Increasing evidence implicates a critical role for aberrant Ras function in promoting the development of human tumours and has provided the impetus for identifying anti-Ras drugs for therapy. In order to be active the protooncogene ras must be associated with the plasma membrane. This feature depends crucially upon its farnesylation (addition of a 15 carbon moiety) by the enzyme farnesyl protein transferase. In the search for new anticancer strategies and agents, potent and selective inhibitors of this enzyme have been designed. The more recent of these compounds have produced impressive results in vivo against human tumours xenografted onto nude mice, without notable toxicity, making them promising candidates for clinical evaluation.

Recent progress in the understanding of the physiopathology of asthma makes possible the revision of the objectives of treatment, to pass from short-term symptomatic control to a prolonged control of the illness. L'ICAM-1 is an excellent potential target for preventative treatment of asthma of viral origin. When there are agents available of both inhibiting histamine and positively regulating ICAM-1 there is no longer reason to use simple antihistamines.

The hypothalamic disorders of obesity include hyperphagia, a low central orthosympathetic tone (with reduced thermogenesis), vagal hyperinsulinism, low serotonin efficacy, a hyperactive hypothalamo-hypophyseal-adrenal axis, a hypoactive GHRH-GH-IGF axis and hypogonadism of central origin. Hyperlipogenesis, glucose intolerance and excessive gluconeogenesis are secondary features. Most frequently the hypothalamic ARC reacts poorly to the leptin hypersecreted by adipose tissue, so that the local synthesis of NPY is unchecked. Fortunately, two prostaglandins derived from dietary arachidonic acid bind fat cell PPAR gamma and hepatic PPAR alpha. Both nuclear proteins are phosphorylated through an insulin pathway, thereby inhibiting the expression of genes favoring obesity and stimulating that of genes accelerating fatty acid oxidation. The array of dietetic and pharmacologic tools considered today is analyzed.

Advances in medical oncology have been obtained with compounds having new structure/mechanism of action. Pharmaceutical research is largely focused on "prospective" targets identified by basic science such as the oncogenic signal transduction pathways. Ras proteins stand as converging targets that could be blocked by different approaches including inhibition of the isoprenylation of the proteins. Many academic institutions and pharmaceutical companies have embarked on the research of farnesyl transferase inhibitors. Two approaches have been developed: 1) random screening of compounds from natural/synthetic origin; 2) synthesis of compounds able to mimic the C-terminal tetrapeptidic "CAAX box" and to inhibit consequently the critical step of farnesylation. This peptidomimetic approach has been successfull since active and specific inhibitors of Ras proteins farnesylation have been synthesized in the nM range. However, several major drawbacks have been identified: in particular, most of the time, the preclinical evaluation has been done with biochemical and biological materials implicating the activated Ha-ras oncogene (very unfrequently activated in human tumors) instead of the activated Ki-ras oncogene which is the relevant target in human carcinomas. This has resulted in the selection of compounds with preferential activity on Ha-ras tumors. Nevertheless, evidence has been now generated that inhibition of farnesyl transferase of ras proteins can lead to significant experimental antitumor effects. The most convincing data are those obtained with the Merck inhibitor L739,749 which is able to cause tumor regressions of carcinomas in transgenic mice.

Oligonucleotides can be synthesized for specific regulation of gene expression within the living cell. The oligonucleotide acts either on messenger RNA (nonsense and ribozyme strategies) or on DNA (triple helix or antigene strategy). This pharmacological approache requires chemically modified oligonucleotides and appropriate vectors. Applications in gene therapy can also be developed using a DNA vector to produce regulator RNA (nonsense, ribozyme, antigene) within the same cells. Early clinical trials are being conducted to determine the therapeutic efficacy of these two approaches.

