A diffusive predator-prey system with prey refuge and predator cannibalism.

This paper is devoted to exploring a diffusive predator-prey system with prey refuge and predator cannibalism. We investigate dynamics of this system, including dissipation and persistence, local and global stability of constant steady states, Turing instability, and nonexistence and existence of nonconstant steady state solutions. The influence of prey refuge and predator cannibalism on predator and prey biomass density is also considered by using a systematic sensitivity analysis. Our studies suggest that appropriate predator cannibalism has a positive effect on predator biomass density, and then high predator cannibalism may stabilize the predator-prey ecosystem and prevent the paradox of enrichment.

Comparison of 5-FU-based and Capecitabine-based Neoadjuvant Chemoradiotherapy in Patients With Rectal Cancer: A Meta-analysis.

INTRODUCTION: The inconvenience of using infusion therapies resulted in the development of capecitabine (CA), an oral fluoropyrimidine. In this meta-analysis, we evaluated 10 studies that compared the efficacy and safety of an oral CA-based regimen with those of a continuous infusion 5-fluorouracil (5-FU) regimen for neoadjuvant chemoradiotherapy in patients with rectal cancer. MATERIALS AND METHODS: The databases searched included Medline, Cochrane, EMBASE, and Google Scholar (until August 31, 2016). The primary outcome assessed was the rate of postoperative down-staging of the tumor and pathologic complete response. The secondary outcomes were disease-free survival (DFS) and overall survival (OS). RESULTS: This meta-analysis (5 retrospective studies, 3 prospective studies, and 2 randomized controlled trials [RCTs]) compared the efficacy of the 5-FU arm (n = 757) to that of the CA arm (n = 719). There was no significant difference in tumor down-staging rate between the 2 regimens (RCTs/prospective studies: odds ratio [OR], 0.88; 95% confidence interval [CI], 0.65-1.20; P = .416; retrospective studies: OR, 0.84; 95% CI, 0.50-1.44; P = .534). There was also no significant difference in pathologic complete response (RCTs/prospective studies: OR, 0.80; 95% CI, 0.52-1.23; P = .304; retrospective studies: OR, 0.73; 95% CI, 0.48-1.12; P = .149), or survival rates (3-year, 5-year DFS, and 5-year OS rate) between the 2 groups. The CA group had a higher number of patients reporting diarrhea and hand-foot syndrome compared with the 5-FU group. The 5-FU group had a higher number of patients reporting mucositis compared with the CA group. CONCLUSIONS: Our data suggested that oral CA was equivalent to continuous infusion 5-FU in the curative setting of rectal cancer during neoadjuvant chemoradiotherapy.

[Effect and mechanism of gastrodin inhibiting ß-amyloid plaques in brain of mice].

This study was designed to investigate the effect of gastrodin（GAS） against ß-amyloid plaques in 5×FAD Alzheimer's disease（AD） transgenic mice, and utilize 117 cell model（over-expression of Aß and ß-secretase） to explore the underlying mechanism. 5×FAD mice model were randomly divided into three groups, including GAS-high dose group(GAS-H, 200 mg·kg(-1)·d(-1)), GAS-middle dose group(GAS-M, 100 mg·kg(-1)·d(-1)) and GAS-low dose group(GAS-L, 50 mg·kg(-1)·d(-1)). Meanwhile, the wild type mice were used in the control group. After being treated with GAS for three months, 5×FAD mice were evaluated by Morris water maze for the learning and memory ability and by ELISA for Aß in the cerebral homogenate. Then, Aß plaques in the hippocampus and cortex of 5×FAD mice were observed and analyzed with immunohistochemical staining. The cell apoptosis rate and the cell viability were determined in vitro, after the cells were treated with different concentrations of GAS(10, 25, 50 and 100 µmol·L(-1)). Furthermore, Intracelluar/extracelluar Aß were determined by ELISA. Effects of GAS on BACE（ß-secretase site APP cleaving enzyme） m RNA and protein expression were analyzed in 117 cell models by Q-PCR and Western blotting. The results suggest that GAS is able to restore the learning and memory capacity of 5×FAD mice, and reduce Aß in the cerebral homogenate and Aß plaques in the brain. Compared with the untreated transgenic positive group, Aß plaques were declined in hippocampus and cortex of GAS-H group by 93.28% and 88.88%, and Aß was reduced in the cerebral homogenate by 55.74%. In vitro study suggests a dose-dependent effect of GAS in reducing Aß in 117 cell models. When the cells were treated with 100 µmol·L(-1) GAS, extracelluar Aß and intracellular Aß of 117 cells were reduced by 63.1% and 49.1%. BACE expression was largely suppressed in m RNA by 32.9%（P < 0.01）. At 50 µmol·L(-1) GAS, the protein level was declined by 47.9%（P < 0.05）. In conclusion, GAS inhibits Aß production and accumulation by inhibiting ß-secretase.

