Endothelial cell death after ionizing radiation does not impair vascular structure in mouse tumor models.

The effect of radiation therapy on tumor vasculature has long been a subject of debate. Increased oxygenation and perfusion have been documented during radiation therapy. Conversely, apoptosis of endothelial cells in irradiated tumors has been proposed as a major contributor to tumor control. To examine these contradictions, we use multiphoton microscopy in two murine tumor models: MC38, a highly vascularized, and B16F10, a moderately vascularized model, grown in transgenic mice with tdTomato-labeled endothelium before and after a single (15 Gy) or fractionated (5 × 3 Gy) dose of radiation. Unexpectedly, even these high doses lead to little structural change of the perfused vasculature. Conversely, non-perfused vessels and blind ends are substantially impaired after radiation accompanied by apoptosis and reduced proliferation of their endothelium. RNAseq analysis of tumor endothelial cells confirms the modification of gene expression in apoptotic and cell cycle regulation pathways after irradiation. Therefore, we conclude that apoptosis of tumor endothelial cells after radiation does not impair vascular structure.

Associations between courses of posttraumatic stress disorder and physical health conditions among Canadian military personnel.

BACKGROUND: Posttraumatic stress disorder (PTSD) and physical health conditions commonly co-occur and are both prevalent among military personnel. This study examined how courses of PTSD (no PTSD, remitted, new onset, persistent/recurrent) are associated with physical health conditions, among a population-based sample of Canadian military personnel. METHOD: We analyzed data from the 2002 Canadian Community Health Survey-Mental Health and Well-being-Canadian Forces supplement (CCHS-CF) and the 2018 Canadian Armed Forces Members and Veterans Mental Health Follow-Up Survey (CAFVMHS; N = 2941). Multivariable logistic regressions examined associations between PTSD courses (reference = no PTSD) and physical health conditions. RESULTS: In general, physical health conditions were more prevalent among symptomatic PTSD courses compared to no PTSD. After adjustment, new onset PTSD was associated with increased odds of all physical health conditions with the exception of ulcers and cancer (AOR range: 1.41-2.31) and remitted PTSD was associated with increased odds of diabetes (AOR = 2.31). CONCLUSION: Results suggest that new onset PTSD may be most strongly associated with physical health conditions. Findings may inform targeted screening and intervention methods among military personnel with PTSD and physical health conditions.

Olaparib increases the therapeutic index of hemithoracic irradiation compared with hemithoracic irradiation alone in a mouse lung cancer model.

BACKGROUND: The radiosensitising effect of the poly(ADP-ribose) polymerase inhibitor olaparib on tumours has been reported. However, its effect on normal tissues in combination with radiation has not been well studied. Herein, we investigated the therapeutic index of olaparib combined with hemithoracic radiation in a urethane-induced mouse lung cancer model. METHODS: To assess tolerability, A/J mice were treated with olaparib plus whole thorax radiation (13 Gy), body weight changes were monitored and normal tissue effects were assessed by histology. In anti-tumour (intervention) studies, A/J mice were injected with urethane to induce lung tumours, and were then treated with olaparib alone, left thorax radiation alone or the combination of olaparib plus left thorax radiation at 8 weeks (early intervention) or 18 weeks (late intervention) after urethane injection. Anti-tumour efficacy and normal tissue effects were assessed by visual inspection, magnetic resonance imaging and histology. RESULTS: Enhanced body weight loss and oesophageal toxicity were observed when olaparib was combined with whole thorax but not hemithorax radiation. In both the early and late intervention studies, olaparib increased the anti-tumour effects of hemithoracic irradiation without increasing lung toxicity. CONCLUSIONS: The addition of olaparib increased the therapeutic index of hemithoracic radiation in a mouse model of lung cancer.

Radiosensitivity of colorectal cancer to 90Y and the radiobiological implications for radioembolisation therapy.

