamous cell carcinomas and 11 CpG islands (associated with the CHAD, DLX4, GRIK2, KCNG3, NR2E1, OSR1, OTX1, OTX2, PROX1, RUNX1, and VAX1 genes) were methylated in >80% of the adenocarcinomas. From the list of genes that were methylated in lung adenocarcinomas, we identified the gene FAT4 and found that this gene was methylated in 39% of the tumors. FAT4 is the closest mammalian homologue of the Drosophila tumor suppressor Fat which is an important component of the Hippo growth control pathway. Many of these newly discovered methylated CpG islands hold promise for becoming biomarkers for the early detection of lung cancer.

Azuma K, Urano T, Watabe T, et al.
PROX1 suppresses vitamin K-induced transcriptional activity of Steroid and Xenobiotic Receptor.
Genes Cells. 2011; 16(11):1063-70 [PubMed] Related Publications
Steroid and Xenobiotic Receptor (SXR) belongs to nuclear receptor superfamily. It was shown that secondary bile acids such as lithocholic acid and several chemical compounds such as rifampicin could be ligands for this receptor. Recently, we have demonstrated that vitamin K2 also serves as a ligand for SXR and activation of SXR by vitamin K2 suppressed proliferation and motility of hepatocellular carcinoma (HCC) cells. To analyze function of SXR in HCC cells, we overexpressed exogenous SXR double-tagged with FLAG and HA in a HCC cell line, HepG2 cells, and purified SXR-binding molecules by immunoprecipitation from the nuclear extracts of these cells. Several binding molecules were identified by TOF-MS analyses. One of the SXR-binding molecules was a transcription factor PROX1. We confirmed the interaction of PROX1 and SXR in HEK293 cells. Then, we have shown that AF2 domain of SXR is necessary for binding with PROX1. We further demonstrated that PROX1 negatively regulated the transcriptional activity of SXR by promoter analyses of SXR target gene. These results suggest that PROX1 could negatively regulate SXR signals in some tumor cells, such as HCC cells, where both SXR and PROX1 are expressed.

Edvardsson K, Ström A, Jonsson P, et al.
Estrogen receptor β induces antiinflammatory and antitumorigenic networks in colon cancer cells.
Mol Endocrinol. 2011; 25(6):969-79 [PubMed] Related Publications
Several studies suggest estrogen to be protective against the development of colon cancer. Estrogen receptor β (ERβ) is the predominant estrogen receptor expressed in colorectal epithelium and is the main candidate to mediate the protective effects. We have previously shown that expression of ERβ reduces growth of colorectal cancer in xenografts. Little is known of the actions of ERβ and its effect on gene transcription in colon cancers. To dissect the processes that ERβ mediates and to investigate cell-specific mechanisms, we reexpressed ERβ in three colorectal cancer cell lines (SW480, HT29, and HCT-116) and conducted genome-wide expression studies in combination with gene-pathway analyses and cross-correlation to ERβ-chromatin-binding sites. Although induced gene regulation was cell specific, overrepresentation analysis of functional classes indicated that the same biological themes, including apoptosis, cell differentiation, and regulation of the cell cycle, were affected in all three cell lines. Novel findings include a strong ERβ-mediated down-regulation of IL-6 and downstream networks with significant implications for inflammatory mechanisms involved in colon carcinogenesis. We also discovered cross talk between the suggested nuclear receptor coregulator PROX1 and ERβ, demonstrating that ERβ both regulates and shares target genes with PROX1. The influence of ERβ on apoptosis was further explored using functional studies, which suggested an increased DNA-repair capacity. We conclude that reexpression of ERβ induces transcriptome changes that, through several parallel pathways, converge into antitumorigenic capabilities in all three cell lines. We propose that enhancing ERβ action has potential as a novel therapeutic approach for prevention and/or treatment of colon cancer.

