Investigation of indolamine 2, 3 dioxygenase (IDO-1) gene expression by real-time PCR among patients with lung cancer

Dual-target inhibitors of indoleamine 2, 3 dioxygenase 1 (Ido1): A promising direction in cancer immunotherapy

Indoleamine 2, 3-dioxygenase 1 (IDO1) is a rate-limiting enzyme that catalyzes the kynurenine (Kyn) pathway of tryptophan metabolism in the first step, and the kynurenine pathway plays a fundamental role in immunosuppression in the tumor microenvironment. Therefore, researchers are vigorously developing IDO1 inhibitors, hoping to apply them to cancer immunotherapy. Nowadays, there have been 11 kinds of IDO1 inhibitors entering clinical trials, among which many inhibitors have shown good tumor inhibitory effect in phase I/II clinical trials. But the phase III study of the most promising IDO1 inhibitor compound 29 (Epacadostat) failed in 2018, which may be caused by the compensation effect offered by tryptophan 2,3-dioxygenase (TDO), the mismatched drug combination strategies, or other reasons. Luckily, dual-target inhibitors show great potential and advantages in solving these problems. In recent years, many studies have linked IDO1 to popular targets and selected many IDO1 dual-target inhibitors through pharmacophore fusion strategy and library construction, which enhance the tumor inhibitory effect and reduce side effects. Currently, three kinds of IDO1/TDO dual-target inhibitors have entered clinical trials, and extensive studies have been developing on IDO1 dual-target inhibitors. In this review, we summarize the IDO1 dual-target inhibitors developed in recent years and focus on the structure optimization process, structure-activity relationship, and the efficacy of in vitro and in vivo experiments, shedding a light on the pivotal significance of IDO1 dual-target inhibitors in the treatment of cancer, providing inspiration for the development of new IDO1 dual-target inhibitors.

Mechanism of miR-760 Reversing Lung Cancer Immune Escape by Downregulating IDO1 and Eliminating Regulatory T Cells Based on Mathematical Biology

In cancer biology, mathematical models have become indispensable. They are useful for gaining a mechanistic grasp of cancer's dynamic processes. In cancer research, mathematical modelling approaches are becoming more common. The complexity of cancer is well suited to quantitative approaches as it provides challenges and opportunities for new developments (Altrock et al., 2015). Background. MicroRNA-760 (miR-760), as an early discovered tumor suppressor gene, is poorly expressed in lung cancer (LC). Indoleamine 2,3-dioxygenase 1 (IDO1), as an important regulator of T cell function, is active in immune tolerance. We discovered that miR-760 has a targeted relationship with IDO1, but the regulatory mechanism between miR-760 and IDO1 is still unclear. Method. The miR-760 and IDO1 levels in NSCLC were tested via real-time quantitative polymerase chain reaction (qRT-PCR) and western blotting (WB). Cell growth was tested by CCK8, and NSCLC cell migration and invasion were analyzed through Transwell analysis. The binding conditions and target gene of miR-451 in NSCLC cells were determined via double luciferase reporter gene. The CD8+ T and CD4+ T cell ratio in CD45+cells was assessed by flow cytometry. Results. qRT-PCR revealed that miR-760 was low-expressed and IDO2 was highly expressed in LC. miR-760 mimics suppressed cell growth, invasiveness, and migration. We also observed that miR-760 could downregulate the IDO1 protein level. Significantly, we revealed that miR-760 could inhibit CD8+ T cell apoptosis by controlling IDO1 enzyme function. Conclusion. Our findings show that miR-760 inhibits CD8+ T cell responses in LC through regulating IDO1, laying the groundwork for the development of novel vaccination therapies for the treatment of LC.

IDO1 plays a tumor-promoting role via MDM2-mediated suppression of the p53 pathway in diffuse large B-cell lymphoma

With the intensive therapeutic strategies, diffuse large B-cell lymphoma (DLBCL) is still a fatal disease due to its progressive characteristics. Indoleamine 2,3-dioxygenase 1 (IDO1) is a key regulator that catalyzes the commitment step of the kynurenine pathway in the immune system, its aberrant activation may contribute to malignant cell escape eradication. However, the role of IDO1 in DLBCL progression remains elusive. Our study showed IDO1 expression was upregulated in DLBCL and was associated with a poor prognosis and low overall survival. Inhibition of IDO1 suppressed DLBCL cell proliferation in vitro and impeded xenograft tumorigenesis in vivo. RNA-seq analyses revealed MDM2 was downregulated while TP53 was upregulated in IDO1 inhibition OCI-Ly10 cells. Mechanistically, IDO1 inhibition decreased the expression of MDM2, a major negative regulator of p53, and restored p53 expression in OCI-Ly3 and OCI-Ly10 cells, resulting in cell cycle arrest and apoptosis. IDO1 inhibition induced cell apoptosis coupled with PUMA and BAX upregulation, as well as BCL2 and BCL-XL downregulation. In addition, p21, a p53 transcriptional target, was upregulated in cell cycle arrest. Taken together, this study revealed IDO1 is essential for the proliferation of DLBCL cells and may be a potential therapeutic target for the treatment of DLBCL.