[Screening of 10 types of Chinese herbal compounds inhibiting Abeta and their possible related mechanism in vitro].

This study is to screen the Chinese herbal compounds which could inhibit the production of Abeta and investigate the underlying mechanism. Ten types of compounds which have potential value in the treatment of AD were selected as initial screening trial. The cell models which used could overexpress Abeta and beta-secretases or Abeta and gamma-secretases. Extracellular Abeta was determined by ELISA after the cell models treated with different concentrations of compounds (0.5-100 micromol x L(-1)), separately. Then the compounds were selected which could inhibit extracellular Abeta and their best concentration ranges were decided, too. Furthermore, the cell viability and apoptosis rate, the level of intracellular Abeta, beta and gamma-secretases were determined after the cell models treated with different concentrations of selected compounds. The results showed that 4 of the 10 compounds could reduce the level of extracellular Abeta; they were cryptotanshinone, astragalosides, gastrodin and paeoniflorin, and their best concentration ranges were 0.5-5.0, 0.5-5.0, 5.0-50, 1.0-25 micromol x L(-1), respectively. Further study indicated that the 4 selected compounds were nontoxic to the cellular models and lowering intracellular Abeta were more effective compared with extracellular; of which astragalosides and gastrodin showed dose-dependent inhibition to the activities of beta and gamma-secretases, with the maximum inhibiting rates of 78.2% and 80.3%, respectively. In conclusion, cryptotanshinone, astragalosides, gastrodin and paeoniflorin could inhibit the expression and secretion of Abeta, and the underlying inhibiting mechanism of astragalosides and gastrodin were related with the reduction of the beta and gamma-secretase activities, respectively.

[Enhanced anticancer effects of 5'-DFUR on colorectal cancer cell lines SW480 and LOVO by transfection with thymidine phosphorylase cDNA].

OBJECTIVES: To study the change of ability to transform from 5'-deoxy-fluorouracil monophosphate (5'-DFUR) to fluorouracil (5-FU) in human colon cancer cell lines SW480 and LOVO which transfected with thymidine phosphorylase (TP) gene. And to discuss the anti-cancer activity of 5'-DFUR to SW480 and LOVO cells. METHODS: TP cDNA were transfected into human colorectal cancer cell lines SW480 and LOVO with the lentiviral vector, pLenti6.3_MCS_IRES2-EGFP. The transfection efficiency was analyzed by flow cytometer, the mRNA expression of TP was detected by RT-PCR, and the TP protein expression was detected by Western blot, and the volumes of 5-FU converted from 5'-DFUR both in 2 cells and medium were detected by high performance liquid chromatography (HPLC). The 50% inhibitory concentration (IC50) of 5'-DFUR on these 2 colon cancer cell lines both wild type and TP-transfected cells were evaluated by MTT assay. RESULTS: The colorectal cancer cell lines SW480 and LOVO transfected with human TP cDNA were monitored 5 generations, and the transfections efficiency rate wea about 95%. Compared with wild type cell SW480 and LOVO, the RQ values of mRNA expression of SW480-TP and LOVO-TP were (695 ± 171) folds (t = -7.00, P = 0.002) and (282 ± 87) folds (t = -5.61, P = 0.030), respectively. Also TP protein expression in SW480-TP and LOVO-TP were higher than their parent cells shown by Western blot. The volume of 5-FU converted from 5'-DFUR in the medium cultured SW480-TP and LOVO-TP were increased compared with their parent cells, respectively (t = 19.406-66.921, P < 0.01), whereas few of 5-FU was detected both in wild, and TP-transfected cells. After transfected with TP cDNA, the IC50 of 5'-DFUR on SW480-TP and LOVO-TP were (587 ± 17) µmol/L and (1088 ± 89) µmol/L respectively, and there were significantly less than their parent cells (t = -32.59 and -8.52, P < 0.01). CONCLUSIONS: The stabilized transfections of SW480 and LOVO with higher TP expression could be built with lentiviral vector. Transfected TP cDNA into SW480 and LOVO, could improve the expression both of TP mRNA and TP protein, increase the volume of 5-FU converted from 5'-DFUR in medium, and result in an enhancement of anticancer effect on these 2 cells.

Research development of the relationship between thymidine phosphorylase expression and colorectal carcinoma.

