Free-amino acid metabolic profiling of visceral adipose tissue from obese subjects.

Interest in adipose tissue pathophysiology and biochemistry have expanded considerably in the past two decades due to the ever increasing and alarming rates of global obesity and its critical outcome defined as metabolic syndrome (MS). This obesity-linked systemic dysfunction generates high risk factors of developing perilous diseases like type 2 diabetes, cardiovascular disease or cancer. Amino acids could play a crucial role in the pathophysiology of the MS onset. Focus of this study was to fully characterize amino acids metabolome modulations in visceral adipose tissues (VAT) from three adult cohorts: (i) obese patients (BMI 43-48) with metabolic syndrome (PO), (ii) obese subjects metabolically well (O), and (iii) non obese individuals (H). 128 metabolites identified as 20 protein amino acids, 85 related compounds and 13 dipeptides were measured by ultrahigh performance liquid chromatography-tandem mass spectroscopy (UPLC-MS/MS) and gas chromatography-/mass spectrometry GC/MS, in visceral fat samples from a total of 53 patients. Our analysis indicates a probable enhanced BCAA (leucine, isoleucine, valine) degradation in both VAT from O and PO subjects, while levels of their oxidation products are increased. Also PO and O VAT samples were characterized by: elevated levels of kynurenine, a catabolic product of tryptophan and precursor of diabetogenic substances, a significant increase of cysteine sulfinic acid levels, a decrease of 1-methylhistidine, and an up regulating trend of 3-methylhistidine levels. We hope this profiling can aid in novel clinical strategies development against the progression from obesity to metabolic syndrome.

Arterial ageing: from endothelial dysfunction to vascular calcification.

Complex structural and functional changes occur in the arterial system with advancing age. The aged artery is characterized by changes in microRNA expression patterns, autophagy, smooth muscle cell migration and proliferation, and arterial calcification with progressively increased mechanical vessel rigidity and stiffness. With age the vascular smooth muscle cells modify their phenotype from contractile to 'synthetic' determining the development of intimal thickening as early as the second decade of life as an adaptive response to forces acting on the arterial wall. The increased permeability observed in intimal thickening could represent the substrate on which low-level atherosclerotic stimuli can promote the development of advanced atherosclerotic lesions. In elderly patients the atherosclerotic plaques tend to be larger with increased vascular stenosis. In these plaques there is a progressive accumulation of both lipids and collagen and a decrease of inflammation. Similarly the plaques from elderly patients show more calcification as compared with those from younger patients. The coronary artery calcium score is a well-established marker of adverse cardiovascular outcomes. The presence of diffuse calcification in a severely stenotic segment probably induces changes in mechanical properties and shear stress of the arterial wall favouring the rupture of a vulnerable lesion in a less stenotic adjacent segment. Oxidative stress and inflammation appear to be the two primary pathological mechanisms of ageing-related endothelial dysfunction even in the absence of clinical disease. Arterial ageing is no longer considered an inexorable process. Only a better understanding of the link between ageing and vascular dysfunction can lead to significant advances in both preventative and therapeutic treatments with the aim that in the future vascular ageing may be halted or even reversed.

Cutaneous mosaicism, in KRT1 pI479T patient, caused by the somatic loss of the wild-type allele, leads to the increase in local severity of the disease.

BACKGROUND: Epidermolytic ichthyosis (BCIE, OMIM 113800), is an autosomal dominant disorder of the skin caused by mutations in keratin genes KRT1 and KRT10. We present two sporadic patients showing a mild diffuse ichthyosis with palmoplantar keratoderma. Interestingly, one of them shows a significant hyperkeratosis of palms and soles similar to those present in the Meleda disease (OMIM 248300). OBJECTIVE: In this paper we would clarify the genetic difference between the two patients, giving rise to the different phenotype. METHODS: Clinical evaluation, followed by histological and molecular analysis has been established for these patients. RESULTS: We demonstrated the presence of a genetic cutaneous mosaicism. Both patients carry the KRT1 pI479T substitution, but in the palmoplantar areas of one of them, only the mutated allele is expressed (hemizygous). This leads to highlight a new type of cutaneous mosaic, the palmoplantar mosaicism.

