Identification and targeting of pathways separating healthy stem cell aging from malignant transformation

摘要 骨髓增生异常综合征(MDS)和急性髓系白血病(AML)通常是无法治愈的血液病 起源于异常的造血干细胞(HSCs)的恶性肿瘤。这些疾病主要发生在 老年人，在此之前有一个通常不被认识到的癌前阶段，这种阶段可以持续数年，并有明显的特点 通过一个逐渐变化的HSC隔间。这种在分子和功能上发散的干细胞，称为 白血病前干细胞(Pre-LSCs)具有较高的恶变倾向。 将健康衰老过程与癌症进化分开的机制尚未完全解决。这一差距 据我们所知，髓系恶性肿瘤的治疗方法的发展是一个巨大的挑战 在过去的几十年里，这种疾病的治愈率大多保持在30%以下。 我们的研究将探讨伴侣介导的自噬(CMA)的作用，CMA是一种高度选择性的亚型 自噬，到目前为止还没有在造血系统中有系统的特征。与…相反 宏自噬，CMA专门降解含有定义的识别基序的蛋白质(“KFERQ”，和 变异体)，并在慢性应激和衰老过程中保持多种细胞类型的完整性和正常功能。CMA 在一些与年龄相关的病理中下降并起关键作用，但它在白血病发生和发展中的作用 癌症干细胞的进化是未知的。利用新的遗传小鼠模型，我们已经获得了令人兴奋的初步结果 数据表明，CMA维持了健康的HSCs的功能。此外，我们还发现，精神障碍 CMA增强了LSC前功能，这似乎与活性氧水平的增加有关， 积聚在缺乏CMA的干细胞中。在这项研究中，我们假设CMA对干细胞具有保护作用 功能障碍和恶变。 我们将利用由遗传小鼠模型、人类细胞系和原代细胞组成的互补模型集 患者来源的细胞用于研究(1)健康的HSCs和LSCs前期的CMA激活模式(利用 CMA报告鼠和慢病毒CMA生物传感器)，(2)分子和(3)功能 CMA失活和刺激的后果。我们还将测试一种新的化学CMA激活剂工具 促进健康的HSCs和损害前LSCs的功效，可进一步开发用于 临床应用。 我们的研究将提供新的见解，揭示一种在衰老和诱因成人过程中衰退的分子机制 组织特异性干细胞向恶性转化，这将对 针对髓系恶性肿瘤的靶向自噬的新治疗策略的开发，可能还有其他 干细胞衍生的癌症。

ABSTRACT Myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML) are generally incurable hematologic malignancies, originating from aberrant hematopoietic stem cells (HSCs). These diseases occur mainly in the elderly and are preceded by an often-unrecognized precancerous phase, which can last for years and is hallmarked by a progressively changing HSC compartment. Such molecularly and functionally diverging stem cells, termed pre-leukemic stem cells (pre-LSCs), harbor a higher propensity to undergo malignant transformation. Mechanisms that separate the healthy aging process from cancer evolution are incompletely resolved. This gap in our knowledge poses a significant challenge for the development of curative therapies for myeloid malignancies for which cure rates have mostly remained below 30% over the last decades. Our study will investigate the role of chaperone-mediated autophagy (CMA), a highly selective subtype of autophagy, which has not been systematically characterized in the hematopoietic system thus far. Contrary to macroautophagy, CMA specifically degrades proteins containing defined recognition motifs (“KFERQ”, and variants), and maintains integrity and proper function of many cell types during chronic stress and aging. CMA declines in and critically contributes to several age-associated pathologies, yet its role in leukemogenesis and cancer stem cell evolution is unknown. Using new genetic mouse models, we have obtained exciting preliminary data demonstrating that CMA sustains the function of healthy HSCs. Furthermore, we found that impairment of CMA increased pre-LSC function that appears to be linked with increased levels of reactive oxygen species, accumulating in CMA-deficient stem cells. For this study, we hypothesize that CMA protects against stem cell dysfunction and malignant transformation. We will utilize a complementary model set consisting of genetic mouse models, human cell lines and primary patient-derived cells for the study of (1) CMA activation patterns in healthy HSCs and pre-LSCs (leveraging a CMA reporter mouse and lentiviral CMA biosensors for primary human cells), (2) molecular and (3) functional consequences of CMA inactivation and stimulation. We will also test a new chemical CMA activator tool compound for its efficacy to promote healthy HSCs and impair pre-LSCs, which could be further developed for clinical use. Our study will provide new insights into a molecular mechanism declining during aging and predisposing adult tissue-specific stem cells to malignant transformation, which will have important implications for the development of new therapeutic strategies for targeting autophagy in myeloid malignancies, and possibly other stem cell-derived cancers.