The target killing effect of cRGD-modified Zinc-doped dendritic mesoporous silicon carrier delivering disulfiram against colorectal cancer CT26 cells / 中国肿瘤生物治疗杂志

@#[摘 要] 目的：制备一种精氨酸-甘氨酸-天冬氨酸环肽（cRGD）修饰、Zn2+掺杂并负载双硫仑（DSF）的树枝状介孔硅纳米颗粒，初步研究其对结直肠癌CT26细胞的靶向杀伤作用。方法：采用水热合成法将Zn2+锚定在树枝状介孔硅纳米颗粒的骨架中，再将DSF负载在介孔孔道中，偶联靶向配体cRGD到纳米颗粒的表面，得到具有靶向功能的纳米颗粒DSF@Zn-DMSN-cRGD。采用透射电镜（TEM）检测DSF@Zn-DMSN-cRGD的表面形貌，通过能谱面扫得到元素映射图验证其中的元素分布，通过激光粒度仪检测其粒径与电位变化，使用红外光谱仪检测表面主要化学键。通过TEM观察载体Zn-DMSN在pH6.5和pH7.4的模拟体液中共培养后的形态，采用细胞摄取实验检测cRGD修饰的Zn-DMSN靶向CT26细胞的能力，采用CCK-8法、Calcein-AM/PI染色法和流式细胞术检测DSF@Zn-DMSN-cRGD对CT26细胞的杀伤能力及对细胞凋亡的影响。结果：TEM观察表明DSF@Zn-DMSN-cRGD表面具有多孔径，元素映射结果显示Zn元素和DSF成功负载在纳米颗粒表面，红外光谱仪检测结果表明cRGD成功偶联在DSF@Zn-DMSN介孔硅复合载体的表面，电位粒径结果显示粒径较未偶联cRGD前稍大，电位明显增加（P<0.000 1），TEM观察发现Zn-DMSN在微酸性环境中其骨架崩解明显增多，细胞摄取实验结果表明经cRGD修饰后的Zn-DMSN被CT26细胞内吞的效率显著增加（P<0.05）。CCK-8法、Calcein-AM/PI染色法和流式细胞术检测结果说明DSF@Zn-DMSN-cRGD能够高效杀伤CT26细胞（均P<0.000 1）并诱导细胞发生凋亡（均P<0.000 1），而对正常地肠上皮细胞NCM460无明显损伤。结论：成功合成了一种掺杂锌、负载DSF并偶联cRGD的纳米颗粒DSF@Zn-DMSN-cRGD，其载体Zn-DMSN骨架具有良好的pH降解性，其中的cRGD能促进纳米颗粒被CT26细胞靶向内吞；在体外实验中，Zn-DMSN-cRGD能够对结直肠癌CT26细胞产生强烈的靶向细胞毒性。

Effect and mechanism of MLL5 knock-out on the growth of colon cancer CT26 cell transplanted tumor / 中国肿瘤生物治疗杂志

@#[摘 要] 目的：探讨混合谱系白血病5（MLL5）基因在小鼠结肠癌CT26细胞移植瘤生长中的作用及其分子机制。方法：利用CRISPR/Cas9技术构建MLL5基因缺失、MLL5和DDX58双基因缺失的结肠癌CT26细胞模型，用Sanger测序和WB法验证敲除效果。将基因敲除的CT26细胞接种到野生型BALB/c小鼠和免疫缺陷型NSG小鼠皮下，构建基因缺失结肠癌CT26细胞移植瘤小鼠模型，并观察移植瘤的生长及荷瘤小鼠的总生存期（OS）。结果：在野生型小鼠中，MLL5基因缺失的CT26细胞移植瘤生长速度显著性低于野生型癌细胞移植瘤，并延长荷瘤小鼠的OS（P<0.01）；在NSG小鼠中，MLL5基因缺失对CT26细胞移植瘤的生长速度以及荷瘤小鼠的OS没有明显改变。MLL5基因缺失提高了癌细胞中视黄酸诱导基因1（RIG-1）蛋白水平，DDX58基因缺失可逆转MLL5基因缺失在CT26细胞移植瘤中的作用。结论：MLL5基因缺失可提高结肠癌CT26细胞中RIG-1蛋白水平、促进肿瘤免疫，从而抑制荷瘤小鼠肿瘤生长，提示MLL5可能成为结肠癌治疗的新靶点。

