Treatment Of Hormone-dependent Cancer Research Articles

Ferrozoles: Ferrocenyl derivatives of letrozole with dual effects as potent aromatase inhibitors and cytostatic agents.

In the treatment of hormone-dependent cancers, aromatase inhibitors (AI) are receiving increased attention due to some undesirable effects such as the risk of endometrial cancer and thromboembolism of SERMs (selective estrogen receptor modulators). Letrozole is the most active AI with 99% aromatase inhibition. Unfortunately, this compound also exhibits some adverse effects such as hot flashes and fibromyalgias. Therefore, there is an urgent need to explore new types of AIs that retain the same-or even increased-antitumor ability. Inspired by the letrozole structure, a set of new derivatives has been synthesized that include a ferrocenyl moiety and different heterocycles. The derivative that contains a benzimidazole ring, namely compound 6, exhibits a higher aromatase inhibitory activity than letrozole and it also shows potent cytostatic behavior when compared to other well-established aromatase inhibitors, as demonstrated by dose-response, cell cycle, apoptosis and time course experiments. Furthermore, 6 promotes the inhibition of cell growth in both an aromatase-dependent and -independent fashion, as indicated by the study of A549 and MCF7 cell lines. Molecular docking and molecular dynamics calculations on the interaction of 6 or letrozole with the aromatase binding site revealed that the ferrocene moiety increases the van der Waals and hydrophobic interactions, thus resulting in an increase in binding affinity. Furthermore, the iron atom of the ferrocene fragment can form a metal-acceptor interaction with a propionate fragment, and this results in a stronger coupling with the heme group-a possibility that is consistent with the strong aromatase inhibition of 6.

Structural dissection of 13-epiestrones based on the interaction with human Organic anion-transporting polypeptide, OATP2B1

Human OATP2B1 encoded by the SLCO2B1 gene is a multispecific transporter mediating the cellular uptake of large, organic molecules, including hormones, prostaglandins and bile acids. OATP2B1 is ubiquitously expressed in the human body, with highest expression levels in pharmacologically relevant barriers, like enterocytes, hepatocytes and endothelial cells of the blood-brain-barrier. In addition to its endogenous substrates, OATP2B1 also recognizes clinically applied drugs, such as statins, antivirals, antihistamines and chemotherapeutic agents and influences their pharmacokinetics. On the other hand, OATP2B1 is also overexpressed in various tumors. Considering that elevated hormone uptake by OATP2B1 results in increased cell proliferation of hormone dependent tumors (e.g. breast or prostate), inhibition of OATP2B1 can be a good strategy to inhibit the growth of these tumors.13-epiestrones represent a potential novel strategy in the treatment of hormone dependent cancers by the suppression of local estrogen production due to the inhibition of the key enzyme of estrone metabolism, 17ß-hydroxysteroid-dehydrogenase type 1 (HSD17ß1). Recently, we have demonstrated that various phosphonated 13-epiestrones are dual inhibitors also suppressing OATP2B1 function. In order to gain better insights into the molecular determinants of OATP2B1 13-epiestrone interaction we investigated the effect of C-2 and C-4 halogen or phenylalkynyl modified epiestrones on OATP2B1 transport function. Potent inhibitors (with EC50 values in the low micromolar range) as well as non-inhibitors of OATP2B1 function were identified. Based on the structure-activity relationship (SAR) of the various 13-epiestrone derivatives we could define structural elements important for OATP2B1 inhibition. Our results may help to understand the drug/inhibitor interaction profile of OATP2B1, and also may be a useful strategy to block steroid hormone entry into tumors.

