Loss of Cul1 results in early embryonic lethality and dysregulation of cyclin E.

The sequential timing of cell-cycle transitions is primarily governed by the availability and activity of key cell-cycle proteins. Recent studies in yeast have identified a class of ubiquitin ligases (E3 enzymes) called SCF complexes, which regulate the abundance of proteins that promote and inhibit cell-cycle progression at the G1-S phase transition. SCF complexes consist of three invariable components, Skp1, Cul-1 (Cdc53 in yeast) and Rbx1, and a variable F-box protein that recruits a specific cellular protein to the ubquitin pathway for degradation. To study the role of Cul-1 in mammalian development and cell-cycle regulation, we generated mice deficient for Cul1 and analysed null embryos and heterozygous cell lines. We show that Cul1 is required for early mouse development and that Cul1 mutants fail to regulate the abundance of the G1 cyclin, cyclin E (encoded by Ccne), during embryogenesis.

Real-time calculation of a limiting form of the Renyi entropy applied to detection of subtle changes in scattering architecture.

Previously a new method for ultrasound signal characterization using entropy H(f) was reported, and it was demonstrated that in certain settings, further improvements in signal characterization could be obtained by generalizing to Renyi entropy-based signal characterization I(f)(r) with values of r near 2 (specifically r=1.99) [M. S. Hughes et al., J. Acoust. Soc. Am. 125, 3141-3145 (2009)]. It was speculated that further improvements in sensitivity might be realized at the limit r-->2. At that time, such investigation was not feasible due to excessive computational time required to calculate I(f)(r) near this limit. In this paper, an asymptotic expression for the limiting behavior of I(f)(r) as r-->2 is derived and used to present results analogous to those obtained with I(f)(1.99). Moreover, the limiting form I(f,infinity) is computable directly from the experimentally measured waveform f(t) by an algorithm that is suitable for real-time calculation and implementation.

Application of Renyi entropy for ultrasonic molecular imaging.

Previous work has demonstrated that a signal receiver based on a limiting form of the Shannon entropy is, in certain settings, more sensitive to subtle changes in scattering architecture than conventional energy-based signal receivers [M. S. Hughes et al., J. Acoust. Soc. Am. 121, 3542-3557 (2007)]. In this paper new results are presented demonstrating further improvements in sensitivity using a signal receiver based on the Renyi entropy.

Properties of an entropy-based signal receiver with an application to ultrasonic molecular imaging.

Qualitative and quantitative properties of the finite part, H(f), of the Shannon entropy of a continuous waveform f(t) in the continuum limit are derived in order to illuminate its use for waveform characterization. Simple upper and lower bounds on H(f), based on features of f(t), are defined. Quantitative criteria for a priori estimation of the average-case variation of H(f) and log E(f), where E(f) is the signal energy of f(t) are also derived. These provide relative sensitivity estimates that could be used to prospectively choose optimal imaging strategies in real-time ultrasonic imaging machines, where system bandwidth is often pushed to its limits. To demonstrate the utility of these sensitivity relations for this application, a study designed to assess the feasibility of identification of angiogenic neovasculature targeted with perfluorocarbon nanoparticles that specifically bind to alpha(v)beta3-integrin expression in tumors was performed. The outcome of this study agrees with the prospective sensitivity estimates that were used for the two receivers. Moreover, these data demonstrate the ability of entropy-based signal receivers when used in conjunction with targeted nanoparticles to elucidate the presence of alpha(v)beta3 integrins in primordial neovasculature, particularly in acoustically unfavorable environments.

Basal amino acid concentrations and the response to incremental glucose infusion in tumor bearing rats.

