STEM CELL SURVIVAL CLONAL ADAPTATION AND CARCINOGENESIS IN FANCONI ANEMIA

骨髓衰竭、骨髓增生异常(MDS)和急性髓系白血病(AML)是Fanconi贫血(FA)最常见的威胁生命的并发症。虽然造血疾病的发病和严重程度因病例而异，但几乎所有的互补组都发现了这种疾病，这表明每个野生型FA蛋白可能在造血细胞中具有特定的功能。我们实验室在过去资助期间开展的工作证实了FANCC蛋白的这一概念。这个项目的一个主要目的是验证这样的假设，即其他FA蛋白(即FANCA、FANCG和FANCD2)具有类似的多功能，并且除了与交联剂引起的损伤相关的功能外，还具有重要的生存功能。虽然有强有力的证据证明FANCC具有核功能， FANCC参与了一个可能促进DNA解离和修复的核复合体，我们发现FANCC也具有调节促凋亡信号分子(例如eIF2α激酶PKR和PERK)的激活状态的功能。因为FANCC抑制eIF2α激酶的能力是由其结合伴侣HSP70的能力决定的，所以我们 S，这一假设将得到验证：在目标1中，我们还发现，在对H_2O_2的响应中，FANCA和FANCC促进STAT3的激活，FANCG和FANCD2促进STAT5的激活。在目标2中，我们测试是否同样适用于由造血干细胞和祖细胞中的造血生长和存活因子诱导的STAT反应。我们也报道过， 在FA患者的骨髓中出现的肿瘤克隆已经获得了抵抗非肿瘤性FA细胞对凋亡信号敏感的能力。我们认为，这样的克隆是由体细胞突变适应性地产生的，这些突变要么绕过了FANCC依赖的STAT激活的要求，要么通过抑制elF2pha激酶(目标3)。基于这些 我们建议检验三个相关假设：(1)FANCC的辅助伴侣功能抑制促凋亡的eIF2α激酶的激活，需要完整的FANCA、FANCD2和FANCG(目标1)；(2)FANCC作为辅助伴侣功能促进STAT1、3和5分子的运输和激活，以响应生长和生存因素以及过氧化氢，并需要野生型FANCA和FANCG的存在(目标2)；(3)导致FA造血和上皮干细胞肿瘤克隆进化的体细胞突变正是那些克服非肿瘤FA细胞促凋亡状态的突变(Aim 3)。这个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.