Cognitive change and neuroimaging following immunoablative therapy and hematopoietic stem cell transplantation in multiple sclerosis: A pilot study.

BACKGROUND: Individuals with MS undergoing immunoablative therapy and hematopoietic stem cell transplantation (HSCT) show substantial decrease in brain volume over 2.4 months, presumably from chemotoxic effects, although other mechanisms have also been postulated. OBJECTIVE: We examined whether volume loss was accompanied by a concomitant decrease in cognition. White and gray matter volumes, and the effect of stem cell dosage were considered. METHODS: Seven individuals with rapidly progressing MS and poor prognosis underwent high dose immunosuppression and autologous HSCT. Neuropsychological testing and MRI scans were performed at baseline, 2 and 24 months post-procedure. RESULTS: Cognitive impairment was noted at all times in most participants. Median decline of 1.39% in total brain volume was noted 2 months post-HSCT. By 24 months a further decline of 1.65% was noted. At 2 months significant decline was observed for areas of executive functioning. At 24 months almost no significant declines were noted. No significant correlations were found between cognitive decline and change in imaging variables or stem cell dosage. CONCLUSIONS: Cognition changed in the early period following treatment but with little apparent relationship to volume changes. With temporal distance from the HSCT procedure, cognition returned to baseline levels. With the caution of a very small sample, preliminary results suggest that immunoablation and HSCT may have no lasting deleterious effects on cognition.

Non-replicating rhabdovirus-derived particles (NRRPs) eradicate acute leukemia by direct cytolysis and induction of antitumor immunity.

Rhabdoviruses (RVs) are currently being pursued as anticancer therapeutics for various tumor types, notably leukemia. However, modest virion production and limited spread between noncontiguous circulating leukemic cells requires high-dose administration of RVs, which exceeds the maximum tolerable dose of the live virus. Furthermore, in severely immunosuppressed leukemic patients, the potential for uncontrolled live virus spread may compromise the safety of a live virus approach. We hypothesized that the barriers to oncolytic virotherapy in liquid tumors may be overcome by administration of high-dose non-replicating RVs. We have developed a method to produce unique high-titer bioactive yet non-replicating rhabdovirus-derived particles (NRRPs). This novel biopharmaceutical is multimodal possessing direct cytolytic and immunomodulatory activity against acute leukemia. We demonstrate that NRRP resistance in normal cells is mediated by intact antiviral defences including interferon (IFN). This data was substantiated using murine models of blast crisis. The translational promise of NRRPs was demonstrated in clinical samples obtained from patients with high-burden multidrug-resistant acute myeloid leukemia. This is the first successful attempt to eradicate disseminated cancer using a non-replicating virus-derived agent, representing a paradigm shift in our understanding of oncolytic virus-based therapies and their application toward the treatment of acute leukemia.

Identification of a role for the nuclear receptor EAR-2 in the maintenance of clonogenic status within the leukemia cell hierarchy.

Identification of genes that regulate clonogenicity of acute myelogenous leukemia (AML) cells is hindered by the difficulty of isolating pure populations of cells with defined proliferative abilities. By analyzing the growth of clonal siblings in low passage cultures of the cell line OCI/AML4 we resolved this heterogeneous population into strata of distinct clonogenic potential, permitting analysis of the transcriptional signature of single cells with defined proliferative abilities. By microarray analysis we showed that the expression of the orphan nuclear receptor EAR-2 (NR2F6) is greater in leukemia cells with extensive proliferative capacity than in those that have lost proliferative ability. EAR-2 is expressed highly in long-term hematopoietic stem cells, relative to short-term hematopoietic stem and progenitor cells, and is downregulated in AML cells after induction of differentiation. Exogenous expression of EAR-2 increased the growth of U937 cells and prevented the proliferative arrest associated with terminal differentiation, and blocked differentiation of U937 and 32Dcl3 cells. Conversely, silencing of EAR-2 by short-hairpin RNA initiated terminal differentiation of these cell lines. These data identify EAR-2 as an important factor in the regulation of clonogenicity and differentiation, and establish that analysis of clonal siblings allows the elucidation of differences in gene expression within the AML hierarchy.

