Structural-model-based genome mining can efficiently discover novel non-canonical terpene synthases hidden in genomes of diverse species.

Non-canonical terpene synthases (TPSs) with primary sequences that are unrecognizable as canonical TPSs have evaded detection by conventional genome mining. This study aimed to prove that novel non-canonical TPSs can be efficiently discovered from proteins, hidden in genome databases, predicted to have 3D structures similar to those of class I TPSs. Six types of non-canonical TPS candidates were detected using this search strategy from 268 genome sequences from actinomycetes. Functional analyses of these candidates revealed that at least three types were novel non-canonical TPSs. We propose classifying the non-canonical TPSs as classes ID, IE, and IF. A hypothetical protein MBB6373681 from Pseudonocardia eucalypti (PeuTPS) was selected as a representative example of class ID TPSs and characterized. PeuTPS was identified as a diterpene synthase that forms a 6/6/6-fused tricyclic gersemiane skeleton. Analyses of PeuTPS variants revealed that amino acid residues within new motifs [D(N/D), ND, and RXXKD] located close to the class I active site in the 3D structure were essential for enzymatic activity. The homologs of non-canonical TPSs found in this study exist in bacteria as well as in fungi, protists, and plants, and the PeuTPS gene is not located near terpene biosynthetic genes in the genome. Therefore, structural-model-based genome mining is an efficient strategy to search for novel non-canonical TPSs that are independent of biological species and biosynthetic gene clusters and will contribute to expanding the structural diversity of terpenoids.

Identification and functional/structural analyses of large terpene synthases.

Large terpene synthases (large-TSs) are a new family of TSs. The first large-TS discovered was from Bacillus subtilis (BsuTS), which is involved in the biosynthesis of a C35 sesquarterpene. Large-TSs are the only enzymes that enable the biosynthesis of sesquarterpenes and do not share any sequence homology with canonical Class I and II TSs. Thus, the investigation of large-TSs is promising for expanding the chemical space in the terpene field. In this chapter, we describe the experimental methods used for identifying large-TSs, as well as their functional and structural analyses. Additionally, several enzymes related to the biosynthesis of large-TS substrates have been described.

Analysis of vitamin D receptor binding affinities of enzymatically synthesized triterpenes including ambrein and unnatural onoceroids.

Onoceroids are a rare family of triterpenes. One representative onoceroid is ambrein, which is the main component of ambergris used as a traditional medicine. We have previously identified the onoceroid synthase, BmeTC, in Bacillus megaterium and succeeded in creating ambrein synthase by introducing mutations into BmeTC. Owing to the structural similarity of ambrein to vitamin D, a molecule with diverse biological activities, we hypothesized that some of the activities of ambergris may be induced by the binding of ambrein to the vitamin D receptor (VDR). We demonstrated the VDR binding ability of ambrein. By comparing the structure-activity relationships of triterpenes with both the VDR affinity and osteoclastic differentiation-promoting activity, we observed that the activity of ambrein was not induced via the VDR. Therefore, some of the activities of ambergris, but not all, can be attributed to its VDR interaction. Additionally, six unnatural onoceroids were synthesized using the BmeTC reactions, and these compounds exhibited higher VDR affinity than that of ambrein. Enzymatic syntheses of onoceroid libraries will be valuable in creating a variety of bioactive compounds beyond ambergris.

Identification and functional analysis of a new type of Z,E-mixed prenyl reductase from mycobacteria.

