Elucidating the Mechanisms by which Hexokinase 2 Regulates Breast Cancer Metastasis

项目摘要： 尽管乳腺癌治疗有了很大的改进，但化疗的毒副作用仍然是一个主要的问题。 因此，有必要开发特异性靶向癌细胞的新的治疗策略， 而不伤害健康细胞。癌细胞的一个标志是"瓦尔堡效应"， 在氧气存在下表现出加速的葡萄糖代谢。己糖激酶催化第一个承诺 通过将葡萄糖磷酸化为葡萄糖-6-磷酸从而捕获葡萄糖的葡萄糖代谢步骤 在细胞中用于各种下游途径。以前的研究表明，虽然正常 乳腺细胞不表达己糖激酶2（HK2）亚型，但在乳腺癌中高度过表达。 癌细胞，这在一定程度上是导致原发性肿瘤中葡萄糖利用加速的原因。HK2 缺失在体外和体内抑制癌细胞的致瘤性。更重要的是，系统删除 肿瘤发生后的HK2抑制小鼠中的肿瘤发展而没有任何不良生理后果 癌症模型。具体而言，HK1表达水平足以维持正常细胞功能，但癌细胞的表达水平与正常细胞功能无关。 细胞不能克服HK2的丢失。因此，HK 2似乎是治疗性的良好的潜在靶点。 治疗原发性乳腺癌肿瘤。然而，转移是乳腺癌高死亡率的原因 这使得阐明HK2在乳腺癌转移中的作用更加重要。事实上， 初步结果显示在乳腺癌小鼠模型中肿瘤发作后HK2的系统性缺失 转移深刻地抑制了转移。拟议的研究计划将有助于阐明具体的 HK2在乳腺癌转移中的作用的机制。HK 2表达水平显着影响 上皮间质转化（EMT）蛋白表达水平，特别是重要的转录 蜗牛因子此外，HK2作为支架促进磷酸化和随后的失活 糖原合成酶激酶3（GSK 3 β）。SNAIL被GSK3 β磷酸化，从而导致 蜗牛的降解SNAIL还受O-GlcNAc修饰的调节，这有助于稳定蛋白质 通过抑制其GSK 3 β磷酸化介导的降解来降低其水平。目的1将研究其机制 HK2在EMT监管中的作用。此外，乳腺癌细胞可能上调HK2以对抗 在转移过程中出现的能量压力增加。研究表明，抗氧化剂可以 增强各种癌症的转移潜力。HK 2的上调可增加代谢物通量 通过戊糖磷酸途径的NADPH，从而允许细胞再循环抗氧化剂，如 glutatharone。目的2将确定HK2在细胞内活性氧水平中的作用， 乳腺癌转移总体而言，本研究采用了一种综合方法来阐明机制 HK2在乳腺癌转移中的作用，因此将提供一个新的潜在的治疗靶点。

Project Summary: Despite large improvements in breast cancer therapy, toxic side effects from chemotherapy are a major limitation; thus, it is necessary to develop novel therapeutic strategies that specifically target cancer cells while sparing healthy cells. One hallmark of cancer cells is the “Warburg Effect,” a phenomenon where cancer cells exhibit accelerated glucose metabolism in the presence of oxygen. Hexokinase catalyzes the first committed step in glucose metabolism by phosphorylating glucose to glucose-6-phosphate and thereby trapping glucose in the cell to be used in various downstream pathways. Previous research has demonstrated that while normal mammary gland cells do not express the hexokinase 2 (HK2) isoform, it is highly overexpressed in breast cancer cells, which, in part, is responsible for the accelerated glucose utilization in primary tumors. HK2 deletion inhibits the tumorigenicity of cancer cells in vitro and in vivo. More importantly, systemic deletion of HK2 after tumor onset inhibits tumor development without any adverse physiological consequences in mouse models of cancer. Specifically, HK1 expression levels are sufficient for normal cellular function, but the cancer cells cannot overcome the loss of HK2. As a result, HK2 appears to be a good potential target for therapeutic treatment of primary breast cancer tumors. However, metastasis accounts for the high mortality rate in breast cancer, which makes it more important to elucidate the role HK2 has in breast cancer metastasis. In fact, preliminary results showing that systemic deletion of HK2 after tumor onset in a mouse model of breast cancer metastasis profoundly inhibits metastasis. The proposed research plan will help elucidate the specific mechanism(s) for HK2's role in breast cancer metastasis. The level of HK2 expression dramatically affects to the level of epithelial mesenchymal transition (EMT) protein expression, specifically the important transcription factor SNAIL. In addition, HK2 acts as scaffold to promote the phosphorylation and subsequent inactivation Glycogen Synthase Kinase 3 (GSK3β). SNAIL is phosphorylated by GSK3β, which it turn leads to the degradation of SNAIL. SNAIL is also regulated by O-GlcNAc modification, which helps to stabilize the protein level by suppressing its GSK3β phosphorylation-mediated degradation. Aim 1 will investigate the mechanism for HK2's role in EMT regulation. Furthermore, it is possible that breast cancer cells upregulate HK2 to combat the increased energetic stress that occurs during metastasis. Research has shown that anti-oxidants can enhance the metastatic potential in various cancers. The upregulation of HK2 can increase metabolite flux through the pentose phosphate pathway for NADPH, thereby allowing cells to recycle anti-oxidants, such as gluthathione. Aim 2 will determine HK2's role in intracellular levels of reactive oxygen species in relation to breast cancer metastasis. Overall, this study utilizes a comprehensive approach to elucidate the mechanism(s) for HK2's role in breast cancer metastasis and as a result will provide a new potential therapeutic target.