Shappell S B, Gupta R A, Manning S, Whitehead R, Boeglin W E, Schneider C, Case T, Price J, Jack G S, Wheeler T M, Matusik R J, Brash A R, Dubois R N
Department of Pathology, Vanderbilt University Medical Center, Nashville, Tennessee 37232-2561, USA.
Cancer Res. 2001 Jan 15;61(2):497-503.
15-Lipoxygenase (15-LOX)-2 is expressed in benign prostate secretory cells and benign prostate produces 15S-hydroxyeicosatetraenoic acid (15S-HETE) from exogenous arachidonic acid (AA). In contrast, 15S-LOX-2 and 15S-HETE formation are reduced in prostate carcinoma (Pca). The mechanisms whereby reduced 15-LOX-2 may contribute to Pca development or progression are not known. We investigated the expression of peroxisome proliferator-activated receptor (PPAR) gamma in benign and malignant prostate tissues and the ability of 15S-HETE to activate PPARgamma-dependent transcription and modulate proliferation of the Pca cell line PC3. In contrast to benign prostate and similar to most Pca tissues, 15-LOX-2 mRNA was not detected in PC3 cells, and they did not produce detectable 15-HETE from [14C]AA. By reverse transcription-PCR, PPARgamma mRNA was present in 18 of 18 benign and 9 of 9 tumor specimens. The PPARgamma ligand BRL 49653 and 15S-HETE caused a dose-dependent inhibition of PC3 proliferation in a 14-day soft agar colony-forming assay (IC50 of 3 and 30 microM, respectively). 15S-HETE (10 microM) caused greater inhibition than 10 microM 15R-HETE. At 3 days, BRL 49653 and 15S-HETE caused a slight increase in cells in G0-G1 and a corresponding decrease in cells in S phase. In PC3 cells transiently transfected with a luciferase reporter linked to a PPAR response element, 1 microM BRL 49653 and 10 microM 15S-HETE caused approximately threefold and greater than twofold induction of PPAR-dependent transcription, respectively. By quantitative real-time reverse transcription-PCR and Northern analysis, 3-day treatment with BRL 49653 and 15S-HETE caused a reduction of PPARgamma expression but a marked up-regulation of the PPAR response element containing adipocyte type fatty acid binding protein. These results support the hypothesis that 15-LOX-2-derived 15S-HETE may constitute an endogenous ligand for PPARgamma in the prostate and that loss of this pathway by reduced expression of 15-LOX-2 may contribute to increased proliferation and reduced differentiation in prostate carcinoma.
15-脂氧合酶（15-LOX）-2在前列腺良性分泌细胞中表达，良性前列腺能将外源性花生四烯酸（AA）转化为15S-羟基二十碳四烯酸（15S-HETE）。相比之下，前列腺癌（Pca）组织中15S-LOX-2的表达及15S-HETE的生成均减少。15-LOX-2表达降低促进前列腺癌发生或进展的机制尚不清楚。我们研究了过氧化物酶体增殖物激活受体（PPAR）γ在前列腺良恶性组织中的表达，以及15S-HETE激活PPARγ依赖性转录并调节前列腺癌细胞系PC3增殖的能力。与前列腺良性组织不同，与大多数前列腺癌组织相似，在PC3细胞中未检测到15-LOX-2 mRNA，且它们不能从[14C]AA生成可检测到的15-HETE。通过逆转录聚合酶链反应（RT-PCR），在18份前列腺良性标本和9份肿瘤标本中均检测到PPARγ mRNA。在一项为期14天的软琼脂集落形成试验中，PPARγ配体BRL 49653和15S-HETE对PC3细胞增殖产生剂量依赖性抑制（IC50分别为3和30μM）。15S-HETE（10μM）比10μM 15R-HETE产生的抑制作用更强。在第3天，BRL 49653和15S-HETE使处于G0-G1期的细胞略有增加，而处于S期的细胞相应减少。在瞬时转染了与PPAR反应元件相连的荧光素酶报告基因的PC3细胞中，1μM BRL 49653和10μM 15S-HETE分别使PPAR依赖性转录诱导约3倍和2倍以上。通过定量实时逆转录聚合酶链反应和Northern分析，用BRL 49653和15S-HETE处理3天导致PPARγ表达降低，但含脂肪细胞型脂肪酸结合蛋白的PPAR反应元件显著上调。这些结果支持以下假说：15-LOX-2衍生的15S-HETE可能是前列腺中PPARγ的内源性配体，15-LOX-2表达降低导致该途径缺失可能促使前列腺癌增殖增加和分化降低。
