Targeting pancreatic cancer metabolic dependencies through glutamine antagonism

Pancreatic ductal adenocarcinoma (PDAC) cells use glutamine (Gln) to support proliferation and redox balance. Early attempts to inhibit Gln metabolism using glutaminase inhibitors resulted in rapid metabolic reprogramming and therapeutic resistance. Here, we demonstrated that treating PDAC cells with a Gln antagonist, 6-diazo-5-oxo-L-norleucine (DON), led to a metabolic crisis in vitro. In addition, we observed a profound decrease in tumor growth in several in vivo models using sirpiglenastat (DRP-104), a pro-drug version of DON that was designed to circumvent DON-associated toxicity. We found that extracellular signal-regulated kinase (ERK) signaling is increased as a compensatory mechanism. Combinatorial treatment with DRP-104 and trametinib led to a significant increase in survival in a syngeneic model of PDAC. These proof-of-concept studies suggested that broadly targeting Gln metabolism could provide a therapeutic avenue for PDAC. The combination with an ERK signaling pathway inhibitor could further improve the therapeutic outcome.

High-Dose Rate Brachytherapy Alone for Treatment of Unfavorable Intermediate Risk Prostate Cancer: A Propensity-Score Matched Analysis

PURPOSE/OBJECTIVE(S)

To demonstrate the feasibility of high-dose rate brachytherapy (HDR BT) as monotherapy for unfavorable intermediate risk (UIR) prostate cancer by comparing survival outcomes of HDR BT alone against external beam radiation therapy (EBRT) + HDR BT boost, +/- androgen deprivation therapy (ADT) using propensity-score matched (PSM) data.

MATERIALS/METHODS

This retrospective study queried two data registries collecting patient data from 1991 to present. 633 patients with UIR prostate cancer treated with HDR BT alone, HDR BT+EBRT or HDR+EBRT+ADT were included. HDR BT patients received 42-45Gy/6 fractions (fx) or 27 Gy/2 fx. For HDR BT+EBRT, the HDR dose was 20-24 Gy/2 fx, 24 Gy/4 fx, or 15 Gy/1 fx. EBRT patients received 45 Gy/25 fx to the prostate +/- pelvic nodes. GU/GI toxicities were graded according to the Common Terminology Criteria for Adverse Events (CTCAE) v5.0. Time-to-event analyses were carried out to evaluate the relationship between treatments and five primary endpoints of interest: freedom from biochemical recurrence (FFBC), freedom from distant metastasis (FFDM), freedom from local failure (FFLF), cancer specific survival (CSS), and overall survival (OS) at 5 years. PSM was performed with one-to-n matching. Logistic regression was used to estimate the respective propensity scores. The five potential confounders identified were T-stage, Gleason score, pre-treatment PSA, age, and percent positive cores. Balance was checked using the standardized mean difference of covariates. Univariate and multivariate analyses were conducted on the matched data. Toxicity analysis was performed via association between a change in pre- and post-treatment GU/GI toxicity status and the treatment group, as well as incidence of post-treatment severe GI/GU toxicity (grade 3 or higher) and the treatment group.

RESULTS

Univariate analysis with Kaplan-Meier method and log rank test comparison between the three cohorts demonstrated no significant difference in all survival outcomes FFBC, FFDM, FFLF, CSS, OS (p = 0.15, 0.19, 0.29, 0.57, 0.28, respectively). Multivariate analysis with Cox proportional hazard regression showed no differences in HR for FFBC and OS (p = 0.95, 0.11) with addition of EBRT, or with EBRT+ADT (p = 0.17, 0.24); no fit was obtainable for FFDM, CSS, FFLF. Toxicities between the three cohorts were not significantly different when comparing post-treatment and baseline GI/GU symptoms (p = 0.53/1). No Grade 2 or 3 GI toxicities were identified, while 8%/1% HDR patients, 10%/1% HDR+EBRT patients, and 12%/2% HDR+EBRT+ADT patients experienced Grade 2/3 GU toxicities. The incidence of grade 3 or higher GU toxicities between the three groups was not significantly different (p = 0.91).

CONCLUSION

This propensity-score matched study demonstrates the feasibility of HDR BT alone for effective treatment of UIR prostate cancer when compared to HDR+EBRT or HDR+EBRT+ADT, while potentially minimizing the added toxicities of EBRT and the undesirable side effect profile of ADT.

Autophagy supports mitochondrial metabolism through the regulation of iron homeostasis in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) cells maintain a high level of autophagy, allowing them to thrive in an austere microenvironment. However, the processes through which autophagy promotes PDAC growth and survival are still not fully understood. Here, we show that autophagy inhibition in PDAC alters mitochondrial function by losing succinate dehydrogenase complex iron sulfur subunit B expression by limiting the availability of the labile iron pool. PDAC uses autophagy to maintain iron homeostasis, while other tumor types assessed require macropinocytosis, with autophagy being dispensable. We observed that cancer-associated fibroblasts can provide bioavailable iron to PDAC cells, promoting resistance to autophagy ablation. To overcome this cross-talk, we used a low-iron diet and demonstrated that this augmented the response to autophagy inhibition therapy in PDAC-bearing mice. Our work highlights a critical link between autophagy, iron metabolism, and mitochondrial function that may have implications for PDAC progression.

Spontaneous hydrolysis and spurious metabolic properties of α-ketoglutarate esters

α-ketoglutarate (KG), also referred to as 2-oxoglutarate, is a key intermediate of cellular metabolism with pleiotropic functions. Cell-permeable esterified analogs are widely used to study how KG fuels bioenergetic and amino acid metabolism and DNA, RNA, and protein hydroxylation reactions, as cellular membranes are thought to be impermeable to KG. Here we show that esterified KG analogs rapidly hydrolyze in aqueous media, yielding KG that, in contrast to prevailing assumptions, imports into many cell lines. Esterified KG analogs exhibit spurious KG-independent effects on cellular metabolism, including extracellular acidification, arising from rapid hydrolysis and de-protonation of α-ketoesters, and significant analog-specific inhibitory effects on glycolysis or mitochondrial respiration. We observe that imported KG decarboxylates to succinate in the cytosol and contributes minimally to mitochondrial metabolism in many cell lines cultured in normal conditions. These findings demonstrate that nuclear and cytosolic KG-dependent reactions may derive KG from functionally distinct subcellular pools and sources.

