Indoleamine 2,3‐dioxygenase promotes peritoneal metastasis of ovarian cancer by inducing an immunosuppressive environment

Indoleamine 2,3‐dioxygenase (IDO) is a tryptophan‐catabolizing enzyme that has immunoregulatory functions. Our prior study showed that tumoral IDO overexpression is involved in disease progression and impaired patient survival in human ovarian cancer, although its mechanism remains unclear. The purpose of the present study is to clarify the role of IDO during the process of peritoneal dissemination of ovarian cancer. Indoleamine 2,3‐dioxygenase cDNA was transfected into the murine ovarian carcinoma cell line OV2944‐HM‐1, establishing stable clones of IDO‐overexpressing cells (HM‐1‐IDO). Then HM‐1‐IDO or control vector‐transfected cells (HM‐1‐mock) were i.p. transplanted into syngeneic immunocompetent mice. The HM‐1‐IDO‐transplanted mice showed significantly shortened survival compared with HM‐1‐mock‐transplanted (control) mice. On days 11 and 14 following transplantation, the tumor weight of peritoneal dissemination and ascites volume were significantly increased in HM‐1‐IDO‐transplanted mice compared with those of control mice. This tumor‐progressive effect was coincident with significantly reduced numbers of CD8⁺ T cells and natural killer cells within tumors as well as increased levels of transforming growth factor‐β and interleukin‐10 in ascites. Finally, treatment with the IDO inhibitor 1‐methyl‐tryptophan significantly suppressed tumor dissemination and ascites with reduced transforming growth factor‐β secretion. These findings showed that tumor‐derived IDO promotes the peritoneal dissemination of ovarian cancer through suppression of tumor‐infiltrating effector T cell and natural killer cell recruitment and reciprocal enhancement of immunosuppressive cytokines in ascites, creating an immunotolerogenic environment within the peritoneal cavity. Therefore, IDO may be a promising molecular target for the therapeutic strategy of ovarian cancer.     

吲哚胺2，3-双加氧酶与肿瘤免疫耐受

人体免疫系统可以对肿瘤表达的多种异常抗原产生免疫反应,但肿瘤通过复杂的进化过程所致的免疫耐受现象能够降低宿主针对肿瘤的自身免疫反应,使宿主无法通过免疫系统对肿瘤细胞作出免疫应答。因此该现象可导致肿瘤细胞逃避宿主的免疫监视以及免疫系统的攻击,从而使肿瘤细胞得以在人体内增殖和转移。IDO是细胞内催化L-色氨酸经犬尿氨酸途径进行分解代谢的关键酶,也是一种与免疫抑制相关的酶。IDO在多种病理生理过程中促进机体免疫耐受的发生,因此与肿瘤的发生发展有密切关系。大量研究发现,IDO作为一种重要的抑制性免疫检查点,在肿瘤患者中其酶活性的增加会促进肿瘤免疫耐受现象的建立。随着IDO介导肿瘤免疫耐受相关分子机制的发现与证实,IDO抑制剂也已成为肿瘤免疫疗法中的关键研究领域。本文重点阐明IDO发现的起源过程、在正常人体和肿瘤患者中的表达情况、调节色氨酸代谢等免疫调节功能以及IDO诱导TME中肿瘤免疫耐受建立的几种重要机制,包括色氨酸耗竭、激活芳香烃受体、诱导调节性T细胞扩增与活化以及募集和激活大量骨髓来源的抑制性细胞等机制,以便能够为今后的深入研究和IDO抑制剂的治疗应用提供更广阔的思维。     

吲哚胺2,3双加氧酶与肿瘤免疫耐受

调节性T细胞(Treg)介导的克隆抑制,是引起肿瘤免疫耐受的主要因素之一.而吲哚胺2,3双加氧酶(IDO)通过对Treg细胞的作用下调各系统肿瘤微环境中的免疫反应,从而诱导宿主免疫耐受的形成.IDO抑制剂1-MT将有望成为治疗肿瘤的新靶点.     

