Curcumin (diferuloyl-methane) enhances tumor necrosis factor-related apoptosis-inducing ligand-induced apoptosis in LNCaP prostate cancer cells.

The role of natural food products in prevention of prostate cancer has been confirmed in recent epidemiological studies; however, the mechanism of chemoprevention by the dietary constituents largely remains unknown. Curcumin, the yellow pigment and active component of turmeric (Curcuma longa), exhibits chemopreventive and growth inhibitory activity against several tumor cell lines. The androgen-sensitive human prostate cancer cell line LNCaP is only slightly susceptible to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), a member of the tumor necrosis factor family of cell death-inducing ligands. In this study, we investigated whether curcumin and TRAIL cooperatively interact to promote death of LNCaP cells. At low concentrations (10 micro M curcumin and 20 ng/ml TRAIL), neither of the two agents alone produced significant cytotoxicity (curcumin, <10%; TRAIL, approximately 15%) in LNCaP cells, as measured by the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxy-phenyl)-2-(4-sulfonyl)-2H-tetrazolium dye reduction assay. On the other hand, cell death was markedly enhanced (2-3-fold) if tumor cells were treated with curcumin and TRAIL together. The combined curcumin and TRAIL treatment increased the number of hypodiploid cells and induced DNA fragmentation in LNCaP cells. The combined treatment induced cleavage of procaspase-3, procaspase-8, and procaspase-9, truncation of Bid, and release of cytochrome c from the mitochondria, indicating that both the extrinsic (receptor-mediated) and intrinsic (chemical-induced) pathways of apoptosis are triggered in prostate cancer cells treated with a combination of curcumin and TRAIL. These results define a potential use of curcumin to sensitize prostate cancer cells for TRAIL-mediated immunotherapy.

In vitro analysis of the antileukemic effect of tumor necrosis factor-alpha gene therapy with myeloid progenitor cells: the role of dendritic cells.

We have previously demonstrated that tumor necrosis factor-alpha (TNF-alpha) gene therapy with transgene-expressing myeloid progenitor cells (32DTNF-alpha) is effective in inhibiting the progression of leukemia with a lethal dose of murine 32Dp210 myeloid leukemia cells. Because TNF-alpha has been shown to induce the activation and maturation of dendritic cells (DCs), we investigated the effect of TNF-alpha secreted by transduced cells (32DTNF-alpha cells) on the activation of DCs and their role in the production of antileukemic cytotoxic T lymphocytes (CTLs). We demonstrate that administration of 32DTNF-alpha cells to the mice enhances the allo-stimulatory capacity of the splenic (CD11c+) and bone marrow-derived DCs in both mixed leukocyte response and CTL development. The enhanced allo-stimulatory capacity of splenic DCs from mice injected with 32DTNF-alpha cells correlated with increase in the cell-surface expression of the costimulatory molecules CD40, CD80, CD86, and major histocompatibility complex (MHC) class II molecules (I-Ak), and production of interleukin-12 (IL-12). Furthermore, administration of 32DTNF-alpha cells during immunization with irradiated 32Dp210 leukemia cells augmented the capacity of splenic DCs to stimulate antileukemic CTL response in spleen cells. Collectively, these data suggest that in vivo production of TNF-alpha by transduced cells enhances the phenotypic and functional activation of DCs, resulting in induction of a stronger antileukemic cytotoxic T-cell immune response.

Disparate in vitro and in vivo antileukemic effects of resveratrol, a natural polyphenolic compound found in grapes.

Resveratrol (trans-3,4',5-trihydroxystilbene), a polyphenol found in grapes and grape wine, has been reported to exhibit cardioprotective and chemopreventive activity against chemical carcinogenesis. It has also been shown to have growth inhibitory activity toward solid tumors in vivo. However, the antitumor activity of resveratrol against hematologic tumors in vivo has not been examined. In this study, the antileukemic activity of resveratrol in vitro and in vivo was examined using a mouse myeloid leukemia cell line (32Dp210). Treatment of 32Dp210 leukemia cells with resveratrol at micromolar concentrations (25-50 micromol/L) significantly and irreversibly inhibited their clonal growth in vitro. The clonal growth inhibition by resveratrol was associated with extensive cell death and an increase in hypodiploid (sub-G1) cells. Resveratol caused internucleosomal DNA fragmentation, suggesting apoptosis as the mode of cell death in 32Dp210 cells. DNA fragmentation was associated with activation of caspase-3, because cleavage of procaspase-3 was detected in resveratrol-treated cells. Although 32Dp210 cells treated with resveratrol in vitro did not produce leukemia in vivo, only a weak antileukemic effect of resveratrol was observed when administered orally. At doses of 8 mg or 40 mg/kg body daily, five times/wk, resveratrol did not affect the survival of mice injected with leukemia cells. Weak potential antileukemic activity of resveratrol was suggested only at a dose of 80 mg/kg body (2 survivors of 14 mice treated). Thus, despite strong antiproliferative and proapoptotic activities of resveratrol against 32Dp210 cells in vitro, a potential antileukemia effect in vivo, if present, occurs only in a small fraction of mice.