Human Tumor-Associated Macrophage and Monocyte Transcriptional Landscapes Reveal Cancer-Specific Reprogramming, Biomarkers, and Therapeutic Targets

The roles of tumor-associated macrophages (TAMs) and circulating monocytes in human cancer are poorly understood. Here, we show that monocyte subpopulation distribution and transcriptomes are significantly altered by the presence of endometrial and breast cancer. Furthermore, TAMs from endometrial and breast cancers are transcriptionally distinct from monocytes and their respective tissue-resident macrophages. We identified a breast TAM signature that is highly enriched in aggressive breast cancer subtypes and associated with shorter disease-specific survival. We also identified an auto-regulatory loop between TAMs and cancer cells driven by tumor necrosis factor alpha involving SIGLEC1 and CCL8, which is self-reinforcing through the production of CSF1. Together these data provide direct evidence that monocyte and macrophage transcriptional landscapes are perturbed by cancer, reflecting patient outcomes.

Autophagy Sustains Pancreatic Cancer Growth through Both Cell-Autonomous and Nonautonomous Mechanisms

Autophagy has been shown to be elevated in pancreatic ductal adenocarcinoma (PDAC), and its role in promoting established tumor growth has made it a promising therapeutic target. However, due to limitations of prior mouse models as well as the lack of potent and selective autophagy inhibitors, the ability to fully assess the mechanistic basis of how autophagy supports pancreatic cancer has been limited. To test the feasibility of treating PDAC using autophagy inhibition and further our understanding of the mechanisms of protumor effects of autophagy, we developed a mouse model that allowed the acute and reversible inhibition of autophagy. We observed that autophagy inhibition causes significant tumor regression in an autochthonous mouse model of PDAC. A detailed analysis of these effects indicated that the tumor regression was likely multifactorial, involving both tumor cell-intrinsic and host effects. Thus, our study supports that autophagy inhibition in PDAC may have future utility in the treatment of pancreatic cancer and illustrates the importance of assessing complex biological processes in relevant autochthonous models.Significance: This work demonstrates that autophagy is critical pancreatic tumor maintenance through tumor cell-intrinsic and -extrinsic mechanisms. These results have direct clinical relevance to ongoing clinical trials as well as drug-development initiatives. Cancer Discov; 8(3); 276-87. ©2018 AACR.See related commentary by Noguera-Ortega and Amaravadi, p. 266This article is highlighted in the In This Issue feature, p. 253.

Predicting Outcomes Using the Heart Failure Survival Score in Adults with Moderate or Complex Congenital Heart Disease

BACKGROUND

Adults with congenital heart disease (CHD) face increased risk for morbidity and mortality with age, but few prognostic models exist.

OBJECTIVE

This study aims to assess whether the Heart Failure Survival Score (HFSS), which risk stratifies patients for heart transplantation, predicts outcomes in adults with moderate or complex CHD.

METHODS

This was a multicenter, retrospective study which identified 441 patients with moderate or complex CHD between 2005 and 2013, of whom 169 had all the HFSS parameters required to calculate the risk score. Because all study patients were deemed low risk by the HFSS, the score was dichotomized at the median (10.4). Outcomes included death, transplant or ventricular assist device (VAD), arrhythmia requiring treatment, nonelective cardiovascular (CV) hospitalizations, and the composite. Associations of mean HFSS and HFSS <10.4 with each outcome were assessed.

RESULTS

The cohort had mean ± standard deviation age of 33.6 ± 12.6 years, peak VO2 21.8 ± 7.5 mL/kg/min, HFSS of 10.45 ± 0.88, and median years follow-up of 2.7 (1.1, 5.2). There were five deaths (2.8%), no transplants or VADs, 25 arrhythmias (14.8%), 22 CV hospitalizations (13%), and 39 composites (23.1%). Lower mean HFSS was observed for patients who died (9.6 ± 0.83 vs. 10.5 ± 0.87, P = .02), arrhythmia requiring treatment (10.0 ± 0.70 vs. 10.5 ± 0.89, P = .005), CV hospitalizations (9.9 ± 0.73 vs. 10.5 ± 0.88, P = .002), and the composite (10.0 ± 0.70 vs. 10.6 ± 0.89, P < .001). The positive and negative predictive values of HFSS <10.4 for the composite were 34% and 88% respectively, with sensitivity and specificity 74% and 56%.

CONCLUSIONS

Although a low HFSS was significantly associated with outcomes, it did not adequately risk stratify adults with CHD, whose heterogeneous pathophysiology differs from that of the acquired heart failure population. Further studies are warranted to provide a more accurate prognosis.

STAT3 and sphingosine-1-phosphate in inflammation-associated colorectal cancer

Accumulated evidences have demonstrated that signal transducer and activator of transcription 3 (STAT3) is a critical link between inflammation and cancer. Multiple studies have indicated that persistent activation of STAT3 in epithelial/tumor cells in inflammation-associated colorectal cancer (CRC) is associated with sphingosine-1-phosphate (S1P) receptor signaling. In inflammatory response whereby interleukin (IL)-6 production is abundant, STAT3-mediated pathways were found to promote the activation of sphingosine kinases (SphK1 and SphK2) leading to the production of S1P. Reciprocally, S1P encourages the activation of STAT3 through a positive autocrine-loop signaling. The crosstalk between IL-6, STAT3 and sphingolipid regulated pathways may play an essential role in tumorigenesis and tumor progression in inflamed intestines. Therapeutics targeting both STAT3 and sphingolipid are therefore likely to contribute novel and more effective therapeutic strategies against inflammation-associated CRC.

Tissue-expressed B7-H1 critically controls intestinal inflammation

B7-H1 (PD-L1) on immune cells plays an important role in T cell coinhibition by binding its receptor PD-1. Here, we show that both human and mouse intestinal epithelium express B7-H1 and that B7-H1-deficient mice are highly susceptible to dextran sodium sulfate (DSS)- or trinitrobenzenesulfonic acid (TNBS)-induced gut injury. B7-H1 deficiency during intestinal inflammation leads to high mortality and morbidity, which are associated with severe pathological manifestations in the colon, including loss of epithelial integrity and overgrowth of commensal bacteria. Results from bone marrow chimeric and knockout mice show that B7-H1 expressed on intestinal parenchyma, but not on hematopoietic cells, controls intestinal inflammation in an adaptive immunity-independent fashion. Finally, we demonstrate that B7-H1 dampened intestinal inflammation by inhibiting tumor necrosis factor α (TNF-α) production and by stimulating interleukin 22 secretion from CD11c(+)CD11b(+) lamina propria cells. Thus, our data uncover a mechanism through which intestinal tissue-expressed B7-H1 functions as an essential ligand for innate immune cells to prevent gut inflammation.

