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Crystal L Mackall

Publications and source records attributed to Crystal L Mackall.

36 records · Page 2Linked to original sources
PubMed2004

Effect of imatinib mesylate on neuroblastoma tumorigenesis and vascular endothelial growth factor expression.

BACKGROUND: Alternative treatment options are needed for advanced neuroblastoma patients because their prognosis remains poor after intensive chemotherapy. Neuroblastoma cells express platelet-derived growth factor (PDGF), stem cell factor (SCF), and vascular endothelial growth factor (VEGF) and their respective receptors, PDGFR, c-Kit, and Flk-1. We therefore evaluated the effects of imatinib mesylate (imatinib), a selective inhibitor of the tyrosine kinase activities of c-Kit and PDGFR, on the growth of neuroblastoma cells in vivo and in vitro. METHODS: We tested seven human neuroblastoma cell lines for their sensitivity to imatinib. Cell viability was assessed by trypan blue dye exclusion. Apoptosis was evaluated by nuclear staining, flow cytometry, and western blotting. Protein assays included immunoprecipitation, western blotting, enzyme-linked immunosorbent assays, and immunohistochemistry. mRNA expression was assessed by northern blotting. We used a xenograft model in SCID mice (10 mice per group) to evaluate the effects of imatinib oral therapy (50 or 100 mg/kg every 12 hours for 14 days) on neuroblastoma tumor growth. All statistical tests were two-sided. RESULTS: All seven neuroblastoma cell lines treated with imatinib displayed concentration-dependent decreases in cell viability, which coincided with an induction of apoptosis, and with ligand-stimulated phosphorylation of c-Kit and PDGFR. The imatinib concentrations that caused 50% inhibition of growth and 50% inhibition of ligand-induced phosphorylation of these receptors were 9-13 micro M and 0.1-0.5 microM, respectively. Expression of VEGF, but not phosphorylation of Flk-1, its receptor, was reduced in neuroblastoma cells treated with imatinib at 10 microM or higher. Mice treated with imatinib at 50 mg/kg or 100 mg/kg had statistically significantly smaller tumors than control mice treated with vehicle (mean tumor volume in mice treated with imatinib at 50 mg/kg = 1546 mm3, in control mice = 2954 mm3; difference = 1408 mm3, 95% confidence interval [CI] = 657 to 2159 mm3; P<.001; mean tumor volume in mice treated with imatinib at 100 mg/kg = 463 mm3; difference = 2491 mm3, 95% CI = 1740 to 3242 mm3; P<.001). CONCLUSIONS: Imatinib inhibited the growth of neuroblastoma cells in vitro and in vivo. This inhibition was associated with suppression of PDGFR and c-Kit phosphorylation and inhibition of VEGF expression.

Administration, Oral↗
PubMed2004

Pediatric large-volume leukapheresis: a single institution experience with heparin versus citrate-based anticoagulant regimens.

BACKGROUND: Anticoagulant-associated toxicity may exert significant effects on the safety and efficacy of large-volume leukapheresis (LVL) in children, however, few studies specifically address management of this issue. STUDY DESIGN AND METHODS: Seventy-four consecutive LVL procedures (mean, 4 blood volumes processed) in children weighing less than or equal to 30 kg (minimum, 10.9 kg) were analyzed. The first 21 procedures were evaluated retrospectively; 11 used heparin alone (Group I) and 10 used heparin plus reduced-dose ACD-A (whole blood to anticoagulant ratio > or =20:1) (Group II). The next 53 procedures were evaluated prospectively and used full-dose ACD-A (whole blood to anticoagulant ratio < or =13:1), intravenous divalent cation prophylaxis and no heparin; 11 used calcium alone (Group III) followed by 42 with calcium plus magnesium (Group IV). RESULTS: Seventy-four LVL (56 PBPC and 18 MNC) collections were performed in 38 subjects. One donor in Group I experienced a significant groin hematoma at the site of line placement. One donor each in Groups III and IV had mild paresthesias. Despite a mean citrate infusion rate of 2.6 mg per kg per minute, mean postapheresis serum potassium and ionized magnesium and calcium concentrations in Group IV declined by only 9, 8, and 4 percent, respectively, and stable levels of these variables were maintained 24 hours later. Postapheresis PLT counts declined significantly from baseline preapheresis levels in all groups (mean, 52% decrease). CONCLUSIONS: Use of full-dose citrate anticoagulant with prophylactic intravenous divalent cation infusion offers an effective and safe approach to management of anticoagulant-related toxicity in children undergoing LVL.