Isoprenoids with reduced Z,E-mixed prenyl groups are found in various organisms. To date, only polyprenol reductases (PR-Dol) involved in dolichol biosynthesis have been identified as enzymes capable of reducing Z,E-mixed prenyl groups. Although C35 -isoprenoids with reduced Z,E-mixed prenyl groups are found in mycobacteria, Z,E-mixed heptaprenyl reductase (HepR) remains unidentified. In the present study, the identification and functional analysis of HepR was performed. No PR-Dol homolog gene was detected in the genome of Mycolicibacterium vanbaalenii. However, a homolog of geranylgeranyl reductase (GGR), which reacts with an all-E prenyl group as a substrate, was encoded in the genome; thus, we analyzed it as a HepR candidate. In vitro enzymatic assay and in vivo gene suppression analysis identified the GGR homolog as HepR and revealed that HepR catalyzes the reduction of ω- and E- prenyl units in Z,E-mixed heptaprenyl diphosphates, and C35 -isoprenoids are mainly biosynthesized using E,E,E-geranylgeranyl diphosphate as a precursor. Thus, it was demonstrated that the Z,E-mixed prenyl reductase family exists in the GGR homologs. To the best of our knowledge, this is the first identification of a new type of Z,E-mixed prenyl reductase with no sequence homology to PR-Dol. The substrate specificity of HepR significantly differed from that of GGR, suggesting that it is a new enzyme. HepR homologs are widely distributed in mycobacterial genomes, and lipid analysis suggests that many strains, including pathogenic species, produce HepR metabolites. The discovery of this new enzyme will promote further research on Z,E-mixed isoprenoids.

Insight into Isoprenoid Biosynthesis by Functional Analysis of Isoprenyl Diphosphate Synthases from Mycobacterium vanbaalenii and Mycobacterium tuberculosis.

Comprehensive functional analyses of E-isoprenyl diphosphate synthases (E-IDSs) from nonpathogenic Mycobacterium vanbaalenii have been performed. Mv0992 and Mv1577 represent a nonaprenyl diphosphate (E-C45 ) synthase and a geranylgeranyl diphosphate (E-C20 ) synthase, respectively. Although Mv3536 was identified as an E-C20 synthase using a single enzyme, co-incubation of Mv3536 and Z-IDSs (Mv4662 and Mv3822) strongly suggested it releases an intermediate geranyl diphosphate (E-C10 ) during a continuous condensation reaction. Mv0992 and Mv3536 functions differed from those of the previously reported pathogenic Mycobacterium tuberculosis homologues Rv0562 and Rv2173, respectively. Re-analysis of Rv0562 and Rv2173 demonstrated that their functions were similar to those of Mv0992 and Mv3536 (Rv0562: E-C45 synthase; Rv2173: E-C10-15 synthase). The newly proposed functions of Rv0562 and Rv2173 would be in the biosynthesis of menaquinone and glycosyl carrier lipids essential for growth. Furthermore, a reduced allylic diphosphate could be used as the Z-IDS of the Mv3822 substrate, thereby introducing a potentially novel pathway of cyclic sesquarterpene biosynthesis.

Adduct Formation of Delamanid with NAD in Mycobacteria.

Delamanid (DLM), a nitro-dihydroimidazooxazole derivative currently approved for pulmonary multidrug-resistant tuberculosis (TB) therapy, is a prodrug activated by mycobacterial 7,8-didemethyl-8-hydroxy 5-deazaflavin electron transfer coenzyme (F420)-dependent nitroreductase (Ddn). Despite inhibiting the biosynthesis of a subclass of mycolic acids, the active DLM metabolite remained unknown. Comparative liquid chromatography-mass spectrometry (LC-MS) analysis of DLM metabolites revealed covalent binding of reduced DLM with a nicotinamide ring of NAD derivatives (oxidized form) in DLM-treated Mycobacterium tuberculosis var. Bacille de Calmette et Guérin. Isoniazid-resistant mutations in the type II NADH dehydrogenase gene (ndh) showed a higher intracellular NADH/NAD ratio and cross-resistance to DLM, which were restored by complementation of the mutants with wild-type ndh Our data demonstrated for the first time the adduct formation of reduced DLM with NAD in mycobacterial cells and its importance in the action of DLM.

