Michio Fujie

Increased serum kynurenine/tryptophan ratio correlates with disease progression in lung cancer

BACKGROUND Indoleamine 2,3-dioxygenase (IDO) catalyzes the rate-limiting step of tryptophan (Trp) degradation along the kynurenine (Kyn) pathway. By depleting tryptophan, IDO is considered to be a fundamental immune escape mechanism for tumor cells. However, IDO expression in lung cancer has not been explored thoroughly. Thus, the present study investigated IDO activity determined by serum Trp and Kyn concentrations in lung cancer and the correlation between the IDO activity and clinical parameters. METHOD The concentrations of Trp and Kyn were measured simultaneously by liquid chromatography/electrospray ionization tandem mass spectrometry (LC-ESI/MS/MS) in the sera of 123 patients with lung cancer and 45 healthy controls. The IDO activity was estimated by calculating the serum Kyn-to-Trp ratio (Kyn/Trp ratio). RESULTS Trp concentrations were significantly lower in patients with lung cancer than in healthy controls (62.6+/-15.8microM vs. 71.1+/-11.8microM, respectively; p=0.0007), while Kyn concentrations were significantly higher in patients compared with the controls (2.82+/-1.17microM vs. 2.30+/-0.56microM, respectively; p=0.0036). The IDO activity determined by the Kyn/Trp ratio was significantly higher in the patients than in the controls (47.1+/-21.3 vs. 32.9+/-9.10, respectively; p<0.0001). In addition, patients in the advanced stages of lung cancer had significantly lower Trp concentrations and higher IDO activity than those in the early stages (p=0.0058 and p=0.0209, respectively). CONCLUSIONS IDO activity was increased in lung cancer patients, and higher IDO activity was associated with more advanced stages. These results suggest that increased IDO activity is involved in disease progression of lung cancer, possibly through its immunosuppressive effect.

Flux of the l-Serine Metabolism in Rabbit, Human, and Dog Livers SUBSTANTIAL CONTRIBUTIONS OF BOTH MITOCHONDRIAL AND PEROXISOMAL SERINE:PYRUVATE/ALANINE:GLYOXYLATE AMINOTRANSFERASE

l-Serine metabolism in rabbit, dog, and human livers was investigated, focusing on the relative contributions of the three pathways, one initiated by serine dehydratase, another by serine:pyruvate/alanine:glyoxylate aminotransferase (SPT/AGT), and the other involving serine hydroxymethyltransferase and the mitochondrial glycine cleavage enzyme system (GCS). Under quasi-physiological in vitro conditions (1 mm l-serine and 0.25 mmpyruvate), flux through serine dehydratase accounted for only traces, and that through SPT/AGT substantially contributed no matter whether the enzyme was located in peroxisomes (rabbit and human) or largely in mitochondria (dog). As for flux through serine hydroxymethyltransferase and GCS, the conversion of serine to glycine occurred fairly rapidly, followed by GCS-mediated slow decarboxylation of the accumulated glycine. The flux through GCS was relatively high in the dog and low in the rabbit, and only in the dog was it comparable with that through SPT/AGT. An in vivo experiment withl-[3-3H,14C]serine as the substrate indicated that in rabbit liver, gluconeogenesis froml-serine proceeds mainly via hydroxypyruvate. Because an important role in the conversion of glyoxylate to glycine has been assigned to peroxisomal SPT/AGT from the studies on primary hyperoxaluria type 1, these results suggest that SPT/AGT in this organelle plays dual roles in the metabolism of glyoxylate and serine.

Anti-metastatic therapy by urinary trypsin inhibitor in combination with an anti-cancer agent.