Approximately 50% of all colorectal cancer (CRC) patients will develop metastasis to the liver. 90Y selective internal radiation therapy (SIRT) is an established treatment for metastatic CRC. There is still a fundamental lack of understanding regarding the radiobiology underlying the dose response. This study was designed to determine the radiosensitivity of two CRC cell lines (DLD-1 and HT-29) to 90Y ß - radiation exposure, and thus the relative effectiveness of 90Y SIRT in relation to external beam radiotherapy (EBRT). A 90Y-source dish was sandwiched between culture dishes to irradiate DLD-1 or HT-29 cells for a period of 6 d. Cell survival was determined by clonogenic assay. Dose absorbed per 90Y disintegration was calculated using the PENELOPE Monte Carlo code. PENELOPE simulations were benchmarked against relative dose measurements using EBT3 GAFchromic™ film. Statistical regression based on the linear-quadratic model was used to determine the radiosensitivity parameters [Formula: see text] and [Formula: see text] using R. These results were compared to radiosensitivity parameters determined for 6 MV clinical x-rays and 137Cs γ-ray exposure. Equivalent dose of EBRT in 2 Gy ([Formula: see text]) and 10 Gy ([Formula: see text]) fractions were derived for 90Y dose. HT-29 cells were more radioresistant than DLD-1 for all treatment modalities. Radiosensitivity parameters determined for 6 MV x-rays and 137Cs γ-ray were equivalent for both cell lines. The [Formula: see text] ratio for 90Y ß --particle exposure was over an order of magnitude higher than the other two modalities due to protraction of dose delivery. Consequently, an 90Y SIRT absorbed dose of 60 Gy equates to an [Formula: see text] of 28.7 and 54.5 Gy and an [Formula: see text] of 17.6 and 19.3 Gy for DLD-1 and HT-29 cell lines, respectively. We derived radiosensitivity parameters for two CRC cell lines exposed to 90Y ß --particles, 6 MV x-rays, and 137Cs γ-ray irradiation. These radiobiological parameters are critical to understanding the dose response of CRC lesions and ultimately informs the efficacy of 90Y SIRT relative to other radiation therapy modalities.

Characterisation of Deubiquitylating Enzymes in the Cellular Response to High-LET Ionizing Radiation and Complex DNA Damage.

PURPOSE: Ionizing radiation, particular high-linear energy transfer (LET) radiation, can induce complex DNA damage (CDD) wherein 2 or more DNA lesions are induced in close proximity, which contributes significantly to the cell killing effects. However, knowledge of the enzymes and mechanisms involved in coordinating the recognition and processing of CDD in cellular DNA are currently lacking. METHODS AND MATERIALS: A small interfering RNA screen of deubiquitylation enzymes was conducted in HeLa cells irradiated with high-LET α-particles or protons, versus low-LET protons and x-rays, and cell survival was monitored by clonogenic assays. Candidates whose depletion led to decreased cell survival specifically in response to high-LET radiation were validated in both HeLa and oropharyngeal squamous cell carcinoma (UMSCC74A) cells, and the association with CDD repair was confirmed using an enzyme modified neutral comet assay. RESULTS: Depletion of USP6 decreased cell survival specifically after high-LET α-particles and protons, but not low-LET protons or x-rays. USP6 depletion caused cell cycle arrest and a deficiency in CDD repair mediated through instability of poly(ADP-ribose) polymerase-1 (PARP-1) protein. Increased radiosensitivity of cells to high-LET protons as a consequence of defective CDD repair was furthermore mimicked using the PARP inhibitor olaparib, and through PARP-1 small interfering RNA. CONCLUSIONS: USP6 controls cell survival in response to high-LET radiation by stabilizing PARP-1 protein levels, which is essential for CDD repair. We also describe synergy between CDD induced by high-LET protons and PARP inhibition, or PARP-1 depletion, in effective cancer cell killing.

Effects of variations in overall treatment time on the clonogenic survival of V79-4 cells: Implications for radiosurgery.