Two new p73 splice variants, gamma and delta, with different transcriptional activity.

p73 has been recently identified as a new structural and functional homologue of the transcription factor p53. It is expressed in either a full-length form, alpha, or a shorter beta mRNA variant, with exon 13 spliced out. Here we report the identification and functional characterization of two new p73 splicing variants, gamma (splicing out exon 11) and delta (splicing out exons 11, 12, and 13). Both gamma and delta p73 variants are expressed in human peripheral blood lymphocytes, primary keratinocytes, and different tumor cell lines, including neuroblastoma, glioblastoma, melanoma, hepatoma, and leukemia. The expression pattern of the four p73 splicing variants differs in both primary cells of different lineage and established cell lines even within the same type of tumor. A two-hybrid assay was used to characterize the homodimeric and heterodimeric interactions between the p73 variants, and showed that neither p73gamma nor p73delta interact with p53, whereas p73gamma showed strong interactions with all p73 isoforms, and p73delta binds efficiently p73alpha and p73gamma but only weakly p73beta. At the functional level, p73gamma is significantly less efficient in activating transcription of the p21(Waf1/Cip1) promoter than p53 or p73beta, whereas the effect of p73delta is intermediate and comparable to that of p73alpha. The ability of the different p73 variants to affect cell growth in p53 null osteosarcoma SAOS-2 cells correlates with their transcriptional activity on the p21(Waf1/Cip1) promoter: p73beta is the most efficient in inhibiting colony formation, whereas p73gamma is almost ineffective. Our results suggest that p73 isoforms may be differentially regulated, with four different isoforms capable of interacting among themselves and with p53. The relative expression level of each splice variant may modulate p73 transcriptional and growth suppression activities by affecting heterodimer formation.

Expression and localisation of insulin receptor substrate 2 in normal intestine and colorectal tumours. Regulation by intestine-specific transcription factor CDX2.

BACKGROUND AND AIMS: Self-renewal and differentiation of intestinal epithelium is a tightly regulated process, whose perturbations are implicated in human colorectal tumourigenesis. The insulin/insulin-like growth factor (IGF) signalling pathway may play an important role in intestinal epithelium homeostasis. Insulin receptor substrate 2 (IRS2) is a poorly characterised component in this pathway. METHODS: Using complementary in vitro and in vivo human and murine models, expression (mRNA and protein levels), localisation (immunohistochemistry) and regulation of IRS2 were investigated in the normal intestine and colorectal tumours. In silico analysis of the human IRS2 promoter was performed together with reporter and chromatin immunoprecipitation assays. RESULTS: Significant IRS2 expression was detected in the intestine, with specific protein localisation in the villus region of the ileum and in the surface epithelium of the colon. In human HT29 and Caco2 cells, IRS2 mRNA levels increased with spontaneous and induced differentiation, together with CDX2 (caudal-related homeobox protein 2), P21 and KLF4 (Krüppel-like factor 4). Adenoviral infection with human CDX2 induced IRS2 expression in APC- (adenomatous polyposis coli) and beta-catenin-mutated cells. On the other hand, IRS2 downregulation was observed in differentiated enterocytes after adenoviral infection with short hairpin CDX2 (shCDX2), in the intestine of CDX2 heterozygous mice and in colorectal tumours of Apc(Min/+) and patients with familial adenomatous polyposis (FAP). The human IRS2 promoter region presents several CDX2-binding sites where CDX2 immunoprecipitated in vivo. IRS2 reporters were functionally activated via CDX2 and blocked via a dominant-negative CDX2 protein. CONCLUSIONS: Combining gain- and loss-of-function approaches, an intriguing scenario is presented whereby IRS2 is significantly expressed in the apical intestinal compartment and is directly controlled by CDX2 in normal intestine and tumours.

Current treatments of primary sclerosing cholangitis.

Primary Sclerosing Cholangitis (PSC) is a chronic cholestatic disease characterized by hepatic inflammation and obliterative fibrosis, resulting in both intra- and extra-hepatic bile duct strictures. End-stage liver disease and bile duct carcinoma represent frequent complications. Incidence and prevalence of PSC in USA have been recently estimated as 0.9 per 100,000 person-years, and 1-6 per 100,000 person-years, respectively. Major diagnostic criteria include the presence of multifocal strictures, beadings of bile ducts, and compatible biochemical profile, once excluded secondary causes of cholangitis. Since the aetiology of PSC remains poorly defined, medical therapy is currently limited to symptom improvement and prolonged survival. Ursodeoxycholic acid (UDCA), corticosteroids and immunosuppressants have been proposed alone or in combination to improve the clinical outcome. In selected cases, surgical or endoscopic procedures need to be considered. Orthotopic liver transplantation (OLT) is at the moment the only definitive approach although disease relapse has been reported. In this article the state of the art in PSC treatment and future promises in this field are reviewed.