High titers of both rheumatoid factor and anti-CCP antibodies at baseline in patients with rheumatoid arthritis are associated with increased circulating baseline TNF level, low drug levels, and reduced clinical responses: a post hoc analysis of the RISING study.

BACKGROUND: Although both rheumatoid factor (RF) and anticyclic citrullinated peptide antibodies (anti-CCP) are useful for diagnosing rheumatoid arthritis (RA), the impact of these autoantibodies on the efficacy of tumor necrosis factor (TNF) inhibitors has been controversial. The aim of this post hoc analysis of a randomized double-blind study (the RISING study) was to investigate the influences of RF and anti-CCP on the clinical response to infliximab in patients with RA. METHODS: Methotrexate-refractory patients with RA received 3 mg/kg of infliximab from weeks 0 to 6 and then 3, 6, or 10 mg/kg every 8 weeks from weeks 14 to 46. In this post hoc analysis, patients were stratified into three classes on the basis of baseline RF/anti-CCP titers: "low/low-C" (RF < 55 IU/ml, anti-CCP < 42 U/ml), "high/high-C" (RF ≥ 160 IU/ml, anti-CCP ≥ 100 U/ml), and "middle-C" (neither low/low-C nor high/high-C). Baseline plasma TNF level, serum infliximab level, and disease activity were compared between the three classes. RESULTS: Baseline RF and anti-CCP titers showed significant correlations with baseline TNF and infliximab levels in weeks 2-14. Comparison of the three classes showed that baseline TNF level was lowest in the low/low-C group and highest in the high/high-C group (median 0.73 versus 1.15 pg/ml), that infliximab levels at week 14 were highest in the low/low-C group and lowest in the high/high-C group (median 1.0 versus 0.1 µg/ml), and that Disease Activity Score in 28 joints based on C-reactive protein at week 14 was lowest in the low/low-C group and highest in the high/high-C group (median 3.17 versus 3.82). A similar correlation was observed at week 54 in the 3 mg/kg dosing group, but not in the 6 or 10 mg/kg group. Significant decreases in both RF and anti-CCP were observed during infliximab treatment. CONCLUSIONS: RF/anti-CCP titers correlated with TNF level. This might explain the association of RF/anti-CCP with infliximab level and clinical response in patients with RA. Baseline RF/anti-CCP titers may serve as indices that aid infliximab treatment. TRIAL REGISTRATION: ClinicalTrials.gov, NCT00691028 . Retrospectively registered on 3 June 2008.

Stratifying the risk of lymph node metastasis in undifferentiated-type early gastric cancer.

AIM: To study how lymph node metastasis (LNM) risk is stratified in undifferentiated-type early gastric cancer (undiff-EGC) dependent on combinations of risk factors. METHODS: Five hundred and sixty-seven cases with undiff-EGC undergoing gastrectomy with lymphadenectomy were examined retrospectively. Using clinicopathological factors of patient age, location, size, an endoscopic macroscopic tumor form, ulceration, depth, histology, lymphatic involvement (LI) and venous involvement (VI), LNM risk was examined and stratified by conventional statistical analysis and data-mining analysis. RESULTS: LNM was positive in 44 of 567 cases (7.8%). Univariate analysis revealed > 2 cm, protrusion, submucosal (sm), mixed type, LI and VI as significant prognostic factors and > 2 cm and LI-positive were independent factors by multivariate analysis. In preoperatively evaluable factors excluding LVI, sm and > 2 cm were independent factors. According to the depth and size, cases were categorized into the low-risk group [m and ≤ 2 cm, 0% (LNM incidence)], the moderate-risk group (m and > 2 cm, 5.6%; and sm and ≤ 2 cm, 6.0%), and the high-risk group (sm and > 2 cm, 19.3%). On the other hand, LNM occurred in 1.4% in all LI-negative cases, greatly lower than 28.2% in all LI-positive cases, and LNM incidence was low in LI-negative cases even in the moderate- and high-risk groups. CONCLUSION: LNM-related factors in undiff-EGC were depth and size preoperatively while those were LI and size postoperatively. Among these factors, LI was the most significantly correlated factor.

