N-MYC Regulates Focal Adhesion Kinase Expression in Human Neuroblastoma

Abstract

N-MYC is a transcription factor important for the control of cellular differentiation and proliferation (1, 2). It is normally expressed in the brain and peripheral nervous system (1). N-MYC has been shown to influence the differentiation of neural crest cells. Early in mouse embryogenesis, N-MYC is present primarily in the migrating neural crest cells, but as the embryo matures, the expression of N-MYC becomes limited to those cells that are undergoing neuronal differentiation (3). Abnormal expression of N-MYC is most notably associated with the pediatric tumor of neural crest origin, neuroblastoma. Amplification of the N-MYC oncogene is the primary adverse prognostic indicator in human neuroblastoma (4, 5). The level of N-MYC expression has been shown to correlate with the growth (6 -9) and invasiveness (10) of neuroblastoma cells, and transgenic mice with N-MYC overexpression develop spontaneous neuroblastoma tumors (11). In addition, down-regulation of N-MYC with antisense oligonucleotides leads to decreases in both cellular proliferation and in anchorageindependent growth in the neuroblastoma cells (6, 9). Despite this information, the exact function and transcriptional gene targets of N-MYC in neuroblastoma are currently not well characterized (5).Focal adhesion kinase (FAK) 3 is a nonreceptor cytoplasmic 125-kDa protein-tyrosine kinase. Initial studies revealed that both the transcription of FAK mRNA (12) and the expression of FAK protein (13-19) are significantly increased in primary and metastatic breast, colon, and thyroid tumors compared with normal tissues and that these changes occur early in tumorigenesis. Real time PCR analysis of colorectal carcinoma and liver metastasis with matched normal colonic tissues demonstrated increased FAK mRNA abundance in the tumors and metastatic tissues compared with control tissues (20), suggesting that the increased FAK expression in human tumors occurs at the level of transcription. Recently the FAK promoter was cloned and characterized, and transcriptional regulation of the FAK promoter has been demonstrated (21).FAK controls a number of cell signaling pathways including proliferation, viability, motility, and survival (22-25). The inhibition of FAK with antisense oligonucleotides has been shown to cause decreased growth in tumor cells (26). In addition, FAK inhibition with a dominant-negative FAK protein (FAK-CD) inhibited cell growth in human melanoma cells (12) and in * The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

Transforming Growth Factor-β Stimulates Intestinal Epithelial Focal Adhesion Kinase Synthesis via Smad- and p38-Dependent Mechanisms

“…62 In a neuroblastoma cell line, NMYC, a transcription factor important in cell survival, was shown to bind to the FAK promoter and increase FAK mRNA. 63 On the other hand, eprhin-A1 down-regulates FAK In human glioma U251 cells. 64 Our present and previous results demonstrate that FAK protein levels can be both down-regulated (by motility) and up-regulated (by exposure to TGF-␤) in intestinal epithelial cells.…”

Focal Adhesion Kinase Expression in Human Neuroblastoma: Immunohistochemical and Real-time PCR Analyses

“…New biomarkers and potential therapeutic targets will be needed to provide novel strategies for the detection and treatment of this tumor. We have recently reported an increase in both FAK mRNA and protein expression in human neuroblastoma cell lines that have amplification of the N-MYC oncogene (24). To date, there have been no reports detailing the expression of FAK in human neuroblastoma specimens.…”

ATM is down-regulated by N-Myc–regulated microRNA-421

“…An FC-pSMC1 assay was performed as previously described (25), and a ChIP assay was performed as previously described (40). More detailed protocols for Fc-pSMC1 and ChIP assays are provided in SI Text.…”