Thymidine phosphorylase (TP) is a key enzyme that contributes to the composition and decomposition of pyrimidine nucleotides. TP seems homologous to platelet-derived endothelial cell growth factor, and its effects on inducing vascularization and anti-apoptosis are closely related to growth and metastasis of colorectal carcinoma. In addition, TP is a key enzyme that catalyzes the transformation from 5-fluorouracil (FU) prodrugs of 5'-deoxy-5-fluorouridine (5'-DFUR) to 5-FU. The activity of TP is closely related to the sensitivity of colorectal carcinoma cells to fluorouracil drugs and targeted therapy. Given the important functions of TP in growth, metastasis, tumor treatment, and prognosis, determining its expression mechanism is significant. This article summarizes the research development of TP expression in colorectal carcinoma, tumor neovascularization, cytotoxicity activation of 5'-DFUR, and colorectal carcinoma therapy.

[Effect of thymidine phosphorylase cDNA transfection on the inhibition of human colon carcinoma cell line by 5'-deoxy-5-fluorouridine].

OBJECTIVE: To investigate the inhibiting impact of 5'-deoxy-5-fluorouridine (5'-DFUR) on human colon carcinoma cell line LOVO after transfection of thymidine phosphorylase (TP) cDNA. METHODS: TP cDNA was transfected into human colon carcinoma cell line LOVO with lentiviral vector pLenti6.3_MCS_IRES2-EGFP, and the transfection efficiency was analyzed by flow cytometry. TP mRNA and protein expressions were detected by RT-PCR and Western blotting respectively. The IC50 of 5'-DFUR on TP-transfected LOVO and parental cell were evaluated by MTT assay. The volumes of 5-FU converted from 5'-DFUR in media, where TP-transfected and parental LOVO were cultured, were detected by HPLC. RESULTS: The stable transfectants passed 5 generations were obtained and the transfection rate was 95%. Compared with parental cell, the RQ values of mRNA expression in TP-transfected LOVO was (282.5±86.8) folds higher significantly (P<0.01), also the TP protein expression of TP-transfected LOVO was obviously up-regulated as compared to parental cells. The IC50 value of 5'-DFUR of TP-transfectants was (1087.7±89.1) µmol/L, less than (1607.3±56.8) µmol/L of parental cells significantly (P<0.01), while there was no significant difference between parental cells and vector-transfectants [(1699.5±38.7) µmol/L, P>0.05]. HPLC revealed that when medium was added with 0, 500, 1000, and 2000 µmol/L of 5'-DFUR respectively, 0, 2.10, 3.13, and 7.19 µmol/L of 5-FU was found in the parental cells culture, while 0, 22.16, 30.94 and 40.02 µmol/L of 5-FU was found in TP-transfectants culture, but no 5-FU was found in the vector-transfectants culture. CONCLUSION: TP cDNA transfection into LOVO can up-regulate the TP mRNA and protein expressions, increase the 5-FU converted from 5'-DFUR, and enhance the cytotoxic effect of 5'-DFUR on the LOVO cells.

[Influence of interferon-α2a on thymidine phosphorylase expression and anticancer activity of 5'-deoxy-fluorouridine in human colon carcinoma cell lines LOVO and SW480].

OBJECTIVE: To detect the effect of interferon-α2a(IFN-α2a) on thymidine phosphorylase(TP) mRNA expression levels and the anticancer activity of 5-fluorouracil(5-FU) and 5'-deoxy-fluorouridine(5'-DFUR) in human colon carcinoma cell lines LOVO and SW480. METHODS: Two human colon cancer cell lines LOVO and SW480 were cultured and treated with IFN-α2a at a series of dosage, and fluorescence quantitative PCR was carried out to detect the TP mRNA expression levels in these 2 cell lines. Then MTT assay and software Templet were used to determine the change of 50% inhibition concentration of 5-FU or 5'-DFUR combined with IFN-α2a on the two cell lines. RESULTS: The TP mRNA expressions were up-regulated significantly by IFN-α2a at the doses of 500 U/ml and 5000 U/ml in LOVO(P<0.01). Compared with untreated cells(IFN-α2a 0 U/ml), no significance was found for TP mRNA expression levels in LOVO and SW480 treated by IFN-α2a at the dose of 50 U/ml (P>0.05). There was no significant difference for TP mRNA expression in SW480 between the dose of 0 U/ml and 500 U/ml of IFN-α2a(P>0.05), while a significant increace was detected at the dose of 5000 U/ml (P<0.01). No significant difference was found for the IC50 values after treatment of 5-FU combined with IFN-α2a (20 U/ml) on LOVO and SW480 compared with 5-FU alone, while the IC50 values after treatment of 5'-DFUR combined with IFN-α2a decreased significantly compared with 5'-DFUR alone(P<0.05). CONCLUSION: There is no direct inhibition effect of IFN-α2a on LOVO and SW480 in vitro, while it can up-regulate TP mRNA expression levels both in LOVO and SW480, and enhance the anticancer effect of 5'-DFUR on these 2 cell lines.

