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The dioxin/aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor responsive to both natural and man-made environmental compounds. AhR and its nuclear partner ARNT are expressed in the female reproductive tract in a variety of species and several indications suggest that the AhR might play a pivotal role in the physiology of reproduction. Furthermore, it appears to be the mediator of most, if not all, the adverse effects on reproduction of a group of highly potent environmental pollutants collectively called aryl hydrocarbons (AHs), including the highly toxic compound 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Although a large body of recent literature has implicated AhR in multiple signal transduction pathways, the mechanisms of action resulting in a wide spectrum of effects on female reproduction are largely unknown. Here we summarize the major types of molecular cross-talks that have been identified for the AhR and linked cell signaling pathways and that are relevant for the understanding of the role of this transcription factor in female reproduction.

Testicular descent as a prerequisite for the production of mature spermatozoa and normal external genitalia morphogenesis, and therefore facilitating copulation and internal fertilization, are essential developmental steps in reproduction of vertebrate species. Cryptorchidism, the failure of testis descent, and feminization of external genitalia in the male, usually in the form of hypospadias, in which the opening of the urethra occurs along the ventral aspect of the penis, are the most frequent pediatric complications. Thus, elucidating the molecular mechanisms involved in the regulation of testis descent and the formation of external genitalia merits a special focus. Natural and transgenic rodent models have demonstrated both morphogenic processes to be under the control of a plethora of genetic factors with complex time-, space-, and dose-restricted expression pattern. The review elucidates the molecular mechanisms involved in the regulation of testis descent and the formation of external genitalia and, wherever possible, assesses the differences between these rodent animal models and other mammalian species, including human.

The role of members of the insulin-like superfamily in human thyroid carcinoma is primarily unknown. Here we demonstrate the presence of RLN2 relaxin and relaxin receptor LGR7 in human papillary, follicular, and undifferentiated anaplastic thyroid carcinoma suggesting a specific involvement of relaxin-LGR7 signaling in thyroid carcinoma. Stable transfectants of the LGR7-positive human follicular thyroid carcinoma cell lines FTC-133 and FTC-238 that secrete bioactive proRLN2 revealed this hormone to act as a multifunctional endocrine factor in thyroid carcinoma cells. Although RLN2 did not act as a mitogen, it acted as an autocrine/paracrine factor and significantly increased anchorage-independent growth and thyroid carcinoma cell motility and invasiveness through elastin matrices. In recent years, the multifunctional peptide hormone relaxin has been identified as an important endocrine player in the reproductive tract, cardiovascular/neural systems, and oncology.1,2 The thyroid was once considered to be a relaxin target tissue with relaxin reported to increase thyroid weight, radioactive iodine uptake, and protein-bound iodination in rats.3,4 Likely because of the crude relaxin preparations used at the time, these results could not be confirmed. 5 No further investigations were reported thereafter using highly purified relaxin preparations to validate a potential role of relaxin in thyroid tissues and thyroid cell lines. Some 40 years later, the discovery of the G-protein-coupled relaxin-like receptors LGR7 and LGR8 revealed the presence of transcripts for both LGR7 (relaxin receptor) and LGR8 (INSL3/relaxin receptor) in the thyroid gland. 6 -8 Relaxin and the relaxin-like INSL3 have been shown to activate cAMP-dependent signaling pathways by binding to either LGR7 or LGR8. 8 -12 We recently demonstrated the expression and regulation of INSL3 and LGR8 transcripts in human thyroid carcinoma cell lines, identifying hyper-and neoplastic human thyrocytes as a new source and target of the actions of INSL3 and a novel INSL3 splice variant. 8,13 Although still primarily undefined, relaxin appears to have oncogenic potential in various organs and tissues, including the human thyroid.14 -17 Relaxin affects proliferation and differentiation of MCF-7 human carcinoma cells in a concentration-dependent manner 18 and can modify the extracellular matrix by affecting the expresSupported by the Deutsche Forschungsgemeinschaft (grants KL1249/5-1