Protective effect of lycopene against tamoxifen-induced hepatotoxicity in albino rats

Background: Tamoxifen citrate (TAM) is a drug of choice for the treatment of hormone-dependent breast cancer, but its use has been associated with frequent hepatotoxicity. Aim: This study evaluated the protective effect of lycopene (LYP) against hepatotoxicity induced by TAM in albino rats. Methods: Adult female albino rats (200–250 g) were divided into eight groups of n = 5. Group 1 (control) received normal saline (0.2mL) intraperitoneally (i.p.), daily for 7 days. Groups 2–4 were treated daily with LYP (10 mg/kg, 20 mg/kg, and 40 mg/kg) (i.p.) for 7 days, respectively. Group 5 was treated daily with TAM (45 mg/kg) i.p. for 7 days. Groups 6–8 were supplemented daily with LYP (10 mg/kg, 20 mg/kg, and 40 mg/kg) before treatment with TAM (45 mg/kg) i.p. for 7 days, respectively. At the end of treatment, the rats were anesthetized and blood samples were collected and assessed for serum markers of liver function. Liver samples were harvested for histology and biochemical assessments. Results: Significant (P

Development and Validation of HPLC-MS/MS Method for Busereline Quantitation in Animal Blood Plasma

Introduction. Busereline, being a synthetic gonadotropin-releasing hormone analog, is widely used for hormone-dependent cancer treatment (e.g. prostate cancer and breast cancer). Based on the accumulated scientific data for busereline quantitation in biosamples, the main analytical method that is used for this purpose is high-performance liquid chromatography (HPLC) with fluorescence detection, combined with protein precipitation (TCA 10%) for sample preparation. However, due to several limitations of this method resulting in low sensitivity (at the µg/mL level of concentrations), the HPLC-MS/MS analytical method was chosen for peptide determination in biosamples. The HPLC-MS/MS method is considered to have higher accuracy and specificity. The main sample preparation method for gonadotropin-releasing hormone analogs is solid-phase extraction. In our work, we’ve chosen protein precipitation as an alternative – easier and less laborious biosamples preparation process.Aim. The main objective of this study was the development and validation of HPLC-MS/MS method for busereline quantitation in animal (mini pigs) plasma samples and its further application to pharmacokinetic studies.Materials and methods. Busereline quantitative determination in plasma samples was performed using HPLC-MS/MS method. A protein precipitation procedure (methanol, 1:2, v/v) was used for busereline extraction from pig plasma.Results and discussion. The developed analytical method was validated for selectivity, linearity, matrix effect, accuracy (intra-day, inter-day), precision (intra-day, inter-day), LLOQ, carryover and stability.Conclusion. A new HPLC-MS/MS method for busereline quantitation in blood plasma was developed and successfully validated. The developed method showed linearity over the quantitation range from 1 to 20 ng/mL. The developed method can be successfully applied to busereline pharmacokinetic studies.

Steroid Receptor Signallings as Targets for Resveratrol Actions in Breast and Prostate Cancer.

Extensive research over the past 25 years in hormone-dependent cancers, such as breast cancer and prostate cancer, has identified the molecular mechanisms driven by steroid receptors, elucidating the interplay between genomic and non-genomic steroid receptors mechanism of action. Altogether, these mechanisms create the specific gene expression programs that contribute to endocrine therapy resistance and cancer progression. These findings, on the bidirectional molecular crosstalk between steroid and growth factor receptors pathways in endocrine resistance, suggest the use of multi-target inhibitors together with endocrine therapies, for treating resistant disease. In this review we will discuss the novel understanding on the chemopreventive and anti-cancer activities of Resveratrol (3,5,4′-trihydroxy-stilbene) (RSV), a phytoalexin found in grapes acting on a plethora of targets. We will highlight Resveratrol effect on steroid receptors signalling and its potential use in the treatment of hormone-dependent cancer. Understanding the molecular mechanisms by which the bioactive compound influences cancer cell behaviour, by interfering with steroid receptors functional activity, will help to advance the design of combination strategies to increase the rate of complete and durable clinical response in patients.

Synthesis, biological evaluation and structure-activity relationship studies of isoflavene based Mannich bases with potent anti-cancer activity.