Prediction of clinical response after 1 year of infliximab therapy in rheumatoid arthritis based on disease activity at 3 months: posthoc analysis of the RISING study.

OBJECTIVE: To investigate the probability of clinical remission (REM) or low disease activity (LDA) after 1 year of infliximab (IFX) therapy based on disease activity at 3 months in patients with rheumatoid arthritis (RA). METHODS: Methotrexate-refractory patients with RA received 3 mg/kg of IFX at weeks 0, 2, and 6, followed by 3 mg/kg, 6 mg/kg, or 10 mg/kg every 8 weeks from Week 14 (W14) to Week 46. Correlation of disease activity at W14 with disease activity at W54 and probability of REM/LDA at W54 were analyzed in each dosing group. RESULTS: Disease activities at W14 were significantly correlated with both disease activity at W54 and probability of REM/LDA at W54 in patients continuing 3 mg/kg as well as in those receiving 6 mg/kg or 10 mg/kg therapy from W14. Results showed that, if approximate REM or LDA had not been achieved by W14, > 50% of patients continuing 3 mg/kg therapy would not be able to achieve REM or LDA at W54. However, even in patients with high or moderate disease activity at W14, dose escalation to 6 mg/kg or 10 mg/kg enabled many to achieve REM/LDA. CONCLUSION: Disease activity at W14 in standard-dose IFX therapy enabled the prediction of longterm clinical response at continued standard dose, as well as subsequent escalated-dose regimens. Disease activity at W14 was hypothesized to be an important index for IFX treatment strategy.

Phase III, multicenter, open-label, long-term study of the safety of abatacept in Japanese patients with rheumatoid arthritis and an inadequate response to conventional or biologic disease-modifying antirheumatic drugs.

OBJECTIVES: To examine the long-term safety of intravenous (IV) abatacept treatment in Japanese patients with rheumatoid arthritis (RA) and an inadequate response to methotrexate (MTX) or other conventional or biologic disease-modifying antirheumatic drugs. METHODS: This Phase III, open-label, long-term study (NCT00484289) comprised Japanese patients with RA who had completed abatacept Phase I or Phase II studies, and new patients intolerant to MTX. Patients from Phase I and Phase II studies received a weight-tiered dosing equivalent of 10 mg/kg abatacept, with MTX at doses up to 8 mg/week; newly enrolled patients received weight-tiered 10 mg/kg abatacept monotherapy. Safety and efficacy were assessed. RESULTS: A total of 217 patients (Phase I, n = 13; Phase II, n = 178; newly enrolled, n = 26) were treated with IV abatacept for a mean of 3 years. Serious adverse events occurred in 67/217 (30.9%) patients. Most adverse events were mild or moderate. For all cohorts combined, American College of Rheumatology 20% response rates ranged from 61.3 to 81.8% for as-observed and last observation carried forward analyses over 192 weeks. Following initial response, clinical and functional outcomes were maintained for up to 3 years. CONCLUSIONS: In Japanese patients with RA, IV abatacept with and without background MTX showed tolerable safety and sustained efficacy over 3 years.

Phase II dose-response study of abatacept in Japanese patients with active rheumatoid arthritis with an inadequate response to methotrexate.

