MYC inhibition induces metabolic changes leading to accumulation of lipid droplets in tumor cells

The MYC genes are the most frequently activated oncogenes in human tumors and are hence attractive therapeutic targets. MYCN amplification leads to poor clinical outcome in childhood neuroblastoma, yet strategies to modulate the function of MYCN do not exist. Here we show that 10058-F4, a characterized c-MYC/Max inhibitor, also targets the MYCN/Max interaction, leading to cell cycle arrest, apoptosis, and neuronal differentiation in MYCN-amplified neuroblastoma cells and to increased survival of MYCN transgenic mice. We also report the discovery that inhibition of MYC is accompanied by accumulation of intracellular lipid droplets in tumor cells as a direct consequence of mitochondrial dysfunction. This study expands on the current knowledge of how MYC proteins control the metabolic reprogramming of cancer cells, especially highlighting lipid metabolism and the respiratory chain as important pathways involved in neuroblastoma pathogenesis. Together our data support direct MYC inhibition as a promising strategy for the treatment of MYC-driven tumors.     

Loss of heterozygosity for the short arm of chromosome 1 in human neuroblastomas: correlation with N-myc amplification.

Partial monosomy of the short arm of chromosome 1 is the most consistent cytogenetic abnormality found in human neuroblastomas, but its overall frequency and significance are unclear. Using a panel of chromosome-1-specific DNA probes that identify restriction fragment length polymorphisms, we demonstrate that 13 of 47 human neuroblastomas (28%) have somatic loss of heterozygosity (LOH) at one or more loci on the distal short arm of chromosome 1. the chromosomal region that shows LOH most consistently is between 1p36.1 and 1p36.3; loss of a gene or genes in this region may be critical for the development or progression of neuroblastomas. The region of LOH in human neuroblastoma may resemble that described for pheochromocytoma, medullary thyroid carcinoma, and melanoma, which are also tumors of neural-crest origin. Although LOH for distal chromosome 1p can occur in early stages of neuroblastoma, the loss usually occurs in tumors of advanced clinical stages. LOH for the short arm of chromosome 1 correlates significantly with N-myc amplification, suggesting that these two genetic events are related. Indeed, these two lesions appear to characterize a genetically distinct subset of particularly aggressive neuroblastomas.     

COX/mPGES-1/PGE2 pathway depicts an inflammatory-dependent high-risk neuroblastoma subset

