Rabbit Anti-Human RACGAP1 (Phospho Ser387) Polyclonal antibody

Purpose: To assess the significance of Rac GTPase-activating protein 1 (RACGAP1) expression in identifying HBV-positive human hepatocellular carcinoma (HCC) patients who are at high risk for recurrent disease. Experimental Design: The prognostic significance of RACGAP1 was compared with clinicopathologic parameters available at diagnosis using multivariate and log-rank test. RACGAP1 expression and outcome in recurrence was compared between 35 patients with recurrence and 41 patients without recurrence using Kaplan-Meier analysis. RACGAP1-targeted molecules and pathways were identified and characterized by inhibition with siRNA duplexes. Results: Kaplan-Meier analysis showed that the level of RACGAP1 expression is sufficient to predict the early recurrence of HCC: high RACGAP1 expression correlates with high risk of postresection recurrent HCC (P < 0.0005). Silencing of RACGAP1 in Hep3B and MHCC97-H HCC cells with high endogenous RACGAP1 expression inhibited cell migration and invasion. Using Ingenuity Pathway Analysis, the target molecules silenced in the RACGAP1 interactome were mostly genes related to the mitotic roles of the polo-like kinases. These included PRC1, AURKB, CDC2, ECT2, KIF23, PAK1, and PPP2R5E. In providing clinical corroboration of these results, when expression of these transcripts was analyzed in an expression database that we have established previously for HBV-positive HCC patients, these genes was mostly upregulated in patients who exhibited early recurrent disease and hence provided important corroboration of these results. Conclusions: siRNA-silencing RACGAP1 mainly targeted genes in an interactome clinically relevant to early HCC recurrence. Besides being an independent informative prognostic biomarker, RACGAP1 could also be a potential molecular target for designing therapeutic strategies for HCC. Clin Cancer Res; 17(18); 6040-51. (C) 2011 AACR.

As they enter mitosis, animal cells undergo profound actin-dependent changes in shape to become round. Here we identify the Cdk1 substrate, Ect2, as a central regulator of mitotic rounding, thus uncovering a link between the cell-cycle machinery that drives mitotic entry and its accompanying actin remodeling. Ect2 is a RhoGEF that plays a well-established role in formation of the actomyosin contractile ring at mitotic exit, through the local activation of RhoA. We find that Ect2 first becomes active in prophase, when it is exported from the nucleus into the cytoplasm, activating RhoA to induce the formation of a mechanically stiff and rounded metaphase cortex. Then, at anaphase, binding to RacGAP1 at the spindle midzone repositions Ect2 to induce local actomyosin ring formation. Ect2 localization therefore defines the stage-specific changes in actin cortex organization critical for accurate cell division.