Adolescent↗
PubMed2003

Induction of caspase 8 by interferon gamma renders some neuroblastoma (NB) cells sensitive to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) but reveals that a lack of membrane TR1/TR2 also contributes to TRAIL resistance in NB.

The resistance of neuroblastoma (NB) cells to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis has been attributed to a lack of caspase 8 expression. Here we demonstrate a clinically applicable molecular targeting strategy that not only increases caspase 8 expression ex vivo in NB cell lines but also in the tumor tissues of NB patients receiving IFN-gamma treatment. We identify the functional caspase 8 promoter, which is different from the methylated region reported previously, and show promoter activity is up-regulated by IFN-gamma through a IFN-gamma activation site-containing region. IFN-gamma also induces TRAIL expression in NB cell lines. However, the IFN-gamma restoration of caspase 8 in some NB cells revealed persistent TRAIL resistance in most NB cell lines examined. This additional lesion in the TRAIL path is because of a loss of cell membrane TRAIL receptors (TR1/TR2) not only in cell lines but in most of the NB tumor tissues evaluated. Restoration of TR2 expression by transfection enhances IFN-gamma-induced TRAIL sensitivity. Furthermore, we have found that we can improve TRAIL sensitivity in NB by reconstituting caspase 8 with IFN-gamma and TR2 with chemotherapeutic agents.

Antineoplastic Agents↗
PubMed2002

Potential use of imatinib in Ewing's Sarcoma: evidence for in vitro and in vivo activity.

BACKGROUND: Ewing's sarcoma cells express c-kit, a receptor tyrosine kinase, and its ligand, stem cell factor (SCF), creating a potential autocrine loop that may promote tumor survival. We thus examined whether the specific tyrosine kinase inhibitor imatinib mesylate (hereafter imatinib; formerly STI571) could inhibit the proliferation of Ewing's sarcoma cells in vitro and in vivo. METHODS: The effect of imatinib on c-kit expression and phosphorylation in Ewing's sarcoma cells was examined by immunoblotting. The effect of imatinib on cell growth and apoptosis was examined with an MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] assay and with a morphologic test and Annexin V staining, respectively. The effect of imatinib oral therapy (every 12 hours for 5-7 days) on primary tumor growth was assessed in Ewing's sarcoma xenografts in SCID/bg mice (5 or 10 mice per group). RESULTS: All Ewing's sarcoma cell lines tested were sensitive to imatinib-mediated apoptosis with a concentration inhibiting growth by 50% (IC50) of 10-12 micro M. Imatinib inhibited SCF-mediated c-kit phosphorylation (IC50 = 0.1-0.5 microM). In the xenograft model, imatinib treatment resulted in the regression or control of primary Ewing's sarcomas. After 6 days of treatment, the mean lower extremity volume including xenograft tumor was 3744 mm3 (95% confidence interval [CI] = 3050 to 4437 mm3), 1442 mm3 (95% CI = 931 to 1758 mm3), and 346 mm3 (95% CI = 131 to 622 mm3) in mice treated with carrier alone or with imatinib at 50 mg/kg or at 100 mg/kg, respectively. CONCLUSIONS: Imatinib interferes with growth of all Ewing's sarcoma cell lines tested in vitro and in vivo. Targeted inhibition of tyrosine kinase-dependent autocrine loops, therefore, may be a viable therapeutic strategy for Ewing's sarcoma.

Animals↗
PubMed2002

IL-7 therapy dramatically alters peripheral T-cell homeostasis in normal and SIV-infected nonhuman primates.

Interleukin-7 (IL-7) is important for thymopoiesis in mice and humans because IL-7 receptor alpha (IL-7Ralpha) mutations result in a severe combined immunodeficiency phenotype with severe thymic hypoplasia. Recent evidence has indicated that IL-7 also plays an important role as a regulator of T-cell homeostasis. Here we report the immunologic effects of recombinant human IL-7 (rhIL-7) therapy in normal and simian immunodeficiency virus (SIV)-infected nonhuman primates. Cynomolgus monkeys receiving 10 days of rhIL-7 showed substantial, reversible increases in T-cell numbers involving a dramatic expansion of both naive and nonnaive phenotype CD4(+) and CD8(+) subsets. Although IL-7 is known to have thymopoietic effects in mice, we observed marked declines in the frequency and absolute number of T-cell receptor excision circle-positive (TREC(+)) cells in the peripheral blood and dramatic increases in the percentage of cycling T cells in the peripheral blood as measured by Ki-67 expression (baseline less than 5% to approximately 50% after 6 days of therapy) and ex vivo bromodeoxyuridine (BrdU) incorporation. Similarly, moderately CD4- depleted SIV-infected macaques treated with rhIL-7 also had significant increases in peripheral blood CD4(+) and CD8(+) T cells following rhIL-7 therapy. Thus, rhIL-7 induces dramatic alterations in peripheral T-cell homeostasis in both T-cell-replete and T-cell-depleted nonhuman primates. These results further implicate IL-7 as a promising immunorestorative agent but illustrate that a major component of its immunorestorative capacity reflects effects on mature cells. These results also raise the possibility that IL-7 therapy could be used to temporarily modulate T-cell cycling in vivo in the context of immunotherapies such as vaccination.