The majority of solid tumors are presented with an inflammatory microenvironment. Proinflammatory lipid mediators including prostaglandin E₂ (PGE₂) contribute to the establishment of inflammation and have been linked to tumor growth and aggressiveness. Here we show that high-risk neuroblastoma with deletion of chromosome 11q represents an inflammatory subset of neuroblastomas. Analysis of enzymes involved in the production of proinflammatory lipid mediators showed that 11q-deleted neuroblastoma tumors express high levels of microsomal prostaglandin E synthase-1 (mPGES-1) and elevated levels of PGE₂. High mPGES-1 expression also corresponded to poor survival of neuroblastoma patients. Investigation of the tumor microenvironment showed high infiltration of tumor-promoting macrophages with high expression of the M2-polarization markers CD163 and CD206. mPGES-1–expressing cells in tumors from different subtypes of neuroblastoma showed differential expression of one or several cancer-associated fibroblast markers such as vimentin, fibroblast activation protein α, α smooth muscle actin, and PDGF receptor β. Importantly, inhibition of PGE₂ production with diclofenac, a nonselective COX inhibitor, resulted in reduced tumor growth in an in vivo model of 11q-deleted neuroblastoma. Collectively, these results suggest that PGE₂ is involved in the tumor microenvironment of specific neuroblastoma subgroups and indicate that therapeutic strategies using existing anti-inflammatory drugs in combination with current treatment should be considered for certain neuroblastomas.Neuroblastoma is the most common and deadliest tumor of childhood. Although the survival of children with neuroblastoma has improved during the last decade, patients with high-risk disease still have a poor prognosis, despite advanced and intensive treatments, with overall survival rates less than 40% (1). The International Neuroblastoma Risk Group (INRG) classification system defines neuroblastoma risk groups as low, intermediate, and high, based on age at diagnosis, histology, and genetic aberrations (2). Among high-risk neuroblastomas, amplification of the neuroblastoma MYC (MYCN) oncogene is the most frequent genetic aberration, seen in 30–40% of the patients. Another common genetic change in the high-risk group is deletion of the long arm of chromosome 11 (11q-deletion). Deletion of 11q occurs in tumors with multiple genetic aberrations and chromosome instability but commonly without MYCN-amplification and therefore is a useful prognostic marker in adverse-stage tumors lacking MYCN-amplification (3). These patients are often older at disease onset and have slow disease progression but often develop therapy resistance and have poor clinical outcome. Among low- and intermediate-risk neuroblastomas are the so-called “special neuroblastomas” (4S) that show a metastatic phenotype but are associated with spontaneous regression and a survival rate of 90% (1, 4, 5).Prostaglandins are bioactive lipids involved in many biological processes both in physiological processes e.g., blood pressure, smooth muscles contraction, and protection of the intestinal mucosa, and in pathological conditions such as autoimmune diseases and cancer (6). Prostaglandins are formed by the conversion of arachidonic acid to prostaglandin H₂ (PGH₂) by the cyclooxygenases COX-1 and COX-2, followed by further processing by terminal enzymes, the prostaglandin synthases. Prostaglandin E₂ (PGE₂) is a proinflammatory and immunomodulatory lipid mediator formed from PGH₂ by microsomal prostaglandin E synthase 1 (mPGES-1). Elevated levels of mPGES-1 and its enzymatic product PGE₂ have been found in several different cancers, including colon cancer (7–9), nonsmall cell lung cancer (10), and prostate cancer (11, 12). PGE₂ signaling contributes to increased proliferation (13, 14) and invasiveness (15) of cancer cells, stimulates tumor angiogenesis (16, 17), inhibit apoptosis (18), induces chemoresistance (19), and mediates suppression of anti-tumor immunity (20, 21). Because tumor-promoting inflammation has been included as one of the hallmarks of cancer (22), chronic inflammation and its impact on tumorigenesis in adult tumors have been immensely investigated.Less is known about the inflammatory component in childhood tumors; however, in a recent study, Asgharzadeh et al. (23) showed that infiltration of immunosuppressive M2-polarized macrophages in metastatic MYCN-nonamplified neuroblastoma tumors contributed to the metastatic phenotype and worsened the outcome of these patients. Cancer-associated fibroblasts (CAFs) also have been found to contribute to tumor development and metastasis (24), and in a study by Zeine et al. (25) a high number of CAFs was found to correlate with more aggressive Schwannian stroma-poor neuroblastoma tumors.We previously reported the effect of anti-inflammatory drugs on tumor growth in preclinical in vivo models of neuroblastoma (26–28). We also have found high expression of the PGE₂ receptors EP1–EP4 in neuroblastoma tumor tissue as well as effects of PGE₂ on neuroblastoma cell growth in vitro (29). These results suggest that inflammatory processes are important for neuroblastoma growth. Therefore we investigated the importance of proinflammatory prostaglandins and their enzymes in neuroblastoma subgroups.     

Sellar Neuroblastoma Mimicking Pituitary Adenoma

Objective and importance: Primary intracranial neuroblastomas are rare. They generally arise in the supratentorial parenchyma or paraventricular region. Even more rare are primary sellar neuroblastomas. We present a neuroblastoma that arose in the sellar region and mimicked a non-functioning pituitary adenoma. Clinical presentation: This 33-year-old man presented with bitemporal hemianopsia. MRI showed a sellar mass with suprasellar extension mimicking a pituitary adenoma. Intervention: Because of tumor recurrence and dissemination to the cervical region, he underwent 6 operations and radiosurgery. Detailed histologic examination confirmed the diagnosis of neuroblastoma. Postoperative conventional radiotherapy was effective in reducing the size of the tumor. Conclusion: Neuroblastoma should be considered in the differential diagnosis of patients with sellar lesions.     

