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.

No abstract

Neuroblastoma is the most common extracranial solid tumor of childhood. Focal adhesion kinase (FAK) is an intracellular kinase that regulates both cellular adhesion and apoptosis. FAK is overexpressed in a number of human tumors including neuroblastoma. Previously, we have shown that the MYCN oncogene, the primary adverse prognostic indicator in neuroblastoma, regulates the expression of FAK in neuroblastoma. In this study, we have examined the effects of FAK inhibition upon neuroblastoma using a small molecule [1,2,4,5-benzenetetraamine tetrahydrochloride (Y15)] to inhibit FAK expression and the phosphorylation of FAK at the Y397 site. Utilizing both non-isogenic and isogenic MYCN+/MYCN− neuroblastoma cell lines, we found that Y15 effectively diminished phosphorylation of the Y397 site of FAK. Treatment with Y15 resulted in increased detachment, decreased cell viability and increased apoptosis in the neuroblastoma cell lines. We also found that the cell lines with higher MYCN are more sensitive to Y15 treatment than their MYCN negative counterparts. In addition, we have shown that treatment with Y15 in vivo leads to less tumor growth in nude mouse xenograft models, again with the greatest effects seen in MYCN+ tumor xenografts. The results of the current study suggest that FAK and phosphorylation at the Y397 site plays a role in neuroblastoma cell survival, and that the FAK Y397 phosphorylation site is a potential therapeutic target for this childhood tumor.

Acute myeloid leukemia (AML) arises from neoplastic transformation of hematopoietic stem and progenitor cells, and relapsed disease remains one of the greater challenges in treating this hematologic malignancy. This paper focuses on angiogenic aspects of AML including the significance and prognostic value of bone marrow microvessel density and circulating cytokine levels. We show three general mechanisms whereby AML exploits angiogenic pathways, including direct induction of angiogenesis, paracrine regulation, and autocrine stimulation. We also present early evidence that leukemia cells contribute directly to vascular endothelia. Novel treatment strategies are proposed, and a review of relevant antiangiogenic clinical trials is presented. By understanding how blood vessels can serve as a reservoir for refractory and relapsed AML, new diagnostics and promising treatment strategies can be developed.