Osteoporosis in Childhood Cancer Survivors: Physiopathology, Prevention, Therapy and Future Perspectives.

The improvement of chemotherapy, radiotherapy, and surgical interventions, together with hematopoietic stem cell transplantation, increased childhood cancer survival rate in the last decades, reaching 80% in Europe. Nevertheless, anti-cancer treatments are mainly responsible for the onset of long-term side effects in childhood cancer survivors (CCS), including alterations of the endocrine system function and activity. In particular, the most frequent dysfunction in CCS is a metabolic bone disorder characterized by low bone mineral density (BMD) with increased skeletal fragility. BMD loss is also a consequence of a sedentary lifestyle, malnutrition, and cancer itself could affect BMD, thus inducing osteopenia and osteoporosis. In this paper, we provide an overview of possible causes of bone impairment in CCS in order to propose management strategies for early identification and treatment of skeletal fragility in this population.

Effect of CB2 Stimulation on Gene Expression in Pediatric B-Acute Lymphoblastic Leukemia: New Possible Targets.

Acute lymphoblastic leukemia type B (B-ALL) is the most common kind of pediatric leukemia, characterized by the clonal proliferation of type B lymphoid stem cells. Important progress in ALL treatments led to improvements in long-term survival; nevertheless, many adverse long-term consequences still concern the medical community. Molecular and cellular target therapies, together with immunotherapy, are promising strategies to overcome these concerns. Cannabinoids, enzymes involved in their metabolism, and cannabinoid receptors type 1 (CB1) and type 2 (CB2) constitute the endocannabinoid system, involved in inflammation, immune response, and cancer. CB2 receptor stimulation exerts anti-proliferative and anti-invasive effects in many tumors. In this study, we evaluated the effects of CB2 stimulation on B-ALL cell lines, SUP-B15, by RNA sequencing, Western blotting, and ELISA. We observe a lower expression of CB2 in SUP-B15 cells compared to lymphocytes from healthy subjects, hypothesizing its involvement in B-ALL pathogenesis. CB2 stimulation reduces the expression of CD9, SEC61G, TBX21, and TMSB4X genes involved in tumor growth and progression, and also negatively affects downstream intracellular pathways. Our findings suggest an antitumor role of CB2 stimulation in B-ALL, and highlight a functional correlation between CB2 receptors and specific anti-tumoral pathways, even though further investigations are needed.

Alteration of osteoclast activity in childhood cancer survivors: Role of iron and of CB2/TRPV1 receptors.

Childhood cancer survivors (CCS) are predisposed to the onset of osteoporosis (OP). It is known that iron overload induces osteoclasts (OCs) overactivity and that the iron chelator Deferasirox (DFX) can counteract it. The Cannabinoid Receptor type 2 (CB2) and the transient receptor potential vanilloid type-1 (TRPV1) are potential therapeutic targets for OP. In this study we isolated OCs from peripheral blood of 20 CCS and investigated osteoclast biomarkers expression and iron metabolism evaluating iron release by OCs and the expression of several molecules involved in its regulation. Moreover, we analyzed the effects of CB2 and TRPV1 stimulation in combination with DFX on osteoclast activity and iron metabolism. We observed, for the first time, an osteoclast hyperactivation in CCS suggesting a role for iron in its development. Moreover, we confirmed the well-known role of CB2 and TRPV1 receptors in bone metabolism, suggesting the receptors as possible key biomarkers of bone damage. Moreover, we demonstrated a promising synergism between pharmacological compounds, stimulating CB2 or inhibiting/desensitizing TRPV1 and DFX, in counteracting osteoclast overactivity in CCS to improve their quality of life.

Biological Aspects of Inflamm-Aging in Childhood Cancer Survivors.

Anti-cancer treatments improve survival in children with cancer. A total of 80% of children treated for childhood cancer achieve 5-year survival, becoming long-term survivors. However, they undergo several chronic late effects related to treatments. In childhood cancer survivors a chronic low-grade inflammation, known as inflamm-aging, is responsible for frailty, a condition characterized by vital organ failure and by premature aging processes. Inflamm-aging is closely related to chemotherapy and radiotherapy, which induce inflammation, accumulation of senescent cells, DNA mutations, and the production of reactive oxygen species. All these conditions are responsible for the onset of secondary diseases, such as osteoporosis, cardiovascular diseases, obesity, and infertility. Considering that the pathobiology of frailty among childhood cancer survivors is still unknown, investigations are needed to better understand frailty's biological and molecular processes and to identify inflamm-aging key biomarkers in order to facilitate the screening of comorbidities and to clarify whether treatments, normally used to modulate inflamm-aging, may be beneficial. This review offers an overview of the possible biological mechanisms involved in the development of inflamm-aging, focusing our attention on immune system alteration, oxidative stress, cellular senescence, and therapeutic strategies.