Phenoxodiol, an analogue of the isoflavone natural product daidzein, is a potent anti-cancer agent that has been investigated for the treatment of hormone dependent cancers. This molecular scaffold was reacted with different primary amines and secondary amines under different Mannich conditions to yield either benzoxazine or aminomethyl substituted analogues. These processes enabled the generation of a diverse range of analogues that were required for structure-activity relationship (SAR) studies. The resulting Mannich bases exhibited prominent anti-proliferative effects against SHEP neuroblastoma and MDA-MB-231 breast adenocarcinoma cell lines. Further cytotoxicity studies against MRC-5 normal lung fibroblast cells showed that the isoflavene analogues were selective towards cancer cells.

Efficacies of aromatase inhibitors in the treatment of hormone dependent metastatic breast cancer in postmenopausal women: a report of 148 cases

To evaluate the clinical efficacies of aromatase inhibitors in the treatment of postmenopausal metastatic breast cancer. A total of 148 postmenopausal women (including bilateral ovariectomy) with hormone dependent metastatic breast cancer receiving aromatase inhibitors (letrozole, anastrozole or exemestane) were analyzed retrospectively. Their clinical efficacies were evaluated. The median progression-free survival (PFS) was 6.5 months and the clinical benefit rate 63.5%. And the rates of PFS of patients on first-line and second-line or above treatments were 9.0 (95% CI: 6.95-11.05) and 3.0 months (95% CI: 1.8-10.1) respectively. The clinical benefit rates of two groups were 74.2% and 26.3% respectively. Aromatase inhibitors are both efficacious and well-tolerated for patients of postmenopausal metastatic breast cancer. It may be recommended as a first-line therapy for postmenopausal women with hormone dependent metastatic breast cancer.

A novel synthetic luteinizing hormone-releasing hormone (LHRH) analogue coupled with modified β-cyclodextrin: Insight into its intramolecular interactions

BackgroundCyclodextrins (CDs) in combination with therapeutic proteins and other bioactive compounds have been proposed as candidates that show enhanced chemical and enzymatic stability, better absorption, slower plasma clearance and improved dose–response curves or immunogenicity. As a result, an important number of therapeutic complexes between cyclodextrins and bioactive compounds capable to control several diseases have been developed. ResultsIn this article, the synthesis and the structural study of a conjugate between a luteinizing hormone-releasing hormone (LHRH) analogue, related to the treatment of hormone dependent cancer and fertility, and modified β-cyclodextrin residue are presented. The results show that both the phenyl group of tyrosine (Tyr) as well as the indole group of tryptophan (Trp) can be encapsulated inside the cyclodextrin cavity. Solution NMR experiments provide evidence that these interactions take place intramolecularly and not intermolecularly. ConclusionsThe study of a LHRH analogue conjugated with modified β-cyclodextrin via high field NMR and MD experiments revealed the existence of intramolecular interactions that could lead to an improved drug delivery. General significanceNMR in combination with MD simulation is of great value for a successful rational design of peptide–cyclodextrin conjugates showing stability against enzymatic proteolysis and a better pharmacological profile.

Effect of Epilobium angustifolium and Serenoa repens extracts on regulation of non-genomic signaling pathway of kinases.

Changes of kinase activity of non-genomic cellular signaling pathway may influence the effectiveness of pharmacotherapy in case of hormone-dependent tumors. Our study investigated a possible interaction at the molecular level between an aqueous herbal extract of Epilobium angustifolium as well as a lipid-sterolic fruit extract of Serenoa repens and synthetic drugs used in the treatment of hormone-dependent cancers. E. angustifolium and Serenoa repens extracts were orally administered to testosterone-induced rats for 21 days. Changes of RafA/Mapk3/Mapk1 mRNA levels were analyzed by real-time quantitative PCR using target specific primers. The level of RafA mRNA slightly increased in rats receiving Epilobium angustifolium (p = 0.076) and Serenoa repens (p = 0.016) extracts. Administration of these extracts resulted in significantly elevated Mapk1 and Mapk3 transcripts in the investigated animals (p < 0.05 for each extract). The levels of Mapk1 and Mapk3 mRNA strongly increased (p < 0.05 for each extract) in animals receiving concomitantly testosterone and the extracts, while RafA transcription slightly decreased (p < 0.05), as compared to controls. The results of our study may indicate a potential effect of S. repens and E. angustifolium extracts on the functioning of non-genomic cellular signaling kinases pathway. We investigated safety of these extracts to detect possible drug interactions between synthetic drugs used in the treatment of proliferative changes in hormone-dependent reproductive organs and herbal preparations.