STAT3 in epithelial cells regulates inflammation and tumor progression to malignant state in colon

Chronic inflammation is an important risk factor for the development of colorectal cancer; however, the mechanism of tumorigenesis especially tumor progression to malignancy in the inflamed colon is still unclear. Our study shows that epithelial signal transducer and activator of transcription 3 (STAT3), persistently activated in inflamed colon, is not required for inflammation-induced epithelial overproliferation and the development of early-stage tumors; however, it is essential for tumor progression to advanced malignancy. We found that one of the mechanisms that epithelial STAT3 regulates in tumor progression might be to modify leukocytic infiltration in the large intestine. Activation of epithelial STAT3 promotes the infiltration of the CD8+ lymphocyte population but inhibits the recruitment of regulatory T (Treg) lymphocytes. The loss of Stat3 in epithelial cells promoted the expression of cytokines/chemokines including CCL19, CCL28, and RANTES, which are known to be able to recruit Treg lymphocytes. Linked to these changes was the pathway mediated by sphingosine 1-phosphate receptor 1 and sphingosine 1-phosphate kinases, which is activated in colonic epithelial cells in inflamed colon with functional STAT3 but not in epithelial cells deleted of STAT3. Our data suggest that epithelial STAT3 plays a critical role in inflammation-induced tumor progression through regulation of leukocytic recruitment especially the infiltration of Treg cells in the large intestine.

A novel mouse model of inflammatory bowel disease links mammalian target of rapamycin-dependent hyperproliferation of colonic epithelium to inflammation-associated tumorigenesis

Inflammatory bowel disease (IBD) is a high-risk condition for human colorectal cancer. However, our mechanistic understanding of the link between inflammation and tumorigenesis in the colon is limited. Here we established a novel mouse model of colitis-associated cancer by genetically inactivating signal transducer and activator of transcription 3 (Stat3) in macrophages, with partial deletion in other myeloid and lymphoid cells. Inflammation developed in the colon of mutant mice spontaneously, and tumor lesions, including invasive carcinoma, arose in the inflamed region of the intestine with a frequency similar to that observed in human IBD patients. The development of both inflammation and tumors in the mutant mice required the presence of microflora. Indeed, inflammation was associated with disruption of colonic homeostasis, fulminant epithelial/tumor cell proliferation, and activation of the mammalian target of rapamycin (mTOR)-Stat3 pathway in epithelial and tumor cells. The activation of this pathway was essential for both the excess proliferation of epithelial/tumor cells and the disruption of colonic homeostasis in the mutant mice. Notably, a similar abnormal up-regulation of mTOR-Stat3 signaling was consistently observed in the colonic epithelial cells of human IBD patients with active disease. These studies demonstrate a novel mouse model of IBD-colorectal cancer progression in which disrupted immune regulation, mTOR-Stat3 signaling, and epithelial hyperproliferation are integrated and simultaneously linked to the development of malignancy.

A novel mouse model of inflammatory bowel disease links mammalian target of rapamycin-dependent hyperproliferation of colonic epithelium to inflammation-associated tumorigenesis

Inflammatory bowel disease (IBD) is a high-risk condition for human colorectal cancer. However, our mechanistic understanding of the link between inflammation and tumorigenesis in the colon is limited. Here we established a novel mouse model of colitis-associated cancer by genetically inactivating signal transducer and activator of transcription 3 (Stat3) in macrophages, with partial deletion in other myeloid and lymphoid cells. Inflammation developed in the colon of mutant mice spontaneously, and tumor lesions, including invasive carcinoma, arose in the inflamed region of the intestine with a frequency similar to that observed in human IBD patients. The development of both inflammation and tumors in the mutant mice required the presence of microflora. Indeed, inflammation was associated with disruption of colonic homeostasis, fulminant epithelial/tumor cell proliferation, and activation of the mammalian target of rapamycin (mTOR)-Stat3 pathway in epithelial and tumor cells. The activation of this pathway was essential for both the excess proliferation of epithelial/tumor cells and the disruption of colonic homeostasis in the mutant mice. Notably, a similar abnormal up-regulation of mTOR-Stat3 signaling was consistently observed in the colonic epithelial cells of human IBD patients with active disease. These studies demonstrate a novel mouse model of IBD-colorectal cancer progression in which disrupted immune regulation, mTOR-Stat3 signaling, and epithelial hyperproliferation are integrated and simultaneously linked to the development of malignancy.

Western-style diets induce oxidative stress and dysregulate immune responses in the colon in a mouse model of sporadic colon cancer

A Western-style diet (WD), defined by high-fat, low-calcium, and vitamin D content, is associated with increased risk of human colorectal cancer. Understanding molecular mechanisms altered by the WD is crucial to develop preventive and therapeutic strategies. Effects of a WD on the colonic transcriptome of C57Bl/6J mice, a model for sporadic colon cancer, were studied at endpoints before tumors occur. To assess whether a WD induces inflammatory changes, expression profiles of a broad spectrum of inflammatory proteins were performed and numbers of lamina propria macrophages were determined with semiquantitative morphometry. Transcriptome changes were translated into molecular interaction network maps and pathways. Pathways related to oxidative stress response; lipid, glutathione, and xenobiotic metabolism; and the immune response were perturbed by the WD. Several nuclear factor-erythroid 2-related factor 2- and aryl hydrocarbon receptor-dependent genes, including those coding for enzymes involved in phase 1 and 2 drug metabolism and oxidative stress responses, were induced. Oxidative stress was demonstrated by measurements of endogenous colonic redox-sensitive compound concentrations. Perturbations in immune response-related pathways, expression of inflammatory proteins, and increased numbers of lamina propria macrophages showed that the WD significantly alters the local colonic immune response. Collectively, these data suggest that consumption of a WD interferes with networks of related biological response pathways involving colonic lipid metabolism, oxidative stress, and the immune response. These new findings impact our understanding of links between consumption of WD and colon carcinogenesis, providing additional information for developing preventive means for decreasing colorectal cancer risk.

Vascular endothelial growth factor restores delayed tumor progression in tumors depleted of macrophages

Genetic depletion of macrophages in Polyoma Middle T oncoprotein (PyMT)-induced mammary tumors in mice delayed the angiogenic switch and the progression to malignancy. To determine whether vascular endothelial growth factor A (VEGF-A) produced by tumor-associated macrophages regulated the onset of the angiogenic switch, a genetic approach was used to restore expression of VEGF-A into tumors at the benign stages. This stimulated formation of a high-density vessel network and in macrophage-depleted mice, was followed by accelerated tumor progression. The expression of VEGF-A led to a massive infiltration into the tumor of leukocytes that were mostly macrophages. This study suggests that macrophage-produced VEGF regulates malignant progression through stimulating tumor angiogenesis, leukocytic infiltration and tumor cell invasion.

