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 ¼ 80) was immunohistochemically scored as four groups (IDOÀ, 1 þ , 2 þ , and 3 þ ). The high IDO expression (IDO2 þ or 3 þ ) 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 ¼ 0.002 and P ¼ 0.001, respectively) compared to patients with no or weak expression of IDO (IDOÀ or 1 þ ). The 5-year PFS for IDOÀ/1 þ , 2 þ , and 3 þ 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 ¼ 64), the PFS for IDO2 þ /3 þ was significantly poor (P ¼ 0.001) compared to that for IDOÀ/1 þ . On multivariate analysis, IDO expression was an independent prognostic factor for PFS (P ¼ 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.
Purpose: Tumor escape from host immune systems is a crucial mechanism for disease progression. We recently showed that the immunosuppressive enzyme indoleamine 2,3-dioxygenase (IDO) is a prognostic indicator for endometrial cancer. The purpose of the present study was to investigate the relationship between IDO expression and tumor-infiltrating lymphocytes (TIL) or natural killer (NK) cells and to clarify their prognostic effect in endometrial cancer. Experimental Design: Immunohistochemical staining for IDO expression in endometrial cancer tissues (n = 65) was done. Tumor-infiltrating CD3+ and CD8+ lymphocytes, as well as CD57+ NK cells, were counted in serial tissue sections. Results: High IDO expression in tumor cells was found in 32 of 65 cases and was positively correlated with myometrial invasion, nodal metastasis, and lymph-vascular space involvement. We also found a significant correlation between high IDO expression and reduced numbers of CD3+, CD8+, and CD57+ cells infiltrating into both the tumor epithelium and stroma. Patients with high IDO expression, a low number of stromal CD3 (<60), low intraepithelial CD8 (<25), or low stromal CD8 (<40) had significantly impaired progression-free survival. On multivariate analysis, IDO expression and the number of stromal CD3+ TILs were independent prognostic factors for impaired progression-free survival. Conclusions: Tumoral IDO expression correlated with a reduced number of TILs and NK cells in endometrial cancer, possibly contributing to disease progression and impaired clinical outcome. These findings suggest that targeting IDO to restore host antitumor immunity may be a therapeutic strategy for endometrial cancer.Tumor escape from host immune surveillance creates a state of ''tolerance'' and is a crucial mechanism for cancer progression (1). However, its underlying cellular and molecular basis remains poorly understood. Recent studies suggest that one mechanism that may contribute to this tolerance is the immunoregulatory enzyme indoleamine 2,3-dioxygenase (IDO; ref. 2).IDO is an intracellular enzyme that catalyzes the initial and rate-limiting steps in the metabolism of the essential amino acid tryptophan along the kynurenine pathway (3). Recently, evidence that indicates an immunosuppressive function for IDO has been accumulating. It was first found that IDO is expressed in the mouse placenta during pregnancy and prevents rejection of the allogeneic fetus, thereby suggesting involvement of IDO in fetal-maternal tolerance (4). Subsequent studies clarified the mechanism of IDO immunosuppression to be local depletion of tryptophan and/or production of toxic tryptophan catabolites, causing growth arrest and the apoptosis of alloreactive T cells or natural killer (NK) cells that are extremely sensitive to tryptophan shortage (5). The tryptophan-derived catabolite kynurenine also inhibits the expression of specific triggering receptors on NK cells and regulates NK-cell function (6).In malignancy, it was firstly shown that IDO is expressed by the tumor...
We have created a simple algorithm for automatically predicting the explicit solvent atom distribution of biomolecules. The explicit distribution is coerced from the three-dimensional (3D) continuous distribution resulting from a 3D reference interaction site model (3D-RISM) calculation. This procedure predicts optimal location of solvent molecules and ions given a rigid biomolecular structure and the solvent composition. We show examples of predicting water molecules near the KNI-272 bound form of HIV-1 protease and predicting both sodium ions and water molecules near the rotor ring of F-adenosine triphosphate (ATP) synthase. Our results give excellent agreement with experimental structure with an average prediction error of 0.39-0.65 Å. Further, unlike experimental methods, this method does not suffer from the partial occupancy limit. Our method can be performed directly on 3D-RISM output within minutes. It is extremely useful for examining multiple specific solvent-solute interactions, as a convenient method for generating initial solvent structures for molecular dynamics calculations, and may assist in refinement of experimental structures. © 2012 Wiley Periodicals, Inc.
Recent progress in the theory of molecular recognition in biomolecules is reviewed, which has been made based on the statistical mechanics of liquids or the RISM/3D-RISM theory during the last five years in the authors' group. The method requires just the structure of protein and the potential energy parameters for the biomolecules and solutions as inputs. The calculation is carried out in two steps. The first step is to obtain the pair correlation functions for solutions consisting of water and ligands based on the RISM theory. Then, given the pair correlation functions prepared in the first step, we calculate the 3D-distribution functions of water and ligands around and inside protein based on the 3D-RISM theory. The molecular recognition of a ligand by the protein is realized by the 3D-distribution functions: if one finds some conspicuous peaks in the distribution of a ligand inside protein, then the ligand is regarded as "recognized" by the protein. Some biochemical processes are investigated, which are intimately related to the molecular recognition of small ligands including water, noble gases, and ions by a protein.
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