Extracellular matrix proteins and tumor angiogenesis.

Tumor development is a complex process that relies on interaction and communication between a number of cellular compartments. Much of the mass of a solid tumor is comprised of the stroma which is richly invested with extracellular matrix. Within this matrix are a host of matricellular proteins that regulate the expression and function of a myriad of proteins that regulate tumorigenic processes. One of the processes that is vital to tumor growth and progression is angiogenesis, or the formation of new blood vessels from preexisting vasculature. Within the extracellular matrix are structural proteins, a host of proteases, and resident pro- and antiangiogenic factors that control tumor angiogenesis in a tightly regulated fashion. This paper discusses the role that the extracellular matrix and ECM proteins play in the regulation of tumor angiogenesis.

The role of dysregulated glucose metabolism in epithelial ovarian cancer.

Epithelial ovarian cancer (EOC) is the most lethal gynecologic cancer and also one of the most poorly understood. Other health issues that are affecting women with increasing frequency are obesity and diabetes, which are associated with dysglycemia and increased blood glucose. The Warburg Effect describes the ability of fast-growing cancer cells to preferentially metabolize glucose via anaerobic glycolysis rather than oxidative phosphorylation. Recent epidemiological studies have suggested a role for hyperglycemia in the pathogenesis of a number of cancers. If hyperglycemia contributes to tumour growth and progression, then it is intuitive that antihyperglycemic drugs may also have an important antitumour role. Preliminary reports suggest that these drugs not only reduce available plasma glucose, but also have direct effects on cancer cell viability through modification of molecular energy-sensing pathways. This review investigates the effect that hyperglycemia may have on EOC and the potential of antihyperglycemic drugs as therapeutic adjuncts.

Effects of rosiglitazone on ovarian function and fertility in animals with reduced fertility following fetal and neonatal exposure to nicotine.

We have previously shown that in utero nicotine exposure causes impaired fertility, follicle immaturity, and ovarian dysfunction in adult female rat offspring. These characteristics overtly resemble the clinical profile of polycystic ovarian syndrome (PCOS) and recent studies have shown that thiazolidinediones such as rosiglitazone improve fertility in women with PCOS but the mechanism is not well defined. Our goal was to examine whether rosiglitazone would (1) ameliorate the altered ovarian physiology that occurs following fetal and neonatal exposure to nicotine and (2) to examine whether this could be due to normalization of ovarian vascularization. At weaning, offspring of nicotine-exposed dams were given either vehicle (NV) or rosiglitazone (3 mg kg(-1) day(-1); NR). Offspring of saline-exposed dams received vehicle (SV). Tissues were collected when the female offspring reached 26 weeks of age. NV animals had reduced granulosa cell proliferation and increased ovarian cell apoptosis. Treatment with rosiglitazone increased proliferation, and decreased apoptosis, compared NV animals. NV animals had decreased ovarian vascularity relative to controls, whereas NR animals had an intermediate level of ovarian vessel density. Moreover, ovaries from NV animals had decreased levels of the pro-angiogenic growth factors vascular endothelial growth factor (VEGF) and endocrine gland-derived VEGF both of which were increased with rosiglitazone treatment. Rosiglitazone reversed some of the nicotine effects in the ovary and increased ovarian vascularization, follicle maturation and improved oocyte competence. Rosiglitazone may be an important treatment option for PCOS and the present study provides a potential mechanism by which rosiglitazone may have beneficial effects on fertility in these patients.

Fetal and neonatal exposure to nicotine disrupts ovarian function and fertility in adult female rats.

Women born to mothers who smoked during pregnancy have been shown to have impaired fertility, although the mechanisms underlying this association are unknown. Nicotine administration in adult animals has adverse effects on the ovary and uterus; however, the effects of fetal exposure to nicotine on postnatal ovarian function have not been determined. The goal of this study was to assess the effect of fetal and neonatal exposure to nicotine on ovarian function and fertility of the offspring. Nulliparous female Wistar rats were given 1 mg.kg-1.d-1 nicotine bitartrate, subcutaneously for 14 d prior to mating, during pregnancy and throughout lactation until weaning. Measures of fertility, breeding success, and serum levels of ovarian steroid hormones in offspring were assessed at 4 and 6 mo of age. Fetal and neonatal exposure to nicotine significantly increased the time to pregnancy as the animals aged. Similarly, evidence of altered ovarian steroidogenesis including increased serum progesterone concentrations and a decreased estrogen:progesterone ratio was observed in 6-mo-old animals. We conclude that fetal and neonatal exposure to nicotine results in delayed ovarian dysfunction in adult female offspring.

