Medulloblastoma Cell Lines D283 Research Articles

Abstract 2080: Role of differentially expressed micro RNAs in non-WNT, non-SHH medulloblastoma

Abstract Medulloblastoma is a common malignant brain tumor in children. It has four distinct molecular subgroups namely WNT, SHH, Group 3 and Group 4. The molecular subgroups differ in their clinical characteristics including age, incidence of metastasis and survival. Group 3 and Group 4 medulloblastomas have overlapping gene expression profile but are distinct in their clinical behavior. Group 3 medulloblastomas have the worst overall survival rates whereas Group 4 medulloblastomas have intermediate survival. Group 3 and Group 4 tumors are not associated with any known signaling pathway and due to their overlapping expression profiles it is often difficult to accurately identify the subgroup, which is very crucial for the appropriate treatment design. MiR-592, located in the intronic region of GRM8 gene, is over expressed in Group 4 medulloblastoma along with its host gene, thus acting as a good marker for Group 4 tumors. MiR-204, on the other hand is expressed from the 6th intron of TRPM3 gene and expressed in some Group 3 and majority of Group 4 medulloblastomas. In order to delineate the role of miR-592 and miR-204 in medulloblastoma biology, effect of expression of these microRNAs on medulloblastoma cell growth and behavior were investigated. The micro RNAs were expressed in a lentiviral mediated inducible manner in Group 3 medulloblastoma cell lines D283, D425 and D341 and their effects on cell proliferation, anchorage-independent growth and invasion potential were studied. MiR-592 expression had marginal effects on the anchorage independent growth potential and the tumorigenic potential of the Group 3 cell line where as miR-204 expression led to significant decrease in the anchorage independent growth, tumorigenic potential, as well as invasion potential of the medulloblastoma cell lines. Further in order to decipher the molecular mechanisms underlying these micro RNA mediated effects, RNA-sequencing analysis of miR-592 and miR-204 expressing medulloblastoma cells were performed to identify genes that are differentially expressed upon micro RNA expression. The results helped us to identify the molecular pathways that are being affected by the micro RNA expression and how they affect the malignant behavior of medulloblastoma cells. Citation Format: Raikamal Paul, Rakesh Jalali, Epari Sridhar, Aliasagar Moiyadi, Neelam Shirsat. Role of differentially expressed micro RNAs in non-WNT, non-SHH medulloblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2080.

Ecto-5'-Nucleotidase Overexpression Reduces Tumor Growth in a Xenograph Medulloblastoma Model.

BackgroundEcto-5’-nucleotidase/CD73 (ecto-5’-NT) participates in extracellular ATP catabolism by converting adenosine monophosphate (AMP) into adenosine. This enzyme affects the progression and invasiveness of different tumors. Furthermore, the expression of ecto-5’-NT has also been suggested as a favorable prognostic marker, attributing to this enzyme contradictory functions in cancer. Medulloblastoma (MB) is the most common brain tumor of the cerebellum and affects mainly children.Materials and MethodsThe effects of ecto-5’-NT overexpression on human MB tumor growth were studied in an in vivo model. Balb/c immunodeficient (nude) 6 to 14-week-old mice were used for dorsal subcutaneous xenograph tumor implant. Tumor development was evaluated by pathophysiological analysis. In addition, the expression patterns of adenosine receptors were verified.ResultsThe human MB cell line D283, transfected with ecto-5’-NT (D283hCD73), revealed reduced tumor growth compared to the original cell line transfected with an empty vector. D283hCD73 generated tumors with a reduced proliferative index, lower vascularization, the presence of differentiated cells and increased active caspase-3 expression. Prominent A1 adenosine receptor expression rates were detected in MB cells overexpressing ecto-5’-NT.ConclusionThis work suggests that ecto-5’-NT promotes reduced tumor growth to reduce cell proliferation and vascularization, promote higher differentiation rates and initiate apoptosis, supposedly by accumulating adenosine, which then acts through A1 adenosine receptors. Therefore, ecto-5’-NT might be considered an important prognostic marker, being associated with good prognosis and used as a potential target for therapy.

