Overview of the clinical efficacy of investigational anticancer drugs

Evaluation of the antimicrobial and cytotoxic potential of endophytic fungi extracts from mangrove plants Rhizophora stylosa and R. mucronata

Mangrove endophytic fungi are tolerant to numerous stresses and are inevitably capable of exhibiting excellent biological activity by producing impressive numbers of metabolites with special biological functions, based on previous work on the biological potential of mangrove-derived endophytic fungi. To obtain marked antimicrobial and cytotoxic fermentation products of culturable endophytic fungi from mangrove forests, our research evaluated the antimicrobial and cytotoxic activities of crude extracts of endophytic fungi from Rhizophora stylosa and Rhizophora mucronata. Forty-six fungal isolates were cultured on four different media, namely, dextrose agar (PDA), Czapek’s agar (CZA), rice medium (RM) and grain medium (GM) and harvested by ethyl acetate solvent at 40 days. The extracts were tested for antimicrobial activity by the microdilution method against the gram-negative bacteria Pseudomonas adaceae (PA), gram-positive bacteria Enterococcus faecalis (EF), methicillin-resistant Staphylococcus aureus (MRSA) and pathogenic fungus Monilia albicans (MA). The cytotoxic activity of the extracts was evaluated by MTT assay using A549 human lung cancer cells, HeLa human cervical carcinoma cells, and HepG2 human hepatocellular cells. The results showed that rice medium could promote the secretion of antimicrobial and antitumour secondary metabolites of endophytic fungi in comparison with other cultivation media. Seventeen strains (68%) from R. stylosa exhibited inhibitory effects on indicators, especially N. protearum HHL46, which could inhibit the growth of four microbes with MIC values reaching 0.0625 mg/mL. Fifteen strains (71.4%) from R. mucronata displayed activities against human pathogenic microbes; in particular, Pestalotiopsis sp. HQD6 and N. protearum HQD5 could resist the growth of four microbes with MIC values ranging from 0.015 to 1 mg/mL. In the cytotoxicity assay, the extracts of 10 strains (40%), 9 strains (40%) and 13 strains (52%) of R. stylosa and 13 strains (61.9%), 10 strains (47.6%) and 10 strains (47.6%) of R. mucronata displayed cytotoxicity against A549, HeLa and HepG2 cancer cells with cell viability values ≤ 50%. Neopestalotiopsis protearum HHL46, Phomopsis longicolla HHL50, Botryosphaeria fusispora HQD83, Fusarium verticillioides HQD48 and Pestalotiopsis sp. HQD6 displayed significant antitumour activity with IC₅₀ values below 20 μg/mL. These results highlighted the antimicrobial and antitumour potential of endophytic fungi from R. stylosa and R. mucronata and the possibility of exploiting their antimicrobial and cytotoxic agents.

Preparation and in vitro bioactivity evaluation of N-heterocyclic-linked dihomooxacalix[4]arene derivatives

Based on the superior prospects of calixarenes-based agents and N-heterocyclic pharmacophores in biomedical applications, 14 new dihomooxacalix[4]arene N-heterocyclic (pyridine, quinoline, and thiazole) derivatives 4a-4n were efficiently synthesized from the parent compound, namely, p-tert-butyldihomooxacalix[4]arene 1; they were further investigated by using their IR, 1H NMR, 13C NMR, and HRMS spectra. Among these derivatives, the crystal and molecular structures of 2-aminomethyl-pyridine-substituted dihomooxacalix[4]arene 4f (obtained from methanol) have been determined by X-ray diffraction. In the case of the inhibition assay of cell growth, we evaluated the effects on four select tumor cell lines (MCF-7, HepG2, SKOV3, and HeLa), as well as the normal cell lines of HUVEC, using paclitaxel as the positive control drug. It was found that the derivatives 4d-4f, 4i, 4k, and 4l could inhibit tumoral activity up to varying degrees. Mechanistically, the cell cycle analysis demonstrated that dihomooxacalix[4]arene N-heterocyclic derivatives could induce apoptosis of MCF cells. In addition, the results of the western blot and immunofluorescence studies revealed the upregulation of the protein expression levels of Bax and cleaved caspase-3, as well as the downregulation of Bcl-2, which are in good agreement with the corresponding inhibitory potencies. Therefore, these findings suggest that N-heterocyclic derivatives based on the dihomooxacalix[4]arene scaffold are promising candidates for use against cancer.