The importance of effects related to the repair of sublethal radiation damage as treatment duration varies, partly a function of dose-rate, is a current controversy in clinical radiosurgery. Cell survival studies have been performed to verify the importance of this effect in relation to established models. Mammalian V79-4 cells were irradiated in vitro with γ-rays, either as an acute exposure in a few minutes, where the effects of sublethal irradiation damage repair over the period of exposure can be ignored, or as protracted exposures delivered over 15-120 min. Protraction was achieved either by introducing a variable time gap between two doses of 7 Gy, or as a continuous exposure at lower dose rates so that a range of doses were delivered in fixed times of 30, 60 or 120 min. For all doses there was a progressive reduction in efficacy with increasing overall treatment time. This was illustrated by the progressive increase in clonogenic cell survival with a resulting right shift of the survival curves. Cell survival curves for irradiations given either as an acute exposure (6.1 Gy/min), over fixed times (30, 60 and 120 min) or for a fixed low dose-rate (0.2 Gy/min) were well fitted by the Linear Quadratic (LQ) model giving an α/ß ratio of 4.0 Gy and a single repair half-time of 31.5 min. The present results are consistent with published data with respect to the response of solid tumors and normal tissues, whose response to both continuous and fractionated irradiation is also well described by the LQ model. This suggests the need for dose compensation in radiosurgical treatments, and other forms of radiotherapy, where dose is delivered over a similar range of protracted overall treatment times, perhaps as a prerequisite to full biological effective dose treatment planning.

TRACKING DOWN ALPHA-PARTICLES: THE DESIGN, CHARACTERISATION AND TESTING OF A SHALLOW-ANGLED ALPHA-PARTICLE IRRADIATOR.

Human exposure to α-particles from radon and other radionuclides is associated with carcinogenesis, but if well controlled and targeted to cancer cells, α-particles may be used in radiotherapy. Thus, it is important to understand the biological effects of α-particles to predict cancer risk and optimise radiotherapy. To enable studies of α-particles in cells, we developed and characterised an α-particle automated irradiation rig that allows exposures at a shallow angle (70° to the normal) of cell monolayers in a 30 mm diameter dish to complement standard perpendicular irradiations. The measured incident energy of the α-particles was 3.3 ± 0.5 MeV (LET in water = 120 keV µm-1), with a maximum incident dose rate of 1.28 ± 0.02 Gy min-1, which for a 5 µm cell monolayer corresponds to a mean dose rate of 1.57 ± 0.02 Gy min-1 and a mean LET in water of 154 keV µm-1. The feasibility of resolving radiation-induced DNA double-strand breaks (DSB) foci along the track of α-particles was demonstrated using immunofluorescent labelling with γH2AX and 53BP1 in normal MRC-5 human lung cells.

Reflections on recovery, rehabilitation and reintegration of injured service members and veterans from a bio-psychosocial-spiritual perspective

Medical interventions regarding trauma resuscitation have increased survivorship to levels not previously attained. Multiple examples from recent conflicts illustrate the potential return to high-level function of severely injured service members following medical and rehabilitative interventions. This review addresses the goals of rehabilitation, distills hard-won lessons of the last decade of military trauma and rehabilitation, and recommends the use of a bio-psychosocial-spiritual approach to care that can be applied at all tiers of the health care system. Questions on enabling participation in meaningful life activities include the following: Why do some patients do well and others do not? What elements contribute to positive outcomes? What factors relate to suboptimal results? Lessons learned revolve around the importance of considering the physical, psychosocial and spiritual aspects of a person's well-being; empowering patients by fostering self-efficacy; and helping patients find meaning in life events and set high-level goals. A bio-psychosocial-spiritual model from the rehabilitation medicine literature ­ the Canadian Model of Occupational Performance and Engagement ­ is proposed as a guide to the provision of person-centred care and the maximization of a person's functioning posttrauma.

