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The extended human major histocompatibility complex (MHC) is a gene-rich region of about 7.6 Mb on chromosome 6, and includes a high proportion of genes involved in the immune response. Among these are the two Human Leukocyte Antigen (HLA) gene clusters, class I and class II, which encode highly polymorphic classical HLA-A, B, C and HLA-DR, DQ and DP genes, respectively. The protein products of the classical HLA genes are heterodimeric cell surface molecules that bind short peptides derived from non-self and self proteins, including infections and auto-antigens. The presentation of these HLA-anchored peptides to T lymphocytes triggers a cascade of responses in immune-associated genes that leads to adaptive immunity. Associations between HLA class II alleles and childhood leukemia have been reported in a number of studies. This could be due to the role of HLA allele-restricted peptide binding and T cell activation, or linkage disequilibrium to an MHC-linked "leukemia gene" in the pathogenesis of childhood leukemia. Efforts are currently in progress to resolve these questions, using large leukemia case-control sample series such as the UK Childhood Cancer Study (UKCCS) and the Northern California Childhood Leukemia Study (NCCLS). Here we review the background to these studies, and present a novel hypothesis based on the paradigm of HLA-associated auto-immune disease that might explain an infection-based etiology of childhood leukemia.
Blood Cells Mol Dis
PMID:The human major histocompatibility complex and childhood leukemia: an etiological hypothesis based on molecular mimicry. 1905

The United Kingdom Childhood Cancer Study (UKCCS) was specifically designed to investigate the potential etiological role of infections as one of its objectives and information on a number of markers of infectious exposure from multiple sources was collected (www.ukccs.org). This study found that a mother's recollections of past minor illness episodes in her children were unreliable, producing systematic case-control differences. From birth onwards children diagnosed with ALL between 2-5 years were found to have had more clinically diagnosed infectious illness episodes (not fewer) than unaffected children, with those with two or more neonatal infections being diagnosed with leukaemia around 7 months earlier than those with only one or none. The findings from these analyses and their implications for future research are reviewed and discussed in this paper.
Blood Cells Mol Dis
PMID:Infectious proxies and childhood leukaemia: findings from the United Kingdom Childhood Cancer Study (UKCCS). 1909 6

S-adenosylmethionine decarboxylase (AdoMetDC) is an essential enzyme of polyamine (PA) biosynthesis, and both AdoMetDC and PA levels are often up-regulated in cancer cells. The second-generation inhibitor SAM486A inhibits AdoMetDC enzyme activity and has been evaluated in phase II clinical cancer trials. However, little is known about the mechanism of action and potential use of this therapeutic drug in the treatment of the pediatric cancer neuroblastoma (NB). Here, we show that p53 wild-type NB cells are highly sensitive to SAM486A treatment. Most notably, SAM486A treatment resulted in the rapid accumulation of proapoptotic proteins p53 and Mdm2. Concomitant with the increase of proteins at endogenous levels, the in vivo phosphorylation of p53 at residues Ser(46)/Ser(392) and Mdm2 at residue Ser(166) was observed. Moreover, the antiapoptotic protein Akt/protein kinase B was down-regulated and also dephosphorylated at residue Ser(473) in a dose- and time-dependent manner and NB cells entered apoptotic cell death. The results presented in this study highlight the importance of PA homeostasis and provide a direct link between PA metabolism and apoptotic cell signaling pathways in p53 wild-type NB cells. PA inhibitors such as SAM486A may be effective alternative agents for the treatment of NBs with or without MYCN amplification.
Mol Cancer Ther 2009 Jul
PMID:Inhibition of S-adenosylmethionine decarboxylase by inhibitor SAM486A connects polyamine metabolism with p53-Mdm2-Akt/protein kinase B regulation and apoptosis in neuroblastoma. 1958 41

Cancer chemotherapy has been recognized as one severe risk factor that influences bone growth and bone mass accumulation during childhood and adolescence. This article reviews on the importance of this clinical issue, current understanding of the underlying mechanisms for the skeletal defects and potential preventative strategies. Both clinical and basic studies that appeared from 1990 to 2010 were reviewed for bone defects (growth arrest, bone loss, osteonecrosis, and/or fractures) caused by paediatric cancer chemotherapy. As chemotherapy has become more intensive and achieved greater success in treating paediatric malignancies, skeletal complications such as bone growth arrest, low bone mass, osteonecrosis, and fractures during and/or after chemotherapy have become a problem for some cancer patients and survivors particularly those that have received high dose glucocorticoids and methotrexate. While chemotherapy-induced skeletal defects are likely multi-factorial, recent studies suggest that different chemotherapeutic agents can directly impair the activity of the growth plate and metaphysis (the two major components of the bone growth unit) through different mechanisms, and can alter bone modeling/remodeling processes via their actions on bone formation cells (osteoblasts), bone resorption cells (osteoclasts) and bone "maintenance" cells (osteocytes). Intensive use of multi-agent chemotherapy can cause growth arrest, low bone mass, fractures, and/or osteonecrosis in some paediatric patients. While there are currently no specific strategies for protecting bone growth during childhood cancer chemotherapy, regular BMD monitoring and exercise are have been recommended, and possible adjuvant treatments could include calcium/vitamin D, antioxidants, bisphosphonates, resveratrol, and/or folinic acid.
Curr Mol Med 2011 Mar
PMID:Pathobiology and prevention of cancer chemotherapy-induced bone growth arrest, bone loss, and osteonecrosis. 2134 29