Plasma amino acid concentrations were measured in fasting nontumor bearing (NTB) and tumor bearing (TB; methylcholanthrene induced sarcoma) male Fischer F344 rats during infusion of 0.9% NaCl solution or glucose at 3.72 or 13.05 mumol/100 g total body weight (TBW)/min. The animals were studied when the tumor comprised only 8% of the TBW at a time when decreased food intake and weight loss were not manifest. During 0.9% NaCl infusion there were no significant differences between NTB or TB animals in the concentration of alanine (NTB: 152.6 +/- 20.1; TB: 150.3 +/- 19.0 microM; mean +/- SD), branched chain amino acids (BCAA) (NTB: 343.3 +/- 48.7; TB: 344.2 +/- 20.5 microM), essential amino acids, aromatic amino acids, or total amino acids. During infusion of glucose at 3.72 mumol/100 g TBW/min the alanine levels rose (NTB: 283.6 +/- 33.4; TB: 286.7 +/- 43.3 microM), and the BCAA levels fell (NTB: 215.9 +/- 19.4; TB: 228.7 +/- 43.4 microM) to similar concentrations in both NTB and TB animals. Glucose infusion at 13.05 mumol/100 g TBW/min resulted in an additional increase in the alanine concentration (NTB: 344.5 +/- 28.7; TB: 382.8 +/- 116.6 microM), and a further decrease in the BCAA concentration (NTB: 166.4 +/- 30.8; TB: 160.7 +/- 30.5 microM) without significant differences between NTB and TB animals. Paired analysis for each animal prior to and during glucose infusion demonstrated a similar absolute micromolar change in alanine and BCAA concentration during both glucose infusion rates in both NTB and TB animals. The levels of aromatic amino acids and total amino acids were unchanged and the essential amino acid concentrations were decreased only at the higher glucose infusion rate in both NTB and TB groups. Basal amino acid metabolism appears similar in the NTB and TB animals, prior to the onset of anorexia and weight loss. During exogenous glucose infusion the reciprocal changes in the plasma alanine and BCAA concentrations support the concept of a glucose-alanine-BCAA cycle at the whole body level that appears to respond to a similar extent in NTB and TB animals.

Cross-species comparison of angiogenesis during the premalignant stages of squamous carcinogenesis in the human cervix and K14-HPV16 transgenic mice.

Infection of the human cervix with certain papillomavirus subtypes is associated with the development of neoplastic squamous lesions that can progress to overt cervical malignancies. Recently, multistage squamous carcinogenesis has been achieved in K14-HPV16 transgenic mice, wherein expression of the human papillomavirus (HPV) type 16 early genes is targeted to basal squamous epithelial cells by regulatory elements of the human keratin-14 (K14) promoter. Immunostaining of the endothelial marker vWf revealed a parallel upregulation of angiogenesis during the early neoplastic stages in both human cervix and the epidermis of K14-HPV16 transgenic mice. Moreover, high-grade premalignant lesions and cancers in humans and transgenic mice were characterized by an additional increment in the number of new capillaries and close apposition of the microvasculature to the overlying neoplastic epithelium. Expression of the potent angiogenic factor VEGF was progressively up-regulated during carcinogenesis in both species, correlating with the increased density and altered distribution of the microvasculature. Thus, angiogenesis occurs during the premalignant stages of squamous carcinogenesis in both human cervical disease and a relevant transgenic model and may be controlled by similar molecular mechanisms in both species. These results validate the use of the transgenic model to elucidate the role of angiogenesis during HPV-associated neoplastic progression.

Sensitivity of the cervical transformation zone to estrogen-induced squamous carcinogenesis.

Regions where one type of epithelium replaces another (metaplasia) have a predilection for cancer formation. Environmental factors are closely linked to metaplastic carcinogenesis. In particular, cervical cancers associated with human papillomavirus (HPV) infection develop primarily at the transformation zone, a region where metaplastic squamous cells are detected in otherwise columnar epithelial-lined endocervical glands. Previously, we reported estrogen-induced multistage vaginal and cervical carcinogenesis in transgenic mice expressing HPV16 oncogenes in basal squamous epithelial cells. In the present study to investigate the threshold neoplastic response to exogenous estrogen, we treated groups of transgenic mice with lower hormone doses. A 5-fold reduction in estrogen dose induced squamous carcinogenesis solely at the cervical transformation zone compared with other reproductive tract sites. Further study delineated stages of transformation zone carcinogenesis, including formation of hyperplastic lower uterine glands and emergence of multiple foci of squamous metaplasia from individual stem-like glandular reserve cells, followed by neoplastic progression of metaplasia to dysplasia and squamous cancer. We propose that a combination of low-dose estrogen and low-level HPV oncogene expression biases transformation zone glandular reserve cells toward squamous rather than columnar epithelial fate decisions. Synergistic activation of proliferation by viral oncoprotein cell cycle dysregulation and estrogen receptor signaling, together with altered paracrine stromal-epithelial interactions, may conspire to support and promote neoplastic progression and cancer formation.

