Synergism of telomere maintenance and telomerase with cancer-promoting signaling

描述(申请人提供)：端粒酶，一种已知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上调。这项研究的目标是了解并最终在治疗上利用常见人类癌症的这一突出的和功能上重要的标志。端粒酶上调水平与肿瘤分级有关：高度恶性耐药肿瘤细胞的端粒酶水平高于低度恶性肿瘤。越来越多的证据表明，增加的端粒酶赋予癌细胞和其他不朽细胞的生长优势不仅是由于它的端粒维持作用，而且是因为端粒酶的功能(S)独立于这一作用。因此，为了充分了解增加的端粒酶如何提高癌细胞的存活和增殖潜力，本提案的目标1：了解端粒酶如何与端粒相互作用以促进其维持，首先集中在端粒功能受损时端粒向细胞发送信号的特性；目标2：定义端粒酶或剪接异构体的特定不同功能。其中一些端粒酶功能不仅涉及活性逆转录酶活性形式的完整的端粒酶核糖核蛋白(RNP)，而且还涉及端粒酶RNP的hTERT蛋白亚单位的b-剪接变异体，其表达丰富，但特性不佳；目的3：从端粒酶的其他作用机制中剖析端粒维持信号的机制，并了解它们对重要的细胞信号通路和过程的影响，如生长和凋亡。因此，这项建议的总体目标是测试这一假设，即在癌症进展过程中，由于端粒酶至少促进了癌症的三个主要特征：端粒维持(不朽)；激活侵袭和转移(癌症干细胞样特性；上皮向间充质转化)和逃避细胞死亡(抗凋亡)，从而选择了高水平的端粒酶。最后，Aim 4将通过测试一个新的假设--适度、短期的端粒酶下调使癌症干细胞对化疗敏感--来研究这些端粒酶/癌症驱动途径相互作用中的哪些是杀死癌细胞的药物的关键作用，并将探讨这一假设的机制基础。这项研究将利用培养的人类癌细胞，通过实验操作和研究它们的分子后果，专注于癌细胞内的机械过程。这项研究有望产生抗癌治疗的新方法。

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.