脂氧合酶对胰腺癌细胞增殖和凋亡的调节作用

目的观察5-脂氧合酶（LOX）及12-LOX在人胰腺癌中的表达，并初步探讨LOX的作用底物——多不饱和脂肪酸（PUFA）及LOX抑制剂对胰腺癌细胞增殖及凋亡的调节作用。方法用免疫组织（细胞）化学、逆转录聚合酶链反应（RT—PCR）方法研究5-LOX及12-LOX在胰腺癌组织和细胞株SW1990中的表达，用四甲基偶氮唑蓝（MTT）还原法及溴脱氧尿嘧啶（BrdU）标记法研究不饱和脂肪酸包括花生四烯酸（AA）、二十二碳六烯酸（DHA）和二十碳五烯酸（EPA）以及5-LOX抑制剂MK-886和12-LOX抑制剂Baicalein对SW1990细胞增殖的影响；并用末端脱氧核苷酰转移酶介导的d-UTP-生物素缺口末端标记法（TUNEL）及流式细胞术方法研究上述物质对SW1990细胞凋亡的影响。结果5-LOX及12-LOX在胰腺癌组织和SW1990人胰腺癌细胞呈高表达，显著高于人正常胰腺组织对照。AA促进胰腺癌细胞株SW1990的增殖，且呈剂量依赖性；而DHA及EPA抑制SW1990细胞增殖，均呈剂量依赖性，DHA及EPA尚可促进SW1990细胞凋亡。MK-886及Baicalein均能抑制胰腺癌细胞株SW1990的体外增殖，并呈剂量依赖性，两者均可促进SW1990细胞凋亡，作用24h后凋亡细胞比例增高。结论5-LOX及12-LOX在胰腺癌中表达上调，PUFA对胰腺癌细胞增殖与凋亡存在调节作用，并且不同脂肪酸作用存在差异。从促进胰腺癌细胞增殖，而DHA及EPA抑制其增殖，促进其凋亡。LOX抑制剂体外可抑制胰腺癌细胞增殖，并诱导细胞凋亡。LOX可能是胰腺癌生物化学治疗的新靶点。

Effect of 5-Iipoxygenase and 12-lipoxygenase on proliferation and apoptosis of pancreatic cancer cell

Objective To examine the expression of lipoxygenases (LOXs)on human pancreatic carcinoma and their effects on proliferation and apoptosis of human pancreatic carcinoma in vitro.Methods Expression of 5- LOX and 12-LOX in the tissue of human pancreatic carcinoma and pancreatic cancer cell line (SW1990) was detected by immunohistochemical staining and RT-PCR.To examine the effects of polyunsaturated fatty acids on pancreatic cancer cell line,the proliferation rate of SW1990 cells treated with arachidouic acid (AA),docosahexaenoic acid (DHA) and eicosapentenoic acid (EPA) was analyzed by MTT and the incorporation of bromodeoxyuridine (BrdU) methods.An annexinV/propidium iodide (PI) assay with flow cytometry and in situ terminal deoxynucleotidyl transferase-mediated dUTP-digoxigenin end labeling (TUNEL) assay were used to identify potential induction of apoptosis by the unsaturated fatty acids.The effects of 5-LOX inhibitor (MK-886) and 12-LOX inhibitor (baicalein) on the proliferation of SW1990 cells were determined by above methods.Results Both 5-LOX and 12-LOX were over expressed in the tissue of human pancreatic carcinoma and the pancreatic cancer cell line.AA had a stimulatory effect on the growth of SW1990 cells while EPA and DHA had an inhibitory effect in a dose-dependent manner.The apeptosis of SW1990 cells co-cultured with DHA or EPA lasting for 24 hours was increased markedly.Furthermore, both MK-886 and baicalein in a dose-dependent-manner inhibited the growth of SW1990 cells ard induced a significant increase of apoptotic cells rate.Conclusions Expression of lipoxygenase is up-regulated in human pancreatic cancer. Polyunsaturated fatty acids have regulatory effects on the growth of pancreatic carcinoma in vitro.AA stimulates proliferation of pancreatic cancer cell line,while DHA and EPA suppress proliferation,simultaneously inducing apoptosis of pancreatic cancer cell line.Blocking the functions of lipoxygenase with its inhibitor exerts a negative regulatory effect on the growth of pancreatic carcinoma in vitro.Lipoxygenase might be a novel therapeutic target for the pancreatic cancer.