Voxel-based analysis of the evolution of magnetization transfer ratio to quantify remyelination and demyelination with histopathological validation in a multiple sclerosis lesion.

We present a new method for advanced image processing to separately quantify significant decreases and increases in the magnetization transfer ratio (MTR) of individual voxels of MS lesions as markers of demyelination and remyelination. We used this method to analyze the evolution of MTR in individual voxels of an acute, Gadolinium (Gd)-enhancing lesion that was available for pathology. Over 6.5 months following enhancement, MTR was low and stable in the lesion center (81% of the initially Gd-enhancing lesion volume (GdLV)) and MTR increased at the lesion border with normal-appearing white matter (14%GdLV). The estimated error of these measurements was less than 1.8%GdLV based on scan/rescan analysis. Histopathological analysis confirmed a demyelinated lesion centre with diffuse presence of macrophages/microglia and marked loss of oligodendrocytes and a partially remyelinated lesion border with diffuse presence of macrophages/microglia and relatively more oligodendrocytes compared to the lesion centre. The correlation of imaging and histopathological findings support the validity and sensitivity of our method of voxel-based MTR image processing for monitoring demyelination and remyelination in vivo.

Brain atrophy after immunoablation and stem cell transplantation in multiple sclerosis.

The authors measured brain atrophy in nine patients undergoing immunoablation and autologous hematopoietic stem cell transplantation for multiple sclerosis. From baseline to 1 month after treatment, atrophy was 10 times faster than before treatment. A patient with non-CNS lymphoma showed comparable acute brain atrophy after analogous therapy. These observations suggest that brain atrophy after immunoablation may not be due entirely to the resolution of edema but may be related to chemotoxicity.

Multiple sclerosis conference synopsis and discussion: cellular therapy for treatment of autoimmune diseases (October 2005).

At a conference held in October 2005, participants presented studies on high dose immunosuppression with hematopoietic cell transplant (HCT) for multiple sclerosis (MS), including neuroimmunological and magnetic resonance imaging (MRI) mechanistic approaches, clinical registry reports, and ongoing or newly-designed protocols. A discussion panel considered questions on how to define success, timing of controlled clinical trials, difficulty in patient recruitment, and future direction of high dose therapy.

Local magnetization transfer ratio signal inhomogeneity is related to subsequent change in MTR in lesions and normal-appearing white-matter of multiple sclerosis patients.

Multiple sclerosis (MS) lesions show differing degrees of demyelination and remyelination. Changes in myelin content are associated with changes in magnetization transfer on MRI. Since acute inflammation and demyelination are spatially and temporally inhomogeneous, we hypothesized that local magnetic transfer ratio (MTR) heterogeneity might be predictive of subsequent changes in MTR. To test this hypothesis, we analyzed MTR images obtained in 14 subjects, at baseline and after 2 months follow-up. We segmented lesions and normal-appearing white-matter (NAWM), calculated MTR signal inhomogeneity maps at baseline and MTR lesion difference maps between baseline and follow-up. We found that regions with low MTR inhomogeneity at baseline experienced little further change in MTR on follow-up. The mean change in lesion MTR between baseline and follow-up was 0.10 +/- 3.70; in NAWM it was -0.09 +/- 2.02. We found that regions with high MTR inhomogeneity at baseline would change MTR on follow-up: (1) voxels with significantly high MTR in regions of high MTR inhomogeneity at baseline showed a mean decrease in MTR between baseline and follow-up of -2.51 +/- 4.68 in lesions and -1.41 +/- 3.00 in NAWM; (2) voxels with low MTR in regions of high MTR inhomogeneity at baseline showed a mean increase in MTR between baseline and follow-up of 2.61 +/- 6.07 in lesions. These changes in MTR were significantly different (P < 0.001). These results suggest that calculation of MTR signal inhomogeneity may provide a method for quantifying the potential for remyelination and demyelination, and thus could provide an important MRI biomarker for assessing the efficacy of therapies targeting remyelination.