We have demonstrated that urinary trypsin inhibitor (UTI) purified from human urine is able to inhibit lung metastasis of mouse Lewis lung carcinoma (3LL) cells in experimental and spontaneous metastasis models. In this study, we have investigated whether UTI in combination with an anti-cancer drug, etoposide, can prevent tumour metastasis and show an enhanced therapeutic effect. Subcutaneous (s.c.) implantation of 3LL cells (1 x 10(6) cells) in the abdominal wall of C57BL/6 female mice resulted in macroscopic lung metastasis within 21 days. Microscopic lung metastasis was established by day 14 after tumour cell inoculation, and surgical treatment alone after this time resulted in no inhibition of lung metastasis. The number of lung tumour colonies in the group of mice which received surgery at day 21 was greater than in mice which had tumours left in situ (P = 0.0017). Surgical treatment on day 7, followed by UTI administration (s.c.) for 7 days, led to a decrease in lung metastasis compared with untreated animals. A significant inhibition of the formation of pulmonary metastasis was obtained with daily s.c. injections of UTI for 7 days immediately after tumour cell inoculation. UTI administration did not affect the primary tumour size at the time of operation. In addition, etoposide treatment alone led to a smaller primary tumours and yielded reduction of the formation of lung metastasis in the group of mice which received surgery at day 14 (P = 0.0026). Even in mice which received surgical treatment on day 14, followed by the combination of UTI (500 micrograms per mouse, days 14, 15, 16, 17, 18, 19 and 20) with etoposide (40 mg kg-1, days 14, 18 and 22), there was significant reduction of the formation of lung metastasis (P = 0.0001). Thus, the combination of an anti-metastatic agent with an anti-cancer drug, etoposide, might provide a therapeutically promising basis for anti-metastatic therapy.

Serum Indoleamine 2,3-Dioxygenase Activity Predicts Prognosis of Pulmonary Tuberculosis

ABSTRACT Tuberculosis (TB) continues to be a major health problem, and there are few biomarkers for predicting prognosis. Indoleamine 2,3-dioxygenase (IDO), a potent immunoregulatory molecule, catalyzes the rate-limiting step of tryptophan (Trp) degradation in the kynurenine (Kyn) pathway. An increase in IDO activity determined by the serum Trp/Kyn ratio has been shown to be associated with poor prognosis in cancers and bacteremia. In TB, however, there are no studies measuring serum IDO activity to determine its clinical significance. We evaluated serum IDO activity with 174 pulmonary TB (PTB) patients and 85 controls, using liquid chromatography/electrospray ionization tandem mass spectrometry. IDO activity was estimated by calculating the serum Kyn-to-Trp ratio. PTB patients had significantly higher Kyn concentrations and IDO activity and significantly lower Trp concentrations (P < 0.0001, P < 0.0001, and P < 0.0001, respectively) than the controls. Of 174 PTB patients, 39 (22.4%) died. The patients who died had significantly higher concentrations of Kyn and significantly lower Trp concentrations, resulting in significantly higher IDO activity (P < 0.0001, P < 0.0001, and P < 0.0001, respectively). In a receiver operating characteristic (ROC) analysis, serum IDO activity had the highest area under the curve (0.850), and this activity was an independent prognostic factor in multivariate analysis. These results suggest that serum IDO activity can be used as a novel prognostic marker in PTB.

Control of Oxalate Formation from L-Hydroxyproline in Liver Mitochondria

Serine:pyruvate/alanine:glyoxylate aminotransferase (SPT/AGT) is largely located in mitochondria in carnivores, whereas it is entirely found within peroxisomes in herbivores and humans. In rat liver, SPT/AGT is found in both of these organelles, and only the mitochondrial enzyme is markedly induced by glucagon. Although SPT/AGT is a bifunctional enzyme involved in the metabolism of both L-serine and glyoxylate, its contribution to L-serine metabolism is independent of mitochondrial or peroxisomal localization (Xue HH et al., J Biol Chem 274: 16028-16033, 1999). Therefore, the species-specific and food habit-dependent organelle distribution might be required for proper metabolism of glyoxylate at the subcellular site of its formation. Glyoxylate formation from glycolate and that from L-hydroxyproline have been shown to occur in peroxisomes and mitochondria, respectively. The present study found that urinary excretion of oxalate was markedly increased when a large dose of L-hydroxyproline or glycolate was administered to rats. Oxalate formation from L-hydroxyproline but not that from glycolate was significantly reduced when mitochondrial SPT/AGT had been induced by glucagon. The hydroxyproline content of collagen is 10 to 13%, and collagen accounts for about 30% of total animal protein; therefore, these results suggest that an important role of mitochondrial SPT/AGT in carnivores is to convert L-hydroxyproline-derived glyoxylate into glycine in situ, preventing undesirable overflow into the production of oxalate.

