Instituto de Inmunología, Facultad de Medicina, Universidad Austral de Chile, 511-0566, Valdivia, Chile.
Escuela de Graduados de Ciencias, Universidad Austral de Chile, 511-0566, Valdivia, Chile.
Biol Res. 2023 Sep 29;56(1):51. doi: 10.1186/s40659-023-00461-2.
Nitric oxide is produced by different nitric oxide synthases isoforms. NO activates two signaling pathways, one dependent on soluble guanylate cyclase and protein kinase G, and other where NO post-translationally modifies proteins through S-nitrosylation, which is the modification induced by NO in free-thiol cysteines in proteins to form S-nitrosothiols. High levels of NO have been detected in blood of breast cancer patients and increased NOS activity has been detected in invasive breast tumors compared to benign or normal breast tissue, suggesting a positive correlation between NO biosynthesis, degree of malignancy and metastasis. During metastasis, the endothelium plays a key role allowing the adhesion of tumor cells, which is the first step in the extravasation process leading to metastasis. This step shares similarities with leukocyte adhesion to the endothelium, and it is plausible that it may also share some regulatory elements. The vascular cell adhesion molecule-1 (VCAM-1) expressed on the endothelial cell surface promotes interactions between the endothelium and tumor cells, as well as leukocytes. Data show that breast tumor cells adhere to areas in the vasculature where NO production is increased, however, the mechanisms involved are unknown.
We report that the stimulation of endothelial cells with interleukin-8, and conditioned medium from breast tumor cells activates the S-nitrosylation pathway in the endothelium to induce leukocyte adhesion and tumor cell extravasation by a mechanism that involves an increased VCAM-1 cell surface expression in endothelial cells. We identified VCAM-1 as an S-nitrosylation target during this process. The inhibition of NO signaling and S-nitrosylation blocked the transmigration of tumor cells through endothelial monolayers. Using an in vivo model, the number of lung metastases was inhibited in the presence of the S-nitrosylation inhibitor N-acetylcysteine (NAC), which was correlated with lower levels of S-nitrosylated VCAM-1 in the metastases.
S-Nitrosylation in the endothelium activates pathways that enhance VCAM-1 surface localization to promote binding of leukocytes and extravasation of tumor cells leading to metastasis. NAC is positioned as an important tool that might be tested as a co-therapy against breast cancer metastasis.
一氧化氮是由不同的一氧化氮合酶同工酶产生的。NO 激活两条信号通路，一条依赖于可溶性鸟苷酸环化酶和蛋白激酶 G，另一条通路是 NO 通过 S-亚硝基化使蛋白质发生翻译后修饰，即 NO 在蛋白质中的自由巯基半胱氨酸上诱导形成 S-亚硝基硫醇的修饰。在乳腺癌患者的血液中检测到高水平的 NO，并且在侵袭性乳腺癌肿瘤中检测到 NOS 活性增加，与良性或正常乳腺组织相比，这表明 NO 生物合成、恶性程度和转移之间存在正相关。在转移过程中，内皮细胞起着关键作用，允许肿瘤细胞黏附，这是导致转移的血管外渗过程的第一步。这一步与白细胞黏附在内皮细胞上有相似之处，并且可能也有一些共同的调节元件。内皮细胞表面表达的血管细胞黏附分子-1（VCAM-1）促进内皮细胞与肿瘤细胞以及白细胞之间的相互作用。有数据表明，乳腺癌细胞黏附在内皮细胞中 NO 产生增加的区域，但具体机制尚不清楚。
我们报告称，白细胞介素-8刺激内皮细胞和乳腺癌细胞的条件培养基激活内皮细胞中的 S-亚硝基化途径，通过一种涉及内皮细胞表面 VCAM-1 细胞表面表达增加的机制诱导白细胞黏附和肿瘤细胞外渗。我们在这个过程中确定 VCAM-1 是 S-亚硝基化的靶标。NO 信号和 S-亚硝基化的抑制阻止了肿瘤细胞穿过内皮单层的迁移。在体内模型中，当存在 S-亚硝基化抑制剂 N-乙酰半胱氨酸（NAC）时，肺转移的数量减少，这与转移中 VCAM-1 的 S-亚硝基化水平较低相关。
内皮细胞中的 S-亚硝基化激活了增强 VCAM-1 表面定位的途径，从而促进白细胞的结合和肿瘤细胞的外渗，导致转移。NAC 被定位为一种重要的工具，可能作为针对乳腺癌转移的联合治疗进行测试。