Effect of different injection approaches of tumor RNA nanoliposome vaccine on the growth of colon cancer / 药学实践杂志

Objective To compare the differences in the anti-tumor growth effects of organisms with different injections of CT26 tumor cell RNA loaded into nanoliposomes. Methods The extracted tumor RNA was loaded into nanoliposomes to prepare tumor RNA nanoliposome vaccines, and the related properties of nanoliposome vaccines were investigated. The particle size of nanoliposome vaccines was （120.0±12.1）nm and zeta potential was （3.39±0.56）mV. Tumor RNA nanoliposome vaccines were injected into different parts of the mice to test and analyze the influence of different injections on the growth of colon cancer transplanted tumors in mice. Results Tumor RNA nanoliposome vaccines were used to inject tumor-transplanted mice in different ways. Compared with underarm injection, intraperitoneal injection enhanced the organism's anti-tumor immune response and inhibited the growth of transplanted tumors more effectively. The H&E staining of important organs in mice was compared and no obvious organic lesions were found in the organs. Conclusion Intraperitoneal injections of nanoliposome loaded with tumor RNA can enhance the body's anti-tumor immune response more effectively than underarm injections.

Study of the mechanism of anti-tumor effect of Metformin-enhanced radiotherapy in CT26WT cell lines or mouse models with transplanted tumors / 中华放射肿瘤学杂志

Objective To investigate the inhibitory effect and mechanism of Metformin (Met) combined with irradiation in CT26WT cell lines or mouse models with transplanted tumors.Methods CT26WT cell line was treated with 0.5 μmol/L,1.0 μmol/L,5.0 μmol/L and 10.0 μmol/L Met,and CellTiter Glo kit was used to detect the inhibitory effect of Met at different concentrations on the viability of CT26WT cells.CT26WT cell line was treated with the control,Met (10 pmol/L),15 Gy irradiation and 15 Gy irradiation+Met (10 μmol/L).Clone formation assay was employed to detect the cell proliferation activity.Bablc mouse models of transplanted tumors (tumor size＞ 150 mm3) were established and randomly divided into the control,15 Gy irradiation,Met and 15Gy irradiation+Met groups.Mice were given with 750 mg/kg Met at 24 h before irradiation.Transplanted tumor volume was measured regularly to delineate the growth curve of transplanted tumors and survival curve.The expression levels of P-H2AX and Sting proteins in CT26WT cells and transplanted tumors were detected by Western blot.The infiltration of CD8a (+) T cells in transplanted tumor tissues was detected by immunohistochemistry.Results The relative cell survival rate was 100％,87.9％,87.8％,87.3％ and 76.5％ in the 0,0.5,1.0,5.0 and 10.0μmol/L Met groups,respectively (all P＜0.05).The inhibitory effect of 10.0 μmol/L was significantly stronger than that of 5.0 μmol/L (P＜0.001).The colone formation rate 34.0％,24.0％,22.3％ and 14.0％ in the control,Met,15 Gy irradiation,Met+ 15Gy irradiation groups,respectively (all P＜0.001).Western blot showed that compared with the control group,the expression of Sting protein was increased by 2.99-fold after Met treatment (P＜0.001),and increased by 1.37-fold and 4.41-fold in the 15 Gy irradiation and 15Gy irradiation+Met groups (both P＜0.01).Compared with the 15 Gy irradiation group,the expression of P-H2AX protein was significantly increased by 1.43 times after treatment with 15Gy+Met (P＜0.001).The transplanted tumor growth curve showed that the transplanted tumor growth in the 15 Gy+Met group was slower than that in the control group[(1007.0± 388.5) mm3 vs.(2639.0± 242.9) mm3,P＜ 0.05)].The overall survival time in the 15 Gy irradiation+Met group was 48 d,significantly longer than 32 d in the control group (P＜0.001).Compared with the control group,the expression of P-H2AX and Sting proteins in the 15 Gy+ Met group was increased by 8.8-fold and 1.6-fold (both P＜0.001).Immunohistochemical staining showed that the infiltration of CD8a (+) T cells in the 15 Gy irradiation+Met group was significantly higher than that in the control group (P＜0.01).Conclusions Met combined with radiotherapy can inhibit the proliferation and clone formation of colon cancer cells,probably by aggravating DNA damage and activating the Sting signaling pathway,eventually leading to the increase of CD8a (+) T cells in tumor tissues and enhancing the killing effect upon transplanted tumor cells.

