Clinical and molecular determinants of PSA response to bipolar androgen therapy in prostate cancer.

BACKGROUND: Bipolar androgen therapy (BAT) is a novel therapy known to be effective in a subset of men with metastatic castrate resistant prostate cancer (mCRPC). A better understanding of responders and nonresponders to BAT would be useful to clinicians considering BAT therapy for patients. Herein we analyze clinical and genetic factors in responders/nonresponders to better refine our understanding regarding which patients benefit from this innovative therapy. METHODS: mCRPC patients were assessed for response or no response to BAT. Patients with PSA declines of greater than 50% from baseline after 2 or more doses of testosterone were considered to be responders. Whereas, nonresponders had no PSA decline after 2 doses of testosterone and subsequently manifest a PSA increase of >50%. Differences between these two groups of patients were analyzed using clinical and laboratory parameters. All patients underwent genomic testing using circulating tumor DNA (ctDNA) and germline testing pre-BAT. RESULTS: Twenty five patients were nonresponders and 16 were responders. Baseline characteristics between nonresponders and responders varied. Responders were more likely to have had a radical prostatectomy as definitive therapy and were more likely to have been treated with an androgen receptor (AR) antagonist (enzalutamide or apalutamide) immediately before BAT (compared to abiraterone). Duration of prior enzalutamide therapy was longer in responders. Nonresponders were more likely to have bone-only metastases and responders were more likely to have nodal metastases. Assays detected ctDNA AR amplifications more often in responding patients. Responders trended toward having the presence of more TP53 mutations at baseline. CONCLUSIONS: BAT responders are distinct from nonresponders in several ways however each of these distinctions are imperfect. Patterns of metastatic disease, prior therapies, duration of prior therapies, and genomics each contribute to an understanding of patients that will or will not respond. Additional studies are needed to refine the parameters that clinicians can utilize before choosing among the numerous treatment alternatives available for CRPC patients.

FDA expedited approval and implications for rational formulary and health plan design.

DISCLOSURES: No funding supported this commentary. The authors are employed by Humana, Inc. Shrank reports board of directors work for GetWell Network and NCQA. The other authors have nothing to disclose.

MYC Promotes Bone Marrow Stem Cell Dysfunction in Fanconi Anemia.

Bone marrow failure (BMF) in Fanconi anemia (FA) patients results from dysfunctional hematopoietic stem and progenitor cells (HSPCs). To identify determinants of BMF, we performed single-cell transcriptome profiling of primary HSPCs from FA patients. In addition to overexpression of p53 and TGF-ß pathway genes, we identified high levels of MYC expression. We correspondingly observed coexistence of distinct HSPC subpopulations expressing high levels of TP53 or MYC in FA bone marrow (BM). Inhibiting MYC expression with the BET bromodomain inhibitor (+)-JQ1 reduced the clonogenic potential of FA patient HSPCs but rescued physiological and genotoxic stress in HSPCs from FA mice, showing that MYC promotes proliferation while increasing DNA damage. MYC-high HSPCs showed significant downregulation of cell adhesion genes, consistent with enhanced egress of FA HSPCs from bone marrow to peripheral blood. We speculate that MYC overexpression impairs HSPC function in FA patients and contributes to exhaustion in FA bone marrow.

Extrahepatic deficiency of transferrin receptor 2 is associated with increased erythropoiesis independent of iron overload.

Transferrin receptor 2 (TFR2) is a transmembrane protein expressed mainly in hepatocytes and in developing erythroid cells and is an important focal point in systemic iron regulation. Loss of TFR2 function results in a rare form of the iron-overload disease hereditary hemochromatosis. Although TFR2 in the liver has been shown to be important for regulating iron homeostasis in the body, TFR2's function in erythroid progenitors remains controversial. In this report, we analyzed TFR2-deficient mice in the presence or absence of iron overload to distinguish between the effects caused by a high iron load and those caused by loss of TFR2 function. Analysis of bone marrow from TFR2-deficient mice revealed a reduction in the early burst-forming unit-erythroid and an expansion of late-stage erythroblasts that was independent of iron overload. Spleens of TFR2-deficient mice displayed an increase in colony-forming unit-erythroid progenitors and in all erythroblast populations regardless of iron overload. This expansion of the erythroid compartment coincided with increased erythroferrone (ERFE) expression and serum erythropoietin (EPO) levels. Rescue of hepatic TFR2 expression normalized hepcidin expression and the total cell count of the bone marrow and spleen, but it had no effect on erythroid progenitor frequency. On the basis of these results, we propose a model of TFR2's function in murine erythropoiesis, indicating that deficiency in this receptor is associated with increased erythroid development and expression of EPO and ERFE in extrahepatic tissues independent of TFR's role in the liver.

