John Ohlfest, Ph.D.

ohlfe001@umn.edu

Education

Dr. Ohlfest is an Assistant Professor and the Director of the gene therapy program in Department of Neurosurgery and a faculty member of the Stem Cell Institute. Dr. Ohlfest studied molecular biology as an undergraduate at Iowa State University and received his Ph.D. in molecular genetics and cell biology at the University of Minnesota. He then did post-doctoral research with Dr. Andrew Freese at the University of Minnesota focusing on gene therapy in the central nervous system.

Research Interests

The Ohlfest lab is focused on understanding the mechanisms of brain tumorogenesis and immune evasion, and using this information to improve therapeutic outcome. There are a several projects ongoing that all relate to the central goal.

Brain Tumor Immunotherapy:
Although select patients appear to benefit from immunotherapy, there is considerable debate about the optimal way to maximize the effectiveness of immunotherapy. Our research aims to improve the efficacy of tumor vaccines using several different mouse models of glioma, an aggressive brain tumor. We are systematically optimizing each step of the immune response that occurs following vaccination from the innate response at the vaccination site to the effector response in the brain. There are several ongoing projects in this area.

1) Influence of oxygen tension on tumor cell immunogenicity
2) Toll-like receptor agonists as vaccine adjuvants
3) Optimizing the priming of tumor-reactive T cells in the lymph nodes
4) Understanding factors that influence lymphocyte trafficking into the brain
5) Understanding and overcoming immune suppression at the tumor site
6) Requirements for antibody and NK cell response in vaccination

Requirements for Tumor Renewal and Progression:
Glioblastoma is difficult to cure by surgery because glioma cells migrate centimeters away from the main tumor mass and self-renew to repopulate the tumor. We have identified CD44, a cell surface receptor for hyaluronic acid, as playing a key role in glioma cell invasion and self-renewal. Using CD44+/+ and CD44-/- mice, we are interrogating the role CD44 plays in the tumor recurrence, resistance to chemotherapy, and evading the immune response. This project is made possible due to the novel spontaneous glioma model we developed that can be induced in any mouse strain (Cancer Res. 2009 Jan 15;69(2):431-9.).

Drug Delivery:
The blood brain barrier (BBB) restricts the influx of drugs into normal brain structures where glioma cells typically infiltrate. The BBB has a mechanical (size exclusion) and active mechanism (ATP-dependent drug transporters) to exclude drugs and antibodies from entrance. We have several projects ongoing in this area will the goal of increasing the efficacy of drugs to treat tumors directly, or by delivering drugs overcome immune suppression at the tumor site.
1) Pharmacologic inhibition of drug efflux transport at BBB and tumor cell barriers
2) Convection enhanced delivery (CED) by neurosurgical intervention to bypass the BBB by placing catheters in the brain directly
3) Improve catheter design for CED
4) Chemotherapy conditioning to deplete myeloid derived suppressor cells and regulatory T cells

Comparative Oncology:
While mouse models of brain cancer provide us with important information, they are limited in their ability to predict human responses. Therefore we have initiated a canine brain tumor clinical trials program. We currently offer several clinical trials to pet owners that are faced with the diagnosis of a brain tumor in their dog. These treatments include anti-tumor vaccines, chemotherapy, gene therapy, and convection enhanced delivery. Moreover, we typically perform surgery to removal as much of the tumor as possible; this maximizes the benefit for the dog and mimics the human clinical situation. Because these canine tumors are naturally arising and can be treated with human-scale doses, the results have great relevance to human medicine. This research program plays an instrumental role in our clinical trial design in humans.

Clinical Research:
We are actively involved in clinical trials. Our lab has developed immunotherapy interventions that will be tested in brain tumor patients. In addition to developing the treatment, we also conduct immune monitoring to measure the immune response evoked by vaccination. We use this information to design more effective therapy.

To learn more about our lab visit www.braintumorlab.com.

Peer Reviewed Articles:

1. Ohlfest JR, Ivics Z, Izsvák Z. Transposable elements as plasmid-based vectors for long-term gene transfer into tumors. Methods Mol Biol. 2009;542:105-16.

2. Oh S, Ohlfest JR, Todhunter DA, Vallera VD, Hall WA, Chen H, Vallera DA. Intracranial elimination of human glioblastoma brain tumors in nude rats using the bispecific ligan-directed toxin, DTEGF13 and convection enhanced delivery. Journal of Neuro-Oncology. 2009 Jun 11. [Epub ahead of print]

3. Wiesner SM, Decker SA, Larson JD, Ericson K, Forster C, Gallardo J, Zamora EA, Donelson RB, Long C, Demorest ZL, Low WC, SantaCruz K, Largaespada DA, Ohlfest JR. De Novo Induction of genetically engineered brain tumors in mice with plasmid DNA. Cancer Research. 2009 Jan 15;69(2):431-439.

4. Xiong Z, Gharagozlou S, Vengco I, Chen W, Ohlfest JR. Effective CpG Immunotherapy of Breast Carcinoma Prevents but Fails to Eradicate Established Brain Metastasis. Clinical Cancer Research. 2008 Sep 1;14(17):5484-5493.