Physical transformations of the active pharmaceutical ingredient BN83495: enantiotropic and monotropic relationships. Access to several polymorphic forms by using various solvation–desolvation processes

BN83495 is an API in development, used in the treatment of hormone dependent cancers. This molecule exhibits an interesting polymorphic landscape consisting of three polymorphic forms (I, II, and III), three 〈1:1〉 DMSO solvate polymorphs, and one 1,4-dioxane hemi-solvate. Among the three DMSO solvates, one can only be obtained in the presence of an inorganic impurity: the letovicite. Between the two polymorphic forms I and III, an enantiotropic transition has been highlighted. This solid–solid transition (Form I → Form III) seems to be controlled by the mosaicity of the particles, where both polymorphic form domains cohabit and this could remain unchanged for months. The reverse transition has not been detected in the solid state; slurrying in a solvent appears necessary to return to Form I. Each of the three polymorphs can be obtained by soaking in cold water the appropriate solvated compound. The crystal structure of each phase was determined from single crystal X-ray diffraction, except for Form II (the monotropic form under normal pressure). The analyses of the starting and final crystal structures involved in a desolvation process led to the proposal of mechanisms with and without transmission of structural information from the mother phase (i.e. the initial solvate) to the daughter phase. The presence of direct hydrogen bonds between BN83495 molecules in DMSO-I and 1,4-dioxane hemi-solvate seems to ensure the structural filiations during the desolvation mechanisms leading respectively to Form III and Form II.

Steroid sulfatase inhibitors for estrogen- and androgen-dependent cancers

Estrogens and androgens are instrumental in the maturation of many hormone-dependent cancers. Consequently, the enzymes involved in their synthesis are cancer therapy targets. One such enzyme, steroid sulfatase (STS), hydrolyses estrone sulfate, and dehydroepiandrosterone sulfate to estrone and dehydroepiandrosterone respectively. These are the precursors to the formation of biologically active estradiol and androstenediol. This review focuses on three aspects of STS inhibitors: 1) chemical development, 2) biological activity, and 3) clinical trials. The aim is to discuss the importance of estrogens and androgens in many cancers, the developmental history of STS inhibitor synthesis, the potency of these compounds in vitro and in vivo and where we currently stand in regards to clinical trials for these drugs. STS inhibitors are likely to play an important future role in the treatment of hormone-dependent cancers. Novel in vivo models have been developed that allow pre-clinical testing of inhibitors and the identification of lead clinical candidates. Phase I/II clinical trials in postmenopausal women with breast cancer have been completed and other trials in patients with hormone-dependent prostate and endometrial cancer are currently active. Potent STS inhibitors should become therapeutically valuable in hormone-dependent cancers and other non-oncological conditions.

Modeling of diarylalkyl‐imidazole and diarylalkyl‐triazole derivatives as potent aromatase inhibitors for treatment of hormone‐dependent cancer

Aromatase is an enzyme that catalyzes the final step in the conversion of androgen to estrogen. It has become an attractive target for the treatment of estrogen responsive breast cancer. The study has been focused on designing aromatase inhibitors (AIs) that can be selected as probable drug candidate for the treatment of breast cancer. In the present study, long chain diarylalkyl-imidazole and -triazole scaffolds have been considered for exploring pharmacophores as potent AIs using QSAR (Quantitative SAR) and pharmacophore mapping studies. The model generated in linear free energy QSAR study (R(2) = 0.905, Q(2)= 0.885, R(2)(pred(ts)) = 0.763) showed the importance of hydrophobicity, size and shape of the molecule, van der Waals surface and hydrogen atom contribution influence the activity. 3D QSAR of comparative molecular field analysis (CoMFA, R(2)= 0.921, Q(2) = 0.741, R(2)(pred(ts))= 0.583) showed that steric and electrostatic features along with hydrophobicity and electronic charge contribution at C(4) (Fig. 1) influence on the inhibitory activity. Comparative molecular similarity analysis (CoMSIA, R(2) = 0.874, Q(2) = 0.716, R(2)(pred(ts)) = 0.591) study adjudged the presence of steric, electrostatic and hydrophobic fields together with hydrogen bond (HB) donor and acceptor play significant role in inhibitory activity to aromatase enzyme. Further pharmacophore mapping study (Q(2) = 0.947, Delta(cost) = 113.171, R(2)(pred(ts)) = 0.857) suggested that presence of HB acceptor, hydrophobicity with aromatic ring, and the importance of steric contribution influence on the activity. The critical distances among the features are also important for the inhibitor activity.

