Induction of Apoptosis and Cell Cycle Arrest in Mouse Colon 26 Cells by Benastatin A

Benastatin A, isolated from Streptomyces bacteria, is reported to inhibit mammalian glutathione transferases (GSTs). Since GST inhibitors such as ethacrynic acid are suggested to induce apoptosis in some cell lines, the effect of benastatin A on the survival of mouse colon 26 adenocarcinoma cells was compared with that of ethacrynic acid. When cells in stationary phase were treated with benastatin A, viable cells were found to be dose-dependently decreased after 3 days. In the case of ethacrynic acid, this became apparent within 24 h. Electrophoretic analysis revealed DNA fragmentation, indicating that cell loss was due to apoptosis in both cases. The dominant GST in colon 26 cells was identified as the class Pi-form (GST-II), and the activities in crude extracts as well as purified GST-II were almost completely inhibited by 50 μ M ethacrynic acid. Immunoblot and northern blot analyses revealed increased GST-II protein and mRNA levels in cells treated with ethacrynic acid. Benastatin A did not significantly affect the activity in the crude extract even at 20 μ M , a 10-fold higher concentration than that which almost completely inhibited the activity of purified GST-II. However, GST activity and GST-II protein were decreased in colon 26 cells treated with benastatin A for 5 days, no significant activity being detected in the range of 16–20 μ M . In addition, β-actin and bax mRNAs were also decreased in a dose-dependent manner. Furthermore, flow cytometric analysis of colon 26 cells revealed that benastatin A blocked the cell cycle at the G1/G0 phase. Thus, benastatin A also induces apoptosis of colon 26 cells, but this is unlikely to be due to inhibition of GST activity.     

Induction of apoptosis and cell cycle arrest in mouse colon 26 cells by benastatin A.

Benastatin A, isolated from Streptomyces bacteria, is reported to inhibit mammalian glutathione transferases (GSTs). Since GST inhibitors such as ethacrynic acid are suggested to induce apoptosis in some cell lines, the effect of benastatin A on the survival of mouse colon 26 adenocarcinoma cells was compared with that of ethacrynic acid. When cells in stationary phase were treated with benastatin A, viable cells were found to be dose-dependently decreased after 3 days. In the case of ethacrynic acid, this became apparent within 24 h. Electrophoretic analysis revealed DNA fragmentation, indicating that cell loss was due to apoptosis in both cases. The dominant GST in colon 26 cells was identified as the class Pi-form (GST-II), and the activities in crude extracts as well as purified GST-II were almost completely inhibited by 50 microM ethacrynic acid. Immunoblot and northern blot analyses revealed increased GST-II protein and mRNA levels in cells treated with ethacrynic acid. Benastatin A did not significantly affect the activity in the crude extract even at 20 microM, a 10-fold higher concentration than that which almost completely inhibited the activity of purified GST-II. However, GST activity and GST-II protein were decreased in colon 26 cells treated with benastatin A for 5 days, no significant activity being detected in the range of 16 - 20 microM. In addition, beta-actin and bax mRNAs were also decreased in a dose-dependent manner. Furthermore, flow cytometric analysis of colon 26 cells revealed that benastatin A blocked the cell cycle at the G1/G0 phase. Thus, benastatin A also induces apoptosis of colon 26 cells, but this is unlikely to be due to inhibition of GST activity.     

Inhibitory Effects of Ginsenoside Rh2 on Tumor Growth in Nude Mice Bearing Human Ovarian Cancer Cells

