We previously identified a distinct population of human circulating hematopoietic
stem and progenitor cells (CHSPCs;
cells) in the peripheral blood (PB) and bone marrow, and their frequency in the PB can
correlate with disease state. The proangiogenic subset (pCHSPC) play a role in regulating
tumor progression, for we previously demonstrated a statistically significant increase in
C32 melanoma growth in NOD.Cg-Prkdcscid (NOD/SCID) injected
with human pCHSPCs (p<0.001). We now provide further evidence that pCHSPCs possess
proangiogenic properties. In vitro bio-plex cytokine analyses and tube
forming assays indicate that pCHSPCs secrete a proangiogenic profile and promote vessel
formation respectively. We also developed a humanized bone marrow-melanoma orthotopic
model to explore in vivo the biological significance of the pCHSPC
population. Growth of melanoma xenografts increased more rapidly at 3-4 weeks post-tumor
implantation in mice previously transplanted with human CD34+ cells
compared to control mice. Increases in pCHSPCs in PB correlated with increases in tumor
growth. Additionally, to determine if we could prevent the appearance of pCHSPCs in the
PB, mice with humanized bone marrow-melanoma xenografts were administered Interferon
α-2b, which is used clinically for treatment of melanoma. The mobilization of the
pCHSPCs was decreased in the mice with the humanized bone marrow-melanoma xenografts.
Taken together, these data indicate that pCHSPCs play a functional role in tumor growth.
The novel in vivo model described here can be utilized to further
validate pCHSPCs as a biomarker of tumor progression. The model can also be used to screen
and optimize anticancer/anti-angiogenic therapies in a humanized system.
proangiogenic; circulating hematopoietic stem and progenitor cells; biomarker; tumor growth
Inhibition of vascular endothelial growth factor (VEGF) increases response rates to chemotherapy and progression-free survival in glioblastoma. However, resistance invariably occurs, prompting the urgent need for identification of synergizing agents. One possible strategy is to understand tumor adaptation to microenvironmental changes induced by antiangiogenic drugs, and test agents that exploit this process. We used an in vivo glioblastoma-derived xenograft model of tumor escape in presence of continuous treatment with Bevacizumab. U87-MG or U118-MG cells were subcutaneously implanted into either BALB/c SCID or athymic nude mice. Bevacizumab was given by intraperitoneal injection every 3 days (2.5mg/kg/dose) and/or dichloroacetate (DCA) was administered by oral gavage twice daily (50mg/kg/dose) when tumor volumes reached 0.3cm3, and continued until tumors reached approximately 1.5–2.0cm3. Microarray analysis of resistant U87 tumors revealed coordinated changes at the level of metabolic genes, in particular a widening gap between glycolysis and mitochondrial respiration. There was a highly significant difference between U87-MG implanted athymic nude mice 1 week after drug treatment. By 2 weeks of treatment, Bevacizumab and DCA together dramatically blocked tumor growth compared to either drug alone. Similar results were seen in athymic nude mice implanted with U118-MG cells. We demonstrate for the first time that reversal of the Bevacizumab-induced shift in metabolism using DCA is detrimental to neoplastic growth in vivo. As DCA is viewed as a promising agent targeting tumor metabolism, our data establish timely proof of concept that combining it with antiangiogenic therapy represents a potent antineoplastic strategy.
Dichloroacetate; hypoxia; Bevacizumab; oxidative phosphorylation; glycolysis
The uPAR·uPA protein-protein interaction (PPI) is involved in signaling and proteolytic events that promote tumor invasion and metastasis. A previous study had identified 4 (IPR-803) from computational screening of a commercial chemical library and shown that the compound inhibited uPAR·uPA PPI in competition biochemical assays and invasion cellular studies. Here, we synthesize 4 to evaluate in vivo pharmacokinetic (PK) and efficacy studies in a murine breast cancer metastasis model. First, we show, using fluorescence polarization and saturation transfer difference (STD) NMR, that 4 binds directly to uPAR with sub-micromolar affinity of 0.2 μM. We show that 4 blocks invasion of breast MDA-MB-231, and inhibits matrix metalloproteinase (MMP) breakdown of the extracellular matrix (ECM). Derivatives of 4 also inhibited MMP activity and blocked invasion in a concentration-dependent manner. 4 also impaired MDA-MB-231 cell adhesion and migration. Extensive in vivo PK studies in NOD-SCID mice revealed a half-life of nearly 5 hours and peak concentration of 5 μM. Similar levels of the inhibitor were detected in tumor tissue up to 10 hours. Female NSG mice inoculated with highly malignant TMD-MDA-MB-231 in their mammary fat pads showed that 4 impaired metastasis to the lungs with only four of the treated mice showing severe or marked metastasis compared to ten for the untreated mice. Compound 4 is a promising template for the development of compounds with enhanced PK parameters and greater efficacy.