Catheter ablation for failed surgical maze: comparison of cut and sew vs. non-cut and sew maze.

PURPOSE: To compare findings in patients undergoing atrial fibrillation(AF) and/or atrial flutter(AFl) ablation after failed cut and sew (CS) vs. non-cut and sew (NCS) surgical maze. METHODS: We compared 10 patients with prior CS to 25 with prior NCS maze undergoing catheter ablation after failed maze. RESULTS: Patient demographics: Age 68.3 ± 8.7 CS vs. 68.2 ± 9.2 NCS(P = 0.977), male 70% CS vs. 72% NCS(P = 1.000), LA size 5.11 ± 0.60 cm CS vs. 4.54 ± 0.92 cm NCS(P = 0.096), sternotomy 100% CS vs. 64% of NCS(P = 0.036). Concomitant heart surgery in 100% CS and 68% NCS(P = 0.073). NCS used radiofrequency 84%, cryoablation 8%, microwave 4%, and ultrasound 4%. All maze operations targeted pulmonary vein (PV) isolation. The maze also targeted the mitral isthmus 100% CS vs. 36% NCS(P = 0.001) and the tricuspid isthmus 90% CS vs. 40% NCS (P = 0.018). Maze failure arrhythmia mechanism was AF 0% CS and 56% NCS (P = 0.0006). Nine CS pts failed for AFl and 1 for RA tachycardia. For NCS pts, 11 failed for AFl. CS isolated 94% of PVs and NCS isolated only 26% of PVs (P < 0.0005). At EPS, clinical and induced arrhythmias were ablated and non-isolated PVs were isolated. After final ablation, arrhythmia-free rates were 60% for CS and 52% for NCS (P = 0.723) after 2.99 ± 2.35 years. CONCLUSIONS: After failed surgical maze, CS isolated nearly all PVs and NCS never isolated all PVs and the clinical rhythm was more frequently AF for NCS and AFl for CS. CS remains the surgical gold standard for durable PV isolation.

LMTK3 is essential for oncogenic KIT expression in KIT-mutant GIST and melanoma.

Certain cancers, including gastrointestinal stromal tumor (GIST) and subsets of melanoma, are caused by somatic KIT mutations that result in KIT receptor tyrosine kinase constitutive activity, which drives proliferation. The treatment of KIT-mutant GIST has been revolutionized with the advent of KIT-directed cancer therapies. KIT tyrosine kinase inhibitors (TKI) are superior to conventional chemotherapy in their ability to control advanced KIT-mutant disease. However, these therapies have a limited duration of activity due to drug-resistant secondary KIT mutations that arise (or that are selected for) during KIT TKI treatment. To overcome the problem of KIT TKI resistance, we sought to identify novel therapeutic targets in KIT-mutant GIST and melanoma cells using a human tyrosine kinome siRNA screen. From this screen, we identified lemur tyrosine kinase 3 (LMTK3) and herein describe its role as a novel KIT regulator in KIT-mutant GIST and melanoma cells. We find that LMTK3 regulated the translation rate of KIT, such that loss of LMTK3 reduced total KIT, and thus KIT downstream signaling in cancer cells. Silencing of LMTK3 decreased cell viability and increased cell death in KIT-dependent, but not KIT-independent GIST and melanoma cell lines. Notably, LMTK3 silencing reduced viability of all KIT-mutant cell lines tested, even those with drug-resistant KIT secondary mutations. Furthermore, targeting of LMTK3 with siRNA delayed KIT-dependent GIST growth in a xenograft model. Our data suggest the potential of LMTK3 as a target for treatment of patients with KIT-mutant cancer, particularly after failure of KIT TKIs.

Atrial fibrillation ablation using very short duration 50 W ablations and contact force sensing catheters.

