Random walks in a random environment on a strip: a renormalization group approach

We present a real space renormalization group scheme for the problem of random walks in a random environment on a strip, which includes one-dimensional random walk in random environment with bounded non-nearest-neighbor jumps. We show that the model renormalizes to an effective one-dimensional random walk problem with nearest-neighbor jumps and conclude that Sinai scaling is valid in the recurrent case, while in the sub-linear transient phase, the displacement grows as a power of the time.Comment: 9 page

Sensitive PCR method for the detection and real-time quantification of human cells in xenotransplantation systems

The sensitive detection of human cells in immunodeficient rodents is a prerequisite for the monitoring of micrometastasis of solid tumours, dissemination of leukaemic cells, or engraftment of haematological cells. We developed a universally applicable polymerase chain reaction method for the detection of a human-specific 850-bp fragment of the α-satellite DNA on human chromosome 17. The method allows the detection of one human cell in 106 murine cells and could be established as both, a conventional DNA polymerase chain reaction-assay for routine screening, and a quantitative real-time polymerase chain reaction-assay using TaqMan-methodology. It was applied to the following xenotransplantation systems in SCID and NOD/SCID mice: (1) In a limiting dilution assay, cells of the MDA-MB 435 breast carcinoma were injected into the mammary fat pad of NOD/SCID mice. It could be shown that 10 cells mouse−1 were sufficient to induce a positive polymerase chain reaction signal in liver and lung tissue 30 days after transplantation as an indicator for micrometastasis. At this time a palpable tumour was not yet detectable in the mammary fat pad region. (2) Cells of a newly established human acute lymphatic leukaemia were administered intraperitoneally to SCID mice. These cells apparently disseminated and were detectable as early as day 50 in the peripheral blood of living mice, while the leukaemia manifestation was delayed by day 140. (3) In a transplantation experiment using mature human lymphocytes we wanted to standardise conditions for a successful survival of these cells in NOD/SCID mice. It was established that at least 5×107 cells given intravenously were necessary and that the mice had to be conditioned by 2 Gy body irradiation to get positive polymerase chain reaction bands in several organs. (4) Engraftment studies with blood stem cells originating from cytapheresis samples of tumour patients or from cord blood were undertaken in NOD/SCID mice in order to define conditions of successful engraftment and to use this model for further optimisation strategies. The polymerase chain reaction method presented allowed a reliable prediction of positive engraftment and agreed well with the results of immunohistochemical or FACS analysis. All together, the polymerase chain reaction method developed allows a sensitive and reliable detection of low numbers of human cells in immunodeficient hosts. In combination with real-time (TaqMan) technique it allows an exact quantification of human cells. As this method can be performed with accessible material of living animals, follow up studies for the monitoring of therapeutic interventions are possible in which the survival time of mice as evaluation criteria can be omitted

Uptake, biodistribution, and time course of naked plasmid DNA trafficking after intratumoral in vivo jet injection

Nonviral jet injection is an applicable technology for in vivo gene transfer of naked DNA. However, little is known about the biodistribution and clearance of jet-injected DNA, or about its localization within tissue and cells. Therefore, in this study we analyzed the intratumoral and systemic biodistribution of jet-injected naked DNA in human colon carcinoma-bearing NCr-nu/nu mice, which were jet-injected with the pCMVbeta plasmid DNA. Intratumoral and systemic plasmid DNA biodistribution was analyzed 5, 10, 20, and 40 min and 3, 6, 24, 48, and 72 hr after jet injection, using quantitative real-time polymerase chain reaction. In the tumors, a rapid drop in naked DNA load within 24 hr of jet injection was shown. Detailed analysis of intratumoral distribution of rhodamine-labeled DNA revealed the presence of plasmid DNA within tumor cells 5 min after jet injection and further accumulation of significant DNA amounts in the cell nuclei 30 to 60 min after jet injection. In the blood, DNA amounts rapidly dropped within 10 to 40 min of jet injection to less than 0.001 pg of plasmid per 250 ng of tissue DNA and only minimal plasmid DNA dissemination was detected in liver, lung, spleen, kidney, and ovaries, which was cleared 3 to 6 hr after jet injection. By contrast, in heart, bone marrow, and brain almost no plasmid DNA was detectable