[Expression and clinical significance of fibroblast activation protein in colorectal carcinoma tissue].

OBJECTIVE: To detect the expression of fibroblast activation protein(FAP) in colorectal cancer tissue, and to investigate the association between expression of FAP with pathological parameters. METHODS: Fifty-five cancer tissues and 50 normal colorectal samples were examined using immunohistochemistry with anti-FAP polyclonal antibody. The distribution of positive cells in different tissues, and associations of positive cell number with tumor staging, lymph node metastasis and tumor invasion were investigated to evaluate the effects of FAP on pathological progress in colorectal cancer. RESULTS: No FAP expression was observed in 50 normal colorectal tissue samples. FAP positive cells were seen in carcinoma associated fibroblasts(CAFs), and in few colorectal cancer cells. The numbers of FAP positive cells in tissue samples of TNM III(-IIII((40.1±15.9) was significantly greater than that of TNMI(-II( (18.3±7.7)(P<0.01). Furthermore, the number of FAP positive cells in tissue samples with lymph node metastasis (44.4±13.3) was also significantly higher than those without lymph node metastasis (18.5±8.1)(P<0.01). Significant positive correlations were found between the number of FAP-positive cells with the tumor TNM staging and lymph node metastasis(r=0.544 and r=0.793, respectively)(P<0.01). The number of FAP-positive cells was 25.2±8.9 in T2, 32.41±19.30 in T3, and 29.2±16.5 in T4. The association between number of positive cells and depth of invasion was not statistically significant(P>0.05). CONCLUSIONS: The FAP mainly expresses in CAFs locating in colorectal cancer tissues. The number of FAP positive cells is positively correlated with TNM staging of colorectal cancer and lymph node metastasis.

[Study on expression of PS1 in APP-PS1 double gene stably transfected cell lines and its relation to gamma-secretase].

OBJECTIVE: To study the role of presenilin1 (PS1) in the processing of beta-amyloid precursor protein (APP) to amyloid beta-peptide (Abeta) and its relation to gamma-secretase in the pathogenesis of Alzheimer's disease (AD). METHODS: Several CHO cell lines stably transfected with either wide-type or mutant PS1 (M(146)L) along with APP(751) genes were established. The expression of PS1 and its half-life were determined by immunoprecipitation, Western blotting and pulse-chase experiment. Abeta released into the conditional media was quantitated by ELISA. RESULTS: PS1 transfected CHO cells expressed an expected 45,000 full length protein. This over-expressed full length PS1 was subject to fast degradation with a half-life of less than 1 hour. In contrast to full length PS1, the truncated N-terminal and C-terminal proteins of PS1 were significantly more stable with a longer half-life of nearly 16 hours. Although the total amount of Abeta released into the conditional media did not show a significant difference between wild-type and mutant PS1 (M(146)L) transfected APP cells, mutant PS1 (M(146)L) transfected APP cells increase Abeta(1 - 42) (a subspecies of total Abeta) production with nearly a 2 fold increase, comparing to untransfected or wild-type PS1 transfected APP cells. CONCLUSION: PS1 is involved in the processing of APP to Abeta, a nearly 2 fold increase of Abeta production in mutant PS1 (M(146)L) transfected APP cells indicates that PS1 may be the expected gamma-secretase itself.

[Thymidine phosphorylase expressed in monocyte-macrophages enhanced anticancer effect of 5'-deoxy-5-fluorouridine on colorectal carcinoma cells].