Budding uninhibited by benzimidazole-related 1 (BUBR1) is a central molecule of the spindle assembly checkpoint. Germline mutations in the budding uninhibited by benzimidazoles 1 homolog beta gene encoding BUBR1 cause premature chromatid separation (mosaic variegated aneuploidy) [PCS (MVA)] syndrome, which is characterized by constitutional aneuploidy and a high risk of childhood cancer. Patients with the syndrome often develop Dandy-Walker complex and polycystic kidneys; implying a critical role of BUBR1 in morphogenesis. However, little is known about the function of BUBR1 other than mitotic control. Here, we report that BUBR1 is essential for the primary cilium formation, and that the PCS (MVA) syndrome is thus a novel ciliopathy. Morpholino knockdown of bubr1 in medaka fish also caused ciliary dysfunction characterized by defects in cerebellar development and perturbed left-right asymmetry of the embryo. Biochemical analyses demonstrated that BUBR1 is required for ubiquitin-mediated proteasomal degradation of cell division cycle protein 20 in the G0 phase and maintains anaphase-promoting complex/cyclosome-CDC20 homolog 1 activity that regulates the optimal level of dishevelled for ciliogenesis.
Hum Mol Genet 2011 May 15
PMID:Insufficiency of BUBR1, a mitotic spindle checkpoint regulator, causes impaired ciliogenesis in vertebrates. 2138 84

Neuroblastoma is a stroma-poor (SP) aggressive pediatric cancer belonging to neuroblastic tumors, also including ganglioneuroblastoma and ganglioneuroma, two stroma-rich (SR) less aggressive tumors. Our previous gene-expression profiling analysis showed a different CXCL13 mRNA expression between SP and SR tumors. Therefore, we studied 13 SP and 13 SR tumors by reverse transcription quantitative real-time PCR (RT-qPCR) and we found that CXCR5b was more expressed in SP than in SR and CXCL13 was predominantly expressed in SR tumors. Then, we isolated neuroblastic and Schwannian stromal cells by laser capture microdissection and we found that malignant neuroblasts express CXCR5b mRNA, whereas Schwannian stromal cells express CXCL13. Immunohistochemistry confirmed that stroma expresses CXCL13 but not CXCR5. To better understand the role of CXCL13 and CXCR5 in neuroblastic tumors we studied 11 neuroblastoma cell lines and we detected a heterogeneous expression of CXCL13 and CXCR5b. Interestingly, we found that only CXCR5b splice variant was expressed in both tumors and neuroblastoma lines, whereas CXCR5a was never detected. Moreover, we found that neuroblastoma cells expressing CXCR5 receptor migrate toward a source of recombinant CXCL13. Lastly, neuroblastoma cells induced to glial cell differentiation expressed CXCL13 mRNA and protein. The chemokine released in the culture medium was able to stimulate chemotaxis of LA1-5S neuroblastoma cells. Collectively, our data suggest that CXCL13 produced by stromal cells may contribute to the generation of an environment in which the malignant neuroblasts are retained, thus limiting the possible development of metastases in patients with SR tumor.
Mol Cancer Res 2011 Jul
PMID:Role of CXCL13-CXCR5 crosstalk between malignant neuroblastoma cells and Schwannian stromal cells in neuroblastic tumors. 2164 90

Ewing's sarcoma is a pediatric cancer of the bone that is characterized by the expression of the chimeric transcription factor EWS-FLI1 that confers a highly malignant phenotype and results from the chromosomal translocation t(11;22)(q24;q12). Poor overall survival and pronounced long-term side effects associated with traditional chemotherapy necessitate the development of novel, targeted, therapeutic strategies. We therefore conducted a focused viability screen with 200 small molecule kinase inhibitors in 2 different Ewing's sarcoma cell lines. This resulted in the identification of several potential molecular intervention points. Most notably, tozasertib (VX-680, MK-0457) displayed unique nanomolar efficacy, which extended to other cell lines, but was specific for Ewing's sarcoma. Furthermore, tozasertib showed strong synergies with the chemotherapeutic drugs etoposide and doxorubicin, the current standard agents for Ewing's sarcoma. To identify the relevant targets underlying the specific vulnerability toward tozasertib, we determined its cellular target profile by chemical proteomics. We identified 20 known and unknown serine/threonine and tyrosine protein kinase targets. Additional target deconvolution and functional validation by RNAi showed simultaneous inhibition of Aurora kinases A and B to be responsible for the observed tozasertib sensitivity, thereby revealing a new mechanism for targeting Ewing's sarcoma. We further corroborated our cellular observations with xenograft mouse models. In summary, the multilayered chemical biology approach presented here identified a specific vulnerability of Ewing's sarcoma to concomitant inhibition of Aurora kinases A and B by tozasertib and danusertib, which has the potential to become a new therapeutic option.
Mol Cancer Ther 2011 Oct
PMID:An integrated chemical biology approach identifies specific vulnerability of Ewing's sarcoma to combined inhibition of Aurora kinases A and B. 2176 30