Osteosarcoma in Children: Not Only Chemotherapy.

Osteosarcoma (OS) is the most severe bone malignant tumor, responsible for altered osteoid deposition and with a high rate of metastasis. It is characterized by heterogeneity, chemoresistance and its interaction with bone microenvironment. The 5-year survival rate is about 67% for patients with localized OS, while it remains at 20% in case of metastases. The standard therapy for OS patients is represented by neoadjuvant chemotherapy, surgical resection, and adjuvant chemotherapy. The most used chemotherapy regimen for children is the combination of high-dose methotrexate, doxorubicin, and cisplatin. Considered that the necessary administration of high-dose chemotherapy is responsible for a lot of acute and chronic side effects, the identification of novel therapeutic strategies to ameliorate OS outcome and the patients' life expectancy is necessary. In this review we provide an overview on new possible innovative therapeutic strategies in OS.

Poikiloderma With Neutropenia and Mastocytosis: A Case Report and a Review of Dermatological Signs.

Poikiloderma with neutropenia (PN) is a very rare genetic disorder mainly characterized by poikiloderma and congenital neutropenia, which explains the recurrence of respiratory infections and risk of developing bronchiectasis. Patients are also prone to develop hematological and skin cancers. Here, we present the case of a patient, the only child of apparently unrelated Serbian parents, affected by PN resulting from the homozygous mutation NM_024598.3:c.243G>A (p.Trp81Ter) of USB1; early onset of poikiloderma (1 year of age) was associated with cutaneous mastocytosis. We also provide a review of the literature on this uncommon condition with a focus on dermatological findings.

Effects of Iron Chelation in Osteosarcoma.

BACKGROUND: Osteosarcoma is an aggressive bone tumor. It represents the principal cause of cancer-associated death in children. Considering the recent findings on the role of iron in cancer, iron chelation has been investigated for its antineoplastic properties in many tumors. Deferasirox is the most used iron chelator compound and in previous studies showed an anticancer effect in hematologic and solid malignancies. Eltrombopag is a Thrombopoietin receptor used in thrombocytopenia that also binds and mobilize iron. It demonstrated an effect on iron overload conditions and also in contrasting cancer cell proliferation. OBJECTIVE: We analyzed the effects of deferasirox and eltrombopag in human osteosarcoma cells in an attempt to identify other therapeutic approaches for this tumor. METHODS: We cultured and treated with deferasirox and Eltrombopag, alone and in combination, two human osteosarcoma cell lines, MG63 and 143B. After 72h exposure, we performed RTqPCR, Western Blotting, Iron Assay and cytofluorimetric assays to evaluate the effect on viability, apoptosis, cell cycle progression and ROS production. RESULTS: The iron-chelating properties of the two compounds are also confirmed in osteosarcoma, but we did not observe any direct effect on tumor progression. DISCUSSION: We tested deferasirox and eltrombopag, alone and in combination, in human osteosarcoma cells for the first time and demonstrated that their iron-chelating activity does not influence biochemical pathways related to cancer progression and maintenance. CONCLUSION: Although further investigations on possible effects mediated by cells of the tumor microenvironment could be of great interest, in vitro iron chelation in osteosarcoma does not impair tumor progression.

Safety of Anticancer Agents Used in Children: A Focus on Their Off-Label Use Through Data From the Spontaneous Reporting System.