Proliferate and survive: cell division cycle and apoptosis in human neuroblastoma

BACKGROUND AND OBJECTIVES: Neuroblastoma is one of the most frequent childhood cancers and a major cause of death from neoplasias of infancy. Although a wealth of studies on its molecular bases have been carried out, little conclusive information about its origin and evolution is available. EVIDENCE AND INFORMATION SOURCES: Some intriguing findings have correlated neuroblastoma development with aberrations of two pivotal cellular processes generally altered in human cancers, namely cell division cycle and apoptosis. Indeed, it has been reported that neuroblastoma cell lines show accumulation of Id2 protein, a factor which is able to hamper the pRb protein antiproliferative activity. STATE OF THE ART: The increased Id2 is due to N-myc gene amplification and overexpression, a phenomenon frequently observed in neuroblastoma and an important independent negative marker. Moreover, neuroblastoma cells are frequently characterized by increased levels of survivin, an inhibitor of the apoptotic response, and by a deficiency of procaspase 8, a key intermediate of the programmed cell death cascade. These two events, probably, make neuroblastomas more resistant to programmed cell death. These recent findings might suggest that neuroblastoma cells have acquired the capability to proliferate easily and die difficultly. PERSPECTIVES: The mechanistic meaning of these data will be discussed in the present review. Moreover, we will suggest new therapeutic scenarios opened up by the described alterations of cell cycle and apoptosis engines.     

ESTABLISHMENT OF FUNCTIONAL CLONAL LINES OF NEURONS FROM MOUSE NEUROBLASTOMA

Clonal lines of neurons were obtained in culture from a mouse neuroblastoma. The neuroblastoma cells were adapted to culture growth by the animal-culture alternate passage technique and cloned after single-cell plating. The clonal lines retained the ability to form tumors when injected back into mice. A striking morphological change was observed in the cells adapted to culture growth; they appeared as mature neurons, while the cells of the tumor appeared as immature neuroblasts.Acetylcholinesterase and the enzymes for the synthesis of neurotransmitters, cholineacetylase and tyrosine hydroxylase were assayed in the tumor and compared with brain levels; tyrosine hydroxylase was found to be particularly high, as described previously in human neuroblastomas. The three enzymes were found in the clonal cultures at levels comparable to those found in the tumors. Similarly, there were no remarkable differences between the three clones examined.     

