Shinichi Kurakata

A novel humanized anti-human death receptor 5 antibody CS-1008 induces apoptosis in tumor cells without toxicity in hepatocytes

BACKGROUND The antitumor activity of CS-1008, a humanized agonistic anti-human death receptor (DR) 5 antibody, was investigated in preclinical models. MATERIALS AND METHODS Cytotoxicity of CS-1008 was evaluated in a several human tumor cell lines as well as primary human hepatocytes in vitro. To evaluate antitumor efficacy, athymic nude mice were inoculated with human colorectal tumor COLO 205, pancreatic tumor MIA PaCa-2 or non-small-cell lung carcinoma NCI-H2122 and CS-1008 was i.v. administered. The combination effects of CS-1008 with gemcitabine or docetaxel (Taxotere) against MIA PaCa-2 or NCI-H2122 were evaluated in vivo, respectively. RESULTS CS-1008 inhibited the growth of tumor cell lines with DR5 expression, including COLO 205, NCI-H2122, MIA PaCa-2 and renal cell adenocarcinoma ACHN in vitro with antibody cross-linkage. Using COLO 205, apoptosis induction was confirmed by annexin V staining. Weekly administration of CS-1008 resulted in the inhibition of COLO 205 tumor growth as well as MIA PaCa-2 in vivo. CS-1008 in combination with gemcitabine or docetaxel demonstrated enhanced antitumor activity against MIA PaCa-2 or NCI-H2122 cells, respectively. Unlike tumor necrosis factor-related apoptosis-inducing ligand, CS-1008 did not induce cell death in human primary hepatocytes. CONCLUSION CS-1008 has a selective toxicity toward tumor cells expressing DR5 and the potential for antitumor efficacy in human malignancies.

Antitumor activity and novel DNA-self-strand-breaking mechanism of CNDAC (1-(2-C-cyano-2-deoxy-?-d-ARABINO-Pentofuranosyl) cytosine) and itsN4-palmitoyl derivative (CS-682)

We have studied the antitumor activity and the novel DNA‐self‐strand‐breaking mechanism of CNDAC (1‐(2‐C‐cyano‐2‐deoxy‐β‐d‐arabino‐pentofuranosyl)cytosine) and its N4‐palmitoyl derivative (CS‐682). In vitro, CS‐682 showed strong cytotoxicity against human tumor cells comparable with that of CNDAC; both compounds displayed a similar broad spectrum. In vivo, however, orally administered CS‐682 showed a more potent activity against human tumor xenografts than CNDAC, 5′‐deoxy‐5‐fluorouridine, 5‐fluorouracil and 2′,2′‐difluorodeoxycytidine. Moreover, CS‐682 was effective against various human organ tumor xenografts at a wide dose range and with low toxicity, and was effective against P388 leukemic cells resistant to mitomycin‐C, vincristine, 5‐fluorouracil or cisplatin in syngeneic mice. CNDAC, an active metabolite of CS‐682, had a prolonged plasma half‐life after repeated oral administrations of CS‐682 but not after oral administrations of CNDAC itself. This difference may partially explain the higher antitumor activity of CS‐682 relative to CNDAC. In both CNDAC‐ and CS‐682‐treated carcinoma cells, CNDAC 5′‐triphosphate (CNDACTP) was generated and incorporated into a DNA strand. High performance liquid chromatography (HPLC) and mass spectrometric analysis of the nucleosides prepared by digestion of the DNA from the CNDAC‐treated cells detected ddCNC (2′‐C‐cyano‐2′,3′‐didehydro‐2′,3′‐dideoxycytidine), which was shown to be generated only when the self‐strand‐breakage of CNDACTP‐incorporated DNA occurred. The cytotoxicity of CNDAC was completely abrogated by the addition of 2′‐deoxycytidine and was low against cells with decreased deoxycytidine kinase. Our results suggest that CNDAC is converted to CNDACMP by deoxycytidine kinase and that the resulting CNDACTP incorporated into a DNA strand as CNDACMP may induce DNA‐self‐strand‐breakage. This novel DNA‐self‐strand‐breaking mechanism may contribute to the potent antitumor activity of CS‐682. Int. J. Cancer 82:226–236, 1999.