Immunostimulatory cytokines can enhance anti-tumor immunity and are part of the therapeutic armamentarium for cancer treatment. We have previously reported that post-transplant lymphoma patients have an acquired deficiency of signal transducer and activator of transcription 4, which results in defective IFNγ production during clinical immunotherapy. With the goal of further improving cytokine-based immunotherapy, we examined the effects of a soybean peptide called lunasin that synergistically works with cytokines on natural killer (NK) cells. Peripheral blood mononuclear cells of healthy donors and post-transplant lymphoma patients were stimulated with or without lunasin in the presence of IL-12 or IL-2. NK activation was evaluated, and its tumoricidal activity was assessed using in vitro and in vivo tumor models. Chromatin immunoprecipitation assay was performed to evaluate the histone modification of gene loci that are regulated by lunasin and cytokine. Adding lunasin to IL-12- or IL-2-stimulated NK cells demonstrated synergistic effects in the induction of IFNG and GZMB involved in cytotoxicity. The combination of lunasin and cytokines (IL-12 plus IL-2) was capable of restoring IFNγ production by NK cells from post-transplant lymphoma patients. In addition, NK cells stimulated with lunasin plus cytokines displayed higher tumoricidal activity than those stimulated with cytokines alone using in vitro and in vivo tumor models. The underlying mechanism responsible for the effects of lunasin on NK cells is likely due to epigenetic modulation on target gene loci. Lunasin represents a different class of immune modulating agent that may augment the therapeutic responses mediated by cytokine-based immunotherapy.
Lunasin; NK; Cytokine immunotherapy; Lymphoma
Virtual screening targeting the urokinase receptor (uPAR) led to (3R)-4-cyclohexyl-3-(hexahydrobenzo[d][1,3]dioxol-5-yl)-N-((hexahydrobenzo[d][1,3]dioxol-5-yl)methyl)butan-1-aminium 1 (IPR-1) and 4-(4-((3,5-dimethylcyclohexyl)carbamoyl)-2-(4-isopropylcyclohexyl)pyrazolidin-3-yl)piperidin-1-ium 3 (IPR-69). Synthesis of an analog of 1, namely 2 (IPR-9), and 3 led to breast MDA-MB-231 invasion, migration and adhesion assays with IC50 near 30 μM. Both compounds blocked angiogenesis with IC50 of 3 μM. Compounds 2 and 3 inhibited cell growth with IC50 of 6 and 18 μM and induced apoptosis. Biochemical assays revealed lead-like properties for 3, but not 2. Compound 3 administered orally reached peak concentration of nearly 40 μM with a half-life of about 2 hours. In NOD-SCID mice inoculated with breast TMD-231 cells in their mammary fat pads, compound 3 showed a 20% reduction in tumor volumes and less extensive metastasis was observed for the treated mice. The suitable pharmacokinetic properties of 3 and the encouraging preliminary results in metastasis make it an ideal starting point for next generation compounds.
Pancreatic cancer is an especially deadly form of cancer with a survival rate <2%. Pancreatic cancers respond poorly to existing chemotherapeutic agents and radiation, and progress for the treatment of pancreatic cancer remains elusive. To address this unmet medical need, a better understanding of critical pathways and molecular mechanisms involved in pancreatic tumor development, progression and resistance to traditional therapy is therefore critical. Reduction-oxidation (redox) signaling systems are emerging as important targets in pancreatic cancer. AP endonuclease1/ Redox effector factor 1 (APE1/Ref-1) is upregulated in human pancreatic cancer cells and modulation of its redox activity blocks the proliferation and migration of pancreatic cancer cells as well as pancreatic cancer-associated endothelial cells (PCECs) in vitro. Modulation of APE1/Ref-1 using a specific inhibitor of APE1/Ref-1’s redox function, E3330 leads to a decrease in transcription factor activity for NFκB, AP-1, and HIF1 in vitro. This study aims to further establish the redox signaling protein APE1/Ref-1 as a molecular target in pancreatic cancer. Here, we show that inhibition of APE1/Ref-1 via E3330 results in tumor growth inhibition in cell lines as well as pancreatic cancer xenograft models in mice. Pharmacokinetic (PK) studies also demonstrate that E3330 attains >10 μM blood concentrations and is detectable in tumor xenografts. Through inhibition of APE1/Ref-1, the activity of NFκB, AP-1, and HIF1α which are key transcriptional regulators involved in survival, invasion and metastasis is blocked. These data indicate that E3330, inhibitor of APE1/Ref-1, has potential in pancreatic cancer and clinical investigation of APE1/Ref-1 molecular target is warranted.