Evaluation of Epstein-Barr virus infection in sinonasal small round cell tumors

 Sinonasal undifferentiated carcinoma, olfactory neuroblastoma and malignant melanoma of the sinonasal regions are included within the category of small round cell tumors of the sinonasal region. It is difficult to diagnose these tumors on the basis of light-microscopic features alone, but, in some instances, immunohistochemical staining evaluating cytokeratin and S-100 protein, for example, is of value. On the other hand, the sinonasal region is a significant site for Epstein-Barr-virus (EBV)-related tumors, including sinonasal undifferentiated carcinoma or malignant lymphoma. Twenty-three sinonasal small round cell tumors (SSRCT) comprising 5 sinonasal undifferentiated carcinomas, 9 olfactory neuroblastomas and 9 malignant melanomas were evaluated for the presence of EBV infection by in situ hybridization for EBV-encoded RNA, combined with immunostaining for EBV-related proteins (LMP-1 and EBNA2). Furthermore, 55 SSRCT comprising 37 sinonasal undifferentiated carcinomas, 9 olfactory neuroblastomas, and 9 malignant melanomas were examined for the presence of cytokeratins (AE1/AE3 and CAM5.2), S-100 protein and p53 protein using immunohistochemical staining. According to in situ hybridization for detecting EBV-encoded RNA 1 (EBER1), all of the sinonasal undifferentiated carcinomas showed clear, intense hybridization signals localized over the nuclei of the tumor cells and, in 3 out of 9 (33.3%) malignant melanomas, hybridization signals were also recognized. However, none of the olfactory neuroblastomas revealed hybridization signals. Immunohistochemically, 4 out of 5 (80%) sinonasal undifferentiated carcinomas were positive for LMP-1, whereas only 2 out 9 (22.2%) malignant melanomas and no olfactory neuroblastomas were positive. With regard to EBNA2, sinonasal undifferentiated carcinomas, malignant melanomas and olfactory neuroblastomas were all negative. Out of 37 sinonasal undifferentiated carcinomas 35 (94.6%) showed a diffuse positive immunoreaction for AE1/AE3, whereas neither olfactory neuroblastoma nor malignant melanoma revealed a positive reaction. All 9 malignant melanomas and 6 out of 9 olfactory neuroblastomas (75%) were positive for S-100 protein, whereas only 6 cases of sinonasal undifferentiated carcinomas (19.4%) were positive. As for p53 protein, 16 of 37 sinonasal undifferentiated carcinomas (43.2%) were positive, whereas neither olfactory neuroblastoma nor malignant melanoma revealed any positive reaction. The above results suggest that EBV infection is closely associated with sinonasal undifferentiated carcinomas, and that some malignant melanomas may also have a relationship with its infection. For the differential diagnosis of SSRCT, it is important to evaluate EBV infection along with immunohistochemical staining for cytokeratins and S-100 protein. The overexpression of p53 protein was found to be related to the oncogenesis of sinonasal undifferentiated carcinoma; however, there was no association between its overexpression and malignant melanoma or olfactory neuroblastoma. Received: 7 April 1999 / Accepted: 10 August 1999     

Two cases of ectopic adrenocorticotropic hormone syndrome with olfactory neuroblastoma and literature review

Olfactory neuroblastomas are rare, slow-growing malignant tumors, usually diagnosed at advanced stages. Ectopic adrenocorticotropic hormone (ACTH) syndrome caused by an olfactory neuroblastoma is extremely rare. We reported two Korean women who suffered from ectopic ACTH syndrome (EAS) caused by olfactory neuroblastomas. The first patient was a 66-year-old woman who had been diagnosed as olfactory neuroblastoma and refused the management two years before and the second patient was a 37-year-old woman on chemotherapy for olfactory neuroblastoma. In the first case, she presented the Cushingoid appearance with systemic edema and her tumor was removed surgically. ACTH secretion by the tissue was confirmed by immunohistochemistry. By contrast, the second patient presented as severe pneumonia caused by cytomegalovirus and was treated with anti-viral agent followed by chemotherapy and radiotherapy, and her residual mass remained. However, after treatment, both patients' plasma ACTH and cortisol levels returned to normal without any adrenolytic therapy. Considering the causative tumors of EAS can be rarely cured and EAS increases the susceptibility to infections, it is prudent to suppress any hypercortisolemia initially, apart from treating the causal malignancy.     

Expression of melanin-concentrating hormone receptor messenger ribonucleic acid in tumor tissues of pheochromocytoma, ganglioneuroblastoma, and neuroblastoma

Expression of melanin-concentrating hormone (MCH) receptor messenger ribonucleic acid (mRNA) was studied by RT-PCR and Northern blot analysis in human brain; pituitary; adrenal glands; tumor tissues of adrenal tumors, ganglioneuroblastomas, and neuroblastomas; and various cultured tumor cell lines. RT-PCR analysis showed that MCH receptor mRNA was widely expressed in brain tissues, pituitary, normal portions of adrenal glands (cortex and medulla), tumor tissues of adrenocortical tumors (12 of 13 cases), pheochromocytoma (all 7 cases), ganglioneuroblastoma (1 case), neuroblastoma (all 5 cases), and various cultured tumor cell lines (6 of 7 cell lines), including 2 neuroblastoma cell lines. Northern blot analysis showed the expression of MCH receptor mRNA ( approximately 2.4 kb) only in the tumor tissues of 5 pheochromocytomas, 1 ganglioneuroblastoma, and 4 neuroblastomas, indicating that the expression levels of MCH receptor mRNA are much higher in these tumors than in the other tissues. These findings raised the possibility that MCH or MCH-like peptides may be related to the pathophysiology of these neural crest-derived tumors.     