Effects of zearalenone and α-Zearalenol in comparison with Raloxifene on T47D cells

Zearalenone (Zen) is a mycotoxin with estrogenic effect which contaminates cereals. In cell culture, Zen and its metabolite, α-Zearalenol (α-Zel), stimulate breast cancer cells growth. Today hormone-dependent cancers are important because of high incidence and death rate. Previous studies showed that Zen and α-Zel have an effect on hormone-dependent cancers. This study explains the effects of the mentioned compounds in comparison with Raloxifene as an anti-estrogen. Cell culture technique was used with MDA-MB-231 and T47D cells for evaluation of compounds. MDA-MB-231 cells were used as negative control and also for proving that treatment compounds merely affect, due to their proliferation activity in the applied doses. According to the Resazurine-based method, for toxicity assay, none of the test compounds have an effect on MDA-MB-231 cells but do effect the growth of T47D cells. Zen and α-Zel at low concentrations (10−8–10−9 M) stimulated T47D cell growth and Raloxifene strongly inhibited cell growth induced by Zen and α-Zel. There is a noticeable result in controlling diet of hormonal carcinogenic compounds and applying novel anti-estrogens for prevention and treatment of hormone-dependent cancers.

Development of hormone-dependent prostate cancer models for the evaluation of inhibitors of 17β-hydroxysteroid dehydrogenase Type 3

17beta-Hydroxysteroid dehydrogenases (17beta-HSDs) are responsible for the pre-receptor reduction/oxidation of steroids at the 17-position into active/inactive hormones, and the 15 known enzymes vary in their substrate specificity, localisation, and directional activity. 17beta-HSD Type 3 (17beta-HSD3) has been seen to be over-expressed in prostate cancer, and catalyses the reduction of androstenedione (Adione) to testosterone (T), which stimulates prostate tumour growth. Specific inhibitors of 17beta-HSD3 may have a role in the treatment of hormone-dependent prostate cancer and benign prostate hyperplasia, and also have potential as male anti-fertility agents. A 293-EBNA-based cell line with stable expression of transfected human 17beta-HSD3 was created and used to develop a whole cell radiometric TLC-based assay to assess the 17beta-HSD3 inhibitory potency of a series of compounds. STX2171 and STX2624 (IC(50) values in the 200-450nM range) were two of several active inhibitors identified. In similar TLC-based assays these compounds were found to be inactive against 17beta-HSD1 and 17beta-HSD2, indicating selectivity. A novel proof of concept model was developed to study the efficacy of the compounds in vitro using the androgen receptor positive hormone-dependent prostate cancer cell line, LNCaPwt, and its derivative, LNCaP[17beta-HSD3], transfected and selected for stable expression of 17beta-HSD3. The proliferation of the parental cell line was most efficiently stimulated by 5alpha-dihydrotestosterone (DHT), but the LNCaP[17beta-HSD3] cells were equally stimulated by Adione, indicating that 17beta-HSD3 efficiently converts Adione to T in this model. Adione-stimulated proliferation of LNCaP[17beta-HSD3] cells was inhibited in the presence of either STX2171 or STX2624. The compounds alone neither stimulated proliferation of the cells nor caused significant cell death, indicating that they are non-androgenic with low cytotoxicity. STX2171 inhibited Adione-stimulated growth of xenografts established from LNCaPwt cells in castrated mice in vivo. In conclusion, a primary screening assay and proof of concept model have been developed to study the efficacy of 17beta-HSD3 inhibitory compounds, which may have a role in the treatment of hormone-dependent cancer. Active compounds are selective for 17beta-HSD3 over 17beta-HSD1 and 17beta-HSD2, non-androgenic with low toxicity, and efficacious in both an in vitro proof of concept model and in an in vivo tumour model.

