Conventional or Drug-Eluting Beads? Randomized Controlled Study of Chemoembolization for Hepatocellular Carcinoma: JIVROSG-1302.

Introduction: With the advent of effective systemic therapy, transarterial chemoembolization (TACE) is established as a highly effective locoregional treatment modality for carefully selected patients with hepatocellular carcinoma (HCC). This randomized controlled trial was conducted to clarify whether selective TACE with drug-eluting beads (DEB-TACE) loaded with epirubicin or selective conventional TACE (cTACE) with epirubicin-ethiodized oil might be more effective for obtaining complete response(CR) in patients with HCC. Methods: Between March 2016 and May 2019, Child-Pugh class A or B patients with unresectable HCC who were scheduled to receive selective TACE were randomly assigned at a 1:1 ratio to the DEB-TACE arm or the cTACE arm. The primary endpoint was the CR rate at 3 months, as evaluated according to the modified Response Evaluation Criteria in Solid Tumors by an independent review committee, and the secondary endpoints were the CR rate at 1 month and incidences of adverse events. Results: A total of 200 patients (DEB-TACE, 99 patients; cTACE, 101 patients) were enrolled in the study. The CR rates at 3 months and 1 month were significantly higher in the cTACE arm (75.2%, 84.2%) as compared with the DEB-TACE arm (27.6%, 35.7%). However, the frequencies of adverse events of any grade, including pyrexia (DEB-TACE vs. cTACE, 19.4% vs. 45.5%, p = 0.0001), fatigue (5.1% vs. 15.8%, p = 0.0194), malaise (11.1% vs. 25.7%, p = 0.0103), appetite loss (12.1% vs. 28.7%, p = 0.0048), abdominal pain (12.1% vs. 23.8%, p = 0.0423), increased serum bilirubin (22.2% vs. 48.5%, p = 0.0002), hypoalbuminemia (43.4% vs. 60.3%, p = 0.0154), increased serum aspartate aminotransferase (35.7% vs. 81.2%, p < 0.0001), and increased serum alanine aminotransferase (35.7% vs. 77.2%, p < 0.0001), were also significantly higher in the cTACE arm than in the DEB-TACE arm. Conclusions: Selective cTACE appeared to have higher CR rates for local tumor control as compared to selective DEB-TACE for HCC. However, the frequency of postembolization syndrome was also significantly higher in the cTACE group than in the DEB-TACE group. Thus, to achieve CR, cTACE may be selected over DEB-TACE in patients who can be expected to tolerate postembolization syndrome.

Impact of chronological age on efficacy and safety of fluoropyrimidine plus bevacizumab in older non-frail patients with metastatic colorectal cancer: a combined analysis of individual data from two phase II studies of patients aged >75 years.

OBJECTIVE: Many clinical trials for older patients with metastatic colorectal cancer have been conducted, and fluoropyrimidine and bevacizumab are standard treatments. However, the relationship between age and the efficacy and safety of this treatment is unclear in older metastatic colorectal cancer patients. METHODS: Individual data from two phase II studies on older (≥75 years), non-frail patients with metastatic colorectal cancer treated with uracil-tegafur/leucovorin or S-1 combined with bevacizumab were collected. Patient characteristics were evaluated with multiple regression analyses for survival outcomes, using the Cox proportional hazard model and linear regression analyses for the worst grade of adverse events. RESULTS: We enrolled 102 patients with a median age of 80 years (range, 75-88 years). Of the 70 patients who died, seven (10%) died of causes unrelated to disease or treatment. The study treatment was discontinued due to adverse events in 19 patients (18.6%), with 63% aged ≥85 years. The adverse event that most commonly resulted in treatment discontinuation was grade 2 fatigue (21%). Chronological age was not associated with progression-free survival (Hazard ratio, 1.03; P = 0.40) or overall survival (Hazard ratio, 1.02; P = 0.65). Age was weakly associated with non-hematologic adverse events (regression coefficient [R], 0.27; P = 0.007), especially fatigue (R, 0.23; P = 0.02) and nausea (R, 0.19; P = 0.06), but not with hematologic (R, 0.05; P = 0.43) or bevacizumab-related (R, -0.06; P = 0.56) adverse events. CONCLUSIONS: The efficacy of fluoropyrimidine plus bevacizumab was age-independent in patients with metastatic colorectal cancer aged ≥75 years, and attention should be paid to non-hematologic adverse events as age increases.