The development of a sensitive, specific, and non-invasive approach for cancer detection will facilitate early detection and, hence, improve the outcome of individuals with known cancer predispositions. Proteomic profiling of blood emerges to be a logical choice of such non-invasive or minimal invasive detection. However, plasma biomarker discovery of pediatric cancers lags behind that of adult cancers, suggesting more efforts are needed in this area. In this study, we used surface-enhanced laser desorption/ionization-time of flight mass spectrometry to profile plasma proteome in osteosarcoma patients. Osteosarcoma is a bone cancer that affects many children and young adults. We have shown that the plasma proteome contains a unique cancer signature that can distinguish patients with osteosarcoma from those with a benign bone disease. To improve cancer biomarker discovery in plasma, we have also shown that depletion of two highly abundant plasma proteins increases the detection sensitivity of lower-abundance proteins. The combination of depletion and proteomic profiling may increase the chance of identifying tumor-derived proteins within the plasma of pediatric cancer patients.
Methods Mol Biol 2012
PMID:Plasma proteomic profiling of pediatric osteosarcoma. 2208 17

Styrene-acrylonitrile Trimer (SAN Trimer), a by-product in production of acrylonitrile styrene plastics, was identified at a Superfund site in Dover Township, NJ, where childhood cancer incidence rates were elevated for a period of several years. SAN Trimer was therefore tested by the National Toxicology Program in a 2-year perinatal carcinogenicity study in F344/N rats and a bacterial mutagenicity assay; both studies gave negative results. To further characterize its genotoxicity, SAN Trimer was subsequently evaluated in a combined micronucleus (MN)/Comet assay in juvenile male and female F344 rats. SAN Trimer (37.5, 75, 150, or 300 mg/kg/day) was administered by gavage once daily for 4 days. Micronucleated reticulocyte (MN-RET) frequencies in blood were determined by flow cytometry, and DNA damage in blood, liver, and brain cells was assessed using the Comet assay. Highly significant dose-related increases (P < 0.0001) in MN-RET were measured in both male and female rats administered SAN Trimer. The RET population was reduced in high dose male rats, suggesting chemical-related bone marrow toxicity. Results of the Comet assay showed significant, dose-related increases in DNA damage in brain cells of male (P < 0.0074) and female (P < 0.0001) rats; increased levels of DNA damage were also measured in liver cells and leukocytes of treated rats. Chemical-related cytotoxicity was not indicated in any of the tissues examined for DNA damage. The results of this subacute MN/Comet assay indicate induction of significant genetic damage in multiple tissues of weanling F344 male and female rats after oral exposure to SAN Trimer.
Environ Mol Mutagen 2012 Apr
PMID:Genotoxicity of styrene-acrylonitrile trimer in brain, liver, and blood cells of weanling F344 rats. 2235 Nov 8

Ewing sarcoma is an aggressive pediatric cancer of the bone and soft tissue, in which patients whose tumors have a poor histologic response to initial chemotherapy have a poor overall prognosis. Therefore, it is important to identify molecules involved in resistance to chemotherapy. Herein, we show that the DNA repair protein and transcriptional cofactor, EYA3, is highly expressed in Ewing sarcoma tumor samples and cell lines compared with mesenchymal stem cells, the presumed cell-of-origin of Ewing sarcoma, and that it is regulated by the EWS/FLI1 fusion protein transcription factor. We further show that EWS/FLI1 mediates upregulation of EYA3 via repression of miR-708, a miRNA that targets the EYA3 3'-untranslated region, rather than by binding the EYA3 promoter directly. Importantly, we show that high levels of EYA3 significantly correlate with low levels of miR-708 in Ewing sarcoma samples, suggesting that this miR-mediated mechanism of EYA3 regulation holds true in human cancers. Because EYA proteins are important for cell survival during development, we examine, and show, that loss of EYA3 decreases survival of Ewing sarcoma cells. Most importantly, knockdown of EYA3 in Ewing sarcoma cells leads to sensitization to DNA-damaging chemotherapeutics used in the treatment of Ewing sarcoma, and as expected, after chemotherapeutic treatment, EYA3 knockdown cells repair DNA damage less effectively than their control counterparts. These studies identify EYA3 as a novel mediator of chemoresistance in Ewing sarcoma and define the molecular mechanisms of both EYA3 overexpression and of EYA3-mediated chemoresistance.
Mol Cancer Res 2012 Aug
PMID:EWS/FLI1 regulates EYA3 in Ewing sarcoma via modulation of miRNA-708, resulting in increased cell survival and chemoresistance. 2272 8


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