STEM CELL SURVIVAL CLONAL ADAPTATION AND CARCINOGENESIS IN FANCONI ANEMIA

骨髓衰竭、骨髓增生异常（MDS）和急性髓细胞性白血病（AML）是范可尼贫血（FA）最常见的危及生命的并发症。虽然造血系统疾病的发病和严重程度因情况而异，但几乎在所有互补组中都发现了它，这表明每个野生型FA蛋白可能在造血细胞中具有特定功能。在过去的资助期间，我们实验室进行的工作证实了FANCC蛋白的这一概念。该项目的一个主要目标是测试其他FA蛋白（即FANCA，FANCG和FANCD 2）具有类似的多功能性，并且具有重要的生存功能，超出了与交联剂诱导的损伤相关的功能。虽然有强有力的证据表明FANCC具有核功能， FANCC参与可能促进DNA解旋和修复的核复合物，我们发现FANCC还具有调节促凋亡信号分子（例如eIF2 α激酶PKR和PERK）的活化状态的功能。因为FANCC抑制eIF2 α激酶的能力是由其结合伴侣蛋白hsp70的能力决定的，我们 认为FANCC在正常细胞中起抗凋亡的分子伴侣作用。这一假设将在目标1中得到检验。我们还发现，响应于H2O2，FANCA和FANCC促进STAT3的激活，FANCG和FANCD 2促进STAT5的激活。在目标2中，我们测试了造血干细胞和祖细胞中的造血生长和生存因子诱导的STAT反应是否也同样如此。我们还报告说， 在FA患者骨髓中产生的肿瘤克隆获得了抵抗非肿瘤性FA细胞对其高度敏感的凋亡信号的能力。我们推断这样的克隆通过体细胞突变适应性地产生，所述体细胞突变绕过对FANCC依赖性STAT激活的需要或通过抑制eIF2 α激酶（目的3）。基于这些 根据这些观察，我们提出测试三个相关的假设：（1）FANCC的共伴侣蛋白功能抑制促凋亡eIF2 α激酶的活化，并且需要完整的FANCA、FANCD 2和FANCG（目的1），（2）FANCC作为共伴侣蛋白功能以促进STAT 1、3和5分子响应于生长和存活因子以及H2O2的运输和活化，并且需要野生型FANCA和FANCG的存在（目的2），以及（3）导致FA造血和上皮干细胞中的肿瘤性克隆进化的体细胞突变正是克服非肿瘤性FA细胞的促凋亡状态的那些体细胞突变（目的3）。本应用程序旨在测试这些假设。

Bone marrow failure, myetodysplasia (MDS), and acute myelogenous leukemia (AML) are the most prevalent life-threatening complications of Fanconi anemia (FA). While the onset and severity of hematopoietic disease varies from case to case, it is found in virtually all complementation groups, suggesting that each wild-type FA protein may have a specific function in hematopoietic cells. Work carried out in our laboratory during the past funding period has confirmed this notion for the FANCC protein. A major objective of this project is to test the hypothesis that other FA proteins (namely FANCA, FANCG, and FANCD2) are similarly multifunctional and have important survival functions beyond those linked with damage induced by cross-linking agents. While strong evidence exists for a nuclear function of FANCC, which participates in a nuclear complex that probably facilitates DNA unwinding and repair, we find that FANCC also functions to modulate the state of activation of pro-apoptotic signaling molecules (e.g. the eiF2alpha kinases PKR and PERK). Because the capacity of FANCC to Suppress eiF2alpha kinases is defined by its capacity to bind the chaperone hsp70, we believe that FANCC functions as an anti-apoptotic co,chaperone in norrnal cel!s, This hypothesis will be tested:in aim 1. We also discovered that in response to H2O2, FANCA and FANCC facilitate the activation of STAT3 and FANCG and FANCD2 facilitate activation of STAT5. In aim 2 we test whether the same will hold true for STAT responses induced by hematopoietic growth and survival factors in hematopoietic stem cells and progenitors. We have also reported that neoplastic clones arising in the marrow of FA patients have acquired the capacity to resist apoptotic cues to which non-neoplastic FA cells are hypersensitive. We reason that such clones arise adaptively by somatic mutations that either bypass a requirement for FANCC dependent STAT activation or by suppressing elF2alpha kinases (Aim 3). Based on these observations, we propose to test three related hypotheses:(1) the co-chaperone function of FANCC suppresses activation of pro-apoptotic eiF2alpha kinases and requires intact FANCA, FANCD2 and FANCG (Aim 1), (2) FANCC functions as a co-chaperone to facilitate traffic and activation of STAT 1, 3 and 5 molecules in response to growth and survival factors and to H2O2 and requires the presence of wild-type FANCA and FANCG (Aim 2), and (3) somatic mutations leading to neoplastic clonal evolution in FA hematopoietic and epithelial stem cells are precisely those that overcome the pro-apoptotic state of non-neoplastic FA cells (Aim 3). This application is designed to test these hypotheses.