MIRD Pamphlet No. 15: Radionuclide S values in a revised dosimetric model of the adult head and brain. Medical Internal Radiation Dose.

UNLABELLED: Current dosimetric models of the brain and head lack the anatomic detail needed to provide the physical data necessary for suborgan brain dosimetry. During the last decade, several new radiopharmaceuticals have been introduced for brain imaging. The marked differences of these tracers in tissue specificity within the brain and their increasing use for diagnostic studies support the need for a more anthropomorphic model of the human brain and head for use in estimating regional absorbed dose within the brain and its adjacent structures. METHODS: A new brain model has been developed that includes eight subregions: the caudate nuclei, the cerebellum, the cerebral cortex, the lateral ventricles, the lentiform nuclei, the thalami, the third ventricle and the white matter. This brain model is incorporated within a total revision of the head model presented in MIRD Pamphlet No. 5 Revised. Modifications include the addition of the eyes, the teeth, the mandible, an upper facial region, a neck region and the cerebrospinal fluid within both the cranial and spinal regions. RESULTS: Absorbed fractions of energy for photon and electron sources located in 14 source regions within the new model were calculated using the EGS4 Monte Carlo radiation transport code for particles in the energy range 10 keV-4 MeV. These absorbed fractions were then used along with radionuclide decay data to generate S values for 24 radionuclides that are used in clinical or investigational studies of the brain, 12 radionuclides that localize within the cranium and spinal skeleton and 12 radionuclides that selectively localize in the thyroid gland. CONCLUSION: A substantial revision to the dosimetric model of the adult head and brain originally published in MIRD Pamphlet No. 5 Revised is presented. This revision supports suborgan brain dosimetry for a variety of radiopharmaceuticals used in neuroimaging. Dose calculations for the neuroimaging agent 1231-tropane provide an example of the new model and yield mean brain doses that are consistent with published values. However, the absorbed dose to subregions within the brain such as the caudate and lentiform nuclei may exceed the average brain dose by a factor of up to 5.

Characterization of transgenic mice with targeted disruption of the catalytic domain of the double-stranded RNA-dependent protein kinase, PKR.

The interferon-inducible, double-stranded RNA-dependent protein kinase PKR has been implicated in anti-viral, anti-tumor, and apoptotic responses. Others have attempted to examine the requirement of PKR in these roles by targeted disruption at the amino terminal-encoding region of the Pkr gene. By using a strategy that aims at disruption of the catalytic domain of PKR, we have generated mice that are genetically ablated for functional PKR. Similar to the other mouse model of Pkr disruption, we have observed no consequences of loss of PKR on tumor suppression. Anti-viral response to influenza and vaccinia also appeared to be normal in mice and in cells lacking PKR. Cytokine signaling in the type I interferon pathway is normal but may be compromised in the erythropoietin pathway in erythroid bone marrow precursors. Contrary to the amino-terminal targeted Pkr mouse, tumor necrosis factor alpha-induced apoptosis and the anti-viral apoptosis response to influenza is not impaired in catalytic domain-targeted Pkr-null cells. The observation of intact eukaryotic initiation factor-2alpha phosphorylation in these Pkr-null cells provides proof of rescue by another eukaryotic initiation factor-2alpha kinase(s).

Identification of sequence-tagged transcripts differentially expressed within the human hematopoietic hierarchy.