The significant relationship between hormone substitution therapy during menopause and reduced cardiovascular risk has been demonstrated in many studies. The beneficial effect of natural estrogens on plasma lipids has been questioned, accounting for no more than 25% of the vascular effect. Natural estrogens act on the vascular wall by favoring the penetration of potassium into the cell and stimulating synthesis of prostacycline synthetase and prostaglandin cyclooxygenase. Capacity for dilatation is partially restored and sensitivity to vasoconstrictor substances is reduced by increased synthesis of endothelium derived relaxing factor (EDRF). In addition to the endothelium-dependent mechanism, there is also an endothelium-independent mechanism due to the anti-calcium effect and endothelin antagonism. Thus natural estrogens increase vascular flow and reduce resistance. Besides the direct or indirect vascular effect, estrogens also have an anti-atherogenic effect resulting from a modulation of gene expression due to specific receptors situated on smooth muscle and endothelial cells. Indications for hormone substitution have been modified due to this better understanding of the different actions of natural estrogens. Patients with atheromatosis or hypertension are legitimate candidates.

Integrins belong to a large family of heterodimeric membrane glycoproteins which mediate cell-cell or cell-extracellular matrix interactions. These interactions could play a major role during the migration of tumor cells across the extracellular matrix and vascular endothelium and would thus appear to be a requisite for the metastatic process. Treatment of the Foss human melanoma cell line with LIF or OSM, two cytokines involved in acute-phase response, increased the expression of membrane alpha v beta 1 by 1.5-2 fold. The same phenomenon was observed on the SK-N-SH human neuroblastoma cell line. This modulation, which was inhibited by specific monoclonal antibodies against alpha v or beta 1 integrin subunits, was concomitant with improved tumor cell attachment to the fibronectin matrix. Similar results were obtained after TNF-alpha treatment. Our findings demonstrate the ability of LIF and OSM to modulate tumor cell capacity to adhere to the matrix component, suggesting a potential role for these cytokines in modulation of tumoral progression.

Calcium channel inhibitors, such as verapamil, have been identified as having the ability to modulate the multidrug-resistant (MDR) phenotype due to overexpression of P-glycoprotein (Pgp). We have studied the effect of verapamil on Pgp expression levels in a cell line originating from acute myeloblastic leukemia and resistant to adriamycin, K562/ADR. In this line, the addition of 15 microM verapamil in the culture medium gives a 3-fold decrease of Pgp expression after 72 hours of treatment. Similar results have been obtained for two other MDR cell lines, which suggest that this phenomenon is not specific of a single model. The level of mdr1 mRNAs is decreased in the presence of verapamil (with a maximum effect obtained at the 24th hour), which suggests that the mechanism of action of verapamil is transcriptional and/or post-transcriptional. We have also studied the effect of verapamil on the level of expression of mdr1 mRNAs in non-drug selected cells such as the HEL line (human acute myeloblastic leukemia) and the parental K562 line, which present a very low level of expression of Pgp, detectable only by PCR. In these lines, verapamil treatment has no effect on the level of expression of mdr1 mRNAs. The effect of verapamil is therefore restricted to drug-selected lines presenting high levels of Pgp expression. The impact of the negative regulation of Pgp expression on the MDR phenotype has been studied in the K562/ADR line. When the cells are treated for 72 h by verapamil, there is a decrease of resistance and an increase of intracellular accumulation of anticancer agents such as daunorubicin or vinblastine. Negative regulation of Pgp expression appears therefore as a possible strategy for MDR phenotype reversal. The effect of verapamil, whose molecular mechanism of action is being studied, could constitute a basis for this strategy.

We studied the early stages of gene amplification in a Chinese hamster cell line and we show that two distinct mechanisms can operate at a single locus. Both of them rely on an unequal segregation of gene copies at mitosis. We conclude that cycles of chromatid breakage, followed by fusion of sister chromatids devoid of a telomere that lead to further breaks in mitosis, have a key role in the coupling of gene amplification and genome remodeling. Rearrangements are first limited to a single chromosome but can then potentially spread to any additional chromosome. Occasionally, a sequence containing the selected gene can be looped out, generating a "double minute" and thus initiating an independent process of extrachromosomal amplification.