BACKGROUND: Among factors influencing the higher risk of developing unknown or rare adverse drug reactions (ADRs) among children and adolescents, there is the frequent off-label use of drugs that seems to be very common in pediatric oncological patients. Our study aim to collect and evaluate data on the safety profile of antineoplastic drugs and their off-label use in the pediatrics population using real life data. METHODS: We retrieved Individual Case Safety Reports (ICSRs) with an anticancer agent as suspected drug among those reported through the Campania spontaneous reporting system from 1 January 2013 to 30 September 2019. We classified ICSRs into four off-label categories: "age," "route of administration," "weight," and "therapeutic indication." We defined an ICSR as an off-label case if it met at least one of the aforementioned categories for at least one of the reported suspected antineoplastic drugs. RESULTS: A total of 18 ICSRs (7.6%) out of 236 were classified as off-label cases. The median age of patients was 13 years (interquartile range, IQR: 6-16), with 94.4% of cases occurring in male patients. In the classification of the off-label category, 16 ICSRs were categorized according to the "therapeutic indication" and two for the "age." No case was categorized for the off-label categories "route of administration" and "weight." The two off-label cases categorized as "age" were both related to the use of brentuximab vedotin for Hodgkin's lymphoma in patients aged 16 years. Twenty-nine ADRs (1.6 suspected adverse drug reactions per ICSR) were identified among off-label cases. Among ADRs, those reported more than one were diarrhea (N = 3), neutropenia (N = 3), nausea (N = 2), pyrexia (N = 2), and vomit (N = 2). CONCLUSIONS: Our findings showed a low number of ICSRs classified as off-label. The majority of off-label ICSRs were categorized for the "therapeutic indication." This low number of off-label ICSRs might be largely due to the underreporting phenomenon, which is a major limit in pharmacovigilance. Therefore, we believe that spreading pharmacovigilance knowledge and awareness might improve this aspect.

Childhood Head and Neck Lymphadenopathy: A Report by a Single Institution (2003-2017).

Actually, there is still no consensus related to diagnostic and management algorithms in case of head and neck lymphadenopathy in children. The aim of our study was to analyze the causes of head and neck lymphadenopathy in children to determine a systematic diagnostic approach. We enrolled all cases of head and neck lymphadenopathy in children under the age of 18 diagnosed at the Unit of Hemato-Oncology, Pediatric Department of University "Luigi Vanvitelli," Naples, over a 15-year period (January 2003-December 2017). In total, 405 patients (271 males) were enrolled in the study. Thirteen cases due to other causes, were left off the study. Therefore, the study was performed on 392 cases. A total of 220 patients (56.1%) had a history of infection, 66 cases (16.8%) a diagnosis of neoplasia, and 101 (24.9%) cases a diagnosis of reactive inflammatory changes of nonspecific origin. We have observed the following from our study: (1) the acute infections are the most common causes of head and neck lymphadenopathy in the pediatric population; (2) in about a quarter of patients, the lymphadenopathy resulted by nonspecific origin; (3) the supraclavicular nodes should be regarded with a high index of suspicion of malignancy.

Bortezomib and endocannabinoid/endovanilloid system: a synergism in osteosarcoma.

Osteosarcoma is the most common primary malignant tumor of bone in children and adolescents. Bortezomib (BTZ) is an approved anticancer drug, classified as a selective reversible inhibitor of the ubiquitin-dependent proteasome system, that leads to cancer cell cycle arrest and apoptosis reducing the invasion ability of Osteosarcoma cells in vitro. It also regulates the RANK/RANKL/OPG system, involved in the pathogenesis of bone tumors and in cell migration. A side effect of BTZ is to induce painful sensory peripheral neuropathy which lead to cessation of therapy or dose reduction. Recently BTZ has been evaluated in combination with Cannabinoids targeting CB1 receptor, demonstrating a promising synergic effect. The Endocannabinoid/Endovanilloid (EC/EV) system includes two G protein-coupled receptors (CB1 and CB2), the Transient Potential Vanilloid 1 (TRPV1) channel and their endogenous ligands and enzymes. CB1 and CB2 are expressed mainly in Central Nervous System and Immune Peripheral cells respectively. TRPV1 is also expressed in primary sensory neurons and is involved in pain modulation. EC/EV system induces apoptosis, reduces invasion and cell proliferation in Osteosarcoma cell lines and is involved in bone metabolism. We analyzed the effects of BTZ, alone and in combination with selective agonists at CB2 (JWH-133) and TRPV1 (RTX) receptors, in the Osteosarcoma cell line (HOS) on Apoptosis, Cell Cycle progression, migration and bone balance. We observed that the stimulation of CB2 and TRPV1 receptors increase the efficacy of BTZ in inducing apoptosis and reducing invasion, cell cycle progression and by modulating bone balance. These data suggest the possibility to use BTZ, in combination with EC/EV agonists, in Osteosarcoma therapy reducing its dose and its side effects.

Anti-proliferative, pro-apoptotic and anti-invasive effect of EC/EV system in human osteosarcoma.