Lung tumor promotion by curcumin

Curcumin exhibits anti-inflammatory and antitumor activity and is being tested in clinical trials as a chemopreventive agent for colon cancer. Curcumin's chemopreventive activity was tested in a transgenic mouse model of lung cancer that expresses the human Ki-ras(G12C) allele in a doxycycline (DOX) inducible and lung-specific manner. The effects of curcumin were compared with the lung tumor promoter, butylated hydroxytoluene (BHT), and the lung cancer chemopreventive agent, sulindac. Treatment of DOX-induced mice with dietary curcumin increased tumor multiplicity (36.3 +/- 0.9 versus 24.3 +/- 0.2) and progression to later stage lesions, results which were similar to animals that were co-treated with DOX/BHT. Microscopic examination showed that the percentage of lung lesions that were adenomas and adenocarcinomas increased to 66% in DOX/BHT, 66% in DOX/curcumin and 49% in DOX/BHT/curcumin-treated groups relative to DOX only treated mice (19%). Immunohistochemical analysis also showed increased evidence of inflammation in DOX/BHT, DOX/curcumin and DOX/BHT/curcumin mice relative to DOX only treated mice. In contrast, co-treatment of DOX/BHT mice with 200 p.p.m. [DOSAGE ERROR CORRECTED] of sulindac inhibited the progression of lung lesions and reduced the inflammation. Lung tissue from DOX/curcumin-treated mice demonstrated a significant increase (33%; P = 0.01) in oxidative damage, as assessed by the levels of carbonyl protein formation, relative to DOX-treated control mice after 1 week on the curcumin diet. These results suggest that curcumin may exhibit organ-specific effects to enhance reactive oxygen species formation in the damaged lung epithelium of smokers and ex-smokers. Ongoing clinical trials thus may need to exclude smokers and ex-smokers in chemopreventive trials of curcumin.

Tumor-associated macrophages press the angiogenic switch in breast cancer

The development of a supportive vasculature is essential for tumor progression. In a mouse model of breast cancer, we found that tumor-associated macrophages that are recruited to the tumor just before malignant conversion are essential for the angiogenic switch. These findings establish a causal linkage to explain well-documented clinical correlations between macrophages, microvessel density, and poor prognosis in breast tumors.

Direct visualization of macrophage-assisted tumor cell intravasation in mammary tumors

Although the presence of macrophages in tumors has been correlated with poor prognosis, until now there was no direct observation of how macrophages are involved in hematogenous metastasis. In this study, we use multiphoton microscopy to show, for the first time, that tumor cell intravasation occurs in association with perivascular macrophages in mammary tumors. Furthermore, we show that perivascular macrophages of the mammary tumor are associated with tumor cell intravasation in the absence of local angiogenesis. These results show that the interaction between macrophages and tumor cells lying in close proximity defines a microenvironment that is directly involved in the intravasation of cancer cells in mammary tumors.

Macrophages regulate the angiogenic switch in a mouse model of breast cancer

The development of a tumor vasculature or access to the host vasculature is a crucial step for the survival and metastasis of malignant tumors. Although therapeutic strategies attempting to inhibit this step during tumor development are being developed, the biological regulation of this process is still largely unknown. Using a transgenic mouse susceptible to mammary cancer, PyMT mice, we have characterized the development of the vasculature in mammary tumors during their progression to malignancy. We show that the onset of the angiogenic switch, identified as the formation of a high-density vessel network, is closely associated with the transition to malignancy. More importantly, both the angiogenic switch and the progression to malignancy are regulated by infiltrated macrophages in the primary mammary tumors. Inhibition of the macrophage infiltration into the tumor delayed the angiogenic switch and malignant transition whereas genetic restoration of the macrophage population specifically in these tumors rescued the vessel phenotype. Furthermore, premature induction of macrophage infiltration into premalignant lesions promoted an early onset of the angiogenic switch independent of tumor progression. Taken together, this study shows that tumor-associated macrophages play a key role in promoting tumor angiogenesis, an essential step in the tumor progression to malignancy.

Treatment with rhenium-188-perrhenate and iodine-131 of NIS-expressing mammary cancer in a mouse model remarkably inhibited tumor growth

INTRODUCTION

Novel therapeutic modalities are needed for breast cancer patients in whom standard treatments are not effective. Mammary gland sodium/iodide symporter has been identified as a molecular target in breast cancers in humans and in some transgenic mouse models. We report the results of a therapy study with (131)I(-) and (188)ReO(4)(-) of breast cancer in polyoma middle T oncoprotein (PyMT) transgenic mice endogenously expressing the Na(+)/I(-) symporter (NIS).

METHODS

PyMT mice (12-13 weeks old) with one palpable tumor of 0.5-0.8 cm in diameter were used. For the therapy studies, PyMT mice were (1) treated with two intraperitoneal injections of 1.5 mCi of (188)ReO(4)(-) 1 week apart, (2) pretreated for 1 week with 5 microg of triiodothyronine (T3) followed by two intraperitoneal injections of 1.5 mCi of (131)I(-) 1 week apart or (3) left untreated. The tumor and normal organ uptakes were assessed by scintigraphic imaging. The thyroid function of treated and control animals was evaluated at the completion of the study by measuring the T3/thyroxine (T4) ratio in their blood.

RESULTS

There was significant uptake of (131)I(-) and (188)ReO(4)(-) in the primary palpable tumors as well as in nonpalpable tumors, stomachs and thyroids. The tumor uptake after the second injection was 10 times lower in comparison with the first injection. Tumor growth was significantly inhibited in both the (131)I(-) and (188)ReO(4)(-) groups in comparison with the control group, and tumors in the (188)ReO(4)(-) group increased in size significantly less than in the (131)I(-) group. The T3/T4 ratios were calculated to be 27 and 25 for the control group and the (188)ReO(4)(-) group, respectively; for (131)I(-), both the T3 and T4 levels were below detection limit, demonstrating much less effect on the thyroids of treatment with (188)ReO(4)(-) than with (131)I(-).

CONCLUSIONS

These results prove that NIS expression in breast tumors in animal models allows specific, efficient and safe treatment with a variety of radionuclides transported by NIS.

