Intratumoral reciprocal expression of monocarboxylate transporter 4 and glypican-3 in hepatocellular carcinomas.

OBJECTIVE: We previously reported the identification of monocarboxylate transporter 4 (MCT4) and glypican-3 (GPC3) as prognostic factors for hepatocellular carcinoma (HCC), which are now considered significant poor prognostic factors for the disease. This study aimed to clarify the detailed interaction of these two factors in HCC to improve our understanding of aggressive HCC phenotypes. A total of 225 Japanese patients with HCC from our previous study were subjected to immunohistochemical analyses. RESULTS: The number of MCT4-positive (MCT4+) HCC cases was 47 (21%), and most MCT4+ HCC showed high GPC3 expression (94%, 44/47 cases). In 44 MCT4+/GPC3+ HCC cases, intratumoral heterogeneity of GPC3 or MCT4 expression was further evaluated. We observed reciprocal (inverse), synergistic, mixed reciprocal and synergistic, or irrelevant interaction of MCT4 and GPC3 expression in 29 (66%), 5 (11%), 1 (2%), and 9 cases (21%), respectively. The cases exhibiting reciprocal expression of both markers tended to have cirrhosis without a history of neoadjuvant therapy. In summary, although MCT4+ HCC cases are mostly GPC3+, intratumoral expression patterns of MCT4 and GPC3 are frequently reciprocal each other, suggesting that dual targeting of MCT4 and GPC3 may achieve a better antitumor effect for MCT4+ HCC cases.

Case-control Indian buffet process identifies biomarkers of response to Codrituzumab.

BACKGROUND: Codrituzumab, a humanized monoclonal antibody against Glypican-3 (GPC3), which is expressed in hepatocellular carcinoma (HCC), was tested in a randomized phase II trial in advanced HCC patients who had failed prior systemic therapy. Biomarker analysis was performed to identify a responder population that benefits from treatment. METHODS: A novel statistical method based on the Indian buffet process (IBP) was used to identify biomarkers predictive of response to treatment with Codrituzumab. The IBP is a novel method that allows flexibility in analysis design, and which is sensitive to slight, but meaningful between-group differences in biomarkers in very complex datasets RESULTS: The IBP model identified several subpopulations of patients having defined biomarker values. Tumor necrosis and viable cell content in the tumor were identified as prognostic markers of disease progression, as were the well-known HCC prognostic markers of disease progression, alpha-fetoprotein and Glypican-3 expression. Predictive markers of treatment response included natural killer (NK) cell surface markers and parameters influencing NK cell activity, all related to the mechanism of action of this drug CONCLUSIONS: The Indian buffet process can be effectively used to detect statistically significant signals with high sensitivity in complex and noisy biological data TRIAL REGISTRATION: NCT01507168 , January 6, 2012.

Combining expression of GPC3 in tumors and CD16 on NK cells from peripheral blood to identify patients responding to codrituzumab.

BACKGROUND: Codrituzumab, a monoclonal antibody targeting an oncofetal protein glypican-3 (GPC3) expressed on cell surface of hepatocellular carcinoma (HCC) induces antibody-dependent cellular cytotoxicity (ADCC) and inhibits tumor growth in preclinical studies. Based on this mechanism, tumor GPC3 expression and CD16 expression on NK cells, which are the effector cells of ADCC, were investigated to correlate with codrituzumab's clinical efficacy in patients with advanced HCC. RESULTS: Joint analyses of the two biomarkers revealed that both high levels of GPC3 and CD16 were required for patients to benefit from codrituzumab; lack of either one of them would lead to a loss of the therapeutic effect. CONCLUSIONS: These results suggest the combination of tumor GPC3 expression and CD16 expression on NK cells from peripheral blood at baseline as a composite biomarker to select HCC patients for codrituzumab. IMPACT: The conclusion warrants a future study in an HCC population with both high GPC3 expression and high levels of CD16 at baseline to establish codrituzumab's therapeutic benefit in HCC. METHODS: Data from a phase II clinical trial of codrituzumab were used for the analyses. GPC3 expression in baseline tumor biopsies was determined by immunohistochemistry (IHC) analysis, and baseline CD16 expression on NK cells were quantified by peripheral blood lymphocyte immunophenotyping. According to high or low expression of GPC3 and CD16, different patient subgroups were formed; for each subgroup, overall survival of patients having high codrituzumab exposure was compared to that of patients receiving placebo.

