Masahiro Kizaki

Capsaicin, a component of red peppers, inhibits the growth of androgen-independent, p53 mutant prostate cancer cells.

Capsaicin is the major pungent ingredient in red peppers. Here, we report that it has a profound antiproliferative effect on prostate cancer cells, inducing the apoptosis of both androgen receptor (AR)-positive (LNCaP) and -negative (PC-3, DU-145) prostate cancer cell lines associated with an increase of p53, p21, and Bax. Capsaicin down-regulated the expression of not only prostate-specific antigen (PSA) but also AR. Promoter assays showed that capsaicin inhibited the ability of dihydrotestosterone to activate the PSA promoter/enhancer even in the presence of exogenous AR in LNCaP cells, suggesting that capsaicin inhibited the transcription of PSA not only via down-regulation of expression of AR, but also by a direct inhibitory effect on PSA transcription. Capsaicin inhibited NF-kappa activation by preventing its nuclear migration. In further studies, capsaicin inhibited tumor necrosis factor-alpha-stimulated degradation of IkappaBalpha in PC-3 cells, which was associated with the inhibition of proteasome activity. Taken together, capsaicin inhibits proteasome activity which suppressed the degradation of IkappaBalpha, preventing the activation of NF-kappaB. Capsaicin, when given orally, significantly slowed the growth of PC-3 prostate cancer xenografts as measured by size [75 +/- 35 versus 336 +/- 123 mm(3) (+/-SD); P = 0.017] and weight [203 +/- 41 versus 373 +/- 52 mg (+/-SD); P = 0.0006; capsaicin-treated versus vehicle-treated mice, respectively]. In summary, our data suggests that capsaicin, or a related analogue, may have a role in the management of prostate cancer.

Green Tea Component, Catechin, Induces Apoptosis of Human Malignant B Cells via Production of Reactive Oxygen Species

Purpose: Green tea polyphenol, (−)-epigallocatechin-3-gallate, has been shown to inhibit cellular proliferation and induce apoptosis of various cancer cells. The aim of this study was to investigate the possibility of (−)-epigallocatechin-3-gallate as a novel therapeutic agent for the patients with B-cell malignancies including multiple myeloma. Experimental Design: We investigated the effects of (−)-epigallocatechin-3-gallate on the induction of apoptosis in HS-sultan as well as myeloma cells in vitro and further examined the molecular mechanisms of (−)-epigallocatechin-3-gallate-induced apoptosis. Results: (−)-Epigallocatechin-3-gallate rapidly induced apoptotic cell death in various malignant B-cell lines in a dose- and time-dependent manner. (−)-Epigallocatechin-3-gallate-induced apoptosis was in association with the loss of mitochondrial transmembrane potentials (Δψm); the release of cytochrome c, Smac/DIABLO, and AIF from mitochondria into the cytosol; and the activation of caspase-3 and caspase-9. Elevation of intracellular reactive oxygen species (ROS) production was also shown during (−)-epigallocatechin-3-gallate-induced apoptosis of HS-sultan and RPMI8226 cells as well as fresh myeloma cells. Antioxidant, catalase, and Mn superoxide dismutase significantly reduced ROS production and (−)-epigallocatechin-3-gallate-induced apoptosis, suggesting that ROS plays a key role in (−)-epigallocatechin-3-gallate-induced apoptosis in B cells. Furthermore, a combination with arsenic trioxide (As2O3) and (−)-epigallocatechin-3-gallate significantly enhanced induction of apoptosis compared with As2O3 alone via decreased intracellular reduced glutathione levels and increased production of ROS. Conclusions: (−)-Epigallocatechin-3-gallate has potential as a novel therapeutic agent for patients with B-cell malignancies including multiple myeloma via induction of apoptosis mediated by modification of the redox system. In addition, (−)-epigallocatechin-3-gallate enhanced As2O3-induced apoptosis in human multiple myeloma cells.

