IDO1/AhR/ZEB1通路促进三阴性乳腺癌转移的机制研究及意义

Our previous study found that the IDO1 inhibitor could restrain the migration and invasion ability of triple-negative breast cancer (TNBC) cells, accompanied by elevated expression of E-cadherin, which acted as a key molecular marker in epithelial mesenchymal transformation (EMT). While ZEB1 promoted EMT by inhibiting E-cadherin in TNBC. Further studies showed that IDO1 inhibition reduced ZEB1 expression, but the underlying molecular mechanisms still remained unknown. AhR:Arnt heterodimer, the downstream components of IDO1 pathway, was identified as a potential transcription factor of ZEB1 using bioinformatics analysis. In addition to promoting EMT, ZEB1 also involved in preserving DNA stability and reducing gene mutation rates. Therefore, we hypothesized that IDO1 inhibitor down-regulated ZEB1 expression through IDO1/Kyn/AhR pathway, which could not only inhibit the metastasis of TNBC by regulating EMT, but also increase DNA mutation rates to improve the efficacy of anti-PD-1 therapy. We dive deep into the molecular mechanism of how IDO1 regulated ZEB1 expression. Then we constructed mice model to evaluate the influence of IDO1 inhibitor on metastasis of TNBC and the effectiveness of immune checkpoint inhibitors in vivo. This research not only helped to elucidate the mechanism of the IDO1 affecting TNBC metastasis, but also provided theoretical basis for a combination therapy of checkpoint inhibitors in the treatment of TNBC and a potentially important predictor of clinical efficacy.

我们前期研究发现IDO1抑制剂减弱三阴性乳腺癌（TNBC）细胞的迁移和侵袭能力，并上调上皮间质转化（EMT）标志物E钙粘蛋白表达。而ZEB1能下调E钙粘蛋白促进TNBC的EMT。进一步研究表明抑制IDO1下调ZEB1表达，但作用机制尚不明确。通过生物信息学预测发现ZEB1启动子区含有IDO1通路的下游组分AhR:Arnt的结合位点。除了参与调控EMT，研究报道ZEB1也参与调节DNA的稳定性，减少DNA突变率。所以我们推测IDO1抑制剂通过IDO1/Kyn/AhR通路下调ZEB1表达，不仅抑制EMT影响TNBC转移，而且增加DNA的突变率提高免疫治疗疗效。本研究将深入探究IDO1调控ZEB1影响TNBC转移的分子机制，体内研究IDO1对TNBC转移的影响和ZEB1在免疫治疗中的作用。本项目不仅有助于阐明IDO1影响TNBC转移的机制，而且为TNBC的免疫联合治疗提供理论依据和疗效预测因子。

三阴性乳腺癌（TNBC）是乳腺癌中恶性程度最高的亚型，其高度的侵袭转移能力、有限的治疗方案是TNBC患者死亡的主要原因，目前免疫检查点抑制成为恶性肿瘤重要的治疗手段之一，如IDO1，而其在TNBC侵袭转移方面的作用和机制尚不明确。我们探究了IDO1在TNBC细胞侵袭转移中的作用，分析IDO1与上皮间质转化（EMT）调控因子的关系，明确IDO1与ZEB1之间的交互作用及可能的分子机制，结合乳腺癌患者数据库，分析ZEB1与IDO1、肿瘤突变负荷（TMB）、肿瘤浸润淋巴细胞（TILs）等之间的相关性。我们的研究发现抑制TNBC中IDO1的表达能够降低TNBC细胞的迁移和侵袭能力，并上调EMT标志物E钙粘蛋白表达。已知TNBC中ZEB1能下调E钙粘蛋白，促进EMT。进一步研究表明抑制IDO1能够下调ZEB1表达。通过生物信息学预测我们发现ZEB1启动子区含有IDO1通路的下游组分AhR:Arnt的结合位点，且IDO1的启动子序列含有多个ZEB1的结合位点。有研究指出ZEB1可以参与调节肿瘤细胞DNA的稳定性，减少DNA突变率。通过生物信息学分析，我们发现乳腺癌中ZEB1表达与TMB负相关，低表达ZEB1患者TMB高。进一步研究发现ZEB1与微卫星不稳定性（MSI）、新抗原、TILs等之间存在相关性，表明其在乳腺癌免疫微环境中发挥作用。综上所述，通过抑制IDO1能够下调ZEB1的表达，不仅抑制TNBC的转移，而且提高了TNBC的TMB，增加免疫治疗的疗效。临床中ZEB1可能成为预测TNBC免疫治疗疗效的重要预测因子。