A paracrine loop between tumor cells and macrophages is required for tumor cell migration in mammary tumors

Invasion of tumor cells into the surrounding connective tissue and blood vessels is a key step in the metastatic spread of breast tumors. Although the presence of macrophages in primary tumors is associated with increased metastatic potential, the mechanistic basis for this observation is unknown. Using a chemotaxis-based in vivo invasion assay and multiphoton-based intravital imaging, we show that the interaction between macrophages and tumor cells facilitates the migration of carcinoma cells in the primary tumor. Gradients of either epidermal growth factor (EGF) or colony-stimulating factor 1 (CSF-1) stimulate collection into microneedles of tumor cells and macrophages even though tumor cells express only EGF receptor and macrophages express only CSF-1 receptor. Intravital imaging shows that macrophages and tumor cells migrate toward microneedles containing either EGF or CSF-1. Inhibition of either CSF-1- or EGF-stimulated signaling reduces the migration of both cell types. This work provides the first direct evidence for a synergistic interaction between macrophages and tumor cells during cell migration in vivo and indicates a mechanism for how macrophages may contribute to metastasis.

Role of infiltrated leucocytes in tumour growth and spread

Leucocytes are a major component of the tumour microenvironment. Recent studies have indicated that the infiltration and activity of these host cells are regulated by the tumour to promote its survival and progression. Through the production of an array of growth factors, proteases and angiogenic mediators, leucocytes in the tumour microenvironment promote tumour growth, angiogenesis and metastasis.

Macrophages: modulators of breast cancer progression

In many solid tumour types the abundance of tumour associated macrophages (TAMs) is correlated with poor prognosis. Macrophages are recruited through the local expression of chemoattractants such as colony stimulating factor 1 (CSF-1) and macrophage chemoattractant protein 1. Over-expression of both of these factors is correlated with poor prognosis in a variety of tumours. Macrophages also play an important physiological role in the development and function of many tissues ranging from the brain to the mammary gland. Thus we hypothesized that TAMs are recruited to tumours through the expression of potent chemoattractants and in this site their normal trophic functions are subverted to promote tumour progression and metastasis. To test this hypothesis we crossed mice deficient in macrophages owing to being homozygous for a null mutation in the CSF-1 gene with mice pre-disposed to mammary cancer due to the epithelial restricted expression of the polyoma middle T oncoprotein. The absence of macrophages did not change the incidence or growth of the primary tumour but decreased its rate of progression and inhibited metastasis. These data are explicable through the known macrophage functions in matrix remodelling, angiogenesis and stimulation of tumour growth and motility through the synthesis of growth and chemotactic factors. Interestingly, these functions are also normally found in wound healing or pathologically during chronic inflammation. This supports the notion that tumours are 'wounds that never heal' and suggests that chronic inflammation through persistent infection or by other means might be an important cofactor in the genesis and promotion of tumours. Macrophages might therefore be important targets for cancer therapies.

Positron emission tomography agent 2-deoxy-2-[18F]fluoro-D-glucose has a therapeutic potential in breast cancer

Background

Novel approaches are needed for breast cancer patients in whom standard therapy is not effective. 2-Deoxy-2-[¹⁸F]fluoro-D-glucose (¹⁸F-FDG) was evaluated as a potential radiomolecular therapy agent in breast cancer animal models and, retrospectively, in patients with metastatic breast cancer.

Methods

Polyoma middle T antigen (PyMT) and mouse mammary tumor virus-NeuT transgenic mice with tumors 0.5–1 cm in diameter were imaged with ¹⁸F-FDG, and tumor to liver ratios (TLRs) were calculated. The radiotoxicity of ¹⁸F-FDG administration was determined in healthy mice. PyMT mice with small (0.15–0.17 cm) and large (more than 1 cm) tumors were treated with 2–4 mCi of ¹⁸F-FDG, and control C3H/B6 mice with 3 mCi of ¹⁸F-FDG. At 10 days after treatment the tumors and control mammary glands were analyzed for the presence of apoptotic and necrotic cells. Five patients with breast cancer and metastatic disease were evaluated and standardized uptake values (SUVs) in tumors, maximum tolerated dose, and the doses to the tumor were calculated.

Results

Doses up to 5 mCi proved to be non-radiotoxic to normal organs. The ¹⁸F-FDG uptake in mouse tumors showed an average TLR of 1.6. The treatment of mice resulted in apoptotic cell death in the small tumors. Cell death through the necrotic pathway was seen in large tumors, and was accompanied by tumor fragmentation and infiltration with leukocytes. Normal mammary tissues were not damaged. A human ¹⁸F-FDG dose delivering 200 rad to the red marrow (less than 5% damage) was calculated to be 4.76 Ci for a 70 kg woman, and the dose to the tumors was calculated to be 220, 1100 and 2200 rad for SUVs of 1, 5 and 10, respectively.

Conclusion

We have shown that positrons delivered by ¹⁸F-FDG to mammary tumors have a tumoricidal effect on cancer cells. The study of breast cancer patients suggests that the tumor and normal organ dosimetry of ¹⁸F-FDG makes it suitable for therapy of this malignancy.

GFP expression in the mammary gland for imaging of mammary tumor cells in transgenic mice

To examine the behavior of tumor cells in tumors developing directly from mammary tissue in transgenic models, we have evaluated transgenic mice expressing green fluorescent protein (GFP). Using the mouse mammary virus promoter (MMTV) to directly drive expression of GFP, we find low levels of fluorescence in the mammary and salivary glands of transgenic animals. Using MMTV-Cre or WAP-Cre in combination with the Cre-activatable CAG-CAT-EGFP construct, we find stronger expression of GFP that is still tissue specific. These animals provide a range of expression of GFP that is suitable for analysis of transgenic mammary tumors and metastases in vivo at the single cell level of resolution.

The macrophage growth factor CSF-1 in mammary gland development and tumor progression

Colony stimulating factor 1 (CSF-1), a major regulator of the mononuclear phagocytic lineage, is expressed in more than 70% of human breast cancers and its expression is correlated with poor prognosis. Studies of CSF-1 null mutant mice demonstrated that CSF-1 plays an important role in normal mammary ductal development as well as in mammary tumor progression to metastasis. CSF-1 regulates these processes through the recruitment and regulation of macrophages, cells that become associated with mammary tumors and the terminal end buds at the end of the growing ducts. This phenomenon suggests that the tumors subvert normal developmental processes to allow invasion into the surrounding stroma, a process that gives the tumor access to the vasculature and consequently the promotion of metastasis. In addition, soluble CSF-1 secreted from the tumor acts to divert antitumor macrophage responses and suppresses the differentiation of mature tumor-antigen-presenting dendritic cell This review discusses these observations in detail and attempts to fit them into a larger picture of CSF-1 and macrophage action in the regulation of normal mammary gland development and tumor progression.

