Consequences and mechanism of aberrant splicing in African American prostate cancer disparities

总结 前列腺癌（PCa）风险和生存结局存在显著的人群（种族）差异， 目前的卫生统计数据。这在非裔美国人（AA）患者和欧洲人患者之间尤其明显 美国（EA）同行，其中AA表现出PCa发病率和死亡率高1.5至2倍的风险。我们 表明癌基因和肿瘤抑制基因发生差异性RNA剪接， 在AA的PCa标本与EA患者相比。差异剪接事件导致富集， 在许多情况下，在EA癌中未观察到AA特异性剪接变体的产生。我们克隆了 磷脂酰肌醇-4，5-二磷酸3-激酶催化亚基δ的AA和EA剪接变体cDNA （PIK 3CD）和成纤维细胞生长因子受体3（FGFR 3），并且异位地分别引入克隆 转化为前列腺癌细胞系。与EA突变体表达系相比，AA突变体表达系的遗传多样性更高， 在体外细胞增殖和侵袭测定中致癌，并表现出更大的肿瘤生长/转移， 在异种移植小鼠模型中对小分子靶向疗法的抗性。这些发现可以部分解释， 观察到AA人群相对于其他种族群体的癌症健康差异。机制 负责形成AA特异性或富集的mRNA剪接变体，假设是由于 AA PCa标本中6种关键剪接因子表达失调。我们把这种失调称为 AA特异性剪接变体的相关产生作为“PCa差异中的AA剪接因子编码”。 尽管取得了这些进展，但仍有一些问题没有得到解决。第一，什么是 6种剪接因子表达失调的机制？二、能否生产AA专用 通过外显子跳跃的剪接变异体是否直接归因于6种失调的剪接因子？最后， PIK 3CD和FGFR 3的AA特异性短变体的编码蛋白介导更致癌的细胞凋亡。 PCa细胞的表型？本申请的目的是解决这些问题，并提供一个 在选择性RNA剪接中与人群相关差异的机制框架，预计 促进未来可药物靶点的鉴定（例如剪接因子和/或产生的剪接变体蛋白） AA肿瘤表型和差异。

Summary There are striking population (race) disparities in prostate cancer (PCa) risk and survival outcome borne out of current health statistics. This is particularly evident between African American (AA) patients and their European American (EA) counterparts, where AAs exhibit a 1.5 to 2 fold higher risk of PCa incidence and mortality. We demonstrate that differential alternative RNA splicing takes place for oncogenes and tumor suppressor genes in PCa specimens of AA compared to EA patients. The differential splicing events result in the enrichment and in many instances generation of AA-specific splice variants not observed in EA cancers. We have cloned the AA and EA splice variant cDNAs for both phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit delta (PIK3CD) and fibroblast growth factor receptor 3 (FGFR3), and ectopically introduced the clones individually into PCa cell lines. Compared to the EA variant-expressing lines, the AA variant-expressing lines are more oncogenic in in vitro cell proliferation and invasion assays, and exhibit greater tumor growth/metastasis and resistance to small molecule targeted therapy in xenograft mouse models. These findings may explain, in part, the observed cancer health disparities in the AA population relative to other racial groups. The mechanism responsible for the formation of AA-specific or -enriched mRNA splice variants are hypothesized to be due to the dysregulated expression of 6 key splicing factor s in AA PCa specimens. We refer to this dysregulation and associated production of AA-specific splice variants as an “AA splicing factor code in PCa disparities.” Notwithstanding these developments, a number of questions remain unresolved. First, what is the mechanism(s) of dysregulated expression of the 6 splicing factors? Second, can the production of AA-specific splice variants via exon skipping be directly attributed to the 6 dysregulated splicing factors? Lastly, how do the encoded proteins of the AA-specific short variants of PIK3CD and FGFR3 mediate a more oncogenic phenotype in PCa cells? The objectives of this application are to address these questions, and to provide a mechanistic framework of population-related differences in alternative RNA splicing, which is anticipated to facilitate future identification of druggable targets (e.g. splicing factors and/or resulting splice variant proteins) of AA tumor phenotype and disparities.