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

非典型畸胎样横纹肌样肿瘤（ATRT）是婴儿期和儿童期的肿瘤，其特征均为SMARCB 1（所有病例的95%）或SMARCA 4（所有病例的5%）缺失，两者均为SWI/SNF复合物（一种表观遗传重塑蛋白复合物）的组分。ATRT儿童的死亡率仍然很高，少数幸存者经常遭受长期的副作用。尽管这些肿瘤的遗传简单，但最近的研究发现了高度的表观遗传异质性：在甲基化水平上确定了三个亚组（命名为ATRT-TYR，ATRT-SHH，ATRT-MYC）。这些亚组之一ATRT-TYR显示黑素体标记基因的过表达。特别是MITF过表达，这是黑素瘤中众所周知的致癌基因。本文旨在描述MITF和共调节蛋白作为ATRT-TYR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生长。除此之外，我们将在ATRT细胞系中敲低MITF，并评估对肿瘤细胞转录组的影响。作为额外的体外步骤，我们将解开与MITF一起与DNA共结合的蛋白质。通过这一点，我们试图获得更多的见解MITF共调节蛋白，可能代表额外的治疗靶点。翻译这些体外研究结果，我们的目标是进行小鼠治疗研究，看看在ATRT异种移植模型中MITF抑制是否会导致生存益处。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其他治疗途径。

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.