Efficacy of immune checkpoint inhibitors in alveolar soft-part sarcoma: results from a retrospective worldwide registry.

BACKGROUND: Conventional cytotoxic drugs are not effective in alveolar soft-part sarcoma (ASPS). Immune checkpoint (programmed cell death protein 1/programmed death-ligand 1) inhibitors (ICIs) are promising drugs in ASPS. A worldwide registry explored the efficacy of ICI in ASPS. MATERIALS AND METHODS: Data from adult patients diagnosed with ASPS and treated with ICI for advanced disease in expert sarcoma centers from Europe, Australia and North America were retrospectively collected, including demographics and data related to treatments and outcome. RESULTS: Seventy-six ASPS patients, with a median age at diagnosis of 25 years (range 3-61 years), were registered. All patients received ICI for metastatic disease. Immunotherapy regimens consisted of monotherapy in 38 patients (50%) and combination in 38 (50%) (23 with a tyrosine kinase inhibitor). Among the 68 assessable patients, there were 3 complete responses and 34 partial responses, translating into an overall response rate of 54.4%. After a median follow-up of 36 months [95% confidence interval (CI) 32-40 months] since the start of immunotherapy, 45 (59%) patients have progressed on ICI, with a median progression-free survival (PFS) of 16.3 months (95% CI 8-25 months). Receiving ICI in first line (P = 0.042) and achieving an objective response (P = 0.043) correlated with a better PFS. Median estimated overall survival (OS) from ICI initiation has not been reached. The 12-month and 24-month OS rates were 94% and 81%, respectively. CONCLUSIONS: This registry constitutes the largest available series of ASPS treated with ICI. Our results suggest that the ICI treatment provides long-lasting disease control and prolonged OS in patients with advanced ASPS, an ultra-rare entity with limited active therapeutic options.

Imaging-based prostate cancer screening among BRCA mutation carriers-results from the first round of screening.

BACKGROUND: Male-carriers of BRCA1/2 gene mutations have an increased risk of prostate cancer (PCa) with a more aggressive phenotype. Current screening-guidelines suggest the use of prostate-specific antigen (PSA) only among BRCA2 carriers. Female carriers have extensive guidelines that include imaging. Our objective was to test the prevalence of PCa among BRCA carriers and examine screening strategies, using PSA and multiparametric magnetic resonance imaging (mpMRI). PATIENTS AND METHODS: We recruited men aged 40-70 years with BRCA1/2 germline mutations and no prior history of prostate biopsy. All men underwent an initial round of screening which included PSA, and prostate mpMRI. PSA was considered elevated using an age-stratified threshold of ≥1 ng/ml for 40-50 years of age, ≥2 ng/ml for 50-60 years of age, and 2.5 ng/ml for 60-70 years of age. Men with elevated PSA and/or suspicious lesion on mpMRI were offered a prostate biopsy. PSA levels, MRI findings, PCa incidence, and tumor characteristics were evaluated. Decision curve analysis was used to compare screening strategies. RESULTS: We recruited 188 men (108 BRCA1, 80 BRCA2), mean age 54 years (9.8). One hundred and ten (57%) had either elevated age-stratified PSA (75; 40%), a suspicious MRI lesion (67; 36%), or both (32; 17%). Of these, 92 (85%) agreed to perform a prostate biopsy. Sixteen (8.5%) were diagnosed with PCa; 44% of the tumors were classified as intermediate- or high-risk disease. mpMRI-based screening missed only one of the cancers (6%), while age-stratified PSA would have missed five (31%). Decision curve analysis showed that mpMRI screening, regardless of PSA, had the highest net benefit for PCa diagnosis, especially among men younger than 55 years of age. We found no difference in the risk of PCa between BRCA1 and BRCA2 (8.3% versus 8.7%, P = 0.91). Ninety percent had a Jewish founder mutation, thus the results cannot be generalized to all ethnic groups. CONCLUSIONS: PCa is prevalent among BRCA carriers. Age may affect screening strategy for PCa in this population. Young carriers could benefit from initial MRI screening. BRCA carriers aged older than 55 years should use PSA and be referred to mpMRI if elevated. TRIAL REGISTRATION: ClinicalTrial.gov ID: NCT02053805.

