Anti-Cancer Agents in Medicinal Chemistry (Formerly Current Medicinal Chemistry - Anti-Cancer Agents) - Volume 12, Issue 7, 2012

Matrix metalloproteinases (MMPs) are known to participate in cancer invasion and metastasis. Copious research on MMPs and their inhibitors has promoted the understanding of the mechanisms of cancer invasion and metastasis as well as the development of effective drugs for cancer treatment. This review discusses the classification of MMPs and tissue inhibitors of metalloproteinases (TIMPs) in relation to tumor growth and invasion mechanisms via signal transduction, followed by the possibilities for cancer treatment. The review focuses especially on the development of anti-cancer agents in the field of MMP science.

Five decades of extensive research have passed since the description for the first time of the existence of an enzyme, which had the ability to degrade collagen during the metamorphosis of tadpoles. In fact, during these years, a large family of enzymes possessing the unique ability of degrading the extra cellular matrix (ECM) has been discovered. These enzymes are widely known as Matrix Metalloproteinases (MMPs) and it is noteworthy that many members of this family are directly linked to several human diseases such as arthritis and cancer. Moreover, due to the critical role of certain members of MMPs in cancer invasion and metastasis, great efforts have been made in order to find new inhibitory compounds against these MMPs. In this work we attempt to summarize the current status of the intervention strategies against MMPs, using inhibitory compounds that could block the activation of MMPs directly or indirectly. Furthermore we will try to shed light towards new potential strategies of MMP inhibitors using monoclonal antibodies.

Reversion-inducing-cysteine-rich protein with Kazal motifs (RECK) is a membrane-anchored glycoprotein that negatively regulates the activities of matrix metalloproteinases (MMPs) and inhibits tumor invasion, metastasis, and angiogenesis. RECK is essential for normal development and is a key mediator of tissue remodeling and stabilization of tissue architechture. Downregulation of RECK documented in a wide range of malignant neoplasms correlates with poor prognosis, and tumor metastasis. The RECK gene is a common negative target for oncogenic signals that act on the Sp1-binding site of the RECK promoter. Both natural and synthetic agents have been identified as upregulators of RECK. Several strategies have been proposed to enhance RECK expression including forced expression of RECK, use of mimetics, recombinant peptides, microRNA antagonists, and gene therapy. Upregulation of RECK could be a valuable therapeutic option to improve prognosis and block tumor progression. This review addresses the potential value of RECK as a prognostic marker and as a molecular target for cancer therapy.

MMPs are a family of Zn dependent endopeptidases, which can mediate degradation of ECM components during various physiological and pathological processes including cancer. Some ECM components, through interaction with integrin receptor and modulation of downstream signaling, are capable of regulating expression and activity of several MMPs. α5β1 integrin is the universally accepted receptor for the ECM component fibronectin (FN). The present review deals with the downstream signaling involved in the α5β1 integrin mediated modulation of expression and activity of MMPs and their effector responses in different cellular system.

MicroRNAs have come to represent a significant mechanism of post transcriptional gene regulation affecting processes as varied as cellular differentiation, proliferation, metabolism, apoptosis, and cancer. As more miRNAs are unravelled and their roles dissected, it has become evident that the involvement of these molecules in cancer is much more extensive than initially thought. Several miRNA expression analyses in both haematological malignancies and solid tumors have shown that, aside significant differences in expression between tumor and normal states, distinct tumor specific miRNA signatures exist. Additionally, the ability of miRNAs to mediate both oncogenic and tumor suppressor functions further broadens their functional significance. In recent years, efforts have intensified to utilize miRNAs therapeutically, especially in the context of oncomirs. As far as the impact and the success of this approach are concerned, it is still early days, but the potential is enormous. This review focuses on the important miRNAs that have been found to impact the tumorigenic process, how far we have come in terms of utilizing these molecules for therapy and the outlook for the near future.

Lung cancer is a heterogeneous disease with several histologic subtypes. The two major pathologies, which account for approximately 70% of lung cancers, are adenocarcinoma (AD) and squamous cell carcinoma (SQ). Traditionally, these two subtypes have been categorized as non-small-cell lung cancer and treated similarly. However, they are different not only pathologically, but also functionally. For example, 18F-fluorodeoxyglucose positron emission tomography (FDG-PET), which assesses glucose metabolism in tumor tissues, shows that SQ has higher glucose metabolism than does AD. Matrix metalloproteinases (MMPs) and their inhibitors play pleiotropic roles in cancer development, carcinogenesis, apoptosis, angiogenesis, invasion and metastasis. Expression of MMPs and their associated molecules is different among the subtypes of lung cancer. Expression levels of MMP-2, MMP-7, reversion-inducing cysteine-rich protein with Kazal motifs (RECK), tissue inhibitors of metalloproteinase (TIMP)-1, and TIMP-2 are higher in AD than in SQ. In contrast, expression levels of MMP-1, MMP-8, MMP-9 and TIMP-3 are higher in SQ than in AD. Serum levels of a disintegrin and metalloproteinase (ADAM)-8 and ADAM-28 are higher in lung cancer patients than in healthy controls. High expression of ADAM-28 correlates with metastasis and recurrence, but there is no significant difference in ADAM-8 or ADAM-28 expression between AD and SQ. It is necessary to recognize the differential expression patterns of MMPs, their endogenous inhibitors and associated molecules for each subtype of lung cancer in order to develop clinical markers, therapeutic inhibitors and treatment strategies using MMP inhibitors.

