No abstract

Aim: To study the expression of proline-rich Akt-substrate PRAS40 in the cell survival pathway and tumor progression. Methods: The effects of three key kinase inhibitors on PRAS40 activity in the cell survival pathway, serum withdrawal, H 2 O 2 and overexpression of Akt were tested. The expression of PRAS40, Akt, Raf and 14-3-3 in normal cells and cancer cell lines was determined by Western blot. Results: The PI3K inhibitors worthmannin and Ly294002, but not rapamycin, completely inhibited the phosphorylation of Akt and PRAS40. The phosphorylation level of Akt decreased after serum withdrawal and treatment with the MEK inhibitor Uo126, but increased after treatment with H 2 O 2 at low concentration, whereas none of these treatments changed PRAS40 activity. 14-3-3 is a PRAS40 binding protein, and the expression of 14-3-3, like that of PRAS40, was higher in HeLa cells than in HEK293 cells; PRAS40 had a stronger phosphorylation activity in A549 and HeLa cancer cells than in HEK293 normal cells. In the breast cancer model (MCF10A/MCF7) and lung cancer model (BEAS/H1198/H1170) we also found the same result: PRAS40 was constitutively active in H1198/H1170 and MCF7 premalignant and malignant cancer cells, but weakly expressed in MCF10A and BEAS normal cell. We also discussed PRAS40 activity in other NSCLC cell lines. Conclusion: The PI3K-Akt survival pathway is the main pathway that PRAS40 is involved in; PRAS40 is a substrate for Akt, but can also be activated by an Aktindependent mechanisms. PRAS40 activation is an early event during breast and lung carcinogenesis.

Recent progress in cancer biology indicates that eradication of cancer stem cells (CSCs) is essential for more effective cancer therapy. Unfortunately, cancer stem cells such as glioma stem-like cells (GSLCs) are often resistant to either radio- or chemotherapy. Therefore, screening and development for novel therapeutic modalities against CSCs has been an important emerging field in cancer research. In this study, we report that a synthetic dl-nordihydroguaiaretic acid compound (dl-NDGA or "Nordy"), inhibited self-renewal and induced differentiation of GSLCs in vitro and in vivo. We found that Nordy inhibited an enzyme known to be involved in leukemia stem cell and leukemia progression, Alox-5, and attenuated the growth of GSLCs in vitro. Nordy reduced the GSLC pool through a decrease in the CD133(+) population and abrogated clonogenicity. Nordy appeared to exert its effect via astrocytic differentiation by up-regulation of GFAP and down-regulation of stemness related genes, rather than by inducing apoptosis of GSLCs. The growth inhibition of xenografted glioma by Nordy was more long-lasting compared with that of the akylating agent BCNU, which exhibited significant relapse on drug discontinuation resulting from an enrichment of GSLCs. Meanwhile, transient exposure to Nordy reduced tumorigenecity of GSLCs and induced differentiation of the xenografts. Taken together, we have identified Alox-5 as a novel target in GSLCs and its inhibition with Nordy exhibits therapeutic implications through inducing GSLC differentiation.

Peptide loading of MHC class II (MHCII) molecules is catalyzed by the non-classical MHCII-related molecule, H2-M. H2-O, another MHCII-like molecule, associates with H2-M and modulates H2-M function. The MHCII presentation pathway is tightly regulated in dendritic cells (DCs); yet how the key modulators of MHCII presentation, H2-M and H2-O, are affected in different DC subsets in response to maturation is unknown. Here we show that H2-O is markedly downregulated in vivo in mouse CD8α− DCs in response to a broad array of TLR agonists. In contrast, CD8α+ DCs only modestly downregulated H2-O in response to TLR-agonists. H2-M levels were slightly down-modulated in both CD8α− and CD8α+ DCs. As a consequence, H2-M:H2-O ratios significantly increased for CD8α− but not CD8α+ DCs. The TLR-mediated downregulation was DC-specific, as B cells did not show significant H2-O and H2-M downregulation. TLR4 signaling was required to mediate DC H2-O downregulation in response to LPS. Finally, our studies showed that the mechanism of H2-O downregulation was likely due to direct protein degradation of H2-O as well as down regulation of H2-O mRNA levels. The differential H2-O and H2-M modulation after DC maturation support the proposed roles of CD8α− dendritic cells in initiating CD4-restricted immune responses by optimal MHCII presentation and CD8α+ DCs in promoting immune tolerance via presentation of low levels of MHCII-peptide.

Although multiple studies examine institutional transitions from one learning management system (LMS) to another, or compare system merits, studies examining student's free choice of access on parallel LMSs for the same course are absent from the literature. In order to investigate usage in a free-choice situation, identical content was posted at the same time to two different LMSs in a large enrollment class with a diversity of majors. Two prevalent LMSs were utilized in the study; WebCT, which was in existence at a university-wide level previously, and Moodle, which will become the new university-wide system in the 2012-13 academic year onwards. Although this inquiry revealed that most students chose to use the WebCT system (85% WebCT users, 15% Moodle users; both self-reported and log-verified), the reasons given for WebCT preference pertained largely to habit and that most other courses are using the WebCT LMS. In contrast, the reasons given for using Moodle spoke directly to the attributes of the LMS itself, namely the interface quality and the way it is organized. This study indicates that institutions should look beyond student usage patterns in making LMS choices, and that LMS quality is sometimes, and perhaps unfortunately, overshadowed by student habit and familiarity.