Ginsenoside Rh₂ (Rh₂), isolated from an ethanol extract of the processed root of Panax ginseng CA Meyer, inhibits the growth of B16 melanoma cells. This study was designed to evaluate the ability of Rh₂ to inhibit growth of human ovarian cancer cells (HRA) in vitro and in nude mouse. Rh₂ inhibited proliferations of various established human ovarian cancer cell lines in a dose-dependent manner between 10 and 60 μM in vitro and induced apoptosis at around the IC₅₀ dose. When HRA cells were inoculated s.c. into the right flank of nude mice, all mice formed a palpable tumor within 14 days. Although i.p. administration of Rh₂ alone hardly inhibited the tumor growth, when Rh₂ was combined with cis-diamminedichloroplatinum(II) (CDDP) the tumor growth was significantly inhibited, compared to treatment with CDDP alone. When mice were treated p.o. with Rh₂ daily (but not weekly), the tumor growth was significantly (P<0.01) inhibited, compared to CDDP treatment alone. When Rh₂ was combined with CDDP, the degree of tumor growth retardation was not potentiated. The survival time was significantly (P<, we examined whether p.o. administration of Rh₂ has a dose-dependent inhibitory effect on the tumor growth. I.p. and weekly administration of CDDP had more potent antitumor activity in the order of 1 mg/kg, 2 mg/kg and 4 mg/kg, whereas p.o. and daily administration of Rh₂ (0.4 to 1.6 mg/kg) not only had antitumor activity comparable to that of 4 mg/kg CDDP, but also resulted in a significant increase of the survival. Doses of Rh₂ used in this study did not result in any adverse side-effects as confirmed by monitoring hematocrit values and body weight, unlike 4 mg/kg CDDP, which had severe side-effects. It is noteworthy that p.o. but not i.p. treatment with Rh₂ resulted in induction of apoptotic cells in the tumor in addition to augmentation of the natural killer activity in spleen cells from tumor-bearing nude mice. Thus, particularly in view of the toxicity of CDDP, Rh₂ alone would seem to warrant further evaluation for treatment of recurrent or refractory ovarian tumor.     

Comparison of DNA‐adduct and tissue‐available dose levels of MeIQx in human and rodent colon following administration of a very low dose

[2‐¹⁴C]2‐amino‐3,8‐dimethylimidazo[4,5‐f]quinoxaline (MeIQx) was administered orally (304 ng/kg body‐weight dose based upon an average 70‐kg‐body‐weight subject) to 5 human colon‐cancer patients (58 to 84 years old), as well as to F344 rats and B₆C₃F₁ mice. Colon tissue was collected from the human subjects at surgery and from the rodents 3.5 to 6 hr after administration. Colon DNA‐adduct levels and tissue available doses were measured by accelerator mass spectrometry (AMS). The mean levels of MeIQx in the histologically normal colon tissue were not different among the human (97 ± 26 pg MeIQx/g), rat (133 ± 15 pg/g) or mouse (78 ± 10 pg/g) tissues; and no difference existed between the levels detected in human normal and tumor tissue (101 ± 15 pg/g). Mean DNA‐adduct levels in normal human colon (26 ± 4 adducts/10¹² nucleotides) were significantly greater (p < 0.01) than in rats (17.1 ± 1 adduct/10¹² nucleotides) or mice (20.6 ± 0.9 adduct/10¹² nucleotides). No difference existed in adduct levels between normal and tumor tissue in humans. These results show that MeIQx forms DNA adducts in human colon at low dose, and that the human colon may be more sensitive to the effects of MeIQx than that of mice or rats. Int. J. Cancer 80:539–545, 1999. © 1999 Wiley‐Liss, Inc.     

Heat enhances the cytotoxicity ofcis-diamminedichloroplatinum(II) and its analoguescis-1,1-cyclobutane-dicarboxylato(2R)-2-methyl-1,4-butanediammineplatinum(II) andcis-diammine(glycolato)platinum in vitro

cis-1,1-Cyclobutanedicarboxylato(2R)-2-methyl-1,4-butanediammineplatinum(II) (NK121) andcis-diammine(glycolato)platinum (254-S), analogues ofcis-diamminedichloroplatinum (II) (CDDP) with reduced nephrotoxicity, are under clinical phase trial in Japan. Since CDDP has been shown to be more cytotoxic under conditions of an elevated temperature, we tested the cytotoxicity and cellular uptake of these analogues at 37° and 43°C using EMT6/KU cells in vitro. The cytotoxicity of CDDP was enhanced at 43°C, and that of NK121 and 254-S was also enhanced, in a dose- and time-dependent manner. The 90% cytotoxic concentration (IC₉₀) of each drug was reduced 2.9-fold for CDDP, 2.5-fold for NK121, and 2.2-fold for 254-S. Cytotoxicity was maximal when the two modalities were used simultaneously for all three drugs. The intracellular platinum concentration was assayed using flameless atomic absorption spectrophotometry. When exposed to IC₉₀ drug concentration at 43°C for 2 h simultaneously, the intracellular platinum concentration increased to 0.095±0.007 μg/10⁷ cells (a 1.9-fold increase) for CDDP, to 0.198±0.012 μg/10⁷ cells (a 1.3-fold increase) for NK121, and to 0.090±0.014 μg/10⁷ cells (a 1.3-fold increase) for 254-S; respectively, as compared with the level measured after drug exposure at 37°C (P<0.05 for all drugs). The elevation in platinum concentration may be one of mechanism related to a synegistic effect of the two treatment modalities. The concomitant use of CDDP analogues and heat shows potential for possible clinical application.     

