Expression of mTOR signaling pathway markers in prostate cancer progression.

BACKGROUND: The PI3K/AKT/mTOR pathway is central to prostate cancer progression. A preliminary investigation of immuno-histochemical expression of mammalian target of rapamycin (mTOR) pathway markers was undertaken to identify patterns of expression in prostate tissue. METHODS: Immunohistochemistry was performed on a custom-made prostate tissue array. Mean long scores and variability of long scores for each marker were recorded for normal lumenal cells, prostate intraepithelial neoplasia (PIN), and cancer. RESULTS: Expression of PTEN decreased and mTOR signaling pathway markers increased in PIN and in cancer as compared to normal cells in the majority of samples. Overexpression of 4E-BP1 and p-4E-BP1 was observed in PIN and cancer. However, in cancer, the overexpression of 4E-BP1 was significantly higher than with any other marker. DISCUSSION: Results suggest that 4E-BP1 overexpression is strongly associated with prostate cancer, especially when combined with PTEN and mTOR expression data. Hierarchical clustering analysis utilizing PTEN, mTOR, and 4E-BP1 separated normal from cancer cell populations in most cases.

Integrin-dependent amplification of the G2 arrest induced by ionizing radiation.

The progressive loss of laminin 5 and the alpha6beta4 integrin is a characteristic of the transition of prostatic intraepithelial neoplasia (PIN) to invasive human prostate cancer. Our objective was to determine if the loss of the interaction with laminin 5 would influence the ability of human epithelial cells to respond to DNA damage. Three cellular damage responses to ionizing radiation (IR) were analyzed including G2 progression, cdc2 phosphorylation, and cell survival. The adhesion of normal human prostate epithelial cells to laminin 5 amplified the G2 arrest induced by IR, and depends on a known cell binding domain of laminin 5. The alteration of G2 arrest was confirmed by an inhibition of phospho-cdc2 nuclear translocation. In contrast, a prostate epithelial cancer cell line blocked in G2 independent of adhesion to laminin 5. The survival of these cell lines in response to IR was unaffected by adhesion to laminin 5. These results suggest that cell adhesion to laminin 5 in normal cells will amplify the IR induced G2 cell cycle progression block without altering cell survival. The loss of laminin 5 and the alpha6beta4 integrin in PIN lesions may contribute to the selection and progression of genetically unstable cell types via attenuation of a DNA damage induced G2 arrest.

Distribution of cell wall components in Sphagnum hyaline cells and in liverwort and hornwort elaters.

Spiral secondary walls are found in hyaline cells of Sphagnum, in the elaters of most liverworts, and in elaters of the hornwort Megaceros. Recent studies on these cells suggest that cytoskeletal and ultrastructural processes involved in cell differentiation and secondary wall formation are similar in bryophytes and vascular plant tracheary elements. To examine differences in wall structure, primary and secondary wall constituents of the hyaline cells of Sphagnum novo-zelandicum and elaters of the liverwort Radula buccinifera and the hornwort Megaceros gracilis were analyzed by immunohistochemical and chemical methods. Anti-arabinogalactan-protein antibodies, JIM8 and JIM13, labeled the central fibrillar secondary wall layer of Megaceros elaters and the walls of Sphagnum leaf cells, but did not label the walls of Radula elaters. The CCRC-M7 antibody, which detects an arabinosylated (1-->6)-linked beta-galactan epitope, exclusively labeled hyaline cells in Sphagnum leaves and the secondary walls of Radula elaters. Anti-pectin antibodies, LM5 and JIM5, labeled the primary wall in Megaceros elaters. LM5 also labeled the central layer of the secondary wall but only during formation. In Radula elaters, JIM5 and another anti-pectin antibody, JIM7, labeled the primary wall. The distribution of arabinogalactan-proteins and pectic polysaccharides restricted to specific wall types and stages of development provides evidence for the developmental and functional regulation of cell wall composition in bryophytes. Monosaccharide-linkage analysis of Sphagnum leaf cell walls suggests they contain polysaccharides similar to those of higher plants. The most abundant linkage was 4-Glc, typical of cellulose, but there was also evidence for xyloglucans, 4-linked mannans, 4-linked xylans and rhamnogalacturonan-type polysaccharides.