A randomised phase II trial of three dosing regimens of radium-223 in patients with bone metastatic castration-resistant prostate cancer.

BACKGROUND: Radium-223 prolongs overall survival and delays symptomatic skeletal events (SSEs) in patients with metastatic castration-resistant prostate cancer (mCRPC) and bone metastases. The approved radium-223 regimen is 55 kBq/kg every 4 weeks (q4w) for six cycles (standard dose). We investigated different radium-223 regimens in patients with mCRPC. PATIENTS AND METHODS: Patients were randomised 1 : 1 : 1 to radium-223 standard-dose, high-dose (88 kBq/kg q4w for six cycles) or extended-schedule arms (55 kBq/kg q4w for 12 cycles). The primary end point, SSE-free survival (SSE-FS), was compared in patients treated with a high- versus standard-dose regimen, or with a standard dose in an extended (>6 to 12 cycles) versus standard schedule (six cycles). RESULTS: A total of 391 patients were randomised; baseline characteristics were balanced between arms. On-treatment SSEs developed in 37/130 (28%), 42/130 (32%) and 48/131 (37%) patients in the standard-dose, high-dose and extended-schedule arms, respectively. There was no statistically significant difference in SSE-FS in the high- versus standard-dose arms [median 12.9 months versus 12.3 months; hazard ratio (HR) 1.06, 80% confidence interval (CI) 0.88-1.27, P = 0.70], and in the extended- versus standard-schedule arms (median 10.8 months versus 13.2 months; HR 1.26, 80% CI 0.94-1.69, P = 0.31). Overall survival in the three treatment arms was similar. As many as 370 (95%) patients received treatment (median of six cycles) in each arm. Grade ≥3 treatment-emergent adverse events (TEAEs) affected 34% of patients in the standard-dose, 48% in the high-dose and 53% in the extended-schedule arm, causing permanent discontinuation in 9%, 16% and 17% of patients, respectively. CONCLUSION: Radium-223 high-dose or extended-schedule regimens resulted in no change in SSE-FS or other efficacy end points and were associated with more grade ≥3 TEAEs. The extended-schedule regimen (beyond six doses) could not be implemented in a large proportion of patients due to disease progression. Therefore, the standard-dose schedule remains one of the standard therapies for patients with symptomatic mCRPC. TRIAL REGISTRATION: ClinicalTrials.govNCT02023697.

Re-treatment with radium-223: first experience from an international, open-label, phase I/II study in patients with castration-resistant prostate cancer and bone metastases.

BACKGROUND: Six radium-223 injections at 4-week intervals is indicated for patients with castration-resistant prostate cancer and symptomatic bone metastases. However, patients usually develop disease progression after initial treatment. This prospective phase I/II study assessed re-treatment safety and efficacy of up to six additional radium-223 injections. PATIENTS AND METHODS: Patients had castration-resistant prostate cancer and bone metastases and six initial radium-223 injections with no on-treatment bone progression; all had subsequent radiologic or clinical progression. Concomitant agents were allowed at investigator discretion, excluding chemotherapy and initiation of new abiraterone or enzalutamide. The primary endpoint was safety; additional exploratory endpoints included time to radiographic bone progression, time to total alkaline phosphatase and prostate-specific antigen progression, radiographic progression-free survival, overall survival, time to first symptomatic skeletal event (SSE), SSE-free survival, and time to pain progression. RESULTS: Among 44 patients, 29 (66%) received all six re-treatment injections. Median time from end of initial radium-223 treatment was 6 months. Forty-one (93%) reported ≥1 treatment-emergent adverse event. No grade 4-5 hematologic treatment-emergent adverse events occurred. Only one (2%) patient had radiographic bone progression; eight (18%) had radiographic soft tissue tumor progression (three lymph node and five visceral metastases). Median times to total alkaline phosphatase and prostate-specific antigen progression were not reached and 2.2 months, respectively. Median radiographic progression-free survival was 9.9 months (12.8-month maximum follow-up). Five (11%) patients died and eight (18%) experienced first SSEs. Median overall survival, time to first SSE, and SSE-free survival were not reached. Five (14%) of 36 evaluable patients (baseline worst pain score ≤7) had pain progression. After 2 years of follow-up, 28 (64%) patients died, and the median overall survival was 24.4 months. CONCLUSIONS: Re-treatment with a second course of six radium-223 injections after disease progression is well tolerated, with minimal hematologic toxicity and low radiographic bone progression rates in this small study with limited follow-up. Favorable safety and early effects on disease progression indicate that radium-223 re-treatment is feasible and warrants further evaluation in larger prospective trials.