OBJECTIVE: The objective of this study was to assess the response to abatacept at doses of 2 mg/kg and 10 mg/kg compared to placebo in patients with active rheumatoid arthritis (RA) with an inadequate clinical response to methotrexate (MTX). METHODS: In this multicenter, placebo-controlled, double-blind, parallel-group, dose-response study, 195 Japanese patients with active RA with an inadequate response to MTX were randomized 1:1:1 to receive 10 mg/kg or 2 mg/kg abatacept plus MTX, or placebo plus MTX, for 24 weeks. RESULTS: Abatacept demonstrated a dose-response relationship when given at 2 and 10 mg/kg. Based on the American College of Rheumatology criteria (20, 50, and 70 %), the responses to 10 mg/kg abatacept were significantly greater than those to placebo at week 24 (p < 0.001). Smaller yet statistically significant responses were also seen in the 2 mg/kg abatacept group. Overall rates of adverse events, serious adverse events, and treatment discontinuations because of adverse events were comparable in all three groups. CONCLUSIONS: Abatacept (2 mg/kg and 10 mg/kg) showed a dose-response relationship in Japanese patients with active RA with an inadequate clinical response to MTX. Administration of abatacept in combination with MTX for 24 weeks was well tolerated.

Tolerability and efficacy of abatacept in Japanese patients with rheumatoid arthritis: a phase I study.

OBJECTIVE: The primary objective of this study was to evaluate the tolerability of single and multiple doses of abatacept in Japanese patients with rheumatoid arthritis. Secondary objectives included evaluating its pharmacokinetics, pharmacodynamics, immunogenicity, and efficacy. METHODS: This dose-escalation, single- and multiple-dose, multicenter, open-label study was conducted at nine sites in Japan. Seven patients were enrolled at each of three dose levels (2, 8 and 16 mg/kg) and received a single intravenous dose of abatacept on day 1 of the single-dose phase. The multiple-dose phase, at the same dose, started once the patients had completed the single-dose phase and when it was confirmed that there were no safety issues. RESULTS: Twenty patients started the single-dose phase. Single and multiple doses of abatacept were well tolerated, and adverse events were of mild to moderate intensity. There were no discontinuations or deaths due to adverse events. The pharmacokinetics of abatacept were linear, with no notable accumulation. There were no immunogenic effects on the safety, efficacy, or pharmacokinetics of abatacept. Multiple doses of abatacept improved individual items of the American College of Rheumatology core set. CONCLUSION: Single and multiple doses of abatacept showed favorable tolerability and efficacy in Japanese patients with rheumatoid arthritis.

Regulatory mechanisms for the production of BAFF and IL-6 are impaired in monocytes of patients of primary Sjögren's syndrome.

INTRODUCTION: In this study, we investigated possible aberrations of monocytes from patients with primary Sjögren's syndrome (pSS). We focused on B-cell-activating factor of the TNF family (BAFF) and IL-6 because they are both produced by monocytes and are known to be involved in the pathogenesis of pSS. METHODS: Peripheral monocytes were prepared from both pSS patients and normal individuals. The cells were stimulated in vitro with IFN-γ, and the amounts of IL-6 and soluble BAFF (sBAFF) produced by the cells were quantitated. The effect of sBAFF itself on the production of IL-6 was also studied. To investigate the response of pSS monocytes to these stimuli, the expression levels of the genes encoding BAFF receptors and IL-6-regulating transcription factors were quantitated. RESULTS: Peripheral pSS monocytes produced significantly higher amounts of sBAFF and IL-6 than normal monocytes did, even in the absence of stimulation. The production of these cytokines was significantly increased upon stimulation with IFN-γ. The elevated production of IL-6 was significantly suppressed by an anti-BAFF antibody. In addition, stimulation of pSS monocytes with sBAFF induced a significant increase in IL-6 production. Moreover, the expression levels of a BAFF receptor and transcription factors regulating IL-6 were significantly elevated in pSS monocytes compared to normal monocytes. CONCLUSIONS: The results of the present study suggest that the mechanisms underlying the production of sBAFF and IL-6 are impaired in pSS monocytes. Our research implies that this impairment is due to abnormally overexpressed IL-6-regulating transcription factors and a BAFF receptor. These abnormalities may cause the development of pSS.

Baseline tumour necrosis factor alpha levels predict the necessity for dose escalation of infliximab therapy in patients with rheumatoid arthritis.