Inhibitory effect of the novel anti-estrogen EM-800 and medroxyprogesterone acetate on estrone-stimulated growth of dimethylbenz[a]anthracene-induced mammary carcinoma in rats

The novel anti-estrogen EM-800 and medroxyprogesterone acetate (MPA) inhibit estrone (E₁)-stimulated growth of dimethylbenz[a]anthracene (DMBA)-induced mammary tumors in a rat model. After 65 days, ovariectomy (OVX) decreased total tumor area to 9.6 ± 3.9% of initial size, while E₁ (1.0 μg, s.c., twice daily) stimulated tumor growth to 225 ± 40.9% of initial size. Daily oral administration of 2.5 mg/kg body weight of EM-800 completely abolished E₁-stimulated tumor growth. A low daily dose of EM-800 (0.25 mg/kg body weight) or MPA (1 mg, s.c., twice daily) used alone partially reversed the stimulatory effect of E₁ on the growth of DMBA-induced tumors. The combination of both compounds, however, caused a more potent inhibitory effect than each compound used alone. A high dose of EM-800 completely or almost completely inhibited the E₁-stimulated vaginal and uterine weights, respectively. The same dose of EM-800 completely reversed the inhibitory effect of E₁ on serum luteinizing hormone levels. Uterine, vaginal and tumoral estrogen and progesterone receptor levels were reduced markedly following treatment with EM-800. Our data show that the combination of the pure anti-estrogen EM-800 with the androgenic compound MPA achieves greater inhibition of the growth of DMBA-induced mammary carcinoma than that achieved by each compound used alone. Int. J. Cancer 73:580–586, 1997. © 1997 Wiley-Liss, Inc.     

Combination effect of AC-7700, a novel combretastatin A-4 derivative,and cisplatin against murine and human tumors in vivo

The in vivo combination effect of AC-7700, a novel combretastatin A-4 derivative, and cisplatin (CDDP) was examined. The combination of AC-7700 and CDDP increased antitumor activity against murine colon 26 tumor in mice and cured the mice. This combination effect was found over wide dosage ranges of AC-7700 (20–80 mg/kg) and CDDP (2.5–5 mg/kg). Moreover, this combination augmented antitumor activity against murine S180 and M109 tumors, and human LX-1 and LS180 tumor xenografts in mice. The effect was the strongest when AC-7700 and CDDP were administered simultaneously. To study this combination effect we measured the concentrations of CDDP in tumors, plasma and kidneys of the mice with colon 26 tumor. In the combination with AC-7700, the concentration of CDDP in the tumors increased from 0.5 to 96 h after administration, but did not change or decrease in plasma or kidneys. Against human LS180 xenografts in mice, the combination similarly increased the concentration of CDDP in the tumors. These results suggest that AC-7700 may specifically augment the accumulation of CDDP in tumors, and thus has the potential to be useful in combination chemotherapy with CDDP. (Cancer Sci 2003; 94: 200–204)     

Changes in T lymphocyte subsets in mice with CT26 colon tumors after treatment with donor lymphocyte infusion

The objective of this study was to detect changes in T lymphocyte subpopulations in mice with CT26 subcutaneous colon cancer after treatment with donor lymphocyte infusion (DLI) and cyclophosphamide (CP) chemotherapy. A colon cancer model was established by subcutaneous injection of CT26 carcinoma cells into BALB/C mice. The mice were randomized into different treatment groups. We recorded survival times, tumor growth inhibition rates, histopathological changes, and T lymphocyte subsets in peripheral blood of the mice. Mice treated with DLI and CP survived 33.5?±?5.02 days, which was significantly longer than the survival time of untreated control mice (16.7?±?2.98 days, P?<?0.01). In addition, the tumor inhibitory rate was higher in mice treated with DLI and CP (89.3 %) than that in mice treated with CP or DLI alone (67.1 and 34.5 %, respectively). There were higher levels of T lymphocytes that were CD3⁺ and CD4⁺ in mice treated with DLI alone or the combination of CP and DLI (P?<?0.05), and the ratio of CD4⁺/CD8⁺ cells was significantly improved in these mice (P?<?0.05). DLI combined with chemotherapy significantly prolonged survival and inhibited tumor growth in mice with CT26 colon cancer. This treatment might also improve immune function in these mice. Donor spleen cells that include high numbers of allogeneic lymphocytes and a few stem cells could induce a graft-versus-tumor effect, leading to elimination of residual cancer cells. This indicates that it is potentially a feasible adoptive cellular immunotherapy strategy for the management of solid tumors.     