Repositioning of fluoroquinolones from antibiotic to anti-cancer agents: An underestimated truth

Increasing development costs and higher failure rate in clinical trials has reduced the repertoire of newer drugs in the market for clinical use. The most appropriate approach to end the search for newer drugs is "Repositioning", as it requires less time and money to explore new indication of existing drug or failed drug. In the past, several drugs have been repositioned for different indication but the full potential remains unharnessed. With rise in cancer prevalence and treatment costs, it is imperative to search for newer drugs and the use of repositioning approach may help us. Fluoroquinolones has been used as antibiotics for over four decades now, but recent research highlighted their use as pharmacological compounds with multifaceted implication. Repositioning of fluoroquinolones into anti-cancer molecule seems to be a highly plausible option owing to their profound immunomodulatory, pro-apoptotic, anti-proliferative and anti-metastatic potential. The present review provides a comprehensive account of the recent and past explorations pertaining to the anti-cancer activity of fluoroquinolones and also discusses the various approaches that are being considered to remodel them for the treatment of cancer.

Petri net siphon analysis and graph theoretic measures for identifying combination therapies in cancer

Epidermal Growth Factor Receptor (EGFR) signaling to the Ras-MAPK pathway is implicated in the development and progression of cancer and is a major focus of targeted combination therapies. Physiochemical models have been used for identifying and testing the signal-inhibiting potential of targeted therapies, however, their application to larger multi-pathway networks is limited by the availability of experimentally-determined rate and concentration parameters. An alternate strategy for identifying and evaluating drug-targetable nodes is proposed. A physiochemical model of EGFR-Ras-MAPK signaling is implemented and calibrated to experimental data. Essential topological features of the model are converted into a Petri net and nodes that behave as siphons-a structural property of Petri nets-are identified. Siphons represent potential drug-targets since they are unrecoverable if their values fall below a threshold. Centrality measures are then used to prioritize siphons identified as candidate drug-targets. Single and multiple drug-target combinations are identified which correspond to clinically relevant drug targets and exhibit inhibition synergy in physiochemical simulations of EGF-induced EGFR-Ras-MAPK signaling. Taken together, these studies suggest that siphons and centrality analyses are a promising computational strategy to identify and rank drug-targetable nodes in larger networks as they do not require knowledge of the dynamics of the system, but rely solely on topology.

Versatility of Particulate Carriers: Development of Pharmacodynamically Optimized Drug-Loaded Microparticles for Treatment of Peritoneal Cancer

Intraperitoneal (IP) chemotherapy confers significant survival benefits in cancer patients. However, several problems, including local toxicity and ineffectiveness against bulky tumors, have prohibited it from becoming a standard-of-care. We have developed drug-loaded, tumor-penetrating microparticles (TPM) to address these problems. TPM comprises two components and uses the versatile PLGA or poly(lacticco-glycolic acid) copolymer to provide tumor-selective adherence and pharmacodynamically optimized fractionated dosing to achieve the desired tumor priming (which promotes particle penetration into tumors) plus immediate and sustained antitumor activity. Preclinical studies show that TPM is less toxic and more effective against several IP metastatic tumors with different characteristics (fast vs. slow growing, porous vs. densely packed structures, wide-spread vs. solitary tumors, early vs. late stage, with or without peritoneal carcinomatosis or ascites), compared to the intravenous paclitaxel/Cremophor micellar solution that has been used off-label in previous IP studies. TPM further requires less frequent dosing. These encouraging preclinical results have motivated the follow-up clinical development of TPM. We are working with National Institutes of Health on the IND-enabling studies.

Endophytic fungi with antitumor activities: Their occurrence and anticancer compounds

Plant endophytic fungi have been recognized as an important and novel resource of natural bioactive products, especially in anticancer application. This review mainly deals with the research progress on the production of anticancer compounds by endophytic fungi between 1990 and 2013. Anticancer activity is generally associated with the cytotoxicity of the compounds present in the endophytic fungi. All strains of endophytes producing antitumor chemicals were classified taxonomically and the genera of Pestalotiopsis and Aspergillus as well as the taxol producing endophytes were focused on. Classification of endophytic fungi producing antitumor compounds has received more attention from mycologists, and it can also lead to the discovery of novel compounds with antitumor activity due to phylogenetic relationships. In this review, the structures of the anticancer compounds isolated from the newly reported endophytes between 2010 and 2013 are discussed including strategies for the efficient production of the desired compounds. The purpose of this review is to provide new directions in endophytic fungi research including integrated information relating to its anticancer compounds.

Predictive tests for individualization of pharmacological cancer treatment

BACKGROUND

The selection of cancer drugs for an individual patient is still based mostly on cancer type and stage. Predictive tests are needed to make individualized and more efficient pharmacological cancer treatment possible.

OBJECTIVE

To provide an overview of available, possible future development and principles for development of predictive tests for individualized selection of cancer drugs.

METHODS

Overview of published data.