Tissue transglutaminase and apoptosis: sense and antisense transfection studies with human neuroblastoma cells.

In this report, we show that the overexpression of tissue transglutaminase (tTG) in the human neuroblastoma cell line SK-N-BE(2) renders these neural crest-derived cells highly susceptible to death by apoptosis. Cells transfected with a full-length tTG cDNA, under the control of a constitutive promoter, show a drastic reduction in proliferative capacity paralleled by a large increase in cell death rate. The dying tTG-transfected cells exhibit both cytoplasmic and nuclear changes characteristic of cells undergoing apoptosis. The tTG-transfected cells express high Bcl-2 protein levels as well as phenotypic neural cell adhesion molecule markers (NCAM and neurofilaments) of cells differentiating along the neuronal pathway. In keeping with these findings, transfection of neuroblastoma cells with an expression vector containing segments of the human tTG cDNA in antisense orientation resulted in a pronounced decrease of both spontaneous and retinoic acid (RA)-induced apoptosis. We also present evidence that (i) the apoptotic program of these neuroectodermal cells is strictly regulated by RA and (ii) cell death by apoptosis in the human neuroblastoma SK-N-BE(2) cells preferentially occurs in the substrate-adherent phenotype. For the first time, we report here a direct effect of tTG in the phenotypic maturation toward apoptosis. These results indicate that the tTG-dependent irreversible cross-linking of intracellular protein represents an important biochemical event in the induction of the structural changes featuring cells dying by apoptosis.

Gallstone disease: Symptoms and diagnosis of gallbladder stones.

The clinical aspects and the diagnostic features of gallstone disease are described. The natural history of silent gallstones is overviewed, and the risk of developing symptoms and complications is also discussed. The importance of colicky pain as a specific gallstone symptom is highlighted, and the role of both laboratory tests and diagnostic investigations for differential diagnosis is discussed. Finally, we describe the diagnostic features of gallbladder stone disease, including indications, sensitivity, specificity, and limitations of different test investigations under special circumstances.

Apoptosis of N-type neuroblastoma cells after differentiation with 9-cis-retinoic acid and subsequent washout.

BACKGROUND: The overall survival rate for patients with neuroblastoma has improved over the past two decades, but long-term survival for the subgroup of patients with high-risk disease remains low. In recent years, there has been interest in the potential clinical use of drugs able to induce differentiation of neuroblastoma cells. Since 9-cis-retinoic acid induces better and more sustained differentiation of neuroblastoma in vitro than other retinoic acid isomers, this may be a more appropriate retinoid for use in neuroblastoma therapy. PURPOSE: The purpose of this work was to compare the long-term effects of all-trans- and 9-cis-retinoic acid on neuroblastoma differentiation using an N-type (neuroblastic) cell line, SH SY 5Y, as an in vitro model. In addition, we wanted to find out whether 9-cis-retinoic acid would induce programmed cell death (apoptosis) in these N-type neuroblastoma cells and to determine whether the effects of either 9-cis- or all-trans-retinoic acid are dependent on their continued presence in the culture medium. METHODS: SH SY 5Y cells were incubated in either the continued presence of all-trans- or 9-cis-retinoic acid or for 5 days with retinoic acid followed by culture in the absence of retinoid for up to 13 days. Morphologic changes were observed using phase-contrast and scanning electron microscopy. Apoptosis was determined by flow cytometry of propidium iodide-stained cells and by using terminal deoxynucleotidyl transferase to end-label DNA fragments in situ in apoptotic cells. RESULTS: Culture of SH SY 5Y cells with all-trans- or 9-cis retinoic acid for 5 days induced morphologic differentiation and inhibited cell growth. These effects were maintained in the continuous presence of each retinoic acid isomer but were more profound in cells treated with 9-cis-retinoic acid. The differentiation of cells treated with all-trans-retinoic acid was reversible once retinoic acid was removed from the medium. Conversely, apoptosis was induced in cells treated with 9-cis-retinoic acid for 5 days and cultured for 9 days (4 days after washout) but not in cells cultured in the continuous presence of 9-cis-retinoic acid. This effect was specific to 9-cis-retinoic acid. CONCLUSIONS: Previous studies have demonstrated differential responses to all-trans-retinoic acid in N- and S-type (substrate-adherent or Schwann-like) neuroblastoma cells: Apoptosis is induced in S-type cells, whereas differentiation occurs in N-type cells. The present results show that, unlike all-trans-retinoic acid, 9-cis-retinoic acid induces both differentiation and apoptosis in N-type SH SY 5Y neuroblastoma cells. However, apoptosis was dependent on removal of 9-cis-retinoic acid from the culture medium. IMPLICATIONS: Since both differentiation and apoptosis are involved in tumor regression, 9-cis-retinoic acid may be a more appropriate retinoid for clinical trials in neuroblastoma. The dependence of apoptosis on treatment and subsequent removal of 9-cis-retinoic acid implies that drug scheduling may be an important parameter affecting therapeutic efficacy.