I-124 codrituzumab imaging and biodistribution in patients with hepatocellular carcinoma.

BACKGROUND: I-124 codrituzumab (aka GC33), an antibody directed at Glypican 3, was evaluated in patients with hepatocellular carcinoma (HCC). Fourteen patients with HCC underwent baseline imaging with I-124 codrituzumab (~ 185 MBq, 10 mg). Seven of these patients undergoing sorafenib/immunotherapy with 2.5 or 5 mg/kg of cold codrituzumab had repeat imaging, with co-infusion of I-124 codrituzumab, as part of their immunotherapy treatment. Three patients who progressed while on sorafenib/immunotherapy were re-imaged after a 4-week washout period to assess for the presence of antigen. Serial positron emission tomography (PET) imaging and pharmacokinetics were performed following I-124 codrituzumab. An ELISA assay was used to determine "cold" codrituzumab serum pharmacokinetics and compare it to that of I-124 codrituzumab. Correlation of imaging results was performed with IHC. Short-term safety assessment was also evaluated. RESULTS: Thirteen patients had tumor localization on baseline I-124 codrituzumab; heterogeneity in tumor uptake was noted. In three patients undergoing repeat imaging while on immunotherapy/sorafenib, evidence of decreased I-124 codrituzumab uptake was noted. All three patients who underwent imaging after progression while on immunotherapy continued to have I-124 codrituzumab tumor uptake. Pharmacokinetics of I-124 codrituzumab was similar to that of other intact IgG. No significant adverse events were observed related to the I-124 codrituzumab. CONCLUSIONS: I-124 codrituzumab detected tumor localization in most patients with HCC. Pharmacokinetics was similar to that of other intact iodinated humanized IgG. No visible cross-reactivity with normal organs was observed.

Time-to-event modelling of effect of codrituzumab on overall survival in patients with hepatocellular carcinoma.

AIMS: Codrituzumab (GC33) is a recombinant, humanized mAb that binds to glypican-3 (GPC3), an oncofetal protein highly expressed in hepatocellular carcinoma (HCC). This investigation aimed to identify clinically relevant factors that may affect the overall survival (OS) in HCC patients treated with codrituzumab and to quantitatively annotate their effects. METHODS: Codrituzumab exposure was estimated by a population pharmacokinetics model with a nonlinear elimination pathway. Analysis of OS was performed using a time-to-event model in 181 patients with advanced HCC. The model was tested with the addition of various covariates, including levels of immune biomarkers, such as CD16 (measured in terms of molecules of equivalent soluble fluorophore; CD16MESF ) and CD4, codrituzumab exposure and potential prognostic biomarkers of HCC such as baseline tumour size and soluble GPC3. RESULTS: The time-to-event model estimated a prolonged OS (>3 months) in patients with codrituzumab exposure of ≥230 µg ml-1 and high CD16MESF level (>5.26 × 105 MESF at least). The Weibull model was selected as the base hazard model. The baseline tumour size was included in the hazard model as a parameter independent of the drug effect. A logistic model was applied to explain the effects of drug exposure and CD16MESF level. CONCLUSIONS: The final model indicates that adequate drug exposure plus a favourable immune environment are associated with prolonged OS. This quantitative model should be further validated with emerging data so as to guide study design in future clinical trials.

Phase Ib study of codrituzumab in combination with sorafenib in patients with non-curable advanced hepatocellular carcinoma (HCC).

