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Objective This multicenter phase II Japanese Gynecologic Oncology Group study (JGOG1067) was designed to evaluate the efficacy and safety of postoperative chemotherapy in patients with node-positive cervical cancer. Methods Patients with stage IB–IIA squamous cervical cancer who underwent radical hysterectomy and were confirmed to have pelvic lymph node metastasis were eligible for this study. The patients postoperatively received irinotecan (CPT-11; 60mg/m 2 intravenously on days 1 and 8) and nedaplatin (NDP; 80mg/m 2 intravenously on day 1). Chemotherapy administration commenced within 6weeks after surgery and was repeated every 28days for up to 5cycles. The primary endpoint of this study was the 2-year recurrence-free survival (RFS) rate. The secondary endpoints were the 5-year overall survival (OS) rate, 5-year RFS rate, and adverse events such as complications of chemotherapy and lower-limb edema. Results Sixty-two patients were analyzed according to our protocol, among whom 55 (88.7%) completed 5cycles of scheduled treatment. The median follow-up period was 66.1months (range, 16.8–96.6months). The 2-year and 5-year RFS rates were 87.1% (95% confidence interval [CI]: 75.9–99.3) and 77.2% (95% CI: 64.5–85.8), respectively. Fourteen patients (22.5%) experienced recurrence during the follow-up period, 8 of whom died of the disease. The 5-year OS rate in this study was 86.5% (95% CI: 74.8–93.0). Only 9.7% of the patients experienced lymphedema in their legs. Conclusion Postoperative chemotherapy without radiotherapy was found to be very effective in high-risk patients with node-positive cervical cancer.

Monitoring the attribution of human papillomavirus (HPV) genotypes to cervical precancerous lesions is essential in assessing the efficacy of HPV vaccines. To resolve the lack of studies comparing the HPV genotyping procedures used to estimate HPV genotype attribution, we undertook a retrospective cross-sectional study to determine the appropriate genotyping procedures for evaluating the potential efficacy of HPV vaccines. Three procedures, including two different genotyping methods, Clinichip HPV test (C-Chip) and modified GP5+/6+ PCR coupled to fluorescent bead sorter detection (MGP), using exfoliated cervical cells (C-Chip and C-MGP, respectively) or formalin-fixed paraffin-embedded tissues (F-MGP), were compared. The overall agreement in detecting high-risk HPV was 88.5-92.1% among the three procedures, and genotype-specific agreement was 83.9-100% for all pairwise comparisons. In cervical intraepithelial neoplasia grade 2/3 specimens, HPV16/18 attribution estimated with the hierarchical attribution method was consistent among the procedures: 52.3% (45/86) for C-Chip, 54.7% (47/86) for C-MGP, and 52.3% (45/86) for F-MGP (P = 0.81). HPV16/18/31/33/45/52/58 hierarchical attribution was 88.4% (76/86) with C-Chip, 86.0% (74/86) with C-MGP, and 83.7% (72/86) with F-MGP (P = 0.49). In cervical intraepithelial neoplasia grade 3 specimens, the corresponding hierarchical attribution was 96.4% (53/55) with C-Chip, 89.1% (49/55) with C-MGP, and 94.5% (52/55) with F-MGP (P = 0.27). Although F-MGP is theoretically a reliable method for determining HPV genotype attribution, it is acceptable to use C-Chip or C-MGP, coupled to the hierarchical attribution formula to correct the bias of multiple infections. These approaches using exfoliated cervical cells are practical for monitoring the efficacy of HPV vaccines.

microRNAs (miRNAs) play important roles in regulation of gene expression during cervical carcinogenesis. We investigated expression profiles of miRNAs in cervical cancer and its precursor lesions by utilizing cervical mucus. Cervical mucus was collected from 230 patients with a normal cervix, cervical intraepithelial neoplasia (CIN), squamous cell carcinoma (SCC), or adenocarcinoma (AD). The levels of miRNA in the mucus were quantified by miRNA array and real-time reverse-transcriptase polymerase chain reaction (RT-PCR). The performance for detecting diseases was statistically analysed. The expression of miRNAs was further validated in the surgical tissues of enrolled patients. Four miRNAs (miR-126-3p, -20b-5p, -451a, and -144-3p) were significantly up-regulated in SCC and AD compared with normal, and their expression levels correlated with disease severity and high-risk human papillomavirus infection. Receiver operating characteristic curve analyses revealed that the area under the curve values for miR-126-3p, -20b-5p, -451a, and -144-3p were 0.89, 0.90, 0.94, and 0.93, respectively, for SCC plus AD compared with normal, showing high accuracy of cancer detection. Real-time RT-PCR analyses confirmed the expression of these four miRNAs in frozen tissues from cervical cancer. miR-126-3p, -20b-5p, -451a, and -144-3p in cervical mucus are promising biomarkers for cervical cancer and high-grade CINs.