RESULTS/CONCLUSION

Despite increased knowledge in cancer biology, only limited progress has been made in the development and use of predictive tests. However, rapid progress in this field will be possible using already available and emerging technologies, but requires a paradigm shift in principles for the development and use of cancer drugs. Assessment of drug activity in intact tumor cells and tumor cell gene expression signatures are considered to have greatest potential for the development of versatile predictive tests.

Loss of cancer drug activity in colon cancer HCT-116 cells during spheroid formation in a new 3-D spheroid cell culture system

Clinically relevant in vitro methods are needed to identify new cancer drugs for solid tumors. We report on a new 3-D spheroid cell culture system aimed to mimic the properties of solid tumors in vivo. The colon cancer cell lines HCT-116 wt and HCT-116 wt/GFP were grown as monolayers and for 3 or 6 days on 96-well NanoCulture® plates to form spheroids. Expression of surface markers, genes and hypoxia were assessed to characterize the spheroids and drug induced cytotoxicity was evaluated based on fluorescein diacetate (FDA) conversion by viable cells to fluorescent fluorescein or by direct measurement of fluorescence of GFP marked cells after a 72 h drug incubation. The cells reproducibly formed spheroids in the NanoCulture® plates with tight cell-attachment after 6 days. Cells in spheroids showed geno- and phenotypical properties reminiscent of hypoxic stem cells. Monolayer cultured cells were sensitive to standard and investigational drugs, whereas the spheroids gradually turned resistant. Similar results for cytotoxicity were observed using simplified direct measurement of fluorescence of GFP marked cells compared with FDA incubation. In conclusion, this new 3-D spheroid cell culture system provides a convenient and clinically relevant model for the identification and characterization of cancer drugs for solid tumors.

Novel activity of acriflavine against colorectal cancer tumor cells

A high-throughput screen of the cytotoxic activity of 2000 molecules from a commercial library in three human colon cancer cell lines and two normal cell types identified the acridine acriflavin to be a colorectal cancer (CRC) active drug. Acriflavine was active in cell spheroids, indicating good drug penetration and activity against hypoxic cells. In a validation step based on primary cultures of patient tumor cells, acriflavine was found to be more active against CRC than ovarian cancer and chronic lymphocytic leukemia. This contrasted to the activity pattern of the CRC active standard drugs 5-fluorouracil, irinotecan and oxaliplatin. Mechanistic studies indicated acriflavine to be a dual topoisomerase I and II inhibitor. In conclusion, the strategy used seems promising for identification of new diagnosis-specific cancer drugs.

Low-temperature 1H-NMR spectroscopic study of doxorubicin influence on the hydrated properties of nanosilica modified by DNA

The effect of the anticancer drug--doxorubicin (Dox) on hydration properties of a nanocomposite material deposited on silica and modified by small amount of DNA (0.6 wt%) was studied by means of (1)H NMR spectroscopy at low temperatures (in the range of 200-280 K). Signals of either weakly (WAW) or strongly (SAW) associated water, as well as water associated with electrondonor groups of the composite surface (ASW), were observed. The findings reveal that, depending on the temperature and the composition of the dispersion medium, fast molecular exchange takes place between different forms of interphase water. The presence of Dox (0.1-0.2 wt%) in the dispersion medium leads to change of the relative concentrations of different forms of water.

Proton dynamics in cancer

Cancer remains a leading cause of death in the world today. Despite decades of research to identify novel therapeutic approaches, durable regressions of metastatic disease are still scanty and survival benefits often negligible. While the current strategy is mostly converging on target-therapies aimed at selectively affecting altered molecular pathways in tumor cells, evidences are in parallel pointing to cell metabolism as a potential Achilles' heel of cancer, to be disrupted for achieving therapeutic benefit. Critical differences in the metabolism of tumor versus normal cells, which include abnormal glycolysis, high lactic acid production, protons accumulation and reversed intra-extracellular pH gradients, make tumor site a hostile microenvironment where only cancer cells can proliferate and survive. Inhibiting these pathways by blocking proton pumps and transporters may deprive cancer cells of a key mechanism of detoxification and thus represent a novel strategy for a pleiotropic and multifaceted suppression of cancer cell growth.

Research groups scattered all over the world have recently started to investigate various aspects of proton dynamics in cancer cells with quite encouraging preliminary results. The intent of unifying investigators involved in this research line led to the formation of the "International Society for Proton Dynamics in Cancer" (ISPDC) in January 2010. This is the manifesto of the newly formed society where both basic and clinical investigators are called to foster translational research and stimulate interdisciplinary collaboration for the development of more specific and less toxic therapeutic strategies based on proton dynamics in tumor cell biology.