5. Wu A, Oh S, Ericson K, Chen L, Hall WA, Champoux PE, Low WC, Ohlfest JR. Persistence of CD133+ Cells in Human and Mouse Glioma Cell Lines: detailed characterization of GL 261 glioma cells with cancer stem cell-like properties. Stem Cells and Development. 2008 Feb;17(1):173-184.

6. Wu A, Oh S, Gharagozlou S, Vedi RN, Ericson K, Chen W, Low WC, Ohlfest JR. In Vivo Vaccination with Tumor Cell Lysate plus CpG Oligodeoxynucleotides Eradicates Murine Glioblastoma. Journal of Immunotherapy. 2007;30(8):789-797.

7. Candolfi M, Curtin JF, Nichols SW, King GD, Barcia C, Pluhar GE, McNiel E, Ohlfest JR, Freese AB, Moore PF, Lowenstein PR, Castro, MG. Glioblastoma Multiforme (GBM): A Comparative Histopathological Analysis of Experimental Gliomas in Mice and Rats with Spontaneous GBM of Dogs and Humans. Journal of Neuro-oncology. 2007 Sep 15; (Epub ahead of print, PMID 17874037).

8. Oh S, Odland R, Wilson S, Kroeger KM, Liu C, Castro MG, Lowenstein PR, Freese A, Hall WA, Ohlfest JR. Improved distribution of small molecules and viral vectors in the murine brain using a hollow fiber catheter. Journal of Neurosurgery. 2007 Sep;107(3):568-577.

9. Oh S, Pluhar GE, McNeil EA, Kroeger KM, Liu C, Castro MG, Lowenstein PR, Freese A, Ohlfest JR. Efficacy of Nonviral Gene Transfer into the Canine Brain. Journal of Neurosurgery. 2007 Jul;107:136-144.

10. Candolfi M, Pluhar GE, Kroeger K, Puntel M, Curtin J, Barcia C, Muhammad AG, Xiong W, Liu C, Mondkar S, Kuoy W, Kang T, McNeil EA, Greese AB, Ohlfest JR, Moore P, Palmer D, Ng P, Young JD, Lowenstein PR, Castro MG. Optimization of adenoviral vector mediated expression in the canine brain in vivo, and in canine glioma cells in vitro. Neuro-oncology. 2007 Jul;9(3):245-58. Epub 2007 May 23.

11. Wu A, Oh S, Ericson K, Demorest ZL, Vengco I, Gharagozlou S, Chen W,Low WC, Ohlfest JR. Transposon-based Interferon Gamma Gene Transfer Overcomes Limitations of Episomal Plasmid for Immunogene Therapy of Glioblastoma. Cancer Gene Therapy. 2007 Jun;14(6):550-560.

12. Wu A, Xiao J, Chen W, Hall WA, Low WC, Ohlfest JR. Expression of MHC I and NK ligands on human CD133+ brain tumor cells: possible targets of immunotherapy. Journal of Neuro-oncology. 2007 Jun;83(2):121-131.

13. Candolfi M, Kroeger KM, Pluhar GE, Liu C, Barcia C, Bergeron J, Puntel M, Curtin JF, McNiel EA, FreeseAB, Ohlfest JR, Moore PF, Kuoy W, Lowenstein PR, Castro MG. Adenoviral mediated gene transfer into the dog brain in vivo. Neurosurgery. 2007 Jan;60(1):167-77.

14. Ohlfest JR, Freese AB, Largaespada DA. Nonviral Vectors for Cancer Gene Therapy: Prospects for Integrating Vectors and Combination Therapies. Current Gene Therapy. 2005 Dec;5(6):629-641.

15. Ohlfest JR, Demorest ZL, Mootoka Y, Vengco I, Oh S, Chen E, Scappaticci FA, Saplis RJ, Ekker SE, Low WC, Freese AB, and Largaespada DA. Combinatorial antiangiogenic gene therapy by nonviral gene transfer using the sleeping beauty transposon causes tumor regression and improves survival in mice bearing intracranial human glioblastoma. Molecular Therapy. 2005 Nov;12(5):778-788.

16. Wiesner SM, Freese AB, Ohlfest JR. Emerging concepts in glioma biology: implications for clinical protocols and rational treatment strategies. Neurosurgical Focus. 2005 Oct 15;19(4):E3.

17. Ohlfest JR, Frandsen JL, Fritz S, Lobitz PD, Perkinson SG, Clark KJ, Nelsestuen G, Key NS, McIvor RS, Hackett PB, Largaespada DA. Phenotypic correction and long-term expression of factor VIII in hemophilic mice by immunotolerization and nonviral gene transfer using the Sleeping Beauty transposon system. Blood. 2005 April 1;105(7):2691-2698. Epub 2004 Dec 2.

18. Ohlfest JR, Lobitz PD, Perkinson SG, Largaespada DA. Integration and long-term expression in xenografted human glioblastoma cells using a plasmid-based transposon system. Molecular Therapy. 2004 Aug;10(2):260-268.