Indoleamine 2,3-dioxygenase is a novel prognostic indicator for endometrial cancer

Indoleamine 2,3-dioxygenase (IDO) is a tryptophan-catabolising enzyme inducing immune tolerance. The present study aimed to investigate IDO expression and its prognostic significance in endometrial cancer. Indoleamine 2,3-dioxygenase expression in endometrial cancer tissues (n = 80) was immunohistochemically scored as four groups (IDO-, 1+, 2+, and 3+). The high IDO expression (IDO2+ or 3+) in tumour cells was found in 37 (46.3%) of the 80 cases, and was positively correlated with surgical stage, myometrial invasion, lymph-vascular space involvement, and lymph node metastasis, but not with the histological grade. Patients with high IDO expression had significantly impaired overall survival and progression-free survival (PFS) (P = 0.002 and P = 0.001, respectively) compared to patients with no or weak expression of IDO (IDO- or 1+). The 5-year PFS for IDO-/1+, 2+, and 3+ were 97.7, 72.9, and 36.4%, respectively. Even in patients with early-stage disease (International Federation of Gynecology and Obstetrics I/II, n = 64), the PFS for IDO2+/3+ was significantly poor (P = 0.001) compared to that for IDO-/1+. On multivariate analysis, IDO expression was an independent prognostic factor for PFS (P = 0.020). These results indicated that the high IDO expression was involved in the progression of endometrial cancer and correlated with the impaired clinical outcome, suggesting that IDO is a novel and reliable prognostic indicator for endometrial cancer.     

Indoleamine 2,3-dioxygenase activity during chemotherapy or hormone therapy in patients with breast cancer

We evaluated the significance of indoleamine 2,3-dioxygenase (IDO) in breast cancer patients during chemotherapy or hormone therapy. IDO activity can be measured by tryptophan (Trp)/kynurenine (Kyn) ratio. Trp and Kyn were measured by high performance liquid chromatography (HPLC). The correlations about Trp/Kyn ratio between chemotherapy group and hormone therapy group in pre-chemotherapies or post-chemotherapies were studied. The Trp/Kyn ratio of chemotherapy group in post-FEC chemotherapy phase and in post-wPTX chemotherapy phase was higher than in pre-chemotherapy phase. And the Trp/Kyn ratio of chemotherapy group is significantly higher than hormone therapy in post-FEC chemotherapy phase and in post-wPTX chemotherapy phase. There were no significant changes for the Trp/Kyn ratio of hormone therapy group in each phase. These results suggest that the hormone therapy may be less invasive for breast cancer patients than the chemotherapy.     

Urokinase receptor promotes ovarian cancer cell dissemination through its 84-95 sequence

The clinical relevance of the urokinase receptor (uPAR) as a prognostic marker in ovarian cancer is well documented. We have shown that the uPAR sequence corresponding to 84-95 residues, linking D1 and D2 domains (uPAR_84-95), drives cell migration and angiogenesis in a protease-independent manner. This study is aimed at defining the contribution of uPAR_84-95 sequence to invasion of ovarian cancer cells. Now, we provide evidence that the ability of uPAR-expressing ovarian cancer cells to cross extra-cellular matrix and mesothelial monolayers is prevented by specific inhibitors of PAR_84-95 sequence. To specifically investigate uPAR_84-95 function, uPAR-negative CHO-K1 cells were stably transfected with cDNAs coding for uPAR D2 and D3 regions and exposing (uPARD2D3) or lacking (uPARΔD2D3) the 84–95 sequence. CHO-K1/D2D3 cells were able to cross matrigel, mesothelial and endothelial monolayers more efficiently than CHO-K1/ΔD2D3 cells, which behave as CHO-K1 control cells. When orthotopically implanted in nude mice, tumor nodules generated by CHO-K1/D2D3 cells spreading to peritoneal cavity were more numerous as compared to CHO-K1/ΔD2D3 cells. Ovarian tumor size and intra-tumoral microvessel density were significantly reduced in the absence of uPAR_84-95. Our results indicate that cell associated uPAR promotes growth and abdominal dissemination of ovarian cancer cells mainly through its uPAR_84-95 sequence.     

IDO在食管癌组织及血清中的表达及对进展的预测价值

目的:通过观察吲哚胺2,3-双加氧酶(IDO)在肿瘤及血清中的表达,探讨其是否可以作为评价食管癌进展情况的预测指标.方法:选取本院2015年01月至2017年12月行食管癌根治术的患者88例,根据是否存在淋巴浸润分成2组,其中淋巴浸润包含淋巴管侵犯和淋巴结转移,另外选取20名健康志愿者作为对照组,采用免疫组化半定量法检...     