OBJECTIVES: To investigate the possible role of baseline plasma tumour necrosis factor alpha levels (baseline-TNF) on the clinical response to infliximab in patients with rheumatoid arthritis (RA). METHODS: Patients with RA refractory to methotrexate received 3, 6, or 10 mg/kg of infliximab every 8 weeks, in a randomised, double-blind manner: the RISING study. Clinical response (disease activity score in 28 joints based on C-reactive protein or American College of Rheumatology core set) at week 54 and serum infliximab levels were compared in three patient groups with low, intermediate, or high baseline-TNF (TNF-low, TNF-int, or TNF-high). RESULTS: In TNF-low patients, the clinical response to different doses of infliximab was comparable, whereas TNF-int patients exhibited a dose-dependent trend. In contrast, TNF-high patients (approximately 13% of the total patients) had a clinical response to 10 mg/kg significantly better than the response to 3 and 6 mg/kg of infliximab. In TNF-high patients, the median trough serum levels of infliximab were below the detection limit (<0.1 µg/ml) at 3 and 6 mg/kg but were greater than 2 µg/ml at 10 mg/kg, whereas the levels were approximately 1 µg/ml for each dosage group in TNF-low patients. CONCLUSION: In patients with RA, baseline-TNF is significantly associated with the clinical response to infliximab in patients with a high baseline-TNF. A higher dose of infliximab may be necessary in these patients, whereas lower doses of infliximab are sufficient for those with a low baseline-TNF. Baseline-TNF may be a useful measure for personalising the treatment of RA using infliximab.

Reduced expression of TCR zeta is involved in the abnormal production of cytokines by peripheral T cells of patients with systemic lupus erythematosus.

Accumulating evidence suggests that dysfunction of T cells underlies the pathogenesis of systemic lupus erythematosus (SLE). We revealed that SLE T cells produced an abnormally excessive amount of IFN-γin vitro upon stimulation through TCR, and the expression level of TCR zeta was significantly reduced. The production of IFN-γ by SLE T cells was negatively correlated with the expression level of TCR zeta. This correlation was abolished when the cells were stimulated with TPA and ionomycin, which bypass TCR and introduce signals directly into the cells, but the production of IFN-γ by SLE T cells remained abnormally elevated. Taken together, these data suggest that regulatory mechanisms not only for the expression of TCR zeta but also for the production of IFN-γ were impaired in SLE T cells. These impairments may be responsible for the aberrant responses of SLE T cells and partly involved in the development of SLE.

Impact of trough serum level on radiographic and clinical response to infliximab plus methotrexate in patients with rheumatoid arthritis: results from the RISING study.

This study is a prospective, randomized, double-blind study to compare the efficacy and safety of 10 mg/kg infliximab with those of 3 mg/kg infliximab treatment in methotrexate-refractory rheumatoid arthritis patients. After the patients received 3 mg/kg infliximab infusion at weeks 0, 2, and 6, they were randomly assigned to be administered 3, 6 or 10 mg/kg infliximab every 8 weeks from week 14 to 46. Mean American College of Rheumatology improvement (ACR-N) at week 54, the primary endpoint, was 51.3% and 58.3% for the 3 mg/kg and 10 mg/kg groups, respectively, with a statistically significant difference. Treatment with 10 mg/kg was found to be remarkably beneficial in patients who had not responded to three infusions with 3 mg/kg at week 10. The median changes in the modified Sharp score were 0.0 in the two groups. There were no significant differences in the incidences of adverse events between the groups. In patients who achieved better clinical response or greater inhibition of progression of joint damage, trough serum infliximab level was significantly higher than in patients who did not. The magnitudes of both efficacies were correlated with the trough serum infliximab level (ClinicalTrials.gov number: NCT00691028).

Effect of interleukin-2 on synthesis of B cell activating factor belonging to the tumor necrosis factor family (BAFF) in human peripheral blood mononuclear cells.