The Inhibitory Effect of the Combination of Antineoplaston A-10 Injection with a Small Dose of cis-Diamminedichloroplatinum on Cell and Tumor Growth of Human Hepatocellular Carcinoma

The inhibitory effects of a combination of Antineoplaston A-10 Injection with a small dose of m-diamminedichloroplatinum (CDDP) on cell and tumor growth was tested in in vitro and in vivo settings. A human hepatocellular carcinoma cell line (KIM-1) was used for the cell growth and transplanted tumor growth studies. In the cell growth study, one-hour exposure of KIM-1 cells to CDDP in the medium at concentrations of 0.5, 1.0, and 2.0 μg/ml inhibited cell growth dose-dependently. Continuous exposure of cultured cells to Antineoplaston A-10 Injection at concentrations of 4, 6, and 8 mg/ml also inhibited tumor growth dose-dependently. The combination of 0.5 μg/ml CDDP and 6 mg/ml A-10 Injection inhibited cell growth more than did each agent individually. Electron microscopic study showed well-maintained organelle structures in Antineoplaston A-10 Injection-treated cells compared to CDDP-treated cells. α-Fetoprotein (AFP) production by 10⁴ cells in 48 h increased in the A-10 Injection-treated and A-10 Injection + CDDP-treated groups as the concentration of these agents increased. In the tumor growth study, daily administration of Antineoplaston A-10 Injection 75 mg with once a week administration of 20 μg of CDDP for 5 weeks inhibited transplanted tumor growth in athymic mice after 33 days of treatment, while administration of 75 mg of A-10 Injection or 20 or 60 μg of CDDP alone showed no significant inhibition of tumor growth.     

Regional administration of natural killer cells in a rat hepatic metastasis model results in better tumor infiltration and anti-tumor response than systemic administration

A syngeneic rat liver metastasis model, the CC531 colon carcinoma cell line in Wag rats, was used to study the homing properties and anti-tumor effects of adoptively transferred, interleukin-2 (IL-2)-activated, cultured natural killer (A-NK) cells. To identify the route of administration that gives the highest tumor infiltration, 1.5 × 10⁸ A-NK cells were dyed with fluorescent rhodamine and injected via 4 different routes into rats, bearing subcapsularly induced (day 10) liver metastases. The routes chosen were: jugular vein, portal vein, hepatic artery and directly into the peritoneal cavity (i.p). The rats were sacrificed 20 hr after administration of A-NK cells. The highest (p < 0.05) infiltration of tumors by A-NK cells was found both at the tumor border and in the tumor center after injection via the hepatic artery: 65 ± 7 A-NK cells/mm² at the tumor border and 26 ± 14 A-NK cells/mm² in the center of the tumor (jugular vein infusion: 32 ± 10 and 9 ± 5 A-NK cells/mm², respectively; portal vein infusion: 36 ± 13 and 7 ± 4 A-NK cells/mm², respectively). No A-NK cells were detected in the liver after i.p. injection. Rats bearing day 5 tumors were injected with 1.5 × 10⁸ A-NK cells via the hepatic artery or via the jugular vein (n = 5 and n = 6 respectively). Regional administration of A-NK cells via the hepatic artery resulted in a significant (p < 0.05) lower weight (35 ± 23 mg) of tumors than did systemic administration (70 ± 10 mg). Our results suggest that both the level of tumor infiltration by adoptively transferred A-NK cells and the therapeutic outcome depend on the route of administration. Int. J. Cancer 75:233–238, 1998. © 1998 Wiley-Liss, Inc.     

Protection by WR-2721 of the toxicity induced by the combination of cisplatin and 5-fluorouracil.