Reactivation of Suppressed RhoB is a Critical Step for the Inhibition of Anaplastic Thyroid Cancer Growth

Anaplastic thyroid carcinoma (ATC) is a highly aggressive form of the disease for which new therapeutic options are desperately needed. Previously, we showed that the high-affinity peroxisome proliferator-activated receptor gamma (PPARgamma) agonist, RS5444, inhibits cell proliferation of ATC cells via induction of the cyclin-dependent kinase inhibitor p21(WAF1/CIP1) (p21). We show here that up-regulation of RhoB is a critical step in PPARgamma-mediated activation of p21-induced cell stasis. Using multiple independently derived ATC cell lines, we found that treatment with RS5444 leads to the up-regulation of RhoB and subsequent activation of p21, and that silencing of RhoB by RNAi blocks the ability of RS5444 to induce p21 and to inhibit cell proliferation. Our results show that transcriptional regulation of RhoB by the nuclear transcription factor PPARgamma is responsible for the induction of p21 mRNA and protein. We further implicate RhoB as a key signaling effector for the growth inhibition of ATC, as treatment with a histone deacetylase inhibitor shown to increase RhoB expression in lung cancer cells caused the up-regulation of RhoB in ATC cells accompanied by increased expression of p21 and inhibition of cell proliferation; this effect occurred even in ATC cells that were unresponsive to RS5444 due to a lack of expression of PPARgamma. Our results implicate RhoB as a novel intermediate in critical signaling pathways and as an additional target for therapeutic intervention in ATC.

Anti-tumour activity of CS-7017, a selective peroxisome proliferator-activated receptor gamma agonist of thiazolidinedione class, in human tumour xenografts and a syngeneic tumour implant model.

The anti-tumour activity of the novel thiazolidinedione class peroxisome proliferator-activated receptor gamma (PPARgamma) agonist CS-7017 was investigated. CS-7017 activated PPARgamma-mediated luciferase expression with an EC(50) of 0.20 nM. In addition, CS-7017 was shown to be highly selective for PPARgamma amongst other PPAR subfamilies. CS-7017 inhibited the proliferation of the human anaplastic thyroid tumour cell line DRO and the pancreatic tumour cell line AsPC-1 in vitro at concentrations as low as 10 nM. In xenograft studies, CS-7017 inhibited the growth of the human colorectal tumour cell line HT-29 in nude mice as well as DRO in nude rats in a dose-dependent manner. At the same dose, an increase in the levels of adiponectin, a surrogate marker for PPARgamma activation, was also observed. CS-7017 prolonged the survival of mice inoculated with murine colorectal tumour Colon 38 with marginal tumour growth inhibition. These preclinical results support the potential utility of CS-7017 in a clinical setting.

Troglitazone can prevent development of type 1 diabetes induced by multiple low-dose streptozotocin in mice.

Recent investigations suggest that cytotoxic cytokines such as tumor necrosis factor (TNF)alpha and interleukin (IL)-1beta or free radicals play an essential role in destruction of pancreatic beta cells in Type 1 diabetes and that, therefore, anti-oxidant or anti-TNF alpha and IL-1beta therapy could prevent the development of Type I diabetes. Troglitazone belongs to a novel class of antidiabetic agent possessing the ability to enhance insulin action provably through activating PPAR gamma and to scavenge free radicals. In the present study, we examined whether troglitazone can prevent the development of Type 1 diabetes in multiple, low-dose streptozotocin (MLDSTZ)-injected mice. In addition, effects of troglitazone on cytokine-induced pancreatic beta cell damage were examined in vitro. Type 1 diabetes was induced by MLDSTZ injection to DBA/2 mice (40 mg/kg/day for 5 days). Troglitazone was administered as a 0.2% food admixture (240 mg/kg/day) for 4 weeks from the start of or immediately after STZ injection. MLDSTZ injection elevated plasma glucose to 615 +/- 8 mg/dl 4 weeks after final STZ injection and was accompanied by infiltration of leukocytes to pancreatic islets (insulitis). Troglitazone treatment with MLDSTZ injection prevented hyperglycemia (230 +/- 30 mg/dl) and, suppressed insulitis and TNF alpha production from intraperitoneal exudate cells. TNF alpha (10 pg/ml) and IL-1beta (1 pg/ml) addition to hamster insulinoma cell line HIT-T15 for 7 days in vitro decreased insulin secretion and cell viability. Simultaneous troglitazone addition (0.03 to approximately 3 microM) significantly improved cytokine-induced decrease in insulin secretion and in cell viability. These findings suggest that troglitazone prevents the development of Type 1 diabetes in the MLDSTZ model by suppressing insulitis associated with decreasing TNF alpha production from intraperitoneal exudate cells and the subsequent TNF alpha and IL-1beta-induced beta cell damage.

