Luteinizing hormone inhibits Fas-induced apoptosis in ovarian surface epithelial cell lines.

Gonadotrophins including LH have been suggested to play an important role in the etiology of epithelial ovarian cancers. The goal of the present study was to obtain more insight in the mechanism of gonadotrophin action on ovarian surface epithelium (OSE) cells. As the Fas system is known to be a major player in the regulation of the process of apoptosis in the ovary, we investigated whether LH interfered with Fas-induced apoptosis in the human OSE cancer cell lines HEY and Caov-3. Activation of Fas receptor by an agonistic anti-Fas receptor antibody induced apoptosis, as was evaluated by caspase-3 activation, poly(ADP-ribose) polymerase fragmentation, phosphatidylserine externalization and morphological changes characteristic of apoptosis. Co-treatment with LH reduced the number of apoptotic cells following activation of Fas in a transient manner, while LH by itself did not affect apoptosis or cell proliferation. The anti-apoptotic effect of LH could be mimicked by the membrane-permeable cAMP analog 8-(4-chlorophenylthio) cAMP (8-CPT-cAMP), and blocked by H89, a specific inhibitor of protein kinase A (PKA). In conclusion, these findings suggest that LH protects HEY cells against Fas-induced apoptosis through a signaling cascade involving PKA. Although it is plausible that in vivo LH might also enhance OSE tumor growth through inhibition of apoptosis, further research is necessary to confirm this hypothesis.

Irregularly shaped inclusion cysts display increased expression of Ki67, Fas, Fas ligand, and procaspase-3 but relatively little active caspase-3.

Human ovarian cancers are thought to arise from sequestered ovarian surface epithelial (OSE) cells that line the wall of inclusion cysts. Nevertheless, the early events toward neoplasia are not well understood. In this study, immunoreactivity for apoptotic proteins in human OSE of control and tumor ovarian sections was examined. Ki67, a marker for cell proliferation, was generally absent in the flat-to-cuboidal OSE cells on the ovarian surface and in regularly shaped inclusion cysts. Fas, Fas ligand, and caspase-3, components of the apoptotic pathway, were also largely absent. Ki67, Fas, Fas ligand, and procaspase-3 expression, though not active caspase-3 expression, was more frequently observed in epithelial cells lining irregularly shaped inclusion cysts, particularly in the columnar and Müllerian-like OSE cell types that resembled ovarian tumor OSE cells. Immunoreactivity for these factors as well as active caspase-3 was found frequently in ovarian tumors. We postulate that the appearance of the Fas system and its related proteins in sequestered columnar OSE cells of irregularly shaped inclusion cysts may contribute to balance cell growth with cell death, although little active caspase-3 expression was observed. Further studies are required to identify whether inhibition of apoptosis in inclusion cysts is an early event in ovarian carcinogenesis.

Heterologous expression of the avirulence gene product, NIP1, from the barley pathogen Rhynchosporium secalis.

NIP1, the product of the avirulence gene AvrRrs1 from Rhynchosporium secalis, a fungal pathogen of barley, is a small secreted cysteine-rich protein. This protein is essential for the specific recognition of the fungus by host plants carrying the complementary resistance gene Rrs1. Different heterologous expression systems were tested to produce sufficient quantities of NIP1 to allow its utilization in receptor identification and isolation. In addition, protein amounts higher than those produced in fungal cultures are required to determine its 3D structure and to analyze its interaction with a receptor. The most efficient method, the synthesis of a His-tag fusion protein in Escherichia coli combined with a refolding procedure, yielded up to 3 mg of recombinant NIP1 from a 1-liter bacterial culture. After removal of the His-tag, the recombinant protein showed the same physicochemical characteristics as the native NIP1 and, most importantly, full biological activity.