We evaluated the effects of WR-2721 and its metabolite WR-1065 on in vitro growth inhibition by 5-fluorouracil (5FU) and cisplatin (CDDP) and the effect of WR-2721 on in vivo toxicity and antitumor effect of 5FU and CDDP. In cell culture both WR-2721 and WR-1065 were not able to reverse growth inhibition caused by either 5FU or CDDP. Administration of WR-2721 i.p. at 525 mg/kg to mice resulted in a severe temperature drop to 27 degrees C; at 200 mg/kg hypothermia was less severe. WR-2721 failed to prevent 5FU toxicity, but the maximum tolerated dose of CDDP in the combination with 5FU (at 100 mg/kg) could be increased from 3 to 7 mg/kg. CDDP at 7 mg/kg enhanced leukopenia caused by 5FU at 100 mg/kg to 20% and thrombocytopenia to 40%; WR-2721 reduced leukopenia and prevented thrombocytopenia induced by the combination. Combination of CDDP, 5FU, and WR-2721 resulted in an enhanced antitumor activity against the murine colon tumor Colon 26 compared to 5FU alone and to 5FU combined with CDDP at their maximum tolerated dose.     

Antitumor effects of novel compound,guttiferone K,on colon cancer by p21Waf1/Cip1‐mediated G0/G1 cell cycle arrest and apoptosis

Low selectivity is one of the major problems of currently used anticancer drugs, therefore, there is a high demand for novel, selective antitumor agents. In this study, the anticancer effects and mechanisms of guttiferone K (GUTK), a novel polyprenylated acylphloroglucinol derivative isolated from Garcinia cowa Roxb., were examined for its development as a novel drug targeting colon cancer. GUTK concentration‐ and time‐dependently reduced the viability of human colon cancer HT‐29 cells (IC₅₀ value 5.39 ± 0.22 μM) without affecting the viability of normal human colon epithelial CCD 841 CoN cells and induced G₀/G₁ cell cycle arrest in HT‐29 cells by down‐regulating cyclins D1, D3 and cyclin‐dependent kinases 4 and 6, while selectively restoring p21Waf1/Cip1 and p27Kip1 to levels comparable to those observed in normal colon cells, without affecting their levels in normal cells. GUTK (10.0 μM) induced cleavage of PARP, caspases‐3, ‐8 and ‐9 and chromatin condensation to stimulate caspase‐3‐mediated apoptosis. The addition of a JNK inhibitor, SP600125, partially reversed GUTK‐induced caspase‐3 activity, indicating the possible involvement of JNK in GUTK‐induced apoptosis. Furthermore, GUTK (10 mg/kg, i.p.) significantly decreased the tumor volume in a syngeneic colon tumor model when used alone or in combination with 5‐fluorouracil without toxicity to the mice. Immunohistochemical staining of the tumor sections revealed a mechanism involving an increase in cleaved caspase‐3 and a decrease in cell proliferation marker Ki‐67. Our results support GUTK as a promising novel, potent and selective antitumor drug candidate for colon cancer.     

Low‐intensity ultrasound and microbubbles enhance the antitumor effect of cisplatin

Cell permeabilization using microbubbles (MB) and low‐intensity ultrasound (US) have the potential for delivering molecules into the cytoplasm. The collapsing MB and cavitation bubbles created by this collapse generate impulsive pressures that cause transient membrane permeability, allowing exogenous molecules to enter the cells. To evaluate this methodology in vitro and in vivo, we investigated the effects of low‐intensity 1‐MHz pulsed US and MB combined with cis‐diamminedichloroplatinum (II) (CDDP) on two cell lines (Colon 26 murine colon carcinoma and EMT6 murine mammary carcinoma) in vitro and in vivo on severe combined immunodeficient mice inoculated with HT29‐luc human colon carcinoma. To investigate in vitro the efficiency of molecular delivery by the US and MB method, calcein molecules with a molecular weight in the same range as that of CDDP were used as fluorescent markers. Fluorescence measurement revealed that approximately 10⁶–10⁷ calcein molecules per cell were internalized. US–MB‐mediated delivery of CDDP in Colon 26 and EMT6 cells increased cytotoxicity in a dose‐dependent manner and induced apoptosis (nuclear condensation and fragmentation, and increase in caspase‐3 activity). In vivo experiments with xenografts (HT29‐luc) revealed a very significant reduction in tumor volume in mice treated with CDDP + US + MB compared with those in the US + CDDP groups for two different concentrations of CDDP. This finding suggests that the US–MB method combined with chemotherapy has clinical potential in cancer therapy. (Cancer Sci 2008; 99: 2525–2531)     

Activity of Aztreonam in Pneumology,Part 2: Influence on Phagocytosis and Intracellular Killing of Human Alveolar Macrophages

Summary

The study aim was to evaluate the activity of aztreonam on phagocytosis and intracellular killing of Staphylococcus aureus ATCC6538 by human alveolar macrophages. Drug concentrations of 1, 10, 25, 100 μg/ml were assayed in culture medium.

