Cellular and Molecular mechanisms of ATRA inhibition of osteoblast-induced MDS development

摘要 成骨细胞是调节造血的造血干细胞(HSC)生态位的重要组成部分。 最近，它们已成为血液病髓系发育的关键调节因子。 恶性肿瘤。我们发现成骨细胞中-连环蛋白信号的一个单一激活突变是 足以导致MDS的发展，最终在小鼠中进展为AML。这种疾病是 可移植，在细胞遗传学水平上以克隆进化为特征。激活的-连环蛋白信号是 在38%的MDS患者的成骨细胞中存在，表明这一途径可能持续发育不良 人类的造血和向MDS和AML的进展。我们的初步观察支持这一迹象。 并进一步提出了一种治疗这一特殊人群的新方法。在寻找潜在的 FDA批准的一种化合物，具有抑制-连环蛋白的能力，我们遇到了全反式维甲酸 (ATRA)。ATRA用于治疗急性早幼粒细胞白血病，其作用机制依赖于 关于它将NCoR-HDACL复合体从RAR中分离出来并允许DNA转录和 未成熟白血病早幼粒细胞向成熟粒细胞的分化。然而，来自体外的报告 研究表明，全反式维甲酸还有另一个功能：它抑制-连环蛋白的功能。我们已经发现，抑制 14例成骨细胞-连环蛋白活性增高的MDS患者应用全反式维甲酸后-连环蛋白信号转导改善 血液学表型，稳定疾病状态和抑制-连环蛋白活性。它还治疗了MDS和 在成骨细胞中表达结构性活性-连环蛋白可防止MDS小鼠的疾病转化。基座 在这些观察的基础上，我们假设干扰mds小鼠成骨细胞的-catenin信号。 成骨细胞中-连环蛋白活性的模型和MDS患者的药物治疗 改善疾病结局。这可能是通过ATRA实现的，它可能会在特定的 部分骨髓增生异常综合征患者成骨细胞中活化的-连环蛋白的治疗。为了检验这一假说 我们将研究全反式维甲酸是否抑制-连环蛋白诱导的小鼠-连环蛋白激活的MDS。 成骨细胞；以及这种抑制是否独立于对HSCs的作用。我们还将剖析分子 全反式维甲酸抑制-连环蛋白的机制，并验证全反式维甲酸抑制的意义和特异性。 体外成骨细胞和异种移植中不同类型-连环蛋白激活的人MDS的细胞遗传学研究 我们开发的模型是为了研究人类MDS和基质细胞之间的相互作用。

ABSTRACT Osteoblasts are critical components of the hematopoietic stem cell (HSC) niche that regulate hematopoiesis. More recently, they have emerged as critical regulators of the development of hematological myeloid malignancies. We showed that a single activating mutation in -catenin signaling in osteoblasts is sufficient to lead to the development of MDS, eventuall progressing to AML in mice. The disease is transplantable and characterized by clonal evolution at the cytogenetic level. Activated -catenin signaling is present in osteoblasts of 38% of MDS patients suggesting that this pathway may sustain dysplastic hematopoiesis and progression to MDS and AML in humans. Our initial observations support this indication and further suggest a novel means for treating this particular population of patients. In search of a potential FDA-approved compound with the ability to inhibit -catenin signaling we came across all-trans-retinoic acid (ATRA). ATRA is used in the treatment of acute promyelocytic leukemia where its mechanism of action relies on its ability to dissociate the NCOR-HDACL complex from RAR and allow DNA transcription and differentiation of the immature leukemic promyelocytes into mature granulocytes. However, reports from in vitro studies indicate that ATRA has another function: it inhibits -catenin functions. We have found that inhibition of -catenin signaling in 14 MDS/ patients with active -catenin in their osteoblasts with ATRA improved their hematologic phenotype, stabilized disease status and inhibited -catenin activity. It also treated MDS and prevented disease transformation in MDS mice expressing constitutive active -catenin in osteoblasts. Based on these observations, we hypothesize that interrupting -catenin signaling in osteoblasts of MDS mouse models and MDS patients with active -catenin in their osteoblasts by pharmacological means will improve disease outcome. This may be achieved with ATRA, which may find a new use specifically in the treatment of the portion of MDS patients with activated -catenin in their osteoblasts. To test this hypothesis we will examine whether ATRA inhibits -catenin-induced MDS in mouse models of activated -catenin in osteoblasts; and whether this inhibition is independent of actions on HSCs. We will also dissect the molecular mechanism of -catenin inhibition by ATRA; and, verify the significance and specificity of ATRA inhibition in cytogenetically different types of human MDS with activated -catenin in osteoblasts in vitro and in xenograft models we developed to examine interactions between human MDS and stromal cells.