Cancer-related FGFR2 overexpression and gene amplification in Japanese patients with gastric cancer.

OBJECTIVE: Fibroblast growth factor receptor 2 (FGFR2) has been proposed as a novel druggable target in unresectable gastric cancer. FGFR2 alteration has been reported as associated with poor prognosis even in patients with gastric cancer who received systemic chemotherapy. This study aimed to evaluate the frequency of FGFR2 overexpression and gene amplification in clinical specimens from Japanese patients with recurrent or unresectable gastric cancer. METHODS: This observational study enrolled patients who were histologically or cytologically confirmed with unresectable HER2-negative or unknown gastric or gastroesophageal junctional adenocarcinoma treated with at least one previous chemotherapy. FGFR2 overexpression and gene amplification in the specimens were evaluated by immunohistochemical staining and fluorescence in situ hybridization methods, respectively. RESULTS: In a total of 173 eligible cases, FGFR2 immunohistochemistry score was evaluated as 0, 1, 2, 3 and 4 for 20, 80, 35, 28 and 10 cases, respectively. In 151 evaluable cases with FGFR2 immunohistochemistry scores of 1-4, FGFR2 copy number expressed as fluorescence in situ hybridization signals were detected as <4, ≥4 < 10 and ≥10 copies for 123, 16 and 12 cases, respectively. FGFR2 copy number showed an increasing tendency along with higher FGFR2 immunohistochemistry scores in the corresponding specimen. The response rate and time to treatment failure for first line chemotherapy did not have any obvious relationship to FGFR2 immunohistochemistry score and FGFR2 copy number. CONCLUSIONS: Although FGFR2 overexpression and gene amplification were shown in Japanese patients with unresectable gastric cancer, these alterations did not impact the effects of cytotoxic agents as first line chemotherapy.

Characterization of a novel moderate-substrate specificity amino acid racemase from the hyperthermophilic archaeon Thermococcus litoralis.

The amino acid sequence of the OCC_10945 gene product from the hyperthermophilic archaeon Thermococcus litoralis DSM5473, originally annotated as γ-aminobutyrate aminotransferase, is highly similar to that of the uncharacterized pyridoxal 5'-phosphate (PLP)-dependent amino acid racemase from Pyrococcus horikoshii. The OCC_10945 enzyme was successfully overexpressed in Escherichia coli by coexpression with a chaperone protein. The purified enzyme demonstrated PLP-dependent amino acid racemase activity primarily toward Met and Leu. Although PLP contributed to enzyme stability, it only loosely bound to this enzyme. Enzyme activity was strongly inhibited by several metal ions, including Co2+ and Zn2+, and nonsubstrate amino acids such as l-Arg and l-Lys. These results suggest that the underlying PLP-binding and substrate recognition mechanisms in this enzyme are significantly different from those of the other archaeal and bacterial amino acid racemases. This is the first description of a novel PLP-dependent amino acid racemase with moderate substrate specificity in hyperthermophilic archaea.

Randomised phase II study of panitumumab plus irinotecan versus cetuximab plus irinotecan in patients with KRAS wild-type metastatic colorectal cancer refractory to fluoropyrimidine, irinotecan and oxaliplatin (WJOG 6510G).