Chidamide enhances inhibitory effect on colon cancer cells by modulating tumorassociated macrophage / 中国肿瘤生物治疗杂志

@# Objective: To investigate the effect of tumor-associated macrophage (TAM) on the anti-tumor function of chidamide and to explore the mechanism. Methods: Mouse macrophage cell linesAna1 and Raw264.7 were cultured in vitro and induced into TAM with tumor supernatant. HDAC enzyme activity was detected after TAM treated with chidamide. The mRNA expressions of cytokines, such as IL-6, IL-12,TNF and IL-1β, in TAM were detected by qPCR. The protein expression of NF-κB and STAT3 in TAM treated with chidamide were detected by Wb. The mixture of TAM and colon cancer CT26 cells was inoculated into nude mice to construct the subcutaneous xenograft model; and the efficacy of chidamide (3.87 mg/kg) on the growth of CT26 xenograft tumors was observed. The protein expressions of PCNA, F4/80, Arg1 and iNos were detected by immunohistochemistry. Results: Chidamide inhibited the proliferation of CT26 cells. In the in vivo experiment, the inhibition rate of chidamide alone on CT26 xenograft was about 18.7%; however, the inhibition rate was up to 57.2% with the presence of TAM. Chidamide could inhibit the activity of HDAC enzyme in TAM, and further increase the Histone acetylation level. Chidamide could affect the expression of nuclear transcription factor NF-κB, inhibit the expressions of Arg1, IL-6 and IL-12, but up-regulate the expressions of iNOS, TNF and IL-1β in TAM. Conclusion: Chidamide can enhance its inhibitory effect on colon cancer CT26 cells via regulating the expression of cytokines and inhibiting the activity of HDAC in TAM.

Screening of monomers from traditional Chinese medicine for specifically inhibiting brafV600E CT26 cells / 中国药理学通报

Aim: To screen BRAFV600E CT26 cell inhibitors from monomers of traditional Chinese medicine (TCM). Methods CT26 cell line was constructed with lentivirus plasmid to stably express BRAFV6C0E. The proliferation, migration and expression of related proteins in MEK/ERK signaling pathway were detected. The monomers of TCM were detected for biological activities as potential BRAF inhibitors by Discovery Studio 4. 0, and further evaluated by MTT assay. Results: The proliferation and migration of BRAFV6C0E CT26 cells were obviously strengthened compared with wild type control. The expressions of proteins in MEK/ ERK pathway were also activated in BRAFV6C0E CT26 cells. Compared with wild type control, Aloin, Angoroside C and Cyasterone exhibited the potent effect against BRAFV600E in CT26 cells (P <0. 05), and could down-regulate the expression of BRAFV600E. Conclusion: Aloin, Angoroside C, Cyasterone might be the potent inhibitors against BRAF for colon treatment.