Analysis of a C-methyltransferase gene (aviG1) involved in avilamycin biosynthesis in Streptomyces viridochromogenes Tü57 and complementation of a Saccharopolyspora erythraea eryBIII mutant by aviG1.

Streptomyces viridochromogenes Tü57 is the principal producer of avilamycin A. aviG1, a putative methyltransferase gene, was detected in the avilamycin biosynthetic gene cluster. To determine the function of aviG1, a targeted gene inactivation experiment was performed. The resulting chromosomal mutant, carrying an in-frame deletion in aviG1, was deficient in avilamycin production. aviG1 was used to complement an eryBIII mutant of the erythromycin A producer Saccharopolyspora erythraea [Gaisser, S., Bohm, G. A., Doumith, M., Raynal, M. C., Dhillon, N., Cortes, J. & Leadlay, P. F. (1998). Mol Gen Genet 258, 78-88]. The presence of erythromycin A in the culture supernatant of the complemented mutant indicated that L-mycarose biosynthesis could be restored and that AviG1 could take over the function of the C-methyltransferase EryBIII.

A defined system for hybrid macrolide biosynthesis in Saccharopolyspora erythraea.

The biological activity of polyketide antibiotics is often strongly dependent on the presence and type of deoxysugar residues attached to the aglycone core. A system is described here, based on the erythromycin-producing strain of Saccharopolyspora erythraea, for detection of hybrid glycoside formation, and this system has been used to demonstrate that an amino sugar characteristic of 14-membered macrolides (D-desosamine) can be efficiently attached to a 16-membered aglycone substrate. First, the S. erythraea mutant strain DM was created by deletion of both eryBV and eryCIII genes encoding the respective ery glycosyltransferase genes. The glycosyltransferase OleG2 from Streptomyces antibioticus, which transfers L-oleandrose, has recently been shown to transfer rhamnose to the oxygen at C-3 of erythronolide B and 6-deoxyerythronolide B. In full accordance with this finding, when oleG2 was expressed in S. erythraea DM, 3-O-rhamnosyl-erythronolide B and 3-O-rhamnosyl-6-deoxyerythronolide B were produced. Having thus validated the expression system, endogenous aglycone production was prevented by deletion of the polyketide synthase (eryA) genes from S. erythraea DM, creating the triple mutant SGT2. To examine the ability of the mycaminosyltransferase TylM2 from Streptomyces fradiae to utilise a different amino sugar, tylM2 was integrated into S. erythraea SGT2, and the resulting strain was fed with the 16-membered aglycone tylactone, the normal TylM2 substrate. A new hybrid glycoside was isolated in good yield and characterized as 5-O-desosaminyl-tylactone, indicating that TylM2 may be a useful glycosyltransferase for combinatorial biosynthesis. 5-O-glucosyl-tylactone was also obtained, showing that endogenous activated sugars and glycosyltransferases compete for aglycone in these cells.

Knowledge-based design of bimodular and trimodular polyketide synthases based on domain and module swaps: a route to simple statin analogues.

BACKGROUND: Polyketides are structurally diverse natural products that have a range of medically useful activities. Nonaromatic bacterial polyketides are synthesised on modular polyketide synthase (PKS) multienzymes, in which each cycle of chain extension requires a different 'module' of enzymatic activities. Attempts to design and construct modular PKSs that synthesise specified novel polyketides provide a particularly stringent test of our understanding of PKS structure and function. RESULTS: We have constructed bimodular and trimodular PKSs based on DEBS1-TE, a derivative of the erythromycin PKS that contains only modules 1 and 2 and a thioesterase (TE), by substituting multiple domains with appropriate counterparts derived from the rapamycin PKS. Hybrid PKSs were obtained that synthesised the predicted target triketide lactones, which are simple analogues of cholesterol-lowering statins. In constructing intermodular fusions, whether between modules in the same or in different proteins, it was found advantageous to preserve intact the acyl carrier protein-ketosynthase (ACP-KS) didomain that spans the junction between successive modules. CONCLUSIONS: Relatively simple considerations govern the construction of functional hybrid PKSs. Fusion sites should be chosen either in the surface-accessible linker regions between enzymatic domains, as previously revealed, or just inside the conserved margins of domains. The interaction of an ACP domain with the adjacent KS domain, whether on the same polyketide or not, is of particular importance, both through conservation of appropriate protein-protein interactions, and through optimising molecular recognition of the altered polyketide chain in the key transfer of the acyl chain from the ACP of one module to the KS of the downstream module.