Hepatocellular carcinoma (HCC) is a cancer with extremely poor prognosis. This review discusses the pathological characteristics of multi-step hepatocarcinogenesis, tumor growth, invasion and metastasis, the expression of matrix metalloproteinases (MMPs) and their inhibitors via signal transduction in relation to dedifferentiation of hepatoma cells. It introduces the reports on anti-cancer agents in the field of MMP science, and finally describes novel strategies for the early stages of HCC in relation to cancer stem cells.

In the United States, about 22,000 women will be diagnosed with ovarian cancer in 2011, and an estimated 14,000 patients will succumb to the disease [1]. Surgery and chemotherapy present the main treatment modalities, but despite the development of novel therapies, the overall 5 years survival for ovarian cancer patients with advanced disease at diagnosis remains at only about 30%. Novel therapeutic strategies are needed to prolong survival and achieve greater cure rates. Matrix metalloproteinases (MMPs) are frequently expressed in ovarian cancer, and play an important role in the metastatic process. MMPs mediate degradation of the basement membrane as a crucial step in epithelial transformation, ovarian tumorigenesis and intraperitoneal metastasis [2]. Various preclinical and clinical studies have demonstrated that MMPs might provide a suitable therapeutic target. This review summarizes important observations regarding the expression of MMPs in ovarian cancer, their biological role, and data from clinical trials targeting MMPs in ovarian cancer patients.

Melanoma is the most severe skin cancer characterized by a bad prognosis at metastatic stages due to resistance to most classical chemotherapies. Invasion of melanoma cells into the surrounding microenvironment locally and at distance of the primary tumour, is facilitated by expression of proteases that degrade the extracellular matrix. Matrix metalloproteinases (MMP) have been long thought as potential therapeutic targets as they are involved in several steps of tumour progression. However, based on this general concept, broad spectrum MMP inhibitors showed weak anticancer potential. Furthermore, MMPs are also expressed by stroma and infiltrating cells. Although, inflammatory conditions lead to uncontrolled expression of MMPs leading to massive matrix destruction, these enzymes are also essential for immune cells to migrate towards the tumour site, and hence mount an anti-tumoral response. During stromal reaction, MMPs also act as non-matrix deteriorating enzymes, and thus modulating the inflammatory response through limited proteolysis of cytokines and chemokines. MMPs contribution to these processes depends on their activity and their expression. Besides the classic control level of transcription by a variety of growth factors and cytokines, the contribution of epigenetic mechanisms on MMPs expression was demonstrated of great importance to extend our knowledge about the role of these enzymes in a specific context such as melanoma progression. Understanding MMPs regulation by epigenetic drugs in melanoma and infiltrated cells will provide a new platform to develop efficient therapies. The therapeutic implication of epigenetic mechanisms to switch a pro-tumoral inflammatory towards an immune anti-tumoral response will be an exciting challenge in which MMPs expression could play a major role.

Emetine and CGP-74514A have previously shown antitumor activity in neuroendocrine tumor cell lines. The aim of this study was to investigate the cytotoxic activity of the drugs in a three-dimensional model and to study if the mechanism of the cytotoxic activity was induction of apoptosis. An in vitro hollow fiber model was used to study the cytotoxic effect and a multiparametric high-content screening assay was used for measurement of apoptosis. The human pancreatic carcinoid cell line, BON-1 and the human typical and atypical bronchial carcinoid cell lines NCI-H727 and NCI-H720 were tested. Emetine and CGP-74514A showed higher antitumor activity on NCI-H720 compared to NCI-H727 and 3 day cultures were more sensitive than the 14 day cultures. A time- and dose-dependent activation of caspase-3 and increase in nuclear fragmentation and condensation were observed for the drugs in NCI-H727 and BON-1 using a multiparametric apoptosis assay. These results were confirmed with nuclear morphological examinations on microscopic slides. Emetine and CGP-74514A showed antitumor activity and induced caspase-3 activation with modest changes in nuclear morphology, indicating induction of apoptosis.