PURPOSE: The optimal radiofrequency (RF) power and lesion duration using contact force (CF) sensing catheters for atrial fibrillation (AF) ablation are unknown. We evaluate 50 W RF power for very short durations using CF sensing catheters during AF ablation. METHODS: We evaluated 51 patients with paroxysmal (n = 20) or persistent (n = 31) AF undergoing initial RF ablation. RESULTS: A total of 3961 50 W RF lesions were given (average 77.6 ± 19.1/patient) for an average duration of only 11.2 ± 3.7 s. As CF increased from < 10 to > 40 g, the RF application duration decreased from 13.7 ± 4.4 to 8.6 ± 2.5 s (p < 0.0005). Impedance drops occurred in all ablations, and for patients in sinus rhythm, there was loss of pacing capture during RF delivery suggesting lesion creation. Only 3% of the ablation lesions were at < 5 g and 1% at > 40 g of force. As CF increased, the force time integral (FTI) increased from 47 ± 24 to 376 ± 102 gs (p < 0.0005) and the lesion index (LSI) increased from 4.10 ± 0.51 to 7.63 ± 0.50 (p < 0.0005). Both procedure time (101 ± 19.7 min) and total RF energy time (895 ± 258 s) were very short. For paroxysmal AF, the single procedure freedom from AF was 86% at 1 and 2 years. For persistent AF, it was 83% at 1 year and 72% at 2 years. There were no complications. CONCLUSIONS: Short duration 50 W ablations using CF sensing catheters are safe and result in excellent long-term freedom from AF for both paroxysmal and persistent AF with short procedure times and small amounts of total RF energy delivery.

The tumor suppressor phosphatase PP2A-B56α regulates stemness and promotes the initiation of malignancies in a novel murine model.

Protein phosphatase 2A (PP2A) is a ubiquitously expressed Serine-Threonine phosphatase mediating 30-50% of protein phosphatase activity. PP2A functions as a heterotrimeric complex, with the B subunits directing target specificity to regulate the activity of many key pathways that control cellular phenotypes. PP2A-B56α has been shown to play a tumor suppressor role and to negatively control c-MYC stability and activity. Loss of B56α promotes cellular transformation, likely at least in part through its regulation of c-MYC. Here we report generation of a B56α hypomorph mouse with very low B56α expression that we used to study the physiologic activity of the PP2A-B56α phosphatase. The predominant phenotype we observed in mice with B56α deficiency in the whole body was spontaneous skin lesion formation with hyperproliferation of the epidermis, hair follicles and sebaceous glands. Increased levels of c-MYC phosphorylation on Serine62 and c-MYC activity were observed in the skin lesions of the B56αhm/hm mice. B56α deficiency was found to increase the number of skin stem cells, and consistent with this, papilloma initiation was accelerated in a carcinogenesis model. Further analysis of additional tissues revealed increased inflammation in spleen, liver, lung, and intestinal lymph nodes as well as in the skin lesions, resembling elevated extramedullary hematopoiesis phenotypes in the B56αhm/hm mice. We also observed an increase in the clonogenicity of bone marrow stem cells in B56αhm/hm mice. Overall, this model suggests that B56α is important for stem cells to maintain homeostasis and that B56α loss leading to increased activity of important oncogenes, including c-MYC, can result in aberrant cell growth and increased stem cells that can contribute to the initiation of malignancy.

Impact of obesity on atrial fibrillation ablation: Patient characteristics, long-term outcomes, and complications.

BACKGROUND: There is an association between obesity and atrial fibrillation (AF). The impact of obesity on AF ablation procedures is unclear. OBJECTIVE: The purpose of this study was to evaluate the influence of body mass index (BMI) on patient characteristics, long-term ablation outcomes, and procedural complications. METHODS: We evaluated 2715 patients undergoing 3742 AF ablation procedures. BMI was ≥30 kg/m2 in 1058 (39%) and ≥40 kg/m2 in 129 (4.8%). Patients were grouped by BMI ranges (<25, 25-<30, 30-<35, 35-<40, and ≥40 kg/m2). RESULTS: As BMI increased from <25 to ≥40 kg/m2, age decreased from 65.3 ± 11.2 to 61.2 ± 9.2 years (P < .001), left atrial size increased from 3.91 ± 0.68 to 4.72 ± 0.62 cm (P < .005), and CHADS2 scores increased from 1.24 ± 1.10 to 1.62 ± 1.09 (P < .001). As BMI increased, paroxysmal AF decreased from 48.0% to 16.3% (P < .0001) and there was an increase in dilated cardiomyopathy (from 7.6% to 12.4%; P < .0001), hypertension (from 41.0% to 72.9%; P < .0001), diabetes (from 4.3% to 23.3%; P < .0001), and sleep apnea (from 7.0% to 46.9%; P < .0001). For the entire cohort, for BMI ≥35 kg/m2 the 5-year ablation freedom from AF decreased from 67%-72% to 57% (P = .036). For paroxysmal AF, when BMI was ≥40 kg/m2 ablation success decreased from 79%-82% to 60% (P = .064), and for persistent AF, when BMI was ≥35 kg/m2 ablation success decreased from 64%-70% to 52%-57% (P = .021). For long-standing AF, there was no impact of BMI on outcomes (P = .624). In multivariate analysis, BMI ≥35 kg/m2 predicted worse outcomes (P = .036). Higher BMI did not impact major complication rates (P = .336). However, when BMI was ≥40 kg/m2, minor (from 2.1% to 4.4%; P = .035) and total (from 3.5% to 6.7%; P = .023) complications increased. CONCLUSION: In patients undergoing AF ablation, increasing BMI is associated with more patient comorbidities and more persistent and long-standing AF. BMI ≥35 kg/m2 adversely impacts ablation outcomes, and BMI ≥40 kg/m2 increases minor complications.