Le Huu AR, Jokinen CH, Rubin BP, et al.
Expression of prox1, lymphatic endothelial nuclear transcription factor, in Kaposiform hemangioendothelioma and tufted angioma.
Am J Surg Pathol. 2010; 34(11):1563-73 [PubMed] Related Publications
Kaposiform hemangioendothelioma (KHE) and tufted angioma (TA) are rare tumors mainly occurring in early childhood. Our recent results showed that ectopic overexpression of human Prox1 gene, a lymphatic endothelial nuclear transcription factor, promoted an aggressive behavior in 2 murine models of KHE. This dramatic Prox1-induced phenotype prompted us to investigate immunohistochemical staining pattern of Prox1, podoplanin (D2-40), LYVE-1, and Prox1/CD34 as well as double immunofluorescent staining pattern of LYVE-1/CD31 in KHE and TA, compared with other pediatric vascular tumors. For this purpose, we examined 75 vascular lesions: KHE (n=18), TA (n=13), infantile hemangioma (n=13), pyogenic granuloma (n=18), and granulation tissue (n=13). Overall, KHE and TA shared an identical endothelial immunophenotype: the neoplastic spindle cells were Prox1, podoplanin, LYVE-1, CD31, and CD34, whereas endothelial cells within glomeruloid foci were Prox1, podoplanin, LYVE-1, CD31, and CD34. The lesional cells of all infantile hemangiomas and pyogenic granulomas were negative for Prox1 in the presence of positive internal control. These findings provide immunophenotypic evidence to support a preexisting notion that KHE and TA are closely related, if not identical. Overall, our results show, for the first time, that Prox1 is an immunohistochemical biomarker helpful in confirming the diagnosis of KHE/TA and in distinguishing it from infantile hemangioma and pyogenic granuloma.

Yoo J, Kang J, Lee HN, et al.
Kaposin-B enhances the PROX1 mRNA stability during lymphatic reprogramming of vascular endothelial cells by Kaposi's sarcoma herpes virus.
PLoS Pathog. 2010; 6(8):e1001046 [PubMed] Free Access to Full Article Related Publications
Kaposi's sarcoma (KS) is the most common cancer among HIV-positive patients. Histogenetic origin of KS has long been elusive due to a mixed expression of both blood and lymphatic endothelial markers in KS tumor cells. However, we and others discovered that Kaposi's sarcoma herpes virus (KSHV) induces lymphatic reprogramming of blood vascular endothelial cells by upregulating PROX1, which functions as the master regulator for lymphatic endothelial differentiation. Here, we demonstrate that the KSHV latent gene kaposin-B enhances the PROX1 mRNA stability and plays an important role in KSHV-mediated PROX1 upregulation. We found that PROX1 mRNA contains a canonical AU-rich element (ARE) in its 3'-untranslated region that promotes PROX1 mRNA turnover and that kaposin-B stimulates cytoplasmic accumulation of the ARE-binding protein HuR through activation of the p38/MK2 pathway. Moreover, HuR binds to and stabilizes PROX1 mRNA through its ARE and is necessary for KSHV-mediated PROX1 mRNA stabilization. Together, our study demonstrates that kaposin-B plays a key role in PROX1 upregulation during lymphatic reprogramming of blood vascular endothelial cells by KSHV.

Wangsa D, Heselmeyer-Haddad K, Ried P, et al.
Fluorescence in situ hybridization markers for prediction of cervical lymph node metastases.
Am J Pathol. 2009; 175(6):2637-45 [PubMed] Free Access to Full Article Related Publications
The presence of lymph node metastases is associated with poor prognosis in early stage cervical cancer. As of yet, no molecular markers predicting lymph node metastases have been identified. We examined single genetic markers and a composite marker, comprised of three fluorescence in situ hybridization (FISH) probes targeting the genes LAMP3, PROX1, and PRKAA1, in pretreatment cervical biopsies from 16 lymph node positive cases and 15 lymph node negative controls from women with stage IB and IIA cervical cancer. In addition, we determined clonal patterns by including CCND1 to compare the clonal constitution of primary tumors and associated lymph node metastases. The composite FISH marker allowed for classification of patients into those with and without lymph node metastases with a sensitivity and specificity of 75% and 87%, respectively (P = 0.001). The positive predictive value and negative predictive value were 86% and 76%, respectively. Clonal patterns varied among the tumors. In many cases, changes between the primary tumor and lymph node metastases in the most common clones may indicate that certain clones have a growth advantage for establishing metastases in lymph nodes. We conclude that the composite FISH marker may be useful for determining risk for subsequent development of lymph node metastases in patients with cervical cancer.