PURPOSE: Codrituzumab, a humanized antibody against glypican-3, is highly expressed in HCC. A phase I study evaluated the combination with sorafenib in HCC. PATIENTS AND METHODS: In a 3 + 3 design, codrituzumab was given intravenously in various doses with sorafenib 400 mg twice daily to patients with advanced HCC, age ≥18, ECOG 0-1, Child-Pugh A and B7, adequate organ functions, and no prior systemic therapy, with tumor assessment by RECIST 1.0 and safety by CTCAE 3.0. PK and pre, during, and post-therapy 124I radiolabeled codrituzumab PET scan imaging were performed. RESULTS: 41 patients were enrolled: 2.5 mg/kg weekly (qw) (12), 5 mg/kg qw (12), 10 mg/kg qw (3), 1600 mg every 2 weeks (q2w) (6), and 1600 mg qw (7). Two drug limiting toxicities occurred: grade 3 hyponatremia at 5 mg/kg and grade 3 hyponatremia and hyperglycemia at 1600 mg q2w. Adverse events occurred in 80% of patients, including at least one ≥grade 3: ten (25%) increased AST, three (7.5%) increased ALT, and ten (25%) increased lipase. There were no responses and nine (25.7%) had stable disease. PK C max and AUCt of codrituzumab and sorafenib were comparable to single-agent data. Thirteen out of 14 patients showed 124I radiolabeled codrituzumab uptake in tumor. In all three patients who underwent a post-progression PET, glypican-3 remained expressed. CONCLUSION: Codrituzumab plus sorafenib were tolerated at 1600 mg q2w and 400 mg bid, respectively, with no responses. Codrituzumab exerts selective distribution to HCC cells, and GPC3 does not show any down-regulation post-progression (NCT00976170).

Evaluating clinical and prognostic implications of Glypican-3 in hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is one of the most deadly cancers worldwide. In patients with HCC, histopathogical differentiation is an important indicator of prognosis; however, because determination of HCC differentiation is difficult, the recently described immunohistochemical (IHC) marker glypican3 (GPC3) might assist in HCC prognostication.The goal of our study was to investigate GPC3's IHC staining pattern and define the relationship between its expression and patients' clinicopathologic features and overall survival. We retrieved clinical parameters from 101 pathologically diagnosed HCC patients' medical records and classified these patients into 4 clinical score categories (0-3) based on increasing GPC3 staining intensity and the percentage of stained tumor cells in their resection and biopsy specimens. Histopathological samples were well, moderately, and poorly differentiated in 33, 22, and 12 patients, respectively, and the GPC3 expression rate was 63%, 86%, and 92%,respectively. The median overall survival was 49.9 months (confidence interval (CI): 35.3-64.6 months) for clinical scores 0-1 and 30.7 months (CI: 19.4-41.9 months) for clinical scores 2-3. This difference was not statistically significant (P = .06) but showed a strong trend. In conclusion, a greater GPC3 expression is associated with a worse HCC prognosis and may be a promising prognostic marker.

Randomized phase II placebo controlled study of codrituzumab in previously treated patients with advanced hepatocellular carcinoma.

