Background With current treatment strategies, nearly half of all medulloblastoma (MB) patients die from progressive tumors. compared with DAOY wild-type or DAOY cells transfected with the empty vector. Conclusion In human MB cells, in addition to its roles in growth and proliferation, c-MYC is also a potent inducer of apoptosis. Therefore, targeting c-MYC might be of therapeutic benefit when used sequentially with chemo- and radiotherapy rather than concomitantly. Background Medulloblastomas (MB) are the most common malignant pediatric neoplasms of the central nervous system. MB constitute 20% of all pediatric brain tumors [1] and are characterized by their aggressive clinical behavior and a high risk of leptomeningeal dissemination. With current treatment strategies, nearly half of all patients eventually die from progressive tumors. Accordingly, the identification of novel therapeutic 832115-62-5 IC50 strategies CEBPE remains a major goal. The c-MYC proto-oncogene encodes a nuclear phosphoprotein involved in the transcription of genes central to regulating the cell cycle [2-4], proliferation [5,6], apoptosis [7-9], telomere maintenance [10,11], 832115-62-5 IC50 angiogenesis [12], and differentiation [13]. The c-MYC oncoprotein plays a pivotal role as a regulator of tumorigenesis in numerous human cancers of diverse origin [14-17]. Deregulated expression 832115-62-5 IC50 of c-MYC is often associated with aggressive, poorly differentiated tumors [4]. Deregulation of c-MYC expression is evident in MB with c-MYC gene amplification or aberrant signal transduction of wingless (WNT) signaling pathway [18]. In MB, high c-MYC mRNA expression and c-MYC gene amplification have been described as indicators of poor prognosis [19-22]. Furthermore, two studies have demonstrated that high c-MYC mRNA expression is associated with tumor anaplasia [23,24]. Developing therapeutic approaches to inhibit c-MYC would have an enormous impact on the treatment of a wide range of human cancers [25-27]. Many strategies are currently under development to target c-MYC in tumor cells, including inhibitors that block c-MYC expression, such as antisense oligonucleotides and small interfering RNA (siRNA) [28]. One aspect to be considered by evaluating the potential of c-MYC as a novel therapeutic target 832115-62-5 IC50 in MB, is its impact on cellular sensitivity to radio- and chemotherapy. In the present study, siRNA-mediated c-MYC inhibition was used to study the biological role of c-MYC in a representative panel of human MB cells expressing different levels of c-MYC. Methods Human MB cell lines DAOY (wild-type), DAOY V11 (empty vector-transfected), and DAOY M2 (c-MYC-transfected) human MB cells have been described previously [24]. D341 and D425 human MB cells were the kind gift of Dr Henry Friedman, Duke University, Durham, NC, USA. DAOY, D341, and D425 MB cell lines are derived from three different MB obtained at craniotomy of patients aged 3C5 years [21,29,30]. All MB cells were cultured in Richter’s zinc option medium (Invitrogen; Basel, Switzerland) supplemented with 10% fetal bovine serum. Non-essential amino acids were added to the medium of D341 and D425 cells to a final concentration of 1%, and G418 was added to the medium of DAOY V11 and DAOY M2 to a final concentration of 500 g/ml. All cell cultures were maintained at 37C in a humidified atmosphere with 5% CO2. Down-regulation of c-MYC The Silencer c-MYC validated siRNA targeting the 3′-untranslated region of the human c-MYC mRNA sequence [31,32], referred to here as c-MYC siRNA, and Silencer scrambled c-MYC negative control siRNA, referred to here as control siRNA, having no significant homology to any known gene sequences from mouse, rat, or human, were purchased from Ambion, and used according to the manufacturer’s instructions [33]. In brief, small interfering RNAs (siRNAs).