Requirement of macrophages and eosinophils and their cytokines/chemokines for mammary gland development

Epithelial/mesenchymal cell interactions are necessary for proper ductal morphogenesis throughout all stages of mammary gland development. Besides the well-established stromal components, such as adipocytes and fibroblasts, the mammary stroma is also infiltrated with migrating blood cells, mostly macrophages and eosinophils. The focus of this review is on the role of macrophages and their growth factor colony-stimulating factor 1 (CSF-1) in promoting branching morphogenesis during postnatal mammary gland development through to lactation. The more restricted role of eosinophils and their chemoattractant eotaxin during pubertal ductal morphogenesis is also discussed. A possible interaction between macrophages and eosinophils in ductal morphogenesis is considered, along with the roles of other chemokines. This role of macrophages in normal development also appears to be subverted by tumors of the mammary gland to promote the escape of the tumor cells from the local environment and enhance their rate of metastasis. These data emphasize the dual role of macrophages in the promotion of epithelial growth in normal and cancer states.

Total esophageal reconstruction using a tubed parascapular free flap

A method for total esophageal reconstruction when intestinal options are no longer available is presented. The technique described utilizes the parascapular microsurgical free flap, which is tubed and interposed between the cervical esophagus and the gastric remnant in the abdomen. The technique involves a well-recognized microsurgical flap and may be added to the armamentarium for total esophageal reconstruction.

Colony-stimulating factor 1 promotes progression of mammary tumors to malignancy

In human breast carcinomas, overexpression of the macrophage colony-stimulating factor (CSF-1) and its receptor (CSF-1R) correlates with poor prognosis. To establish if there is a causal relationship between CSF-1 and breast cancer progression, we crossed a transgenic mouse susceptible to mammary cancer with mice containing a recessive null mutation in the CSF-1 gene (Csf1(op)) and followed tumor progression in wild-type and null mutant mice. The absence of CSF-1 affects neither the incidence nor the growth of the primary tumors but delayed their development to invasive, metastatic carcinomas. Transgenic expression of CSF-1 in the mammary epithelium of both Csf1(op)/Csf1(op) and wild-type tumor-prone mice led to an acceleration to the late stages of carcinoma and to a significant increase in pulmonary metastasis. This was associated with an enhanced infiltration of macrophages into the primary tumor. These studies demonstrate that the growth of mammary tumors and the development to malignancy are separate processes and that CSF-1 selectively promotes the latter process. CSF-1 may promote metastatic potential by regulating the infiltration and function of tumor-associated macrophages as, at the tumor site, CSF-1R expression was restricted to macrophages. Our data suggest that agents directed at CSF-1/CSF-1R activity could have important therapeutic effects.

Angiogenesis and vascular growth factor receptor expression in malignant melanoma

The growth and metastases of many solid tumors are dependent on the recruitment of new blood vessels. Tumor angiogenesis is most likely initiated by paracrine release of growth factors that bind to their corresponding endothelial cell surface receptors. To determine whether angiogenesis and growth factor receptor expression are consistent findings in malignant melanoma, primary human melanomas were examined for mRNA expression of receptors for fibroblast growth factors (FGFR-1, FGFR-2), vascular endothelial growth factor (VEGFR-1, VEGFR-2), and the receptors Tiel and Tie2. Charts were reviewed and archival formalin-fixed, paraffin-embedded primary tumors were obtained from patients with thin (<1 mm; n = 10), intermediate (1 to 4 mm; n = 10), or thick malignant melanoma (>4 mm; n = 8). Also examined was whether melanoma cell lines could induce endothelial growth factor receptor synthesis by metabolic labeling. It was found that tumor vascularity did not correlate with clinical stage, melanoma thickness, or clinical outcome. It was also found that melanoma cell lines were not capable of directly regulating endothelial cell synthesis of growth factor receptors. However, expression of Tiel and VEGFR-2 mRNA by the tumor vasculature in select stage IA-IIB patients, and FGFR-1 mRNA expression by the tumor cells in the same clinical stages was found. The expression of these growth factor receptors did not correlate with clinical outcome. These data suggest that angiogenesis is not a prominent characteristic of primary malignant melanoma lesions and that the endothelial cell expression of Tiel and VEGFR-2 in vivo is probably not directly induced by the tumor.

Methemoglobinemia secondary to topical silver nitrate therapy--a case report

Methemoglobinemia is a rare complication in individuals exposed to nitrates or nitrites. Whereas methemoglobinemia is a recognized potential complication in burn patients treated with topical 0.5% silver nitrate solution, no report of methemoglobinemia in burn patients has been present in the literature for more than 15 years. We raise consciousness about this complication with a case report of a 12-month-old child with necrotizing fasciitis resulting from a cutaneous flank infection. The patient developed cyanosis 20 days after initiation of topical treatment with 0.5% silver nitrate solution. Intravenous injection of methylene blue can restore normal blood oxygenation.

Complexity in uterine macrophage responses to cytokines in mice

Uterine stromal macrophages change dramatically in density and morphology through the estrous cycle and during early pregnancy, whereas those in the mesometrial triangle do not undergo these changes. The mononuclear phagocytic growth factor, colony-stimulating factor-1 (CSF-1), regulates both the density and morphology of uterine macrophage populations, as shown by the fact that uterine macrophages are depleted and more rounded in the absence of CSF-1 caused by the osteopetrotic (csfm(op)) null mutation, compared to those of normal mice. Restoration of circulating CSF-1 to the nullizygous mice did not affect stromal macrophage density although it restored the population in the mesometrial triangle. This suggests CSF-1 regulation of these macrophage populations by local and humoral routes, respectively. Nevertheless, even in the absence of CSF-1, stromal macrophage population density varies 30-fold through the estrous cycle, suggesting the involvement in their regulation of factors other than CSF-1, such as the chemokines, which are chemoattractive for macrophages. The mRNA for the chemokines JE (MCP-1), C10, RANTES, and MIP1alpha are expressed in the uterus, with elevated levels observed on the first day of pregnancy. Such molecules, together with CSF-1, may play a role in modulating the complexities of uterine macrophage dynamics in response to sex steroid hormones and mating.