Carbohydrate-based therapeutics

In recent years there has been a resurgence of interest in the biological roles of carbohydrates and as a result it is now known that carbohydrates are involved in a vast array of disease processes. This review summarises progress in the development of carbohydrate-based therapeutics that involve: inhibition of carbohydrate-lectin interactions; immunisation, using monoclonal antibodies for carbohydrate antigens; inhibition of enzymes that synthesise disease-associated carbohydrates; replacement of carbohydrate-processing enzymes; targeting of drugs to specific disease cells via carbohydrate-lectin interactions; carbohydrate based anti-thrombotic agents.

Identification of a novel topoisomerase inhibitor effective in cells overexpressing drug efflux transporters

Background

Natural product structures have high chemical diversity and are attractive as lead structures for discovery of new drugs. One of the disease areas where natural products are most frequently used as therapeutics is oncology.

Method and Findings

A library of natural products (NCI Natural Product set) was screened for compounds that induce apoptosis of HCT116 colon carcinoma cells using an assay that measures an endogenous caspase-cleavage product. One of the apoptosis-inducing compounds identified in the screen was thaspine (taspine), an alkaloid from the South American tree Croton lechleri. The cortex of this tree is used for medicinal purposes by tribes in the Amazonas basin. Thaspine was found to induce conformational activation of the pro-apoptotic proteins Bak and Bax, mitochondrial cytochrome c release and mitochondrial membrane permeabilization in HCT116 cells. Analysis of the gene expression signature of thaspine-treated cells suggested that thaspine is a topoisomerase inhibitor. Inhibition of both topoisomerase I and II was observed using in vitro assays, and thaspine was found to have a reduced cytotoxic effect on a cell line with a mutated topoisomerase II enzyme. Interestingly, in contrast to the topoisomerase II inhibitors doxorubicin, etoposide and mitoxantrone, thaspine was cytotoxic to cell lines overexpressing the PgP or MRP drug efflux transporters. We finally show that thaspine induces wide-spread apoptosis in colon carcinoma multicellular spheroids and that apoptosis is induced in two xenograft mouse models in vivo.

Conclusions

The alkaloid thaspine from the cortex of Croton lechleri is a dual topoisomerase inhibitor effective in cells overexpressing drug efflux transporters and induces wide-spread apoptosis in multicellular spheroids.

Safety and efficacy of NAD depleting cancer drugs: results of a phase I clinical trial of CHS 828 and overview of published data

PURPOSE

Depletion of cellular nicotinamide adenine dinucleotide (NAD) by inhibition of its synthesis is a new pharmacological principle for cancer treatment currently in early phases of clinical development. We present new and previously published data on the safety and efficacy of these drugs based on early clinical trials.

METHODS

A phase I clinical trial of CHS 828 in patients with advanced solid tumours was performed. Published clinical trials on NAD depleting drugs for cancer treatment were summarised for safety and efficacy.

RESULTS

Seven patients with previously treated solid tumours received oral administration of CHS 828 in the dose range 20-80 mg once weekly for 3 weeks in 4 weeks cycles. Toxicity was dominated by gastrointestinal symptoms including nausea, vomiting, diarrhoea, constipation, subileus and gastric ulcer. One patient had thrombocytopenia grade 2. There were two cases each of grade 3-4 hyperuricemia and hypokalemia. Safety and efficacy of the NAD depleting drugs CHS 828 and FK866 have been reported from four phase I clinical trials, including a total of 97 patients with previously treated solid tumours. Outstanding toxicity reported was thrombocytopenia and various gastrointestinal symptoms. No objective tumour remission has been observed in the total of 104 patients treated in the above early trials.

CONCLUSIONS

Critical toxicity from NAD depleting cancer drugs to consider in future trials seems to be thrombocytopenia and various gastrointestinal symptoms. Efficacy of NAD depleting drugs when used alone is expected to be low.

Targeted drugs in metastatic colorectal cancer with special emphasis on guidelines for the use of bevacizumab and cetuximab: an Acta Oncologica expert report

From having been a 'single-drug not very interesting cancer type' from a medical treatment perspective, treatment of colorectal cancer (CRC) has during the past five years become a more complex issue of the appropriate use of several cytotoxic drugs sometimes integrated with advanced metastatic surgery with curative intent. The new drugs have provided significant benefit to the patients, so far mostly in the metastatic setting but also in adjuvant treatment. The significant progress in molecular and tumour biology has produced a great number of new 'targeted' drugs that are now in various stages of clinical development. Two of these drugs, the monoclonal antibodies bevacizumab (Avastin) and cetuximab (Erbitux), directed against VEGF and EGFR, respectively, have recently been approved within the EU for use in metastatic CRC. This Nordic Expert Consensus Report summarizes the current status of chemotherapy in metastatic CRC, overviews the clinical status of targeted drugs in CRC and, finally, provides guidelines for the routine clinical use of bevacizumab and cetuximab based on the most recently available clinical data.