Aromatase inhibition by bioavailable methylated flavones

Previous studies have shown chrysin, 7-hydroxyflavone and 7,4′-dihydroxyflavone to be the most potent flavonoid inhibitors of aromatase. However, very poor oral bioavailability is a major limitation for the successful use of dietary flavonoids as chemopreventive agents. We have recently shown that methylated flavones, including 5,7-dimethoxyflavone, 7-methoxyflavone and 7,4′-dimethoxyflavone, are much more resistant to metabolism than their unmethylated analogs and have much higher intestinal absorption. In this study, we examined these fully methylated flavones as potential aromatase inhibitors for the prevention and/or treatment of hormone-dependent cancers. Whereas 5,7-dimethoxyflavone had poor effect compared to its unmethylated analog chrysin, 7-methoxyflavone and 7,4′-dimethoxyflavone were almost equipotent to their unmethylated analogs with IC 50 values of 2–9 μM. Thus, some fully methylated flavones appear to have great potential as cancer chemopreventive/chemotherapeutic agents.

Search for Potential Non-Steroidal Inhibitors of 17 &amp;#946;-Hydroxysteroid Dehydrogenase (17 &amp;#946;-HSD) in the Treatment of Hormone-Dependent Cancers

We report the search for non-steroidal inhibitors of 17β-hydroxysteroid dehydrogenase, in particular, for types 1 and 3. The results show that the synthesised compounds based on the biphenyl backbone were good inhibitors of 17β-HSD1, but were weak inhibitors of 17β-HSD3. The compounds were evaluated against 3β-HSD but showed weak inhibition.

Targeting Steroid Hormone Receptor Pathways in the Treatment of Hormone Dependent Cancers

Sex steroid hormones play a central role in the development and progression of prostate and breast cancers. The biological functions of these and other steroid hormones are mediated by a family of closely related steroid hormone receptors (SHRs), with the androgen receptor (AR) mediating the effects of testosterone and related androgens, and the classical estrogen receptor (ERalpha) mediating the effects of estradiol. Recent studies have begun to elucidate the complex pathways through which SHRs regulate gene expression, and their interaction with other cellular pathways. These studies have also begun to reveal molecular mechanisms underlying the diverse spectrum of effects mediated by steroid hormone analogues in different tissues. A major advance has been the finding that certain drugs induce unique conformational changes in SHRs that alter their interactions with transcriptional coactivator and corepressor proteins, resulting in cell type specific responses. These unique conformational changes appear responsible for the tissue specific effects of the selective estrogen receptor modulators (SERMs) in breast cancer. SHRs are clearly well established therapeutic targets in cancer, and drug development has continued to focus on agents that either block steroid hormone production or bind to and modulate their receptors. The identification of multiple proteins and pathways that mediate the downstream functions of SHRs may eventually provide additional therapeutic targets. This review outlines the basic biology of SHR structure and function, with a focus on AR and ERalpha. Hormonal therapies in prostate and breast cancer that directly target AR and ERalpha, respectively, are then presented and possible novel drug targets in the SHR pathway are discussed.

Steroid hormone receptors

Steroid receptors belong to a superfamily of hydrosoluble nuclear proteins which regulate transcription of a number of genes. In the absence of hormone, they are bound to proteins which maintain the receptors in an inactive state but prepared for binding with the hormone. In the presence of the hormone, the receptor is activated, which is reflected by modification of its physico-chemical constants and dissociation of associated proteins. This hormone-receptor complex forms a homodimer and binds to DNA at the regulatory regions of the genes involved, which is termed "hormone response element". The receptors are constituted of 5 to 6 domains, each responsible for one or several functions. The hormone binding domain (region E) and DNA binding domain (region C) are the most highly conserved. Progress in the comprehension of the mechanism of action of these receptors has led to the development of antihormones which are important in the treatment of hormone-dependent cancer. With progress in molecular biology, it is now possible to detect mutants of the receptors or their absence in syndromes involving hormonal resistance.