BACKGROUND: Cetuximab has been shown to be clinically active when given in combination with irinotecan in patients with irinotecan-refractory metastatic colorectal cancer (mCRC). However, it has remained unclear whether panitumumab is effective when combined with irinotecan. We compared efficacies of both regimens in this randomised phase II study. PATIENTS AND METHODS: Patients with wild-type KRAS exon 2 mCRC previously treated with fluorouracil-, oxaliplatin- and irinotecan-based chemotherapies were randomised (1:1) to either panitumumab plus irinotecan (panitumumab arm) or cetuximab plus irinotecan (cetuximab arm). The primary end-point was progression-free survival (PFS). The planned sample size was 120, expecting a hazard ratio (HR) of 1.0 with non-inferiority margin of 1.3 (one-sided alpha error 0.2 and power 0.7). Major secondary end-points were overall survival (OS), response rate and safety. RESULTS: From December 2011 to September 2014, 121 patients were enrolled, and 61 and 59 patients were randomised to the panitumumab and cetuximab arms, respectively (1 patient excluded). Most patients (97%) had received prior chemotherapies containing bevacizumab. The median PFS was 5.42 months in the panitumumab arm and 4.27 months in the cetuximab arm (HR = 0.64, 95% confidence interval [CI] = 0.44-0.94, P < 0.001 for non-inferiority, P = 0.058 for superiority), and median OS was 14.85 and 11.53 months (HR = 0.66, 95% CI = 0.44-1.00, P = 0.050 for superiority), respectively. The incidence of grade 3 or 4 hypomagnesaemia was higher in the panitumumab arm than that in the cetuximab arm (17% vs. 7%). CONCLUSION: Panitumumab may be non-inferior to cetuximab in combination with irinotecan in survival of patients with irinotecan-refractory mCRC.

Phase II study of S-1 on alternate days plus bevacizumab in patients aged ≥ 75 years with metastatic colorectal cancer (J-SAVER).

BACKGROUND: Alternate-day administration of S-1 is thought to reduce toxicities. This phase II study evaluated S-1 on alternate days combined with bevacizumab as first-line treatment for elderly patients with metastatic colorectal cancer. PATIENTS AND METHODS: Eligible patients had histologically proven colorectal adenocarcinoma, measurable metastatic lesions, age ≥ 75 years, Eastern Cooperative Oncology Group performance status ≤ 1, no previous chemotherapy, and refused oxaliplatin- or irinotecan-containing regimens. Patients received 40 mg, 50 mg, or 60 mg (body surface area ≤ 1.25 m2, > 1.25 to ≤ 1.50 m2, or > 1.50 m2, respectively) of S-1 twice orally on Sunday, Monday, Wednesday, and Friday every week. Bevacizumab (7.5 mg/kg) was administered every 3 weeks. The primary endpoint was progression-free survival. RESULTS: Of 54 enrolled patients, 50 patients were evaluated for efficacy and 53 for safety. The median age was 79 years (range 75-88 years). The median progression-free survival was 8.1 months (95% confidence interval (CI) 6.7-9.5 months). The median overall survival was 23.1 months (95% CI 17.4-28.8 months). The response rate was 44% (95% CI 30.2-57.8%), and the disease control rate was 88% (95% CI 79.0-97.0%). Grade 3 or higher hematologic, non-hematologic, and bevacizumab-related adverse events occurred in 9%, 11%, and 25% of patients, respectively. The most common grade 3 and 4 treatment-related adverse events were hypertension (11%), nausea (6%), fatigue (6%), anemia (6%), and proteinuria (6%). Only 6 patients discontinued treatment due to adverse events. CONCLUSION: S-1 on alternate days combined with bevacizumab showed better tolerability and comparable survival compared with the results of similar studies.

aCGH Analysis of Predictive Biomarkers for Response to Bevacizumab plus Oxaliplatin- or Irinotecan-Based Chemotherapy in Patients with Metastatic Colorectal Cancer.