Characterization of the cytotoxic activity of the indoloquinoline alkaloid cryptolepine in human tumour cell lines and primary cultures of tumour cells from patients

The plant derived indoloquinoline alkaloid cryptolepine was investigated for its cytotoxic properties in 12 human tumour cell lines and in primary cultures of tumour cells from patients. The fluorometric microculture cytotoxicity assay was used to assess cytotoxicity and DNA micro-array analysis to evaluate gene expression. Cryptolepine mean IC(50) in the cell line panel was 0.9 microM compared with 1.0 and 2.8 microM in haematological and solid tumour malignancies, respectively. Among patient solid tumour samples, those from breast cancer were the most sensitive and essentially as sensitive as haematological malignancies. Cryptolepine activity showed highest correlations to topoisomerase II and microtubule targeting drugs. In the cell lines cryptolepine activity was essentially unaffected by established mechanisms of drug resistance. A number of genes were identified as associated with cryptolepine activity. In conclusion, cryptolepine shows interesting in vitro cytotoxic properties and its further evaluation as an anti-cancer drug seems warranted.

Target specificity and off-target effects as determinants of cancer drug efficacy

Targeted therapeutics are aimed to hit one or a few key cellular targets. Agents that target single signaling molecules (such as EGFR and IGF-R1) often show limited clinical activities, at least in the major groups of solid tumors. Nevertheless, some signaling inhibitors are effective in the treatment of previously difficult-to-treat diseases such as renal carcinoma. Similarly, these drugs inhibit multiple kinases and/or may display off-target activities. Inhibition of cellular targets such as the proteasome, heat-shock protein 90, and histone deacetylase induces complex cellular effects, and agents that inhibit these targets show promising clinical activities. Clinically effective targeted agents are therefore reminiscent of conventional agents such as cisplatin and doxorubicin, which are known to have several cellular targets. It is becoming increasingly clear that a comprehensive understanding of the spectrum of effects exerted by an anticancer agent is fundamental for understanding its efficacy and toxicity profile.

Intravesical treatments of bladder cancer: review

For bladder cancer, intravesical chemo/immunotherapy is widely used as adjuvant therapies after surgical transurethal resection, while systemic therapy is typically reserved for higher stage, muscle-invading, or metastatic diseases. The goal of intravesical therapy is to eradicate existing or residual tumors through direct cytoablation or immunostimulation. The unique properties of the urinary bladder render it a fertile ground for evaluating additional novel experimental approaches to regional therapy, including iontophoresis/electrophoresis, local hyperthermia, co-administration of permeation enhancers, bioadhesive carriers, magnetic-targeted particles and gene therapy. Furthermore, due to its unique anatomical properties, the drug concentration-time profiles in various layers of bladder tissues during and after intravesical therapy can be described by mathematical models comprised of drug disposition and transport kinetic parameters. The drug delivery data, in turn, can be combined with the effective drug exposure to infer treatment efficacy and thereby assists the selection of optimal regimens. To our knowledge, intravesical therapy of bladder cancer represents the first example where computational pharmacological approach was used to design, and successfully predicted the outcome of, a randomized phase III trial (using mitomycin C). This review summarizes the pharmacological principles and the current status of intravesical therapy, and the application of computation to optimize the drug delivery to target sites and the treatment efficacy.

Quantitative image analysis of intra-tumoral bFGF level as a molecular marker of paclitaxel resistance

Background

The role of basic fibroblast growth factor (bFGF) in chemoresistance is controversial; some studies showed a relationship between higher bFGF level and chemoresistance while other studies showed the opposite finding. The goal of the present study was to quantify bFGF levels in archived tumor tissues, and to determine its relationship with chemosensitivity.

Methods

We established an image analysis-based method to quantify and convert the immunostaining intensity of intra-tumor bFGF to concentrations; this was accomplished by generating standard curves using human xenograft tumors as the renewable tissue source for simultaneous image analysis and ELISA. The relationships between bFGF concentrations and tumor chemosensitivity of patient tumors (n = 87) to paclitaxel were evaluated using linear regression analysis.