Abstract 2499: The significance of Wip1 in neuroblastoma and medulloblastoma

Abstract Background: The most common cytogenetic lesions in the embryonal neural tumors medulloblastoma (MB) and neuroblastoma (NB) affect chromosome 17, with 17q+ or isochromosome 17q, in approximately one-third of MB with these aberrations being a significant indicator of poor clinical outcome. Similarly, in NB 17q+ is the most powerful genetic predictor of adverse clinical outcome. We found aberrations of chromosome 17 in 85% in a national study of NB (PNAS 2010) with 17q+ in 46% and whole 17 gain in 39%. In both MB and NB gain of wild-type p53-induced phosphatase 1 (Wip1) at 17q23 is frequently detected. Wip1 is a serine/threonine phosphatase of the type 2C protein phosphatase family (PP2C). The type 2C phosphatases are linked to the regulation of cellular stress responses. Methods: Comparative genomic hybridization (CGH) with the Affymetrix250k SNP array was used to analyze primary NB and MB and a large set of cell lines. Cell lines from MB, NB and breast cancers were examined for Wip1 expression using western blotting, immunohistochemistry and Real-Time quantitative PCR (Q-PCR). Stable transfections of Wip1 silenced cell lines were generated by shRNA specific for Wip1 and puromycin selection. The phosphorylation of histone H2AX and clonogenicity of Wip1 knockdown were examined in cell lines using flow cytometry and clonogenic assay, respectively. Results: Detailed CGH analysis revealed that Wip1 is present in at least one extra genomic copy in all 54 tumor samples containing 17q gain. Results from our large set of MB and NB cell lines demonstrate 17q aberrations with more complex patterns in MB corroborating previous results in clinical tumors. These findings have been confirmed by analyzing the expression pattern of Wip1 using different immunostaining techniques. Moreover, mRNA levels of Wip1 correlate to Wip1 protein expression. Transfection experiments with shRNA against Wip1 showed substantial decrease in cell viability in MEB-MED8A, D283 MED, D324 MED and SK-N-BE(2) cell lines. MED-MED8A and SK-N-BE(2) showed a significant decrease in cell growth and colony formation. The MB cell lines D283 MED and D324 MED but not MEB-MED8A showed a substantial increase of gamma-H2AX expression after Wip1 knockdown compared to the non-silencing transfections. Conclusions: Our study indicates an important oncogenic role of Wip1 in NB and MB. Our results showed that Wip1 is present in at least one extra genomic copy in the majority of primary NB and MB. We identified NB and MB cell lines expressing high, moderate and low levels of Wip1 where Wip1 knocked cell lines exhibited decreased cell growth and clonogenic capacity compared to non-silenced cells. Moreover, knockdown of Wip1 induced phosphorylation of histone H2AX in NB and MB cell lines indicating a significant role of Wip1 in the DNA damage response of these tumors. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2499. doi:1538-7445.AM2012-2499

Differential expression and cellular distribution of γ‐tubulin and βIII‐tubulin in medulloblastomas and human medulloblastoma cell lines

In previous studies, we have shown overexpression and ectopic subcellular distribution of gamma-tubulin and betaIII-tubulin in human glioblastomas and glioblastoma cell lines (Katsetos et al., 2006, J Neuropathol Exp Neurol 65:455-467; Katsetos et al., 2007, Neurochem Res 32:1387-1398). Here we determined the expression of gamma-tubulin in surgically excised medulloblastomas (n = 20) and in the human medulloblastoma cell lines D283 Med and DAOY. In clinical tissue samples, the immunohistochemical distribution of gamma-tubulin labeling was pervasive and inversely related to neuritogenesis. Overexpression of gamma-tubulin was widespread in poorly differentiated, proliferating tumor cells but was significantly diminished in quiescent differentiating tumor cells undergoing neuritogenesis, highlighted by betaIII-tubulin immunolabeling. By quantitative real-time PCR, gamma-tubulin transcripts for TUBG1, TUBG2, and TUBB3 genes were detected in both cell lines but expression was less prominent when compared with the human glioblastoma cell lines. Immunoblotting revealed comparable amounts of gamma-tubulin and betaIII-tubulin in different phases of cell cycle; however, a larger amount of gamma-tubulin was detected in D283 Med when compared with DAOY cells. Interphase D283 Med cells exhibited predominantly diffuse cytoplasmic gamma-tubulin localization, in addition to the expected centrosome-associated distribution. Robust betaIII-tubulin immunoreactivity was detected in mitotic spindles of DAOY cells. Our data indicate that overexpression of gamma-tubulin may be linked to phenotypic dedifferentiation (anaplasia) and tumor progression in medulloblastomas and may potentially serve as a promising tumor marker.