Autotaxin in ascites promotes peritoneal dissemination in pancreatic cancer

Peritoneal dissemination and malignant ascites in pancreatic ductal adenocarcinoma (PDAC) patients represent a major clinical issue. Lysophosphatidic acid (LPA) is a lipid mediator that modulates the progression of various cancers. Based on the increasing evidence showing that LPA is abundant in malignant ascites, we focused on autotaxin (ATX), which is a secreted enzyme that is important for the production of LPA. This study aimed to elucidate the importance of the ATX‐LPA axis in malignant ascites in PDAC and to determine whether ATX works as a molecular target for treating peritoneal dissemination. In a PDAC peritoneal dissemination mouse model, the amount of ATX was significantly higher in ascites than in serum. An in vitro study using two PDAC cell lines, AsPC‐1 and PANC‐1, showed that ATX‐LPA signaling promoted cancer cell migration via the activation of the downstream signaling, and this increased cell migration was suppressed by an ATX inhibitor, PF‐8380. An in vivo study showed that PF‐8380 suppressed peritoneal dissemination and decreased malignant ascites, and these results were validated by the biological analysis as well as the in vitro study. Moreover, there was a positive correlation between the amount of ATX in ascites and the degree of disseminated cancer progression. These findings demonstrated that ATX in ascites works as a promotor of peritoneal dissemination, and the targeting of ATX must represent a useful and novel therapy for peritoneal dissemination of PDAC.     

Indoleamine 2,3-dioxygenase expression in human cancers: clinical and immunologic perspectives

Indoleamine 2,3-dioxygenase (IDO) is a tryptophan-catabolizing enzyme with immune-regulating activities in many contexts, such as fetal protection, allograft protection, and cancer progression. Clinical trials are currently evaluating IDO inhibition with 1-methyltryptophan in cancer immunotherapy. However, the exact role of tryptophan catabolism by IDO in human cancers remains poorly understood. Here, we review several studies that correlate IDO expression in human cancer samples and tumor-draining lymph nodes, with relevant clinical or immunologic parameters. IDO expression in various histologic cancer types seems to decrease tumor infiltration of immune cells and to increase the proportion of regulatory T lymphocytes in the infiltrate. The impact of IDO on different immune cell infiltration leads to the conclusion that IDO negatively regulates the recruitment of antitumor immune cells. In addition, increased IDO expression correlates with diverse tumor progression parameters and shorter patient survival. In summary, in the vast majority of the reported studies, IDO expression is correlated with a less favorable prognosis. As we may see results from the first clinical trials with 1-methyltryptophan in years to come, this review brings together IDO studies from human studies and aims to help appreciate outcomes from current and future trials. Consequently, IDO inhibition seems a promising approach for cancer immunotherapy.     

Indoleamine 2,3-dioxygenase contributes to tumor cell evasion of T cell-mediated rejection

The priming of an appropriate anti-tumor T cell response rarely results in the rejection of established tumors. The characteristics of tumors that allow them to evade a T cell-mediated rejection are unknown for many tumors. We report on evidence that the expression of the immunosuppressive enzyme, indoleamine 2,3-dioxygenase (IDO) by mononuclear cells that invade tumors and tumor-draining lymph nodes, is 1 mechanism that may account for this observation. Lewis lung carcinoma (LLC) cells stimulated a more robust allogeneic T cell response in vitro in the presence of a competitive inhibitor of IDO, 1-methyl tryptophan. When administered in vivo this inhibitor also resulted in delayed LLC tumor growth in syngeneic mice. Our study provides evidence for a novel mechanism whereby tumors evade rejection by the immune system, and suggests the possibility that inhibiting IDO may be developed as an anti-cancer immunotherapeutic strategy.     

Akt promotes cisplatin resistance in human ovarian cancer cells through inhibition of p53 phosphorylation and nuclear function

Resistance to cisplatin-based chemotherapy is a major cause of treatment failure in human ovarian cancer. Wild-type TP53 status is often, but not always, associated with cisplatin sensitivity, suggesting that additional factors may be involved. Overexpression/activation of the phosphatidylinositol-3-kinase/Akt pathway is commonly observed in ovarian cancer, and Akt activation is a determinant of chemoresistance in ovarian cancer cells, an effect that may be due, in part, to its inhibitory actions on p53-dependent apoptosis. To that end, we examined the role and regulation of p53 in chemosensitive ovarian cancer cells, as well as in their chemoresistant counterparts, and investigated if and how Akt influences this pathway. Cisplatin induced apoptosis in chemosensitive, but not chemoresistant cells, and this was inhibited by downregulation of p53. Cisplatin upregulated PUMA in a p53-dependent manner, and the presence of PUMA was necessary, but not sufficient for cisplatin-induced apoptosis. p53 was phosphorylated on numerous N-terminal residues, including Ser15, Ser20, in response to cisplatin in chemosensitive, but not chemoresistant cells. Furthermore, activation of Akt inhibited the cisplatin-induced upregulation of PUMA, and suppressed cisplatin-induced p53 phosphorylation, while inhibition of Akt increased total and phospho-p53 contents and sensitized p53 wild-type, chemoresistant cells to cisplatin-induced apoptosis. Finally, mutation of Ser15 and/or Ser20, but not of Ser37, to alanine significantly attenuated the ability of p53 to facilitate CDDP-induced apoptosis, and this was independent of PUMA expression. These results support the hypothesis that p53 is a determinant of CDDP sensitivity, and suggest that Akt contributes to chemoresistance, in part, by attenuating p53-mediated PUMA upregulation and phosphorylation of p53, which are essential, but independent determinants of sensitivity to CDDP-induced apoptosis.     