Les interventions médicales de réanimation en traumatologie ont porté les taux de survie à des niveaux encore inégalé. Plusieurs exemples tirés de conflits récents illustrent le retour potentiel à un degré fonctionnel élevé après des interventions médicales et de réadaptation chez des membres des forces armées grièvement blessés. La présente revue expose les objectifs de la réadaptation, résume les dures leçons tirées de la dernière décennie en traumatologie et réadaptation dans le monde militaire et recommande l'utilisation d'une approche de soins bio- et psychosociospirituelle qui peut être appliquée à tous les échelons du système de soins de santé. Les questions concernant la capacité d'un retour à des activités signifiantes incluent : Pourquoi les patients n'obtiennent-ils pas tous les mêmes résultats? Quels éléments contribuent à des résultats positifs? Quels facteurs sont en lien avec des résultats optimaux? Les leçons apprises font ressortir l'importance de tenir compte des dimensions physique, psychosociale et spirituelle des personnes pour assurer leur bien-être, de les rendre autonomes en favorisant une plus grande auto-efficacité et de les aider à trouver du sens dans les événements de la vie et à se fixer des objectifs ambitieux. Un modèle bio- et psychosociospirituel tiré de la littérature en médecine de réadaptation ­ le Modèle canadien de rendement occupationnel et de participation ­ est proposé comme guide pour la prestation de soins centrés sur la personne et la maximisation de son fonctionnement après un traumatisme.

Complex DNA Damage Induced by High Linear Energy Transfer Alpha-Particles and Protons Triggers a Specific Cellular DNA Damage Response.

PURPOSE: To investigate the precise mechanism of recognition and processing of ionizing radiation (IR)-induced complex DNA damage (CDD), where two or more DNA lesions are in close proximity, in cellular DNA which is packaged with histones to form chromatin. METHODS AND MATERIALS: HeLa and oropharyngeal squamous cell carcinoma (UMSCC74A and UMSCC6) cells were irradiated with high linear energy transfer (LET) α-particles or protons, versus low-LET protons and X rays. At various time points after irradiation, site-specific histone post-translational modifications were analyzed by quantitative Western blotting; DNA damage and repair were measured by different versions of the comet assay; and cell survival was determined using clonogenic assays. RESULTS: Site-specific histone post-translational modifications after low- and high-LET radiation, particularly proton irradiation, were screened, aiming to identify those responsive to CDD. We demonstrate that histone H2B ubiquitylated on lysine 120 (H2Bub) is specifically induced several hours after irradiation in response to high-LET α-particles and protons but not by low-LET protons or X rays/γ-radiation. This is associated with increased levels of CDD, which contributes to decreased cell survival. We further discovered that modulation of H2Bub is under the control of two E3 ubiquitin ligases, MSL2 and RNF20/RNF40 complex, whose depletion leads to defective processing and further persistence of CDD, and to additional decreased cell survival after irradiation. CONCLUSION: This study demonstrates that the signaling and repair of CDD, particularly induced by high-LET IR is co-ordinated through the specific induction of H2Bub catalyzed by MSL2 and RNF20/40, a mechanism that contributes significantly to cell survival after irradiation.

Efficacy of radiosensitizing doped titania nanoparticles under hypoxia and preparation of an embolic microparticle.

The aim of this study was to develop a manufacturing protocol for large-scale production of doped titania radiosensitizing nanoparticles (NPs) to establish their activity under hypoxia and to produce a multimodal radiosensitizing embolic particle for cancer treatment. We have previously shown that radiosensitizing NPs can be synthesized from titania doped with rare earth elements, especially gadolinium. To translate this technology to the clinic, a crucial step is to find a suitable, scalable, high-throughput method. Herein, we have described the use of flame spray pyrolysis (FSP) to generate NPs from titanium and gadolinium precursors to produce titania NPs doped with 5 at% gadolinium. The NPs were fully characterized, and their capacity to act as radiosensitizers was confirmed by clonogenic assays. The integrity of the NPs in vitro was also ascertained due to the potentially adverse effects of free gadolinium in the body. The activity of the NPs was then studied under hypoxia since this is often a barrier to effective radiotherapy. In vitro radiosensitization experiments were performed with both the hypoxia mimetics deferoxamine and cobalt chloride and also under true hypoxia (oxygen concentration of 0.2%). It was shown that the radiosensitizing NPs were able to cause a significant increase in cell death even after irradiation under hypoxic conditions such as those found in tumors. Subsequently, the synthesized NPs were used to modify polystyrene embolization microparticles. The NPs were sintered to the surface of the microparticles by heating at 230°C for 15 minutes. This resulted in a good coverage of the surface and to generate embolization particles that were shown to be radiosensitizing. Such multimodal particles could therefore result in occlusion of the tumor blood vessels in conjunction with localized reactive oxygen species generation, even under hypoxic conditions such as those found in the center of tumors.

