高濃度葡萄糖藉由水解磷酸脂促進前列腺癌細胞淋巴管生成因子

High Glucose Induces Vascular Endothelial Growth Factor-C through Lysophosphatidic Acid Signals in Human Prostate Cancer PC-3 Cells

楊雅然(Ya-Jan Yang)

指導教授 ： 張正琪

共同指導教授 ： 李心予(Hsinyu Lee)

國立臺灣大學/牙醫專業學院/口腔生物科學研究所/碩士(2015年)

https://doi.org/10.6342/NTU.2015.02753

摘要

前列腺癌 (prostate cancer) 是男性常見的癌症之一，在台灣男性癌症中死亡率排行第七位，常見病徵有淋巴和骨髓轉移等現象。而在第二型糖尿病患者中，經由臨床統計發現其具較高的罹癌機率，高血糖會促進有氧糖解，增進癌細胞生長速度，但目前的研究對於高血糖在前列腺癌的影響尚具爭議。水解磷酸脂 (Lysophosphatidic acid, LPA) 為細胞膜上衍生出的小分子傳訊脂質，由溶血磷脂醯膽鹼 (Lysophosphatidylcholine, LPC) 在自分泌運動因子 (Autotaxin, ATX) 酵素的作用下切除膽鹼而形成。已知LPA會和細胞膜上的水解磷酸脂受器 (LPA receptors)結合，促進癌細胞生長、移動和附著。在實驗室先前的研究中發現，在前列腺癌PC-3細胞株中，LPA可透過水解磷酸脂受器1 (LPA1) 和水解磷酸脂受器3 (LPA3) 促進淋巴管新生因子C型 (Vascular endothelial growth factor-C, VEGF-C) 的表現，進而影響癌症的淋巴轉移；此外，在糖尿病患者及老鼠中，也發現 ATX 的表現量增加。因此本實驗的目的探討在前列腺癌PC-3細胞株中，高濃度葡萄糖是否藉由水解磷酸脂訊號傳遞路徑促進有氧糖解和淋巴管新生因子C型的表現，導致前列腺癌的惡化。實驗結果顯示10 mM和20 mM的高濃度葡萄糖會增加VEGF-C 和ATX 的核醣核酸和蛋白質的表現。並透過抑制性藥物和基因敲除 (knockdown) 的實驗證實高濃度的葡萄糖確實透過ATX、LPA1/3、過氧化物 (Reactive oxygen species, ROS) 和晶狀體上皮源性生長因子 (Lens epithelium-derived growth factor, LEDGF) 的訊息傳遞路徑促進VEGF-C的表現。此外，我們也發現高濃度葡萄糖會增加鈣網蛋白 (Calreticulin, CRT) 的表現，並藉由基因knockdown的實驗證實CRT會調控ATX的表現。另一方面，由海馬生物能量測定儀結果顯示高濃度葡萄糖和LPA會提高有氧糖解的速率，反之，加入抑制LPA1/3藥物後有氧糖解速率下降。由這些結果證實，不正常的葡萄糖代謝會促進ATX的表現並增加LPA的含量，進而促進前列腺癌的淋巴管新生，造成前列腺癌病患的惡化。

關鍵字

水解磷酸脂 ； 自分泌運動因子 ； 前列腺癌 ； 有氧糖解 ； 淋巴管新生因子

並列摘要

Prostate cancer is one of the most frequently diagnosed cancers in males and usually metastasizes to various organs but particularly to local lymph nodes. Clinical evidences suggest that type II diabetes mellitus has been known to increase the risk of several cancers. Hyperglycemia would increase aerobic glycolysis and promote cancer growth, but the effects on prostate cancer are still controversial. Lysophosphatidic acid (LPA) is a small glycophospholipid that mediates multiple behaviors by activating LPA receptors in cancer cells, such as cell proliferation, migration and adhesion. In our previous studies, LPA could enhance VEGF-C expression through activating LPA receptor 1/3 in prostate cancer. On the other hand, autotaxin (ATX), an enzyme responsible for LPA synthesis, was up-regulated in diabetic patients and mice. In this study, we used PC-3 cell line as a model to investigate whether high glucose induced lymphangiogenesis and aerobic glycolysis through LPA signals to drive cancer progression. Our results demonstrated that the mRNA and protein expression levels of VEGF-C and ATX were increased after 10 mM and 20 mM high glucose treatments in PC-3 cells. By pharmacological blockers and knockdown experiments, we confirmed that the expression of VEGF-C was mediated through ATX, LPA1/3, ROS and LEDGF dependent pathways. Furthermore, the mRNA and protein levels of calreticulin (CRT) were up-regulated under high glucose conditions. By knockdown experiments, we demonstrated that ATX might be a downstream signal of CRT. On the other hand, high glucose and LPA treatments also enhanced the aerobic glycolysis. Taken together, these results suggested that the abnormal glucose metabolism might lead to LPA synthesis and therefore the subsequent pathological conditions of prostate cancer. These novel findings could potentially provide new strategies for prostate cancer treatments.

並列關鍵字

LPA ； prostate cancer ； aerobic glycolysis ； lymphangiogenesis ； VEGF-C

參考文獻

[1]American Diabetes, A. Standards of medical care in diabetes--2012. Diabetes Care 35 Suppl 1, S11-63, doi:10.2337/dc12-s011 (2012).

[2]Taylor, R. Insulin resistance and type 2 diabetes. Diabetes 61, 778-779, doi:10.2337/db12-0073 (2012).

[3]Habib, S. L. & Rojna, M. Diabetes and risk of cancer. ISRN Oncol 2013, 583786, doi:10.1155/2013/583786 (2013).

[4]Johnson, J. A. et al. Diabetes and cancer (1): evaluating the temporal relationship between type 2 diabetes and cancer incidence. Diabetologia 55, 1607-1618, doi:10.1007/s00125-012-2525-1 (2012).

[5]Vander Heiden, M. G., Cantley, L. C. & Thompson, C. B. Understanding the Warburg effect: the metabolic requirements of cell proliferation. Science 324, 1029-1033, doi:10.1126/science.1160809 (2009).