During amphibian embryogenesis, axis definition and the specification of the mesoderm and neural plate depend on cell interactions. These interactions are mediated by peptide growth factors and other diffusible molecules including retinoic acid (RA). Several genes encoding transcription factors are known to be immediate early or delayed early responses to the action of growth factors and retinoids in the embryo. By the criterion of cycloheximide (CHX) resistance, goosecoid (gsc), Xlim-1, Xbra, Mix.1, XFKH1/pintallavis/XFD1, and Xnot are immediate early response genes in mesoderm/induction. Among these, gsc, Xnot and XFKH1 are superinduced by CHX, suggesting that their regulation depends in part on rapid turnover of the mRNA. RA is known to induce Xlim-1 in Xenopus embryos and to lead to anterior malformations. We show that 9-cis RA, the ligand of the RXR receptor class, is more effective than all-trans RA in generating these biological effects.

Initially discovered as antiviral agents, the interferons (IFNs) proved to be a class of cytokines with multifunctional properties, including inhibition of cell growth and modulation of immune functions. A number of clinical trials were thus carried out in cancer and viral diseases, and IFN-alpha therapy was shown to have a wide range of indications in hematology and dermatology: B-cell malignancies (hairy cell leukemia, non-Hodgkin's lymphoma, multiple myeloma), myeloproliferations (chronic myeloid leukemia, thrombocytosis), cutaneous T lymphoma, basal-cell carcinoma, cutaneous squamous cell carcinoma, Kaposi's sarcoma. IFN therapy also showed efficacy in viral tumors (condyloma acuminatum and laryngeal papillomatosis) and chronic hepatitis B and C. The antitumoral action of IFN-alpha mainly involves its capacity to inhibit cell proliferation, partly via antagonistic effects on growth factors. The elucidation of IFN-alpha signalling pathway(s) leading to gene activation, a better understanding of the interactions between IFN-alpha and cytokine network, and the development of combination therapy with other biological treatments or chemotherapy should greatly improve the clinical use of IFNs.

The interaction of a ligand with its cognate receptor not only activates signal transduction pathways but also determines adaptive responses affecting key elements in these pathways, in particular the cell surface receptor. Such is the case for G protein-linked receptors, the expression and functional status of which are highly regulated. The regulatory mechanisms involved can be divided according to two distinct time frames, acute and chronic. In the short-term, posttranslational mechanisms alter the functional status of the elements without changing steady-state levels or gene expression. Protein phosphorylation plays a prominent role in these acute adaptive responses. Thus agonists promote phosphorylation and the desensitization of several G protein-linked receptors. And we have shown in the case of the dopamine D2 receptor that protein kinase C modulates receptor coupling to its G-protein. Longer-term regulation involves transcriptional (gene expression), posttranslational (mRNA stability), and posttranslational (protein phosphorylation) regulation of the turnover of the elements in the information transduction pathway. In the case of G protein-linked receptors, long-term regulation is often reflected in changes in steady-state levels of mRNA (which can be quantified by techniques such as northern blot analysis, solution hybridization or in-situ hybridization). For dopamine D2 receptors, prolonged administration of neuroleptic drugs induces an up-regulation of receptor mRNA in various brain regions, probably through an increase in gene transcription. Receptor-transduced extracellular stimuli are converted into long-term changes in gene expression through specific nuclear transcription factors.(ABSTRACT TRUNCATED AT 250 WORDS)

Flunisolide (FLU), beclomethasone dipropionate (BDP) and its pulmonary metabolites beclomethasone monopropionate (BMP) and beclomethasone (B) were studied in rat for: their relative binding affinity (RBA) for the 5 classes of steroid receptors, their in vitro glucocorticoid activity on rat thymocytes, their in vivo glucocorticoid activity by oral route. These compounds displayed a strong RBA for rat lung, thymus and liver glucocorticoid receptors (FLU > or = BMP > BDP > or = B). They were also shown to have a moderate RBA for both mineralocorticoid and progestin receptors, while being devoid of any binding to androgen and oestrogen receptors. On rat thymocytes FLU exhibited the highest glucocorticoid activity (FLU > B > or = BMP > BDP). In rat oral FLU displayed a strong glucocorticoid activity with a slight first-pass metabolism as opposed to what has been reported in human.