Results

The image analysis results were compared to our previous results obtained using a conventional, semi-quantitative visual scoring method. While both analyses indicated an inverse relationship between bFGF level and tumor sensitivity to paclitaxel, the image analysis method, by providing bFGF levels in individual tumors and therefore more data points (87 numerical values as opposed to four groups of staining intensities), further enabled the quantitative analysis of the relationship in subgroups of tumors with different pathobiological properties. The results show significant correlation between bFGF level and tumor sensitivity to the antiproliferation effect, but not the apoptotic effect, of paclitaxel. We further found stronger correlations of bFGF level and paclitaxel sensitivity in four tumor subgroups (high stage, positive p53 staining, negative aFGF staining, containing higher-than-median bFGF level), compared to all other groups. These findings suggest that the relationship between intra-tumoral bFGF level and paclitaxel sensitivity was context-dependent, which may explain the previous contradictory findings on the merit of using plasma or urine bFGF level as a prognostic indicator.

Conclusion

The present study established a quantitative image analysis method that enabled the measurement of intratumoral bFGF level in archived tissues. The ability to quantify a potential biomarker provided the opportunity to study the relationship between the biomarker and chemosensitivity in tumor subgroups and thereby enabled hypothesis generation for additional translational research.

Synthesis of Functional “Top-Half” Partial Structures of Azinomycin A and B

The design and synthesis of a detailed series of functional "top-half" substructures of azinomycin A and B is described.

Imatinib mesylate reduces production of extracellular matrix and prevents development of experimental dermal fibrosis

OBJECTIVE

Imatinib mesylate is a clinically well-tolerated small molecule inhibitor that exerts selective, dual inhibition of the transforming growth factor beta (TGFbeta) and platelet-derived growth factor (PDGF) pathways. This study was undertaken to test the potential use of imatinib mesylate as an antifibrotic drug for the treatment of dermal fibrosis in systemic sclerosis (SSc).

METHODS

The expression of extracellular matrix (ECM) proteins in SSc and normal dermal fibroblasts was analyzed by real-time polymerase chain reaction, Western blot, and Sircol collagen assay. Proliferation capacity was assessed with the MTT assay. Cell viability was analyzed by mitochondrial membrane potential and by annexin V/propidium iodide staining. Bleomycin-induced experimental dermal fibrosis was used to assess the antifibrotic effects of imatinib mesylate in vivo.

RESULTS

Imatinib mesylate efficiently reduced basal synthesis of COL1A1, COL1A2, and fibronectin 1 messenger RNA in SSc and normal dermal fibroblasts, in a dose-dependent manner. The induction of ECM proteins after stimulation with TGFbeta and PDGF was also strongly and dose-dependently inhibited by imatinib mesylate. These results were confirmed at the protein level. Imatinib mesylate did not alter proliferation or induce apoptosis and necrosis in dermal fibroblasts. Consistent with the in vitro findings, imatinib mesylate reduced dermal thickness, the number of myofibroblasts, and synthesis of ECM proteins in experimental dermal fibrosis, without evidence of toxic side effects.

CONCLUSION

These data show that imatinib mesylate at biologically relevant concentrations has potent antifibrotic effects in vitro and in vivo, without toxic side effects. Considering its favorable pharmacokinetics and clinical experience with its use in other diseases, imatinib mesylate is a promising candidate for the treatment of fibrotic diseases such as SSc.

The new era in the treatment of advanced colorectal cancer patients: the role of monoclonal antibodies

Colorectal cancer (CRC) represents a major health problem in the Western world. Approximately 60% of patients with CRC require systemic therapy for metastatic disease, either at diagnosis or at disease recurrence. Until recently, classic chemotherapeutic agents have been combined in the treatment of advanced CRC. The recent considerable development of novel monoclonal antibodies that target key components of biological pathways has expanded the options to treat advanced CRC patients. These newer agents more specifically target unique features of the cancer cell and its surroundings and so attempt to exploit the progress that has been made in the understanding of basic cell biology. Two targets in particular--the process of new blood vessel development, or angiogenesis, and the EGF receptor and its signalling pathway--are exploited by the newest monoclonal antibodies available for use in this setting. This clinical review focuses on the defining role of the two most clinically advanced novel agents, bevacizumab and cetuximab in metastatic colorectal cancer.

Is translational research compatible with preclinical publication strategies?

The term "translational research" is used to describe the transfer of basic biological knowledge into practical medicine, a process necessary for motivation of public spending. In the area of cancer therapeutics, it is becoming increasingly evident that results obtained in vitro and in animal models are difficult to translate into clinical medicine. We here argue that a number of factors contribute to making the translation process inefficient. These factors include the use of sensitive cell lines and fast growing experimental tumors as targets for novel therapies, and the use of unrealistic drug concentrations and radiation doses. We also argue that aggressive interpretation of data, successful in hypothesis-building biological research, does not form a solid base for development of clinically useful treatment modalities. We question whether "clean" results obtained in simplified models, expected for publication in high-impact journals, represent solid foundations for improved treatment of patients. Open-access journals such as Radiation Oncology have a large mission to fulfill by publishing relevant data to be used for making actual progress in translational cancer research.

