Low DLG2 gene expression, a link between 11q-deleted and MYCN-amplified neuroblastoma, causes forced cell cycle progression, and predicts poor patient survival.

Abstract

Neuroblastoma (NB) is a childhood neural crest tumor. There are two groups of aggressive NBs, one with MYCN amplification, and another with 11q chromosomal deletion; these chromosomal aberrations are generally mutually exclusive. The DLG2 gene resides in the 11q-deleted region, thus makes it an interesting NB candidate tumor suppressor gene. Methods We evaluated the association of DLG2 gene expression in NB with patient outcomes, stage and MYCN status, using online microarray data combining independent NB patient data sets. Functional studies were also conducted using NB cell models and the fruit fly. Results Using the array data we concluded that higher DLG2 expression was positively correlated to patient survival. We could also see that expression of DLG2 was inversely correlated with MYCN status and tumor stage. Cell proliferation was lowered in both 11q-normal and 11q-deleted NB cells after DLG2 over expression, and increased in 11q-normal NB cells after DLG2 silencing. Higher level of DLG2 increased the percentage of cells in the G2/M phase and decreased the percentage of cells in the G1 phase. We detected increased protein levels of Cyclin A and Cyclin B in a fruit fly model over expressing dMyc or silencing dmDLG , indicating that both events results in enhanced cell cycling. Induced MYCN expression in NB cells, lowered DLG2 gene expression, this was confirmed in the fly, when dMyc was over expressed, the dmDLG protein level was lowered, indicating a link between Myc over expression and low dmDLG level. Conclusion We conclude that low DLG2 expression level forces cell cycle progression, and that it predicts poor NB patient survival. The low DLG2 expression level could be caused by either MYCN -amplification or 11q-deletion.

The loss of DLG2 isoform 7/8, but not isoform 2, is critical in advanced staged neuroblastoma

“…We have previously established that DLG2 is a candidate tumor suppressor gene with importance in 11q deleted NB as well as a downregulated target of the oncogene MYCN, commonly ampli ed in aggressive NB (4). During which, we did not explore the various isoforms of DLG2 and the effects that the resulting proteins have on NB.…”

“…Within the 11q-deleted region, resides the gene Discs Large Homologue 2 (DLG2). Low expression of DLG2 is seen in a majority of aggressive NBs, including both the 11q-deleted subset and those with MYCN ampli cation (4). Also Anaplastic Lymphoma Kinase (ALK) activity seems to affect the DLG2 expression in NB (5).…”

“…Also Anaplastic Lymphoma Kinase (ALK) activity seems to affect the DLG2 expression in NB (5). Low DLG2 level forces cell cycle progression (4) and results in an undifferentiated state in NB cells (5). In addition to NB, abnormally low DLG2 expression is reported in osteosarcoma (6) and ovarian cancer (7).…”

Identification of aberrantly methylated differentially expressed genes in papillary thyroid carcinoma using integrated bioinformatic analysis

“…One of the key ndings from these studies was that DLG had tumor suppressor properties in Drosophilalarvae: loss of DLG function was associated with excessive over proliferation and neoplastic transformation of epithelial cells within the imaginal discs [16]. Disruption of Drosophila DLG also resulted in acute disorganization of epithelial structure with disruption of intercellular junction formation and a loss of apico-basal cell polarity [17], whereas in C.elegans the single homologue of Drosophila DLG, homologue of Drosophila DLGs required for proper adherens junction formation.…”

DLG2 impairs dsDNA break repair and maintains genome integrity in neuroblastoma

“…In NB, the 11q-deleted region spans a number of candidate tumor suppressor genes such as ATM, H2AX, CHK1 and MRE11a [6], all of which are involved in DNA damage response (DDR) [27]. Recently, 11q deleted NB was shown to have abnormally low expression of Discs Large Homologue 2 (DLG2; 11q14) [27,28]. Low DLG2 expression has also been found in osteosarcoma [29] and ovarian cancer [30].…”