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Tastin was previously characterized as an accessory protein for cell adhesion that participates in early embryo implantation. Here, we report that tastin is also required for spindle assembly during mitosis. Tastin protein levels peaked in the G2/M phase and abruptly declined after cell division. Microscopy showed that tastin is primarily localized on the microtubules, centrosomes, and the mitotic spindle during the cell cycle. Tastin interacted with the dynein intermediate chain, p150Glued, and γ-tubulin in addition to Tctex-1 (the light chain of dynein). Overexpression of tastin led to monopolar spindle formation, whereas loss of tastin expression caused profound mitotic block and preferentially induced multipolar spindles. These multipolar spindles were generated through a loss of cohesion in mitotic centrosomes; specifically, tastin depletion caused the fragmentation of pericentrosomal material and the splitting of the centrioles at the spindle poles. Tastin depletion induced centrosome abnormalities exclusively during mitosis and required both microtubule integrity and Eg5 activity. However, tastin depletion did not disrupt the organization of spindle poles, as revealed by localization of nuclear mitotic apparatus protein (NuMA) and the p150Glued component of dynactin. These data indicate that the major function of tastin during mitosis is to maintain the structural and dynamic features of centrosomes, thereby contributing to spindle bipolarity. [ABSTRACT FROM AUTHOR]

Elevated expression of sialyl Lewis X has been postulated to be a prognostic indicator of prostate cancer. However, direct evidence for the relationship between increased expression of sialyl Lewis X and malignancy of prostate cancer is still lacking. To determine whether increased levels of sialyl Lewis X leads to malignancy in prostate tumor, we transfected the human prostate cancer cell line PC-3 with α1,3-fucosyltransferase III (FTIII) to obtain stable transfectants, PC-3-FTIII lines, that highly express sialyl Lewis X. When inoculated in the prostate of nude mice, PC-3-FTIII cells produced large prostate tumors, while mock-transfected PC-3 cells, which are negative for sialyl Lewis X antigen, produced small prostate tumors. The aggressive tumor formation by PC-3-FTIII cells was inhibited by preincubation of the tumor cells with anti-sialyl Lewis X antibody, by the presence of sialyl Lewis X oligosaccharide or by selectin ligand mimic peptide but not by control peptide. PC-3-FTIII cells and mock-transfected PC-3 cells exhibited no significant difference in cell numbers when cultured in vitro. Remarkably, PC-3-FTIII adhered to prostatic stromal cells in vitro with higher affinity than mock-transfected PC-3. Such adhesion was inhibited by preincubation of PC-3-FTIII cells with antisialyl Lewis X antibody, by the addition of sialyl Lewis X oligosaccharide or by selectin ligand mimic peptide. However, anti-E-selectin, anti-P-selectin or anti-L-selectin antibodies did not inhibit the adhesion of PC-3-FTIII cells to the stromal cells. These results suggest that prostate cancer cells gain aggressiveness through adhesive interaction with prostatic stromal cells by a novel mechanism involving sialyl Lewis X. © 2003 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]