Brain Cancer SPORE Research Projects

The Mayo Clinic Brain Cancer SPORE Grant has four research projects. These research projects reflect the most innovative ways to generate advances in the understanding of glioma biology and to reflect Mayo Clinic's strengths in basic, translational, clinical and clinical trials research in gliomas.

Project 1: Influence of DNA repair on PARP inhibitor efficacy in glioblastoma multiforme

Co-leaders: Jann N. Sarkaria, M.D., and Nadia N. Laack, M.D.
Co-investigators: Timothy J. Kaufmann, M.D., and Meena Shrivastav, Ph.D.

The addition of temozolomide during and after radiation therapy improved survival for patients with newly diagnosed glioblastoma multiforme and is the current standard of care. However, the survival benefit of temozolomide therapy is limited by the development of temozolomide resistance in almost all patients.

There is significant interest in identifying molecular sensitizing strategies to improve the efficacy of temozolomide.

One promising strategy targeting the repair of temozolomide-induced DNA damage is inhibition of poly-ADP-ribose polymerase (PARP). PARP is indirectly involved in numerous repair pathways, and previous data suggest that PARP inhibitors will sensitize essentially all tumors to temozolomide.

While the project's preliminary in vivo data in a panel of primary glioblastoma multiforme xenografts confirms a robust sensitizing effect of the PARP inhibitor ABT-888 when combined with temozolomide or temozolomide and radiation therapy, the data also demonstrate that combination therapy with PARP inhibitors is only effective in tumors that are inherently sensitive to temozolomide. Defects in homologous recombination-mediated DNA repair are associated with increased sensitivity to temozolomide and to PARP inhibitor therapy.

This project has three aims:

  • Aim 1. Test whether deregulation of homologous recombination is associated with greater temozolomide-sensitizing effects of PARP inhibitors. Defects in homologous recombination capacity are associated with increased efficacy of PARP inhibitors alone and in combination with cytotoxic chemotherapy. A subset of glioblastoma multiforme harbors mutations within genes important for homologous recombination activity. This aim will test whether molecular defects within these genes influence the efficacy of combined ABT-888/temozolomide therapy.
  • Aim 2. Evaluate the influence of combination therapy on resistance emergence. This project's preliminary data demonstrate a loss of efficacy of PARP inhibitors in models of acquired temozolomide resistance. These data suggest that emergence of temozolomide resistance may negatively impact the efficacy of combined therapy. Conversely, other data suggest that radiation may influence the emergence of temozolomide resistance in some tumors. This aim will use the project's xenograft models to characterize the interplay between temozolomide resistance and PARP inhibitor therapy.
  • Aim 3. Evaluate whether a molecular signature can identify patients likely to benefit from ABT-888 combined with chemoradiotherapy. PARP plays crucial roles in homologous recombination-mediated repair of O6MG-induced replication fork collapse. Because suppression of O-6-methylguanine-DNA methyltransferase (MGMT) by promoter methylation is permissive for replication arrest, this project hypothesizes that MGMT promoter methylation, potentially combined with other molecular features, can be used to enrich the cohort for patients likely to benefit from combined therapy. The project team plans to test this in a single-arm phase II clinical trial.

The development of effective chemo- and radio-sensitizing strategies could significantly improve the survival of patients with glioblastoma multiforme. PARP inhibitors show significant promise as a specific temozolomide-sensitizing strategy.

This project is testing whether defects in DNA repair within tumors can be used to predict response to the combination of a PARP inhibitor with standard chemoradiotherapy in glioblastoma multiforme. Ultimately, this could lead to the use of molecular markers to customize therapy.

Project 2: Optimizing measles virotherapy in the treatment of gliomas

Co-leaders: Evanthia Galanis, M.D., and Ian F. Parney, M.D., Ph.D.
Co-investigators: Kah Whye Peng, Ph.D., and Fredric B. Meyer, M.D.
Significant contributors: Jan C. Buckner, M.D., Allan B. Dietz, Ph.D., and Jann N. Sarkaria, M.D.