New functional imaging modalities for chromaffin tumors, neuroblastomas and ganglioneuromas.

Nuclear medicine modalities use radiolabeled ligands that either follow metabolic pathways or act on cellular receptors. Thus, they permit functional imaging of physiological processes and help to localize sites such as tumors that harbor pathological events. The application of positron emission tomography (PET) ligands to the specific pathways of synthesis, metabolism and inactivation of catecholamines found in chromaffin tumors, neuroblastomas and ganglioneuromas can be used to provide a more thorough localization of these types of tumor. Recent advances have been made in functional imaging to localize pheochromocytomas, paragangliomas, neuroblastomas and ganglioneuromas, including approaches based on PET with [(18)F]fluorodopamine, [(18)F]fluorohydroxyphenylalanine, [(11)C]epinephrine or [(11)C]hydroxyephedrine. Such functional imaging can complement computed tomography or magnetic resonance imaging and other scintigraphic techniques to localize these tumors before surgical or medical therapeutic approaches are considered.     

Second thyroid neoplasms after prophylactic cranial irradiation for acute lymphoblastic leukemia

An understanding of the pathogenesis of second cancers may help in their prevention. We report on two children who were treated for acute lymphoblastic leukemia (ALL), with an exclusively cranial prophylactic irradiation (18 Gy) and who presented with a thyroid carcinoma (TC) 12 and 13 years later. From a thorough review of the literature of TC after ALL and of radiation-induced TC, a strong case can be made that these tumors are caused by late effects of scattered radiation. The risk is at its highest in small children. After cranial irradiation, patients require clinical monitoring of the thyroid and cervical area for nodules, continued indefinitely. We suggest that, in most cases, an alternative form of neuromeningeal prophylaxis should be offered in small children with ALL. Am. J. Hematol. 59:91–94, 1998. © 1998 Wiley-Liss, Inc.     

Catastrophic ATP loss underlies a metabolic combination therapy tailored for MYCN-amplified neuroblastoma

MYCN-amplified neuroblastoma is a lethal subset of pediatric cancer. MYCN drives numerous effects in the cell, including metabolic changes that are critical for oncogenesis. The understanding that both compensatory pathways and intrinsic redundancy in cell systems exists implies that the use of combination therapies for effective and durable responses is necessary. Additionally, the most effective targeted therapies exploit an “Achilles’ heel” and are tailored to the genetics of the cancer under study. We performed an unbiased screen on select metabolic targeted therapy combinations and correlated sensitivity with over 20 subsets of cancer. We found that MYCN-amplified neuroblastoma is hypersensitive to the combination of an inhibitor of the lactate transporter MCT1, AZD3965, and complex I of the mitochondrion, phenformin. Our data demonstrate that MCT4 is highly correlated with resistance to the combination in the screen and lowly expressed in MYCN-amplified neuroblastoma. Low MCT4 combines with high expression of the MCT2 and MCT1 chaperone CD147 in MYCN-amplified neuroblastoma, altogether conferring sensitivity to the AZD3965 and phenformin combination. The result is simultaneous disruption of glycolysis and oxidative phosphorylation, resulting in dramatic disruption of adenosine triphosphate (ATP) production, endoplasmic reticulum stress, and cell death. In mouse models of MYCN-amplified neuroblastoma, the combination was tolerable at concentrations where it shrank tumors and did not increase white-blood-cell toxicity compared to single drugs. Therefore, we demonstrate that a metabolic combination screen can identify vulnerabilities in subsets of cancer and put forth a metabolic combination therapy tailored for MYCN-amplified neuroblastoma that demonstrates efficacy and tolerability in vivo.