Glucose metabolism and the percentage of glucose derived from alanine: response to exogenous glucose infusion in tumor-bearing and non-tumor-bearing rats.

Glucose and alanine metabolism were investigated in non-tumor-bearing (NTB) and tumor-bearing (TB) male F344 rats after a 24-hr fast and during the infusion of either 0.9% NaCl solution or glucose at 0.67 or 2.35 mg per 100 g total body weight per min. During 0.9% NaCl solution infusion, the plasma glucose level was higher (98.2 +/- 4.0 versus 85.8 +/- 8.1 mg per di; p less than 0.05), the whole-blood lactate level was lower (5.8 +/- 0.8 versus 8.3 +/- 1.6 mg per di; p less than 0.05), the glucose turnover rate was lower (0.72 +/- 0.04 versus 0.88 +/- 0.13 mg per 100 g total body weight per min; p less than 0.05), alanine turnover rate and the percentage of glucose derived from alanine was measured by [14C]alanine in the NTB and compared to the TB animals. In response to glucose infusions, the whole-blood lactate level rose in both groups but remained lower (7.1 +/- 0.9 versus 10.5 +/- 2.4 mg per dl at 0.67 mg per 100 g total body weight per min, p less than 0.05; 9.1 +/- 1.1 versus 19.3 +/- 5.5 mg per dl at 2.35 mg per 100 g total body weight per min, p less than 0.05; NTB versus TB) in the NTB than in the TB animals. The endogenous production rate of glucose as measured by [3H]glucose displayed a similar response to exogenous substrate in the NTB and TB animals but required a higher plasma glucose concentration to effect a similar degree of suppression in the TB group. The alanine turnover rate rose to a similar level, and the percentage of glucose derived from alanine was similarly depressed in the NTB and TB animals at each glucose infusion rate.

Selective depletion of tumor ATP by 2-deoxyglucose and insulin, detected by 31P magnetic resonance spectroscopy.

The purpose of this study was to investigate whether substrate deprivation acutely and selectively decreases ATP concentration in an experimental sarcoma. Two methods of substrate deprivation were examined: glycolysis was inhibited using 2-deoxyglucose (2DG), and plasma substrate levels were reduced using insulin. The effects of treatment on tumor ATP, inorganic phosphate, and pH were studied by 31P nuclear magnetic resonance spectroscopy. 2DG (2 g/kg) was administered i.p. to rats bearing s.c. methylcholanthrene-induced sarcomas. Inhibition of glycolysis by 2DG caused a 52 +/- 13% (SE) decrease in the tumor ATP to inorganic phosphate ratio, associated with a decrease in pH of 0.38 +/- 0.10 unit. The same dose of 2DG caused no significant change in the ratio of phosphocreatine to ATP in brain. Insulin (125 units/kg, i.p.) caused a 68% decline in plasma glucose and a 71% decline in betahydroxybutyrate compared to saline-treated animals. Concomitantly, 31P nuclear magnetic resonance spectroscopy detected a 48 +/- 13% decrease in sarcoma ATP, with a reciprocal elevation of inorganic phosphate in insulin-treated animals. In contrast, the brain phosphocratine/ATP ratio was unaffected by insulin. These results suggest that large tumors are acutely sensitive to inhibition of glycolysis and reductions in plasma levels of substrates for oxidative phosphorylation and glycolysis, while the brain is unaffected. In addition, this work provides support for the use of 31P nuclear magnetic resonance spectroscopy to monitor tumor response to therapy.

