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commonlydisseminate;三分之一的髓母细胞瘤病例在诊断时表现为转移性疾病，大多数患者在复发时表现为转移性疾病。虽然近年来平均风险患者的长期生存率显著提高，但转移性和复发性疾病的高风险和极高风险患者的预后仍然很差。显然，需要新的治疗方案来提高生存率，减少与当前治疗相关的终身认知和功能并发症。ATP结合盒（ABC）转运蛋白在许多癌症中高度表达，它们赋予恶性细胞多药耐药性。ATP结合盒亚家族B成员1（ABCB1）的表达与高危髓母细胞瘤相关，并且已知在目前髓母细胞瘤治疗方案中使用的许多化疗药物中有外排作用。Y-box结合蛋白1 （YB-1）是ABCB1基因的潜在调节因子。YB-1核表达与ABCB1表达之间的相关性已在几种癌症中得到证实，YB-1的缺失与ABCB1基因活性的降低有关。YB-1在许多癌症中也过表达，核表达升高通常与预后不良有关。尽管在其他癌症中有很好的研究，但对YB-1髓母细胞瘤的作用知之甚少。在这个项目的第一年，我研究了YB-1在成神经管细胞瘤中的表达，发现YB-1在所有成神经管细胞瘤亚组中mRNA和蛋白水平都有表达。研究人员首次探索了YB-1髓母细胞瘤的细胞定位，并在一系列第3、4组和Sonic Hedgehog （SHH）衍生细胞系的细胞核和细胞质亚细胞区室中检测到YB-1和pYB-1（S102）。此外，研究发现化疗和ABCB1底物长春新碱治疗可促进SHH细胞系day中YB-1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启动子中一个倒置的CCAAT盒子结合，这表明YB-1可能代表了成神经管细胞瘤中ABCB1基因的一种新的调节因子。虽然需要进一步的实验，但这些发现确定了YB-1是髓母细胞瘤耐药进一步研究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.