Hematopoiesis is regulated by a complex gene expression program. To gain further insight into the molecular mechanisms underlying this process in humans, we sampled the transcriptional activity of the CD34+ hematopoietic progenitor line KG1a by single-pass sequencing the 5' ends of 1018 clones from a unidirectional cDNA library. Searches of public databases with the resulting expressed sequence tags (ESTs) identified 101 clones that showed no sequence similarity to any of the existing entries and that were therefore considered to derive from previously undescribed genes. Of the remaining 917 ESTs, 553 (a total of 485 distinct transcripts) corresponded to known genes. A further 279 KG1a ESTs matched or exhibited sequence similarity to ESTs or genomic sequences from humans and other species. Among the latter were putative human orthologs of developmental and cell cycle control genes from Caenorhabditis elegans, Drosophila, and yeast, as well as genes whose predicted amino acid sequences showed similarity to mammalian transcription factors. Hybridization of selected novel KG1a ESTs to globally amplified cDNAs prepared from single primary human hematopoietic precursors and homogeneous populations of terminally maturing hematopoietic cells revealed transcripts that are expressed preferentially at a specific stage or in a particular lineage within the hematopoietic hierarchy. Thus, included in the KG1a EST dataset are candidates for new human genes that may play roles in hematopoietic differentiative progression and lineage commitment.

Treatment of metastatic bone pain with tin-117m Stannic diethylenetriaminepentaacetic acid: a phase I/II clinical study.

The physical characteristics of Sn-117m combined with the biodistribution of the compound tin-117m (Stannic, 4+) diethylenetriaminepentaacetic acid (Sn-117m DTPA) suggest that it should be an excellent agent for the palliation of pain from bony metastases. Prior work has established the dosimetry and the safety for the material in human beings. The presence of low-energy conversion electrons should result in the relative sparing of the bone marrow while delivering a high radiation dose to sites of bony metastatic disease. Forty-seven patients with painful bone metastases from various malignancies were treated with Sn-117m DTPA. The patients were assigned to five different dose levels ranging from 2.64 to 10.58 MBq (71-286 microCi) per kg of body weight. Follow-up included review of pain diaries, performance scores, analgesic requirements, blood chemistries, and hematological assessment. Three patients received a second treatment. There was an overall response rate for relief of pain of 75% (range, 60-83%) in the 40 treatments that could be evaluated. No correlation was apparent in this limited series between response rate and the five dose levels used. The relief was complete in 12 patients (30%). The time to onset of pain relief was 19 +/- 15 days with doses < or = 5.29 MBq/kg and 5 +/- 3 days with doses > or = 6.61 MBq/kg. Myelotoxicity was minimal, with only one patient having a marginal grade 3 WBC toxicity. On the basis of our data, Sn-117m DTPA should be an effective and safe radiopharmaceutical for palliation of painful bony metastases. A large-scale trial is warranted to evaluate it in comparison to other similar agents.

Radiopharmaceuticals for bone malignancy therapy.

OBJECTIVE: This continuing education article reviews radionuclide bone therapy agents that are available commercially and introduces agents that are being evaluated for future use. Currently these agents are used to provide pain palliation from metastases to bone. Future applications may include adjuvant therapy to surgery or external beam treatment. After reading this paper, the reader should be able to: (a) describe the desirable characteristics of radionuclide bone therapy agents; (b) compare and contrast radiopharmaceuticals available for bone therapy; and (c) state the clinical applications of radionuclide bone therapy agents.

Overview of nuclides for bone pain palliation.

A variety of radiopharmaceuticals has been used for systemic therapy to relieve pain from malignancies metastatic to bone, using electron emitting radionuclides either in ionic form or as labels for bone seeking compounds to irradiate locally at sites of metastases. The major complication comes from the absorbed dose to the bone marrow. Therefore, there has been a search for radionuclides with lower energy emissions and correspondingly shorter range in tissue. Some studies have shown that it is possible to delay the onset of new pain sites and perhaps increase life expectancy.

Impaired permeability in radiation-induced lung injury detected by technetium-99m-DTPA lung clearance.