BACKGROUND & AIMS: Codrituzumab, a humanized monoclonal antibody against Glypican-3 (GPC3) that is expressed in hepatocellular carcinoma (HCC), interacts with CD16/FcγRIIIa and triggers antibody-dependent cytotoxicity. Codrituzumab was studied vs. placebo in a randomized phase II trial in advanced HCC patients who had failed prior systemic therapy. METHODS: Patients with advanced HCC who had failed prior systemic therapy, ⩾18years, Eastern cooperative oncology group (ECOG) 0-1, Child-Pugh A were randomized 2:1 to biweekly codrituzumab 1600mg vs. placebo. Patients were stratified based on GPC3 immunohistochemical expression: 2+/3+, 1+, and 0. Primary endpoint was progression free survival. Secondary endpoints include overall survival (OS), tolerability, pharmacokinetics, and an exploratory endpoint in biomarkers analysis. RESULTS: 185 patients were enrolled: 125 received codrituzumab and 60 placebo: Median age 64/63, 85/75% male, 46/42% Asian, ECOG 0 65/63%, 74/77% having vascular invasion and/or extra-hepatic metastasis. 84%/70% had prior sorafenib. Drug exposure was 98.4% of planned dose, with an identical adverse events profile between the 2 groups. The median progression free survival and overall survival in the codrituzumab vs. placebo groups in months were: 2.6 vs. 1.5 (hazard ratios 0.97, p=0.87), and 8.7 vs. 10 (hazard ratios 0.96, p=0.82). Projected Ctrough at cycle 3day 1 based exposure, high CD16/FcγRIIIa on peripheral immune cells, and GPC3 expression in the tumor, were all associated with prolonged progression free survival and overall survival. CONCLUSIONS: Codrituzumab did not show clinical benefit in this previously treated HCC population. Whether higher codrituzumab drug exposure or the use of CD16 and GPC3 as potential biomarkers would improve outcome remain unanswered questions. LAY SUMMARY: Codrituzumab is a manufactured antibody against a liver cancer protein called glypican-3. In this clinical trial, codrituzumab was not found be effective against liver cancer. It was suggested though that a higher dose of codrituzumab or selecting patients with high level of glypican-3 or its mediator CD16 might improve outcome. CLINICAL TRIAL REGISTRATION: This trial is registered at Clinicaltrials.gov (NCT01507168).

High preoperative levels of serum glypican-3 containing N-terminal subunit are associated with poor prognosis in patients with hepatocellular carcinoma after partial hepatectomy.

Glypican-3 (GPC3) is a glycosylphosphatidylinositol-anchored cell surface glycoprotein overexpressed in hepatocellular carcinoma (HCC) cells and may serve as a potential molecular target for therapeutic intervention. This study evaluated the prognostic significance of serum GPC3 in HCC patients receiving curative surgery. A novel sandwich enzyme-linked immunosorbent assay for the quantitative and sensitive determination of serum GPC3 N-terminal subunit antigen (sGPC3N) was developed and used to measure sGPC3N levels in 25 healthy volunteers and 115 HCC patients who underwent curative partial hepatectomy. The relationships between sGPC3N and clinicopathologic features were analyzed and the prognostic impact on overall survival (OS) or disease-free survival (DFS) was also investigated. Mean and median levels of sGPC3N in healthy controls were 110.12 and 115.95 pg mL(-1) , respectively, with 185.52 pg mL(-1) (mean + 2 SD) being set as the upper limit of the normal range. In HCC patients, sGPC3N levels were significantly increased (mean/median, 405.16/236.19 pg mL(-1) ) compared to healthy controls (p < 0.0001), and 60% of HCC cases (69/115) showed sGPC3N levels that were higher than the upper normal limit. High sGPC3N levels were significantly associated with serum AFP level, high Child-Pugh score and positive HCV. Kaplan-Meier analysis indicated that elevated pre-operative sGPC3N was associated with shorter OS and DFS after hepatectomy (p ≤ 0.01). Multivariate analysis revealed elevated sGPC3N as an independent poor prognostic marker for OS (p < 0.05) and DFS (p < 0.01). The pre-operative sGPC3N level serves as an independent prognostic biomarker in HCC patients.

Circulating biomarkers in hepatocellular carcinoma.

