Role of the hedgehog/patched signaling pathway in oncogenesis: a new polymorphism in the PTCH gene in ovarian fibroma

We compared the expression of target genes of Hedgehog/Patched signaling in ovarian fibromas and ovarian dermoids. We noted that high levels of SHH appear almost regularly, especially in dermoids, usually accompanied by increased expression of SMO. GLI overexpression does not coincide with that of PTCH. Loss of heterozygosity findings in the PTCH locus and increased expression of several genes in the pathway strongly suggest that the pathway is involved in both ovarian fibroma and dermoids.

Analysis of the PTCH1 signaling pathway in ovarian dermoids

Dermoids belong to the group of developmental cysts and arise from germ cells. Studies on these tumors may therefore increase our understanding of normal germ cell development within different environments and cell lines derived from these lesions may also constitute an important vehicle for studying neoplasia and differentiation. Recently, we investigated the status of the PTCH1 locus in a large set of sporadic non-inflammatory, developmental cystic lesions. Our data showed allelic loss of microsatellite markers in close vicinity to the PTCH1 locus in both odontogenic keratocysts and dentigerous cysts as well as in ovarian dermoid cysts (ODC). In this study, we closely examined the status of the PTCH1 gene in ODCs. Although about 25% of cysts demonstrated LOH at the PTCH1 locus, no nonsense or missense mutations in the coding region of PTCH1 were detected in genomic DNA isolated from any of the ODCs examined by direct sequencing. Staining with PTCH1 and GLI1 antibodies showed that proteins were present in virtually all epithelial linings, with variable staining intensity not correlated with LOH and generally weaker for GLI1. However, cDNA microarray analysis performed on cell lines derived from ODCs did not show any significant alteration in the expression of the analyzed target genes of PTCH1 signaling in any of the cell lines examined, except for CyclinD1 (and several other genes generally not associated with PTCH1 signaling).

Alterations in CDKN2A locus as potential indicator of melanoma predisposition in relatives of non-familial melanoma cases

AIM

To examine constitutional alterations of CDKN2A/p16INK4A locus as a potential indicator of melanoma predisposition among the first-degree relatives of patients with malignant melanoma.

METHOD

The study included eight families with a single member affected with melanoma. Members of the families were screened for allelic cosegregation with 9p21 region polymorphic markers IFNA, D9S126, and D9S104. The patient's tumors were screened for loss of heterozygosity (LOH) with the same markers, as well as for single strand conformational polymorphism (SSCP) variability of CDKN2A. In suspect cases, constitutional DNA was examined by SSCP and direct sequencing.

RESULTS

LOH was detected in four cases, and SSCP indicated variability in at least one CDKN2A exon in these tumor samples. In three of four LOH cases, the remaining allele cosegregated within the family, which was interpreted as a preliminary indicator of potential genetic predisposition. In one of these three families, we found constitutional CDKN2A mutations in the patient and one of the relatives. In the second family, only the patient had the constitutionally altered gene, whereas no constitutional CDKN2A alterations were detected in the third family. All significant mutations were different and had not been reported before.

CONCLUSION

We detected one case of melanoma predisposition among unaffected family members, which corresponded to statistical expectations for such a small number of screened families. Since constitutional mutations of CDKN2A exons have limited incidence, our stepwise approach seemed to be more informative and more affordable than straightforward CDKN2A sequencing of all subjects.

Embryotoxicity of magainin-2-amide and its enhancement by cyclodextrin, albumin, hydrogen peroxide and acidification

BACKGROUND

The channel-forming antimicrobial peptide, magainin-2-amide, interacts preferentially with negatively charged, non cholesterol-containing membranes, including those of sperm, oocytes and cells of pre-implantation embryos. Cyclodextrin and albumin remove membrane cholesterol and together with hydrogen peroxide (H2O2) are potential enhancers of embryotoxicity.

METHODS

Two-cell murine embryos were cultured in vitro with magainin-2-amide at a high effective concentration (250 microg/ml) and at subthreshold concentrations (166 and 200 microg/ml). Embryos treated with sub-threshold concentrations of magainin were additionally treated with cyclodextrin, bovine serum albumin or H2O2 or were cultured under acidified conditions. Cell viability was verified with propidium iodide and fluorescein diacetate.

RESULTS

The embryotoxic effect of magainin and H2O2 was dose- and time-dependent. Cyclodextrin, H2O2, acidification of the medium, and to a lesser extent albumin, enhanced the embryotoxicity of magainin at sub-threshold concentrations.

