A prostatic intraepithelial neoplasia-dependent p27 Kip1 checkpoint induces senescence and inhibits cell proliferation and cancer progression.

Transgenic expression of activated AKT1 in the murine prostate induces prostatic intraepithelial neoplasia (PIN) that does not progress to invasive prostate cancer (CaP). In luminal epithelial cells of Akt-driven PIN, we show the concomitant induction of p27(Kip1) and senescence. Genetic ablation of p27(Kip1) led to downregulation of senescence markers and progression to cancer. In humans, p27(Kip1) and senescence markers were elevated in PIN not associated with CaP but were decreased or absent, respectively, in cancer-associated PIN and in CaP. Importantly, p27(Kip1) upregulation in mouse and human in situ lesions did not depend upon mTOR or Akt activation but was instead specifically associated with alterations in cell polarity, architecture, and adhesion molecules. These data suggest that a p27(Kip1)-driven checkpoint limits progression of PIN to CaP.

mTOR inhibition reverses Akt-dependent prostate intraepithelial neoplasia through regulation of apoptotic and HIF-1-dependent pathways.

Loss of PTEN function leads to activation of phosphoinositide 3-kinase (PI3K) signaling and Akt. Clinical trials are now testing whether mammalian target of rapamycin (mTOR) inhibition is useful in treating PTEN-null cancers. Here, we report that mTOR inhibition induced apoptosis of epithelial cells and the complete reversal of a neoplastic phenotype in the prostate of mice expressing human AKT1 in the ventral prostate. Induction of cell death required the mitochondrial pathway, as prostate-specific coexpression of BCL2 blocked apoptosis. Thus, there is an mTOR-dependent survival signal required downstream of Akt. Bcl2 expression, however, only partially restored intraluminal cell growth in the setting of mTOR inhibition. Expression profiling showed that Hif-1 alpha targets, including genes encoding most glycolytic enzymes, constituted the dominant transcriptional response to AKT activation and mTOR inhibition. These data suggest that the expansion of AKT-driven prostate epithelial cells requires mTOR-dependent survival signaling and activation of HIF-1 alpha, and that clinical resistance to mTOR inhibitors may emerge through BCL2 expression and/or upregulation of HIF-1 alpha activity.

Prostate intraepithelial neoplasia induced by prostate restricted Akt activation: the MPAKT model.

To determine whether Akt activation was sufficient for the transformation of normal prostate epithelial cells, murine prostate restricted Akt kinase activity was generated in transgenic mice (MPAKT mice). Akt expression led to p70S6K activation, prostatic intraepithelial neoplasia (PIN), and bladder obstruction. mRNA expression profiles from MPAKT ventral prostate revealed similarities to human cancer and an angiogenic signature that included three angiogenin family members, one of which was found elevated in the plasma of men with prostate cancer. Thus, the MPAKT model may be useful in studying the role of Akt in prostate epithelial cell transformation and in the discovery of molecular markers relevant to human disease.

Antiplasmodial activity of extracts and quassinoids isolated from seedlings of Ailanthus altissima (Simaroubaceae).

Extracts and isolated compounds from seedlings of Ailanthus altissima, were assessed for antiplasmodial activity in vitro. Two quassinoids, ailanthone and 6alpha-tigloyloxychaparrinone, isolated from the active extracts showed activity against both chloroquine-resistant and chloroquine-sensitive strains of Plasmodium falciparum in vitro. Only ailanthone demonstrated low toxicity against the Vero cell line (kidney cells from the African green monkey). This is the first report of the isolation and antiplasmodial activity of 6alpha-tigloyloxychaparrinone from this species.

Regulation of macrophage migration inhibitory factor expression by glucocorticoids in vivo.

Glucocorticoid hormones are important anti-inflammatory agents because of their anti-inflammatory and proapoptotic action within the immune system. Their clinical usefulness remains limited however by side effects that result in part from their growth inhibitory action on sensitive target tissues. The protein mediator, macrophage migration inhibitory factor (MIF), is an important regulator of the host immune response and exhibits both glucocorticoid-antagonistic and growth-regulatory properties. MIF has been shown to contribute significantly to the development of immunopathology in several models of inflammatory disease. Although there is emerging evidence for a functional interaction between MIF and glucocorticoids in vitro, little is known about their reciprocal influence in vivo. We investigated the expression of MIF in rat tissues after ablation of the hypothalamic-pituitary-adrenal axis and after high-dose glucocorticoid administration. MIF expression is constitutive and independent of the influence of adrenal hormones. Hypophysectomy and the attendent loss of pituitary hormones, by contrast, decreased MIF protein content in the adrenal gland. Administration of dexamethasone was found to increase MIF protein expression in those organs that are considered to be sensitive to the growth inhibitory effects of glucocorticoids (immune and endocrine tissues, skin, and muscle). This increase was most likely because of a posttranscriptional regulatory effect because tissue MIF mRNA levels were not influenced by dexamethasone treatment. Finally, MIF immunoneutralization enhanced lymphocyte egress from blood during stress-induced lymphocyte redistribution, consistent with a functional interaction between MIF and glucocorticoids on immune cell trafficking in vivo. These findings suggest a role for MIF in both the homeostatic and physiological action of glucocorticoids in vivo.