PURPOSE: Our aims are to determine levels of circulating cellular and protein biomarkers in hepatocellular carcinoma (HCC) patients and to analyse any relationships with clinical parameters. METHODS: Fifty-four consenting patients were recruited. Circulating tumour cells (CTCs) were enumerated (by CellSearch) and characterised via filtration [by isolation by size of epithelial tumour cells (ISET)] with downstream immunohistochemistry (IHC). Glypican-3 (GPC3) expression in tumour biopsies and CTCs (by IHC) was compared, and levels of circulating caspase-cleaved and full-length cytokeratin 18 (CK18, measured using M30 and M65 ELISAs) were examined as a putative prognostic factor and marker of tumour burden. RESULTS: CTCs were identified in 14 out of 50 (28%) patients by CellSearch and in 19 out of 19 (100%) patients by ISET. The presence of GPC3-positive CTCs by ISET was 100% concordant with the presence of GPC3-positive cells in the original tumour (n = 5). No statistically significant correlations were observed between CTC number and clinical characteristics, although trends were noted between CTC subtypes, Child-Pugh score and tumour node metastasis stage. Serum M30 and M65 levels (as continuous variables) significantly correlated with overall survival (OS) in a univariate analysis (p = 0.003 and p < 0.001, respectively); M65 levels remained statistically significant in a multivariate analysis (p = 0.029). CONCLUSIONS: This is the first study to detect GPC3-positive CTCs in HCC, important for drug development with this target. The significant association of circulating CK18 with OS in HCC further exemplifies the utility of circulating biomarkers in cancer.

Aberrant expression of monocarboxylate transporter 4 in tumour cells predicts an unfavourable outcome in patients with hepatocellular carcinoma.

BACKGROUND & AIMS: The tumour cell microenvironment, which includes local oxygen saturation, pericellular pH and stromal cells, can modulate tumour progression. This study determined the prognostic impact of infiltrating tumour-associated macrophages and the expression of monocarboxylate transporter 4 (MCT4) and glypican 3 (GPC3) in hepatocellular carcinoma (HCC) clinical specimens. METHODS: A total of 225 cases of resected HCC were subjected to immunohistochemical analyses of CD68, CD204, MCT4 and GPC3. Immunoreactivities and other common clinicopathological parameters were subjected to univariate prognostic analyses for overall survival (OS, n = 225) and disease-free survival (DFS, n = 222). All variables with prognostic impact were further analysed in multivariate analysis. RESULTS: Increased intratumoural infiltration of CD204-positive or MCT4-positive macrophages suggested shorter OS (P = 0.015 or P = 0.001 respectively), but DFS was not altered. The GPC3 score (with an emphasis on circumferential immunoreactivity) was correlated with shorter OS and DFS. Aberrant expression of MCT4 in HCC cells was observed in a subset of HCC cases (21%, 47/225). In those cases, significantly poorer OS (P < 0.0001) and DFS (P = 0.0003) were observed, and there was a positive correlation with the intratumoural infiltration of CD204- or MCT4-positive macrophages and the GPC3 score. Multivariate analysis showed that aberrant MCT4 expression in HCC cells was an independent prognostic factor for shorter OS (P = 0.018) and DFS (P = 0.006) after resection of HCC. CONCLUSION: Aberrant expression of MCT4 in carcinoma cells serves as a novel, independent prognostic factor for HCC, indicating a poorer patient outcome.

First-in-man phase I study of GC33, a novel recombinant humanized antibody against glypican-3, in patients with advanced hepatocellular carcinoma.