Flux of the l-Serine Metabolism in Rat Liver THE PREDOMINANT CONTRIBUTION OF SERINE DEHYDRATASE

l-Serine metabolism in rat liver was investigated, focusing on the relative contributions of the three pathways, one initiated by l-serine dehydratase (SDH), another by serine:pyruvate/alanine:glyoxylate aminotransferase (SPT/AGT), and the other involving serine hydroxymethyltransferase and the mitochondrial glycine cleavage enzyme system (GCS). Because serine hydroxymethyltransferase is responsible for the interconversion between serine and glycine, SDH, SPT/AGT, and GCS were considered to be the metabolic exits of the serine-glycine pool. In vitro, flux through SDH was predominant in both 24-h starved and glucagon-treated rats. Flux through SPT/AGT was enhanced by glucagon administration, but even after the induction, its contribution under quasi-physiological conditions (1 mm l-serine and 0.25 mm pyruvate) was about 1 10 of that through SDH. Flux through GCS accounted for only several percent of the amount ofl-serine metabolized. Relative contributions of SDH and SPT/AGT to gluconeogenesis from l-serine were evaluatedin vivo based on the principle that 3H at the 3 position of l-serine is mostly removed in the SDH pathway, whereas it is largely retained in the SPT/AGT pathway. The results showed that SPT/AGT contributed only 10–20% even after the enhancement of its activity by glucagon. These results suggested that SDH is the major metabolic exit of l-serine in rat liver.

Urinary trypsin inhibitor (UTI) and fragments derived from UTI by limited proteolysis efficiently inhibit tumor cell invasion

We investigated the effects of purified human urinary trypsin inhibitor (UTI) and fragments derived from UTI by proteolysis on the invasive potential of ovarian cancer cells (HOC-I) and gestational choriocarcinoma cells (SMT-ccl) using anin vitro reconstituted basement membrane invasion assay. These cells express cell-associated plasmin and functional uPA receptors that are partially occupied by ligands. SMT-ccl cells, which express threefold higher levels of cell-associated plasmin activity than HOC-I cells, showed approximately twofold increase in their invasive potential. For the invasion assay, HOC-I cells were primed with exogenous plasminogen, but SMT-ccl cells were not. Human leukocyte elastase (HLE)-digested UTI (22 kDa fragment; UTI-22) inhibited plasmin practically with the same strength as native UTI. Trypsindigested UTI (20 kDa fragment; UTI-20), however, did not inhibit plasmin significantly. Treatment of cells with UTI or UTI-22 reduced the incidence of tumor cell invasive capacity, whereas the inhibitory effect of UTI-20 was not remarkable. The inhibitory effect on tumor cell invasion was dose-dependent and non-toxic; moreover, it was not mediated by inhibition of the tumor cell chemotactic response or of cell attachment to matrigel. These results indicate that inhibition of the proteolytic enzyme plasmin specifically reduced the invasive capacity of tumor cellsin vitro.

Relationship between an increased serum kynurenine/tryptophan ratio and atherosclerotic parameters in hemodialysis patients