Indoleamine-2,3-dioxygenase, an immunosuppressive enzyme that inhibits natural killer cell function, as a useful target for ovarian cancer therapy

This study examined the role of the immuno-suppressive enzyme indoleamine-2,3-dioxygenase (IDO) in ovarian cancer progression, and the possible application of this enzyme as a target for ovarian cancer therapy. We transfected a short hairpin RNA vector targeting IDO into the human ovarian cancer cell line SKOV-3, that constitutively expresses IDO and established an IDO downregulated cell line (SKOV-3/shIDO) to determine whether inhibition of IDO mediates the progression of ovarian cancer. IDO downregulation suppressed tumor growth and peritoneal dissemination in vivo, without influencing cancer cell growth. Moreover, IDO downregulation enhanced the sensitivity of cancer cells to natural killer (NK) cells in vitro, and promoted NK cell accumulation in the tumor stroma in vivo. These findings indicate that downregulation of IDO controls ovarian cancer progression by activating NK cells, suggesting IDO targeting as a potential therapy for ovarian cancer.     

Endostatin binding to ovarian cancer cells inhibits peritoneal attachment and dissemination

Ovarian cancer cells use integrins to attach to the peritoneal wall. Integrin alpha(5)beta(1) is also the target for the angiogenesis inhibitor, endostatin. Therefore, the ability of endostatin to competitively inhibit tumor cell seeding of the peritoneum was investigated. An imaging method was developed to determine early phases of peritoneal dissemination of ovarian cancer cells. Using this method, endostatin was found to bind ovarian cancer cells through integrin alpha(5)beta(1) and inhibit vessel cooption efficiently. Although both angiostatin and endostatin are potent inhibitors of tumor angiogenesis, peritoneal attachment and vessel cooption was blocked only by the endostatin. Knocking down the expression of integrins alpha(5) and beta(1) in ovarian cancer cells interfered with endostatin-mediated inhibition of peritoneal seeding. Furthermore, adenovirus-mediated in situ expression of endostatin either inside the peritoneum or by the ovarian tumor cells inhibited peritoneal seeding and dissemination in vivo. Endostatin treatment also prevented primary ovarian cancer cells from attaching to mouse peritoneal wall. These studies show a paraendothelial mechanism by which endostatin can inhibit peritoneal dissemination of ovarian cancer cells and raises the possibility of intraperitoneal expression of endostatin to reduce recurrence.     

Intraperitoneal chemotherapy with taxanes for ovarian cancer with peritoneal dissemination.

Paclitaxel and docetaxel are currently the two clinically available taxanes. The combination of a taxane and a platinum compound has become the systemic chemotherapy of choice for primary ovarian cancer. Despite the high activity of these drugs in systemic chemotherapy, the majority of patients with advanced ovarian cancer will develop recurrent disease and ultimately decease of this disease. Therefore, more effective systemic chemotherapy regimens or alternative treatment modalities are warranted. Intraperitoneal chemotherapy is such an alternative treatment option. Pharmacokinetic studies on intraperitoneal administration of paclitaxel and docetaxel demonstrated very high locoregional drug concentrations and exposure. Their activity and response seem to be dose-dependent and hence higher efficacy with limited systemic toxicity is to be expected. Intraperitoneal chemotherapy may be combined intraoperatively with hyperthermia, which enhances tissue penetration and cytotoxic activity of many drugs. The data concerning thermal enhancement of taxanes are inconsistent, but at the high locoregional concentrations provided by intraperitoneal drug administration such a thermal enhancement seems to exist. Clinical studies have clearly demonstrated the feasibility and efficacy of intraperitoneal instillation chemotherapy with taxanes in patients with ovarian cancer. Preliminary results of a phase III study demonstrated improved outcome with the addition of intraperitoneal instillation chemotherapy to systemic chemotherapy after optimal primary cytoreductive surgery. Intraoperative hyperthermic intraperitoneal chemotherapy with docetaxel has been performed in a single study, in which promising results were observed. Further clinical investigations with an adequate follow-up period are needed to confirm the promising initial results and to determine the exact efficacy of intraperitoneal chemotherapy with these drugs.     