Oncology in neuroimmunomodulation. What progress has been made?

In 1987 in Dubrovnik, Yugoslavia, N.H. Spector named a new discipline: Neuroimmunomodulation. R. Ader called this new discipline psychoneuroimmunomodulation when the major emphysis was on its behavioral aspects. Neuroimmunomodulation (NIM) is devoted to the study of the interactions at different morphologic and functional levels among the immune, nervous, and endocrine systems. In fact, this science is the modern manifestation of an old science: in the words of B.D. Jankovic (1987), "Neuroimmunomodulation is a modern reflection in neurosciences and immunosciences of the ideas and experience of philosophers and ingenious observers of ancient Egypt, Greece, China, India, and other civilizations that the mind is involved in the defense against diseases." Twelve years ago NIM was regarded by many conventional scientists almost as a form of witchcraft. Today it may be the fastest growing area of biomedical science research in the world. Important clinical applications will not be far behind. NIM research has also progressed in the field of oncology research. Topics such as treatment of hormone-dependent cancer with analogues of hypothalamic hormones, the role of opioids and T cells in cancer, stress-cancer-immune connections, the anticancer role of melatonin and cytokines, immunotherapy of cancer, and the role of psychotherapy in cancer patients represent some lines of research that have been or are being investigated by scientists. Some areas remain to be thoroughly investigated such as the influence of physical exercise (sports), music (classical or modern), and/or relaxation techniques (e.g. yoga) on the development of human cancer. This paper reviews the role of NIM in oncology and provides some perspectives for further research and development of clinical applications.

A novel inhibitor of cytochrome P450 BM3.

The cytochromes P450 are a ubiquitous superfamily of haemoproteins which catalyse the addition of single atoms of oxygen to a wide range of organic substrates (1). P450 enzymes participate in the metabolism of a large number of physiological compounds including steroids, eicosanoids and fatty acids. Numerous xenobiotics are also substrates for different P450 enzymes and many of these compounds may also serve as inducers or inhibitors of various P450 isoforms (2). In mammalian systems, much interest surrounds the involvement of the hepatic class II P450s in the processes of drug metabolism and activation of carcinogens (3). In bacteria and lower eukaryotes, attention is focused on the potential use of P450s for biotechnological purposes, such as the biodegradation of environmental pollutants and the hydroxylation of steroidal rings in the synthesis of glucocorticoids for use as anti-inflammatory agents (4). The inhibition of P450 isozymes has medical applications, including the blocking of steroid synthesis in the treatment of hormone-dependent cancers, and is of interest as a tool for study of their structure and function (5). A number of reversible and irreversible P450 inhibitors have been characterised, which act at different steps in the catalytic cycles of various P450 isozymes (6,7). We have discovered a novel inhibitor of cytochrome P450 BM3 from Bacillus megateriurn and are currently involved in work to determine its mode of action. P450 BM3 is a fatty acid hydroxylase with an unusually wide substrate selectivity range (8). It is soluble, catalytically self-sufficient and is the only known prokaryotic class II P450 (9). The enzyme has been recognised as the most experimentally amenable model system for the investigation of biochemical phenomena relating to its biomedically relevant mammalian counterparts (10). We have found that 2,2'azino-bis(3-ethylbenz-thiazoline-6-sulphonic acid) (ABTS) acts as quite a potent inhibitor of fatty acid linked NADPH oxidation by P450 BM3. ABTS is best known as the colour generating component in the widely used GOD-Perid method for blood glucose determination. Figure 1 shows the effect of addition of increasing quantities of ABTS to a system containing 98Opls buffer (20mM MOPS (pH 7.4) + IOOmM KCI), 5pIs P450 BM3 (1.87nmols), 5pIs of fatty acid (33pM) and lOpls of NADPH