The present study aimed to investigate the association between nedaplatin (NDP) sensitivity and the expression of biological factors in cervical cancer. A total of 45 cervical cancer specimens, including 18 pretreatment biopsies and 27 surgical specimens, were used in histoculture drug response assays to determine the chemosensitivity of cervical cancer specimens to NDP. Each specimen was assessed for immunohistochemical expression of Ki-67, p53, B-cell lymphoma-2 (Bcl-2), Bcl-2-associated X protein (Bax), cleaved caspase-3, cyclooxygenase-2 (COX-2), and excision repair cross-complementation group 1 (ERCC1). The results revealed that low or negative expression of p53, Bcl-2 and COX-2, and high or positive expression of cleaved caspase-3 were significantly correlated with high sensitivity to NDP. However, there were no significant differences in Ki-67, Bax or ERCC1 expression between the low and high sensitivity groups. These findings indicate that sensitivity to platinum may be easily predicted by immunostaining for the detection of these specific factors in pretreatment biopsies or surgical specimens. The expression profiles of these targets may therefore provide additional information for planning individualized chemotherapy in the treatment of cervical cancer.

Objective: Histopathological variation has been demonstrated in grade 3 endometrioid adenocarcinomas. We attempted to evaluate the clinicopathological features of grade 3 tumors by endometrial cytological features using a scoring system. Study Design: Twenty-one endometrial cytological samples were evaluated using 5 cytological features: rates of cluster formation in tumor cells; nuclear pleomorphism; nuclear dimension; size of nucleoli, and chromatin structure and distribution. The relationships between cytological scores and clinicopathological factors or prognosis were investigated. Results: The median cytological score was 6 (range 4-14); therefore, samples with scores of 4-5 were defined as having low scores, while those with scores of 6-14 were defined as high scores. The accuracy of the cytological diagnosis for grade 3 tumors in the high score group (8/10 patients, 80.0%) was significantly higher than that of the low score group (2/11 patients, 18.2%; p = 0.009). Significant relationships between cytological scores and lymph node metastases or positive peritoneal cytology were observed (p = 0.03 and 0.035, respectively). The overall survival rate was significantly worse in the high score group (30.0%) than the low score group (88.9%; p = 0.02). Conclusions: Grade 3 endometrioid adenocarcinomas varied in cytological features; according to the scoring system used, high scores were associated with worse clinicopathological factors and poorer prognosis than low scores.

This study was conducted to retrospectively compare the efficacy and safety of irinotecan (CPT-11) and pegylated liposomal doxorubicin (PLD) in patients with platinum-resistant or -refractory recurrent epithelial ovarian and primary peritoneal carcinoma.Nineteen patients who received CPT-11 and eleven patients who received PLD were enrolled. CPT-11 was intravenously administered at a starting dose of 60-100 mg/m(2) on day 1, 8, and 15 every 28 days, and PLD was administered at a starting dose of 40-50 mg/m(2) on day 1 every 28 days. Primary outcomes were overall response rate (complete response [CR] + partial response [PR]), disease control rate (CR + PR + stable disease), and progression-free survival (PFS) in each group. Clinical response was evaluated every two or three cycles using the Response Evaluation Criteria in Solid Tumors criteria; CA125 analysis was not performed.The overall response rate was 21.1 % (PR, four cases) and 0 % (p = 0.10) in the CPT-11 and PLD groups, respectively, and the disease control rate was 73.7 and 45.5 % (p = 0.12), respectively. Median PFS was 25.3 (range 5.4-69.9) weeks and 12.7 (range 4.0-43.1) weeks in the CPT-11 and PLD groups, respectively; however, this difference was not statistically significant (p = 0.064). Major adverse events in the CPT-11 group were neutropenia, nausea, and diarrhea, whereas those in the PLD group included thrombocytopenia, anemia, stomatitis, and hand-foot syndrome.This retrospective study demonstrated comparable efficacy outcomes for CPT-11 and PLD. The overall response rate, disease control rate, and median PFS were more favorable in the CPT-11 group compared to the PLD group, although the difference was not significant. The adverse event profiles were different between groups. These results suggest that CPT-11 might be a feasible choice as single-agent salvage chemotherapy for platinum-resistant or -refractory recurrent epithelial ovarian and primary peritoneal carcinoma beside established regimen like PLD.

