An investigation into YB-1 and its role in tumour progression in medulloblastoma.

髓母细胞瘤是儿童最常见的恶性脑肿瘤。肿瘤通常是扩散的；三分之一的髓母细胞瘤患者在确诊时表现为转移疾病，大多数患者在复发时表现为转移。虽然近年来平均年龄患者的长期存活率显著提高，但转移和复发疾病的高风险和极高风险患者的预后总是较差。显然，需要新的治疗方案来提高存活率，减少与当前治疗相关的终生认知和功能并发症。三磷酸腺苷结合盒(ABC)转运体在许多癌症中高度表达，在恶性肿瘤细胞中产生多药耐药。三磷酸腺苷结合盒B亚家族成员1(ABCB1)的表达与髓母细胞瘤的高危相关，并且已知可以外流目前用于髓母细胞瘤治疗方案的许多化疗药物。Y-box结合蛋白1(YB-1)是ABCB1基因的潜在调节因子。YB-1的核表达和ABCB1的表达在一些癌症中已经被证明是相关的，并且YB-1的缺失与ABCB1基因的活性降低有关。YB-1在许多肿瘤中也过度表达，核表达升高往往与预后不良有关。尽管在其他癌症中研究得很好，但对YB-1在髓母细胞瘤中的作用知之甚少。在这个项目的第一年，我研究了YB-1在髓母细胞瘤中的表达，发现YB-1在所有髓母细胞瘤亚型中都有mRNA和蛋白的表达。首次探索了YB-1髓母细胞瘤的细胞定位，并在第3、4组和Sonic Hedgehog(SHH)来源的一系列细胞系的核亚细胞室和细胞质亚细胞室中检测到YB-1和pYB-1(S102)。此外，化疗和ABCB1底物长春新碱处理可促进YB-1在SHH细胞系DAOY中的核定位。最后，利用染色质免疫沉淀(CHIP)分析，我们发现YB-1与ABCB1启动子中的一个倒置CCAAT框结合，这表明YB-1可能是髓母细胞瘤中ABCB1基因的一个新的调节因子。尽管还需要进一步的实验，但这些发现确定YB-1是进一步研究髓母细胞瘤耐药的一个引人注目的靶点。

Medulloblastoma is the most frequent malignant childhood brain tumour. Tumours commonlydisseminate; one-third of medulloblastoma cases display metastatic disease at diagnosis and themajority of patients exhibitmetastases at relapse.Whilst long term survival rates amongst averageriskpatients have significantly improved in recent years, outcome for high- and very high-riskpatients with metastatic and recurrent disease remains invariably poorer. Clearly, new treatmentoptions are required to improve survival rates and reduce the life-long cognitive and functionalcomplications associated with current therapies.ATP Binding Cassette (ABC) transporters are highly expressed in numerous cancers, where theyconfer multi-drug resistance in malignant cells. ATP binding cassette subfamily B member 1(ABCB1) expression correlates with high-risk medulloblastoma and is known to efflux a number ofchemotherapeutics currently used in medulloblastoma treatment protocols. Y-box binding protein1 (YB-1) represents a potential regulator of the ABCB1 gene. Correlation between YB-1 nuclearexpression and ABCB1 expression has been demonstrated in several cancers and depletion ofYB-1 is associated with reduced activity of the ABCB1 gene. YB-1 is also over-expressed innumerous cancers, with elevated nuclear expression frequently associated with poor prognosis.Although well researched in other cancers, very little is known about the role of YB-1 inmedulloblastoma. In the first year of this project, I have investigated YB-1 expression inmedulloblastoma and found YB-1 to be expressed at both mRNA and protein level in allmedulloblastoma subgroups. For the first time, cellular localisation of YB-1 inmedulloblastoma hasbeen explored and YB-1 and pYB-1(S102) detected in both nuclear and cytoplasmic subcellularcompartments in a range of Group 3, 4 and Sonic Hedgehog (SHH) derived cell lines. Further tothis, treatment with chemotherapeutic and ABCB1 substrate vincristine was found to promotenuclear localisation of YB-1 in SHH cell line DAOY. Finally, utilising chromatin immunoprecipitation(ChIP) analysis, we have shown that YB-1 binds to an inverted CCAAT box in the ABCB1 promoter,suggesting that YB-1 may represent a novel regulator of the ABCB1 gene in medulloblastoma.Although further experiments are required, these findings identify YB-1 as a compelling target forfurther research into drug resistance in medulloblastoma.