Aztreonam induces dose-dependent phagocytosis up to 25 μg/ml concentrations; with a phagocytosis index (PIa) of 1.18 ± 0.2 at 1 μg/ml; of 1.27 ± 0.2 at 10 μg/ml; of 1.42 ± 0.3 at 25 μg/ml. No phagocytosis increase or inhibition, with unchanged cell viability compared to controls, is shown at 100 μg/ml aztreonam (PI 1.03 ± 0.3). Intracellular killing acts in a similar way: the killing index (KIa) is 1.27 ± 0.3 at 1 μg/ml concentrations; 1.38 ± 0.3 at 10 μg/ml; 1.61 ± 0.4 at 25 μg/ml whereas at 100 μg/ml the KIa is 1.03 ± 0.3. This study shows aztreonam's ability to stimulate macrophages' functional activity against a microorganism (S. aureus) which is not susceptible to its antibacterial activity.     

Tumor cell lysate-pulsed dendritic cells induce a T cell response against colon cancer in vitro and in vivo

To investigate whether tumor cell lysate-pulsed (TP) dendritic cells (DCs) induce cytotoxic T lymphocyte (CTL) activity against colon cancer in vitro and in vivo. Hematopoietic progenitor cells were magnetically isolated from BALB/c mice bone marrow cells. These cells were cultured with cytokines GM-CSF, IL-4, and TNFα to induce their maturation. They were analyzed by morphological observation and phenotype analysis. DCs were pulsed with tumor cell lysate obtained by rapid freezing and thawing at a 1:3 DC:tumor cell ratio. CTL activity and interferon gamma (IFNγ) secretion was evaluated ex vivo. In order to determine whether or not vaccination with CT26 TP DCs induce the therapeutic potential in the established colon tumor model, CT26 colon tumor cells were implanted subcutaneously (s.c.) in the midflank of naïve BALB/c mice. Tumor-bearing mice were injected with vaccination with CT26 TP DCs on days 3 and 10. Tumor growth was assessed every 2–3 days. Finally, CTL activity and IFNγ secretion were evaluated in immunized mice. Hematopoietic progenitor cells from mice bone marrow cells cultured with cytokines for 8 days showed the character of typical mature DCs. Morphologically, these cells were large with oval or irregularly shaped nuclei and with many small dendrites. Phenotypically, FACS analysis showed that they expressed high levels of MHC II, CD11b, CD80, and CD86 antigen, and were negative for CD8α. However, immature DCs cultured with cytokines for 5 days did not have typical DCs phenotypic markers. Ex vivo primed T cells with CT26 TP DCs were able to induce effective CTL activity against CT26 tumor cells, but not B16 tumor cells (E:T = 100:1, 60.36 ± 7.11% specific lysis in CT26 group vs. 17.36 ± 4.10% specific lysis in B16 group), and produced higher levels of IFNγ when stimulated with CT26 tumor cells but not when stimulated with B16 tumor cells (1210.33 ± 72.15 pg/ml in CT26 group vs. 182.25 ± 25.51 pg/ml in B16 group, P < 0.01). Vaccination with CT26 TP DCs could induce anti-tumor immunity against CT26 colon tumor in murine therapeutic models (tumor volume on day 19: CT26 TP DCs 342 ± 55 mm³ vs. the other control groups, P < 0.05). In addition, all splenic CD3⁺ T cells obtained from mice vaccinated with CT26 TP DCs produced high levels of IFNγ and shown specific cytotoxic activity against CT26 tumor cells, but no cytotoxic activity when stimulated with B16 tumor cells. Tumor cell lysate-pulsed DCs can induce tumor-specific CTL activity against colon cancer in vitro and in vivo.     