Induction of cell death in human papillomavirus 18-positive cervical cancer cells by E6 siRNA

Human cervical cancer is caused by high-risk types of human papillomavirus (HPV) such as HPV16 and HPV18, which possess the E6 and E7 oncogenes, whose concurrent expression is a prerequisite for cancer development and maintaining malignant phenotypes. Silencing these oncogenes is considered to be applicable in molecular therapies of human cervical cancer. However, it remains to be determined whether E6, E7, or both should be silenced to obtain most efficient antitumor activity by an HPV small-interfering RNA (siRNA). Herein, we report two types of siRNAs targeting HPV18 E6, that exerted a negative growth effect on HPV18-positive cervical cancer cells (HeLa and SW756), in part, inducing cell death. One siRNA (Ex-18E6), designed to target both E6-E7 mRNA and its splicing variant, E6*I-E7 mRNA, efficiently knocked down both E6 and E7 expression. The other (Sp-18E6), designed to specifically target E6-E7 mRNA but not E6*I-E7 mRNA, suppressed E6 to a similar level as Ex-18E6; however, it less efficiently inhibited E7 as compared to Ex-18E6. Although both siRNAs induced cell death, Sp-18E6 siRNA induced more prominent cell death than Ex-18E6. Our results suggest that E6-specific suppression may induce more potent anticancer activity than simultaneous E6 and E7 suppression, and that E6-specific targeting is a promising strategy for siRNA-based therapy for HPV-positive cervical cancer.

A New Mechanism of Methotrexate Action Revealed by Target Screening with Affinity Beads

Methotrexate (MTX) is the anticancer and antirheumatoid drug that is believed to block nucleotide synthesis and cell cycle by inhibiting dihydrofolate reductase activity. We have developed novel affinity matrices, termed SG beads, that are easy to manipulate and are compatible with surface functionalization. Using the matrices, here we present evidence that deoxycytidine kinase (dCK), an enzyme that acts in the salvage pathway of nucleotide biosynthesis, is another target of MTX. MTX modulates dCK activity differentially depending on substrate concentrations. 1-β-d-Arabinofuranosylcytosine (ara-C), a chemotherapy agent often used in combination with MTX, is a nucleoside analog whose incorporation into chromosome requires prior phosphorylation by dCK. We show that, remarkably, MTX enhances incorporation and cytotoxicity of ara-C through regulation of dCK activity in Burkitts lymphoma cells. Thus, this study provides new insight into the mechanisms underlying MTX actions and demonstrates the usefulness of the SG beads.

Induction of apoptosis via the modulation of reactive oxygen species (ROS) production in the treatment of myeloid leukemia.

Recent advances in genetic and molecular biology have provided greater insight into the biology of acute myeloid leukemia (AML). These investigations have shown that AML is a heterogeneous disease of biologically different entities. Current therapeutic approaches to AML are based on chemotherapy, but the side effects of the drugs used and various complications, including infections and bleeding, are sometimes fatal. In addition, responses to therapy and long-term outcome differ depending on the subentity in question. Therefore, it is essential to develop new therapeutic strategies such as biology adapted treatment based on the individual molecular pathogenesis of AML. Natural compounds appear to be safer than the current chemotherapeutic drugs, and we have therefore sought new potential agents among various natural compounds with the ability to induce the apoptosis of myeloid leukemic cells. Recently, we found that a highly toxic reactive oxygen species (ROS) generated via the hydrogen peroxide/myeloperoxidase [H(2)O(2)/MPO/halide] system by natural compounds induces apoptosis in MPO-positive leukemic cells. This result is of great interest in establishing novel therapeutic approaches to AML mediated through ROS-induced apoptosis of leukemic cells.

Establishment of a new human acute monocytic leukemia cell line TZ-1 with t(1;11)(p32;q23) and fusion gene MLL-EPS15

Human leukemia cell lines are of great value in investigating basic and applied aspects of cell biology and clinical medicine. There have been 37 leukemia cell lines carrying 11q23 translocation and MLL rearrangements; however, cell lines harboring with t(1;11)(p32;q23) have not been established. We report here for the first time a new acute monocytic leukemia (AMoL) cell line with t(1;11)(p32;q23), designated TZ-1, and herein describe its biological characteristics. Mononuclear cells isolated from the ascites from a patient with AMoL (French–American–British classification; acute myeloid leukemia M5a) were isolated and passaged by liquid culture medium for a year. TZ-1 cells revealed typical monocytic features in morphology and had a t(1;11)(p32;q23) translocation. The immunoprofiling as determined by flow cytometry showed that TZ-1 cells are positive for myeloid and monocytic markers with lymphoid-associated markers. Fluorescence in situ hybridization and reverse transcription-polymerase chain reaction analyses revealed MLL-EPS15 fusion transcript and protein. Taken together, these results suggest that TZ-1 is a new monocytic leukemia cell line with t(1;11) translocation and fusion gene MLL-EPS15. The established cell line, TZ-1, could provide a valuable model in the analysis of the pathogenesis of MLL-EPS15-positive leukemia and in the development of new agents for this type of leukemia.