Cell death sensitization of leukemia cells by opioid receptor activation

Cyclic AMP (cAMP) regulates a number of cellular processes and modulates cell death induction. cAMP levels are altered upon stimulation of specific G-protein-coupled receptors inhibiting or activating adenylyl cyclases. Opioid receptor stimulation can activate inhibitory Gi-proteins which in turn block adenylyl cyclase activity reducing cAMP. Opioids such as D,L-methadone induce cell death in leukemia cells. However, the mechanism how opioids trigger apoptosis and activate caspases in leukemia cells is not understood. In this study, we demonstrate that downregulation of cAMP induced by opioid receptor activation using the opioid D,L-methadone kills and sensitizes leukemia cells for doxorubicin treatment. Enhancing cAMP levels by blocking opioid-receptor signaling strongly reduced D,L-methadone-induced apoptosis, caspase activation and doxorubicin-sensitivity. Induction of cell death in leukemia cells by activation of opioid receptors using the opioid D,L-methadone depends on critical levels of opioid receptor expression on the cell surface. Doxorubicin increased opioid receptor expression in leukemia cells. In addition, the opioid D,L-methadone increased doxorubicin uptake and decreased doxorubicin efflux in leukemia cells, suggesting that the opioid D,L-methadone as well as doxorubicin mutually increase their cytotoxic potential. Furthermore, we found that opioid receptor activation using D,L-methadone alone or in addition to doxorubicin inhibits tumor growth significantly in vivo. These results demonstrate that opioid receptor activation via triggering the downregulation of cAMP induces apoptosis, activates caspases and sensitizes leukemia cells for doxorubicin treatment. Hence, opioid receptor activation seems to be a promising strategy to improve anticancer therapies

Efficacy of MS-275, a selective inhibitor of class I histone deacetylases, in human colon cancer models

N-(2-aminophenyl)-4-[N-(pyridine-3yl-methoxy-carbonyl) aminomethyl] benzamide (MS-275) is a second generation histone deacetylase (HDAC) inhibitor with significant anti-tumor efficacy currently in clinical development. We investigated the effect of MS-275 treatment on various colon cancer cell lines, as well as on mouse xenograft models derived from human colorectal cancer. MS-275 exerted strong anti-proliferative effects in five cell lines and increased the acetylation of histones 3 and 4. In vivo testing of the compound in eight different models of human colon cancer derived from primary colorectal cancers or from established cell lines revealed that five models were responders, two non-responders and one an anti-responder. Gene expression profiles were determined in order to identify genes and pathways differentially regulated upon MS-275 treatment in responder versus non-responder models. Principle component analysis revealed a correlation of the anti-tumor efficacy with the sub-clustering of the MS-275 treatment groups in 7 out of 8 models. Although the overall gene expression pattern was rather unique for each individual model, 129 genes were significantly up- and 58 genes significantly down-regulated in at least 2 out of 5 responder models in response to MS-275 treatment. We identified potential biomarkers for response to MS-275, such as PRA1, MYADM and PALM2-AKAP2 which were up-regulated in all responder models and down-regulated or unchanged in all non-responder models. Our results provide a starting point for the development of clinically relevant biomarkers for predicting a response to MS-275 and the understanding of the mode of action of this HDAC inhibitor

Opioid receptor activation triggering downregulation of cAMP improves effectiveness of anti-cancer drugs in treatment of glioblastoma