Schedule dependent tumour growth delay,DNA cross-linking and pharmacokinetic parameters in target tissues with cis-diamminedichloroplatinum(II) and etanidazole with or without hyperthermia or radiation

It has been reported previously that striking increases in tumour growth delay and cytotoxicity are seen when cis-diamminedichloroplatinurn(II) (CDDP) is combined with mild local hyperthermia (43°C, 30 min) and/or etanidazole (ETA). This paper reports a study of CDDP pharmacology and the in vivo tumour DNA cross-linking produced by these combinations. In C3H mice bearing the FSaIIC murine fibrosarcoma, Pt plasma pharmacokinetics were not significantly altered by any of the combination of treatments. Although ETA caused no significant change in CDDP tissue pharmacokinetics, treatment of the tumour-bearing limb with hyperthermia immediately following an i.p. injection of CDDP (10 mg/kg) resulted in an increased peak Pt concentration (3.5 versus 2.8 μg Pt/g tumour wet weight) and doubled the t_1/2 elimination of Pt (15 to 30 h) from the tumour. Similar heat-induced changes were observed in the Pt pharmacokinetics in skin. There was about a three-fold increase in the Pt area under the curve (AUC) for the tumour, a 1.5-fold increase in the AUC for skin and little change in the AUC for muscle with hyperthermia. When the tumour DNA cross-linking factor (CLF) was determined, it was found that local hyperthermia treatment (43°C, 30 min) increased the CLF of CDDP from 1.7 to 2.7 and hyperthermia (43°C, 1 h) further increased the CLF to 6.1. Misonidazole (MISO) (1 g/kg) increased the CDDP CLF to 2.0, 6.3 and 15.1 in conjunction with 37, 43 (30 min) and 43°C (1 h), respectively. ETA (1 g/kg) was more effective than MISO at increasing the CDDP CLF, producing CLFs of 2.8, 9.1 and 21.5 at 37, 43 (30 min) and 43°C (1 h), respectively. These changes in CLF were reflected in an increased tumour growth delay in the FSaIIC murine fibrosarcoma with CDDP (5 mg/kg) alone from 4.4 to 5.9 days with 43°C (30 min) and then to 11.9 days with ETA (1 g/kg) and 20.9 days with both ETA and local hyperthermia (43°C, 30 min). When CDDP, ETA and hyperthermia were added to a radiation schedule of 300 cGy daily for five days, it was found that giving ETA (1 g/kg), CDDP (5 mg/kg) and hyperthermia (43°C, 30 min) together on day 1 produced the largest tumour growth delay (43 days) and that other schedules which divided the dose of ETA over the other days of the radiation treatment (including one schedule with a second heat treatment on day 4) were significantly inferior. Thus, local hyperthermia increased tumour versus normal tissue exposure to Pt, probably by altering the vascular physiology of the tumour, and both hyperthermia and ETA markedly increased CDDP-induced DNA damage, leading to commensurate increases in tumour growth delay. These results suggest that the addition of both ETA and hyperthermia to CDDP should be effective clinically, and they indicate that treatment once a week with hyperthermia, CDDP and ETA at the maximum tolerated dose will be the most successful.     

Inhibition of methionine uptake by CIS-diamminedichloroplatinum (II) in experimental brain tumors

cis-diamminedichloroplatinum (II) (CDDP) has been used both alone and in combination with other chemotherapeutics for cancer chemotherapy. Although CDDP acts primarily on DNA, it can also act at the tumor-cell membrane to inhibit methionine transport. The latter mechanism of CDDP is reported to have an important role as a chemical modulator in enhancing chemotherapeutic effects of 5-fluorouracil in tumor cells. We report here the effects of CDDP on methionine uptake in an in vivo brain-tumor model. C6 brain-tumor cells were stereotactically inoculated in the right basal ganglia of 6-week-old male Sprague-Dawley rats. Ten days after the inoculation, autoradiographic images were obtained using (¹⁴C-methyl)-L-methionine. The tracer uptake, represented as differential absorption ratio (DAR) and an acid-insoluble fraction (AIF), was measured in both brain tumors and normal brain with or without an intravenous injection of CDDP. The tumor/non-tumor DAR and AIF decreased significantly (P < 0.01, as determined by the Mann-Whitney U-test) after CDDP treatment, whereas the non-tumor DAR and AIF remained almost unchanged. These findings indicate that CDDP inhibits methionine uptake selectively in brain-tumor tissue and may therefore be a potent chemical modulator in the chemotherapy of brain tumors. © 1996 Wiley-Liss, Inc.     