Ablation of atypical atrial flutters using ultra high density-activation sequence mapping.

PURPOSE: The purpose of this study was to evaluate ultra high density-activation sequence mapping (UHD-ASM) for ablating atypical atrial flutters. METHODS: For 23 patients with 31 atypical atrial flutters (AAF), we created UHD-ASM. RESULTS: Demographics age = 65.3 ± 8.5 years, male = 78%, left atrial size = 4.66 ± 0.64 cm, redo ablation 20/23(87%). AAF were left atrial in 30 (97%). For each AAF, 1273 ± 697 points were used for UHD-ASM. Time to create and interpret the UHD-ASM was 20 ± 11 min. For every AAF, the entire circuit was identified. Thirty (97%) were macroreentry. AAF cycle length was 267 ± 49 ms, and the circuit length was 138 ± 38 mm (range 35-187). Macroreentry atrial flutters took varied pathways, but each had an area of slow conduction (ASC) averaging 16 ± 6 mm (range 6-29) in length. Entrainment was not utilized. We targeted the ASC and ablation terminated AAF directly in 19/31 (61.3%) and altered AAF activation in 7/31 (22.6%), all of which terminated directly with additional mapping/ablation. AAF degenerated to atrial fibrillation in 2/31 (6.5%) with RF and could not be reinduced after ASC ablation. Median time from initial ablation to AAF termination was 64 s. Thus, 28/31 (90.3%) terminated with RF energy and/or could not be reinduced after ASC ablation. At 1 year of follow-up, 77% were free of atrial tachycardia or atrial flutter and 61% were free of all atrial arrhythmias. CONCLUSIONS: Using rapidly acquired UHD-ASM, the entire AAF circuit as well as the target ASC could be identified. Most AAF were left atrial macroreentry. Ablation of the ASC or microreentry focuses directly terminated or eliminated AAF in 90.3% without the need for entrainment mapping.

Predicting atrial fibrillation ablation outcome: The CAAP-AF score.

BACKGROUND: Patients with a variety of clinical presentations undergo atrial fibrillation (AF) ablation. Long-term ablation success rates can vary considerably. OBJECTIVE: The purpose of this study was to develop a clinical scoring system to predict long-term freedom from AF after ablation. METHODS: We retrospectively derived the scoring system on a development cohort (DC) of 1125 patients undergoing AF ablation and tested it prospectively in a test cohort (TC) of 937 patients undergoing AF ablation. RESULTS: The demographics of the DC patients were as follows: age 62.3 ± 10.3 years, male sex 801 (71.2%), left atrial size 4.30 ± 0.69 cm, paroxysmal AF 348 (30.9%), number of drugs failed 1.3 ± 1.1, hypertension 525 (46.7%), diabetes 100 (8.9%), prior stroke/transient ischemic attack 78 (6.9%), prior cardioversion 528 (46.9%), and CHADS2 score 0.87 ± 0.97. Multivariate analysis showed 6 independent variables predicting freedom from AF after final ablation: coronary artery disease (P = .021), atrial diameter (P = .0003), age (P = .004), persistent or long-standing AF (P < .0001), number of antiarrhythmic drugs failed (P < .0001), and female sex (P = .0001). We created a scoring system (CAAP-AF) using these 6 variables, with scores ranging from 0 to 13 points. The 2-year AF-free rates by CAAP-AF scores were as follows: 0 = 100%, 1 = 95.7%, 2 = 96.3%, 3 = 83.1%, 4 = 85.5%, 5 = 79.9%, 6 = 76.1%, 7 = 63.4%, 8 = 51.1%, 9 = 53.6%, and ≥10 = 29.1%. Ablation success decreased as CAAP-AF scores increased (P < .0001). The CAAP-AF score also predicted freedom from AF in the TC. The 2-year Kaplan-Meier AF-free rates by CAAP-AF scores were as follows: 0 = 100%, 1 = 87.0%, 2 = 89.0%, 3 = 91.6%, 4 = 90.5%, 5 = 84.4%, 6 = 70.1%, 7 = 71.0%, 8 = 60.7%, 9 = 68.9%, and ≥10 = 51.3%. As CAAP-AF scores increased, 2-year freedom from AF in the TC decreased (P < .0001). CONCLUSION: An easily determined clinical scoring system was derived retrospectively and applied prospectively. The CAAP-AF score predicted freedom from AF after ablation in both a DC and a TC of patients undergoing AF ablation. The CAAP-AF score provides a realistic AF ablation outcome expectation for individual patients.