Pancreatic cancer; animal models of cancer; new targets; xenograft models; cellular responses to anticancer drugs; cellular pharmacology; pharmacokinetics and pharmacodynamics; agents with other mechanisms of action
Pre-clinical in vivo studies can help guide the selection of agents and regimens for clinical testing. However, one of the challenges in screening anti-cancer therapies is the assessment of off-target human toxicity. There is a need for in vivo models that can simulate efficacy and toxicities of promising therapeutic regimens. For example, hematopoietic cells of human origin are particularly sensitive to a variety of chemotherapeutic regimens but in vivo models to assess potential toxicities have not been developed. In this study, a xenograft model containing humanized bone marrow is utilized as an in vivo assay to monitor hematotoxicity.
A proof-of-concept, temozolomide-based regimen was developed that inhibits tumor xenograft growth. This regimen was selected for testing since it has been previously shown to cause myelosuppression in mice and humans. The dose-intensive regimen was administered to NOD/SCID/γchainnull mice reconstituted with human hematopoietic cells and the impact of treatment on human hematopoiesis was evaluated.
The dose-intensive regimen resulted in significant decreases in growth of human-glioblastoma xenografts. When this regimen was administered to mice containing humanized bone marrow, flow cytometric analyses indicated that the human bone-marrow cells were significantly more sensitive to treatment than the murine bone-marrow cells, and that the regimen was highly toxic to human-derived hematopoietic cells of all lineages (progenitor, lymphoid, and myeloid).
The humanized bone-marrow xenograft model described has the potential to be used as a platform for monitoring the impact of anti-cancer therapies on human hematopoiesis and could lead to subsequent refinement of therapies prior to clinical evaluation.
human xenograft model; myelosuppression; stem-cell
Humanized bone-marrow xenograft models that can monitor the long-term impact of gene-therapy strategies will help facilitate evaluation of clinical utility. The ability of the murine bone-marrow microenvironment in NOD/SCID versus NOD/SCID/γ chainnull mice to support long-term engraftment of MGMTP140K-transduced human-hematopoietic cells following alkylator-mediated in vivo selection was investigated. Mice were transplanted with MGMTP140K-transduced CD34+ cells and transduced cells selected in vivo. At 4 months after transplantation, levels of human-cell engraftment, and MGMTP140K-transduced cells in the bone marrow of NOD/SCID versus NSG mice varied slightly in vehicle- and drug-treated mice. In secondary transplants, although equal numbers of MGMTP140K-transduced human cells were transplanted, engraftment was significantly higher in NOD/SCID/γ chainnull mice compared to NOD/SCID mice at 2 months after transplantation. These data indicate that reconstitution of NOD/SCID/γ chainnull mice with human-hematopoietic cells represents a more promising model in which to test for genotoxicity and efficacy of strategies that focus on manipulation of long-term repopulating cells of human origin.
We recently reported that murine marrow cultured ex vivo for gamma-retrovirus transduction engrafts ~10 fold less well than fresh marrow upon transplantation into submyeloablated hosts. Here, we evaluated homing efficiency as a potential mechanism for this engraftment disparity, and whether CD26 inhibition with the tripeptide Diprotin A (DipA) would enhance engraftment of ex vivo cultured cells in submyeloablated hosts.
Homing and engraftment of fresh and ex vivo cultured lineage-negative (lin-) marrow cells in submyeloablated congenic hosts with and without DipA treatment was evaluated. Expression of CXCR4 and CD26 on fresh and cultured lin- marrow cells was compared.
Homing of lin- cells cultured for gamma-retrovirus transduction was ≥3-fold less than that of fresh lin- cells 20 hours after transplantation into submyeloablated hosts. DipA treatment of fresh lin- cells resulted in ≥-fold increased homing and engraftment in submyeloablated hosts. DipA treatment, however, did not significantly improve homing or engraftment of cells undergoing a three-day culture protocol for gamma-retrovirus transduction in submyeloablated hosts. CXCR4 expression on lin- cells was significantly decreased following three days of culture; CXCR4 expression was not significantly altered following overnight culture.
Ex vivo culture of lin- cells for gamma-retroviral transduction downregulates CXCR4 expression and markedly impairs homing and engraftment of murine lin- marrow in submyeloablated hosts. While inhibition of CD26 activity with DipA increases homing and engraftment of fresh lin- cells, DipA treatment does not improve homing and engraftment of cultured lin- marrow cells in submyeloablated congenic hosts.
