Fukumura D, Yuan F, Endo M, Jain R K
Edwin L. Steele Laboratory, Department of Radiation Oncology, Massachusetts General Hospital, Boston, MA 02114, USA.
Am J Pathol. 1997 Feb;150(2):713-25.
The present study was designed to define the role of nitric oxide (NO) in tumor microcirculation, through the direct intravital microcirculatory observations after administration of NO synthase (NOS) inhibitor and NO donor both regionally and systemically. More specifically, we tested the following hypotheses: 1) endogenous NO derived from tumor vascular endothelium and/or tumor cells increases and/or maintains tumor blood flow, decreases leukocyte-endothelial interactions, and increases vascular permeability, 2) exogenous NO can increase tumor blood flow via vessel dilatation and decrease leukocyte-endothelial interactions, and 3) NO production and tissue responses to NO are tumor dependent. To this end, a murine mammary adenocarcinoma (MCaIV) and a human colon adenocarcinoma (LS174T) were implanted in the dorsal skinfold chamber in C3H and severe combined immunodeficient mice, respectively, and observed by means of intravital fluorescence microscopy. Both regional and systemic inhibition of endogenous NO by N omega-nitro-L-arginine methyl ester (L-NAME; 100 mumol/L superfusion or 10 mg/kg intravenously) significantly decreased vessel diameter and local blood flow rate. The diameter change was dominant on the arteriolar side. Superfusion of NO donor (spermine NO, 100 mumol/L) increased tumor vessel diameter and flow rate, whereas systemic injection of spermine NO (2.62 mg/kg) had no significant effect on these parameters. Rolling and stable adhesion of leukocytes were significantly increased by intravenous injection of L-NAME. In untreated animals, both MCaIV and LS174T tumor vessels were leaky to albumin. Systemic NO inhibition significantly attenuated tumor vascular permeability of MCaIV but not of LS174T tumor. Immunohistochemical studies, using polyclonal antibodies to endothelial NOS and inducible NOS, revealed a diffuse pattern of positive labeling in both MCaIV and LS174T tumors. Nitrite and nitrate levels in tumor interstitial fluid of MCaIV but not of LS174T were significantly higher than that in normal subcutaneous interstitial fluid. These results support our hypotheses regarding the microcirculatory response to NO in tumors. Modulation of NO level in tumors is a potential strategy for altering tumor hemodynamics and thus improving oxygen, drug, gene vector, and effector cell delivery to solid tumors.
本研究旨在通过局部和全身给予一氧化氮合酶（NOS）抑制剂和一氧化氮供体后直接进行活体微循环观察，来确定一氧化氮（NO）在肿瘤微循环中的作用。更具体地说，我们检验了以下假设：1）源自肿瘤血管内皮和/或肿瘤细胞的内源性NO增加和/或维持肿瘤血流，减少白细胞与内皮细胞的相互作用，并增加血管通透性；2）外源性NO可通过血管扩张增加肿瘤血流并减少白细胞与内皮细胞的相互作用；3）NO的产生和组织对NO的反应取决于肿瘤。为此，分别将小鼠乳腺腺癌（MCaIV）和人结肠腺癌（LS174T）植入C3H小鼠和严重联合免疫缺陷小鼠的背部皮褶小室中，并通过活体荧光显微镜进行观察。用Nω-硝基-L-精氨酸甲酯（L-NAME；100μmol/L灌注或10mg/kg静脉注射）局部和全身抑制内源性NO均显著降低血管直径和局部血流速度。直径变化在小动脉侧占主导。灌注NO供体（精胺NO，100μmol/L）可增加肿瘤血管直径和血流速度，而全身注射精胺NO（2.62mg/kg）对这些参数无显著影响。静脉注射L-NAME可显著增加白细胞的滚动和稳定黏附。在未处理的动物中，MCaIV和LS174T肿瘤血管对白蛋白均有渗漏。全身抑制NO可显著降低MCaIV肿瘤的血管通透性，但对LS174T肿瘤无此作用。使用抗内皮NOS和诱导型NOS的多克隆抗体进行的免疫组织化学研究显示，MCaIV和LS174T肿瘤中均呈现弥漫性阳性标记模式。MCaIV肿瘤间质液中的亚硝酸盐和硝酸盐水平显著高于正常皮下间质液，但LS174T肿瘤并非如此。这些结果支持了我们关于肿瘤对NO微循环反应的假设。调节肿瘤中的NO水平是改变肿瘤血流动力学从而改善向实体瘤输送氧气、药物、基因载体和效应细胞的一种潜在策略。