Syntheses of 1-O-carboxyalkyl GLA-60 analogues

As part of our ongoing study to survey potent LPS antagonists, the following six compounds were synthesized in an efficient manner: 3-carboxypropyl and carboxymethyl 2-deoxy-2-(2,2-difluorotetradecanamido)-4-O-phosphono-3-O-[(R)-3- (tetradecanoyloxy)tetradecanoyl]-alpha- and beta-D-glucopyranosides (11 and 23; 32 and 36), as well as the non-fluorinated equivalents, carboxymethyl 2-deoxy-4-O-phosphono-2-tetradecanamido-3-O-[(R)-3-(tetradecano yloxy)- tetradecanoyl]-alpha-D-glucopyranoside (44) and carboxymethyl 2-deoxy-2-[(R)-3-(hydroxy)tetradecanamido]-4-O-phosphono-3-O-[(R)- 3- (tetradecanoyloxy)tetradecanoyl]-alpha-D-glucopyranoside (48). Of these compounds, 32 was most pronounced in terms of LPS-antagonistic activity.

CS-706, a novel cyclooxygenase-2 selective inhibitor, prolonged the survival of tumor-bearing mice when treated alone or in combination with anti-tumor chemotherapeutic agents.

The potent chemopreventive activity of cyclooxygenase‐2 (COX‐2) inhibitors has been demonstrated in a number of preclinical studies, but their potency in antitumor activity is still in dispute. In this report, we demonstrate the potent antitumor activity of a novel COX‐2 inhibitor, CS‐706 in mouse colorectal adenocarcinoma colon 26 tumor‐bearing mice treated with or without antitumor chemotherapeutic agents. Daily oral administration of CS‐706 at doses of 3–100 mg/kg from the day of tumor inoculation (Day 0) inhibited tumor growth dose‐dependently, and the maximal inhibition was 67% at a dose of 100 mg/kg. In contrast, celecoxib, a well‐known COX‐2 inhibitor, did not inhibit tumor growth at doses up to 100 mg/kg. Furthermore, CS‐706 at a dose of 1 mg/kg or above markedly prolonged the survival time of tumor‐bearing mice. Administration of 30 mg/kg CS‐706 from Day 7 combined with a single intravenous treatment of 10 mg/kg cisplatin on Day 7 completely regressed the tumors in all tumor‐bearing mice examined, whereas only in 1 of 10 mice tumor was regressed with cisplatin treatment. Similar combination effects were observed with 10 mg/kg CS‐706 and 60 mg/kg 5‐fluorouracil (5‐FU). Moreover, 10 mg/kg CS‐706 significantly inhibited angiogenesis induced by implanted chambers with colon 26 cells in a dorsal air sac assay in mice. Collectively, these results suggest that CS‐706 is a potent antitumor agent, especially in combination with conventional chemotherapeutic agents, and that the anti‐angiogenic activity of CS‐706 may contribute at least in part to its marked antitumor activity.

The high affinity peroxisome proliferator-activated receptor-gamma agonist RS5444 inhibits both initiation and progression of colon tumors in azoxymethane-treated mice

We evaluated RS5444, a thiazolidinedione high affinity PPARγ agonist, for the ability to inhibit colon carcinogenesis in azoxymethane (AOM)‐treated mice. In our initial experiment, mice were treated with RS5444 during AOM treatment, and the drug was withdrawn 12 weeks after the last injection of AOM. RS5444 significantly inhibited aberrant crypt focus formation under these circumstances. Furthermore, exposure to RS5444 during the course of AOM treatment effectively blocked colon tumor formation after withdrawal of the agonist. PPARγ expression and nuclear localization were reduced in adenomas. RS5444 did not inhibit DNA synthesis in tumor cells, suggesting that PPARγ activity was impaired in adenomas. To test this hypothesis, pre‐existing adenomas were treated with RS5444 for 16 weeks. We observed a slight, albeit not statistically significant, reduction in tumor incidence in RS5444‐treated mice. However, histological examination revealed that tumors from RS5444‐treated mice were of significantly lower grade, as evaluated by the extent of dysplasia. Furthermore, carcinoma in situ was observed in about one‐third of control tumors, but was never observed in RS5444‐treated tumors. We conclude that RS5444 inhibits both initiation and progression of colon tumors in the AOM model of sporadic colon carcinogenesis.

Synthesis of GLA-60 type pyran carboxylic acids with an alkyl chain instead of an ester chain as LPS-antagonists

Synthesis of GLA-60 type pyran carboxylic acid analogues with an alkyl chain instead of an ester chain and their LPS-antagonist activity toward human U937 cells are described.

Lipid A-Type Pyrancarboxylic Acid Derivatives, their Synthesis and their Biological Activities

Abstract Synthesis of lipid A-type pyrancarboxylic acid derivatives, which have a carboxylic acid group in the anomeric position of the reducing sugar part of the disaccharide instead of the phosphoric acid group in lipid A, is described. We investigated the influence of the substituents in the 2′- and 6′-position of the molecules synthesized on their activities toward human monoblastic U937 cells. It was revealed that a series of compounds, possessing an acetamido group in the 2′-position showed strong LPS-antagonistic activity.