Animals↗
PubMed2002

Interleukin 7 worsens graft-versus-host disease.

Impaired immune reconstitution has moved to the forefront of clinical problems limiting progress in allogeneic bone marrow transplantation (BMT). The identification of therapies that can enhance immune reconstitution by increasing thymopoiesis is critical to solving this problem. Interleukin 7 (IL-7) is the most potent thymopoietic cytokine identified thus far. To study the effects of IL-7 on immune reconstitution and graft-versus-host disease (GVHD) following allogeneic BMT, we administered recombinant human IL-7 (rhIL-7) in a murine parent into an F1 model. Results showed that rhIL-7 therapy lowered the "threshold" T-cell dose required to induce both clinical signs of GVHD as well as lethal GVHD. Histologic analysis of GVHD target tissues revealed that rhIL-7 increased the degree of inflammation and tissue damage observed at all T-cell doses studied, but did not change the pattern of organs affected or the histologic appearance of the GVHD within target organs. In addition, we evaluated the capacity for rhIL-7 to enhance thymopoiesis in the setting of allogeneic T cell-depleted (TCD) and T-cell-replete BMT. We observed that rhIL-7 therapy enhanced thymic function in TCD allogeneic BM transplant recipients, but not in animals that received even modest doses of T cells presumably due to thymic toxicity of the graft-versus-host reaction. Thus, caution must be exercised as IL-7 is developed clinically as an immunorestorative agent for use in the setting of allogeneic BMT. These results suggest that use of IL-7 should be limited to the setting of TCD BMT to obtain the greatest benefit on immune competence with the least toxicity.

Animals↗
PubMed2002

Pilot trial of tumor-specific peptide vaccination and continuous infusion interleukin-2 in patients with recurrent Ewing sarcoma and alveolar rhabdomyosarcoma: an inter-institute NIH study.

BACKGROUND: Patients with recurrent Ewing sarcoma and alveolar rhabdomyosarcoma have poor prognoses and limited therapeutic options. We have investigated the use of peptide pulsed vaccination in an attempt to immunologically target the breakpoint region of tumor specific fusion proteins expressed in these tumors. PROCEDURE: Sixteen patients with recurrent, translocation positive, Ewing sarcoma, and alveolar rhabdomyosarcoma underwent apheresis for collection of peripheral blood mononuclear cells. Following countercurrent centrifugal elutriation, an apheresis product comprised predominantly of monocytes but containing small numbers of circulating immature dendritic cells was pulsed with peptides derived from the breakpoint region of the fusion proteins. Vaccines were administered intravenously concomitant with continuous intravenous rhIL-2 at 9 x 10(6) IU/m(2)/day. RESULTS: Toxicity was limited to IL-2 related effects and was generally mild. Following vaccination, all patients showed progressive disease, most in a rapid fashion following the first vaccine. One patient showed evidence of an immunologic response and another showed a mixed clinical response. Patients enrolled on this tumor vaccine trial showed significant immunosuppression and large bulky tumors. CONCLUSIONS: Peptide vaccination as administered in this trial did not alter the dismal clinical outcome for patients with recurrent pediatric sarcomas. Future trials of tumor vaccines in this population should target patient populations with improved immune competence and smaller tumor burdens. Furthermore, optimization of the antigen presenting cell populations may be important for inducing immune responses to peptide antigens.

Adolescent↗
PubMed2002

Bax deficiency partially corrects interleukin-7 receptor alpha deficiency.

The requirement for cytokines in hematopoiesis is partly attributable to the protection of cells from apoptosis. Since IL-7 is required for normal T cell development, we evaluated the role of Bax in vivo by generating mice deficient in both Bax and the IL-7 receptor alpha chain (IL-7R). Starting at birth, we observed complete recovery of all stages of alphabeta thymocyte development up to 4 weeks of age. However, by 12 weeks of age, thymic cellularity had reverted to that of mice deficient in IL-7R alone. The BH3 only proteins, Bad and Bim, were also part of the death pathway repressed by IL-7. Thus, in young mice, Bax emerges as an essential protein in the death pathway induced by IL-7 deficiency.