Hypoxia-inducible factor-1alpha is a positive factor in solid tumor growth.

Deficiencies in oxygenation are widespread in solid tumors. The transcription factor hypoxia-inducible factor (HIF)-1alpha is an important mediator of the hypoxic response of tumor cells and controls the up-regulation of a number of factors important for solid tumor expansion, including the angiogenic factor vascular endothelial growth factor (VEGF). We have isolated two cell lines nullizygous for HIF-1alpha, one from embryos genetically null for HIF-1alpha, and the other from embryos carrying loxP-flanked alleles of the gene, which allows for cre-mediated excision. The loss of HIF-1alpha negatively affects tumor growth in these two sets of H-ras-transformed cell lines, and this negative effect is not due to deficient vascularization. Despite differences in VEGF expression, vascular density is similar in wild-type and HIF-1alpha-null tumors. The evidence from these experiments indicates that hypoxic response via HIF-1alpha is an important positive factor in solid tumor growth and that HIF-1alpha affects tumor expansion in ways unrelated to its regulation of VEGF expression.

Coordinate up-regulation of hypoxia inducible factor (HIF)-1alpha and HIF-1 target genes during multi-stage epidermal carcinogenesis and wound healing.

Both carcinogenesis and wound healing proceed through stages of proliferation and tissue remodeling. Here, using either a model of multistage epidermal carcinogenesis in K14-HPV16 transgenic mice or creation of full-thickness back wounds in nontransgenic mice, we determined patterns of expression of hypoxia inducible factor (HIF)-1alpha, and three targets of the heterodimeric transcription factor HIF-1, glucose transporter (GLUT)-1, phosphoglycerate kinase (PGK)-1, and vascular endothelial growth factor (VEGF) in skin. Neither HIF-1alpha, GLUT-1, PGK-1, nor VEGF mRNA was detectable in unwounded nontransgenic skin. In epidermal carcinogenesis, HIF-1alpha, GLUT-1, PGK-1, and VEGF mRNAs were just detectable in early-stage hyperplasia, markedly increased in high-grade epidermal chest dysplasias, and further increased in invasive squamous carcinomas. In neoplastic skin, HIF-1alpha, GLUT-1, and PGK-1 mRNAs localized in the basal and immediate suprabasal epidermal layers, whereas VEGF mRNA was predominantly expressed in the more superior spinous and granular epidermal layers. Immediately after wounding, HIF-1alpha, GLUT-1, and PGK-1 mRNAs were detectable in basal keratinocytes at the wound edge. Expression of all three genes increased to maximum levels in reepithelializing basal keratinocytes and then diminished to near undetectable levels after wound epithelialization. Although VEGF mRNA similarly increased and decreased during wound healing, its expression pattern was more punctate; the most intense hybridization signals were detected in the upper spinous and granular layers of reepithelializing keratinocytes and in dermal cells morphologically similar to macrophages. These data suggest stage-specific and spatio-temporal control of HIF-1alpha and HIF-1 target gene expression in both multistage epithelial carcinogenesis and wound healing.

Difluoromethylornithine chemoprevention of epidermal carcinogenesis in K14-HPV16 transgenic mice.