Dickkopf-1 is an epigenetically silenced candidate tumor suppressor gene in medulloblastoma1

Medulloblastoma is a heterogeneous pediatric brain tumor with significant therapy-related morbidity, its five-year survival rates ranging from 30% to 70%. Improvement in diagnosis and therapy requires better understanding of medulloblastoma pathology. We used whole-genome microarray analysis to identify putative tumor suppressor genes silenced by epigenetic mechanisms in medulloblastoma. This analysis yielded 714 up-regulated genes in immortalized medulloblastoma cell line D283 on treatment with histone deacetylase (HDAC) inhibitor trichostatin A (TSA). Dickkopf-1 (DKK1), a Wnt antagonist, was found to be up-regulated on HDAC inhibition. We examined DKK1 expression in primary medulloblastoma cells and patient samples by reverse transcriptase PCR and found it to be significantly down-regulated relative to normal cerebellum. Transfection of a DKK1 gene construct into D283 cell lines suppressed medulloblastoma tumor growth in colony focus assays by 60% (P < 0.001). In addition, adenoviral vector-mediated expression of DKK1 in medulloblastoma cells increased apoptosis fourfold (P < 0.001). These data reveal that inappropriate histone modifications might deregulate DKK1 expression in medulloblastoma tumorigenesis and block its tumor-suppressive activity.

Multiple DNA repair mechanisms and alkylator resistance in the human medulloblastoma cell line D-283 Med (4-HCR).

We have previously reported preferential repair of DNA interstrand crosslinks in the 4-hydroperoxycyclophosphamide-resistant human medulloblastoma cell line D-283 Med (4-HCR). We now report further studies that explored the potential mechanisms underlying this repair. Limiting dilution assays and Western, Southern, and Northern blots were used to compare specific differences between D-283 Med (4-HCR) and its parental line D-283 Med. D-283 Med (4-HCR) was cross-resistant to melphalan and 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), with O6-alkylguanine-DNA alkyltransferase (AGT) levels of 466+/-164 fmol/mg protein; AGT levels in the parental line, D-283 Med, were 76+/-96 fmol/mg. The increase in AGT activity was not a result of gene amplification. Depleting AGT with O6-benzylguanine partially restored sensitivity to BCNU. Both cell lines were deficient in the human mismatch protein MutLalpha. ERCC4 mRNA and poly(ADP-ribose) polymerase levels were similar in both cell lines, and ERCC1 mRNA levels were 2- to 2.5-fold lower in D-283 Med (4-HCR). Topoisomerase I levels were 2- to 2.5-fold higher in D-283 Med compared with D-283 Med (4-HCR). These results, while illustrating the multiple differences between D-283 Med and D-283 Med (4-HCR), do not explain the enhanced DNA interstrand crosslink repair seen in D-283 Med (4-HCR).

Modulation of cyclophosphamide activity by O6-alkylguanine-DNA alkyltransferase.

The human medulloblastoma cell line D283 Med (4-HCR), a line resistant to 4-hydroperoxycyclophosphamide (4-HC), displays enhanced repair of DNA interstrand crosslinks induced by phosphoramide mustard. D283 Med (4-HCR) cells are cross-resistant to 1,3-bis(2-chloroethyl)- -nitrosourea, but partial sensitivity is restored after elevated levels of O6-alkylguanine-DNA alkyltransferase (AGT) are depleted by O6-benzylguanine (O6-BG). Studies were conducted to define the activity of 4-HC and 4-hydroperoxydidechlorocyclophosphamide against D283 Med (4-HCR) after AGT is depleted by O6-BG. Limiting dilution and xenograft studies were conducted to define the activity of 4-HC and 4-hydroperoxydidechlorocyclophosphamide with or without O6-BG. The activity of 4-HC and 4-hydroperoxydidechlorocyclophosphamide against D283 Med (4-HCR) was increased after AGT depletion by O6-BG preincubation. Similar studies with Chinese hamster ovary cells, with or without stable transfection with a plasmid expressing the human AGT protein, revealed that the AGT-expressing cells were significantly less sensitive to 4-HC and 4-hydroperoxydidechlorocyclophosphamide. Reaction of DNA with 4-HC, phosphoramide mustard, or acrolein revealed that only 4-HC and acrolein caused a decrease in AGT levels. We propose that a small but potentially significant part of the cellular toxicity of cyclophosphamide in these cells is due to acrolein, and that this toxicity is abrogated by removal of the acrolein adduct from DNA by AGT.