A1, a Bcl-2 family member, prolongs cell survival and permits myeloid differentiation

A1, a bcl-2 family member, has been identified as a hematopoietic-specific, early inducible gene. In this study it is shown that stable transfection of A1 into an interleukin-3 (IL-3)-dependent myeloid precursor cell line, 32D c13, leads to a retardation of IL-3 withdrawal-induced cell death similar to that observed with transfection of bcl-2. However, unlike bcl-2. A1 expression permits the accumulation of differentiated myeloid cells both before and after IL-3 withdrawal. Total cell accumulation, on the other hand, is considerably greater after IL-3 deprivation in the bcl-2 transfectant than in A1-expressing cells. Cells cotransfected with the two genes behave similarly to cells singly transfected with bcl-2, except that viability following IL-3 withdrawal is somewhat further enhanced. These results suggest that these two proteins have distinct roles that may be related to the divergent regulation of their expression during myeloid differentiation.

HIV infection and surgeons

The human immunodeficiency virus (HIV) causes acquired immunodeficiency syndrome, which remains uniformly fatal in affected individuals. A common route of HIV transmission is via inoculation of contaminated blood, which may occur during surgical procedures. Surgeons may estimate their risk of HIV infection over a 30-year surgical career based on HIV prevalence among surgical patients, percutaneous injury rate per operation, and seroconversion rate. Surgeons can reduce their risk by various means, but the most pragmatic is by reducing the rate of percutaneous injury through optimal surgical technique and proper precautions.

Selective induction of the beta chemokine C10 by IL-4 in mouse macrophages

The beta chemokines are a family of 8- to 12-kDa leukocyte chemoattractants that are typically produced by activated macrophages or lymphocytes. We examined the expression in primary macrophages of a recently described, and as yet functionally uncharacterized, murine beta chemokine, C10, and contrasted its regulation with that of several other beta chemokines. Although three other beta chemokines, macrophage inflammatory protein-1 alpha (MIP-1 alpha), JE, and RANTES, were all induced by LPS treatment of bone marrow-derived macrophages (BMM) and/or resident peritoneal macrophages (RPM), LPS stimulation of C10 was never observed. Conversely, IL-3 and granulocyte macrophage-CSF (GM-CSF) strongly induced C10 in both macrophage populations, whereas MIP-1 alpha and RANTES showed a weaker induction restricted to BMM. JE was strongly induced but only in BMM. Finally, IL-4 strongly induced C10 in a dose-dependent manner in both BMM and RPM but failed to stimulate any of the other three beta chemokines. The accumulation of C10 protein in culture supernatants paralleled the induction of mRNA, and the combination of IL-4 and GM-CSF led to enhanced protein levels. The expression of the C10 message in response to cytokines was completely blocked by cycloheximide, whereas the other three chemokines were all overexpressed in the presence of this inhibitor. These results demonstrate a sharp divergence between the regulation of C10 expression and that of other chemokines and suggest that this molecule may have distinct functions in host defense.

Selective induction of the beta chemokine C10 by IL-4 in mouse macrophages

The beta chemokines are a family of 8- to 12-kDa leukocyte chemoattractants that are typically produced by activated macrophages or lymphocytes. We examined the expression in primary macrophages of a recently described, and as yet functionally uncharacterized, murine beta chemokine, C10, and contrasted its regulation with that of several other beta chemokines. Although three other beta chemokines, macrophage inflammatory protein-1 alpha (MIP-1 alpha), JE, and RANTES, were all induced by LPS treatment of bone marrow-derived macrophages (BMM) and/or resident peritoneal macrophages (RPM), LPS stimulation of C10 was never observed. Conversely, IL-3 and granulocyte macrophage-CSF (GM-CSF) strongly induced C10 in both macrophage populations, whereas MIP-1 alpha and RANTES showed a weaker induction restricted to BMM. JE was strongly induced but only in BMM. Finally, IL-4 strongly induced C10 in a dose-dependent manner in both BMM and RPM but failed to stimulate any of the other three beta chemokines. The accumulation of C10 protein in culture supernatants paralleled the induction of mRNA, and the combination of IL-4 and GM-CSF led to enhanced protein levels. The expression of the C10 message in response to cytokines was completely blocked by cycloheximide, whereas the other three chemokines were all overexpressed in the presence of this inhibitor. These results demonstrate a sharp divergence between the regulation of C10 expression and that of other chemokines and suggest that this molecule may have distinct functions in host defense.

Increased expression of Fc gamma RI on isolated PMN from individuals of African descent

Fc gamma R plays an important role in host defense, triggering and/or facilitating many immunologic responses. Of the three defined Fc gamma Rs, Fc gamma RI (CD64) is not known to be constitutively expressed on normal PMN. We report here that there is markedly increased expression of Fc gamma RI on the PMN of normal, healthy blacks, detected by binding of monoclonal antibody to this receptor. This may have significant implications when multiracial data are pooled in studies of receptor expression as markers of response to various chemotherapeutic agents.

Characterization of A1, a novel hemopoietic-specific early-response gene with sequence similarity to bcl-2

Granulocyte-macrophage colony-stimulating factor (GM-CSF) stimulates hemopoietic cell proliferation, differentiation, and functional activation by inducing the expression of specific genes. As part of an investigation of the regulation of gene expression by GM-CSF, we have previously identified a novel murine GM-CSF-inducible gene, A1. In this report, we present the complete nucleotide sequence of the A1 mRNA as well as a portion of the 5' flanking region, and describe the expression pattern of the gene. The results demonstrate that A1 is a hemopoietic tissue-specific gene that is expressed in several hemopoietic cell lineages, including T-helper lymphocytes, macrophages, and neutrophils. In murine bone marrow-derived macrophages, A1 gene expression is rapidly and transiently induced by GM-CSF, and the induction was independent of de novo protein synthesis. In addition to GM-CSF, a transient induction of A1 mRNA accumulation was observed in response to LPS in macrophages. This induction is not mediated by IL-1 alpha or IL-6, neither of which stimulate A1. In the myeloid precursor cell line, 32D cl3, A1 gene expression is stably induced during granulocyte colony-stimulating factor-stimulated myeloid cell differentiation. The A1 message encodes a predicted polypeptide with an M(r) of 20,024 and no signal peptide. The peptide sequence contains a region of 80 amino acids that shows similarity to bcl-2 and to the recently described bcl-2-related gene, MCL1. These data demonstrate that A1 is a novel early-response gene whose expression is associated with a variety of stimuli and occurs in several hemopoietic cell types.