Through its ability to both induce immunosuppression and act as a carcinogen, UVB radiation plays a major role in cutaneous malignancies. Recent studies have indicated that UVB-mediated inhibition of delayed-type hypersensitivity reactions is mediated, in part, by the lipid mediator platelet-activating factor (PAF). The objective of this study was to further define the mechanism by which UVB inhibits contact hypersensitivity (CHS) reactions. UVB irradiation resulted in an inhibition of subsequent CHS to the chemical DNFB in wild-type, but not in PAF-R-deficient mice. UVB-mediated inhibition of CHS was also blocked by a cyclooxygenase-2 (COX-2) inhibitor or a neutralizing antibody directed against IL-10. UVB irradiation upregulated IL-10 mRNA levels in lymph nodes and spleen only to significant levels in PAF-R-expressing mice. Bone marrow transplantation studies demonstrated that UVB-mediated immunomodulatory effects were dependent on PAF-R-positive bone marrow. These studies suggest that UVB irradiation results in epidermal production of PAF agonists, which then act on PAF-R-positive bone marrow-derived cells to upregulate IL-10 through COX-2-generated prostaglandins.
Using a clinically relevant transduction strategy, we investigated to what extent hematopoietic stem cells in lineage-negative bone marrow (Linneg BM) could be genetically modified with a FV vector that expresses the DNA repair protein, O6-methylguanine DNA methyltransferase (MGMTP140K) and selected in vivo with submyeloablative versus myeloablative alkylator therapy.
Linneg BM was transduced at a low multiplicity-of-infection (MOI), with the FV vector, MD9-P140K, that co-expresses MGMTP140K and the enhanced green fluorescent protein, transplanted into C57BL/6 mice, and mice treated with submyeloablative or myeloablative alkylator therapy. The BM was analyzed for the presence of in vivo selected, MD9-P140K-transduced cells at 6 months post-transplantation and subsequently transplanted into secondary recipient animals.
Following submyeloablative therapy, 55% of the mice expressed MGMTP140K in the BM. Proviral integration was observed in ∼50% of committed BM-derived progenitors and analysis of proviral insertion sites indicated up to 2 integrations per transduced progenitor colony. Transduced BM cells selected with submyeloablative therapy reconstituted secondary recipient mice for up to 6 months post-transplantation. In contrast, following delivery of myeloablative therapy to primary recipient mice, only 25% survived. Hematopoietic stem cells were transduced since BM cells from the surviving animals reconstituted secondary recipients with MGMTP140K positive cells for 5-6 months.
In vivo selection of MD9-P140K-transduced BM cells was more efficient following submyeloablative versus myeloablative therapy. These data indicate that a critical number of transduced-stem cells must be present to produce sufficient numbers of genetically modified progeny to protect against the acute toxicity associated with myeloablative therapy.
gene therapy; hematopoietic stem cells; foamy virus vector; O6-methylguanine DNA methyltransferase (MGMT)
Standard competitive repopulation assays have proven valuable in evaluating engraftment potential in ablated hosts, permitting comparisons between various test cell populations. However, no similar method exists to compare engraftment of test cells in submyeloablated hosts, which would be helpful given the applications of reduced-intensity conditioning for hematopoietic gene-replacement therapy and other cellular therapies. Here, we developed a novel assay to quantitate engraftment of hematopoietic stem cells in submyeloablated hosts.
Engraftment of murine marrow cells transduced with retroviral vectors using two separate protocols was compared to engraftment of fresh untreated competitor cells within low-dose radiation conditioned hosts using a “three-way” marking system, so that test, competitor and host cell chimerism could be reliably determined post-transplant.
We demonstrate that the repopulating ability of marrow cells transduced using two distinct protocols was reduced ~10-fold compared to fresh competitor cells in submyeloablated hosts utilizing the novel “three-way” transplant assay.
Murine marrow cells transduced using a clinically-applicable protocol acquire an engraftment defect in submyeloablated hosts, similar to cells transduced using a research protocol. We conclude that the submyeloablative competitive repopulation assay described here will be of benefit to comparatively assess the engraftment ability of manipulated hematopoietic stem cells using various culture protocols, such as to test the impact of modifications in transduction protocols needed to attain therapeutic levels of gene-corrected blood cells, or the effect of ex vivo expansion protocols on engraftment potential.
Engraftment; conditioning; submyeloablative; transduction; hematopoietic stem cells