Education & Certifications
Bachelor of Arts, Stanford University, HUMBI-BAH (2010)
We generated a mouse model for hemophilia A that combines a homozygous knockout for murine factor VIII (FVIII) and a homozygous addition of a mutant human FVIII (hFVIII). The resulting mouse, having no detectable FVIII protein or activity and tolerant to hFVIII, is useful for evaluating FVIII gene-therapy protocols. This model was used to develop an effective gene-therapy strategy using the ?C31 integrase to mediate permanent genomic integration of an hFVIII cDNA deleted for the B-domain. Various plasmids encoding ?C31 integrase and hFVIII were delivered to the livers of these mice by using hydrodynamic tail-vein injection. Long-term expression of therapeutic levels of hFVIII was observed over a 6-month time course when an intron was included in the hFVIII expression cassette and wild-type ?C31 integrase was used. A second dose of the hFVIII and integrase plasmids resulted in higher long-term hFVIII levels, indicating that incremental doses were beneficial and that a second dose of ?C31 integrase was tolerated. We observed a significant decrease in the bleeding time after a tail-clip challenge in mice treated with plasmids expressing hFVIII and ?C31 integrase. Genomic integration of the hFVIII expression plasmid was demonstrated by junction PCR at a known hotspot for integration in mouse liver. The ?C31 integrase system provided a nonviral method to achieve long-term FVIII gene therapy in a relevant mouse model of hemophilia A.
View details for DOI 10.1089/hum.2011.110
View details for Web of Science ID 000303046800009
View details for PubMedID 22077817
The ?C31 integrase system provides genomic integration of plasmid DNA that may be useful in gene therapy. For example, the ?C31 system has been used in combination with hydrodynamic injection to achieve long-term expression of factor IX in mouse liver. However, a concern is that prolonged expression of ?C31 integrase within cells could potentially stimulate chromosome rearrangements or an immune response. Western blot and immunofluorescence analyses were performed to investigate the duration of ?C31 integrase expression in mouse liver. Integrase was expressed within 2 to 3 hr after hydrodynamic injection of a plasmid expressing ?C31 integrase. Expression peaked between 8 and 16 hr and fell to background levels by 24-48 hr postinjection. Analysis of the amount of integrase plasmid DNA present in the liver over time suggested that the brief period of integrase expression could largely be accounted for by rapid loss of the bulk of the plasmid DNA, as well as by silencing of plasmid expression. PCR analysis of integration indicated that ?C31 integrase carried out genomic integration of a codelivered attB-containing plasmid by 3 hr after plasmid injection. Integrase was expressed for longer times and at higher levels in transfected cultured cells compared with liver. Inhibitor studies suggested that the enzyme had a short half-life and was degraded by the 26S proteasome. The short duration of integrase expression in liver and rapid integration reaction appear to be features favorable for use in gene therapy.
View details for DOI 10.1089/hum.2010.049
View details for Web of Science ID 000282955500007
View details for PubMedID 20497035
To evaluate the prognostic value of metabolic tumor volume measured on 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) imaging and other clinical factors in patients treated for locally advanced head-and-neck cancer (HNC) at a single institution.Between March 2003 and August 2007, 85 patients received positron emission tomography (PET)/computed tomography-guided chemoradiotherapy for HNC. Metabolically active tumor regions were delineated on pretreatment PET scans semiautomatically using custom software. We evaluated the relationship of (18)F-fluorodeoxyglucose-PET maximum standardized uptake value (SUV) and total metabolic tumor volume (MTV) with disease-free survival (DFS) and overall survival (OS).Mean follow-up for surviving patients was 20.4 months. The estimated 2-year locoregional control, DFS, and OS for the group were 88.0%, 69.5%, and 78.4%, respectively. The median time to first failure was 9.8 months among the 16 patients with relapse. An increase in MTV of 17.4 mL (difference between the 75th and 25th percentiles) was significantly associated with an increased hazard of first event (recurrence or death) (1.9-fold, p < 0.001), even after controlling for Karnofsky performance status (KPS) (1.8-fold, p = 0.001), and of death (2.1-fold, p < 0.001). We did not find a significant relationship of maximum SUV, stage, or other clinical factors with DFS or OS.Metabolic tumor volume is an adverse prognostic factor for disease recurrence and death in HNC. MTV retained significance after controlling for KPS, the only other significant adverse prognostic factor found in this cohort. MTV is a direct measure of tumor burden and is a potentially valuable tool for risk stratification and guiding treatment in future studies.
View details for DOI 10.1016/j.ijrobp.2008.10.060
View details for Web of Science ID 000268346100006
View details for PubMedID 19289263