To be informative for chemoprevention, animal models must both closely emulate human disease and possess surrogate endpoint biomarkers that facilitate rapid drug screening. This study elucidated site-specific histopathological and biochemical surrogate endpoint biomarkers of spontaneous epidermal carcinogenesis in K14-HPV16 transgenic mice and demonstrated that the incidence and severity of these markers were decreased by the ornithine decarboxylase (ODC) inhibitor difluoromethylornithine (DFMO). The cumulative incidence of visible epidermal cancers in 127 untreated transgenic mice was 42% by 52 weeks of age, most frequently affecting the chest as flat lesions in association with chronic ulcers, or in the ear as protuberant masses. Microscopic malignancies were detected in 39% of 32-week-old transgenic mice and were found to emerge from precursor lesions that were of two distinct types: dysplastic sessile ear papillomas and hyperproliferative follicular/interfollicular chest dysplasias. ODC activity and tissue polyamine contents were differentially elevated in ear and chest skin during carcinogenesis, such that there was a marked elevation of both parameters of polyamine metabolism as early as 4 weeks of age in the ear, whereas in the chest, polyamine metabolism was increased significantly only in the late stages of neoplastic progression and in epidermal cancers. Administration of 1.0% DFMO in the drinking water from 4 to 32 weeks of age prevented both visible and microscopic malignancies and significantly decreased the incidence of chest and ear precursor lesions. ODC activity and tissue putrescine content were markedly diminished by DFMO chemoprevention in ear skin, whereas there was a more modest decline of these parameters in chest skin. DFMO treatment of transgenic mice from 28 to 32 weeks of age was associated with an absence of ear cancer and a marked regression of dysplastic papillomas. In contrast, the results in chest skin were complex in that the severity of chest precursors diminished, but their incidence was unchanged, and microscopic cancers were still detectable within these lesions. Collectively, this study highlights the utility of multistage epidermal carcinogenesis in K14-HPV16 transgenic mice both for the study of the biology of, and as a screening tool for, novel drugs and chemopreventive regimens.

Indole-3-carbinol prevents cervical cancer in human papilloma virus type 16 (HPV16) transgenic mice.

Mice that express transgenes for human papillomavirus type 16 under a keratin 14 promoter (K14-HPV16 mice) develop cervical cancer when they are given 17beta-estradiol chronically. We asked whether the antiestrogenic phytochemical indole-3-carbinol (I3C), found in cruciferous vegetables, administered at physiological doses, would prevent the cervical-vaginal cancer that is promoted in these mice by high doses of estrogen. We compared mice that were fed a control diet with those that were fed a diet supplemented with 2000 ppm I3C. In the group fed the control diet, at a dose of estradiol of 0.125 mg per 60-day release, 19 of 25 transgenic mice developed cervical-vaginal cancer within 6 months, and the remainder had dysplasia. Only 2 mice of 24 in the group fed the I3C supplemented diet developed cancer, and the remainder had dysplasia or hyperplasia. I3C reduced dysplasia in the nontransgenic mice. Similar results were obtained at a higher dose of estradiol (0.250 mg per 60-day release), and I3C helped to prevent morbidity associated with retention of fluid in the bladder that frequently occurred with the higher estradiol dose. Additionally, I3C appeared to reduce skin cancer in transgenic mice. These data indicate that I3C is a useful preventive for cervical-vaginal cancer and, possibly, other cancers with a papillomavirus component.

Upregulation of fibroblast growth factors and their receptors during multi-stage epidermal carcinogenesis in K14-HPV16 transgenic mice.

Upregulation of acidic and basic fibroblast growth factors (FGF-1 and -2), and their cognate receptors FGFR-1 and -2, has been demonstrated in a variety of epithelial malignancies. However, the patterns of FGF/FGFR expression at specific stages of epithelial carcinogenesis have not been extensively characterized. In this report, the levels of FGF-1, FGF-2, FGF-7 mRNA and their receptors FGFR-1 and FGFR-2, were investigated during epidermal carcinogenesis in transgenic mice expressing the early region of the 'high risk' papillomavirus type 16 (HPV16) under control of the human keratin-14 enhancer/promoter (K14-HPV16 transgenic mice). FGF-1 was first upregulated in dysplasias, while FGF-2 was constitutively expressed in non-transgenic, neoplastic, and malignant keratinocytes throughout carcinogenesis. Expression of FGF-7 was undetectable in non-transgenic epidermis, and remained at threshold levels at all stages of progression. In well differentiated squamous cancers, FGFR-1 was upregulated and co-localized with angiogenic capillaries in the dermis underlying dysplastic lesions and within papillary fronds of invasive cancers. In contrast, FGFR-1 was upregulated specifically within the malignant squamous cells of moderate-poorly differentiated squamous cancers. The expression of FGFR-2 was essentially constitutive in both non-transgenic and neoplastic epidermis. Collectively the data suggest that the FGF/FGFR signaling pathways may potentially contribute to several facets of multi-stage epithelial carcinogenesis, including auto- or paracrine growth stimulation, upregulation of angiogenesis, and stromal remodeling.