Childhood acute lymphoblastic leukaemia and relapse

Acute lymphoblastic leukaemia (ALL) is the most common childhood cancer. Treatment has improved but relapsed ALL remains more common than new cases of many 'common' paediatric malignancies. We have salvage regimens with substantial complete remission (CR) rates and increasing access to haematopoietic stem cell transplantation, but most patients who relapse die. We need better therapies. Insights into pharmacology may guide more effective use of existing agents. Novel agents with activity against resistant lymphoblasts offer an appealing strategy. However, most candidate agents fail, despite enthusiastic investigators, intriguing mechanisms of action and 'compelling' preclinical data. A number of existing combinations provide a 40% complete response rate in second or third relapse. Yet survival in third remission is <10%. Novel agents must, most likely, be integrated into multiagent combinations that provide a higher CR rate or better quality CR's than our conventional combinations in order to contribute substantially to cure. The march from bench to bedside requires careful consideration of the intermediate steps.

Screening for apoptosis???classical and emerging techniques

There has been a rapid development of cell-based assays and screening methods to identify promising apoptosis-inducing drug candidates for the treatment of cancer. Distinguishing between the complex processes involved in apoptosis and other forms of cell death requires information on both biochemical and morphological processes in the cell. Traditionally, many assays have been limited to measuring, for example, caspase activity using fluorogenic substrates. However, these screening assays provide only limited information on the complex processes involved in apoptosis. In this review we describe some of the available apoptosis assays amenable to high-throughput screening. In particular, image-based high-content screening assays to evaluate multiple biochemical and morphological parameters in apoptotic cells are described. Through combining the imaging of cells in microtiter plates with powerful image analysis algorithms, one can acquire deeper knowledge on multiple biochemical or morphological pathways at the single-cell level at an early stage in the development of novel anti-cancer drugs.

Predictive value of in vitro assessment of cytotoxic drug activity in advanced breast cancer

The predictive value of a short-term in vitro total cell kill assay was investigated in 37 patients with breast cancer (BC). Tumor cells were prepared from tumor samples from 17 patients with locally advanced and 20 with metastatic BC, which were treated with the FEC (5-fluorouracil, epirubicin, cyclophosphamide) regimen or a combination of epirubicin and taxane. The cells were then tested in the fluorometric microculture cytotoxicity assay (FMCA), which is based on the conversion by viable cells of fluorescein diacetate to fluorescent fluorescein, for sensitivity to the drugs given in vivo. The FMCA data were scored as low, intermediate or extreme drug resistance based on the median cell survival +/- SD for each drug and patient subset. The drug classification for each sample was then correlated to clinical outcome in terms of objective response and time to tumor progression. The FMCA significantly predicted objective tumor response with a sensitivity of 89% and a specificity of 53%. Furthermore, in patients with locally advanced BC, low drug resistance was significantly associated with longer time to progression. It is concluded that the FMCA seems to report clinically relevant cytotoxic drug sensitivity data in BC. The potential clinical role of the FMCA and similar tests is discussed.

In vitro assays for anticancer drug discovery--a novel approach based on engineered mammalian cell lines

Despite decisive progress in understanding the molecular biology of cancer development, cytotoxic anticancer drugs continue to be the cornerstone of modern antitumor therapies. The developmental therapeutics program, initiated by the US National Institutes of Health's National Cancer Institute in the early 1990s, pioneered massive-scale screening for agents able to phenotypically interfere with the growth and viability of neoplastic cell lines derived from a representative panel of human carcinogenic tissues. Capitalizing on advanced knowledge of molecular processes particular for neoplastic cell characteristics, target-specific screening scenarios became since increasingly popular. With drug targets defined, natural and synthetic (combinatorial) compound/peptide/nucleic acid libraries available and the high-throughput screening technology of the systems' biology era in place, the quo vadis of anticancer drug discovery seems to be well determined. We review recent advances in cytotoxic anticancer drug assay design with emphasis on a novel mammalian cell-based anticancer drug finder technology for the discovery of cytotoxic drugs with fewer side-effects on non-dividing cells.