Structural characterization of Sophora alopecuroides polysaccarides and study on its antitumor activity of CT26 / 中草药

Objective: To study the structure of Sophora alopecuroides polysaccarides (SAP) and its antitumor activity on CT26 transplanted tumor in mice. Methods: The structure was characterized by high-performance gel permeation chromatography (HPGPC), gas chromatography-mass spectrometer (GC-MS), infrared spectroscopy (IR), and nuclear magnetic resonance spectroscopy (NMR). And then the anticancer activity of CT26-bearing mice was investigated in vivo. Results: The results showed that SAP was consisted of D-mannopyranose and D-galactopyranose residues. The main chain of the galactomannan comprises β-(1,4)-linked D-mannopyranose residues, with branches of galactose, linked to the carbohydrate core through α-D-Gal (1,6) linkage. SAP could inhibit the tumor proliferation of CT26-bearing mice in a dose-dependent manner with inhibitory rate of 44.03% at high dose. Conclusion: Structure determination of SAP provides the theoretical basis for structure-activity relationship study. And it is expected to be further developed as a new antitumor drug with high efficiency and low toxicity.

Identification of dysregulated microRNA expression and their potential role in the antiproliferative effect of the essential oils from four different Lippia species against the CT26.WT colon tumor cell line

ABSTRACT In spite of advances in colorectal cancer treatments, approximately 1.4 million new global cases are estimated for 2015. In this sense, Brazilian plant diversity offers a multiplicity of essential oils as prospective novel anticancer compounds. This study aimed to evaluate the antiproliferative effect of the essential oils from four Lippia species in CT26.WT colon tumor cells, as a measurement of cell cycle phase distribution and microRNA expression. CT26.WT showed cell cycle arrest at G2/M phase after treatment with 100 µg/ml of Lippia alba (Mill.) N.E.Br. ex Britton & P. Wilson, Lippia sidoides Cham., and Lippia lacunosa Mart. & Schauer, Verbenaceae, essential oils and, at the same concentration, Lippia rotundifolia Cham. essential oil caused an augment of G0/G1 phase. The miRNA expression profiling shows change of expression in key oncogenic miRNAs genes after treatment. Our findings suggest growth inhibition mechanisms for all four essential oils on CT26.WT cells involving direct or indirect interference on cell cycle arrest and/or oncogenic miRNAs expression.

Anti-tumour immune effect of oral administration of Lactobacillus plantarum to CT26 tumour-bearing mice.

Colorectal cancer (CRC) is one of the most prevalent forms of cancer that shows a high mortality and increasing incidence. There are numerous successful treatment options for CRC, including surgery, chemotherapy, radiotherapy and immunotherapy; however, their side effects and limitations are considerable. Probiotics may be an effective strategy for preventing and inhibiting tumour growth through stimulation of host innate and adaptive immunity. We investigated and compared potential anti-tumour immune responses induced by two isolated Lactobacillus strains, Lactobacillus plantarum A and Lactobacillus rhamnosus b, by pre-inoculating mice with lactobacilli for 14 days. Subsequently, subcutaneous and orthotopic intestinal tumours were generated in the pre-inoculated mice using CT26 murine adenocarcinoma cells and were assessed for response against the tumour. Our results indicated that oral administration with L. plantarum inhibited CT26 cell growth in BALB/c mice and prolonged the survival time of tumour-bearing mice compared with mice administered L. rhamnosus. L. plantarum produced protective immunity against the challenge with CT26 cells by increasing the effector functions of CD8+ and natural killer (NK) cell infiltration into tumour tissue, up-regulation of IFN-γ (but not IL-4 or IL-17) production, and promotion of Th1-type CD4+ T differentiation. Consequently, our results suggest that L. plantarum can enhance the anti-tumour immune response and delay tumour formation.

