Characterization of oncogenic FGFR3-TACC3 fusion gene in glioblastoma

描述(申请人提供)：融合基因是许多癌症中常见的染色体异常，在临床实践中可作为预后标志和药物靶点。通过使用全转录组测序，我们和其他人[1，2]在胶质母细胞瘤(GBM)中发现了FGFR3-TACC3融合，复发率高达8.3%。这种融合是由4p16.3上的串联复制事件引起的，促进了体外细胞的增殖和体内的肿瘤进展。融合基因在星形胶质细胞中的过度表达导致了细胞的非整倍体[1]，然而促进染色体异常分离的机制仍有待阐明。FGFR3-TACC3融合阳性细胞对MEK抑制剂U0126或PAN FGFR抑制剂PD173074有较高的敏感性，但对一线GBM化疗药物替莫唑胺(TMZ)的耐药性更强。因此，我们的研究确定了GBM中的一种新的基因改变，该改变至少对这种致命疾病的两个主要特征至关重要：基因组不稳定和对化疗的耐药性。最近的一份报告显示，FGFR3-TACC3融合也发生在膀胱癌中[3]。因此，这一新发现的基因事件的意义可能是广泛的。我们试图进一步鉴定这个新的癌基因FGFR3-TACC3。我们假设FGFR3-TACC3融合蛋白是一种关键的遗传变异，它显着改变了胶质瘤发生发展过程中的信号通路，导致了GBM的特征。我们计划通过进行实验来验证我们的假设，这些实验将确定融合中促进肿瘤发展的关键磷酸化位置和结构域，确定融合对替莫唑胺治疗耐药的分子机制，确定融合促进异常染色体分离的机制，最后确定当前药物抑制物在包含肿瘤的维甲酸融合中的疗效。我们将使用体外和体内两种方法来回答这些问题。

DESCRIPTION (provided by applicant): Fusion genes are common chromosomal aberrations in many cancers, and can be used as prognostic markers and drug targets in clinical practice. By using whole transcriptome sequencing, we and others [1, 2] have discovered FGFR3-TACC3 fusions in glioblastoma (GBM) at a recurrence rate of up to 8.3%. The fusion, caused by a tandem duplication event on 4p16.3, promoted cell proliferation in vitro and tumor progression in vivo. Overexpression of the fusion in astrocytes lead to cellular aneuploidy [1], however the mechanisms facilitating aberrant chromosomal segregation remain to be elucidated. FGFR3-TACC3 fusion positive cells exhibited higher sensitivity to the MEK inhibitor U0126 or pan FGFR inhibitor PD173074 but were more resistant to the frontline GBM chemotherapy drug, Temozolomide (TMZ). Thus, our studies have identified a novel genetic alteration in GBM that is critical for at least two major hallmarks of this deadly disease: genomic instability and resistanc to chemotherapy. A recent report showed that the FGFR3-TACC3 fusion also occurs in bladder cancer [3]. Thus, the significance of this newly recognized genetic event is likely broad. We seek to further characterize this novel FGFR3-TACC3 oncogene. We hypothesize that the FGFR3-TACC3 fusion protein is a key genetic aberration that significantly modifies the signaling pathways during glioma development and progression contributing to the hallmarks of GBM. We plan to test our hypothesis by performing experiments that will determine the critical phosphorylation sites and domains within the fusion that promote tumor development, to determine the molecular mechanisms by which the fusion is resistant to temozolomide treatment, to determine the mechanisms by which the fusion promotes abnormal chromosomal segregation, and finally to determine the efficacy of current pharmacological inhibitors in treatin fusion containing tumors. We will use both in vitro and in vivo approaches to answer these questions.