Characterization of A1, a novel hemopoietic-specific early-response gene with sequence similarity to bcl-2

Granulocyte-macrophage colony-stimulating factor (GM-CSF) stimulates hemopoietic cell proliferation, differentiation, and functional activation by inducing the expression of specific genes. As part of an investigation of the regulation of gene expression by GM-CSF, we have previously identified a novel murine GM-CSF-inducible gene, A1. In this report, we present the complete nucleotide sequence of the A1 mRNA as well as a portion of the 5' flanking region, and describe the expression pattern of the gene. The results demonstrate that A1 is a hemopoietic tissue-specific gene that is expressed in several hemopoietic cell lineages, including T-helper lymphocytes, macrophages, and neutrophils. In murine bone marrow-derived macrophages, A1 gene expression is rapidly and transiently induced by GM-CSF, and the induction was independent of de novo protein synthesis. In addition to GM-CSF, a transient induction of A1 mRNA accumulation was observed in response to LPS in macrophages. This induction is not mediated by IL-1 alpha or IL-6, neither of which stimulate A1. In the myeloid precursor cell line, 32D cl3, A1 gene expression is stably induced during granulocyte colony-stimulating factor-stimulated myeloid cell differentiation. The A1 message encodes a predicted polypeptide with an M(r) of 20,024 and no signal peptide. The peptide sequence contains a region of 80 amino acids that shows similarity to bcl-2 and to the recently described bcl-2-related gene, MCL1. These data demonstrate that A1 is a novel early-response gene whose expression is associated with a variety of stimuli and occurs in several hemopoietic cell types.

The effects of IL-1, IL-2, and tumor necrosis factor on polymorphonuclear leukocyte Fc gamma receptor-mediated phagocytosis. IL-2 down-regulates the effect of tumor necrosis factor

It has been reported that the Fc gamma R-mediated phagocytic activity of polymorphonuclear leukocytes (PMN) from patients with acute bacterial infections is markedly enhanced when compared with healthy controls. Inasmuch as several potent cytokines are known to be involved in inflammatory and infectious processes, we studied the effects of three such cytokines (IL-1 beta, IL-2, and TNF-alpha) on normal PMN Fc gamma R-mediated phagocytosis. IL-1 beta and TNF alpha both caused a significant increase in the ingestion of EIgG by adherent PMN. In combination, IL-1 beta and TNF-alpha had an additive effect, even when each was used at its optimal concentration. In contrast to the enhancing effects mediated by IL-1 beta and TNF-alpha, IL-2 alone had no significant effect on PMN phagocytosis. Notably, however, IL-2 at a concentration of 10(4) U/ml partially inhibited TNF-alpha-mediated enhancement of phagocytosis by decreasing TNF binding to the PMN cell surface. This inhibitory effect of IL-2 on TNF was reversed by anti-IL-2 antibody and mAb directed against the low affinity IL-2R (anti-Tac), whereas mAb directed against the intermediate affinity receptor (mik-beta 1) had no such effect. These findings may have important physiologic implications, because patients receiving IL-2 therapy have been shown to have increased susceptibility to infection.

The effects of IL-1, IL-2, and tumor necrosis factor on polymorphonuclear leukocyte Fc gamma receptor-mediated phagocytosis. IL-2 down-regulates the effect of tumor necrosis factor

It has been reported that the Fc gamma R-mediated phagocytic activity of polymorphonuclear leukocytes (PMN) from patients with acute bacterial infections is markedly enhanced when compared with healthy controls. Inasmuch as several potent cytokines are known to be involved in inflammatory and infectious processes, we studied the effects of three such cytokines (IL-1 beta, IL-2, and TNF-alpha) on normal PMN Fc gamma R-mediated phagocytosis. IL-1 beta and TNF alpha both caused a significant increase in the ingestion of EIgG by adherent PMN. In combination, IL-1 beta and TNF-alpha had an additive effect, even when each was used at its optimal concentration. In contrast to the enhancing effects mediated by IL-1 beta and TNF-alpha, IL-2 alone had no significant effect on PMN phagocytosis. Notably, however, IL-2 at a concentration of 10(4) U/ml partially inhibited TNF-alpha-mediated enhancement of phagocytosis by decreasing TNF binding to the PMN cell surface. This inhibitory effect of IL-2 on TNF was reversed by anti-IL-2 antibody and mAb directed against the low affinity IL-2R (anti-Tac), whereas mAb directed against the intermediate affinity receptor (mik-beta 1) had no such effect. These findings may have important physiologic implications, because patients receiving IL-2 therapy have been shown to have increased susceptibility to infection.

Effects of ethanol on CRF release in vitro

Acute ethanol exposure produces activation of the brain-pituitary-adrenal (BPA) axis, resulting in the release of ACTH, beta-endorphin, and glucocorticoids. While elevated levels of plasma glucocorticoids are also found after chronic ethanol administration, plasma ACTH and beta-endorphin are normal or reduced. It is also unclear whether chronic ethanol exposure results in tolerance to the stimulatory effect of ethanol on BPA activity. To determine the site and mechanism of ethanol action on the BPA axis we studied the CRF secretory profile in a superfused rat hypothalamic preparation after chronic ethanol administration in vivo and the CRF responses after acute ethanol exposure in vitro. Superfused hypothalami from normal and pair-fed control rats released CRF-like immunoreactive material (CRF-LI) in a pulsatile manner, with a mean (+/- SE) frequency of 5.1 +/- 0.7 pulses/h. In contrast, the pulse frequency of CRF-LI release from hypothalami of rats receiving chronic ethanol treatment (fed an alcohol-containing liquid diet for 2 weeks) increased dramatically; the basal mean CRF level, pulse amplitude, and pulse duration remained unchanged. Hypothalamic CRF content was decreased. This chronic ethanol exposure also altered the dose-response characteristics of CRF release when ethanol was introduced acutely, as a pulse, into the in vitro preparation. Acute exposure to 20 mg/100 ml ethanol produced greater release of CRF-LI from control hypothalami than from chronic ethanol-exposed hypothalami. A further elevation above basal levels was produced by 200 mg/100 ml ethanol in control, but not ethanol-exposed, hypothalami. Secretion of CRF from ethanol-exposed hypothalami in response to depolarizing concentrations of potassium chloride was suppressed. Chronic ethanol treatment had no effect on CRF-LI and CRF bioactivity responses to stimulation with acetylcholine. These findings suggest the presence of a high frequency pulse-generating mechanism for CRF release in the hypothalamus. This pulsatile secretory mechanism is altered by chronic ethanol exposure of the animals in vivo. Chronic intoxication resulted in tolerance to the stimulatory effect of ethanol on CRF release in vitro.