Synergism of telomere maintenance and telomerase with cancer-promoting signaling

描述（由申请人提供）：端粒酶是一种核糖核蛋白，已知可合成和维持染色体保护性端粒DNA，在几乎所有人类肿瘤中均上调。这项研究的目标是了解并最终在治疗上利用人类常见癌症的这一突出且功能重要的标志。端粒酶上调的水平与肿瘤分级相关：高度恶性的治疗抗性肿瘤细胞比低级别肿瘤具有更高的端粒酶水平。越来越多的证据表明，通过增加端粒酶赋予癌症和其他永生细胞的生长优势不仅是由于其端粒维持作用，而且还由于端粒酶与该作用无关的功能。因此，为了充分理解增加的端粒酶如何提高癌细胞的存活和增殖潜力，本提案的目的是：目的1：理解端粒酶如何与端粒相互作用以促进其维持，首先关注当端粒功能受损时端粒向细胞发出信号的性质;目的2：定义端粒酶选择性剪接异构体的特定独特功能。这些端粒酶功能中的一些不仅涉及完整端粒酶核糖核蛋白（RNP）的活性逆转录酶活性形式，而且还涉及端粒酶RNP的hTERT蛋白亚基的大量表达但表征不佳的逆转录酶活性B-剪接变体;目的3：从端粒酶可以起作用的额外机制中剖析端粒维持信号传导的机制，并了解它们对重要的细胞信号通路和过程（如生长和凋亡）的影响。因此，该提议的总体目标是检验以下假设：在癌症进展期间选择表征人类癌症的高水平端粒酶，这是由于端粒酶促进癌症的至少三个主要标志：端粒维持（永生）;激活侵袭和转移（癌症干细胞样性质;上皮向间充质转化）和逃避细胞死亡（抗凋亡）。最后，目标4将通过测试一种新的假设-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，来研究这些端粒酶/癌症驱动途径相互作用中的哪一个是杀死癌细胞的药物的关键。该研究将使用培养的人类癌细胞，通过实验操作和对其分子后果的调查，重点关注癌细胞内的机械过程。这项研究预计将产生抗癌疗法的新方法。

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.