New Therapeutic Paradigms
Metabolic Dysregulation in Tumors
Metabolic dysregulation in tumors is a topic of intense interest in the study of cancer. We are investigating the therapeutic value of a using a high-fat, low-carbohydrate ketogenic diet to alter the cellular metabolism of tumors in combination with traditional radiation and chemotherapy. This diet is a highly regimented, established nonpharmacologic treatment for refractory epilepsy. We have found that it slows the growth of brain tumor cells in laboratory experiments and enhances survival in a murine model of malignant brain tumors. When combined with radiation or Temodar®, it significantly increased survival. Molecular analysis of the mechanism of action has demonstrated multiple effects on tumors:
- A reduction in reactive oxygen species
- A reduction in the expression of genes involved in growth factor pathways known to be involved in tumor growth
- An overall change in gene expression to a state similar to that seen in normal brain
We continue to study the use of metabolic alteration to enhance the efficacy of currently used therapies in a preclinical setting.
Scutellaria Baicalensis as an Adjuvant to Radiation and Chemotherapy
Our second investigational complementary therapy is based on the extract of the Chinese medicinal herb Scutellaria baicalensis (Baikal Skullcap). Our published work demonstrates that the extract of this plant inhibits the growth of tumor cells and potentiates the effect of traditional chemotherapeutic agents. We are studying the effects of this compound both in a standalone fashion and in combination with radiation and chemotherapy. In vivo analyses of the efficacy of this extract and the isolated active ingredients are progressing.
Resistance to Current Therapies
Resistance of Tumor Cells to Gamma Knife and Cyber Knife Radiotherapies
In collaboration with Kris Smith, MD, we are studying the resistance of tumors to Gamma Knife® and Cyber Knife® radiation therapies. There are few, if any, laboratory studies of tumoral resistance to the high doses of radiation given during Gamma and Cyber Knife treatment. These therapies focus high doses of radiation on a tumor while sparing healthy brain tissue from such high doses. This approach reduces side effects while maximizing tumor death, and is often used at Barrow when tumors recur after standard radiation and chemotherapy. However, some cells survive even these high doses of radiation.
Improving the efficacy of these therapies requires study of the cells that survive Gamma and Cyber Knife treatments. We therefore designed and constructed a device that allows us to put cells grown in the laboratory into the Gamma Knife machine. We have also devised an assay that gives an excellent view of the overall radiation sensitivity or resistance of the cells and the relative number of cells resistant to higher doses of radiation. Using this method, we can identify the resistant cells and isolate and grow them for further study. Molecular analyses of these resistant cells and the conditions that lead to resistance are being studied.
Therapy Resistance in Recurrent Tumors
The use of cell lines from our extensive tumor bank has permitted us to compare gene expression in primary tumors to recurrent tumor from the same patient. Typically, cells from a recurrent tumor are more resistant to therapy than cells from the primary tumor. One gene that may be involved in resistance to therapy is crystallin alpha B. We are using transfection and siRNA techniques to determine if this gene directly contributes to therapy.
We have initiated a multimodal collaborative investigation of meningiomas. Although typically benign, a subset of these tumors behaves aggressively. We are using a combination of techniques to identify tumors that are more likely to be malignant. Our published molecular cytogenetic analysis of a large group of meningiomas demonstrated genetic heterogeneity even in benign tumors. That is, not all of the cells have the same genetic aberrations.
There appears to be a correlation between the presence of multiple genetic aberrations and tumor aggression. In collaboration with Ari Perry, MD at the University of California, San Francisco, we used a number of techniques to identify a “molecular signature” that can serve a as marker for tumor aggression in meningiomas. In addition to these molecular studies, we have an ongoing collaboration with Mark C. Preul, MD, Director of Neurosurgery Research at Barrow, to correlate regional molecular results to those obtained by magnetic resonance spectroscopy of tissue extracts, tissue chunks, and patient tumors.
T(11;22) in Recurrent Tumor
We have previously identified three translocations involving chromosomes 11 and 22 in cells from tumors that recurred after therapy, but not in cells or tissue from the primary tumors from the same patients. The selection for cells containing t(11;22) in the recurrent tumor suggests that the translocation provides a selective advantage for the tumor cell and may serve as a target for the design of a novel therapy that is efficacious against recurrent (therapy-resistant) malignant brain tumors. We are the first laboratory to describe a specific, reproducible translocation in brain tumors.
However, further study required complete mapping of the translocations. This project is now being pursued through collaboration with Andy Futreal, PhD from the Sanger Center in England. He has used new technology to analyze the genomic alterations (including translocations) found in our cells. This work will lead to the complete mapping of our translocation and analysis for its utility in the design of a novel therapy for recurrent tumor.
Hand-Held Confocal Microscope (OptiScan)
In collaboration with Mark Preul, MD, and the Neurosurgery Research Laboratory, our in vivo immunocompetent bioluminescent mouse model of intracranial malignant glioma is being used in studies using the Zeiss in vivo confocal microscope (OptiScan). We are using an antibody that interacts with our GL261-luc2 cells to tag the with tumor cells with fluorescence, which should be visible using both the IVIS® Spectrum in vivo imaging system and the OptiScan in vivo confocal microscope. This antibody will be injected into the mouse and allowed to home in on the tumor cells. We will analyze their macroscopic location using the IVIS system and their microscopic localization using the Optiscan in vivo confocal microscope. We hypothesize that the use of labeled antibodies will improve the ability of neurosurgeons to identify tumor cells, especially at the invading edge of the tumor. This technique is a prototype for the design of a labeled antibody for eventual use in humans.
Our extensive bank of tumor cells and expertise in fluorescent in situ hybridization has led to a long-term collaboration with Markus Bredel, MD, PhD. This work has analyzed the genetic “landscape” of human glioblastomas and has demonstrated that the gene encoding NFKBIA promotes tumorigenesis in glioblastomas that lack certain alterations in the epidermal growth factor receptor pathway.
We are collaborating with Dr. Phillip Stafford from the Biodesign Institute at Arizona State University to identify immunosignatures from blood serum that would be an early indicator of tumor recurrence in brain tumor patients.