Richard C. Duke

Whole recombinant yeast vaccine activates dendritic cells and elicits protective cell-mediated immunity

There is currently a need for vaccines that stimulate cell-mediated immunity—particularly that mediated by CD8+ cytotoxic T lymphocytes (CTLs)—against viral and tumor antigens. The optimal induction of cell-mediated immunity requires the presentation of antigens by specialized cells of the immune system called dendritic cells (DCs). DCs are unique in their ability to process exogenous antigens via the major histocompatibility complex (MHC) class I pathway as well as in their ability to activate naive, antigen-specific CD8+ and CD4+ T cells. Vaccine strategies that target or activate DCs in order to elicit potent CTL-mediated immunity are the subject of intense research. We report here that whole recombinant Saccharomyces cerevisiae yeast expressing tumor or HIV-1 antigens potently induced antigen-specific, CTL responses, including those mediating tumor protection, in vaccinated animals. Interactions between yeast and DCs led to DC maturation, IL-12 production and the efficient priming of MHC class I- and class II-restricted, antigen-specific T-cell responses. Yeast exerted a strong adjuvant effect, augmenting DC presentation of exogenous whole-protein antigen to MHC class I- and class II-restricted T cells. Recombinant yeast represent a novel vaccine strategy for the induction of broad-based cellular immune responses.

Human DU145 prostate cancer cells overexpressing mitogen-activated protein kinase phosphatase-1 are resistant to Fas ligand-induced mitochondrial perturbations and cellular apoptosis †

Recent studies have suggested that MAP kinase phosphatase 1 (MKP-1) is overexpressed in prostate cancer. To evaluate the role of MKP-1 in regulating cell death and tumor growth in prostate cancer, MKP-1 was conditionally overexpressed in the human prostate cancer cell line DU145. Overexpression of MKP-1 in DU145 cells blocked activation of stress-activated protein kinase (SAPK/JNK). MKP-1 overexpression in DU-145 cells was also found to inhibit Fas ligand (FasL)-induced apoptosis, as well as block the activation of caspases by Fas engagement. In addition, MKP-1 blocked the activation of apoptosis by transfected MEKK-1 and ASK-1, presumably through its inhibition of the SAPK/JNK family of enzymes. MKP-1 blocked the ability of FasL to induce loss of mitochondrial transmembrane potential (Δγm), suggesting that MKP-1 acts upstream of mitochondrial pro-apoptotic events induced by FasL and that the SAPK/JNK pathway may form the signaling link between Fas receptor and mitochondrial dysfunction. Thus, MKP-1 overexpression in prostate cancer may play a role in promoting prostate carcinogenesis by inhibiting FasL-induced cell death.

Three‐dimensional spheroid cultures of human prostate cancer cell lines

Many of the available human prostate cancer (PC) cell lines have lost androgen sensitivity and no longer secrete prostate‐specific proteins after serial culturing in cell monolayers. Three‐dimensional spheroid cultures have been found to better mimic the in vivo phenotypes of several nonprostatic cell lines.

CD95 (Fas) Ligand

CD95 (Fas/APO-1) is a 45 kD cell surface glycoprotein and member of the tumor necrosis factor receptor superfamily (Nagata and Golstein 1995; Itoh et al. 1991; Oehm et al. 1992; Watanabe-Fukunaga et al. 1992a; Smith et al. 1994). Although CD95 is expressed in many tissues including liver, heart, gut, skin and ovaries (Watanabe-Fukunaga et al. 1992b; Leithauser et al. 1993), its major biological role appears to be in the regulation of immune responses (Nagata and Golstein 1995; Cohen and Eisenberg 1992; Vignaux and Golstein, 1994). Lpr mice which lack the ability to express functional CD95 accumulate large numbers of abnormal T and B cells in their peripheral lymphoid organs and develop autoimmune disease (Cohen and Eisenberg 1992; Cohen and Eisenberg 1991; Roths et al. 1984). The abnormal lymphocytes in these mice express markers found on activated lymphocytes and it appears that autoimmunity develops as a result of an inability to eliminate autoreactive T and B cells.