Transportation of peripheral blood progenitor cell products: effect of ambient temperature.

BACKGROUND AIMS: Peripheral blood progenitor cell (PBPC) products are often transported at high cell concentrations (>200 × 109/L) over long distances, requiring >36 h transport time. METHODS: Fresh PBPC samples from eight healthy donors were studied with two viability assays for effects of temperature outside the transport container (ambient temperature). The Coleman 5272 container, routinely used by the National Marrow Donor Program (NMDP) with two -20°C gel packs, was compared with the Coleman 6216 container, which can hold four -20°C gel packs. RESULTS: The temperature inside the smaller transport container (5272) proved to be sensitive to ambient temperature, whereas the larger container (6216) was less sensitive. The viability of CD34(+) cells, and the survival of granulocyte-macrophage colony-forming units (GM-CFU), was more dependent on the ambient temperature for the smaller than for the larger container. CONCLUSIONS: PBPC products are most often transported at approximately 2-8°C. The inside temperature of the container currently used by the NMDP appears to be more sensitive to increases in temperature when exposed to higher ambient temperature for prolonged periods of time. Increasing the number of gel packs from two to four improves the stability of the temperature inside the container but would require a different container.

Transportation of peripheral blood progenitor cell products: effects of time, temperature and cell concentration.

BACKGROUND AIMS: Peripheral blood progenitor cell (PBPC) products are often transported at high cell concentrations (>200x10(9)/L) over long distances, requiring >36 h transport time. METHODS: Fresh PBPC samples from 12 healthy donors were studied with various viability assays regarding the effects of temperature, cell concentration and duration of storage. RESULTS: Trypan blue exclusion was far less sensitive to cell damage than two-color fluorescence for CD34 and 7-AAD, and colony-forming unit-granulocyte-macrophage (CFU-GM) assays; the latter assay proved the most sensitive. All products stored at 4 degrees C maintained their viability for up to 4 days. Thus, at 96 h, recovery of viable CD34(+) cells was still 82%, and of CFU-GM 57%, even at concentrations of 200x10(9)/L. Higher storage temperatures rapidly decreased the viability, with extensive variation between donors. At room temperature 80% of viable CD34(+) cells and >90% of CFU-GM were lost after 48 h of storage at 200x10(9)/L. Lower cell concentrations allowed storage at higher temperatures: at 17 degrees C a concentration of 50x10(9)/L resulted in only 5% loss of viable CD34(+) cells after 48 h, while the loss was >30% at 200x10(9)/L. CONCLUSIONS: PBPC products should be transported at 4 degrees C. Dilution of the product may partly compensate for slightly higher temperatures. Trypan blue exclusion should be abandoned as a method for assessing viability after prolonged transportation. Proliferative assays should be used to validate transportation conditions.

Starting granulocyte-colony-stimulating factor (filgrastim) early after autologous peripheral blood progenitor cell transplantation leads to faster engraftment without increased resource utilization.