PURPOSE: GC33 is a novel recombinant fully humanized monoclonal antibody that binds to human glypican-3 (GPC3). The antitumor activity of GC33 was shown in preclinical models of hepatocellular carcinoma (HCC). This first-in-man clinical trial was conducted to evaluate the safety, pharmacokinetic characteristics, and preliminary efficacy of GC33 in patients with advanced HCC. EXPERIMENTAL DESIGN: Patients with measurable, histologically proven, advanced HCC were enrolled to a dose-escalation study of GC33 (2.5-20 mg/kg) given intravenously weekly. The primary endpoint was to determine the maximum tolerated dose of GC33 for further development. Pharmacokinetic characteristics were measured in serum samples. Immunohistochemistry was conducted on tumor biopsies to evaluate GPC3 expression. Tumor response was assessed every 8 weeks using Response Evaluation Criteria in Solid Tumors criteria. RESULTS: Twenty patients were enrolled and treated with GC33. A maximum tolerated dose was not reached as there were no dose-limiting toxicities (DLT) up to the highest planned dose level. Common adverse events with all grades included fatigue (50%), constipation (35%), headache (35%), and hyponatremia (35%). The incidence of adverse events seemed not to be dose dependent. Trough serum concentrations at steady state were in excess of target concentration at doses of 5 mg/kg or greater. Median time to progression (TTP) was 26.0 weeks in the GPC3 high expression group and 7.1 weeks in the low expression group (P = 0.033). CONCLUSION: This study shows that GC33 was well tolerated in advanced HCC and provides preliminary evidence that GPC3 expression in HCC may be associated with the clinical benefit to GC33 that warrants prospective evaluation.

Prognostic significance of circumferential cell surface immunoreactivity of glypican-3 in hepatocellular carcinoma.

BACKGROUND: GC33 is a recently developed monoclonal antibody against human glypican-3 (GPC3), which is significantly upregulated in hepatocellular carcinoma (HCC). GC33 recognizes a GPC3 ectodomain and shows significant antitumour activity in vivo. Thus, humanized GC33 antibody may be a promising tool for treating HCC having cell surface GPC3 expression. AIMS: This study aims to determine the specificity, subcellular localization and prognostic impact of GPC3 immunoreactivity detected by GC33 in HCC clinical specimens. METHODS: Immunohistochemical analysis was performed for 194 cases of resected HCC and prognostic analysis was performed for 185 eligible cases. Two antigen retrieval methods (autoclave and protease pretreatments) were used for immunohistochemistry and compared. The immunoscore system reflecting circumferential membranous GPC3 immunoreactivity was developed using either the autoclave or protease methods. The GPC3 mRNA level was analysed by quantitative real-time reverse transcription-polymerase chain reaction. RESULTS: GC33 immunostaining after autoclave is a sensitive method and revealed the GPC3 expression (≥20% of tumour cells) in the majority (77%) of HCC samples tested. Alternatively, protease pretreatment showed lower sensitivity, but was superior for evaluating the intensity and subcellular localization of GPC3. Correlation between immunoscores and the GPC3 mRNA level was also confirmed. Subsequent clinicopathological analysis revealed worse prognoses in HCC patients with circumferential membranous GPC3 immunoreactivity. For HCC patients with hepatitis C virus (HCV) infection in particular, the high membranous GPC3 immunoreactivity was an independent prognostic factor for disease-free survival. CONCLUSIONS: Circumferential membranous GPC3 immunoreactivity in HCC indicates poorer prognosis particularly in patients with HCV infection.

Viral envelope protein gp64 transgenic mouse facilitates the generation of monoclonal antibodies against exogenous membrane proteins displayed on baculovirus.

We have been investigating the functional display of multipass membrane protein such as transporter or G-protein coupled receptor on the budded baculovirus (BV). We tested the use of a viral envelope protein gp64 transgenic mouse for the direct immunization of these membrane proteins displayed on BVs. The gp64 transgenic mice showed only a weak response to virus compared to wild type BALB/c mice. Immunizing gp64 transgenic mice with the BV expressing peptide transporter PepT1, we obtained 47 monoclonal antibodies (mAbs). These mAbs were specific to the PepT1 on the pancreatic cancer cells AsPC-1 by fluorocytometric analysis and exhibited antibody-dependent cellular cytotoxicity or complement-dependent cytotoxicity to AsPC-1. We also generated 7 mAbs by immunizing gp64 transgenic mice on a CCR2-deficient background with the BV expressing chemokine receptor CCR2 together with partially purified CCR2. These mAbs possessed specific binding to CCR2 in CHO cells on fluorocytometric analysis, and exhibited neutralizing activities for ligand-dependent inhibition of cyclic AMP production. This method provides a powerful tool for the generation of therapeutic/diagnostic mAbs against membrane proteins.