Osteosarcoma is the most common and aggressive bone tumor in children. The Endocannabinoid/Endovanilloid system has been proposed as anticancer target in tumor of different origins. This system is composed of two receptors (CB1 and CB2), the Transient Potential Vanilloid 1 (TRPV1) channel and their ligands and enzymes. CB1 is expressed mainly in central nervous system while CB2 predominantly on immune and peripheral cells. We investigated the effects of JWH-133 (CB2 agonist) and RTX (TRPV1 agonist) in six human Osteosarcoma cell lines: MG-63, U-2OS, MNNG/HOS, Saos-2, KHOS/NP, Hs888Lu, by Apoptosis and Migration-Assay. We also compared the effects of these compounds on Caspase-3, AKT, MMP-2 and Notch-1 regulation by Q-PCR and Western Blotting. We observed an anti-proliferative, pro-apoptotic, anti-invasive effect. Our results show that both CB2 stimulation and TRPV1 activation, in different Osteosarcoma cell lines, can act on the same pathways to obtain the same effect, indicating the Endocannabinoid/Endovanilloid system as a new therapeutic target in Osteosarcoma.

The Role of Mifamurtide in Chemotherapy-induced Osteoporosis of Children with Osteosarcoma.

BACKGROUND: Osteosarcoma is the most frequent malignant bone tumor in childhood and young adulthood. Long-term survivors of osteosarcoma patients show high prevalence of osteoporosis and fractures. The immunomodulatory mifamurtide, which modulates macrophages activity, improves disease outcome. OBJECTIVE: To evaluate the role of mifamurtide on macrophage component of bone, the osteoclasts, during chemotherapy in children with osteosarcoma. METHOD: Osteoclasts, obtained from peripheral blood cells of healthy donors were harvested in the presence or not of mifamurtide. Moreover, osteoclast cultures were obtained from osteosarcoma patients, at onset and during chemotherapy, alone or with mifamurtide. Pro-osteoporotic tartrateresistant acid phosphatase (TRAP), phosphokinase-ß-2 (PKCß2), vanilloid receptor type 1 (TRPV1), and anti-osteoporotic cannabinoid receptor type 2 (CB2) biomarkers were analyzed by bio-molecular (qPCR), biochemical (Western Blotting), and morphological (TRAP assay) approaches. RESULTS: Osteoclasts from osteosarcoma patients show significant increase of TRAP and decrease of CB2 with respect to osteoclasts from healthy donors. This osteoclast hyperactivity is more evident in osteoclasts from osteosarcoma patients during chemotherapy. Mifamurtide reduces pro-osteoporotic TRAP, PKCß2, TRPV1 levels and increases CB2 in osteoclasts from healthy donors. Moreover, chemotherapy-induced effects on bone resorption markers are fully reverted in osteoclasts derived from osteosarcoma patients in chemotherapy plus mifamurtide. CONCLUSION: Our data suggest a new therapeutic role for mifamurtide as possible anti-resorption agent in chemotherapy-induced osteoporosis in children with osteosarcoma.

Osteonecrosis as a complication in pediatric patients with acute lymphoblastic leukemia.

Osteonecrosis is a significant adverse effect of treatment administered to children suffering from acute lymphoblastic leukemia (ALL) that may have a negative effect on the quality of life. The purpose of this study is to evaluate the rate of secondary vascular osteonecrosis (ON) in a population of pediatric patients with ALL treated with corticosteroids and cytostatic agents. A retrospective analysis of prospectively collected data of the medical records of 328 patients with ALL identified 4 cases with ON, corresponding to 1.2% of all cases observed. Of the 4 patients identified in our study 3 were girls and 1 was a boy, aged from 10 to 16 years old (average age at diagnosis, 12 years). Median time between the diagnosis of ALL and ON was 12.5 months (range, 12 to 36 months). Regarding the lesion size of ON, in all cases the femoral head (monolateral in 1 case and bilateral in 3 cases) was involved and was associated with the scapula-humeral joint in one case. ON of the weight-bearing joints has been identified as a severe complication in children with leukemia that may be associated with the development of articular surface collapse, subsequent debilitating arthritis, sometimes needing arthroplasty. For this reason it is very important to implement prevention strategies, especially in adolescent girls treated with steroids and chemotherapy. An early diagnosis of ON and careful orthopedic follow-up are necessary in order to avoid bone deformations related to the late start or the wrong therapy.

Time trends of cancer incidence in childhood in Campania region: 25 years of observation.