Rina Kato,1 Kiyoshi Hasegawa,1 Risa Ishii,1 Akiko Owaki,1 Yutaka Torii,1 Shuko Oe,1 Hiroshi Hirasawa,2 Yoichi Kobayashi,3 Yasuhiro Udagawa1 1Department of Obstetrics and Gynecology, Fujita Health University School of Medicine, Toyoake, Japan; 2Department of Pathology, Fujita Health University School of Medicine, Toyoake, Japan; 3Department of Obstetrics and Gynecology, Kyorin University School of Medicine, Mitaka, Japan Introduction: Human epidermal growth factor receptor (HER)-2 overexpression or gene amplification is more common in high-grade or type 2 endometrial carcinomas. We assessed the discordance of HER-2 expression between primary and metastatic or recurrent endometrial carcinomas. Materials and methods: Thirty-six primary, along with 14 metastatic and five recurrent tumors (matched to primaries), pathologically confirmed as high-grade or type 2 endometrial carcinomas, were submitted for immunohistochemistry (IHC) for HER-2. Fluorescence in situ hybridization was performed when the tumors showed HER-2 overexpression (≥2+ IHC score). The results of the IHC and fluorescence in situ hybridization assays were compared between the primary and metastatic or recurrent tumors. The relationships between HER-2 expression and clinicopathological factors or prognosis were investigated. Results: HER-2 overexpression and HER-2 amplification (a ratio of HER-2 copies to chromosome 17 [CEP17] copies ≥2.2) were detected in 33.3% (twelve of 36 patients) and 5.6% (two of 36 patients) of primary tumors, respectively. HER-2 overexpression was not associated with clinicopathological factors or prognosis. In 19 tumor specimens obtained from metastatic or recurrent tumors, HER-2 overexpression and HER-2 amplification were detected in 57.9% (eleven patients) and 15.8% (three patients), respectively. HER-2 overexpression tended to predict a worse prognosis. Conclusion: HER-2 expression in metastatic or recurrent tumors was more frequent than in matched primary high-grade or type 2 endometrial carcinomas. Trastuzumab in combination with cytotoxic chemotherapy may represent an alternative therapeutic option for these tumors. Keywords: endometrial carcinoma, high grade, type 2, HER-2, metastatic or recurrent tumors

Objective: Several studies have suggested that excision repair cross-complementation group 1 (ERCC1), a protein involved in nucleotide excision repair, is associated with resistance to platinum agent-based chemotherapy or chemoradiotherapy with platinum agents in various types of cancer. Herein we evaluated ERCC1 protein expression in uterine cervical adenocarcinoma and the relationship between this expression, clinicopathological factors, and clinical outcome, particularly in patients receiving adjuvant cisplatin-based chemotherapy or chemoradiotherapy with cisplatin. Methods: Thirty-six patients with International Federation of Gynecology and Obstetrics (FIGO) stage IB to stage IIB cervical adenocarcinoma who underwent radical hysterectomy were evaluated. Excision repair cross-complementation group 1 protein expression was examined by immunohistochemistry in tumor tissues. The relationship between ERCC1 expression levels and clinicopathological factors (age, FIGO stage, histological grade, tumor size, vascular invasion, cervical stromal invasion, and lymph node metastases) and prognosis was evaluated. Results: No significant differences between ERCC1 expression levels and clinicopathological factors were observed. The patients in the ERCC1 high-expression group (n = 7) experienced significantly worse disease-free survival than the patients in the ERCC1 low-expression group (n = 29; P = 0.005). Among the 25 patients who received cisplatin-based chemotherapy or chemoradiotherapy with cisplatin, those with high ERCC1 expression (n = 5) also experienced significantly worse disease-free survival than those with low ERCC1 expression (n = 20; P = 0.002). Moreover, univariate and multivariate analyses revealed that high ERCC1 expression was an independent prognostic factor in patients receiving cisplatin-based chemotherapy or chemoradiotherapy with cisplatin. Conclusions: This is the first analysis of the association between ERCC1 expression and clinical outcomes in patients with uterine cervical adenocarcinoma. High ERCC1 protein expression was revealed to be associated with worse disease-free survival in the patients who received adjuvant cisplatin-based chemotherapy or chemoradiotherapy with cisplatin and was shown to be an independent prognostic factor. Further evaluation with a larger number of patients is required to confirm these preliminary observations.