Imaging response during therapy with radium-223 for castration-resistant prostate cancer with bone metastases-analysis of an international multicenter database.

BACKGROUND: The imaging response to radium-223 therapy is at present poorly described. We aimed to describe the imaging response to radium-223 treatment. METHODS: We retrospectively evaluated the computed tomography (CT) and bone scintigraphy response of metastatic castration-resistant prostate cancer (CRPC) patients treated with radium-223, in eight centers in three countries. RESULTS: A total of 130 patients were included, the majority (n=84, 65%) received radium-223 post docetaxel. Thirty-four of 99 patients with available data (34%) received concomitant abiraterone or enzalutamide. A total of 54% (n=70) patients completed the planned six injections of radium-223. In patients with available data, a transient increase in bone metastases-related pain was observed in 27% (n=33/124) and an improvement of bone metastases-related pain on treatment with radium-223 was noted in 49% of patients (n=61/124). At 3 and 6 months of treatment with radium-223, bone imaging showed stable disease in 74% (n=84/113) and 94% of patients (n=93/99) with available data, respectively. An increase in the number of bone lesions was documented at 3 months compared with baseline in 26% (n=29/113) and at 6 months compared with 3 months in 6% of patients (n=6/99), respectively. Radiological extraskeletal disease progression occurred in 46% of patients (n=57/124) with available CT data at 3 and/or 6 months. CONCLUSIONS: Progression of bone metastases during radium-223 therapy is uncommon. A bone flare (pain and/or radiological) may be noted during the first 3 months, and should not be confused with progression. Imaging by CT scan should be considered after three and six doses of radium-223 to rule out extraskeletal disease progression.

Hematopoietic progenitor cell collection after autologous transplant for multiple myeloma: low platelet count predicts for poor collection and sole use of resulting graft enhances risk of myelodysplasia.

Collection of hematopoietic progenitor cells (HPC) after previous autologous hematopoietic progenitor cell transplant (aHCT) was studied in 221 patients with multiple myeloma (MM). With a total of 333 collections, the median number of CD34+ cells collected was 4.7 × 10(6) CD34+ cells/kg, and 74% of the patients collected ≥ 2.5 × 10(6) CD34+ cells/kg. Among 26 variables examined, the strongest predictor for poor collection was a platelet count <100 × 10(6)/l before mobilization (P<0.001). A subsequent aHCT was performed in 154 of the 221 patients. Sole use of HPC procured after aHCT in 86 patients was associated with delayed platelet recovery (P<0.001) and linked to development of myelodysplastic syndrome (MDS)-associated cytogenetic abnormalities (MDS-CA; P=0.027, odds ratio (OR) 10.34) and a tendency towards clinical MDS/acute myeloid leukemia (AML; P=0.091, OR 3.57). However, treatment-related mortality (P=0.766) and time to absolute neutrophil count recovery ≥0.5 × 10(9)/l (P=0.879) were similar to when a pre-aHCT graft was used. Indeed, adding HPC collected before any aHCT neutralized the risk of MDS-CA or MDS/AML. Therefore, we advise generous initial HPC collection to broaden the salvage armamentarium for patients with MM.

