Department of Comprehensive Dentistry, University of Texas Health Science Center at San Antonio School of Dentistry, San Antonio, TX, USA.
Department of Pathology, University of Texas Health Science Center at San Antonio School of Medicine, San Antonio, TX, USA.
J Oral Pathol Med. 2018 Aug;47(7):674-682. doi: 10.1111/jop.12735. Epub 2018 Jun 9.
Thymol is a transient receptor potential ankyrin subtype 1 channel, (TRPA1) agonist found in thyme and oregano. Thymol has antioxidant, anti-inflammatory, and antimicrobial properties; thus, thymol is added to many commercially available products including Listerine mouthwash. Thymol is also cytotoxic to HL-60 (acute promyelocytic leukemia) cells in vitro. Therefore, we evaluated the effects of thymol against oral squamous cell carcinoma (OSCC) and its anticancer mechanism-of-action.
The antiproliferative effects of thymol in OSCC Cal27 cells were determined by MTS assays. Antitumor effects were evaluated in Cal27- and HeLa-derived mouse xenografts. Calcium imaging, mitochondrial transmembrane potential (ΔΨm) studies, and Western blot analysis of cleaved PARP (c-PARP) evaluated thymol's mechanism-of-action.
Thymol had significant, long-lasting antiproliferative effects in vitro. In vivo, thymol displayed significant antitumor effects in Cal27-derived tumors. Thymol's anticancer effects were confirmed in HeLa-derived xenografts demonstrating that thymol effects are not tumor-type specific. Calcium imaging verified calcium influx in Cal27 cells that were reversed with the TRPA1 antagonist, HC030031. However, no calcium influx was seen in HeLa cells indicating that TRP channels do not regulate thymol cytotoxicity. This was confirmed using cell viability assays in which pre-treatment with HC030031 had no effect on thymol cytotoxicity. Instead, ΔΨm studies revealed that thymol induces significant ΔΨm depolarization and apoptosis.
Our findings provide the first evidence of thymol's novel antitumor effects against OSCC in vivo, which do not rely on TRPA1 activity. Instead, we show that thymol induces mitochondrial dysfunction and apoptosis and may be efficacious against multiple cancers.
百里香酚是一种瞬时受体电位锚蛋白 1 型通道（TRPA1）激动剂，存在于百里香和牛至中。百里香酚具有抗氧化、抗炎和抗菌特性；因此，百里香酚被添加到许多市售产品中，包括李施德林漱口水。百里香酚对 HL-60（急性早幼粒细胞白血病）细胞也具有细胞毒性。因此，我们评估了百里香酚对口腔鳞状细胞癌（OSCC）的作用及其抗癌作用机制。
通过 MTS 测定法确定百里香酚对 OSCC Cal27 细胞的增殖抑制作用。在 Cal27 和 HeLa 衍生的小鼠异种移植中评估抗肿瘤作用。通过钙成像、线粒体跨膜电位（ΔΨm）研究和裂解多聚（ADP-核糖）聚合酶（c-PARP）的 Western blot 分析评估百里香酚的作用机制。
百里香酚在体外具有显著且持久的抗增殖作用。在体内，百里香酚在 Cal27 衍生的肿瘤中显示出显著的抗肿瘤作用。百里香酚在 HeLa 衍生的异种移植中证实了其抗癌作用，表明百里香酚的作用不是肿瘤类型特异性的。钙成像验证了 Cal27 细胞中的钙内流，而 TRPA1 拮抗剂 HC030031 可逆转该作用。然而，在 HeLa 细胞中未观察到钙内流，表明 TRP 通道不调节百里香酚的细胞毒性。这通过细胞活力测定得到证实，其中 HC030031 的预处理对百里香酚的细胞毒性没有影响。相反，ΔΨm 研究表明，百里香酚诱导显著的 ΔΨm 去极化和细胞凋亡。
我们的研究结果首次提供了百里香酚在体内对 OSCC 的新型抗肿瘤作用的证据，该作用不依赖于 TRPA1 活性。相反，我们表明百里香酚诱导线粒体功能障碍和细胞凋亡，可能对多种癌症有效。