Recently, as laparoscopic myomectomy (LM) has become increasingly common, reports of intraoperative or postoperative complications have arisen. We experienced a case of massive hemorrhage resulting from a ruptured uterine arteriovenous fistula after LM. A 24-year-old woman, nulligravid, presented with hypermenorrhea. She was diagnosed with an 8-cm intramyometrial leiomyoma of the posterior uterus with endometrial deformation. LM was performed. The myoma was soft, its boundaries were not clear, and there was extensive contact with endometrium. Operative time, blood loss, and enucleate weight were 181 minutes, 1,000 ml, and 298g. On a transvaginal ultrasound 25 days after the operation, a cystic lesion was noted in the area of the myomectomy. Color Doppler ultrasonography showed a fountain of blood streaming from a single artery into the cyst, while the size of the cyst was not changed. However, a massive hemorrhage erupted even as we were conferring with the patient in the medical examination room. She underwent emergency laparotomy on the same day. Pulsatile bleeding from a 1mm diameter artery in the wound of the myomectomy was observed. We examined the cyst in detail after ligating the artery. The wall of cyst was a structured fibrous myomatous capsule of a white color with a perforation of the intrauterine part. Blood infiltration and hematoma were not seen at all in the myometrium of the cyst. We have performed LM on 406 patients in our hospital. This case was the first of its kind, so we are reporting it as a warning for consideration in the LM of the future.

Primary uterine cervical neuroendocrine tumors are rare, but affect relatively young women and the prognosis is poor despite multidisciplinary treatment. The incidence of meningeal carcinomatosis arising from malignant tumors of the uterine cervix is extremely low, only two patients with meningeal carcinomatosis arising from a uterine cervical neuroendocrine tumor have been reported in the English literature. Moreover, there have been no reports in which this was confirmed at autopsy. We encountered a pregnant woman aged 33 years who was diagnosed as having atypical carcinoid of the uterine cervix after radical surgery. Despite multidrug chemotherapy (paclitaxel + etoposide + cisplatin and irinotecan + carboplatin), the patient developed multiple organ metastases. Although there was no metastasis to the brain parenchyma or the spinal cord parenchyma, the patient also developed meningeal carcinomatosis. Whole-brain radiation therapy was performed, but was ineffective. The patient died at 19 months after her initial operation and 10 days after diagnosis of meningeal carcinomatosis. The presence of meningeal carcinomatosis was confirmed at autopsy.

Podoplanin is a 43-kd mucin-type transmembrane glycoprotein that is a candidate marker for the pathologic diagnosis of mesothelioma and lymphatic endothelial cells and lymphangiogenesis. The aim of this study was to investigate podoplanin expression in epithelial ovarian carcinomas. Immunohistochemistry was performed on the paraffin-embedded tissues from 78 patients with epithelial ovarian carcinomas consisting of serous adenocarcinoma (SA), endometrioid adenocarcinoma (EM), mucinous adenocarcinoma (MA), and clear cell adenocarcinoma (CCC) cases. Only 36.8% (7/19) of SA, 33.3% (6/18) of EM, and 15.8% (3/19) of MA cases were positive for podoplanin expression, whereas 54.5% (12/22) of CCC samples were positive. Immunohistochemical scores (mean+/-SD) were 1.2+/-1.5, 1.9+/-2.6, 0.8+/-1.6 and, 3.6+/-4.0 in SA, EM, MA, and CCC, respectively. Podoplanin expression was significantly stronger in CCC than in other histologic types. However, no significant correlation was observed between its expression and FIGO stage, the presence of endometriosis, lymph node metastasis, or recurrence. There was also no correlation between podoplanin expression and overall survival. We confirmed the expression of podoplanin in epithelial ovarian carcinomas, particularly in CCC. Podoplanin might have utility as a marker for CCC in pathologic diagnosis. Further investigation is needed to clarify the relationship between podoplanin expression and the biologic characteristics of CCC.

