Synergism of telomere maintenance and telomerase with cancer-promoting signaling

描述（由申请人提供）：端粒酶，一种已知用于合成和维持染色体保护端粒DNA的核糖核蛋白，在几乎所有人类肿瘤中都上调。这项研究的目标是理解，并最终在治疗上利用这一常见人类癌症的突出和功能上的重要标志。端粒酶水平上调与肿瘤分级相关：高度恶性耐药肿瘤细胞的端粒酶水平高于低分级肿瘤细胞。越来越多的证据表明，端粒酶的增加赋予癌症和其他不朽细胞的生长优势，不仅是因为端粒酶的端粒维持作用，还因为端粒酶的功能与端粒酶的作用无关。因此，为了充分了解端粒酶增加如何提高癌细胞的生存和增殖潜力，本研究的目标是：了解端粒酶如何与端粒相互作用以促进其维持，首先关注端粒功能受损时端粒的哪些特性向细胞发出信号；目的2：定义端粒酶选择性剪接异构体的特定不同功能。这些端粒酶的一些功能不仅涉及全端粒酶核糖核蛋白（RNP）的活性逆转录能力形式，而且还涉及端粒酶RNP的hTERT蛋白亚基的大量表达，但特征不佳，逆转录能力不足的b-剪接变体；目的3：从端粒酶作用的其他机制剖析端粒维持信号的机制，并了解它们对重要细胞信号通路和过程（如生长和凋亡）的影响。因此，本提案的总体目标是验证这样一种假设，即在癌症进展过程中，由于端粒酶促进了至少三个癌症的主要标志，端粒酶的高水平是人类癌症特征的选择：端粒维持（不朽）；激活侵袭和转移（癌干样特性；上皮细胞向间充质细胞转化），逃避细胞死亡（抗凋亡）。最后，Aim 4将研究端粒酶/癌症驱动途径的哪些相互作用是杀死癌细胞的药物的关键作用，通过测试一个新的假设-端粒酶的适度，短期敲低使癌症干细胞样细胞对化疗敏感-并将研究其机制基础。这项研究将利用培养的人类癌细胞，通过实验操作和对其分子后果的研究，专注于癌细胞内部的机制过程。这项研究有望为抗癌治疗提供新的途径。

DESCRIPTION (provided by applicant): Telomerase, the ribonucleoprotein known to synthesize and maintain chromosome-protective telomeric DNA, is upregulated in nearly all human tumors. The goal of this research is to understand, and ultimately to exploit therapeutically, this prominent and functionally important hallmark of common human cancers. The level of telomerase upregulation is correlated with tumor grade: highly malignant therapy-resistant tumor cells have higher telomerase levels than lower grade tumors. Increasing evidence suggests that the growth advantage conferred to cancer and other immortal cells by increased telomerase is due not only to its telomere maintenance role but also to function(s) of telomerase separate from this role. Therefore, to fully understand how increased telomerase elevates the survival and proliferative potential of cancer cells, the objective of this proposal i to Aim 1: understand how telomerase interacts with telomeres to promote their maintenance, focusing first on what properties of telomeres signal to cells when telomere function is compromised; Aim 2: define the specific distinct functions of telomerase alternatively spliced isoforms. Some of these telomerase functions involve not only the active reverse transcriptase-competent form of the full telomerase ribonucleoprotein (RNP), but also the abundantly expressed, yet poorly characterized, reverse transcriptase-incompetent b- splice variant of the hTERT protein subunit of the telomerase RNP; Aim 3: dissect the mechanisms of telomere maintenance signaling from the additional mechanisms through which telomerase can act, and understand their impact on important cellular signaling pathways and processes such as growth and apoptosis. Thus, the overall goal of this proposal is to test the hypothesis that the high leve of telomerase characterizing human cancer is selected during cancer progression due to the promotion by telomerase of at least three of the primary hallmarks of cancer: telomere maintenance (immortality); activating invasion and metastasis (cancer stem-like properties; epithelial to mesenchymal transition), and evasion of cell death (anti-apoptotic). Finally, Aim 4 will investigate which of these telomerase/cancer-driver pathway interactions are the critical ones for drugs that kill cancer cells, by testing a novel hypothesis - that moderate, short-term knock- down of telomerase sensitizes cancer stem-like cells to chemotherapy - and will investigate the mechanistic basis of this. The research will use cultured human cancer cells to focus on mechanistic processes within cancer cells, by experimental manipulations and investigations of their molecular consequences. This research is anticipated to generate new approaches for anti-cancer therapies.