Validation of the transcription factor MITF and melanosomal protein expression as therapeutic targets in atypical teratoid rhabdoid tumors (ATRT)

非典型类畸胎瘤、横纹肌样肿瘤（ATRT）是发生在婴儿期和儿童期的肿瘤，其特征要么是SMARCB1缺失（占所有病例的95%），要么是SMARCA4缺失（占所有病例的5%），这两种肿瘤都是SWI/SNF复合物（一种表观遗传重塑蛋白复合物）的组成部分。ATRT儿童的死亡率仍然很高，少数幸存者往往遭受衰弱的长期副作用。因此，迫切需要新的治疗方法。尽管这些肿瘤的遗传简单性，但最近的研究发现了高度的表观遗传异质性：在甲基化水平上鉴定了三个亚组（命名为ATRT-TYR， ATRT-SHH, ATRT-MYC）。其中一个亚群，ATRT-TYR，显示过表达黑素体标记基因。特别是MITF过度表达，这是黑色素瘤中众所周知的致癌基因。本文旨在描述MITF和协同调节蛋白在ATRT-TYR中作为潜在药物靶点的适用性。我们将在细胞系中使用MITF抑制剂进行体外研究，以观察MITF下调是否会阻碍体外ATRT的生长。除此之外，我们将敲除ATRT细胞系中的MITF并评估其对肿瘤细胞转录组的影响。作为一个额外的体外步骤，我们将解开与MITF一起与DNA结合的蛋白质。通过这种方法，我们寻求对可能代表其他治疗靶点的MITF协调节蛋白获得更多的见解。翻译这些体外研究结果，我们的目标是进行小鼠治疗研究，看看MITF抑制在ATRT异种移植模型中是否会导致生存获益。总的来说，通过结合体外和体内治疗和敲除研究，我们将全面评估MITF抑制是否代表ATRT-TYR肿瘤的可行策略，从而寻求为这种致命疾病建立额外的治疗途径。

Atypical teratoid, rhabdoid tumors (ATRT) are tumors of infancy and childhood that are all characterized either by the loss of SMARCB1 (95% of all cases) or SMARCA4 (5% of all cases) both of which are components of the SWI/SNF complex, an epigenetic remodeling protein complex. Mortality of children with ATRT is still high and the few survivors often suffer from debilitating long-term side effects. New therapeutic approaches are therefore urgently needed.Despite the genetic simplicity of these tumors, recent studies have found a high degree of epigenetic heterogeneity: Three subgroups were identified at the methylation level (named ATRT-TYR, ATRT-SHH, ATRT-MYC). One of these subgroups, ATRT-TYR, displays overexpression of melanosomal marker genes. In particular MITF is overexpressed, a well known oncogene in melanoma. Here way aim to delineate the suitability of MITF and coregulated proteins as potential drug targets in ATRT-TYR. We will perform in vitro studies with MITF inhibitors in cell lines to see if MITF downregulation impedes ATRT growth in vitro. Beyond this, we will knock-down MITF in ATRT cell lines and assess the effect on the transcriptome of the tumor cells. As an additional in vitro step, we will unravel proteins that co-bind to the DNA together with MITF. By this we seek to gain additional insights into MITF coregulatory proteins that may represent additional therapeutic targets. Translating these in vitro findings we aim to perform mouse treatment studies to see if MITF inhibition in xenograft models of ATRT leads to a survival benefit. Overall, by combining in vitro and in vivo treatment and knock-down studies we will comprehensively evaluate if MITF inhibition represents a viable strategy for ATRT-TYR tumors and thus seek to establish additional therapeutic avenues for this deadly disease.