ΔNp63 targets cytoglobin to inhibit oxidative stress-induced apoptosis in keratinocytes and lung cancer.

During physiological aerobic metabolism, the epidermis undergoes significant oxidative stress as a result of the production of reactive oxygen species (ROS). To maintain a balanced oxidative state, cells have developed protective antioxidant systems, and preliminary studies suggest that the transcriptional factor p63 is involved in cellular oxidative defence. Supporting this hypothesis, the ΔNp63α isoform of p63 is expressed at high levels in the proliferative basal layer of the epidermis. Here we identify the CYGB gene as a novel transcriptional target of ΔNp63 that is involved in maintaining epidermal oxidative defence. The CYGB gene encodes cytoglobin, a member of the globin protein family, which facilitates the diffusion of oxygen through tissues and acts as a scavenger for nitric oxide or other ROS. By performing promoter activity assays and chromatin immunoprecipitation, reverse transcriptase quantitative PCR and western blotting analyses, we confirm the direct regulation of CYGB by ΔNp63α. We also demonstrate that CYGB has a protective role in proliferating keratinocytes grown under normal conditions, as well as in cells treated with exogenous hydrogen peroxide. These results indicate that ΔNp63, through its target CYGB has an important role in the cellular antioxidant system and protects keratinocytes from oxidative stress-induced apoptosis. The ΔNp63-CYGB axis is also present in lung and breast cancer cell lines, indicating that CYGB-mediated ROS-scavenging activity may also have a role in epithelial tumours. In human lung cancer data sets, the p63-CYGB interaction significantly predicts reduction of patient survival.

p63 controls cell migration and invasion by transcriptional regulation of MTSS1.

Metastasis is a multistep cell-biological process, which is orchestrated by many factors, including metastasis activators and suppressors. Metastasis Suppressor 1 (MTSS1) was originally identified as a metastasis suppressor protein whose expression is lost in metastatic bladder and prostate carcinomas. However, recent findings indicate that MTSS1 acts as oncogene and pro-migratory factor in melanoma tumors. Here, we identify and characterized a molecular mechanism controlling MTSS1 expression, which impinges on a pro-tumorigenic role of MTSS1 in breast tumors. We found that in normal and in cancer cell lines ΔNp63 is able to drive the expression of MTSS1 by binding to a p63-binding responsive element localized in the MTSS1 locus. We reported that ΔNp63 is able to drive the migration of breast tumor cells by inducing the expression of MTSS1. Notably, in three human breast tumors data sets the MTSS1/p63 co-expression is a negative prognostic factor on patient survival, suggesting that the MTSS1/p63 axis might be functionally important to regulate breast tumor progression.

Essential versus accessory aspects of cell death: recommendations of the NCCD 2015.

Cells exposed to extreme physicochemical or mechanical stimuli die in an uncontrollable manner, as a result of their immediate structural breakdown. Such an unavoidable variant of cellular demise is generally referred to as 'accidental cell death' (ACD). In most settings, however, cell death is initiated by a genetically encoded apparatus, correlating with the fact that its course can be altered by pharmacologic or genetic interventions. 'Regulated cell death' (RCD) can occur as part of physiologic programs or can be activated once adaptive responses to perturbations of the extracellular or intracellular microenvironment fail. The biochemical phenomena that accompany RCD may be harnessed to classify it into a few subtypes, which often (but not always) exhibit stereotyped morphologic features. Nonetheless, efficiently inhibiting the processes that are commonly thought to cause RCD, such as the activation of executioner caspases in the course of apoptosis, does not exert true cytoprotective effects in the mammalian system, but simply alters the kinetics of cellular demise as it shifts its morphologic and biochemical correlates. Conversely, bona fide cytoprotection can be achieved by inhibiting the transduction of lethal signals in the early phases of the process, when adaptive responses are still operational. Thus, the mechanisms that truly execute RCD may be less understood, less inhibitable and perhaps more homogeneous than previously thought. Here, the Nomenclature Committee on Cell Death formulates a set of recommendations to help scientists and researchers to discriminate between essential and accessory aspects of cell death.