Retinoic acid regulates the expression of the calcium binding protein, calbindin-D28K.

It is a well established fact that the calcium-binding protein, calbindin-D28k, is influenced by vitamin D in intestine and kidney. However, very little is known concerning the regulation of calbindin-D28k in brain. Although few genes that are regulated by retinoic acid (RA) have been identified in the nervous system, we now report that the human medulloblastoma cell line D283 (which is derived from cerebellum and has a distinctly neuronal phenotype) contains calbindin-D28k endogenously and that calbindin protein and mRNA can be induced 10- to 15-fold in these cells by 10(-7) M RA. These findings are the first evidence of RA-mediated regulation of calbindin. The time course of response, as determined by Northern blot analysis, indicated that the first significant increase in calbindin-D28k mRNA is at 12 h with a plateau of calbindin mRNA induction at 72 h after RA treatment. The induction of calbindin mRNA by RA was preceded by an induction of retinoic acid receptor-alpha mRNA and was accompanied by an induction of retinoid X receptor-alpha mRNA. Calbindin-D28k mRNA levels in D283 medulloblastoma cells as well as the induction of calbindin mRNA by RA were not significantly affected by 1,25-dihydroxyvitamin D3 treatment. Deletion mutant analysis of the native calbindin-D28k promoter and cotransfection of CV-1 or D283 medulloblastoma cells in the presence of retinoic acid receptor-alpha and/or retinoid X receptor-alpha expression vectors as well as results of nuclear transcription assays did not indicate transcriptional regulation of calbindin-D28k by RA. Studies of calbindin-D28k mRNA in control and RA-pretreated D283 medulloblastoma cells at various times (3-24 h) after treatment with 4 micrograms/ml actinomycin D indicated that the half-life of calbindin-D28k mRNA was significantly increased in the presence of RA, suggesting regulation of calbindin-D28k mRNA stability by RA. Thus, calbindin-D28k is one of the few known targets of RA action in cells that express a neuronal phenotype. In addition, our findings present further evidence of an interrelationship between the actions of 1,25-dihydroxyvitamin D3 and the active metabolites of vitamin A.

Introduction of nerve growth factor (NGF) receptors into a medulloblastoma cell line results in expression of high- and low-affinity NGF receptors but not NGF-mediated differentiation.

Expression of the cloned human nerve growth factor receptor (NGFR) cDNA in cell lines can generate both high- and low-affinity binding sites. Since the inability to respond appropriately to differentiation factors such as NGF may contribute to determining the malignant phenotype of neuroblastomas, we sought to determine whether the same is true of medulloblastomas. To generate a human central nervous system neuronal cell line that would respond to NGF, we infected the medulloblastoma cell line D283 MED with a defective retrovirus carrying the cDNA coding for the human NGFR. The resultant cells (MED-NGFR) expressed abundant low- and high-affinity NGFRs, and NGF treatment induced a rapid transient increase of c-fos mRNA in the NGFR-expressing cells but not in the parent line or in cells infected with virus lacking the cDNA insert. However, the MED-NGFR cells did not internalize the NGFR at high efficiency, nor did they differentiate in response to NGF. Three important conclusions emerge from this study: (i) internalization of NGFRs is not necessary for some early rapid transcriptional effects of NGF; (ii) an unknown factor(s) that cooperates with the cloned NGFR in allowing high-affinity NGF binding is found in a primitive central nervous system cell line; and (iii) NGFRs introduced into and expressed by D283 MED (i.e., MED-NGFR) cells are partially functional but are unable to induce differentiation in these primitive neuron-like tumor cells, implying that high-efficiency receptor-mediated endocytosis of NGF and its receptor may be a necessary step in the cascade of events leading to NGF-mediated differentiation.