PDE5 类磷酸二酯酶抑制剂（PDE5i）导致细胞内环状鸟苷酸单磷酸盐（cGMP）的增加，并被用于临床治疗勃起功能障碍。研究发现cGMP可能上下调节某些内分泌肿瘤细胞的生长，提示PDE5i可能影响癌症风险。我们评估了PDE5i是否可以在体外调节甲状腺癌细胞的生长。我们使用了恶性（K1）和良性（Nthy-ori 3-1）甲状腺细胞系，以及COS7细胞作为参考模型。细胞在0-24小时内用PDE5i瓦登非尔或cGMP类似物8-br-cGMP（nM-μM范围）处理。cGMP水平和半胱氨酸天冬酶3（caspase 3）裂解通过BRET，在cGMP或caspase 3生物传感器表达的细胞中进行评估。增殖相关外分泌调节激酶1和2（ERK1/2）的磷酸化通过Western blotting评估，核分裂通过DAPI染色。使用3-（4,5-二甲基噻唑-2-基）-2,5-二苯基四唑溴化物（MTT）测定细胞存活率。瓦登非尔和8-br-cGMP都可以有效地诱导所有细胞系的剂量依赖性cGMP BRET信号（p≤0.05）。然而，在所有浓度和时间点测试中，与未处理的细胞相比，PDE5i处理的细胞没有发生半胱氨酸天冬酶3的激活差异（p>0.05）。这些结果与细胞用8-br-cGMP处理时获得的结果相符，在所有细胞系中都未能诱导半胱氨酸天冬酶3裂解（p>0.05）。此外，它们反映了核碎片的缺乏。有趣的是，用vardenafil或类似物调节细胞内的cGMP水平并不影响恶性和良性甲状腺肿瘤细胞系的细胞存活率，也不影响ERK1/2的磷酸化（p>0.05）。这项研究表明，在K1和Nthy-ori 3-1细胞系中提高的cGMP水平与细胞存活或死亡无关，提示PDE5i不会影响甲状腺癌细胞的生长。由于此前发表了不同的结果，建议进行进一步的调查以澄清PDE5i对甲状腺癌细胞的影响。版权所有：© 2023 Alessandro等人。这是一篇开放获取的文章，根据知识共享署名许可证分发，允许在任何媒介上自由使用、分发和再现，前提是原作者和来源得到认可。

Type 5 phosphodiesterase (PDE5) inhibitors (PDE5i) lead to intracellular cyclic-guanosine monophosphate (cGMP) increase and are used for clinical treatment of erectile dysfunction. Studies found that cGMP may up/downregulate the growth of certain endocrine tumor cells, suggesting that PDE5i could impact cancer risk.We evaluated if PDE5i may modulate thyroid cancer cell growth in vitro.We used malignant (K1) and benign (Nthy-ori 3-1) thyroid cell lines, as well as the COS7 cells as a reference model. Cells were treated 0-24 h with the PDE5i vardenafil or the cGMP analog 8-br-cGMP (nM-μM range). cGMP levels and caspase 3 cleavage were evaluated by BRET, in cGMP or caspase 3 biosensor-expressing cells. Phosphorylation of the proliferation-associated extracellularly-regulated kinases 1 and 2 (ERK1/2) was evaluated by Western blotting, while nuclear fragmentation by DAPI staining. Cell viability was investigated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay.Both vardenafil and 8-br-cGMP effectively induced dose-dependent cGMP BRET signals (p≤0.05) in all the cell lines. However, no differences in caspase 3 activation occurred comparing PDE5i-treated vs untreated cells, at all concentrations and time-points tested (p>0.05). These results match those obtained upon cell treatment with 8-br-cGMP, which failed in inducing caspase 3 cleavage in all the cell lines (p>0.05). Moreover, they reflect the lack of nuclear fragmentation. Interestingly, the modulation of intracellular cGMP levels with vardenafil or the analog did not impact cell viability of both malignant and benign thyroid tumor cell lines, nor the phosphorylation of ERK1/2 (p>0.05).This study demonstrates that increased cGMP levels are not linked to cell viability or death in K1 and Nthy-ori 3-1 cell lines, suggesting that PDE5i do not impact the growth of thyroid cancer cells. Since different results were previously published, further investigations are recommended to clarify the impact of PDE5i on thyroid cancer cells.Copyright: © 2023 Alessandro et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.