BACKGROUND: The randomized phase III study (WJOG4407G) showed equivalent efficacy between FOLFOX and FOLFIRI in combination with bevacizumab as the first-line treatment for metastatic colorectal cancer (mCRC). We studied whole genome copy number profiles using array-based comparative genomic hybridization (aCGH) analysis of tumor tissue samples obtained in this study. The aim of this study was to identify gene copy number alterations that could aid in selecting either FOLFOX or FOLFIRI in combination with bevacizumab for patients with mCRC. MATERIALS AND METHODS: DNA was purified from 154 pretreatment formalin-fixed paraffin-embedded tissue samples (75 from the FOLFOX arm and 79 from the FOLFIRI arm) of 395 patients enrolled in the WJOG4407G trial and analyzed by aCGH. Genomic regions greater than 1.2-fold were regarded as copy number gain (CNG). RESULTS: Patient characteristics between the treatment arms were well balanced except for tumor laterality (left side; 64% in FOLFOX arm and 80% in FOLFIRI arm, p = .07). FOLFIRI showed a trend toward better response rate (RR), progression-free survival (PFS) and overall survival (OS) than FOLFOX in the patients with CNG of chromosome 8q24.1 (Fisher's exact test, p = .134 for RR; interaction test, p = .102 for PFS and p = .003 for OS) and 8q24.2 (Fisher's exact test, p = .179 for RR; interaction test, p = .144 for PFS and p = .002 for OS). CONCLUSION: Chromosome 8q24.1-q24.2 may contain genes that could potentially serve as predictive markers for selecting either FOLFOX or FOLFIRI in combination with bevacizumab for treatment of patients with mCRC. IMPLICATIONS FOR PRACTICE: Bevacizumab has been used as a standard first-line treatment for patients with metastatic colorectal cancer (mCRC) in combination with either oxaliplatin-based or irinotecan-based chemotherapy. Until now, there has been no predictive marker to choose between the two combination chemotherapies. This array-based comparative genomic hybridization analysis revealed that the difference in therapeutic effect between the two combination chemotherapies is prominent in patients with mCRC with gene copy number gain in chromosome 8p24.1-p24.2. Such patients showed more favorable response and survival when treated with irinotecan-based combination chemotherapy. Overlapping genes commonly found in this region may be predictive biomarkers of the efficacy of the combination chemotherapy with bevacizumab.

Halide-Substituted Electronic Properties of Organometal Halide Perovskite Films: Direct and Inverse Photoemission Studies.

Solution-processed perovskite solar cells are attracting increasing interest due to their potential in next-generation hybrid photovoltaic devices. Despite the morphological control over the perovskite films, quantitative information on electronic structures and interface energetics is of paramount importance to the optimal photovoltaic performance. Here, direct and inverse photoemission spectroscopies are used to determine the electronic structures and chemical compositions of various methylammonium lead halide perovskite films (MAPbX3, X = Cl, Br, and I), revealing the strong influence of halide substitution on the electronic properties of perovskite films. Precise control over halide compositions in MAPbX3 films causes the manipulation of the electronic properties, with a qualitatively blue shift along the I → Br → Cl series and showing the increase in ionization potentials from 5.96 to 7.04 eV and the change of transport band gaps in the range from 1.70 to 3.09 eV. The resulting light absorption of MAPbX3 films can cover the entire visible region from 420 to 800 nm. The results presented here provide a quantitative guide for the analysis of perovskite-based solar cell performance and the selection of optimal carrier-extraction materials for photogenerated electrons and holes.

Uracil-Tegafur and Oral Leucovorin Combined With Bevacizumab in Elderly Patients (Aged ≥ 75 Years) With Metastatic Colorectal Cancer: A Multicenter, Phase II Trial (Joint Study of Bevacizumab, Oral Leucovorin, and Uracil-Tegafur in Elderly Patients [J-BLUE] Study).