OBJECTIVE: To detect the thymidine phosphorylase (dThdPase) expression in colorectal carcinoma tissue, and clarify whether dThdPase expressed in macrophage-like cell lines, and monocytes from human peripheral blood can modulate the anticancer effect of 5'-deoxy-5-fluorouridine (5'-DFUR) on colorectal carcinoma cells. METHODS: Forty specimens resected from 40 patients with colorectal carcinoma were immunohistochemically stained by the monoclonal antibodies 654-1 (anti-dThdPase) and PG-M1 (anti-macrophage marker CD68). Then morphometrical analysis and positive cell counting were performed. In 27 of 40 specimens, dThdPase activity analysis was assayed by HPLC. The dThdPase level were also measured by ELISA in 4 colorectal cancer cell lines, LS174T, Clone A, Colo320, MIP101, and 2 macrophage-like cell lines, THP-1, U937. After estimated the drug sensitivities of each colorectal carcinoma cell both to 5'-DFUR and 5-Fu by MTT assay, THP-1, U937, or monocytes isolated from human blood were incubated in the medium containing 5-Fu or 5'-DFUR for 24 hours, respectively. Then the supernatant was collected and 2-fold serially diluted with the medium, in which the macrophage-like cells, or monocytes were also cultivated for 24 h without anticancer agents. Using the serially diluted medium, MTT assay were also carried out on 4 colorectal carcinoma cell lines. Each experiment was repeated six times and the means of IC50 value +/- standard errors (mean +/- S.E.M.) were calculated. Finally, THP-1 or U937 cells were cultured in medium containing 400 micro mol/L of 5'-DFUR for 24 hours, then the supernatants were collected and the amount of generated 5-Fu was measured by HPLC. RESULTS: dThdPase activities was significantly increased (139.7 micro g x 5-Fu x h(-1) x ml(-1) +/- 61.5 micro g x 5-Fu x h(-1) x ml(-1)) in colorectal carcinoma tissues compared with adjacent normal tissues (42.2 micro g x 5-Fu x h(-1) x ml(-1) +/- 21.4 micro g x 5-Fu x h(-1) x ml(-1)), P < 0.001. In immunohistochemical analysis, it was confirmed that most cells expressed dThdPase-positive cells were the stromal cells, especially macrophages, which surrounding cancer nests, or along the invasive margin of cancer. The distribution patterns of dThdPase-positive stromal cells are similar to that of the CD68-positive cells. The number of dThdPase positive cells was correlated with the number of macrophages in the cancerous tissues, r = 0.76. The dThdPase protein were detected at the levels of 18.2 unit/mg in THP-1, 19.3 unit/mg in U937, and 0.5 unit/mg in LS174T, however, not detected in other 3 colorectal carcinoma cells. The values of IC50 of 5'-DFUR on the 4 colorectal carcinoma cell lines were 11.5 approximately 84.8 times higher than those of 5-Fu (all P < 0.01). It was showed that no inhibiting effect for 5'-DFUR on the growth rates of THP-1, U937, and monocyte cells. After incubated with THP-1 or U937, 5'-DFUR expressed a significant enhanced antitumor effect (P < 0.0001), while almost no change is observed to 5-Fu (P > 0.05). Same conclusion was also demonstrated in using the monocytes instead of THP-1 or U937. 40.2 micro mol/L and 29.5 micro mol/L of 5-Fu were detected in the medium containing 400 micro mol/L of 5'-DFUR treated with THP-1 and U937 cells, respectively. CONCLUSION: 5'-DFUR cannot be converted into 5-Fu in colorectal carcinoma cells in vitro because no dThdPase is expressed in those cells. After being incubated with macrophage-like cell, THP-1, U937, or human monocytes, the anticancer effect of 5'-DFUR is significantly increased due to the activation by dThdPase expressed in above cells.

Expression of thymidine phosphorylase by macrophages in colorectal cancer tissues.

AIM: To detect the thymidine phosphorylase (dThdPase) expression in human colorectal cancer tissues and cells. METHODS: Forty specimens resected from patients with colorectal cancer were immunohistochemically stained by 654-1, anti-dThdPase monoclonal antibody, PG-M1, anti-macrophage marker CD68 monoclonal antibody. Morphometrical analysis and positive cell counting were performed. In 27 of 40 specimens, dThdPase activity was also assayed by HPLC. Otherwise, the dThdPase level was measured by ELISA in 6 colorectal cancer cell lines, LS174T, Clone A, Colo320, CX-1, Lovo, and MIP101, as well as in 2 macrophage-like cell lines, THP-1 and U937. RESULTS: dThdPase activity was significantly increased in cancer tissues compared with adjacent normal tissue (P<0.01). In immunohistochemical analysis, it was confirmed that most cells expressed dThdPase were the stromal cells surrounding cancer nests or along the invasive margin of cancer. Based on their morphometrical characteristics, we found that most of them were tumor-associated macrophages (TAMs). The number of dThdPase-positive stromal cells was significantly correlated with the number of CD68-positive macrophages (r=0.76, P<0.0001). By ELISA, 18.2 unit/mg and 19.3 unit/mg of dThdPase protein were detected in THP-1 and U937, but only little was detected in 6 colorectal cancer cell lines. CONCLUSION: The present data suggest that dThdPase expression is seldom detected in colorectal carcinoma cells. TAM is the most important source of dThdPase in colorectal cancer tissues.