Malignant cells in solid tumors survive under prolonged hypoxia and can be a source of resistance to current cancer therapies. Tumor hypoxia is also associated with a more malignant phenotype and poor survival in cancer patients. Recent progress in our understanding of the biology of tumor cells under hypoxia has led to increased attention on targeting hypoxia for cancer therapy. We report here that a novel fusicoccin derivative (ISIR-042), but not its parent or related compounds such as fusicoccin A and cotylenin A, is more cytotoxic to hypoxic cells than to normoxic cells. The hypoxia-induced accumulation of hypoxia-inducible factor (HIF)-1α and the phosphorylation of Akt were effectively inhibited by treatment with ISIR-042, suggesting that the preferential cytotoxicity toward hypoxic cells is associated with a reduction of HIF-1α and Akt activation. ISIR-042 inhibited the growth of human pancreatic cancer MIAPaCa-2 cells while sparing normal endothelial cells, and significantly inhibited the growth of MIAPaCa-2 cells as xenografts without apparent adverse effects. Pancreatic cancer cells expressing CD24 and CD44 exhibited characteristics of stem cells. Treatment with gemcitabine increased this stem cell-enriched population, and this effect was significantly inhibited by ISIR-042, suggesting that ISIR- 042 preferentially inhibits stem/progenitors in pancreatic cancer cell lines compared with chemotherapeutic agents. These results suggest that ISIR-042 may be a potential therapeutic agent for hypoxic tumors such as pancreatic cancer.

A series of N-substituted amino caproic hydroxamic acid histone deacetylase inhibitors derivatives was designed in good-toexcellent yields and evaluated for their antiproliferative activity in a panel of human cancer cell lines, showing half maximum effective concentration varying from 700 nM to > 100 μM. Interestingly, the replacement of a furyl group by a thienyl one impacted very significantly the cap role on this antiproliferative activity and on histone acetylation induced by these drugs in cell-based but also in cell-free enzyme assays, suggesting an important role of the electronic density attached to the oxygen or sulfur atoms.

The analysis of the influence of molecular features which can be extracted from the simplified molecular input line entry system (SMILES) and involved in the process of the building up of a series of QSAR models (with different splits into training and test sets) by means of the CORAL software for mutagenicity and anticancer activity has been performed. The presence of nitrogen (sp3) is favorable for decrease of the both endpoints; the presence of only one ring is also promotor for decrease of the both endpoints; however the presence of two or three rings is favorable for increase of mutagenicity and decrease of anticancer activity. These findings provide useful criteria for further experimental and computational studies in the search for new anticancer agents.

All chemotherapeutic agents currently in use have a narrow window of therapeutic index of 1 to 1.2. Camptothecin ester compounds are reported to have a wider therapeutic index when being used to treat human xenografts in nude mice. As a continuous effort in searching for better chemotherapeutic agents for treating cancers, new haloalkyl camptothecin and 9-nitrocamptothecin ester derivatives 2a-b and 3a-d were prepared by respective acylation of camptothecin 1a and 9-nitrocamptothecin 1b with the corresponding acylating agents. These new derivatives were tested in vitro against 8 human cancer cell lines using 7 different concentrations ranging from 5 to 300 nM and also in vivo against various types of human tumor xenografts grown in nude mice. Most of these new compounds started showing inhibitory effects on the growth of 8 cancer cell lines at concentration of 80 nM and achieved greater than 70% inhibitions against these cell lines when the concentration increased to 300 nM. Compound 2a and 3a showed good activity against human tumor xenografts in nude mice. Compared to mother compound camptothecin, 3a was much less toxic in mice with a better therapeutic index, having the potential to be further developed as a safer treatment for cancers.

R (rituximab)-CHOP (cyclophosphamide, adriamycin, vincristin, and prednisone) is given to outpatients with CD20-positive lymphoma as a standard treatment. However, this regimen requires long-term infusion because of the necessity for monitoring the infusion reaction (IR) during R administration. In this study, pharmacological changes in anti-tumor agents were examined after the joint use of R and CHOP, and the possibility of concurrent administration of R and CHOP for outpatients was discussed. After combining antitumor agents with R, the binding capacity of R to the CD20 peptide and molecular changes in anti-tumor agents were measured by ELISA and LC/MS/MS-based analysis. At the same time, a pilot study involving concurrent administration of R and CHOP to patients with diffuse large B-cell lymphoma (DLBCL) was carried out after the first course of R-CHOP. After combining with either adriamycin or cyclophosphamide, the binding capacity of R to the CD20 antigen was equivalent to controls, and no molecular changes in adriamycin and cyclophosphamide were detected after combination with R. Twenty-one cases of DLBCL were treated safely with concurrent administration of R and CHOP. Twenty patients achieved complete remission after a full course of R-CHOP. The results indicated that long-term medication might not be necessary for outpatients treated with R-CHOP.