Despite their relative rarity compared to blood cancers, solid-tumor pediatric cancers are now the leading cause of pediatric cancer-related deaths. Among the most deadly is high-risk neuroblastoma (NB): amplification of MYCN confers high risk and is the clear driver of NB in these cancers (1). As such, MYCN remains the most important drug target in NB and one of the most important in pediatric cancer. Unfortunately, direct chemical targeting of MYCN has not yet been successful, and despite advancements in anti-GD2 immunotherapy (2), alternate ways of targeting MYCN-amplified NB may be needed to successfully treat this cancer.One approach is to find tumor-specific vulnerabilities, which are exploitable pharmacologically. Many efforts, including ours (3), have exhaustively looked for kinase inhibitors with particular efficacy in MYCN-amplified NBs. However, the emerging picture is a lack of kinase inhibitor efficacy in MYCN-amplified NB. Other vulnerabilities may be classified under the broad category of drugs targeting epigenetic modifiers. For example, using a CRISPR/Cas9 screen, Stegmaier and colleagues demonstrated that MYCN-amplified NB may be susceptible to targeting the H3K27me methylase EZH2 (4); in a different study, they demonstrated the susceptibility of MYCN-amplified NB to the combination of BRD4 inhibitors with CDK7 inhibitors (5). In addition, Thiele and colleagues (6) demonstrated high-risk NBs were susceptible to inhibition of the lysine methyltransferase SETD8. As promising as these data are, it remains unknown whether tolerability and/or clinical activity in MYCN-amplified NB will occur and SETD8, BRD4, and CDK7 inhibitors so far are not in the pediatric clinic. Cell death inducers constitute a third category. To this point, we recently uncovered a susceptibility of MYCN-amplified NB to the BCL-2 inhibitor venetoclax (3), confirmed by others (7). There, MYCN-driven NOXA expression sensitizes cells to venetoclax (3). Venetoclax is now in early phase trials in pediatric patients including those with NB ({"type":"clinical-trial","attrs":{"text":"NCT03236857","term_id":"NCT03236857"}}NCT03236857). It remains to be seen whether or not it will elicit responses in NB patients as a single agent.A fourth distinct category of therapeutic strategies to indirectly target oncogenes is through metabolism targeting, involving the growing coterie of drugs targeting the pathways fulfilling the high-energy demands of cancer cells. A major energy currency in cells is adenosine triphosphate (ATP). The Warburg effect describes the propensity of cancer cells (and highly proliferating normal cells) to produce ATP in the presence of oxygen with the less efficient, extramitochondrial glycolysis, as opposed to the more efficient mitochondria-based oxidative phosphorylation occurring in most noncancerous cells (8). The mechanistic explanation of the Warburg effect and how it might benefit cancer cells has been revised dramatically over the years. It was originally proposed that mitochondria from cancer cells were defective and lacked oxidative phosphorylation capabilities (9); on the contrary, emerging data show that many cancers rely on oxidative phosphorylation to facilitate the generation of ATP (8, 10). Interestingly, while amplified MYCN directly regulates the expression of many of the key glycolytic enzymes and as such contributes to the Warburg effect (11, 12), a study utilizing a Seahorse respirator demonstrated that a MYCN-amplified NB cell line favored oxidative phosphorylation over glycolysis for the metabolic needs, while the reverse was true for a MYCN wild-type NB cell line (13). In an independent study, MYCN was associated with higher glycolytic flux and oxidative phosphorylation and conferred sensitivity to fatty acid oxidation disruption (12). Overall, since c-MYC, which shares ∼40% binding homology to DNA-binding sites throughout the genome with MYCN, has been extensively characterized as a metabolic master regulator (14, 15), it is likely there are other MYCN-driven metabolic processes that may represent significant drug targets.Monocarboxylate transporters (MCTs) consist of four members (MCT1–4) in mammalian cells. Among their most critical substrates are lactate and pyruvate; MCT1 and MCT4 are responsible for lactate export across the plasma membrane to the extracellular space (16). AZD3965 (17) (AstraZeneca) is the first in-class–specific MCT1/2 dual inhibitor and is currently in early phase trials for diverse cancers; however, other inhibitors from different companies have recently been developed as well (18). Of note, AZD3965 has demonstrated good tolerability in diverse patients (clinical trial number {"type":"clinical-trial","attrs":{"text":"NCT01791595","term_id":"NCT01791595"}}NCT01791595). Although rare (65 cases/100,000 person-years), lactic acidosis led to the market retrieval of phenformin in America (19), yet phenformin remains in use as a type II antidiabetic drug in Europe, functioning centrally as a mitochondrial complex I electron transport chain (ETC) inhibitor. Phenformin reduces both glycolytic intermediates and pyruvate, increases shunting of glucose-derived carbon (increasing total lactate production), and markedly reduces tricarboxylic acid cycle intermediates (20). Indeed, there has been a recent resurgence in interest in the use of phenformin to treat cancer. For example, in BRAF mutant melanoma, phenformin sensitized cells to BRAF inhibitor through cooperative suppression of the metabolic sensor pathway mTORC1 (21). These preclinical data have led to a clinical trial of phenformin in combination with BRAF inhibitor in BRAF mutant melanoma ({"type":"clinical-trial","attrs":{"text":"NCT03026517","term_id":"NCT03026517"}}NCT03026517). Overall, while targeting individual metabolic pathways has demonstrated some preclinical success in different cancer models, it is limited with significant redundancy in pathways to generate ATP and regenerate NAD+ (22). We therefore assessed potential combination therapies involving metabolic targeting drugs to identify a strategy for MYCN-amplified NB.     