Regulation of Myc and Mad during epidermal differentiation and HPV-associated tumorigenesis.

c-Myc and Mad each form heterodimers with Max that bind the same E-box related DNA sequences. Whereas Myc:Max complexes activate transcription and promote cell proliferation and transformation, Mad:Max complexes repress transcription and block c-Myc-mediated cell transformation. Here we examine these antagonistic transcription factors during epithelial differentiation and neoplastic progression. During differentiation of primary human keratinocytes, Mad is rapidly induced and c-Myc is downregulated, resulting in a switch from c-Myc:Max to Mad:Max heterodimers. In normal epidermis and colonic mucosa c-myc expression is restricted to proliferating cell layers, while mad expression is restricted to differentiating cell layers. Using HPV18 transformed keratinocytes that vary in their ability to differentiate in organotypic cultures, we find that Mad induction occurs only in those cells that retain a differentiation response. In the epidermis of transgenic mice in which expression of the HPV16 E6 and E7 oncogenes are targeted to basal keratinocytes, neoplastic progression occurs and is marked by an expansion of c-myc expressing basal-like cells. Expression of mad is found only in growth-arrested differentiating cells on the outer edges of preneoplastic lesions. The squamous cell carcinomas that arise evidence a variable number of sites within the tumor masses where mad expression and morphological differentiation coincide; increasing malignancy correlates with loss of both mad and capability to differentiate. These results indicate that c-Myc and Mad expression are tightly coupled to the transition from proliferation to differentiation of epithelial cells and that restriction of Mad expression may be associated with loss of normal differentiation capability and with tumorigenesis.

Wound complications in the multimodality treatment of extremity and superficial truncal sarcomas.

The incidence and severity of wound complications were examined in 105 patients with extremity and superficial truncal sarcomas who were eligible for wide local excision with or without adjuvant perioperative brachytherapy (BRT) and/or chemotherapy. Fifty-four cases from the eligible group were entered into a randomized prospective trial of the efficacy of BRT in decreasing local recurrence. In the eligible patients, major wound complications occurred in nine of 41 (22%) of the BRT cases, compared with two of 64 (3%) of the non-BRT patients, which was a significant increase (P = .002). The combined frequency of major and moderate wound complications was also significantly increased in the BRT (18 of 41, 44%) compared with the non-BRT (nine of 64, 14%) patients (P = .0006). The median duration to complete resolution of these complications was 189 days (14 to 597) in the BRT, compared with 49 (11 to 170) days in the non-BRT group (P = .0005); however, no amputations were required, and only 14% of the BRT-associated wound complications were of prolonged duration, ie, greater than 200 days. In the randomized study, both the total number of complications, and the combination of major and moderate complications were increased significantly in the BRT v the non-BRT patients. Adjuvant Adriamycin (Adria Laboratories, Columbus, OH) administered in 60 mg/m2 increments to a cumulative dose of 540 mg/m2 did not appear to impair wound healing even when administered within 15 days of operation. Significant wound complications occur in major resections of extremity and superficial truncal sarcomas. If the addition of adjuvant BRT produces a decrease in local recurrence, then either patient selection will have to be more rigidly applied, especially in wounds where skin flap blood supply is tenuous, or the technique will need to be modified to balance the short-term aim of reducing wound complications with the long-term goal of local tumor control.

Modulation of the human homeobox genes PRX-2 and HOXB13 in scarless fetal wounds.