UNLABELLED: This study evaluates the use of the 99mTc-DTPA aerosol lung clearance method to investigate radiation-induced lung changes in eight patients undergoing radiotherapy for lung or breast carcinoma. The sensitivity of the method was compared with chest radiography for detecting radiation-induced changes in the lung, regional alterations within (irradiated region) and outside (shielded region) the treatment ports, effect of irradiated lung volume, and dependence on time after radiotherapy. METHODS: Serial DTPA lung clearance studies were performed before the first radiation treatment (baseline), then weekly during a 5- to 7-wk course, and up to 12 times post-therapy over periods of 56-574 days. The total activity deposited in the lungs for each study was approximately 150 microCi (approximately 5.6 MBq). DTPA clearance, expressed in terms of the biological half-time, t 1/2, was computed from the slopes of the least-squares fit regression lines of the time-activity curves for the first 10 min for irradiated and shielded lung regions. RESULTS: Major findings include: (a) significant and early DTPA t 1/2 changes were observed in all patients during and after radiotherapy; (b) changes in DTPA t 1/2 values were observed in both irradiated and shielded lung regions in all patients suggesting a radiation-induced systemic reaction; (c) changes in DTPA t 1/2 values were correlated (p < 0.05) with the irradiated lung volumes; (d) significantly reduced DTPA t 1/2 values were observed in three patients who subsequently presented with clinical symptoms and/or radiographic changes consistent with radiation pneumonitis (t1/2 felt to 19% +/- 6% of baseline values, compared with 64% +/- 17% in the remaining patients [p < 0.01]); (e) the onset of decreased DTPA t 1/2 values in these three patients occurred 35-84 days before clinical symptoms and/or radiographic changes; and (f) DTPA t 1/2 tended to approach baseline values with time after radiotherapy, suggesting a long-term recovery in lung injury. CONCLUSION: These observations show significant and early alterations in DTPA lung clearance during and after radiotherapy that may provide a sensitive assay to monitor changes in radiation-induced lung injury and may facilitate early therapeutic intervention.

Tin-117m(4+)DTPA: pharmacokinetics and imaging characteristics in patients with metastatic bone pain.

UNLABELLED: Biokinetics and imaging characteristics of 117mSn(4+)DTPA have been studied in patients with metastatic bone pain. METHODS: Seventeen patients with bone pain due to metastasis were given three dose levels: 180 microCi/kg (6.66 MBq/kg), 229 microCi/kg (8.47 MBq/kg) and 285 microCi/kg (10.55 MBq/kg) body weight. Periodic blood and daily urine samples were collected for 14 days to measure percent injected activity retained in blood and that excreted in urine. Simultaneous anterior and posterior view whole-body images were obtained under identical scan settings at 1, 3.5 and 24 hr and on Days 3 and 7 and between 4-6 and 8-10 wk postinjection. The total body retention was calculated using the geometric mean counts. RESULTS: After intravenous injection, the total body clearance of 117mSn(4+)DTPA shows two components: a soft-tissue component and a bone component. The soft-tissue component accounts for 22.4% of the dose and consists of four subcomponents with an average biologic clearance half-time of 1.45 days (range 0.1-3.2 days). The bone component accounting for the remaining 77.6% of the dose shows no biologic clearance. A mean 22.4% of the dose is excreted in urine in 14 days; 11.4% within 24 hr. The uptake pattern appears similar to that of 99mTc-MDP. Peak uptake is observed in normal bone by 24 hr and metastatic lesions by 3-7 days. Pain palliation was observed with all three doses levels. CONCLUSION: Among the four potential bone pain palliation radionuclides, 117mSn(4+)DTPA demonstrates the highest bone uptake and retention. Some biokinetic and radionuclidic features of 117mSn(4+)DTPA are similar to other agents, but many features are different and unique and may make it an ideal bone pain palliation agent. Double-blind comparative studies are needed to determine its exact role in bone pain palliation.