Aging↗
PubMed2002

Focus on sarcomas.

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Cell Differentiation↗
PubMed2002

Interleukin-7 and immunorestoration in HIV: beyond the thymus.

One of the hallmarks of untreated HIV infection is a progressive loss of effective immunity to both HIV-associated and non-HIV antigens. Combination antiretroviral therapy can frequently control viral replication, resulting in variable levels of immune reconstitution, but has not resulted in restoration of effective immunity to the virus. Understanding the limitations of immune reconstitution following highly active antiretroviral therapy (HAART) and identifying approaches to enhance immunity in this context may not only improve outcome for patients with HIV infection but could also provide insight for immune reconstitution in other conditions associated with T cell depletion.

Anti-HIV Agents↗
PubMedDate not supplied

Escape from immune surveillance does not result in tolerance to tumor-associated antigens.

Despite expression of tumor-associated or tumor-specific antigens by most tumors, evasion of protective T-cell immunity is the rule rather than the exception. Understanding whether tumor immune escape primarily represents T-cell neglect, anergy/tolerance, or quantitative limits of an existent immune response is central to developing new strategies to enhance antitumor immunity. The authors studied the immune response to MB49, a tumor that naturally expresses HY. Immune surveillance was effective following low-dose tumor inocula, since normal female mice showed a diminished incidence and slower growth rate of MB49 compared with T-cell-depleted female mice and male mice. Following high-dose tumor inoculation, females developed large, progressive tumors but continued to demonstrate immune responses to class I and class II restricted HY epitopes. The HY reactive T cells remained capable of executing HY immune responses since T cells adoptively transferred from MB49-bearing animals mediated accelerated HY skin graft rejection compared with those taken from naive mice. Thus, MB49 does not induce immune tolerance to HY but rather escapes immune surveillance largely due to quantitative limits of the immune response. Treatment of tumor-bearing animals with rhIL7 significantly increased the number of T cells responding to HY but did not alter tumor growth rate. These results demonstrate that escape from immune surveillance does not necessarily imply immune tolerance to tumor antigens and that immunotherapy need not overcome tumor-induced tolerance per se, and suggest that substantial opportunities remain in tumor-bearing hosts to amplify weak but persistent antitumor immune responses.

Adoptive Transfer↗
PubMedDate not supplied

Treatment of metastatic osteosarcoma with the somatostatin analog OncoLar: significant reduction of insulin-like growth factor-1 serum levels.

BACKGROUND: Insulin-like growth factor-1 (IGF-1) has been implicated in the growth and/or metastasis of osteosarcoma (OS) and chondrosarcoma based on in vitro and experimental animal studies. STUDY PURPOSE: To determine the degree of growth hormone (GH), IGF-1 axis blockade, toxicities, and antitumor effect of OncoLar (ONC) (Novartis, East Hanover, NJ, U.S.A.) in OS. DESIGN/METHODS: A phase 1 study with ONC enrolled 21 OS patients (median age 19 y) in four cohorts: ONC 60 mg or 90 mg intramuscularly every 4 weeks with/without tamoxifen (TAM) 20 mg oral daily. RESULTS: There were no dose-limiting toxicities. Nineteen percent of patients had grade III drug-related toxicities including: 62% of patients showed progressive disease after two courses (8 wk). Nineteen percent received four courses. No clinical responses were observed. At weeks two and eight of therapy, IGF-1 serum levels dropped 46% ( < 0.0001, n = 21) and 53% ( = 0.003, n = 10). The difference of the area under the curve (AUC) minus baseline AUC (DeltaAUC) for arginine-stimulated GH serum levels at week two was lower than baseline ( < 0.01). At weeks two and eight, GH peak values were lower than baseline ( < 0.0001 and = 0.002, respectively). CONCLUSIONS: A long-acting somatostatin analog was able to lower IGF-1 levels of OS patients. IGF-BP-3 and GH were only transiently reduced. Although ONC was well tolerated, no sustained clinical responses were observed. The pathophysiology of serum versus tissue concentrations of IGF-1 as well as the interplay of IGFs, IGF-binding proteins, and other growth factors and cytokines in osteosarcoma warrants further investigation. A better understanding of these processes should lead to a more effective exploitation of these pathways for the targeted therapy of OS.

Adolescent↗
PubMedDate not supplied

Cytokine signals in T-cell homeostasis.