Identification of ROBO1 as a novel hepatocellular carcinoma antigen and a potential therapeutic and diagnostic target.

PURPOSE: Hepatocellular carcinoma is the most common primary malignancy of the liver and accounts for as many as one million deaths annually worldwide. The present study was done to identify new transmembrane molecules for antibody therapy in hepatocellular carcinoma. EXPERIMENTAL DESIGN: Gene expression profiles of pooled total RNA from three tissues each of moderately differentiated and poorly differentiated hepatocellular carcinoma were compared with those of normal liver, noncancerous liver tissue in hepatocellular carcinoma patients, 30 normal tissue samples, and five fetal tissue samples. Target genes up-regulated specifically in hepatocellular carcinoma were validated by immunohistochemical analysis and complement-dependent cytotoxicity assay using monoclonal antibodies generated against target molecules. RESULTS: The human homologue of the Drosophila Roundabout gene, axon guidance receptor homologue 1, ROBO1/DUTT1, a member of the immunoglobulin superfamily, was highly expressed in hepatocellular carcinoma, whereas it showed only a limited distribution in normal tissues. On immunohistochemical analysis using a newly generated anti-ROBO1 monoclonal antibody, positive signals were observed in 83 of 98 cases of hepatocellular carcinoma (84.7%). The mAb B2318C induced complement-dependent cytotoxicity in ROBO1-expressing cell lines and in the liver cancer cell line PLC/PRF/5. Strikingly, the ectodomain of ROBO1 was detected not only in the culture medium of liver cancer cell lines (PLC/PRF/5, HepG2, etc.) but also in sera from hepatocellular carcinoma patients (6 of 11). CONCLUSIONS: This is the first report that ROBO1 is overexpressed in hepatocellular carcinoma and shed into serum in humans. These observations suggest that ROBO1 is a potential new serologic marker for hepatocellular carcinoma and may represent a new therapeutic target.

Recovery of functional peptide transporter PepT1 in budded baculovirus fraction.

Transporters play a critical role in many physiological and pathological states and expression of the functional transporter protein is essential in exploring its kinetics and developing effective drugs. We describe here the recovery of functional transporter protein in the baculovirus fraction. We introduced a gene encoding human peptide transporter PepT1, important for the absorption of protein hydrolytic products or peptide-mimetic drugs, into a baculovirus vector. After infection, a large amount of PepT1 appeared in the budded virus fraction compared with Sf9 cells. Uptake of [14C]glycylsarcosine was markedly increased in an acidic condition and showed a clear overshoot in PepT1-expressing virus fraction. The apparent Michaelis constant for [14C]glycylsarcosine was 0.55 +/- 0.06 mM. [14C]Glycylsarcosine uptake was inhibited by di- and tripeptides and orally active beta-lactam antibiotics. These results suggest that functional PepT1 recovers efficiently in a budded virus fraction, and, thus, this expression system will be a useful tool for characterization and screening of peptide-mimetic drugs in drug discovery.

Overexpression of MUC13 is associated with intestinal-type gastric cancer.

Mucins are secreted or transmembrane glycoproteins that are expressed mainly in the digestive tract. This family of proteins has been the focus of much gastric cancer research as some transmembrane mucins are implicated in tumorigenesis and make attractive targets for cancer diagnosis and therapeutics. Mucins have also been utilized to classify gastric cancer by differentiating between gastric and intestinal phenotypes. Here we show that transmembrane mucin MUC13 is upregulated in gastric cancer. By quantitative real-time reverse transcription-polymerase chain reaction and immunoblot analysis, overexpression of MUC13 was verified in more than half of the samples examined. In immunohistochemical analysis, MUC13 staining was observed in 74 of 114 cases of gastric cancer (64.9%), predominantly in intestinal type (P < 0.001), and in 9 of 10 cases of intestinal metaplasia, precancerous lesions of intestinal-type gastric cancer, but not observed in normal gastric mucosa. Moreover, MUC13 staining patterns characteristic of histological type were identified: staining was on the apical side of tubular glands in intestinal type and on the cytoplasm in diffuse type. These results suggest that MUC13 is a good differentiation marker for gastrointestinal mucosa and that it may have a causal role that correlates with two distinct gastric tumorigenesis pathways.