c-Met overexpression is a prognostic factor in ovarian cancer and an effective target for inhibition of peritoneal dissemination and invasion

The hepatocyte growth factor receptor c-Met is a receptor tyrosine kinase that plays an important role in tumor growth by activating mitogenic signaling pathways. The goal of this study was to evaluate the role of c-Met in the biology of ovarian cancer and to determine its potential as a therapeutic target. c-Met protein expression was detected by immunohistochemistry in 138 advanced-stage ovarian cancers using a tissue microarray annotated with disease-specific patient follow-up. Fifteen of 138 (11%) tissues had c-Met overexpression. Median survival for patients with high c-Met levels was 17 months versus 32 months (P = 0.001) for patients with low c-Met expression. Infection of SKOV-3ip1 cells with an adenovirus expressing a small interfering RNA (siRNA) against c-Met efficiently inhibited c-Met protein and mRNA expression as well as extracellular signal-regulated kinase and phosphatidylinositol 3-kinase signaling. It also inhibited adhesion to different extracellular matrix components, human primary mesothelial cells, and full-thickness human peritoneum and, in vivo, to mouse peritoneum. This was paralleled by a significant reduction in alpha(5) and beta(1) integrin protein and mRNA expression as well as a reduction of urokinase and matrix metalloproteinase (MMP)-2/MMP-9 activity. In SKOV-3ip1 ovarian cancer xenografts, i.p. treatment with the c-Met siRNA significantly reduced tumor burden, ascites formation, protease activity, and the number of peritoneal implants but not tumor size or angiogenesis. These results suggest that c-Met overexpression is a prognostic factor in ovarian cancer and that targeting c-Met in vivo inhibits peritoneal dissemination and invasion through an alpha(5)beta(1) integrin-dependent mechanism. Therefore, c-Met should be explored further as a therapeutic target in ovarian cancer.     

Indoleamine 2,3-dioxygenase up regulates the expression of human leucocyte antigen-G in hepatocellular carcinoma cells

目的:探讨人类吲哚胺2,3-双加氧酶(indoleamine 2,3-dioxygenase,IDO)对肝癌细胞人类白细胞抗原-G(human leucocyte antigen-G,HLA-G)表达的影响.方法:用脂质体lipofectamineTM2000将pcDNA3.1-IDO重组质粒稳定转染入肝癌SMMC-77 2 1细胞作为实验组(pcDNA3.1-IDO质粒转染组),同时设置空载体对照组(pcDNA3.1转染组)和空白对照组(未转染组),用RTPCR和Western blot鉴定实验组和2个对照组细胞IDO mRNA和蛋白的表达,然后分别给予实验组细胞IDO的抑制剂(2.5 mmol/L 1-DMT)和底物(200μmol/L L-色氨酸)干预48 h,进一步用实时荧光定量PCR和Westernblot检测上述5组细胞中HLA-G mRNA和蛋白的表达水平.结果:RT-PCR和Western blot显示空载体对照组和空白对照组未见IDO表达,而实验组细胞高表达IDO.实时荧光定量PCR和Western blot结果显示,实验组HLA-G mRNA和蛋白表达水平较空载体对照组和空白对照组均明显上调(P均＜0.05),给予1-D-MT和L-色氨酸干预后此效应可逆转.结论:在肝癌SMMC-7721细胞,IDO可以上调HLA-G的表达,色氨酸降解途径参与了此调节过程.     

Significance of vascular endothelial growth factor in growth and peritoneal dissemination of ovarian cancer

Vascular endothelial growth factor (VEGF) is a key regulator of angiogenesis which drives endothelial cell survival, proliferation, and migration while increasing vascular permeability. Playing an important role in the physiology of normal ovaries, VEGF has also been implicated in the pathogenesis of ovarian cancer. Essentially by promoting tumor angiogenesis and enhancing vascular permeability, VEGF contributes to the development of peritoneal carcinomatosis associated with malignant ascites formation, the characteristic feature of advanced ovarian cancer at diagnosis. In both experimental and clinical studies, VEGF levels have been inversely correlated with survival. Moreover, VEGF inhibition has been shown to inhibit tumor growth and ascites production and to suppress tumor invasion and metastasis. These findings have laid the basis for the clinical evaluation of agents targeting VEGF signaling pathway in patients with ovarian cancer. In this review, we will focus on VEGF involvement in the pathophysiology of ovarian cancer and its contribution to the disease progression and dissemination.