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The orphan nuclear receptor Nurr1 restricts the proliferation of haematopoietic stem cells.

ABSTRACT: Successful haematopoiesis requires long-term retention of haematopoietic stem cells (HSCs) in a quiescent state. The transcriptional regulation of stem cell quiescence, especially by factors with specific functions in HSCs, is only beginning to be understood. Here, we demonstrate that Nurr1, a nuclear receptor transcription factor, has such a regulatory role. Overexpression of Nurr1 drives early haematopoietic progenitors into quiescence. When stem cells overexpressing Nurr1 are transplanted into lethally irradiated mice, they localize to the bone marrow, but do not contribute to regeneration of the blood system. Furthermore, the loss of only one allele of Nurr1 is sufficient to induce HSCs to enter the cell cycle and proliferate. Molecular analysis revealed an association between Nurr1 overexpression and upregulation of the cell-cycle inhibitor p18 (also known as INK4C), suggesting a mechanism by which Nurr1 could regulate HSC quiescence. Our findings provide critical insight into the transcriptional control mechanisms that determine whether HSCs remain dormant or enter the cell cycle and begin to proliferate.

SUBMITTER: Sirin O

PROVIDER: S-EPMC3059561 | biostudies-literature | 2010 Dec

REPOSITORIES: biostudies-literature

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The orphan nuclear receptor Nurr1 restricts the proliferation of haematopoietic stem cells.

Sirin Olga O Lukov Georgi L GL Mao Rui R Conneely Orla M OM Goodell Margaret A MA

Nature cell biology 20101114 12

Successful haematopoiesis requires long-term retention of haematopoietic stem cells (HSCs) in a quiescent state. The transcriptional regulation of stem cell quiescence, especially by factors with specific functions in HSCs, is only beginning to be understood. Here, we demonstrate that Nurr1, a nuclear receptor transcription factor, has such a regulatory role. Overexpression of Nurr1 drives early haematopoietic progenitors into quiescence. When stem cells overexpressing Nurr1 are transplanted int ...[more]

PMID: 21076412

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Project description:NR4A orphan nuclear receptors are involved in multiple biological processes which are important in tumorigenesis such as cell proliferation, apoptosis, differentiation, and glucose utilization. The significance of NR4A family member NURR1 (NR4A2) in breast cancer etiology has not been elucidated. The purpose of this study was to ascertain the impact of NURR1 expression on breast transformation, tumor growth, and breast cancer patient survival.We determined the expression of NURR1 in normal breast versus breast carcinoma in tissue microarrays (immunohistochemistry), tissue lysates (immunoblot), and at the mRNA level (publically available breast microarrays). In addition NURR1 expression was compared among breast cancer patients in cohorts based on p53 expression, estrogen receptor ? expression, tumor grade, and lymph node metastases. Kaplan-Meier survival plots were used to determine the correlation between NURR1 expression and relapse free survival (RFS). Using shRNA-mediated silencing, we determined the effect of NURR1 expression on tumor growth in mouse xenografts.Results from breast cancer tissue arrays demonstrate a higher NURR1 expression in the normal breast epithelium compared to breast carcinoma cells (p???0.05). Among cases of breast cancer, NURR1 expression in the primary tumors was inversely correlated with lymph node metastases (p???0.05) and p53 expression (p???0.05). Clinical stage and histological grade were not associated with variation in NURR1 expression. In gene microarrays, 4 of 5 datasets showed stronger mean expression of NURR1 in normal breast as compared to transformed breast. Additionally, NURR1 expression was strongly correlated with increase relapse free survival (HR?=?0.7) in a cohort of all breast cancer patients, but showed no significant difference in survival when compared among patients whom have not been treated systemically (HR?=?0.91). Paradoxically, NURR1 silenced breast xenografts showed significantly decreased growth in comparison to control, underscoring a biphasic role for NURR1 in breast cancer progression.NURR1 function presents a dichotomy in breast cancer etiology, in which NURR1 expression is associated with normal breast epithelial differentiation and efficacy of systemic cancer therapy, but silencing of which attenuates tumor growth. This provides a strong rationale for the potential implementation of NURR1 as a pharmacologic target and biomarker for therapeutic efficacy in breast cancer.

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The orphan nuclear receptor Nurr1 restricts the proliferation of haematopoietic stem cells.

Publications

The orphan nuclear receptor Nurr1 restricts the proliferation of haematopoietic stem cells.

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