Glioblastoma are the most frequent and malignant human brain tumors, having a very poor prognosis. The enhanced radio- and chemoresistance of glioblastoma and the glioblastoma stem cells might be the main reason why conventional therapies fail. The second messenger cyclic AMP (cAMP) controls cell proliferation, differentiation, and apoptosis. Downregulation of cAMP sensitizes tumor cells for anti-cancer treatment. Opioid receptor agonists triggering opioid receptors can activate inhibitory Gi proteins, which, in turn, block adenylyl cyclase activity reducing cAMP. In this study, we show that downregulation of cAMP by opioid receptor activation improves the effectiveness of anti-cancer drugs in treatment of glioblastoma. The µ-opioid receptor agonist D,L-methadone sensitizes glioblastoma as well as the untreatable glioblastoma stem cells for doxorubicin-induced apoptosis and activation of apoptosis pathways by reversing deficient caspase activation and deficient downregulation of XIAP and Bcl-xL, playing critical roles in glioblastomas' resistance. Blocking opioid receptors using the opioid receptor antagonist naloxone or increasing intracellular cAMP by 3-isobutyl-1-methylxanthine (IBMX) strongly reduced opioid receptor agonist-induced sensitization for doxorubicin. In addition, the opioid receptor agonist D,L-methadone increased doxorubicin uptake and decreased doxorubicin efflux, whereas doxorubicin increased opioid receptor expression in glioblastomas. Furthermore, opioid receptor activation using D,L-methadone inhibited tumor growth significantly in vivo. Our findings suggest that opioid receptor activation triggering downregulation of cAMP is a promising strategy to inhibit tumor growth and to improve the effectiveness of anti-cancer drugs in treatment of glioblastoma and in killing glioblastoma stem cells

Cell cycle effects of fatty acid derivatives of cytarabine, CP-4055, and of gemcitabine, CP-4126, as basis for the interaction with oxaliplatin and docetaxel

To bypass resistance due to limited entry into the cell derivatives of cytarabine (CP-4055, elacytarabine) and gemcitabine (CP-4126) containing a fatty acid chain at the 5' position of the nucleoside were developed. CP-4055 showed an increased retention of the active metabolite, the triphosphate. This characteristic was supposed to favor combinations, such as with the tubulin antagonist docetaxel, the platinum oxaliplatin and the antifolate pemetrexed. The role of the cell cycle effects of CP-4055 and CP-4126 on the efficacy of the combination with docetaxel or pemetrexed was determined. The combination of CP-4055 with oxaliplatin and docetaxel was also evaluated in a mouse xenograft model. CP-4055 induced a G2/M and S phase accumulation and CP-4126 an S phase accumulation. Both analogs induced a dose-dependent cell kill (apoptosis and necrosis). None of the docetaxel combinations induced a synergistic effect. The combination of docetaxel with CP-4055 or CP-4126 induced a G2/M accumulation in the A549 (lung cancer) cell line, but a G0/G1 accumulation in the WiDR (colon cancer) cell line. Preincubation with docetaxel induced an increased cell kill in both cell lines. The combination with oxaliplatin showed a synergistic effect in both cell lines. Combinations with pemetrexed were antagonistic in both cell lines. In the A549 cell line pemetrexed with CP-4055 led to an increase of the G0/G1 phase and the S phase. In WiDR the combination of pemetrexed with CP-4055 increased the G0/G1 phase and increased the cell kill. Pemetrexed with CP-4126 induced an increase in the G0/G1 phase and the S phase in the A549 cell line. In the xenograft study, on a colon cancer and a lung metastasis model, the combination of CP-4055 with docetaxel showed the best results. Treatment with CP-4055 followed by docetaxel after 4 h resulted in a reduction in metastasis in a lung metastasis model, and a favorable toxicity profile was observed. In conclusion, the combinations with oxaliplatin showed a synergistic effect in the combination studies. Although the combinations with docetaxel did not show an enhanced effect in the in vitro studies, this combination revealed an increased effect in the xenograft model

Systemic shRNA mediated knock down of S100A4 in colorectal cancer xenografted mice reduces metastasis formation