Scarless healing of cutaneous wounds occurs in humans during the first two trimesters of development, but by birth all wounds are repaired with scar formation. To search for transcriptional regulatory genes that might mediate fetal tissue regeneration, we surveyed homeobox gene expression in proliferating fetal fibroblasts and in wounded and unwounded skin. Two novel human homeobox genes, PRX-2 and HOXB13, were identified that were differentially expressed during fetal versus adult wound healing. Both genes were predominantly expressed in proliferating fetal fibroblasts and developing dermis, and PRX-2 was downregulated in adult skin. In a model of scarless fetal skin regeneration, PRX-2 expression was strongly increased compared with unwounded skin and the signal was localized to the wounded dermis, the site of scarless repair. Conversely, in adult skin weak epidermal PRX-2 expression was observed, mRNA levels were not increased by wounding, and no dermal expression was detected. HOXB13 expression was decreased in wounded fetal tissue relative to unwounded fetal controls or wounded adult skin. Thus both HOXB13 and PRX-2 are expressed in patterns consistent with roles in fetal skin development and cutaneous regeneration.

Expression of interferon-beta is associated with growth arrest of murine and human epidermal cells.

The cytokine interferon-beta is a regulator of cell replication and function, including invasion and induction of angiogenesis. The goal of this study was to determine whether the expression of interferon-beta by cells in the epidermis correlated with terminal differentiation. In situ hybridization analysis and immunohistochemical staining of formalin-fixed, paraffin-embedded specimens of normal human and murine epidermis and human and murine skin tumors of epithelial origin revealed that only differentiated, nondividing cells of the epidermis expressed interferon-beta protein. Keratinocyte cultures established from the epidermis of 3 d old mice were maintained under conditions permitting continuous cell division or induction of differentiation. Continuously dividing cells did not produce interferon-beta whereas nondividing differentiated cells expressing keratin 1 did. Growth-arrested, undifferentiated keratinocytes also expressed interferon-beta protein. Neutralizing interferon-beta in the culture medium inhibited differentiation, but the addition of exogenous interferon-beta did not stimulate differentiation. These data indicate that interferon-beta is produced by growth-arrested, terminally differentiated keratinocytes.

Mucoepidermoid tumor of trachea.

Mucoepidermoid carcinoma of the trachea is rare. Its occurence in a 14-year-old boy is reported here. This case illustrates the typical course of tracheal tumors with clinical manifestations of cough, wheezing, and hemoptysis, the intially reported normal chest roentgenogram, and the common failure to diagnose tracheal tumor for several months. Early use of tomographic studies and bronchoscopic examination in any person with recent onset of airway obstruction unresponsive to bronchodilator therapy is recommended.

Inhibition of tumor high-energy phosphate metabolism by insulin combined with rhodamine 123.

The purpose of this study was to determine whether the energy metabolism of an experimental rodent sarcoma was selectively depressed by the combination of inhibition of glycolysis and respiration. In vivo phosphorus-31 nuclear magnetic resonance spectroscopy was used to monitor the response of tumor or brain high-energy phosphate compounds to insulin hypoglycemia, rhodamine 123, or both agents in fasting rats with subcutaneous methylcholanthrene-induced sarcomas. Insulin or rhodamine 123 alone produced a similar 50% to 60% reduction in tumor adenosine triphosphate (ATP) concentration compared with controls injected with saline solution (p less than 0.05, one-way analysis of variance [ANOVA]). The combination of insulin plus rhodamine 123 resulted in a 90% reduction of tumor ATP concentration, which was significantly different from the effect of either agent alone (p less than 0.05, one-way ANOVA). Brain phosphocreatine and ATP concentrations were unchanged by these agents. Administration of dimethyl sulfoxide (DMSO)/glycerol, the vehicle for rhodamine, produced a 35% reduction of tumor ATP, which was similar to the effect of insulin alone but significantly different from rhodamine. The combination of DMSO/glycerol plus insulin hypoglycemia resulted in a 70% reduction in tumor ATP, which was significantly elevated compared with the combination of rhodamine plus insulin. Glucose deprivation induced by insulin, and combined with the inhibition of oxidative phosphorylation, produces an additive depression of tumor energetics. The drug vehicle DMSO/glycerol significantly depresses tumor energy metabolism, presumably because of its DMSO component, which may explain the previously reported antineoplastic efficacy of this solvent. Combinations of inhibitors directed at different points of tumor metabolism produced an enhanced depression of tumor energetics, whereas host tissue was protected.