The mevalonate (MEV) cascade is responsible for cholesterol biosynthesis and the formation of the intermediate metabolites geranylgeranylpyrophosphate (GGPP) and farnesylpyrophosphate (FPP) used in the prenylation of proteins. Here we show that the MEV cascade inhibitor simvastatin induced significant cell death in a wide range of human tumor cell lines, including glioblastoma, astrocytoma, neuroblastoma, lung adenocarcinoma, and breast cancer. Simvastatin induced apoptotic cell death via the intrinsic apoptotic pathway. In all cancer cell types tested, simvastatin-induced cell death was not rescued by cholesterol, but was dependent on GGPP- and FPP-depletion. We confirmed that simvastatin caused the translocation of the small Rho GTPases RhoA, Cdc42, and Rac1/2/3 from cell membranes to the cytosol in U251 (glioblastoma), A549 (lung adenocarcinoma) and MDA-MB-231(breast cancer). Simvastatin-induced Rho-GTP loading significantly increased in U251 cells which were reversed with MEV, FPP, GGPP. In contrast, simvastatin did not change Rho-GTP loading in A549 and MDA-MB-231. Inhibition of geranylgeranyltransferase I by GGTi-298, but not farnesyltransferase by FTi-277, induced significant cell death in U251, A549, and MDA-MB-231. These results indicate that MEV cascade inhibition by simvastatin induced the intrinsic apoptosis pathway via inhibition of Rho family prenylation and depletion of GGPP, in a variety of different human cancer cell lines.

The pathogenesis of endometriosis includes the proliferation of heterogeneous endometrial cells and their invasion into ectopic sites within the peritoneal cavity. This may be due to abnormalities of the eutopic endometrium itself, predisposing the cells to survive and implant ectopically. We investigated the applicability of 2-DE gels and peptide mass mapping to identify candidate endometrial proteins with a role in endometriosis. Despite the heterogeneous nature of endometrium, our results show that combining the analysis of 2-DE gels and peptide mass mapping yields consistent data. We identified dysregulated proteins in women with endometriosis which included: (i) molecular chaperones including heat shock protein 90 and annexin A2, (ii) proteins involved in cellular redox state, such as peroxiredoxin 2, (iii) proteins involved in protein and DNA formation/breakdown, including ribonucleoside-diphosphate reductase, prohibitin and prolyl 4-hydroxylase, and (iv) secreted proteins, such as apolipoprotein A1. These proteins have functions which suggest that they could play a role in the pathogenesis of endometriosis. This study demonstrated that 2-DE gel analysis and mass spectroscopic protein identification are suitable for the identification of proteins with candidate associations with endometriosis. These techniques should be used on a larger scale to identify endometriosis-related proteins, thus improving the understanding of this complex disease.

Temozolomide (TMZ) is a chemotherapy agent used to treat Grade IV astrocytoma, also known as glioblastoma (GBM). TMZ treatment causes DNA damage that results in tumor cell apoptosis and increases the survival rate of GBM patients. However, chemoresistance as a result of TMZ‐induced autophagy significantly reduces this anticancer effects over time. Statins are competitive inhibitors of HMG‐CoA reductase, the rate‐limiting enzyme of the mevalonate (MEV) cascade. Statins are best known for their cholesterol (CH)‐lowering effect. Long‐term consumption of statins, prior to and in parallel with other cancer therapeutic approaches, has been reported to increase the survival rate of patients with various forms of cancers. In this study, we investigated the potentiation of TMZ‐induced apoptosis by simvastatin (Simva) in human GBM cell lines and patient GBM cells, using cell monolayers and three‐dimensional cell culture systems. The incubation of cells with a combination of Simva and TMZ resulted in a significant increase in apoptotic cells compared to cells treated with TMZ alone. Incubation of cells with CH or MEV cascade intermediates failed to compensate the decrease in cell viability induced by the combined Simva and TMZ treatment. Simva treatment inhibited the autophagy flux induced by TMZ by blocking autophago‐lysosome formation. Our results suggest that Simva sensitizes GBM cells to TMZ‐induced cell death in a MEV cascade‐independent manner and identifies the inhibition of autophagosome‐lysosome fusion as a promising therapeutic strategy in the treatment of GBM.