Vitoux D, Mourah S, Kerob D, et al.
Highly sensitive multivariable assay detection of melanocytic differentiation antigens and angiogenesis biomarkers in sentinel lymph nodes with melanoma micrometastases.
Arch Dermatol. 2009; 145(10):1105-13 [PubMed] Related Publications
OBJECTIVES: To evaluate the prognostic value of melanocytic differentiation antigens and angiogenesis biomarkers in sentinel lymph nodes (SLNs) with melanoma micrometastases.
DESIGN: Prognostic study of an inception cohort.
SETTING: Academic research. Patients Between July 1, 1999, and July 31, 2002, all patients who had primary cutaneous or mucosal melanomas that have a Breslow depth of 1.5 mm or greater, ulceration, or Clark level IV or V, or had SLN biopsies.
MAIN OUTCOME MEASURES: By the use of quantitative reverse transcription-polymerase chain reaction, the expression of the following was analyzed in SLNs: 2 melanocytic differentiation antigens (tyrosinase [P17646] and melanoma antigen recognized by T cells [MART-1; Q16655]) and genes involved in angiogenesis (VEGF [NM_001025366] and VEGFR2 [AF035121]), lymphangiogenesis (VEGFC [NM_005429], VEGFR3 [X68203], LYVE1 [NM_016164], and PROX1 [002763]), and invasion (uPA [NM_002658], PAI1 [NM_00602], and EMMPRIN [L10240]). Outcome measures were the association of these melanocytic differentiation antigens and angiogenesis biomarkers with clinicopathologic characteristics of patients, and an evaluation of the prognostic value for relapse-free survival and overall survival.
RESULTS: Ninety-one patients were included, with a median follow-up period of 41 months. Micrometastases were present in 15% (14 of 91) of patients. Tyrosinase (P < .001), MART-1 (P < .001), vascular endothelial growth factor 121 (VEGF(121)) (P = .007), and PAI1 (P = .02) expression was significantly associated with micrometastasis. In univariate analysis, histologic findings and tyrosinase and MART-1 expression were significantly associated with relapse-free survival. Tyrosinase and MART-1 expression was associated with overall survival. A multiple Cox proportional hazards regression model identified negative histologic findings and tyrosinase expression that exceeded 27 copies/copy of TATA box-binding protein (third quartile) as significantly associated with an increased risk of relapse or death.
CONCLUSIONS: Quantitative assessment of melanocytic differentiation antigens in SLNs, which has prognostic value, is more specific than qualitative assessment. Prognosis may be more effectively predicted by the combination of quantitative assessment of melanocytic differentiation antigens in SLNs with histologic assessment. A significant association was found between the presence of micrometastases and the expression of angiogenesis biomarkers.

Balla MM, Vemuganti GK, Kannabiran C, et al.
Phenotypic characterization of retinoblastoma for the presence of putative cancer stem-like cell markers by flow cytometry.
Invest Ophthalmol Vis Sci. 2009; 50(4):1506-14 [PubMed] Related Publications
PURPOSE: Retinoblastoma (Rb) is an intraocular tumor that grows rapidly and poses a threat to sight and life. Similar to other tumors, there is increasing speculation that the Rb tumor also contains cancer stem-like cells that could influence the prognosis and response to therapy. This study was undertaken in an attempt to identify putative stem-like cells by characterizing different subpopulations of cells in retinoblastoma.
METHODS: Freshly isolated tumor cells obtained from unfixed eye specimens (n=7) were analyzed for the presence of CD44, ABCG2, CXCR4, CD133, and CD90 using flow cytometry. RT-PCR was performed to analyze the expression of human Syntaxin1A, PROX1, CD133, and NSE in the sorted subpopulation of tumor cells.
RESULTS: Two different subpopulations of cells were observed in seven samples. The small cells, assigned FSC(lo)/SSC(lo) (forward scatter low/side scatter low, ranging from 1.7% to 17.7%) were characterized as positive for CD44 and negative for CD133, CXCR4, and CD90. The large cells were designated as FSC(hi)/SSC(lo) (ranging from 2.7% to 35.1%) and characterized as positive for all markers. RT-PCR analysis revealed that sorted cells of FSC(lo)/SSC(lo) subpopulation expressed the retinal progenitor cell markers PROX1 and Syntaxin1A.
CONCLUSIONS: Retinoblastoma, on flow cytometric analysis, revealed two distinct subpopulations with variable expression of stem cell and retinal progenitor markers. In these populations, the FSC(lo)/SSC(lo) subpopulation appeared to be more primitive, since they expressed stem cell (CD44) and retinal progenitor markers (PROX1 and Syntaxin 1A) combined with a relatively lower percentage of differentiated markers. Moreover, the FSC(hi)/SSC(lo) subpopulation showed a higher percentage of differentiated markers (CD90 and CD133).

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