A novel therapeutic approach for thrombocytopenia by minibody agonist of the thrombopoietin receptor.

Antibodies have brought valuable therapeutics in the clinical treatment of various diseases without serious adverse effects through their intrinsic features such as specific binding to the target antigen with high affinity, clinical safety as serum proteins, and long half-life. Agonist antibodies, furthermore, could be expected to maximize the value of therapeutic antibodies. Indeed, several IgG/IgM antibodies have been reported to induce cellular growth/differentiation and apoptosis. These agonist antibodies, however, should be further improved to exert more potent biologic activities and appropriate serum half-life depending upon the disease indications. Here, we report that IgG antibodies against the thrombopoietin receptor (Mpl), which have an absence or very weak agonist activity, can be engineered to be agonist minibodies, which include diabody or sc(Fv)2 as potent as natural ligand. Through this technological development, minibodies have been successfully constructed to bind and activate 2 types of dysfunctional mutant Mpls that cause congenital amegakaryocytic thrombocytopenia (CAMT). This drastic conversion of biologic activities by designing minibodies can be widely applicable to generate agonist minibodies for clinical application, which will constitute a new paradigm in antibody-based therapeutics.

A dominant negative TAK1 inhibits cellular fibrotic responses induced by TGF-beta.

Transforming growth factor-beta (TGF-beta) is crucially virulent in the progression of fibrotic disorders. TAK1 (TGF-beta activated kinase 1) is one of the mitogen-activated kinase kinase kinase (MAPKKK) that is involved in TGF-beta signal transduction. To elucidate the importance of TAK1 in TGF-beta-induced fibrotic marker expression, we investigated whether dominant negative TAK1 could suppress TGF-beta signaling. Based on the finding that TAB1 (TAK1 binding protein 1) binding to TAK1 is required for TAK1 activation, a minimal portion of TAK1 lacking kinase activity that binds to TAB1 was designed as a TAK1 dominant negative inhibitor (TAK1-DN). The effect of TAK1-DN was assessed in the cells that respond to TGF-beta stimulation and that lead to the increase in production of extracellular matrix (ECM) proteins. TAK1-DN, indeed, decreased the ECM protein production, indicating that TAK1-DN retains the ability to intercept the TGF-beta signaling effectively.

A resorcylic acid lactone, 5Z-7-oxozeaenol, prevents inflammation by inhibiting the catalytic activity of TAK1 MAPK kinase kinase.

TAK1, a member of the mitogen-activated kinase kinase kinase (MAPKKK) family, participates in proinflammatory cellular signaling pathways by activating JNK/p38 MAPKs and NF-kappaB. To identify drugs that prevent inflammation, we screened inhibitors of TAK1 catalytic activity. We identified a natural resorcylic lactone of fungal origin, 5Z-7-oxozeaenol, as a highly potent inhibitor of TAK1. This compound did not effectively inhibit the catalytic activities of the MEKK1 or ASK1 MAPKKKs, suggesting that 5Z-7-oxozeaenol is a selective inhibitor of TAK1. In cell culture, 5Z-7-oxozeaenol blocked interleukin-1-induced activation of TAK1, JNK/p38 MAPK, IkappaB kinases, and NF-kappaB, resulting in inhibition of cyclooxgenase-2 production. Furthermore, in vivo 5Z-7-oxozeaenol was able to inhibit picryl chloride-induced ear swelling. Thus, 5Z-7-oxozeaenol blocks proinflammatory signaling by selectively inhibiting TAK1 MAPKKK.