The metastasis-inducing protein S100A4 was found to be a prognostic indicator for the development of metachronous metastases. S100A4 expression levels correlate with the formation of human colorectal cancer metastases and shorter patients' survival. Inhibition of S100A4 expression in patients might therefore result in decreased metastasis formation and prolonged survival. In the present study, we used shRNA expression plasmids to inhibit S100A4 expression in the colorectal cancer cell lines HCT116, SW620 and DLD-1. Cell lines with reduced S100A4 expression showed reduced cell migration and invasion in vitro. The knock-down of S100A4 expression also led to significantly diminished formation of liver metastases when intrasplenically transplanted in mice (P = 0.004). We then focused on the therapeutic potential of systemically applied shRNA expression plasmids acting on S100A4 via repeated hydrodynamics-based tail vein injection of plasmid DNA. Mice, intrasplenically transplanted with HCT116 cells and treated systemically with S100A4‑shRNA plasmids, showed a decrease of S100A4 and MMP9 expression levels, resulting in significantly reduced liver metastases (P = 0.005). In summary, we show for the first time the intratumoral knock down of S100A4 via systemic application of S100A4‑shRNA plasmid DNA, which restricts metastasis formation in a xenografted mouse model of colorectal cancer

Development and characterization of a tamoxifen-resistant breast carcinoma xenograft

A human tamoxifen-resistant mammary carcinoma, MaCa 3366/TAM, originating from a sensitive parental xenograft 3366 was successfully established by treatment of tumour-bearing nude mice with 1–50 mg kg−1tamoxifen for 3 years during routine passaging. Both tumours did not differ significantly in OR- and PR-positivity, however, when compared with the sensitive tumour line, the mean OR content of the TAM-resistant subline is slightly lower. An OR-upregulation following withdrawal of oestradiol treatment was observed in the parental tumours but not in the resistant xenografts. Following long-term treatment with tamoxifen, the histological pattern of the breast carcinoma changed. The more differentiated structures being apparent after treatment with 17β-oestradiol in the original 3366 tumour were not induced in the resistant line. Tamoxifen failed to induce a tumour growth inhibition in comparison to the tamoxifen-sensitive line. The pure anti-oestrogen, ICI 182 780, revealed cross-resistance. Sequence analysis of the hormone-binding domain of the OR of both lines showed no differences, suggesting that either mutations in other regions of the OR are involved in the TAM-resistance phenotype or that mechanisms outside of this protein induced this phenotype. Oestrogen and anti-oestrogen regulate pS2 and cathepsin D expression in 3366 tumours as in the human breast cancer cell line MCF-7. The resistant 3366/TAM tumours have lost this regulation. The established breast cancer xenografts 3366 and 3366/TAM offer the possibility of investigating mechanisms of anti-oestrogen resistance in an in vivo situation. They can be used to test novel approaches to prevent, or to overcome, this resistance in a clinically related manner. © 2000 Cancer Research Campaig

Redox-inactive ions control the redox-activity of molecular vanadium oxides

Polyoxometalates are key materials for energy conversion and storage due to their unique chemical tunability and electrochemical reactivity. Herein, we report that functionalization of molecular vanadium oxides, polyoxovanadates, with redox-inert Ca$^{2+}$ cations leads to a significant increase in their electron storage capabilities. The electrochemical performance of the Ca$^{2+}$-functionalized dodecavanadate [Ca$_{2}$V$_{12}$O$_{32}$Cl(DMF) $_{3}$]$^{2-}$ (={Ca$_{2}$V$_{12}$}) was thus compared with that of the precursor compound (H$_{2}$NMe$_{2}$)$_{2}$ [V$_{12}$O$_{32}$Cl] $^{3-}$ (={V$_{12}$}). {Ca$_{2}$V$_{12}$} can store up to five electrons per cluster, while {V12} only shows one reversible redox transition. In initial studies, we demonstrated that {Ca$_{2}$V$_{12}$} can be used as an active material in lithium-ion cathodes. Our results show how redox-inert cations can be used as structural and electrostatic stabilizers, leading to major changes in the redox-chemistry of polyoxovanadates