BACKGROUND: We previously reported that uracil-tegafur with oral leucovorin (UFT/LV) treatment for elderly patients (aged ≥ 75 years) was well-tolerated in a phase II study. In the present study, the efficacy and safety of a modified (1-week shorter administration period) UFT/LV schedule combined with bevacizumab for a similar population are reported. PATIENTS AND METHODS: The present study was a single-arm, open-label, multicenter, cooperative group clinical trial. The key eligibility criteria included age ≥ 75 years, Eastern Cooperative Oncology Group (ECOG) performance status 0 or 1, first-line chemotherapy, measurable lesions, and preserved organ function. Patients received UFT 300 mg/m(2)/d and LV 75 mg/d on days 1 to 21 and intravenous bevacizumab 5 mg/kg on days 1 and 15. Treatment was repeated every 28 days. The primary endpoint was progression-free survival (PFS), and the secondary endpoints were the objective response rate (ORR), overall survival (OS), and safety. RESULTS: Of the 55 patients enrolled from 15 Japanese institutions, 52 eligible patients were evaluated. Their median age was 80 years (range, 75-87 years), and 73% had an ECOG performance status of 0. The median PFS was 8.2 months (95% confidence interval [CI], 6.2-10 months). The ORR was 40% (95% CI, 27%-55%). The median OS was 23 months (95% CI, 12-33 months). The most common grade 3 and 4 treatment-related adverse events were hypertension (12%), fatigue (8%), anemia (8%), nausea (6%), and diarrhea (6%). Treatment-related death occurred in 2 patients. CONCLUSION: UFT/LV (3 weeks of therapy and 1 week without) combined with biweekly bevacizumab is a tolerable and effective treatment option for elderly patients (aged ≥ 75 years) with metastatic colorectal cancer.

Glasgow Prognostic Score predicts poor prognosis among advanced biliary tract cancer patients with good performance status.

Advanced cancer patients with good performance status (PS) sometimes show poor prognosis despite receiving some chemotherapies. We evaluated prognosis of chemo-naïve advanced biliary tract cancer (ABTC) patients with good PS by Glasgow Prognostic Score (GPS). Sixty-two patients with Eastern Cooperative Oncology Group PS 0 or 1 were retrospectively analyzed, using multivariate Cox regression. GPS was defined with serum levels of two parameters, albumin >3.5 g/dl and C-reactive protein <1.0 mg/dl (both as 0, either as 1, and neither as 2). PS 0 (n = 32) and 1 (n = 30) patients had similar survival (P = 0.98). The median overall survival (OS) was 17.0 months for GPS 0 (n = 19), 14.2 months for GPS 1 (n = 17), and 6.4 months for GPS 2 (n = 26). GPS 2 had significantly shorter OS than GPS 0 (P = 0.002) or 1 (P = 0.033). Multivariate analysis identified two independent prognostic factors: GPS (hazard ratio 0.60, 95 % confidence interval 0.40-0.90, P = 0.012) and liver metastasis (hazard ratio 0.43, 95 % CI 0.20-0.90, P = 0.026). GPS was useful for chemo-naïve ABTC patients with good PS.

A randomized phase II study comparing S-1 plus weekly split-dose cisplatin with S-1 plus standard-dose cisplatin as first-line chemotherapy for advanced gastric cancer.

