Current Cancer Drug Targets - Volume 5, Issue 4, 2005

Acute myelogenous leukemia (AML) is an aggressive disorder with an overall disease-free survival of 40-50% even for the younger patients under 60 years of age who can receive the most intensive treatment. The median age at the time of diagnosis is 60-65 years, and the large majority of elderly patients usually receive less intensive chemotherapy or only supportive therapy due to the high treatment-related mortality when using intensive therapy for elderly individuals. Thus, there is a need for new therapeutic approaches to improve the treatment in younger patients and to make AML-directed therapy with acceptable toxicity possible in elderly individuals. Angiogenesis seems to be important both for leukemogenesis and susceptibility to intensive chemotherapy, and antiangiogenic strategies are therefore considered for the treatment of AML. The two proangiogenic mediators vascular endothelial growth factor (VEGF) and interleukin 8, (IL-8, also referred to as CXCL8) seem to be important in human AML: VEGF is released at increased levels due to interactions between AML cells and neighboring nonleukemic cells, whereas IL-8 is released at high levels by native human AML cells. Thus, VEGF as a therapeutic target in AML is suggested both by experimental and clinical observations, whereas IL-8 as a target is mainly suggested by experimental evidence. In the present review we describe and discuss (i) the angioregulatory network of soluble mediators in AML, including both the systemic levels and local release by native human AML cells; and (ii) various therapeutic approaches to target VEGF and IL-8. Although single angioregulatory mediators can be targeted, it should be emphasized that the final effect of soluble mediators on angioregulation is determined by a complex angioregulatory network that varies between AML patients, and the final effect of targeting single mediators may therefore differ between patient subsets.

Angiogenesis, the formation of new blood vessels, is essential for tumor growth, progression and metastasis. The development of agents that target tumor vasculature is ultimately dependent on the availability of appropriate preclinical screening assays. The chorioallantoic membrane (CAM) assay is well established and widely used as a model to examine angiogenesis, and anti-angiogenesis. This review 1) summarizes the currently used angiogenesis assays and the importance of CAM model among them; 2) summarizes the current knowledge about the development and structure of the CAM's capillary bed; 3) reports findings regarding the role played by molecular signaling pathways in angiogenesis process; 4) discusses the use, advantages and limitations of the CAM as a model for studying tumor angiogenesis and invasiveness, as well as development of angiogenic and/or anti-angiogenic agents; 5) discusses the importance of standardization of the major methodologies for all aspects of the use of the CAM in angiogenesis-related studies; 6) and finally, summarizes major findings regarding the agents developed by the use of CAM model in the study of tumor angiogenesis, invasion and development of anti-angiogenic agents.

The purpose of this mini-review is to summarize and highlight the different advances in our understanding of the antimicrobial and antiangiogenic activity of squalamine, a cationic steroid isolated in 1993 from the dogfish shark Squalus Acanthias. Indeed, squalamine has shown to be useful for the treatment of important diseases such as cancers (lung, ovarian, brain and others), age-related macular degeneration (AMD) and the control of body weight in man. All these results led to a question: could we consider squalamine as a polyvalent drug of the future?

MYCN belongs to the MYC family of proto-oncogenes, which encode for transcription factors of the basic-helix-loop-helix-zipper (bHLHZ) class and is fundamental in the development of the peripheral and central nervous systems (PNS and CNS). While Myc is ubiquitous, MYCN has a very restricted expression pattern: it is mainly expressed during embryonic development, but then becomes downregulated, while in adults it is usually detected in B-cell development. Identification of selective inhibitors of MYCN and its mRNA and protein could be important for the development of more specific, effective and less toxic therapeutic agents for tumors of the PNS and CNS. In children, the most common tumors of the PNS and CNS are neuroblastomas and medulloblastomas, respectively. About 30% of neuroblastoma (NB) tumors present MYCN amplification/over-expression, which is associated with rapid progression and poor prognosis. N-Myc is essential during neurogenesis for the rapid expansion of progenitor cells in the brain. MYCN amplification and over-expression has been reported in medulloblastoma, and especially in the desmoplastic type. Other tumors associated with MYCN overexpression include retinoblastoma, small cell lung carcinoma, glioblastoma and certain embryonal tumors. A cell-based, N-Myc-dependent luciferase reporter gene assay to identify specific N-Myc small-molecule inhibitors has allowed identification of five compounds showing significant activity. Antisense oligodeoxynucleotides have been shown to inhibit N-Myc production and anti-tumoral activity in vitro and in vivo for NB. Peptide nucleic acids (PNA), which belong to the most recent (third) generation of nucleic acid therapeutics, form highly stable duplexes with DNA and RNA, and are resistant to degradation by nucleases and proteases. Encouraging results have been reported utilizing a PNA-based antisense strategy for inhibition of N-Myc expression in neuroblastoma.

Matrix metalloproteinases (MMPs), also designated as matrixins, play a central role in many biological processes and are involved both in physiologic cellular processes and in pathologic situations such as tumor growth, invasion and metastasis. For more than 30 years MMPs have been considered as promising targets for cancer therapy and a number of different synthetic and natural MMP inhibitors have been identified as cytostatic and anti-angiogenic agents and have begun clinical testing in view of their specific implication in malignant tissues. Although preclinical studies were so compelling to encourage several clinical trials, the past years have seen a consistent number of disappointments and limited success. The critical examination of previous studies shed light on new information about the cellular source, substrates and mode of action of MMPs, focusing the attention of future research on the identification of specific MMP targets in tumors at different stage of tumor progression, both in order to improve efficacy and to reduce the side effect profile. In this review we discuss the current view on the feasibility of MMPs as target for therapeutic intervention in cancer, taking into account that the perspective may be of great value for molecular medicine for the twenty-first century, providing intriguing information about the MMPs as mediators in biology and pathology, and as targets for disease therapies.

Gardenia, the fruit of Gardenia jasminoides Ellis, has been widely used to treat liver and gall bladder disorders in Chinese medicine. It has been shown recently that geniposide, the main ingredient of Gardenia Fructus, exhibits the anti-tumor effect. In this review, we discuss the anti-tumor effect and possible mechanisms of a derivative from Gardenia Fructus, penta-acetyl geniposide ((Ac)5GP). It has been demonstrated that (Ac)5GP plays more potent roles than geniposide in chemoprevention. (Ac)5GP decreased DNA damage and hepatocarcinogenesis induced by aflatoxin B1 (AFB1) by activating the phase II enzymes glutathione S-transferase (GST) and GSH peroxidase (GSH-Px). It reduced the growth and development of inoculated C6 glioma cells especially in pre-treated rats. In addition to the preventive effect, (Ac)5GP exerts its actions on apoptosis and growth arrest. Treatment of (Ac)5GP caused DNA fragmentation of glioma cells. (Ac)5GP induced sub- G1 peak through the activation of apoptotic cascades PKCd/ JNK/ Fas/ caspase8 and caspase 3. Besides, p53/ Bax signaling was suggested to be involved in (Ac)5GP-induced apoptosis, though its downstream cascades needs further clarified. (Ac)5GP has also been shown to inhibit DNA synthesis of tumor cells. It arrested cell cycle at G0/ G1 by inducing the expression of p21, thus suppressing the cyclin D1/ cdk4 complex formation and the phosphorylation of E2F. The phosphorylation status of p53 on serine 392 correlated with the process of growth arrest. Evidences from the in vivo experiments showed that (Ac)5GP is not harmful to liver, heart and kidney. In conclusion, (Ac)5GP is highly suggested to be an anti-tumor agent for development in the future.