DNA methylation profiles delineate epigenetic heterogeneity in seminoma and non-seminoma.

BACKGROUND: It remains important to understand the biology and identify biomarkers for less studied cancers like testicular cancer. The purpose of this study was to determine the methylation frequency of several cancer-related genes in different histological types of testicular cancer and normal testis tissues (NT). METHODS: DNA was isolated from 43 seminomas (SEs), 14 non-SEs (NSEs) and 23 NT, and was assayed for promoter methylation status of 15 genes by quantitative methylation-specific PCR. The methylation status was evaluated for an association with cancer, and between SEs and NSEs. RESULTS: We found differential methylation pattern in SEs and NSEs. MGMT, VGF, ER-ß and FKBP4 were predominately methylated in NSEs compared with SEs. APC and hMLH1 are shown to be significantly more methylated in both subtypes in comparison with NT. When combining APC, hMLH1, ER-ß and FKBP4, it is possible to identify 86% of the NSEs, whereas only 7% of the SEs. CONCLUSIONS: Our results indicate that the methylation profile of cancer-associated genes in testicular cancer correlates with histological types and show cancer-specific pattern for certain genes. Further methylation analysis, in a larger cohort is needed to elucidate their role in testicular cancer development and potential for therapy, early detection and disease monitoring.

The spectrum of clinical manifestations, outcome and treatment of pericardial tamponade in patients with systemic lupus erythematosus: a retrospective study and literature review.

Pericardial effusions causing pericardial tamponade are rare in patients with systemic lupus erythematosus (SLE). The goal of this study is to describe in detail the clinical and laboratory characteristics of a group of patients with pericardial effusions and pericardial tamponade secondary to SLE. We retrospectively reviewed the records of 71 patients with SLE, admitted to our Hospital between 1985 and 2006 with a diagnosis of pericarditis, pericardial effusion and tamponade. Clinical features in the patients with tamponade were compared with those with pericardial effusions without tamponade. Pericardial effusion and SLE was confirmed in 41 patients. Pericardial tamponade occurred in nine of these patients (21.9%) at the time of presentation. All tamponade patients were women. Patients with pericardial effusions who developed tamponade had a statistically significant (P = 0.05) lower C4 level as compared with patients who did not develop tamponade. A pericardial window was required in five patients even though the patients were receiving high-dose corticosteroids. In the present series, all patients with tamponade were treated with high-dose corticosteroids though five of nine patients required a pericardial window in contrast to previous studies. A low C4 level at presentation was predictive of the development of tamponade physiology.

Quantitative assessment of promoter methylation profiles in thyroid neoplasms.

CONTEXT: Cancer-specific molecular markers are needed to supplement the cytopathological assessment of thyroid tumors, because a majority of patients with cytologically indeterminate nodules currently undergo thyroidectomy without a definitive diagnosis. OBJECTIVE: The aim of this study was the quantitative assessment of promoter hypermethylation and its relation to the BRAF mutation in thyroid tumors. DESIGN: Quantitative hypermethylation of Rassf1A, TSHR, RAR-beta2, DAPK, S100, p16, CDH1, CALCA, TIMP3, TGF-beta, and GSTpi was tested on a cohort of 82 benign and malignant thyroid tumors and five thyroid cancer cell lines. SETTING: The study was conducted at a tertiary research hospital. PATIENTS: Patients underwent surgical resection for a thyroid tumor from 2000 to 2003 at our institution. INTERVENTIONS: There were no interventions. MAIN OUTCOME MEASURE: Final surgical pathology diagnosis was the main outcome measure. RESULTS: Thyroid tumors showed hypermethylation for the following markers: Rassf1A, TSHR, RAR-beta2, DAPK, CDH1, TIMP3, and TGF-beta. A trend toward multiple hypermethylation was evident in cancer tissues, with hypermethylation of two or more markers detectable in 25% of hyperplasias, 38% of adenomas, 48% of thyroid cancers, and 100% of cell lines. A rank correlation analysis of marker hypermethylation suggests that a subset of these markers is epigenetically modified in concert, which may reflect an organ-specific regulation process. Furthermore, a positive correlation was found between the BRAF mutation and RAR-beta2, and a negative correlation was found between the BRAF mutation and Rassf1A. CONCLUSIONS: Methylation-induced gene silencing appears to affect multiple genes in thyroid tissue and increases with cancer progression. Additional markers with better discriminatory power between benign and malignant samples are needed for the diagnostic assessment of cytologically indeterminate thyroid nodules.