BACKGROUND: S-1 plus weekly split-dose cisplatin demonstrated promising results in previous phase I and II studies for advanced gastric cancer (AGC) patients. METHODS: In this randomized phase II study, the efficacy and safety of S-1 plus weekly split-dose cisplatin (SWP, S-1 daily oral dose of 80-120 mg according to body surface area on days 1-14, and cisplatin 20 mg/m(2) i.v. on days 1 and 8 every 3 weeks) were compared with those of S-1 plus standard-dose cisplatin (SP) as first-line chemotherapy for AGC patients. The primary endpoint was 1-year survival rate. RESULTS: Patients were randomized into two groups: 18 in the SWP arm and 19 in the SP arm. This trial was terminated early because of low patient enrollment. The 1-year survival rate was 61 % [95 % confidence interval (CI), 36-86 %] and 53 % (95 % CI, 30-75 %) in the SWP and SP arms, respectively. However, the median survival time was 12.3 months (9.9-14.6 months) and 15.7 months (4.0-27.4 months), respectively (P = 0.064). Progression-free survival was significantly shorter in the SWP arm than in the SP arm (P = 0.047). Toxicity tended to be milder in the SWP arm than in the SP arm. For approximately 40 % of patients in the SWP arm, cisplatin was omitted on day 8 and treatment delayed because of prolonged myelosuppression. CONCLUSIONS: No clear benefits of adding cisplatin to S-1 in the SWP arm were demonstrated in this study. At this point, split-dose cisplatin combined with S-1 cannot be recommended for use in clinical practice.

Phase I/II multicenter study of transarterial chemoembolization with a cisplatin fine powder and porous gelatin particles for unresectable hepatocellular carcinoma: Japan Interventional Radiology in Oncology Study Group Study 0401.

PURPOSE: A multicenter phase I/II study of transarterial chemoembolization with a fine cisplatin powder and gelatin particles (GPs) for multifocal hepatocellular carcinoma (HCC) was conducted. Primary endpoints were dose-limiting toxicity (DLT) and recommended dose (RD). Secondary endpoints were the incidence and severity of adverse events and tumor response. MATERIALS AND METHODS: Nonselective transarterial chemoembolization was performed until all tumor enhancement disappeared. Lipiodol was not used. In the phase I study, the cisplatin dose was escalated from 35 mg/m(2) to 65 mg/m(2) in 15-mg/m(2) increments to determine DLT and RD. In the phase II study, 40 patients were treated with the RD. Toxicity was assessed by Common Toxicity Criteria for Adverse Effects (version 3.0), and tumor response was evaluated by Response Evaluation Criteria in Solid Tumors (RECIST; version 1.0) and European Association for the Study of the Liver (EASL) criteria. RESULTS: A total of 46 patients were enrolled. As no DLT occurred at any dose level in the phase I study, RD was determined as 65 mg/m(2). In the phase II study, the treatment was discontinued in one patient as a result of vasovagal response. Toxicities of grade 3 or higher included nausea (2.2%), pancreatitis (2.2%), cholecystitis (2.2%), thrombocytopenia (8.7%), hyperbilirubinemia (2.2%), and increased aspartate aminotransferase (28.3%) and alanine aminotransferase (21.7%) levels. Tumor response rates under RD were 25.6% and 64.1% by RECIST and EASL criteria, respectively. CONCLUSIONS: Nonselective transarterial chemoembolization with fine cisplatin powder and GPs was well tolerated and effective in patients with multifocal HCC at the RD of 65 mg/m(2).

Phase II clinical study on stent therapy for unresectable malignant colorectal obstruction (JIVROSG-0206).

PURPOSE: A phase II study of stent therapy for unresectable malignant colorectal obstruction was conducted to ascertain the clinical efficacy, safety, and procedural feasibility. METHODS: Inclusion criteria comprised unresectable obstruction of the rectum or sigmoid colon; no other apparent stenosis; performance status by Eastern Cooperative Oncology Group ≤3; and maintained major organ function. The treatment protocol was to place an uncovered metal stent through the anus in an obstructive portion under x-ray fluoroscopic guidance. The patients were followed for 4 weeks after therapy, and the degree of improvement in subjective symptoms lasting ≥2 weeks was assessed as effective when the patient was decompressed with stent, or ineffective when not decompressed. Rate of clinical efficacy was defined as the proportion of effective cases. RESULTS: The participants of the study comprised 33 patients (13 men and 20 women; mean age, 60 y). Rate of procedure completion was 97.0% (32/33). Treatment was effective in 27 patients, ineffective in 4, and unassessable in 1, yielding a clinical efficacy rate of 81.8% (27/33). Death owing to underlying disease (n=3), stent removal owing to anal pain (n=1), and occlusion at another location (n=1) were noted. No recurrences were seen among clinically effective cases. Adverse reactions included grades 2 to 3 diarrhea (n=12), pain (n=5), bleeding (n=1), and dysuria (n=1), but no grade 4 adverse reactions or treatment-related deaths were identified. CONCLUSIONS: Stent therapy for unresectable malignant colorectal obstruction is effective, safe, and feasible.