The Corepressor Rcor1 Is Essential for Normal Myeloerythroid Lineage Differentiation.

Based on its physical interactions with histone-modifying enzymes, the transcriptional corepressor Rcor1 has been implicated in the epigenetic regulation blood cell development. Previously, we have demonstrated that Rcor1 is essential for the maturation of definitive erythroid cells and fetal survival. To determine the functional role of Rcor1 in steady-state hematopoiesis in the adult, we used a conditional knockout approach. Here, we show that the loss of Rcor1 expression results in the rapid onset of severe anemia due to a complete, cell autonomous block in the maturation of committed erythroid progenitors. By contrast, both the frequency of megakaryocyte progenitors and their capacity to produce platelets were normal. Although the frequency of common lymphoid progenitors and T cells was not altered, B cells were significantly reduced and showed increased apoptosis. However, Rcor1-deficient bone marrow sustained normal levels of B-cells following transplantation, indicating a non-cell autonomous requirement for Rcor1 in B-cell survival. Evaluation of the myelomonocytic lineage revealed an absence of mature neutrophils and a significant increase in the absolute number of monocytic cells. Rcor1-deficient monocytes were less apoptotic and showed ∼100-fold more colony-forming activity than their normal counterparts, but did not give rise to leukemia. Moreover, Rcor1(-/-) monocytes exhibited extensive, cytokine-dependent self-renewal and overexpressed genes associated with hematopoietic stem/progenitor cell expansion including Gata2, Meis1, and Hoxa9. Taken together, these data demonstrate that Rcor1 is essential for the normal differentiation of myeloerythroid progenitors and for appropriately regulating self-renewal activity in the monocyte lineage.

The triterpenoid RTA 408 is a robust mitigator of hematopoietic acute radiation syndrome in mice.

Bone marrow suppression due to exposure to ionizing radiation is a significant clinical problem associated with radiation therapy as well as with nonmedical radiation exposure. Currently, there are no small molecule agents available that can enhance hematopoietic regeneration after radiation exposure. Here, we report on the effective mitigation of acute hematopoietic radiation syndrome in mice by the synthetic triterpenoid, RTA 408. The administration of a brief course of RTA 408 treatment, beginning 24 h after lethal doses of radiation to bone marrow, significantly increased overall survival. Importantly, treatment with RTA 408 led to the full recovery of steady state hematopoiesis with normalization of the frequency of hematopoietic stem and progenitor cells. Moreover, hematopoietic stem cells from RTA 408-mitigated mice showed lineage-balanced, long-term, multilineage potential in serial transplantation assays, indicative of their normal self-renewal activity. The potency of RTA 408 in mitigating radiation-induced bone marrow suppression makes it an attractive candidate for potential clinical use in treating both therapy-related and unanticipated radiation exposure.

Intestinal microbiota-derived metabolomic blood plasma markers for prior radiation injury.

