糖酵解在乳腺癌侵袭转移中的作用和干预研究

Invasion and metastasis is the major cause of death for breast cancer patients. Intervention of invasion and metastasis is the key step in breast cancer therapy. Cancer cells are different from normal cells in their metabolic properties. Normal cells mostly rely on mitochondrial oxidative phosphorylation for their growth. In contrast, cancer cells depend more on glycolysis, even in the presence of available oxygen. This altered energy dependency is known as the "Warburg effect". Although the cause-effect relationship between tumor development and increased glycolysis is controversial, increased glycolysis is a hallmark of cancer cells and has been well accepted as an important process to support cancer cell malignant phenotypes. Therefore, targeting glycolysis is a new strategy in cancer therapy. ErbB2 (also known as Her2 or neu) is an oncogene that is overexpressed in 20~25% of brease cancer cases and is correlated with a poor prognosis. It has been demonstrated that the overexpression of ErbB2 increases invasion and/or metastasis. Our previous reports demonstrated that ErbB2 upregulates lactate dehydrogenase A (LDHA) through heat shock factor 1(HSF1) leading to increased glycolysis in human breast cancer cells. This suggests that ErbB2-HSF1-LDHA is an important pathway to regulate glycolysis in breast cancer cells. However, the role of glycolysis in invasion and metastasis of breast cancer is unclear. We also found that Herceptin inhibits glycolysis via downregulation of HSF1 and LDHA in breast cancer cells. A recent study showed that Herceptin inhibits invasion of breast cancer cells. However, whether Herceptin can reverse invasion and metastasis via its glycolysis-inhibitory effect is unclear. Based on previous reports and our studies, we hypothesize that ErbB2 induces invasion and metastasis through increased glycolysis and targeting glycolysis can inhibit invasion and metastasis of breast cancer. To address these hypotheses, we will pursuit the following specifc aims. First we will study the role of glycolysis in invasion and metastasis of breast cancer including dependency of invasion and metastasis on glycolysis and the role of HSF1 in invasion and metastasis. Then we will investigate the effect of targeting glycolysis on invasion and metastasis and its mechanism. Finally, we will test whether combination of Herceptin and glycolysis inhibitors will better reverse invasion and metastasis. Successful completion of this project will provide an understanding of the impact of ErbB2-increased glycolysis on invasion and metastasis of breast cancer and will substantially augment our knowledge of the molecular mechanism of invasion and metastasis. Furthermore, new sights into the unique ErbB2-mediated glycolysis in breast cancer cells that result from this project may lead to a more effective targeted cancer therapy for treating ErbB2-overexpressing cancers.

侵袭转移是导致乳腺癌患者死亡的主要原因，阻止其侵袭转移是乳腺癌治疗中的关键环节。糖酵解增强是恶性肿瘤细胞的一个显著特征且在肿瘤的恶性表型中起重要作用，干预糖酵解是靶向治疗肿瘤的新方向和发展趋势。我们的前期研究结果证实ErbB2通过热休克因子1(heat shock factor 1, HSF1)上调乳酸脱氢酶A (lactate dehydrogenase A, LDHA)，最终增强糖酵解，即ErbB2-HSF1-LDHA是乳腺癌细胞中调节糖酵解的一条重要通路，但是糖酵解在乳腺癌侵袭转移中的作用还不清楚。我们预测ErbB2通过增强糖酵解介导乳腺癌的侵袭转移，干预糖酵解能抑制此作用。为此，我们首先需要明确糖酵解在乳腺癌侵袭转移中的作用; 其次研究干预糖酵解对乳腺癌侵袭转移的抑制作用及其分子机制。本项目对乳腺癌侵袭转移分子机制的探讨和干预具有重要意义，有望为乳腺癌的治疗提供新思路和新靶点。

转移是导致乳腺癌患者死亡的主要原因，但乳腺癌转移的分子机制还不完全清楚。瓦伯格效应即糖酵解增强是恶性肿瘤细胞的一个标志，干预糖酵解是靶向治疗肿瘤的新方向。曲妥珠单抗(trastuzumab,商品名赫赛汀，Herceptin)是一种针对癌细胞ErbB2的人源化单克隆抗体，在临床上主要用于治疗ErbB2阳性的乳腺癌和其它癌症。但Herceptin抗癌的分子机制还未完全阐明。我们的前期研究结果证实ErbB2通过热休克因子1(heat shock factor 1, HSF1)上调乳酸脱氢酶A (lactate dehydrogenase A, LDHA)，最终增强糖酵解，即ErbB2-HSF1-LDHA是乳腺癌细胞中调节糖酵解的一条重要通路，但是糖酵解在乳腺癌侵袭转移中的作用还不清楚。我们还发现，Herceptin可以抑制乳腺癌细胞的糖酵解，有报道Herceptin能抑制乳腺癌细胞的侵袭，但抑制糖酵解是否是Herceptin抑制侵袭的分子机制有待研究。在本项目中，我们首先构建了ErbB2高表达的乳腺癌细胞MCF7/ErbB2，研究了乳腺癌细胞的迁移侵袭对糖酵解的依赖性和干预糖酵解能否部分逆转乳腺癌的迁移侵袭，证实了ErbB2、FASN介导的糖酵解，ErbB2-HSF1-LDHA通路在乳腺癌细胞的迁移侵袭中起重要作用，即ErbB2高表达细胞的迁移侵袭依赖于糖酵解，糖酵解抑制剂2-脱氧葡萄糖(2-deoxyglucose, 2-DG)和草酸盐（oxamate,OX）及脂肪酸合酶抑制剂浅蓝菌素（Cerulenin, Cer）能部分逆转迁移侵袭。其次，我们研究了干预糖酵解对乳腺癌细胞迁移侵袭的抑制作用及其分子机制，揭示了Herceptin抗癌的新机制：通过下调HSF1和LDHA而抑制ErbB2-HSF1-LDHA通路介导的糖酵解，最终抑制ErbB2高表达乳腺癌细胞的迁移侵袭；Herceptin与糖酵解抑制剂（2-DG/OX）的联用能更有效地抑制糖酵解从而协同抑制乳腺癌细胞的迁移侵袭。这些研究结果使我们从代谢角度对乳腺癌转移的分子机制有了更进一步的认识，为ErbB2高表达乳腺癌患者的临床治疗提供了新靶点和新思路。