Detection of experimental autoimmune myocarditis in rats by 111In monoclonal antibody specific for tenascin-C.

BACKGROUND: Although the identification of inflammatory infiltrates in endomyocardial biopsy specimens is necessary for the definite diagnosis of myocarditis, the biopsy test is invasive and is not sensitive. Therefore, a new diagnostic technique for the early and noninvasive evaluation of myocarditis has been awaited. Expression of tenascin-C (TNC), one of the oligometric extracellular glycoproteins, is induced in various pathological states, including inflammation, suggesting that TNC can be a molecular marker of myocarditis. METHODS AND RESULTS: An 111In anti-TNC monoclonal antibody Fab' fragment was injected intravenously into rats with experimental autoimmune myocarditis (EAM), and the biodistribution of this radiotracer was measured. Rapid clearance of radioactivity from the blood was observed in both EAM and control rats (<1% at 6 hours after injection). Myocardial uptake of the tracer was much higher in EAM rats than in control rats (7.54-, 4.39-, and 3.51-fold at 6, 24, and 48 hours after injection, respectively). By autoradiography, high radioactivities were clearly observed in the regions indicative of inflammation in EAM rats. Single-photon emission CT imaging demonstrated the focal myocardial uptake of 111In anti-TNC Fab' in vivo. CONCLUSIONS: Radiolabeled anti-TNC Fab' may be useful for the noninvasive diagnosis of myocarditis.

Immunohistochemical localization of thyroid stimulating hormone induced by a low oral dose of 2,3,7,8-tetrachlorodibenzo-p-dioxin in female Sprague-Dawley rats.

We have investigated how a low dose of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) affects thyroid hormone regulation, especially in relation to the localization of thyroid stimulating hormone (TSH) in the pituitary and that of thyroxin (T4) of the thyroid in the rat. Female Sprague-Dawley rats were given a single oral administration of TCDD ranging from 1.0 to 4.0 microg/kg body weight (bw), and then tissue specimens were removed on day 7 post-administration. Thyroid hormone concentrations were measured in serum, and the expression of the TCDD-responsive genes, UDP-glucuronosyltransferase-1 (UGT1) and cytochrome P4501A1 (CYP1A1) were examined in the liver. TCDD administration resulted in an increase in both immunostaining intensity and the number of TSH-positive cells in the anterior pituitary. T4 was found to localize only in the follicular lumen of the thyroid in vehicle-treated control rats, while TCDD administration caused a foamy change in the colloid of some follicles, an indication of accelerating the biosynthesis of T4 in the thyroid. By morphometrical analysis, the ratio of parenchymal/lumenal area of the thyroid was found to increase in response to TCDD. TCDD treatment as low as 2.0 microg TCDD/kg bw induced a significant decrease in both serum total T4 (TT4) and free T4 (FT4) concentrations in the rats, with a significant increase in serum TSH levels in the 4.0 microg TCDD/kg bw rats. Serum total triiodothyronine (TT3) level was unchanged in all groups. The UGT1 gene was significantly induced at a TCDD dose as low as 1.0 microg/kg bw in a dose-dependent manner. TCDD concentrations in the serum, liver and adipose tissues were detected in a dose-related fashion. The present immunohistochemical results clearly support the earlier biochemical findings on the perturbation of the thyroid-pituitary axis by TCDD and suggest that UGT1 is an immediate target of a low TCDD exposure that triggers the perturbation.