Dwyer-Nield Lori D, Srebernak Mary C, Barrett Bradley S, Ahn Jinhee, Cosper Pippa, Meyer Amy M, Kisley Lori R, Bauer Alison K, Thompson David C, Malkinson Alvin M
Department of Pharmaceutical Sciences, University of Colorado Health Sciences Center, 4200 East Ninth Avenue, Denver, CO 80262, USA.
Carcinogenesis. 2005 Jul;26(7):1196-206. doi: 10.1093/carcin/bgi061. Epub 2005 Mar 3.
Studies using transgenic and knockout mice have demonstrated that particular cytokines influence lung tumor growth and identified prostaglandin E2 (PGE2), prostacyclin (PGI2) and nitric oxide (NO) as critical mediators of this process. PGE2 and NO were pro-tumorigenic while PGI2 was antitumorigenic. We describe herein an in vitro experimental approach to examine interactions among cytokines, prostaglandins (PGs) and NO. PGE2, PGI2, and NO levels were assayed in culture media from non-tumorigenic mouse lung epithelial cell lines, their spontaneous transformants and mouse lung tumor-derived cell lines, before or after exposure to the cytokines TNFalpha, IFNgamma and IL1beta, alone and in combination. More PGE2 than PGI2 was produced by neoplastic cells, while the opposite was observed in non-tumorigenic lines. Cytokine exposure magnified the extent of these differential concentrations. The PGE2 to PGI2 ratio was also greater in chemically-induced mouse lung tumors than in adjacent tissue or control lungs, supporting the physiological relevance of this in vitro model. Expression of PG biosynthetic enzymes in these cell lines correlated with production of the corresponding PGs. Cytokine treatment enhanced NO production by inducing the inflammation-associated biosynthetic enzyme, inducible NO synthase (iNOS), but this did not correlate with the neoplastic status of cells. Inhibition of iNOS or cyclooxygenase 2 activity using aminoguanidine or NS-398 respectively, demonstrated that NO did not affect PG production nor did PGs influence NO production. Since lack of iNOS inhibits mouse lung tumor formation, we propose that this is independent of any modulation of PG synthesis in epithelial cells. The similar normal/neoplastic trends in PGE2 to PGI2 ratios both in vitro and in vivo, together with an amplification of this difference upon cytokine exposure, are consistent with the hypothesis that cytokines released during inflammation exacerbate differences in the behavior of neoplastic and normal lung cells.
使用转基因和基因敲除小鼠的研究表明，特定的细胞因子会影响肺肿瘤的生长，并确定前列腺素E2（PGE2）、前列环素（PGI2）和一氧化氮（NO）是这一过程的关键介质。PGE2和NO具有促肿瘤作用，而PGI2具有抗肿瘤作用。我们在此描述一种体外实验方法，以研究细胞因子、前列腺素（PGs）和NO之间的相互作用。在非致瘤性小鼠肺上皮细胞系、它们的自发转化细胞系以及小鼠肺肿瘤衍生细胞系暴露于细胞因子TNFα、IFNγ和IL1β单独或联合作用之前和之后，测定培养基中PGE2、PGI2和NO的水平。肿瘤细胞产生的PGE2比PGI2多，而在非致瘤性细胞系中观察到相反的情况。细胞因子暴露放大了这些差异浓度的程度。化学诱导的小鼠肺肿瘤中PGE2与PGI2的比值也高于相邻组织或对照肺，支持了这个体外模型的生理相关性。这些细胞系中PG生物合成酶的表达与相应PG的产生相关。细胞因子处理通过诱导炎症相关的生物合成酶——诱导型NO合酶（iNOS）来增强NO的产生，但这与细胞的肿瘤状态无关。分别使用氨基胍或NS - 398抑制iNOS或环氧化酶2的活性，表明NO不影响PG的产生，PGs也不影响NO的产生。由于缺乏iNOS会抑制小鼠肺肿瘤的形成，我们认为这与上皮细胞中PG合成的任何调节无关。体外和体内PGE2与PGI2比值的正常/肿瘤相似趋势，以及细胞因子暴露后这种差异的放大，与炎症期间释放的细胞因子加剧肿瘤性和正常肺细胞行为差异的假设一致。