Comparison of the usefulness of the MTT, ATP, and calcein assays to predict the potency of cytotoxic agents in various human cancer cell lines

Cell viability assays are important tools in oncological research and clinical practice to assess the tumor cell sensitivity of individual patients. The purpose of this study was to demonstrate the comparability of 3 widely used assays (MTT, ATP, calcein assays) by principal component analysis. The study included 4 different cytostatics (cisplatin, docetaxel, doxorubicin, vinblastine) and 3 different human cancer cell lines (MCF-7, A2780, doxorubicin resistant A2780adr). Ninety-three percent of the total variance of all variables included in the principal component analysis (resulting from 3 cell lines and 3 assays) could be explained by 1 principal component. Factor loadings were > 0.937 except for the variable MTT-A2780adr, which was 0.872. These results indicate the similarity of the 3 assays. A 2nd principal component analysis included literature data and showed accordance of data from this study and the literature. The MTT assay was further improved as a high-throughput screening-capable assay. The ATP assay is able to detect effects of cytostatics already after 1 h incubation. The determination of resistance factors allowed to differentiate cytostatics into P-gp or non-P-gp substrates. In conclusion, this study provides improved microplate reader-based cell viability assays and sets a statistically solid basis for a future comparison of data obtained in different laboratories by any of the 3 assays.

The SH2 domain: versatile signaling module and pharmaceutical target

The Src homology 2 (SH2) domain is the most prevalent protein binding module that recognizes phosphotyrosine. This approximately 100-amino-acid domain is highly conserved structurally despite being found in a wide variety proteins. Depending on the nature of neighboring protein module(s), such as catalytic domains and other protein binding domains, SH2-containing proteins play many different roles in cellular protein tyrosine kinase (PTK) signaling pathways. Accumulating evidence indicates SH2 domains are highly versatile and exhibit considerable flexibility in how they bind to their ligands. To illustrate this functional versatility, we present three specific examples: the SAP, Cbl and SOCS families of SH2-containing proteins, which play key roles in immune responses, termination of PTK signaling, and cytokine responses. In addition, we highlight current progress in the development of SH2 domain inhibitors designed to antagonize or modulate PTK signaling in human disease. Inhibitors of the Grb2 and Src SH2 domains have been extensively studied, with the aim of targeting the Ras pathway and osteoclastic bone resorption, respectively. Despite formidable difficulties in drug design due to the lability and poor cell permeability of negatively charged phosphorylated SH2 ligands, a variety of structure-based strategies have been used to reduce the size, charge and peptide character of such ligands, leading to the development of high-affinity lead compounds with potent cellular activities. These studies have also led to new insights into molecular recognition by the SH2 domain.

Cancer genes and the pathways they control

The revolution in cancer research can be summed up in a single sentence: cancer is, in essence, a genetic disease. In the last decade, many important genes responsible for the genesis of various cancers have been discovered, their mutations precisely identified, and the pathways through which they act characterized. The purposes of this review are to highlight examples of progress in these areas, indicate where knowledge is scarce and point out fertile grounds for future investigation.

Isolation and structure assignments of rostratins A-D, cytotoxic disulfides produced by the marine-derived fungus Exserohilum rostratum

Four new cytotoxic disulfides, rostratins A-D (1-4), were isolated from the whole broth of the marine-derived fungus Exserohilum rostratum (Drechsler), a fungal strain found associated with a marine cyanobacterial mat. The structures of these cyclic dipeptides were established through chemical degradation and a variety of two-dimensional NMR techniques. The absolute configurations of the rostratins were determined by the modified Mosher method. In the case of the polyhydroxylated compound 1 and the mercaptol 4, regioselective acylation was achieved by modulating the reaction temperature while monitoring the progress of the reaction by 1H NMR. Rostratins A, B, C, and D showed in vitro cytotoxicity against human colon carcinoma (HCT-116) with IC50 values of 8.5, 1.9, 0.76, and 16.5 microg/mL, respectively.

Cancer metastasis therapeutic targets and drug discovery: emerging small-molecule protein kinase inhibitors

Cancer metastasis is a significant problem and a tremendous challenge to drug discovery relative to identifying key therapeutic targets as well as developing breakthrough medicines. Recent progress in unravelling the complex molecular circuitry of cancer metastasis, including receptors, intracellular proteins and genes, is highlighted. Furthermore, recent advances in drug discovery to provide novel proof-of-concept ligands, in vivo effective lead compounds and promising clinical candidates, are summarised. Such drug discovery efforts illustrate the integration of functional genomics, cell biology, structural biology, drug design, molecular/cellular screening and chemical diversity (e.g., small molecules, peptides/peptidomimetics, natural products, antisense, vaccines and antibodies). Promising therapeutic targets for cancer metastasis have been identified, including Src, focal adhesion kinase, the integrin receptor, the vascular endothelial growth factor receptor, the epidermal growth factor receptor, Her-2/neu, c-Met, Ras/Rac GTPases, Raf kinase, farnesyl diphosphate synthase (i.e., amino-bisphosphonate therapeutic target) and matrix metalloproteases within the context of their implicated functional roles in cancer growth, invasion, angiogenesis and survival at secondary sites. Clinical and preclinical drug discovery is described and emerging small-molecule inhibitors of protein kinases are highlighted.