Retinoic acid is an exception amongst teratogenic agents: indeed, it not only interferes with morphogenesis, but it also alters positional values, which leads to the formation of additional structures. The latter effect, similar to that of homeotic mutations, which have been characterized in drosophila, is the most instructive way to study morphogenetic processes. Intramniotic injection of retinoic acid into 10-day-old chick embryos causes feather formation on the scales of the anterior side of tarsometatarsus. Likewise, when the upper-lip skin of 13.5-day mouse embryos is treated in vitro with retinoic acid, there is a development of mouse vibrissa hair buds into glands. The expression of retinoic acid nuclear receptors (RARs) has been studied by in situ hybridization during normal morphogenesis of hair vibrissa follicles as well as during retinoic acid-induced glandular metaplasia. During the normal development of hair follicle, only RAR alpha and RAR gamma genes are transcribed, whereas RAR beta gene expression remains undetected by the techniques used. Retinoic acid skin treatment brings about RAR beta expression in the dermis, leading to the formation of glomerular glands. Now, hair, gland, scale or feather differentiation implies dermal-epidermal interactions which have been extensively studied. However, little is known about the language of communication used by the two tissues. Even if the inductive role of the dermis seems dominant, the competence of the epidermis must not be neglected: the latter determines in some cases the type of cutaneous appendage which is formed.(ABSTRACT TRUNCATED AT 250 WORDS)

Prolonged administration of neuroleptic drugs increases the density of dopamine D2 receptors in several brain regions. We have recently shown that such treatment also raises dopamine D2 receptor mRNA levels in the striatum. To elucidate some of the initial events which lead to this upregulation, we studied the acute effects of dopamine D2 agonists and antagonists on the expression of c-jun and c-fos. A single injection I.P. of haloperidol (2 mg/kg) produced a rapid and transient increase in c-jun and c-fos mRNA in the rat striatum. This induction was specifically blocked by a D2 agonist (1 mg/kg quinelorane). In contrast, by itself quinelorane was without effect. These results show that dopamine D2 receptors inhibit the expression of a set of immediate early genes in the striatum, and these may be involved in the up-regulation of D2 mRNA upon prolonged neuroleptic treatment.

The mechanism of ornithine decarboxylase (ODC) induction by phorbol ester (TPA) has been studied in two permanent epithelial cell lines, a control (Ctr) and a Benzo (a) pyrene transformed line (BaP-tr); the degree of ODC gene expression (ODC-mRNA) was evaluated in comparison to the ODC activity. A small dose of TPA (4 x 10(-8) M) highly induced ODC activity in these cells. The induction levels differed however, corresponding respectively to 4:1 (induced: basal ODC) in Ctr cells and to 2:1 in BaP-tr cells. This difference reflected the variation of ODC gene expression; the ODC-mRNA induction was 6:1 in Ctr cells and 3:1 in BaP-tr cells. Repetitive TPA treatment decreased the ODC induction in these cells, as compared to that resulting from a single TPA treatment. Studies of ODC modulation were performed in presence of anti-inflammatory agents. In the two cell lines, Indomethacin (anti-cyclooxygenase) did not change the level of ODC induction by TPA. Nordihydroguaiaretic acid (NDGA, anti-lipoxygenase) inhibited this induced ODC. These results differed from that obtained in vivo in mouse skin. Dexamethasone (DXME, anti-phospholipase A2) showed different action according to treatment time. Used together with TPA (t0), DXME inhibited ODC induction by the carcinogen; with three hours delay after TPA (t3), DXME treatment stimulated ODC in the cells. This divergent action may be reproduced by Actinomycin D, while Cycloheximide only exhibited constant inhibition. Studies now in progress suggested that the inhibition of TPA induced ODC by DXME may reflect ODC gene repression, as for the stimulating effect it could be related to ODC post-transcriptional modulation, owing to the decrease of proteolytic action.