Developing a free supportive care program for cancer patients within an integrative medicine clinic.

The cancer patient's journey not only includes a threat to one's life, but the need to face many medical and emotional challenges. The free Cancer Supportive Care Program (CSCP) within the Center for Integrative Medicine Clinic at Stanford University Hospital and Clinics has been identified as a successful model for helping patients to deal with these challenges. Its programs include informational lectures, support groups, chair massages, exercise, alternative modality classes, a Life Tapes Project, an informational website, and a bimonthly newsletter available free to anybody touched by cancer. Now in its third year, this program benefits from a blending of leadership resources, availability of space, institutional agreement on patient need and funds from private and corporate donations. By presenting the basic premises of the Cancer Supportive Care program and outlining specifics about the program, institutions in various national and international demographic regions may implement similar programs according to their resources and the needs of patients. It is our hope that the CSCP can become a model for the development of similar programs in various parts of the United States and abroad.

Value of chest CT scans in routine ovarian carcinoma follow-up.

OBJECTIVE: The purpose of our study was to examine the role of chest CT scans in routine follow-up of patients who had been treated for ovarian carcinoma. MATERIALS AND METHODS: The radiologic follow-up of 127 women with metatastic ovarian carcinoma who had undergone surgery and chemotherapy between 1985 and 1996 was reviewed. In reviewing each patient's medical record, we determined whether a chest CT scan had been obtained, and if so, how many had been obtained during the patient's follow-up period. For patients with a chest CT scan, an analysis of the presence of disease in the thorax and its relation to disease in the abdomen and pelvis, as revealed on CT images, was performed. RESULTS: Of the patients whose cases were examined, 82 (65%) had had at least one chest CT scan obtained, with more than 50% having had three or more scans. Thirty-two (39%) patients had no radiologic evidence of disease. Twenty-eight (34%) showed disease in the abdomen or pelvis but no disease in the chest. Eighteen (22%) had both chest and abdominal or pelvic CT scans that indicated disease. In all of these patients, abdominal or pelvic disease had appeared on scans before spreading to the chest. Four (5%) of the patients had isolated chest disease. The rate of lung metastases from ovarian carcinoma in our series was 6%. In all of these patients, pulmonary metastases were preceded either by abdominal or pelvic disease or by a rise in tumor markers. CONCLUSION: Pulmonary metastases in ovarian carcinoma are rare and usually preceded by recurrence of carcinoma in the abdomen or pelvis. We suggest that chest CT scanning could be eliminated in the routine follow-up of patients who have been treated for ovarian carcinoma; yet it should be performed for those patients with elevated serum tumor markers but without evidence of abdominal or pelvic disease.

Differences in the locational attainment of immigrant and native-born households with children in New York City.