BACKGROUD/AIM: We previously demonstrated that high protein expression of excision repair cross-complementation group-1 (ERCC1) was associated with poor disease-free survival in patients who received adjuvant cisplatin-based chemotherapy or chemoradiotherapy with cisplatin, and was shown to be an independent prognostic factor. In the present study, we evaluated ERCC1 expression levels in uterine cervical adenocarcinoma cell lines to assess whether they are affected by treatment with cisplatin with and without 5-fluorouracil (5-FU).Firstly, half-maximal (50%) inhibitory concentration (IC50) values for cisplatin or 5-FU were calculated in cervical adenocarcinoma, HCA-1, and TCO-2 cell lines by 3-(4,5-di-methylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, yellow tetrazole (MTT) assay. ERCC1 mRNA and protein levels were investigated by reverse transcription-polymerase chain reaction (RT-PCR) and western blotting. Secondly, cisplatin-resistant HCA-1 cells, designated HCA-1R cells were established, and IC50 values for cisplatin and 5-FU were calculated by the MTT assay. ERCC1 mRNA expression levels were investigated using quantitative RT-PCR following treatment with cisplatin with and without 5-FU.HCA-1 and TCO-2 cells exhibited similar sensitivity to cisplatin, and 5-FU, and comparable expression of ERCC1 mRNA and protein levels. HCA-1R cells exhibited two-fold higher resistance to cisplatin and a significantly higher level of ERCC1 mRNA expression compared to native HCA-1 cells. ERCC1 expression was significantly elevated by cisplatin treatment, which was reduced by co-administration of 5-FU in HCA-1, TCO-2 and HCA-1R cells.The current study demonstrated an association between ERCC1 expression and sensitivity to cisplatin in cervical adenocarcinoma cells. Co-administration of cisplatin and 5-FU revealed synergistic or additive effects through inhibition of ERCC1 expression in cervical adenocarcinoma cells. Therefore, it is possible that a combination therapy of cisplatin and 5-FU or 5-FU derivatives constitutes an ideal treatment regimen, from the ERCC1 inhibition point of view in cervical adenocarcinoma.

Cyclooxygenase (COX)-2 inhibitors have been reported to potentially modulate the resistance of cancer cells to chemotherapeutic drugs by affecting multidrug resistance 1 (MDR1) expression. In the present study, we investigated the association between COX-2 and MDR1 expression in endometrial cancers and evaluated the effects of the COX-2 inhibitor, etodolac, in combination with paclitaxel on paclitaxel-resistant endometrial cancer cells. The relationship between COX-2 and MDR1 mRNA expression was examined by quantitative PCR in 36 endometrial cancer specimens. The paclitaxel-resistant cell line OMC-2P was established from OMC-2 cells. Paclitaxel (1 µg/ml) with or without etodolac (10 µg/ml) was added to OMC-2 and OMC-2P cells, and COX-2 and MDR1 mRNA expression levels were examined. The concentration of prostaglandin E2 (PGE2) in the supernatant of each cell line was examined by enzyme-linked immunosorbent assay. The function of MDR1 was determined by intracellular accumulation of rhodamine 123 using flow cytometry, and the concentration of intracellular paclitaxel was determined by high-performance liquid chromatography. We found a positive relationship between COX-2 and MDR1 mRNA expression in endometrial cancer. Both COX-2 mRNA expression and PGE2 production were elevated in resistant OMC-2P cells when compared to non-resistant OMC-2 cells. Additionally, MDR1 mRNA expression was markedly upregulated in OMC-2P cells. In OMC-2 cells, COX-2 and MDR1 mRNA levels were significantly upregulated by paclitaxel treatment and downregulated by co-administration with etodolac. In OMC-2P cells, COX-2 mRNA expression was also significantly upregulated by paclitaxel treatment and tended to be downregulated by co-administration with etodolac. Moreover, co-administration of paclitaxel and etodolac suppressed the induction of MDR1 mRNA. Rhodamine 123 efflux was increased in OMC-2P cells when compared to the efflux in the OMC-2 cells and was increased in response to paclitaxel treatment. Co-administration of paclitaxel and etodolac in both cell lines resulted in decreased rhodamine 123 efflux. The actual concentration of intracellular paclitaxel in OMC-2P cells was significantly lower than that in OMC-2 cells treated with paclitaxel alone and was significantly increased after co-administration of paclitaxel and etodolac. These findings suggest that paclitaxel resistance may be associated with COX-2 and MDR1 expression in cancer cells. Co-administration of COX-2 inhibitors and paclitaxel may have a key role in modulating or overcoming paclitaxel resistance in endometrial cancers.