Effect of emodin on Treg cells function in a mouse model of CT26 colon cancer / 实用医学杂志

Objective To investigate the effect of emodin on immune suppression function of regulatory T cells in a mouse model of CT26 colon cancer. Methods Twenty-four mice were divided into the negative control group, the emodin group and the tumor group. The populations of CD8+CD3+T cells, the T cells producing IFN-γand the CD4+CD25+Tregs secreting IL-10 in different mouse tissues were detected by flow cytometry. Levels of IFN-γ, TNF- β1 and IL-10 in serum were determined by ELISA. Results Emodin could significantly increase the percent of CD8+CD3+T cells in tumor (P < 0.05) and improve the ability of IFN-γ secretion in T cells from peripheral blood and lymph nodes (P < 0.05). Emodin could reduce the levels of IFN-γ, TNF-β1 and IL-10 in the serum (P < 0.01) and inhibit IL-10 secretion in CD4+CD25+ Tregs (P < 0.01). Conclusion Emodin possesses the antitumor effect by affecting the immunosuppressive function of Tregs cells.

Inhibition of Colon Cancer Cells by Ethanol Extract of Oldenlandia Diffusa / 昆明医科大学学报

Objective To explore the inhibitory effect of the ethanol extract of Oldenlandia diffusa on the proliferation of CT-26 colon cancer cells which come from BALB/c mice. Method We determined the inhibitory effect of different concentrations of ethanol extract of Oldenlandia diffusa on CT-26 cells' proliferation by using methyl thiazolyl tetrazolium (MTT), and calculated the 50% inhibiting concentration (IC50) . Results As to the same concentration, the inhibitory effect of the ethanol extract of Oldenlandia diffusa on CT-26 cells was increased with time, for exsample:after treated with 0.08 mg/mL of ethanol extract of Oldenlandia diffusa for 24 h, 48 h and 72 h, the inhibitory rates of CT-26 cells were (16.67 ±9.35)%, (34.66 ±9.23)%and (40.07 ±9.16)%, respectively. After treating CT-26 cancer cells for 24 h, 48 h and 72 h, the IC50 values of the ethanol extract of Oldenlandia diffusa were 0.315,0.155 and 0.115 mg/mL, respectively. In the same treatment time, the inhibitory effect of the ethanol extract of Oldenlandia diffusa on CT-26 cells was increased with the increase of concentration:after treatment for 72 h with different concentrations (0.06 mg/mL,0.08 mg/mL,0.10 mg/mL,0.12 mg/mL, 0.14 mg/mL,0.16 mg/mL,0.18 mg/mL and 0.20 mg/mL) of the ethanol extract of Oldenlandia diffusa,the inhibitory rates of CT-26 cells were (35.46 ±3.59)%, (40.07 ±9.16)%, (40.77 ±6.92)%, (52.81 ±1.87)%, (54.22±2.35)%, (68.72±3.71)%, (70.04±8.03)%and (71.84±3.12)%, respectively. Conclusion The ethanol extract of olenlandia diffusa can inhibit the proliferation of CT-26 colon cancer cells from BALB/c mice in a time and dose dependent manner.

Inhibitory Effect of Ethanol Extract of Oldenlandia Diffusa on Colorectal Cancer Angiogenesis in BALB/c Mice / 昆明医科大学学报

Objective To explore the inhibitory effect of Oldenlandia diffusa extract on colorectal cancer angiogenesis in BALB/c mice. Methods Thirty-two BALB/c mice with subcutaneous CT26 colon cancer animal model were randomly equally divided into four groups,including the control group (groupⅠ,saline 0.1 mL/(10. d), O. diffusa ethanol extract of 90 mg/(kg.d) (groupⅡ), O. diffusa ethanol extract of 180 mg/(kg.d) (groupⅢ) and O. diffusa ethanol extract of 360 mg/(kg.d) (group Ⅳ) . Each group of mice were treated with intragastric administration of law administration 12 days after vaccination, then stopped and continue fed to 32 days, and the mice were killed. Micro-vascular dense ( MVD) was observed and countered under the microscopy by immunohistory chemistry. Results The murine colon tumor volumes of GroupⅡ,ⅢandⅣwere significantly less than that of groupⅠ,with significant difference ( <0.05) . The tumor microvessel density values of four groups was (7.83±2.87), (5.32±1.27), (1.77±0.70) and (1.87±0.68),respectively. The number of tumor blood vessels in GroupⅡ,Ⅲ and Ⅳ were significantly less than that of Ⅰ group, with significant difference ( <0.05) . Conclusion Within a certain dose range, the ethanol extract of O. diffusa can significantly inhibit the mouse colon cancer and the mechanism may be realated to inhibiting tumor angiogenesis.

