Department of Medical Biology, Faculty of Medicine, Sakarya University, Sakarya, Turkey.
J Pharm Pharm Sci. 2019;22(1):281-291. doi: 10.18433/jpps30493.
Toll-like receptor 4 (TLR4) is over-expressed in breast tumors and thus contributing to the tumor progression and metastasis. Natural products have drawn attention in cancer immunotherapy due to their various biological activities. Curcumin is well investigated in different types of cancer. However, the mechanisms underlying its anti-inflammatory actions have not been extensively elucidated. For this purpose, we explored the inhibitory effects of curcumin on lipopolysaccharide (LPS)-induced TLR4 dependent TRIF signaling pathway in two subtypes of breast cancer cell lines (MCF-7 and MDA-MB-231) in this study.
In this context, the cytotoxicity of curcumin and LPS alone and the combination of curcumin with LPS on these cells was evaluated by WST-1 assay. The expression level of TLR4 and the release of type I interferon (IFN) levels were determined after treatment with curcumin and/or LPS by RT-PCR and ELISA analysis, respectively. Furthermore, the subcellular localization of TLR4 and interferon regulatory factor 3 (IRF3) were detected by immunofluorescence analysis.
Curcumin treatment suppressed breast cancer cells viabilities and the activation of TLR4-mediated TRIF signaling pathway by the downregulation of TLR4 and IRF3 expression levels and the inhibition of type I IFN (IFN-α/β) levels induced by LPS. However, curcumin was more efficient in MDA- MB-231 cells than MCF-7 cells owing to its greater inhibitory efficacy in the LPS- enhanced TLR4 signaling pathway. Furthermore, IFN-α/β levels induced by TLR4 and IRF3 were decreased in these cells following curcumin treatment.
Consequently, these results demonstrated that the activation of LPS stimulated TLR4/TRIF/IRF3 signaling pathway was mediated by curcumin in breast cancer cells, in vitro. However, more studies are necessary to examine the curcumin's anti-inflammatory activities on TLR4/MyD88/NF-κB as well as other signaling pathways downstream of TLRs in breast cancer.
Toll 样受体 4（TLR4）在乳腺癌肿瘤中过度表达，从而促进肿瘤的进展和转移。天然产物因其多种生物活性而引起了癌症免疫治疗的关注。姜黄素已在不同类型的癌症中得到了广泛研究。然而，其抗炎作用的机制尚未得到广泛阐明。为此，我们在本研究中探讨了姜黄素对两种乳腺癌细胞系（MCF-7 和 MDA-MB-231）中脂多糖（LPS）诱导的 TLR4 依赖性 TRIF 信号通路的抑制作用。
在这种情况下，通过 WST-1 测定评估姜黄素和 LPS 单独以及姜黄素与 LPS 联合对这些细胞的细胞毒性。用 RT-PCR 和 ELISA 分析分别检测姜黄素和/或 LPS 处理后 TLR4 的表达水平和 I 型干扰素（IFN）水平的释放。此外，通过免疫荧光分析检测 TLR4 和干扰素调节因子 3（IRF3）的亚细胞定位。
姜黄素处理抑制乳腺癌细胞活力，并通过下调 TLR4 和 IRF3 表达水平以及抑制 LPS 诱导的 I 型 IFN（IFN-α/β）水平来抑制 TLR4 介导的 TRIF 信号通路的激活。然而，由于其在 LPS 增强的 TLR4 信号通路中具有更大的抑制作用，因此姜黄素在 MDA-MB-231 细胞中比 MCF-7 细胞更有效。此外，在用姜黄素处理后，这些细胞中 TLR4 和 IRF3 诱导的 IFN-α/β 水平降低。
因此，这些结果表明，在体外，姜黄素可激活 LPS 刺激的 TLR4/TRIF/IRF3 信号通路在乳腺癌细胞中。然而，需要更多的研究来检查姜黄素对 TLR4/MyD88/NF-κB 以及 TLRs 下游其他信号通路的抗炎活性在乳腺癌中的作用。