Differential amplification, assembly, and relocation of multiple DNA sequences in human neuroblastomas and neuroblastoma cell lines.

DNA amplification, manifested by homogeneously staining regions in chromosomes and by extrachromosomal, double minute bodies, is characteristic of many neuroblastoma cell lines. Sequences recruited from a specific domain on the short arm of chromosome 2 (2p) are amplified in advanced-stage primary neuroblastomas, whereas sequences from distinctly different regions of 2p are amplified in the neuroblastoma cell line IMR-32. Five different DNA segments, which include the oncogene N-myc, three other fragments derived from the homogeneously staining region of the neuroblastoma cell line IMR-32, and a fifth fragment, derived from the neuroblastoma cell line NB-9, showed differential and variable amplification in 24 advanced-stage neuroblastoma tumors out of 112 tested specimens. All five fragments were mapped within the chromosomal region 2p23-2p25 by three different approaches. However, eight other fragments cloned from the homogeneously staining region of IMR-32 cells, which were not amplified in the tumor tissues examined, were mapped to two more proximal domains of 2p, thousands of kilobases apart from each other and from the chromosomal domain that is amplified in the tumors. These results establish the amplification, to different degrees, of a variable-sized segment of one domain near the terminus of 2p in advanced neuroblastomas. These tumors might ultimately be distinguished according to the pattern of amplification of DNA segments within this domain. The data presented also indicate the existence of a new and complex amplification mechanism in at least one neuroblastoma cell line (IMR-32), which involves not only relocation of DNA from specific genomic domains but also the formation of novel units by splicing together very distant DNA segments.     

Nephroblastoma and neuroblastoma — histology and prognosis

Summary Statistically evaluating the influence of a histological grading, respectively of morphological differences on prognosis of nephroblastomas and neuroblastomas, better chances for survival become evident not only for earlier clinical stages, but also for nephroblastomas with high differentiation, or neuroblastomas with signs for differentiation. Only for neuroblastomas a relevant predeliction of tumors with signs of differentiation for the early clinical stage I is present.Combined subclassification according to clinical stages and histological grades results in 3 risk groups with different chances for survival. These 3 groups may play a role for specific therapeutic considerations.     

