Defining the Critical Function and Regulation of NNMT in Breast Cancer Progression and Metastasis

N-甲基转移酶(NNMT)是NAD+挽救途径中的一个关键酶，但功能尚不清楚。 在基底细胞样乳腺癌(BLBC)中高表达且特异。我们发现NNMT是稳健的 当BLBC细胞从基质中分离并在悬浮中生长时升高。NNMT淘汰赛(KO) 体外抑制非锚定生长，但也抑制动物肿瘤生长和转移 模特们。使用无偏CRISPR-Cas9文库筛选，我们鉴定FOXC1-CARM1复合体为 负责BLBC的NNMT上调工作。重要的是，通过KO或使用An抑制NNMT 抑制剂可增强化疗药物介导的促细胞凋亡作用。因此，我们假设NNMT是一个 维持BLBC进展和转移的NAD+动态平衡的关键门卫；这种动态平衡 增强细胞抗氧化防御机制，防止BLBC细胞遇到的ROS激增 在转移过程中。这项建议目的是(1)表征NNMT在调节NAD+中的功能 肿瘤进展和转移中的动态平衡；(2)NNMT的转录调控 以及(3)探讨NNMT作为预测预后的生物标志物和临床应用的价值。 BLBC的可下药目标。在强劲的初步数据的指导下，我们将通过追求三个方面来检验这一假设 具体目标：(1)确定NNMT在BLBC中的关键作用；(2)通过描述NNMT的转录 FOXC1-CARM1复合体；以及(3)明确NNMT在乳腺发育中的作用和 乳腺癌转移。我们的提议具有创新性和重大意义，因为NNMT代表着阿喀琉斯家族 BLBC的脚后跟；针对这种代谢脆弱性提供了一种有效的治疗选择 BLBC。

N-methyltransferase (NNMT), a key enzyme in the NAD+ salvage pathway with unclear functions, is expressed highly and specifically in basal-like breast cancer (BLBC). We found that NNMT is robustly elevated when BLBC cells detach from a matrix and grow in suspension. Knockout (KO) of NNMT not only inhibits anchorage-independent growth in vitro but also suppresses tumor growth and metastasis in animal models. Using an unbiased CRISPR-Cas9 library screening, we identified the FOXC1-CARM1 complex as being responsible for NNMT upregulation in BLBC. Importantly, inhibition of NNMT by either KO or use of an inhibitor increases the proapoptotic effects mediated by chemo-drugs. We thus hypothesize that NNMT is a critical gatekeeper that maintains NAD+ homeostasis for BLBC progression and metastasis; this homeostasis boosts the cellular antioxidative defense machinery, and prevents surges of ROS that BLBC cells encounter during metastasis. The objective of this proposal is to (1) characterize NNMT function in regulating NAD+ homeostasis in tumor progression and metastasis; (2) delineate the transcriptional regulation of NNMT by the FOXC1-CARM1 complex; and (3) explore the clinical value of NNMT as a prognostic biomarker and a druggable target for BLBC. Guided by strong preliminary data, we will test this hypothesis by pursuing three specific aims: (1) to determine the critical roles of NNMT in BLBC; (2) to delineate NNMT transcription by the FOXC1-CARM1 complex; and (3) to define the roles of NNMT in the development of mammary gland and breast cancer metastasis. Our proposal is innovative and significant, because NNMT represents the achilles heel of BLBC; targeting this metabolic vulnerability offers an effective therapeutic option against metastatic BLBC.