Building on its previous work, this brain cancer research team hypothesizes that by increasing the efficiency and extent of tumor cell destruction and by introducing a therapeutic transgene, they can further augment the anti-tumor activity of measles virotherapy in gliomas.

This project team was the first to demonstrate that engineered measles virus (MV) strains have significant anti-tumor activity against gliomas. Their tumor specificity is due to abundant expression of the measles virus receptor CD46 in glioma cells. Upon entering the tumor cells, the virus causes membrane fusion with neighboring cells, syncytia formation and death.

In addition, this team has translated this approach into the first human clinical trial of a measles virus derivative producing human carcinoembryonic antigen, MV-CEA (CEA added to facilitate viral monitoring) in recurrent glioblastoma multiforme patients.

The team plans to accomplish this by testing the translational potential of three novel approaches: a different measles virus strain, MV-NIS, which encodes the sodium iodine symporter (NIS) gene, thus allowing imaging of viral distribution in vivo; enhancing MV-NIS oncolysis by exploiting NIS as therapeutic transgene with application of the beta and gamma emitter 131I (radiovirotherapy); and combining measles virus derivatives with cyclophosphamide, an agent that has been shown to suppress antiviral innate and adaptive immunity and increase viral proliferation in tumors.

This project has four aims:

  • Aim 1. To evaluate the therapeutic potential of MV-NIS-based virotherapy and radiovirotherapy against glioblastoma multiforme and compare its anti-tumor activity with MV-CEA. MV-NIS is a more recently constructed MV-Edmonston derivative, with similar backbone to MV-CEA, encoding the sodium iodine symporter gene. MV-NIS allows use of radioactive iodine and technetium isotopes for imaging of viral replication, and iodine isotopes for treatment purposes. The project team has already developed Food and Drug Administration-approved methodology for production of MV-NIS. The virus is easier to manufacture than is MV-CEA and grows to higher titers. This aim will test the hypothesis that MV-NIS is equivalent or superior to MV-CEA and that its potency can be further enhanced by 131I mediated radiovirotherapy.
  • Aim 2. To test combination strategies with cyclophosphamide, a suppressant of the innate immune response, to further increase the potency of measles virotherapy or radiovirotherapy. In preliminary experiments, the project team demonstrated that administration of cyclophosphamide prior to measles virus administration resulted in significant potentiation of the oncolytic activity of measles virus in orthotopic glioma xenografts by increasing viral proliferation in glioma tumors. This aim will optimize the dose and schedule of cyclophosphamide in order to achieve optimal anti-tumor activity of measles-based virotherapy or radiovirotherapy against orthotopic glioblastoma xenografts.
  • Aim 3. To perform toxicology and biodistribution studies in MV-susceptible transgenic mice and rhesus macaques in order to determine the safety of the optimal translational strategy. Aims 1 and 2 are testing different approaches to further augment the efficacy of measles virotherapy in the treatment of gliomas. The safety of the optimal efficacy enhancing approach will be carefully assessed in measles-susceptible animal models prior to clinical translation.
  • Aim 4. To employ the approach with the optimal safety and efficacy profile in a subsequent phase I clinical trial in patients with recurrent glioblastoma multiforme. Collectively, these studies will provide information that will guide the selection of the most promising approach to test in a subsequent phase I trial in patients with recurrent glioblastoma multiforme.

In preclinical models, measles vaccine strains have potent anti-tumor activity against gliomas and demonstrate synergy with existing therapies. This application proposes to investigate strategies optimizing the use of measles vaccine strains as novel anti-tumor agents in the treatment of gliomas.

Project 3: Histone modification and glioblastoma multiforme therapy

Co-leaders: Zhenkun Lou, Ph.D., and Jan C. Buckner, M.D.

This project's recent findings led the research team to hypothesize that histone methyltransferase (HMT) MMSET is a contributor to chemo/radioresistance in patients with glioblastoma multiforme. MMSET (also called WHSC1, NSD2) has been shown to methylate histone H4 Lys20 (H4K20), H3 Lys27 (H3K27) and H3 Lys36 (H3K36).