BACKGROUND: Childhood cancer is relatively uncommon and the European age-standardized rate was 164 new case per million per year among children 0 to 14 years of age (95 % CI 158-170). Aims of our study are to evaluate the cases of these malignant diseases observed between 0 and 15 years of age in the Campania region between 1990 and 2014, the ration between observed and expected cases by disease and province of residence. Also we studied the percentage of extra-regional migration over the time by disease and province of residence. METHODS: In this study we reported the patients with malignant disease observed in 25 years (1990-2014) based on the specialized registry, the Mod. 1.01 of the AIEOP (Association Italian Pediatric Hematology-Oncology). The size of the monitored population also allowed us to systematically examine five time trends: 1990-94: 1995-99; 2000-04; 2005-09; and 2010-14. RESULTS: Between 1990 and 2014 a total of 3655 malignant neoplasms were reported: Napoli province (2059 cases), Salerno province (625), Caserta province (589), Avellino province (229), and Benevento province (153). Epidemiological data suggested that about 4100 cases could be expected in Campania region during the same period. The overall ratio between observed (O) and expected (E) numbers of cases in the five periods considered rose gradually from 0.69 in the first period to 0.76, then 0.82, 0.91, and 0.94, in the other periods considered. The extra-regional migration involved 1029 cases (28.1 %), showing a reduction from 33.7 % of the first period to 20.3 % of the last period considered. Considering single province of residence we observed the lowest rate of migration in Napoli and Caserta province, whereas higher levels were observed in the other provinces. For all provinces, except Salerno, the extra-regional migration declined significantly over time. CONCLUSIONS: The present findings showed an increase over time of O/E ratio, probably due to improvement in the organization of centers and greater trust of families in local centers. It is possible to further improve the efficiency of healthcare system of Campania region and migration can be reduced with a more rational use of hospitals throughout region.

High EZH2 expression is correlated to metastatic disease in pediatric soft tissue sarcomas.

BACKGROUND: Enhancer of Zeste Drosophila Homologue 2 (EZH2) is a key regulator of transcription as a member of polycomb repressive complex 2 (PRC2) which exerts repression of downstream genes and is correlated to invasiveness and progression of different tumours. Therefore, we evaluated the expression of PRC2 proteins in pediatric soft tissue sarcoma (rhabdomyosarcoma, RMS and extraosseous Ewing sarcoma, EES) correlating them to the clinical outcome of the patients. METHODS: We analyzed PRC2 protein expression by quantitative real time PCR, western blotting and immunohistochemistry in 17 soft tissue sarcomas (11 RMS and 6 EES) enrolled at Paediatric Oncology Units of the Second University of Naples. Expression analysis was performed for EZH2, SUZ12 and EED. RESULTS: Enhancer of Zeste Drosophila Homologue 2 was expressed with a different degree in 60 % of samples. Interestingly, the magnitude of EZH2 up regulation was significantly higher in patients presenting lymph node and/or distant metastases at the diagnosis. Moreover, patients overexpressing EZH2 had a lower probability of survival compared to patients negative or with low EZH2 expression. CONCLUSIONS: Our study suggests that high EZH2 expression is associated to increased aggressiveness of the disease. Therefore, drugs that control its activity could be potentially used in the epigenetic target treatment of tumors with these alterations.

Unusual association of non-anaplastic Wilms tumor and Cornelia de Lange syndrome: case report.

BACKGROUND: Cornelia de Lange syndrome is the prototype for cohesinopathy disorders, which are characterized by defects in chromosome segregation. Kidney malformations, including nephrogenic rests, are common in Cornelia de Lange syndrome. Only one post-mortem case report has described an association between Wilms tumor and Cornelia de Lange syndrome. Here, we describe the first case of a living child with both diseases. CASE PRESENTATION: Non-anaplastic triphasic nephroblastoma was diagnosed in a patient carrying a not yet reported mutation in NIPBL (c.4920 G > A). The patient had the typical facial appearance and intellectual disability associated with Cornelia de Lange syndrome in absence of limb involvement. The child's kidneys were examined by ultrasound at 2 years of age to exclude kidney abnormalities associated with the syndrome. She underwent pre-operative chemotherapy and nephrectomy. Seven months later she was healthy and without residual detectable disease. CONCLUSION: The previous report of such co-occurrence, together with our report and previous reports of nephrogenic rests, led us to wonder if there may be any causal relationship between these two rare entities. The wingless/integrated (Wnt) pathway, which is implicated in kidney development, is constitutively activated in approximately 15-20 % of all non-anaplastic Wilms tumors. Interestingly, the Wnt pathway was recently found to be perturbed in a zebrafish model of Cornelia de Lange syndrome. Mutations in cohesin complex genes and regulators have also been identified in several types of cancers. On the other hand, there is no clear evidence of an increased risk of cancer in Cornelia de Lange syndrome, and no other similar cases have been published since the fist one reported by Cohen, and this prompts to think Wilms tumor and Cornelia de Lange syndrome occurred together in our patient by chance.

