PPP2R2A tumor suppression haploinsufficiency in prostate cancer

前列腺癌中的 PPP2R2A 肿瘤抑制单倍体不足

• 批准号: 9307124
• 负责人: Xavier Grana
• 金额: $ 7.93万
• 依托单位: TEMPLE UNIV OF THE COMMONWEALTH
• 依托单位国家: 美国
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-08-14 至 2019-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9307124
• 关键词: AKT1 gene; Affect; Alpha Cell; Architecture; Binding; Biological; Biological Assay; Biological Process; Cell Cycle; Cell Cycle Arrest; Cell Death; Cell Differentiation process; Cell Line; Cells; Cellular Spheroids; Collection; Complex; Critical Pathways; Cultured Cells; DNA biosynthesis; DU145; Data; Defect; Development; Disease-Free Survival; Down-Regulation; Ectopic Expression; Environment; Epithelial; Epithelial Cells; Exhibits; Fibroblasts; Frequencies; Gene Family; Genes; Growth; Holoenzymes; Human; Immunocompromised Host; Invaded; Ions; Link; Malignant Neoplasms; Malignant neoplasm of prostate; Mediating; Membrane; Mitotic; Modeling; Molecular; Mus; Normal Cell; Oncogenes; Organoids; Ovarian; PC3 cell line; PI3K/AKT; Pathway interactions; Patients; Pharmaceutical Preparations; Pharmacology; Phenothiazines; Phosphoric Monoester Hydrolases; Phosphorylation; Play; Preclinical Drug Evaluation; Property; Prostate; Prostatic Neoplasms; Protein Dephosphorylation; Protein Phosphatase 2A Regulatory Subunit PR53; Proteins; Proto-Oncogene Proteins c-akt; Retinoblastoma Protein; SCID Mice; Sampling; Signal Transduction; Structure; Substrate Specificity; Suggestion; Suppressor Genes; Testing; The Cancer Genome Atlas; Therapeutic; Toxic effect; Tumor Suppression; Tumor Suppressor Genes; Tumor Suppressor Proteins; Tumorigenicity; Up-Regulation; Work; cyclin B1; loss of function; mRNA Expression; malignant breast neoplasm; matrigel; monolayer; negative affect; neoplastic cell; new therapeutic target; novel; reconstitution; three dimensional cell culture; tumor; tumor growth

The PPP2R2A gene encodes B55α, a B regulatory subunit of PP2A, which is found hemizygously deleted at high frequency in prostate, ovarian and luminal B breast cancer. PP2A is a Ser/Thr phosphatase that consists of a collection of trimeric holoenzymes whose substrate specificity, and thus biological function, is determined by the regulatory B subunit. There are at least fourteen known genes encoding different B subunits belonging to four unrelated gene families. While it is well known that PP2A plays a key tumor suppressor function, which inhibition is required for transformation of a variety of human normal epithelial cells and fibroblasts in cooperation with defined sets of oncogenes and inactivated tumor suppressor genes, the actual holoenzymes implicated are not well understood. Data from TCGA and others shows that PPP2R2A is deleted in the majority of prostate tumors (>50% hemizygous/~7% homozygous loss). Importantly, PPP2R2A hemizygous loss correlates with its reduced mRNA expression. Moreover, PCa patients present reduced disease free survival with this alteration. While this has led to the suggestion that PPP2R2A is a tumor suppressor, there is not data supporting that loss of this gene contributes to PCa. We have found that limited ectopic expression of B55α in PCa cell lines, which naturally express lower levels than normal prostate epithelial cells and other PCa cell lines, results in dramatic toxicity. This toxicity is linked to mitotic arrest, euploidy, cell death, and potent tumor growth inhibition in SCID mice. Our preliminary studies also show growth inhibition and architecture defects in PCa and DU145 3D organoids following inducible upregulation of B55α. Moreover, treatment of PC3 cells with phenothiazines, which bind and activate PP2A, mimic cell cycle effects seen with B55α reconstitution. We hypothesize that PPP2R2A hemizygous deletion and/or other alterations that reduce B55α expression in PrECs promote transformation and tumorigenicity and restoring B55α/PP2A activity has therapeutic potential. To test this hypothesis we propose two aims: (1). To determine the transforming potential and tumorigenicity of B55α loss/downregulation in Prostate Epithelial Cells (PrECs) and PCa cell lines and the effect of reconstitution of B55α expression in their ability to differentiate, grow and/or invade when grown as 3D organoids. (2). To determine if the growth suppressor function of B55α in 3D organoids is associated with its mitotic functions and/or the result of alterations in survival/differentiation pathways and if it can be targeted with PP2A activating drugs. Successful completion of this work will support the feasibility of multiple studies aimed at understanding (a) oncogene/tumor suppressor gene cooperativity in prostate tumor development in mice, and its correlation in human tumors; (b) signaling mechanisms and identification of key target substrates; and importantly, (c) devising strategies to therapeutically upregulate this holoenzyme in tumor cells. Because PPP2R2A alterations occur at high frequency in prostate tumors, the proposed studies will lay the molecular and biological framework for the development of novel classes of PP2A drugs that could potentially help treat the large pool of PCa patients with hemizygous deletions on PPP2R2A.