Decrease in intestinal endocrine cells in Balb/c mice with CT-26 carcinoma cells

The density of intestinal endocrine cells, in Balb/c mice with colon 26 (CT-26) carcinoma cells, were examined immunohistochemically at 28 days after implantation. After CT-26 cell administration there was a significant decrease in most of the intestinal endocrine cells (p < 0.01) compared with the control group. The significant quantitative changes in the intestinal endocrine cell density might contribute to the development of the gastrointestinal symptoms commonly encountered in cancer patients.

The Effects of the Tumor Mass Size Inoculated in Immunologically Competent Balb/c Mice on Delayed-type Hypersensitivity Response

BACKGROUND: Based on outstanding progresses in animal experiments, vaccines for some human tumors have been developed. However, clinical effects of these vaccines have been far below than expected. This discrepancy might come from differences between animal models and human patients with respect to immunocompetency. The immune status of mice after tumor inoculation has not been well studied, which make us cautious in interpreting and applying the results from mice to human. We evaluated cell-mediated immune responses in mice after tumor cell inoculation. METHODS: Mice were inoculated with TA3Ha, CT26, or 4T1. Delayed-type hypersensitivity (DTH) responses were induced 2-4 weeks after inoculation using 2,4-dinitro-1-fluorobenzene as an antigen. The relationships between the severity of DTH responses and the duration of tumor inoculation or the size of tumor mass were analyzed. RESULTS: In TA3Ha groups, DTH response was elevated 2 weeks after inoculation, but depressed after 4 weeks, compared to the control group. When analyzed based on the sizes of tumor masses elicited, DTH responses were inversely related to the mass size, especially in those greater than 10 mm in diameter. In CT26 groups, while the duration after inoculation did not affect the severity of DTH responses, those with large mass showed depressed responses regardless the duration of inoculation. 4T1 cells grew so slowly that the size of tumor mass was small even 4 weeks after inoculation, and this group showed much higher DTH responses compared to that of tumor-free group. CONCLUSION: At least in an experimental setting where tumor model was induced by inoculating tumor cell lines into immunologically competent mice, the host immune response was elevated in early stage, and then depressed in late stage when the mass grew over a critical size.

Application of Apoptogenic Pretreatment to Enhance Anti-tumor Immunity of Granulocyte-Macrophage Colony Stimulating Factor (GM-CSF)-secreting CT26 Tumor Cells

BACKGROUND: As an attempt to develop a strategy to improve the protective immune response to GM-CSF-secreting CT26 (GM-CSF/CT26) tumor vaccine, we have investigated whether the apoptogenic treatment of GM-CSF/CT26 prior to vaccination enhances the induction of anti-tumor immune response in mouse model. METHODS: A carcinogen- induced mouse colorectal tumor, CT26 was transfected with GM-CSF gene using a retroviral vector to generate GM-CSF-secreting CT26 (CT26/GM-CSF). The CT26/GM-CSF was treated with gamma-irradiation or mitomycin C to induce apoptosis and vaccinated into BALB/c mice. After 7 days, the mice were injected with a lethal dose of challenge live CT26 cells to examine the protective effect of tumor vaccination in vivo. RESULTS: Although both apoptotic and necrotic CT26/GM-CSF vaccines were able to enhance anti-tumor immune response, apoptotic CT26/GM-CSF induced by pretreatment with gamma-irradiation (50,000 rads) was the most potent in generating the anti-tumor immunity, and thus 100% of mice vaccinated with the apoptotic cells remained tumor free for more than 60 days after tumor challenge. CONCLUSION: Apoptogenic pretreatment of GM-CSF-secreting CT26 tumor vaccine by gamma-irradiation (50,000 rads) resulted in a significant enhancement in inducing the protective anti-tumor immunity. A rapid induction of apoptosis of CT26/GM-CSF tumor vaccine at the vaccine site might be critical for the enhancement in anti-tumor immune response to tumor vaccine.