Does detoxification reverse the acute lung injury of crack smokers?

The effect on chronic crack users of a 3 month detoxification programme on lung clearance of inhaled 99Tcm-diethylenetriamine pentaacetate (99Tcm-DTPA) aerosol, spirometry and gas exchange was determined in a controlled in-patient clinical treatment setting. Imaging studies were carried out in eight chronic crack users (four crack-only and four crack plus tobacco) before and after the successful completion of the detoxification programme to measure the clearance of inhaled 99Tcm-DTPA from the lungs, an index of lung epithelial permeability. 99Tcm-DTPA lung clearance, expressed in terms of the biological half-time, T1/2, was determined from the slopes of the least-squares fit regression lines of the respective time-activity plots. The mean (+/- S.D.) global T1/2 values of the crack-only (75 +/- 39 min) and crack plus tobacco users (22 +/- 10 min) were significantly shorter (P < 0.02 and P < 0.001, respectively) than from the lungs of the non-smoking controls (124 +/- 29 min). This was consistent with increased lung epithelial permeability secondary to crack-related lung injury. The mean global T1/2 value of the crack plus tobacco users was significantly shorter (P < 0.05) than that of the crack-only users. After detoxification, the abnormally rapid lung clearance became normal in two of the four crack-only users studied, improved in a third and remained unchanged in the fourth, a subject whose T1/2 value was already normal initially. However, lung clearance improved in only one of the four crack plus tobacco users studied. Faster 99Tcm-DTPA clearance was the only impairment found in seven of the eight crack users, the eighth having restrictive lung disease. Crack-related lung injury, reflected by abnormally rapid 99Tcm-DTPA lung clearance, may be at least partially reversible after a 3 month period of abstinence from crack.

Radiolabeled bone-seeking radiopharmaceuticals.

Bone seeking radiopharmaceuticals consist of diagnostic (primarily single photon emitters) and therapeutic agents. The therapeutic radiopharmaceuticals are utilized on the basis of their particulate emissions (primarily beta-) and thus are treated differently than the single photon bone imaging agents. Lately, the therapeutic bone seekers have attained increasing importance due to their potential role in alleviating pain from osseous metastases in cancer patients. However, there seems to be a paucity of published data on the pharmacokinetics of most of these agents. This paper will briefly review and summarize the presently available pharmacokinetic information on the various therapeutic bone seeking radiopharmaceuticals. Bone imaging agents based on single photon emitters will not be covered since they have been extensively discussed in the published literature.

A revised dosimetric model of the adult head and brain.

UNLABELLED: During the last decade, several new radiopharmaceuticals have been introduced for brain imaging. The marked differences of these tracers in tissue specificity within the brain and their increasing use for diagnostic studies support the need for a more anthropomorphic model of the human brain and head. Brain and head models developed in the past have comprised only simplistic representations of this anatomic region. METHODS: A new brain model has been developed which includes eight subregions: the caudate nucleus, the cerebellum, the cerebral cortex, the lateral ventricles, the lentiform nucleus, the thalamus, the third ventricle and the white matter. This brain model has been included within a slightly modified version of the head model developed by Poston et al. in 1984. The head model, which includes both the thyroid and eyes, was modified in this work to include the cerebrospinal fluid within the cranial and spinal regions. RESULTS: Absorbed fractions of energy for photon and electron sources located in thirteen source regions within the new head model were calculated using the EGS4 Monte Carlo radiation transport code for radiations in the energy range 10 keV to 4 MeV. CONCLUSION: S-values were calculated for five radionuclides used in brain imaging (11C, 15O, 18F, 99(m)Tc and 123I) and for three radionuclides showing selective uptake in the thyroid (99(m)Tc, 123I, and 131I). S-values were calculated using 100 discrete energy points in the beta-emission spectrum of the different radionuclides.