Hailey-Hailey disease maps to a 5 cM interval on chromosome 3q21-q24.

Hailey-Hailey disease (HHD) is a rare autosomal dominant genodermatosis characterized by disturbed keratinocyte adhesion. The disease has recently been mapped to a 14 cM region on chromosome 3q. We have further refined the location of the HHD gene by linkage analysis in six HHD families from Germany and Italy using 11 polymorphic microsatellite markers and found no evidence for genetic heterogeneity. We observed complete cosegregation between HHD and marker D3S1587, with a maximal lod score of 4.54. Detailed haplotype analyses allowed us to narrow the interval containing the HHD locus to 5 cM, flanked by D3S1589 and D3S1290.

Differential effects of retinoic acid isomers on the expression of nuclear receptor co-regulators in neuroblastoma.

Retinoic acid modulates growth and induces differentiation and apoptosis of neuroblastoma cells in vitro, with the all-trans and 9-cis isomers having different biological properties. Transcriptional activation in response to retinoic acid isomers is mediated by retinoic acid receptors and retinoid X receptors. The differential expression of co-activators and co-repressors which preferentially interact with retinoic acid receptors or retinoid X receptors may be a mechanism leading to different cellular responses to 9-cis and all-trans retinoic acid. To test this hypothesis, we have studied the expression of the nuclear receptor co-regulators TIF1alpha, TIF1beta, SUG1 and SMRT in the N-type and S-type neuroblastoma cell lines SH SY 5Y and SH S EP. Transcripts for all four co-regulators were expressed in these neuroblastoma cells. The expression of TIF1alpha, TIF1beta and SUG1 did not change in response to retinoic acid; however, SMRT was induced in both neuroblastoma cell lines, but particularly by all-trans retinoic acid in SH S EP cells. An additional co-activator, Trip3, was isolated by differential mRNA display and shown to be preferentially induced by 9-cis retinoic acid in SH SY 5Y and SH S EP cells. These data suggest that retinoic acid isomer-specific induction of nuclear receptor co-regulators may determine, in part, the differential biological effects of retinoic acid isomers.

Cell death by oxidative stress and ascorbic acid regeneration in human neuroectodermal cell lines.

In this paper, we show that human neuroectodermal cells exposed to 1-5 mM hydrogen peroxide or 10 nM-1 mM ascorbate die by programmed cell death induced by oxidative stress. The cell death by peroxide occurs within 4 h and involves approximately 80% of B-mel melanoma cells, while ascorbate causes cell death of approximately 86% of B-mel cells within 24 h. SK-N-BE(2) neuroblastoma cells are more resistant, 32% and 43% cell death for peroxide and ascorbate, respectively. In all cases, cell death causes hypodiploic DNA staining, evaluated by flow cytometry. Both cell lines can efficiently metabolise ascorbate due to significant levels of NADH-dependent semidehydroascorbate reductase and glutathione-dependent dehydroascorbate reductase. The cell death observed suggests a pro-oxidant, rather than anti-oxidant, role for ascorbic acid at physiological concentrations under these experimental conditions.

Retinoids in neuroblastoma therapy: distinct biological properties of 9-cis- and all-trans-retinoic acid.

We investigated the potential for 9-cis-retinoic acid in the differentiation therapy of neuroblastoma using an N-type neuroblastoma cell line, SH SY 5Y, as an experimental model. In these cells, 9-cis-retinoic acid is more effective than other isomers at inducing the expression of RAR-beta. An RAR-alpha-specific antagonist inhibited the induction of RAR-beta in response to all-trans-but not to 9-cis-retinoic acid. This indicates that the mechanism of gene induction by 9-cis-retinoic acid differs markedly from all-trans-retinoic acid. 9-cis-retinoic acid is also better than all-trans at producing sustained morphological differentiation and inhibition of proliferation of SH SY 5Y cells. Although N-type neuroblastoma cells are not thought to undergo apoptosis in response to all-trans-retinoic acid, we observed a significant degree of apoptosis in SH SY 5Y cells treated with 9-cis-retinoic acid for 5 days and then cultured in the absence of retinoid, an effect not observed in cells treated with the all-trans isomer. These results suggest that 9-cis- and all-trans-retinoic acid have distinct biological properties and that 9-cis retinoic acid may be clinically effective in neuroblastoma by inducing both differentiation and apoptosis under an appropriate treatment regimen.