Retention Characteristics of Tc-99m-Pullulan-Derivatives in CT26 Tumor of Mice / 대한핵의학회잡지

OBJECTIVE: Pullulan derivatives (PD) can be used to make self-assembled hydrogel nanoparticles which are responsive to ionic strength. The aim of this study is to evaluate the potential of PD as a retaining carrier of radioisotope inside tumors. MATERIALS AND METHODS: Four types of PD were evaluated which included pullulan acetate (PA), succinylated PA (SPA), PA-DTPA and SPA-DTPA conjugates. They were radiolabeled with Tc-99m. Labelling efficiencies were determined at 30 min, 1, 2, 4 and 12 hours after radiolabeling. CT-26 colon cancer cells were subcutaneously injected into Balb/c mice. After 2 weeks of subcutaneous injection, Tc-99m-labelled PD (Tc-99m-PD) were injected into the tumors. Whole body images of mice were obtained at 30 min, 1, 2, and 12 hr after intratumoral injection. All twenty mice were grouped into four groups by largest diameter; control A (largest diameter = 5 mm, n = 5), control B (largest diameter = 10 mm, n = 5), pullulan A (largest diameter = 5 mm, n = 5), pllulan B (largest diameter = 10 mm, n = 5). Dynamic images were obtained for 1 hour after intratumoral injection. Static images were obtained at 1 hr, 2 hr, 3 hr and 4 hr after intratumoral injection with Tc-99m pertechnetate and Tc-99m-PA. Target-to-background ratios and retention rates were calculated. RESULTS: Labeling efficiencies of PA, SPA, PA-DTPA and SPA-DTPA were 94.5 +/- 5.9%, 97.8 +/- 3.5% 94.2 +/- 3.8%, and 92.5 +/- 6.2%, respectively (p> 0.05). Percent retention rates (%RR) of PA and PA-DTPA were significantly higher than those of control, however, those of SP-DTPA and SPA became similar to control at 4 and 12 hr, respectively. %RR of pullulan A and pullulan B at 1, 4 and 8 hr is significantly higher than that of control (p < 0.05). However, %RR between pullulan A and pullulan B were similar. CONCLUSION: The ionic strength dependent PD-nanoparticles are retained in the tumor. No difference of %RR according to tumor size was noted. Therapeutic application of PD labelled with beta- or alpha- emitting radionuclides can be expected.

The Apoptosis Induction of CT 26 Cells by Recombinant Clostridium difficile Toxin B / 微生物学通报

To investigate the induction of apoptosis of mouse colonic adenocarcinoma CT26 cells by recombinant Clostridium difficile toxin B (rTcdB), CT26 cells were exposed to different concentrations of rTcd B. Inhibition of cell proliferation was measured by MTT assay. The activation of Caspase 3 was measured by colorimetric method. Cell morphological analysis and flow cytometry were performed to confirm cell apoptosis. rTcd B inhibited the proliferation of CT26 cells in a timeand dose-dependent manner. Caspase 3 activity in CT26 cells was elevated remarkably after rTcd B exposure for 6 h, 12 h, 18 h or 24 h, as compared with the control group. Morphological changes were observed by fluorescence microscopy. The exposure of rTcd B to CT26 cells induced a timeand dose-dependent apoptotic cell death as determined by flow cytometry analysis. The results showed that recombinant Clostridium difficile toxin B induced apoptosis of CT26 cells.