Establishment of a cisplatin-resistant gastric carcinoma cell line OCUM-2M/DDP

 A cis-diamminedichloroplatinum (CDDP)-resistant scirrhous gastric cancer cell line, OCUM-2M/DDP, was established by chronic exposure of cells of the parent scirrhous gastric cancer cell line, OCUM-2M, to CDDP at progressively increasing concentrations. The OCUM-2M/DDP cell line had an 11.3-fold higher level of resistance relative to its parent cell line as determined by a succinate dehydrogenase inhibition test. The biological and biochemical characteristics of the resistant and parent cell line were compared. There were differences in the modal chromosome number and DNA index, suggesting that some alterations of the DNA in the CDDP-resistant cells had occurred. Neither the parent nor resistant cell line expressed mdr-1 mRNA. After exposure to CDDP for 4 h, the intracellular platinum content of OCUM-2M cells was significantly higher than that of OCUM-2M/DDP cells (51.9±1.8 vs 16.4 plus 1.0 ng/mg protein, mean±SD, respectively). The GSH levels in OCUM-2M cells and OCUM-2M/DDP cells were 3.5±1.0 μg/mg protein and 16.8±1.2 μg/mg protein, respectively. These levels were also significantly different. These findings suggest that the possible mechanisms of resistance to CDDP in OCUM-2M/DDP cells may be a decrease in intracellular CDDP accumulation and detoxication by GSH. This OCUM-2M/DDP cell line could be used in further investigations of the mechanism of CDDP resistance in gastric cancer. Received: 16 August 1996 / Accepted: 16 November 1996     

Distinct P-glycoprotein expression in two subclones simultaneously selected from a human colon carcinoma cell line by cis-diamminedichloroplatinum (II)

Two drug-resistant sublines, CP2.0 and RT, were simultaneously selected by cis-diamminedichloroplatinum (CDDP) from the human colon carcinoma cell line LoVo by the conventional method of continuous drug exposure. The 2 sublines differed in morphology, growth kinetics and pattern of gene expression. Genetic signature analysis indicated that the lines were independent subclones but that both arose from LoVo. These sublines were maintained in a growth medium containing 2.0 μg/ml CDDP. However, CP2.0 cells were 3 times more resistant to CDDP than were RT cells. Although both were cross-resistant to mustargen and 5-fluorouracil, only CP2.0 was resistant to Adriamycin and vincristine. Western-blot analysis, immunocytochemical staining and in vitro phosphorylation experiments indicated that the level of P-glycoprotein was significantly elevated in CP2.0 but not in RT. Despite the differences between these sublines, they possess similar CDDP-resistance mechanisms, including decreased intracellular CDDP accumulation, elevated levels of glutathione and metallothionein-like proteins, increased glutathione transferase-μ mRNA, and enhanced susceptibility to CDDP cytotoxicity after treatment with DL-buthionine-[S,R]-sulfoximine. Nevertheless, our results suggest that, in certain tumor types, P-glycoproteinmediated multi-drug resistance and CDDP-resistance phenotypes can coexist in cells with primary resistance to CDDP.     

Combined effect of S-1 and CDDP as a modulator for colon 26 liver metastasis

S-1 is a novel oral anticancer drug, composed of tegafur (FT), gimestat (CDHP) and otastat potassium (Oxo) in a molar ratio of 1:0.4:1, based on the biochemical modulation of 5-fluorouracil (5-FU). In this study the combined effect of S-1 and low-dose CDDP as a modulator for colon 26 liver metastasis in mice was evaluated. In an experiment with S-1 (5 mg/kg/day: po) and CDDP (0.25 mg/kg/day: i.p.) for 14 days, the combined effects for both liver metastasis and tumor of spleen were not superior to those with S-1 or CDDP alone group. Body weight loss was not greater in the S-1 + CDDP group than in the control group. In an experiment with S-1 (5 mg x 2/kg/day: po) and CDDP (0.25 mg/kg/day: i.p.) for 7 days, the inhibitory effects of S-1 + CDDP of liver metastasis and tumor of the spleen were remarkable compared with the S-1 alone group. However a greater loss of body weight was seen in the S-1 + CDDP group than in other groups. This study suggests that low-dose CDDP might be a modulator of S-1 for colon 26 liver metastasis. Further study is needed to determine the optimum dose and duration of treatment.