Influence of methylenetetrahydrofolate reductase gene polymorphisms on the outcome of pediatric patients with non-Hodgkin lymphoma treated with high-dose methotrexate.

High-dose methotrexate (MTX) is a key component of most treatment protocols for childhood and adolescent non-Hodgkin lymphoma (NHL). Recent studies have suggested that the toxicity of antifolate drugs, such as MTX, is affected by inherited single nucleotide polymorphisms (SNPs) in folate metabolizing genes. The aim of our study was to investigate the potential influence of the C677T and A1298C genetic variants of the methylenetetrahydrofolate reductase (MTHFR) gene on the clinical toxicity and efficacy of MTX in pediatric patients with NHL (n = 95) treated with therapeutic protocols Associazione Italiana Ematologia Oncologia Pediatrica (AIEOP) LNH-97 and EURO LB-02. We demonstrated that patients with the 677T genotype had an approximately six-fold greater risk of developing hematological toxicity compared with wild-type carriers, especially in the 1 g/m(2) treatment group (p = 0.01). Moreover, we identified a correlation between the risk of relapse and the T genotype: T carriers had reduced disease-free survival compared with wild-type patients (67% vs. 100%). Our data suggest a pharmacogenetic influence on the adverse effects of high-dose MTX in the 1 g/m(2) treatment group.

Kaposiform hemangioendothelioma of the kidney: an unusual presentation of a rare vascular neoplasm.

Kaposiform hemangioendothelioma (KHE) is a rare, locally aggressive, vascular spindle-cell proliferation, with resemblance to Kaposi sarcoma. Usually, this tumor occurs in the skin and the retroperitoneum. We described a girl with a kidney localization and extension into the inferior vena cava and even into the right atrium. The case presented here is unique in 2 ways. First, kidney involvement of KHE has never been described in the literature until now. Second, and most remarkably, extensive tumor thrombosis suggests surgical excision even with cardiopulmonary bypass. The KHE of the kidney is a rare tumor but should be taken into account in the differential diagnosis with other pediatric renal neoplasms.

Beta-spectrinBari: a truncated beta-chain responsible for dominant hereditary spherocytosis.

We describe a beta-spectrin variant, named beta-spectrin Bari, characterized by a truncated chain and associated with hereditary spherocytosis. The clinical phenotype consists of a moderately severe hemolytic anemia, splenomegaly, and spherocytes and acanthocytes in the blood smear. The occurrence of the truncated protein, that represents about 8% of the total beta-spectrin occurring on the membrane, results in a marked spectrin deficiency. The altered protein is due to a single point mutation at position -2 (A->G) of the acceptor splice site of intron 16 leading to an aberrant beta-spectrin message skipping exons 16 and 17 indistinguishable from that reported for beta-spectrin Winston-Salem. We provide evidence that the mutated gene is transcribed but its mRNA is less abundant than either its normal counterpart or beta-spectrin Winston-Salem mRNA. Our findings are an example of how mutations in different splice sites, although causing the same truncating effect, result in clearly different clinical pictures.

Vitamin A and infancy. Biochemical, functional, and clinical aspects.

Vitamin A is a very intriguing natural compound. The molecule not only has a complex array of physiological functions, but also represents the precursor of promising and powerful new pharmacological agents. Although several aspects of human retinol metabolism, including absorption and tissue delivery, have been clarified, the type and amounts of vitamin A derivatives that are intracellularly produced remain quite elusive. In addition, their precise function and targets still need to be identified. Retinoic acids, undoubtedly, play a major role in explaining activities of retinol, but, recently, a large number of physiological functions have been attributed to different retinoids and to vitamin A itself. One of the primary roles this vitamin plays is in embryogenesis. Almost all steps in organogenesis are controlled by retinoic acids, thus suggesting that retinol is necessary for proper development of embryonic tissues. These considerations point to the dramatic importance of a sufficient intake of vitamin A and explain the consequences if intake of retinol is deficient. However, hypervitaminosis A also has a number of remarkable negative consequences, which, in same cases, could be fatal. Thus, the use of large doses of retinol in the treatment of some human diseases and the use of megavitamin therapy for certain chronic disorders as well as the growing tendency toward vitamin faddism should alert physicians to the possibility of vitamin overdose.