BACKGROUND: Hematopoietic growth factor support is routinely used after autologous stem cell transplantation. The optimal starting date of this growth factor support has not been established yet, but many engraftment studies now recommend the fifth day after stem cell infusion (Day 5). STUDY DESIGN AND METHODS: After switching the start date of granulocyte-colony-stimulating factor (G-CSF) support from the day of transplant (Day 0 group), to Day 5 after stem cell infusion (Day 5 group), the impression arose that there was an associated delay in engraftment of both white blood cells and platelets (PLTs). A retrospective analysis of two cohorts was performed with attention to engraftment variables and resource utilization. RESULTS: Patients in the Day 0 group recovered an absolute granulocyte count of more than 0.500 x 10(9) per L significantly earlier than patients in the Day 5 group (p < 0.001 in log-rank test; median difference, 1 day). Time to PLT recovery of more than 20 x 10(9) per L, without transfusion support, was not significantly different between the Day 0 and Day 5 groups (p = 0.16; medians of 10 and 12 days, respectively). Resource utilization, defined as number of red blood cell and PLT transfusions, days with fever or on intravenous antibiotics, days with mucositis, and length of hospital stay, were not significantly different between the two groups (p >or= 0.15 in each case). Total charges for the transplant episode were also not different between the two groups (p = 0.48). CONCLUSION: Starting G-CSF support on the day of stem cell infusion, instead of on Day +5, leads to faster hematologic recovery without a significant impact on resource utilization.

Prediction of engraftment after autologous peripheral blood progenitor cell transplantation: CD34, colony-forming unit-granulocyte-macrophage, or both?

BACKGROUND: The rate of hematologic recovery after peripheral blood progenitor cell (PBPC) transplantation is influenced by the dose of progenitor cells. Enumeration of cells that express CD34+ on their surface is the most frequently used method to determine progenitor cell dose. In vitro growth of myeloid progenitor cells (colony-forming unit-granulocyte-macrophage [CFU-GM]) requires more time and resources, but may add predictive information. STUDY DESIGN AND METHODS: A series of 323 patients, who underwent autologous PBPC transplantation for multiple myeloma, malignant lymphoma, or locally advanced breast cancer, were studied for the effect of CD34+ dose and CFU-GM dose on hematologic recovery. Measures for engraftment were days to absolute granulocyte and platelet (PLT) counts to greater than 500 per muL and than 20 x 10(9) per L, respectively, and number of PLT transfusions and red cell units required. RESULTS: The CD34+ dose had a median of 8.4 x 10(6) per kg, and the CFU-GM dose a median of 84.9 x 10(4) per kg. The CD34+ and CFU-GM doses showed significant correlation (R = 0.63; p < 0.0001) but a wide variation in the ratio of CD34+ and CFU-GM. Both CD34+ and CFU-GM doses had significant correlation with the measures of engraftment, but for all measures the relationship of CD34+ was stronger. Multivariate analysis and subgroup analysis of patients receiving CD34+ doses of less than 5 x 10(6) per kg also did not reveal an independent predictive value for CFU-GM. CONCLUSION: For prediction of hematologic recovery after autologous PBPC transplantation, determination of CFU-GM dose does not add to the predictive value of the CD34+ dose.

Delayed ABLC prophylaxis after allogeneic stem-cell transplantation.

Invasive fungal infections (IFI) are frequent causes of mortality after allogeneic stem-cell transplantation (SCT). A very important risk factor for IFI is the use of steroids. We used a risk-based chemoprevention in an open-labelled pilot study. All patients received oral fluconazole or itraconazole (200-400 mg day(-1)) during their neutropenic episode. Starting on day +30, patients receiving prednisone > or =30 mg day(-1) were switched to twice weekly Amphotericin-B-lipid-complex (ABLC) in a dose of 4 mg kg(-1). Patients receiving lower steroid doses continued on the fluconazole/itraconazole prophylaxis. Between 1999 and 2002, 100 patients were enrolled and followed for IFI for 1 year. Seven patients were started on therapeutic daily ABLC treatment before day +30 because of documented or suspected IFI; four had definite or probable aspergillosis, and two had candidaemia. Thirty patients did not need prophylactic ABLC; only one developed candidaemia. Sixty-three patients received ABLC prophylaxis for a median of 52 days (range: 1-289). Seven of these patients developed IFI; one definite and two probable cases of aspergillosis, one case of probable Trichosporon beigelii infection, and three cases of candidaemia. The twice weekly ABLC was well tolerated. This risk-based chemoprevention appears to be effective and might diminish the role of steroids as risk factor for IFI after allogeneic SCT. The relatively high incidence of early IFI suggests that additional prophylaxis for IFI may be indicated for poor-risk patients prior to day +30.