The role of estrogen deficiency in skin ageing and wound healing

The links between hormonal signalling and lifespan have been well documented in a range of model organisms. For example, in C. elegans or D. melanogaster, lifespan can be modulated by ablating germline cells, or manipulating reproductive history or pregnenolone signalling. In mammalian systems, however, hormonal contribution to longevity is less well understood. With increasing age human steroid hormone profiles change substantially, particularly following menopause in women. This article reviews recent links between steroid sex hormones and ageing, with special emphasis on the skin and wound repair. Estrogen, which substantially decreases with advancing age in both males and females, protects against multiple aspects of cellular ageing in rodent models, including oxidative damage, telomere shortening and cellular senescence. Estrogen’s effects are particularly pronounced in the skin where cutaneous changes post-menopause are well documented, and can be partially reversed by classical Hormone Replacement Therapy (HRT). Our research shows that while chronological ageing has clear effects on skin wound healing, falling estrogen levels are the principle mediator of these effects. Thus, both HRT and topical estrogen replacement substantially accelerate healing in elderly humans, but are associated with unwanted deleterious effects, particularly cancer promotion. In fact, much current research effort is being invested in exploring the therapeutic potential of estrogen signalling manipulation to reverse age-associated pathology in peripheral tissues. In the case of the skin the differential targeting of estrogen receptors to promote healing in aged subjects is a real therapeutic possibility.     

Stem cell origin of cancer and differentiation therapy

Our forefathers in pathology, on observing cancer tissue under the microscope in the mid-19th century, noticed the similarity between embryonic tissue and cancer, and suggested that tumors arise from embryo-like cells [Recherches dur le Traitement du Cancer, etc. Paris. (1829); Editoral Archiv fuer pathologische Anatomie und Physiologie und fuer klinische Medizin 8 (1855) 23]. The concept that adult tissues contain embryonic remnants that generally lie dormant, but that could be activated to become cancer was later formalized by Cohnheim [Path. Anat. Physiol. Klin. Med. 40 (1867) 1-79; Virchows Arch. 65 (1875) 64] and Durante [Arch. Memori ed Osservazioni di Chirugia Practica 11 (1874) 217-226], as the "embryonal rest" theory of cancer. An updated version of the embryonal rest theory of cancer is that cancers arise from tissue stem cells in adults. Analysis of the cellular origin of carcinomas of different organs indicates that there is, in each instance, a determined stem cell required for normal tissue renewal that is the most likely cell of origin of carcinomas [Lab. Investig. 70 (1994) 6-22]. In the present review, the nature of normal stem cells (embryonal, germinal and somatic) is presented and their relationships to cancer are further expanded. Cell signaling pathways shared by embryonic cells and cancer cells suggest a possible link between embryonic cells and cancer cells. Wilm's tumors (nephroblastomas) and neuroblastomas are presented as possible tumors of embryonic rests in children. Teratocarcinoma is used as the classic example of the totipotent cancer stem cell which can be influenced by its environment to differentiate into a mature adult cell. The observation that "promotion" of an epidermal cancer may be accomplished months or even years after the initial exposure to carcinogen ("initiation"), implies that the original carcinogenic event occurs in a long-lived epithelial stem cell population. The cellular events during hepatocarcinogenesis illustrate that cancers may arise from cells at various stages of differentiation in the hepatocyte lineage. Examples of genetic mutations in epithelial and hematopoietic cancers show how specific alterations in gene expression may be manifested as maturation arrest of a cell lineage at a specific stage of differentiation. Understanding the signals that control normal development may eventually lead us to insights in treating cancer by inducing its differentiation (differentiation therapy). Retinoid acid (RA) induced differentiation therapy has acquired a therapeutic niche in treatment of acute promyelocytic leukemia and the ability of RA to prevent cancer is currently under examination.