B cell activating factor belonging to the tumor necrosis factor family (BAFF) is a cytokine, indispensable for B cell survival, maturation, and activation. Over-expression of BAFF leads to lupus like disease in mice and the serum level of BAFF is elevated in human lupus. However, little is known about BAFF synthesis and its regulation. In this study, we examined the effects of a series of inflammatory cytokines on BAFF production in human peripheral blood mononuclear cells (PBMCs) in vitro. We found interleukin-2 (IL-2) strongly and dose-dependently stimulated BAFF synthesis in PBMCs, and an anti-IL-2 antibody neutralized the effect. Furthermore, T and NK cells produced BAFF with IL-2 stimulation. From these observations, IL-2 is one of the regulatory cytokines having a positive effect on BAFF synthesis in human peripheral T and NK cells. Persistent over-production of IL-2 might lead to up-regulation of BAFF synthesis in PBMCs in pathological conditions such as lupus.

Conservative sequences in 3'UTR of TCRzeta mRNA regulate TCRzeta in SLE T cells.

We have demonstrated that T-cell receptor zeta (zeta) mRNA with a 562-bp deleted alternatively spliced 3'-untranslated region (3'UTR) observed in T cells of patients with systemic lupus erythematosus (SLE) can lead to a reduction in zeta and TCR/CD3 (J. Immunol., 2003 & 2005). To determine the region in zeta mRNA 3'UTR for the regulation of zeta, zeta mRNA with 3'UTR truncations ligated into pDON-AI was used to infect murine T-cell hybridoma MA5.8 cells, which do not contain zeta. As a Western blot analysis demonstrated the importance of the regions from +871 to +950, containing conservative sequence 1 (CS1), and +1070 to +1136, containing CS2, for the production of zeta, we constructed MA5.8 mutants carrying zeta mRNA 3'UTR with deletions of these regions (DeltaCS1 and DeltaCS2 mutants). Western blot and FACS analyses showed significant reduction in the cell surface zeta and TCR/CD3 in both these mutants, and IL-2 production was decreased, compared with MA5.8 cells transfected with wild-type zeta mRNA. Furthermore, real-time PCR demonstrated the instability of zeta mRNA with 3'UTR deletions in these MA5.8 mutants. In conclusion, CS1 and CS2 may be responsible for the regulation of zeta and TCR/CD3 through the stability of zeta mRNA in SLE T cells.

Down-regulation of Fas-ligand mRNA in Sjögren's syndrome patients with enlarged exocrine glands.

We have reported that Sjögren's syndrome (SS) patients with enlarged exocrine glands (EEG) formerly referred to as Mikulicz's disease were defective with Fas-ligand (FasL) expression in PBL and lacrimal glands (LGs). To investigate the mechanisms of reduced FasL expression in SS patients with EEG, FasL mRNA expression level was determined using real-time PCR. The FasL gene promoter region (from - 1197 to - 3) was also amplified using PCR and specific primers. Expression of the FasL mRNA in the LGs and PBLs of three SS patients with EEG was significantly decreased. Direct sequencing revealed a heterozygous point mutation ( - 259T/C) in the FasL gene promoter region in one SS patient with EEG. A luminescent beta-galactosidase (beta-gal) reporter assay using a pbetagal Enhancer Vector demonstrated that beta-gal activity from the vector including the mutant ( - 259C) FasL (pbetagal/mFasL) gene promoter region (735 +/- 42) was similar (p = 0.13) to that from a pbetagal Enhancer Vector without the gene promoter region (603 +/- 66). On the other hand, the beta-gal activity was significantly lower (p < 0.0001) than that from a vector including the wild-type ( - 259T) FasL (pbetagal/wFasL) (3226 +/- 148). In conclusion, the down-regulation of FasL in SS patients with EEG may be due to transcriptional regulation, and the point mutation at - 259T/C in the FasL gene promoter region may lead to the down-regulation of FasL mRNA expression and the lymphoproliferative process observed in SS patients with EEG.