Activation of gonadotropin-releasing hormone (GnRH) receptors inhibits proliferation of transformed cells derived from reproductive tissues and in transfected cell lines. Hence, GnRH receptors represent a therapeutic target for direct action of GnRH analogues on certain proliferating cells. However, more cell biological data are required to develop this particular application of GnRH analogues. Therefore, we compared the effects of GnRH receptor activation in transfected HEK293 cells (HEK293 [SCL60] ) with transfected human ovarian cancer cell lines SKOV3 and EFO21, human hepatoblastoma HepG2 cells, and rat neuroblastoma B35 cells. Marked differences in receptor levels, magnitude of inositol phosphate generation, and dynamics of inositol phosphate turnover occurred in the different cells. Activation of GnRH receptors, expressed at high or moderate levels, inhibited the growth of HEK293 [SCL60] and B35 cells, respectively. Western blotting detected markers of apoptosis [cleaved poly(ADP-ribose) polymerase, caspase-9] in HEK293 [SCL60] and B35 following treatment with 100 nmol/L D-Trp 6 -GnRH

In the normal breast, hepatocyte growth factor (HGF) is primarily expressed by stromal cells, and stimulates in a paracrine manner epithelial cells expressing the HGF receptor (Met). In invasive human breast carcinomas, HGF and Met are frequently overexpressed, possibly establishing an autocrine HGF/Met loop that promotes tumour cell invasion. However, the mechanisms leading to autocrine HGF expression in carcinoma cells are not known. We previously demonstrated a cooperative effect between c-Src and Stat3 in the activation of HGF transcription in mammary carcinoma cells. The present report defines a novel Stat3 consensus site at nt À95 in the HGF promoter that is highly conserved in human and mouse, and is required for c-Src and Stat3 to activate HGF transcription in breast epithelial cells. DNA-protein binding studies demonstrated high affinity binding of a Stat3-containing complex to the nt À95 site. Endogenous Stat3 binding to this region of the HGF promoter in carcinoma cells expressing HGF was demonstrated using a chromatin immunoprecipitation assay. In addition, coexpression of Stat3 and activated c-Src caused increased expression of endogenous HGF mRNA and protein and marked cell scattering in breast epithelial cells. Our results delineate a novel c-Src/Stat3-dependent mechanism that regulates HGF promoter activity, and is linked to transformation of mammary epithelial cells.

The bivalve mollusc Corbula gibba (Olivi) is often regarded as an invasive weed species that forms monospecific stands in organically enriched hypoxic habitats. However, despite its status as a potential menace, surprisingly little is known about its basic biology, including its dispersal capacity. Measurement of the respiration rate of C. gibba revealed a respiratory demand of 3.12 µl O 2 h -1 and a respiratory quotient of 0.61, which suggests that C. gibba adopts a conservationist rather than exploitative mode of life. Examination of the hypoxic tolerance of C. gibba determined that adults could survive for > 34 d (LT 50 ≥ 34 d) and juveniles for > 30 d (LT 50 = 14 d), indicating that this species is well adapted to living in low oxygen habitats. Unusually, adults under hypoxia had a greater survival rate than control adults in normoxic conditions. Investigation of the salinity tolerance of C. gibba revealed that it could readily survive for 2 d at 0 to 16 psu, with increasing mortality for up to 10 d. In brackish seawater, survival was indistinguishable from that in normal seawater. Examination of the population genetics of 6 different populations of C. gibba separated over various spatial scales, using RAPD PCR methodology, determined that all populations were genetically distinct from each other, including populations separated by as little 5 km, although this may in part be due to the influence of a localised front. This suggests that the larval longevity and dispersal capacity of C. gibba is much less than has been previously considered. In light of all the results, it is concluded that instead of being an insidious pest species, C. gibba is more likely to be an inferior competitor, present in background numbers in normoxic habitats, and only becomes dominant when a system becomes hypoxic, thereby removing competitors and allowing C. gibba to flourish in the habitat to which it is adapted.

Engineered high-level GnRH receptor activation inhibits growth of a subset of papillomavirus-immortalized prostate cells. Elucidating mechanisms leading to clone-specific differences in cell surface GnRH receptor levels is a valuable next step in developing strategies to exploit prostate cell anti-proliferation using GnRH agonists.