Background:The significance of Pak1 in prostate cancer remains unclear. Results: Pak1 knockdown impaired prostate tumor growth via increased expression of TGF␤ and reduced secretion of MMP9. Conclusions:We demonstrated that Pak1 is a more potent mediator of prostate cancer cell migration and tumor growth than Pak6, the predominant isoform in the prostate. Significance: A novel role of Pak1 in prostate cancer is identified.

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Background: Ki-67 proliferation index was recently incorporated in the grading of neuroendocrine neoplasms (NENs) of the gastrointestinal tract (GIT) and pancreas. These are now divided into well-differentiated neuroendocrine tumors (WDNETs, grades 1 and 2) and poorly differentiated neuroendocrine carcinomas (grade 3). While Ki-67 is an established proliferation marker in NENs, phosphohistone H3 (PHH3), a newer marker of mitotic activity, is not. Methods: We determined Ki-67 and PHH3 indices on cytologic samples from WDNETs of the GIT and pancreas using an automated cellular imaging system (ACIS®). Results: There was a strong correlation between Ki-67 and PHH3 indices generated by ACIS on cytologic samples. However, in some cases the two stains caused conflicting grades within the same tumor. Conclusion: Both antibodies stain cells in different phases of the cell cycle which may cause discordant grades, thus affecting patient management and prognostication. Ki-67 staining is stronger than PHH3, making ‘hot spots' easier to identify on ACIS. Ki-67 is more ideal than PHH3 for staining NENs, especially in tumors with borderline grades. Because PHH3 generates lower mitotic indices it should not be used as a proliferation marker in NENs until its expression has been further characterized.