Expression and down-regulation by retinoic acid of IGF binding protein-2 and -4 in medium from human neuroblastoma cells.

Insulin-like growth factors (IGFs) regulate the autocrine/paracrine growth of neuroblastomas. The IGFs bind to specific binding proteins (IGFBPs) which modulate their biological activity. We investigated, by Western ligand blotting (WLB), the presence of IGFBPs and their possible modulation by retinoic acid (RA), IGF-I, IGF-II and truncated Des(1-3)IGF-I in conditioned medium (CM) of the human neuroblastoma SK-N-BE(2) cell line. We demonstrated the presence of two IGFBPs, with MW 37 kDa and 25 kDa. Following immunoprecipitation, they turned out to be IGFBP-2 and -4, respectively. The RA-induced differentiation in SK-N-BE(2) cells was accompanied by a marked reduction of the intensity of both IGFBP bands after 48 h (32% and 24% of control, respectively) and 72 h (2% and 0% of control, respectively) incubation. The addition of exogenous IGFs, which did not induce cell differentiation, did not change the IGFBP pattern significantly, except for the truncated form of IGF-I, which induced a marked decrease in both the 37 kDa and 25 kDa bands after 72 h incubation (45% and 18% of control, respectively). These findings suggest that IGFBPs have a role in RA-induced differentiation in human neuroblastoma cells.

Interleukin-6 and corticotrophin-releasing hormone mRNA are modulated during differentiation of human neuroblastoma cells.

Two cell clones [BE(2)-C and BE(2)-M17] derived from the human neuroblastoma cell line SK-N-BE(2) express corticotrophin-releasing hormone as well as interleukin-6 mRNA. Both genes are overexpressed, although with a different time course, following exposure to 5 microM retinoic acid, in parallel to the induction of neuroblastic differentiation. On the contrary, we are unable to detect interleukin-1 beta mRNA in these cell lines. Both cytokines are known to increase hypothalamic CRH mRNA. The production of cytokines and neuropeptides by neuroblastoma cells indicate a complex dialogue between tumour cells and anti-tumour immunity.

IGF-II mRNA expression in LI human glioblastoma cell line parallels cell growth.

A human glioblastoma cell line was found to express in vitro mRNA transcripts specific for insulin-like growth factor-II (IGF-II) and growth-hormone releasing-hormone (GHRH). In the absence of gross morphological changes, retinoic acid reduced the growth rate without major change of IGF-II mRNA expression, while alpha-difluoromethylornithine produced a complete growth arrest and a sharp decrease of IGF-II mRNA expression. Both reagents increased the expression of GHRH mRNA. Also in this glioblastoma cell line, like other neuroectodermal tumours, IGF-II mRNA is expressed independently from GHRH and seems to be parallel to growth rate.

Modulation of IGF-2 expression during growth and differentiation of human neuroblastoma cells: retinoic acid may induce IGF-2.

Insulin-like growth factor 2 (IGF-2) is the major autocrine growth factor for neuroblastoma. IGF-2 mRNA can just be detected in SK-N-BE(2) cell line; higher levels are present in two clones derived from it [BE(2)-C; BE(2)-M17]. IGF-2 mRNA is increased by retinoic acid (RA) only in the clones. IGF-2 expression/induction is more marked in BE(2)-M17, which shows more RA-resistance (evaluated as growth inhibition, neurite outgrowth and induction of programmed cell death). Under RA exposure, the parental line shows a more pronounced growth inhibition, neurite outgrowth and programmed cell death, as compared to its clones. BE(2)-C cells also express type 1 IGF receptor mRNA, though with a different time course than for expression of IGF-2. The data suggest that IGF-2 expression is correlated with growth, and may counteract the growth retardation, neurite outgrowth and programmed cell death effects of retinoic acid. Therefore the autocrine pattern of IGF-2 production by neuroblastoma cells may promote RA-resistance.