PURPOSE: Assessing whole-body radiation injury and absorbed dose is essential for remediation efforts following accidental or deliberate exposure in medical, industrial, military, or terrorist incidents. We hypothesize that variations in specific metabolite concentrations extracted from blood plasma would correlate with whole-body radiation injury and dose. METHODS AND MATERIALS: Groups of C57BL/6 mice (n=12 per group) were exposed to 0, 2, 4, 8, and 10.4 Gy of whole-body gamma radiation. At 24 hours after treatment, all animals were euthanized, and both plasma and liver biopsy samples were obtained, the latter being used to identify a distinct hepatic radiation injury response within plasma. A semiquantitative, untargeted metabolite/lipid profile was developed using gas chromatography-mass spectrometry and liquid chromatography-tandem mass spectrometry, which identified 354 biochemical compounds. A second set of C57BL/6 mice (n=6 per group) were used to assess a subset of identified plasma markers beyond 24 hours. RESULTS: We identified a cohort of 37 biochemical compounds in plasma that yielded the optimal separation of the irradiated sample groups, with the most correlated metabolites associated with pyrimidine (positively correlated) and tryptophan (negatively correlated) metabolism. The latter were predominantly associated with indole compounds, and there was evidence that these were also correlated between liver and plasma. No evidence of saturation as a function of dose was observed, as has been noted for studies involving metabolite analysis of urine. CONCLUSIONS: Plasma profiling of specific metabolites related to pyrimidine and tryptophan pathways can be used to differentiate whole-body radiation injury and dose response. As the tryptophan-associated indole compounds have their origin in the intestinal microbiome and subsequently the liver, these metabolites particularly represent an attractive marker for radiation injury within blood plasma.

Functional integration of acute myeloid leukemia into the vascular niche.

Vascular endothelial cells are a critical component of the hematopoietic microenvironment that regulates blood cell production. Recent studies suggest the existence of functional cross-talk between hematologic malignancies and vascular endothelium. Here we show that human acute myeloid leukemia (AML) localizes to the vasculature in both patients and in a xenograft model. A significant number of vascular tissue-associated AML cells (V-AML) integrate into vasculature in vivo and can fuse with endothelial cells. V-AML cells acquire several endothelial cell-like characteristics, including the upregulation of CD105, a receptor associated with activated endothelium. Remarkably, endothelial-integrated V-AML shows an almost fourfold reduction in proliferative activity compared with non-vascular-associated AML. Primary AML cells can be induced to downregulate the expression of their hematopoietic markers in vitro and differentiate into phenotypically and functionally defined endothelial-like cells. After transplantation, these leukemia-derived endothelial cells are capable of giving rise to AML. These novel functional interactions between AML cells and normal endothelium along with the reversible endothelial cell potential of AML suggest that vascular endothelium may serve as a previously unrecognized reservoir for AML.

Corepressor Rcor1 is essential for murine erythropoiesis.

The corepressor Rcor1 has been linked biochemically to hematopoiesis, but its function in vivo remains unknown. We show that mice deleted for Rcor1 are profoundly anemic and die in late gestation. Definitive erythroid cells from mutant mice arrest at the transition from proerythroblast to basophilic erythroblast. Remarkably, Rcor1 null erythroid progenitors cultured in vitro form myeloid colonies instead of erythroid colonies. The mutant proerythroblasts also aberrantly express genes of the myeloid lineage as well as genes typical of hematopoietic stem cells (HSCs) and/or progenitor cells. The colony-stimulating factor 2 receptor ß subunit (Csf2rb), which codes for a receptor implicated in myeloid cytokine signaling, is a direct target for both Rcor1 and the transcription repressor Gfi1b in erythroid cells. In the absence of Rcor1, the Csf2rb gene is highly induced, and Rcor1(-/-) progenitors exhibit CSF2-dependent phospho-Stat5 hypersensitivity. Blocking this pathway can partially reduce myeloid colony formation by Rcor1-deficient erythroid progenitors. Thus, Rcor1 promotes erythropoiesis by repressing HSC and/or progenitor genes, as well as the genes and signaling pathways that lead to myeloid cell fate.

HCMV infection of humanized mice after transplantation of G-CSF-mobilized peripheral blood stem cells from HCMV-seropositive donors.

Human cytomegalovirus (HCMV) infection, including primary infection resulting from transmission from a seropositive donor to a seronegative recipient (D(+)/R(-)), remains a significant problem in the setting of peripheral blood stem cell transplantation (PBSCT). The lack of a suitable animal model for studying HCMV transmission after PBSCT is a major barrier to understanding this process and, consequently, developing novel interventions to prevent HCMV infection. Our previous work demonstrated that human CD34(+) progenitor cell-engrafted NOD-scid IL2Rγc(null) (NSG) mice support latent HCMV infection after direct inoculation and reactivation after treatment with granulocyte colony-stimulating factor. To more accurately recapitulate HCMV infection in the D(+)/R(-) PBSCT setting, granulocyte colony-stimulating factor-mobilized peripheral blood stem cells from seropositive donors were used to engraft NSG mice. All recipient mice demonstrated evidence of HCMV infection in liver, spleen, and bone marrow. These findings validate the NSG mouse model for studying HCMV transmission during PBSCT.