CONCLUSION

Magainin on its own is highly embryotoxic. Its embryotoxicity is enhanced by cyclodextrin, albumin, H2O2 and acidification. Thus, magainin which has antibacterial, antifungal and antiprotozoal activity may also have a potential role as a contraceptive agent. The harmful effects of various concentrations of the exogenous H2O2 on 2-cell stage mouse embryos are reported here, to the best of our knowledge, for the first time.

Characterisation of epithelial cell line from rat cornea

PURPOSE

Characterisation of RtCE-1 cells, newly established rat corneal epithelial cell line.

METHODS

Morphology of RtCE-1 cells was characterised by light and electron microscopy. Expression of cytokeratins was studied by polyacrylamide electrophoresis and Western blotting. Characterisation of RtCE-1 cells also included karyotype analysis and in vitro study of growth kinetics.

RESULTS

The line shows morphological similarities to normal corneal epithelium. The cells express cornea-specific cytokeratins. Karyotype analysis revealed that the cells are polyploid with modal number of chromosomes at passage 30 equalling 72 +/- 14. Growth of the line is partially dependent on EGF.

CONCLUSION

RtCE-1 cells may constitute a model for the evaluation of proliferation, function and differentiation of corneal epithelium in vitro.

Apoptosis induced in L1210 leukaemia cells by an inhibitor of the chymotrypsin-like activity of the proteasome

Of a number of factors involved in apoptosis, protease activity may play a crucial role. We show that N-benzyloxycarbonyl-Ile-Glu( O-t-butyl)-Ala-leucinal (PSI), a selective inhibitor of the chymotrypsin-like activity of the proteasome, induces massive apoptosis in murine leukaemia L1210 cells. At 50 nM concentration, PSI induces a block of cytokinesis, while higher concentrations (500 nM) cause S phase block and massive apoptosis. Z-Leu-leucinal, a specific calpain inhibitor, did not induce apoptosis. In contrast to previous reports, TNF-alpha did not enhance apoptosis when combined with PSI. Our results suggest that proteasome inhibitors may be considered as potential anti-neoplastic agents.

Fourier analysis of the nuclear and cytoplasmic shapes of living two-cell murine embryos

Living two-cell mouse embryos were flushed out from the oviduct 17, 24 and 36 hours after fertilization in order to obtain cells in the G1S, early G2 and late G2 phases of the second cell cycle. The nuclei of the living cells were stained with Hoechst 33342. The coordinates of the contour shapes of the entire cells (cellular contours) were registered by contour image processing with a TV camera coupled with a computer; the contours of the nuclei were computed by means of a digitizer coupled with the computer. Fourier analysis of the cellular and nuclear contours revealed systematic modifications in the folding of the cells and nuclei in the course of the murine second cell cycle. The progression of cells through the second cell cycle was correlated with an increasing diversification of cellular and nuclear shape, with the diversification being much more pronounced in the nuclear shapes.

Action of phorbol myristate acetate (PMA) at fertilization of mouse oocytes in vitro

Phorbol ester (PMA) in concentration 5 and 10 ng ml-1 blocks cytokinesis of the second maturation division in mouse oocytes. Karyokinesis is not impaired and digynic triploid oocytes are obtained which undergo first cleavage division. Effectiveness of blocking cytokinesis is dependent on the timing of exposure of oocytes to PMA action. When oocytes are subjected to PMA at the onset of the second maturation division only 14.5% of eggs are triploid. PMA present during fertilization in vitro (about 1 h exposure to PMA) induces triploidy in 40% eggs. Extending the time of exposure of oocytes to 2 h produces 76% tripronucleate eggs. Applicability of PMA is compared with the use of cytochalasin B to induce triploidy in the mouse.

Cortical and zona reactions of heat-activated mouse eggs

Oocytes collected from superovulated Swiss albino mice were activated by heat-shock and/or fertilized in vitro. Electron microscopy showed that the cortical reaction in heat-treated eggs was incomplete. Digestion of the zona pellucida of untreated, heat-treated and fertilized eggs by pronase showed that zona pellucida hardening did occur but was weaker in heat-treated than in fertilized eggs. Fertilizability of heat-treated eggs decreased 1.5 h after heating. We concluded that, in heat-activated eggs, changes occur at the zona and plasmalemma but they are not identical with those in fertilized eggs.

Cytochalasin B-induced triploidy in mouse oocytes fertilized in vitro

Mouse eggs and spermatozoa were treated in various ways with 5 or 10 mug cytochalasin B/ml. The fertilization rate in vitro was reduced by treatment with the drug but 80-90% of the eggs fertilized were triploid. Many of the experimental eggs were penetrated by one or more spermatozoa but remained unfertilized (75% compared with 9% in control eggs). It is suggested that cytochalasin B weakens the zona reaction and interferes with fusion of gametes but does not prevent the block to polyspermy.