Essential amino acid tryptophan (Trp) is mainly catabolized by indoleamine 2,3‐dioxygenase, which leads to the formation of kynurenine (Kyn). In this study, we reexamined whether an increased indoleamine 2,3‐dioxygenase activity, as estimated by the Kyn/Trp ratio (μM/mM), is associated with atherosclerotic parameters in hemodialysis (HD) patients. Serum Trp and Kyn were measured in 243 HD patients by liquid chromatography/electrospray ionization tandem mass spectrometry. We measured carotid artery intima‐medial thickness, brachial‐ankle pulse wave velocity, ankle‐brachial pressure index, and the cardio‐ankle vascular index. Log‐transformed Kyn/Trp ratio was significantly correlated with log‐transformed time on HD (ρ=0.28, P<0.01), log‐transformed highly sensitive C‐reactive protein (ρ=0.20, P<0.01), and peripheral total lymphocyte count (ρ=−0.13, P<0.05). A significant association was found between log‐transformed Kyn/Trp ratio and mean carotid artery intima‐medial thickness (ρ=0.18, P<0.01). Mean carotid artery intima‐medial thickness was significantly higher in the lowest quartile of Kyn/Trp ratio (<165) (0.62±0.12 mm) when compared with the highest quartile (≥304) (0.68±0.15 mm) (P<0.01). Ankle‐brachial pressure index was lower in the second quartile (1.01±0.20), the third quartile (1.01±0.19), and the fourth quartile (1.03±0.15) compared with that in the first quartile (1.09±0.13) (P<0.05). It follows from these findings that the Kyn/Trp ratio increases with time on HD, and is associated with advanced atherosclerotic changes in chronic HD patients.

Identification and characterization of the cell-associated binding protein for urinary trypsin inhibitor

Urinary trypsin inhibitor (UTI) inhibits not only tumor cell invasion but also production of experimental and spontaneous metastasis. Cell-binding experiments indicated that human choriocarcinoma SMT-cc1 cells have specific binding sites for UTI on their cell surface. [Kobayashi et al., J. Biol. Chem. 269, 1994, 20,642-20,647]. UTI binding protein (UTIBP) was purified to homogeneity by a combination of UTI-coupled affinity beads, preparative polyacrylamide gel electrophoresis and reverse phase HPLC. This protein is very similar to a truncated form of human cartilage link protein (LP). LP was identified structurally by its apparent molecular mass with and without deglycosylation treatment: Immunologically by the reactivity with anti-UTIBP antibody, and functionally by its ability to bind the NH2-terminal domain of UTI. UTI and UTIBP are distributed uniformly in the cytoplasm and/or over the cell surface of tumor cells and fibroblasts. The level of staining for hyaluronic acid, UTIBP and UTI is much lower in sections digested with hyaluronidase. These results suggest that the cell membrane-derived UTI-associated binding protein is the LP of proteoglycan-hyaluronic acid aggregates, which interacts with hyaluronic acid. Cell-associated LP may play a role in modulating protease activity to the environment close to tumor and fibroblast cell surface.

Characterization of binding properties of urinary trypsin inhibitor to cell-associated binding sites on human chondrosarcoma cell line HCS-2/8.

Urinary trypsin inhibitor (UTI) forms membrane complexes with UTI-binding proteins (UTI-BPs) and initiates modulation of urokinase-type plasminogen activator (uPA) expression, which results in UTI-mediated suppression of cell invasiveness. It has been established that suppression of uPA expression and invasiveness by UTI is mediated through inhibition of protein kinase C-dependent signaling pathways and that human chondrosarcoma cell line HCS-2/8 expresses two types of UTI-BPs; a 40-kDa UTI-BP (UTI-BP40), which is identical to link protein (LP), and a 45-kDa UTI-BP (UTI-BP45). Here we characterize binding properties of UTI-BPs·UTI complexes in the cells. In vitro ligand blot, cell binding and competition assays, and Scatchard analyses demonstrate that both UTI-BP40 and UTI-BP45 bind125I-UTI. A deglycosylated form of UTI (NG-UTI), from which the chondroitin-sulfate side chain has been removed, binds only to UTI-BP40. Additional experiments, using various reagents to block binding of 125I-UTI and NG-UTI to the UTI-BP40 and UTI-BP45 confirm that the chondroitin sulfate side chain of UTI is required for its binding to UTI-BP45. Analysis of binding of125I-UTI and NG-UTI to the cells suggests that low affinity binding sites are the UTI-BP40 (which can bind NG-UTI), and the high affinity sites are the UTI-BP45. In addition, UTI-induced suppression of phorbol ester stimulated up-regulation of uPA is inhibited by reagents that were shown to prevent binding of UTI to the 40- and 45-kDa proteins. We conclude that UTI must bind to both of the UTI-BPs to suppress uPA up-regulation.