In this paper we use a data set created especially for New York City to evaluate whether the locational attainment of households with children, as indicated by the context of the neighborhoods in which they live, varies by their immigrant status. In addition, we evaluate whether the relationship between immigrant status and neighborhood conditions varies by the householder's race/ethnicity. Overall, when compared with native-born households with children, immigrant households with children live in neighborhoods of lower quality, characterized by higher teenage fertility rates and higher percentages of students in local schools scoring below grade level in math and of persons receiving AFDC, but lower rates of juvenile detention. Further analyses, however, revealed that race/ethnicity is far more potent than immigrant status per se in predicting where households with children live.

A rapid food screener to assess fat and fruit and vegetable intake.

BACKGROUND: The U.S. Preventive Services Task Force recommends that Americans lower dietary fat and cholesterol intake and increase fiber and fruit/vegetables to reduce prevalence of heart disease, cancer, stroke, hypertension, obesity, and non-insulin-dependent diabetes mellitus in the United States. To provide preventive services to all, a rapid, inexpensive, and valid method of assessing dietary intake is needed. METHODS: We used a one-page food intake screener based on national nutrition data. Respondents can complete and score the screener in a few minutes and can receive immediate, brief feedback. Two hundred adults self-administered the food screener. We compared fat, fiber, and fruit/vegetable intake estimates derived from the screener with estimates from a full-length, 100-item validated questionnaire. RESULTS: The screener was effective in identifying persons with high-fat intake, or low-fruit/vegetable intake. We found correlations of 0.6-0.7 (p<0. 0001) for total fat, saturated fat, cholesterol, and fruit/vegetable intake. The screener could identify persons with high percentages of calories from fat, total fat, saturated fat, or cholesterol, and persons with low intakes of vitamin C, fiber, or potassium. CONCLUSIONS: This screener is a useful tool for quickly monitoring patients' diets. The health care provider can use it as a prelude to brief counseling or as the first stage of triage. Persons who score poorly can be referred for more extensive evaluation by low-cost paper-and-pencil methods. Those who still have poor scores at the second stage ultimately can be referred for in-person counseling.

State funding of comprehensive primary medical care service programs for medically underserved populations.

OBJECTIVES: This study examined the availability of state funding for comprehensive primary care programs and the need for primary care subsidies for medically underserved communities. METHODS: A brief questionnaire was used to ask health agencies in all 50 states whether their state funded a program that met our definition of comprehensive primary medical care practice programs. An in-depth written survey instrument was then administered to the states with programs. RESULTS: Almost half of all states provide some funds for the development and/or operation of comprehensive primary medical care practices. Expenditures in most states were found to be relatively modest in comparison with both federal funding and the total level of unmet need for primary care. States that subsidize primary care practices tend to follow the model established under the federal health centers program. CONCLUSIONS: The findings suggest the continued viability of the health center model of care, as well as the presence of some state support for such a program. However, in light of limited state resources for the development and operation of comprehensive practices, a continued and significant federal effort is imperative.

Linking primary care centers and hospitals.

Primary care centers (PCCs) are increasingly entering into linkages with hospitals that go far beyond the traditional arrangements in which the hospitals serve as backups to the PCCs. The linkages can be for managed care purposes, for training of health professionals in primary care settings, or for other reasons. This article explores the advantages of such arrangements, the organizational forms that the linkages can take, the legal issues, and negotiating the deal.

Modulation of learned helplessness by 5-hydroxytryptamine2A receptor antisense oligodeoxynucleotides.

Serotonergic systems have been implicated in the pathogenesis of major depression in humans as well as in learned helplessness (LH), an animal model of depression. To understand the significance of neuronal responses in depression and LH that are mediated by serotonin (5-hydroxytryptamine, 5HT) receptors, we used intracerebroventricular injections to introduce a unique antisense oligonucleotide (ASO) to the 5HT2A receptor and determined its effect on LH behavior in Sprague-Dawley rats as determined by an escape-avoidance strategy. Of the rats injected with the 5HT2A receptor ASO, 8/16 rats met criteria for LH. By contrast, only 1/15 of the control group injected with 5HT2A sense oligonucleotide (SO) met criteria for LH. Quantitative receptor autoradiography revealed significant differences in 5HT2A receptor density between ASO and control sense oligonucleotides (SO), in close proximity to the injection site. Significant decreases in 5HT2A receptor density caused by oligonucleotide blockade were found in the CA3 hippocampal region. These data support the view that central 5HT, mediated by the 5HT2A receptor, participates in regulating behaviors that are affected by inescapable stress, and that the induction of behavioral depression may be specifically regulated via serotonergic pathways that terminate in this hippocampal subfield.