Thymic production of T cells declines rapidly with age, and therefore homeostatic cycling (HC) of mature lymphocytes plays an important role in maintaining stable numbers of mature T lymphocytes bearing sufficient repertoire diversity. Following lymphocyte depletion, HC changes in quality and magnitude, resulting in homeostatic peripheral expansion (HPE), a state of widespread T-cell cycling that serves to increase T-cell number and to maintain T-cell repertoire diversity to the greatest extent possible. Recent studies delineating the requirements for HC and HPE have shown that naive CD4+ cells and naive CD8+ cells require both IL7 and TCR engagement for survival, cycling, and homeostatic expansion, whereas CD8+ memory cells are maintained and expanded by cytokine signals alone, independent of TCR engagement. While basal levels of IL15 are sufficient for HC and HPE of CD8+ memory cells, supranormal levels of IL7 will also suffice. The requirements for memory CD4+ cells remain unclear, but current models hypothesize that either IL7 or TCR triggering may be sufficient. Thus, the changes in immune physiology that are present in lymphopenic hosts can be largely accounted for by cytokine-driven signals, especially those rendered by IL7 or IL15. As the alterations in immune physiology present in lymphopenic hosts may be conducive to stronger antitumor immune responsiveness, careful delineation of the factors responsible may be expected to give rise to approaches to augment the effectiveness of current antitumor immunotherapies.

Animals↗
PubMedDate not supplied

IL-7 administration to humans leads to expansion of CD8+ and CD4+ cells but a relative decrease of CD4+ T-regulatory cells.

Lymphopenia is a serious consequence of HIV infection and the administration of cancer chemotherapeutic agents. Although growth factors can be administered to patients to increase circulating neutrophils, there is no effective method to stimulate CD8+ lymphocyte production in humans, in vivo. This report is the first to describe the administration of recombinant interleukin-7 to humans and demonstrates the ability of this cytokine to mediate selective increases in CD4+ and CD8+ lymphocytes along with a decrease in the percentage of CD4+ T-regulatory cells. These studies suggest an important role for interleukin-7 in the treatment of patients with lymphopenia.

Adult↗
PubMedDate not supplied

Ewing sarcoma family of tumors in unusual sites: confirmation by rt-PCR.

Ewing sarcoma family tumors originating in the palate or adrenal gland are extremely rare and may cause difficulty in diagnosis. More common tumors primary to these sites need to be excluded before one arrives at the correct diagnosis. We have recently diagnosed 2 such cases. The 1st case was that of a 24-year-old woman who presented with a swelling in the right side of the hard palate. The 2nd case was diagnosed in a 28-year-old woman who presented with a mass in the right adrenal gland. In both cases, the diagnosis of Ewing sarcoma family of tumors was confirmed by immunohistochemical studies and reverse transcriptase-polymerase chain reaction (RT-PCR). The hard palate case is the 1st and the adrenal gland the 3rd case of Ewing sarcoma family of tumors arising in these sites, in which the diagnosis was confirmed by RT-PCR and/or cytogenetics. Accurate diagnosis of Ewing sarcoma family of tumors is crucial for the management of patients, and when found in such rare locations, diagnosis should be supported by immunohistochemical and/or molecular genetic studies.

Adrenal Gland Neoplasms↗
PubMedDate not supplied

Tumor expression of 4-1BB ligand sustains tumor lytic T cells.

Inadequate costimulation by solid tumors is generally believed to induce immune tolerance during primary tumor growth. We looked for tumor-specific immunity vs. tolerance in patients with Ewing's sarcoma. Circulating T cells from patients with progressively growing Ewing's tumors displayed MHC restricted tumor-induced proliferation and robust tumor lysis. Tumor-reactive T cells reside within the memory CD3+CD8+ subset and are CD28-/4-1BB+. Autologous Ewing's tumors expressed 4-1BBL, and tumor-induced T cell proliferation and activation required costimulation by 4-1BBL. Stimulation of PBL with anti-CD3/4-1BBL, but not anti-CD3/anti-CD28 induced tumor lytic effectors. Similarly, in a xenograft model, anti-CD3/4-1BBL expanded T cells controlled primary growth and prevented metastasis of autologous tumors while nonactivated and anti-CD3/anti-CD28 activated CD8+ cells did not. These results question prevailing models of tumor induced tolerance accompanying progressive tumor growth; rather, we show coexistence of progressive tumor growth and anti-tumor immunity, with costimulation provided by the tumor itself. They further demonstrate a potential new therapeutic role for 4-1BBL mediated costimulation in expanding tumor reactive CTLs for use in the adoptive immunotherapy of cancer.

4-1BB Ligand↗