The prognosis of advanced ovarian cancer primarily depends on maximal surgical debulking and chemosensitivity of the tumor. Neo-adjuvant chemotherapy(NAC), maintenance chemotherapy, and interval debulking surgery(IDS)are sometimes used to improve the prognosis of advanced ovarian cancer patients. In this study, we evaluated the outcomes of these therapeutic options in the treatment of FIGO stage III and IV ovarian cancers with intraperitoneal dissemination.Fifty patients with FIGO stage IIIc and IV ovarian cancer were evaluated. Progression-free survival(PFS)and overall survival(OS)were compared between different patient groups, including patients who underwent optimal surgery versus suboptimal surgery, patients who received NAC versus those who did not, patients who received 6 cycles of postoperative adjuvant chemotherapy versus those who received more than 7 cycles, and patients who underwent IDS versus those who did not.1 ) The 5- and 10-year OS rates were 52% and 21%, respectively. 2 ) Patients in the optimal surgery group experienced significantly longer PFS than patients in the suboptimal surgery group(p=0. 04). 3) Although NAC increased the possible rate of optimal surgery from 31. 2% to 66. 7%, no significant differences in PFS or OS were observed between patients who did and did not receive NAC. 4 ) Patients who underwent more than 7 cycles of adjuvant chemotherapy after suboptimal surgery experienced significantly longer OS(p=0. 001)and a tendency toward longer PFS(p=0. 07)compared to patients who received 6 cycles of adjuvant chemotherapy. 5 ) Patients who achieved a complete response(CR)following adjuvant chemotherapy after suboptimal surgery experienced significantly longer PFS(p=0. 001)and OS(p=0. 001) compared to patients who did not obtain CR. Moreover, patients who underwent IDS and who did not obtain a CR after adjuvant chemotherapy tended to experience longer PFS than patients who did not undergo IDS(p=0. 07).The results of this study are essentially compatible with those of recent randomized controlled trials(RCTs) evaluating NAC, maintenance chemotherapy, and IDS in advanced ovarian cancer. We hope to obtain additional RCT results that will allow improvement of the prognosis of advanced ovarian cancer patients.

COX-2 is highly expressed in endometrial cancers, suggesting that a selective COX-2 inhibitor could be valuable for treating endometrial cancers that overexpress COX-2. In this study, we investigated the anti-tumor effects of the selective COX-2 inhibitor etodolac on endometrial cancer patients.Etodolac (400 mg, bid, for 2 weeks) was administered preoperatively to 21 endometrial cancer patients who had provided informed consent. Using pre-treatment biopsies and post-treatment surgical specimens, the expression levels of COX-2, Ki-67, p53, p21, p27, and cyclin D1 were evaluated by immunohistochemistry and the apoptotic index (AI) was determined by TUNEL staining. Preoperative biopsies and surgical specimens from 32 patients with endometrial cancer not treated with etodolac served as controls.Surgical specimens from COX-2 positive endometrial cancer patients treated with etodolac had significantly reduced expression levels of COX-2, Ki-67, p53, p21, p27, and cyclin D1 as determined by immunohistochemistry, while AI was not affected. These markers were unchanged for COX-2 negative endometrial cancer patients treated with etodolac and the control group.The selective COX-2 inhibitor etodolac showed anti-proliferative effects by suppressing COX-2 and cell-cycle regulator protein expression in patients with endometrial cancer positive for COX-2 expression. This study demonstrates that a selective COX-2 inhibitor is a potentially beneficial treatment for COX-2 positive endometrial cancers.

An empirical law τDIDL =const has been found for the lifetime τD of the double layers (DL) observed in a linear turbulent‐heating device NU‐II [Phys. Fluids 28, 703 (1985)], where IDL is the current passing through the DL.

Time‐ and space‐resolved measurements of strong double layers (DLs) have been carried out for the first time on a linear turbulent‐heating device, together with those of fluctuation spectra and precise current measurements. A stable stong DL is formed even when the electric current through the DL is less than the so‐called Bohm value. Discussion of the formation and decay processes is given, indicating a transition from an ion‐acoustic DL to a monotonic DL.

Simulations based on the Vlasov–Poisson scheme are carried out to observe the temporal and spatial development of dopuble layers (DLs) in a linear mirror field. Simulation results show that the magnetic mirrors have a substantial effect in reducing the current passing through the DL. Development of a negative potential region on the low potential side of the DL is also observed, in agreement with the experimental results. The observed strong DLs appear to be formed, triggered by the ion‐acoustic instability.