Race and ethnicity in housing: turnover in New York City, 1978-1987.

This study examines the patterns and predictors of housing turnovers among non-Hispanic whites, non-Hispanic blacks, Puerto Ricans, and other Hispanics in New York City during 1978-1987 to assess whether access to housing is distributed differentially by race and ethnicity. The data are taken from the triennial New York City Housing and Vacancy Survey. After controlling for household preferences, purchasing power, and quality characteristics of the housing unit, multinomial logistic regression results show the most consistent and significant predictors of turnover to be geographic and market-sector attributes. The findings suggest the presence of structural constraints in the housing market which effectively channel racial/ethnic groups to separate neighborhoods. The overall results are reminiscent of early studies of neighborhood transition by Duncan and Duncan (1957) and Taeuber and Taeuber (1965), and show that little progress has been made toward achieving equality in housing or informal social contact between racial/ethnic groups.

Effect of reduced temperatures and brefeldin A on prolactin secretion and on subcellular distribution of the secretory product and membrane antigens in GH3 pituitary cells.

The effects of reduced temperatures (20, 15 or 10 degrees C) and brefeldin A (BFA) on prolactin (PRL) secretion in the GH3 rat pituitary cell line have been compared. Both treatments inhibit PRL release to different extents. Ultrastructural immunocytochemistry reveals that, depending on the treatment, PRL is blocked at different steps during its intracellular transit. The temperatures of 20 and 15 degrees C block the PRL transport at one face of the Golgi stacks whereas both the temperature of 10 degrees C and BFA treatment induce an arrest of PRL at the level of the rough endoplasmic reticulum (RER) cisternae. Moreover, exposure to 10 degrees C or BFA induces an accumulation of a specific Golgi membrane antigen in the dilated RER structures. However, although disorganized and no longer definable under BFA treatment, the Golgi apparatus remains visible at 10 degrees C. These two last treatments cause also an increase in the number of partly rough, partly smooth tubular structures tentatively called 'paired cisternae'.

Rapid and transient reorganization of the cytoskeleton in GH3B6 cells during short-term exposure to thyroliberin.

The cytoskeletal organization of the rat pituitary tumor cell line GH3B6 was analysed using immunofluorescence, in basal conditions and after stimulation by thyroliberin (TRH). Under basal conditions, a dense and entangled cytoplasmic microtubule network, a perinuclear cage of cytokeratin fibers, and a diffuse distribution of F-actin were revealed. Short-term stimulation of these cells by TRH induces a first early phase of PRL release (0-2 min), concomitant with a rarefaction of cytoplasmic PRL-containing granules, followed by a second plateau phase (5-30 min), concomitant with modifications of the Golgi zone. We show that TRH induced early and transient modifications in the cytoskeletal distribution during these short periods of stimulation. First, after 2 min of stimulation, small fluorescent tubulin blebs appeared under the plasma membrane. Then, after 5 min they disappeared, and a thin actin network, accentuated by thicker fibers, organized transiently in the cytoplasm. After 30 min, the microtubules and cytokeratin networks had extended throughout the cytoplasm and the actin distribution was diffuse again. So, in this study, we have shown the existence of a parallelism between the redistribution of intracellular PRL compartments and the reorganization of cytoskeletal elements, during exposure to TRH. We could not clearly correlate these modifications with transduction mechanisms involved in TRH action.