PPP2R2A基因编码B55α，这是PP2A的B调节亚基，被发现是半合子缺失的 在前列腺癌、卵巢癌和B腔乳腺癌中高发。PP2A是一种丝氨酸/苏氨酸磷酸酶， 由三聚体全酶的集合组成，其底物专一性，从而生物学功能是 由调节B亚基决定。至少有14个已知基因编码不同的B亚基 属于四个不相关的基因家族。虽然众所周知，PP2A是一种关键的肿瘤抑制因子 功能，抑制多种人类正常上皮细胞的转化和 成纤维细胞与确定的癌基因和失活的肿瘤抑制基因协同作用，实际 所涉及的全酶还不是很清楚。来自TCGA等人的数据显示，PPP2R2A被删除 在大多数前列腺肿瘤中(&gt；50%半合子/~7%纯合子丢失)。重要的是，PPP2R2A 半合子缺失与其基因表达降低有关。此外，目前的PCA患者减少了 通过这种改变可以无病存活。虽然这导致了PPP2R2A是一种肿瘤的说法 抑制者，没有数据支持该基因的缺失导致前列腺癌。我们发现这是有限的 B55α在前列腺癌细胞系中的异位表达，其表达水平自然低于正常前列腺 上皮细胞和其他前列腺癌细胞系，导致显著的毒性。这种毒性与有丝分裂停滞有关， SCID小鼠的整倍体、细胞死亡和有效的肿瘤生长抑制。我们的初步研究还表明 Pca和DU145 3D有机物诱导表达上调后的生长抑制和结构缺陷 B55α。此外，用结合并激活PP2A的吩噻嗪处理PC3细胞，模拟细胞周期 B55α重建的影响。我们假设PPP2R2A半合子缺失和/或其他 降低前EC中B55α表达的改变促进转化、致瘤和修复 B55α/PP2A活性具有治疗潜力。为了验证这一假设，我们提出了两个目标：(1)。要确定 B55α缺失/下调在前列腺上皮细胞中的转化潜能和致瘤性 和PCa细胞系及重组B55α表达对其分化、生长能力的影响 和/或当生长为3D有机体时入侵。(2)。确定B55α在3D中是否具有生长抑制功能 有机化合物与其有丝分裂功能和/或存活/分化的改变有关。 以及它是否可以被PP2A激活药物靶向。这项工作的成功完成将支持 旨在了解(A)癌基因/抑癌基因协同作用的多项研究的可行性。 小鼠前列腺癌的发展及其在人类肿瘤中的相关性；(B)信号机制和 确定关键的靶标底物；以及重要的是，(C)制定治疗上上调这一目标的策略 肿瘤细胞中的全酶。由于PPP2R2A改变在前列腺癌中发生的频率很高，因此 拟议的研究将为PP2A新类别的开发奠定分子和生物学框架 可能有助于治疗大量PPP2R2A基因缺失的前列腺癌患者的药物。