Transplantation of hematopoietic stem cells from the peripheral blood.

Hematopoietic stem cells can be collected from the peripheral blood. These hematopoietic stem cells (HSC), or better progenitor cells, are mostly expressed as the percentage of cells than react with CD34 antibodies or that form colonies in semi-solid medium (CFU-GM). Under steady-state conditions the number of HSC is much lower in peripheral blood than in bone marrow. Mobilization with chemotherapy and/or growth factors may lead to a concentration of HSC in the peripheral blood that equals or exceeds the concentration in bone marrow. Transplantation of HSC from the peripheral blood results in faster hematologic recovery than HSC from bone marrow. This decreases the risk of infection and the need for blood-product support. For autologous stem-cell transplantation (SCT), the use of peripheral blood cells has completely replaced the use of bone marrow. For allogeneic SCT, on the other hand, the situation is more complex. Since peripheral blood contains more T-lymphocytes than bone marrow, the use of HSC from the peripheral blood increases the risk of graft-versus-host disease after allogeneic SCT. For patients with goodrisk leukemia, bone marrow is still preferred, but for patients with high-risk disease, peripheral blood SCT has become the therapy of choice.

Hypereosinophilic syndrome: long-term remission following allogeneic stem cell transplant in spite of transient eosinophilia post-transplant.

A 38-year-old male with progressive myeloproliferative variant of hypereosinophilic syndrome (HES) underwent allogeneic bone marrow transplantation from a matched unrelated donor. The preparative regimen consisted of TBI, cytarabine, and cyclophosphamide. The graft was T-cell-depleted. The patient had slow, but complete, hematologic recovery, and all cells were shown by VNTR analysis to be of donor origin. Five months after transplant, the patient developed prominent eosinophilia (peak 4.1 x 10(9)/L) with dermatographism and very high IL-5 levels. Eosinophils isolated to purity by cell sorting were all of donor origin. Mild increase in immunosuppression led to a normalization of eosinophil count after about 6 months. The patient is now 6 years after transplant, off all medications, and without evidence of disease. Allogeneic stem-cell transplantation is a potentially curative therapy for HES.

Peripheral blood progenitor cell transplantation.

Peripheral blood progenitor cells (PBPCs) have become increasingly popular over the last 15 years as the source of hematopoietic stem cells for transplantation. In the early 1990s, PBPCs replaced bone marrow (BM) as the preferred source of autologous stem cells, and recently the same phenomenon is seen in the allogeneic setting. Under steady-state conditions, the concentration of PBPCs (as defined by CFU-GM and/or CD34+ cells) is very low, and techniques were developed to increase markedly this concentration. Such mobilization techniques include daily injections of filgrastim (G-CSF) or a combination of chemotherapy and growth factors. Leukapheresis procedures allow the collection of large numbers of circulating white blood cells (and PBPCs). One or two leukapheresis procedures are often sufficient to obtain the minimum number of CD34+ cells considered necessary for prompt and consistent engraftment (i.e., 2.5-5.0 x 10(6)/kg). As compared to BM, autologous transplants with PBPCs lead to faster hematologic recovery and have few, if any, disadvantages. In the allogeneic arena, PBPCs also result in faster engraftment, but at a somewhat higher cost of chronic graft-versus-host disease (GvHD). This may be a double-edged sword leading to both increased graft-versus-tumor effects and increased morbidity. The rapid advances in the study of hematopoietic, and even earlier, stem cells will continue to shape the future of PBPC transplantation.