Aside from several reports linking MMSET to transcriptional regulation, its cellular function remains obscure. The project team found that MMSET participates in the ATM-MDC1-53BP1 pathway during the DNA damage response. Specifically, MMSET accumulates at sites of DNA damage.

Correlating with this, H4K20 methylation, which is required for 53BP1 recruitment, also increases at DNA damage sites. Downregulation of MMSET decreases H4K20 methylation and abolishes the accumulation of 53BP1 to DNA damage sites.

These results suggest that MMSET functions as an upstream regulator of 53BP1 through its HMT activity. In support of its role in DNA damage responses, MMSET affects cellular sensitivity to temozolomide and radiation.

The team also found that MMSET is overexpressed in a subset of glioblastoma lines and that overexpression of MMSET is associated with resistance to temozolomide and radiation.

Based on these preliminary findings, the team hypothesizes that MMSET regulates 53BP1 and the temozolomide and radiation response, and that misregulation of MMSET could affect glioblastoma multiforme sensitivity to chemo/radiotherapy.

This project is examining this hypothesis through three aims:

  • Aim 1. Structure-function analysis of MMSET in the DNA damage response. The project team found that MMSET regulates cellular response to temozolomide and radiation. In addition, MMSET regulates histone H4K20 methylation and the recruitment of 53BP1 to the sites of DNA damage. However, it's not clear if 53BP1 is the major downstream factor of MMSET in DNA damage response. MMSET could also regulate other DNA damage factors through its methyltransferase activity or protein-protein interactions. In addition, MMSET could modulate DNA damage response through its transcriptional activity. The team is investigating these potential mechanisms in this aim.
  • Aim 2. Investigate the role of MMSET in TMZ/RT response using mouse models. The project team is using primary xenograft models to examine the influence of MMSET overexpression on temozolomide and radiation resistance. The team is also exploring ways to sensitize glioblastoma multiforme that have MMSET overexpression to temozolomide and radiation treatment.
  • Aim 3. Examine the expression of MMSET in glioblastoma multiforme patients and its correlation with temozolomide and radiation response. The project team is using clinical samples to examine the influence of MMSET overexpression on temozolomide and radiation resistance in relationship to another key prognostic marker, MGMT promoter methylation.

This project is also testing whether overexpression of MMSET contributes to the chemoradioresistance of glioblastoma multiforme. This could ultimately lead to the identification of a novel drug target and biomarker for glioblastoma multiforme therapy.

Project 4: Clinical relevance of chromosome 5p/9p/20q/8q germline alterations in glioma

Co-leaders: Robert B. Jenkins, M.D., Ph.D., and Daniel Honore Lachance, M.D.
Co-investigators: Jeanette E. Eckel-Passow, Ph.D., and Hugues Sicotte, Ph.D.

This project builds on previous research and proposes to further validate the germline alteration(s) within or near the CDKN2A/B (9p21), TERT (5p15), RTEL1 (20q13) and CCDC26/MLZE (8q24) regions that are associated with glioma development to correlate alteration status with somatic genetic and expression alterations, with pathological variables and with clinical parameters.

The development of glioblastoma has been hypothesized to be associated with relatively common germline alterations with limited penetrance. Recently, two genome-wide association studies using various single nucleotide polymorphism (SNP) array platforms have been performed in gliomas.

Collaborating with the University of California at San Francisco (UCSF), the project team recently reported that SNPs mapping near CDKN2A/B/ARF (9p21) and RTEL1 (20q13) are associated with the development of high-grade astrocytomas. Other researchers have also observed these associations, as well as associations near TERT (5p15) and CCDC26/MLZE (8q24).

A reanalysis of data from UCSF and Mayo Clinic suggests that the RTEL1 (20q13), TERT (5p15) and CCDC26/MLZE (8q24) associations are largely restricted to patients with glioblastoma multiforme, anaplastic astrocytoma and oligodendroglioma. This suggests that different germline polymorphisms are associated with the development of different glioma subtypes.

This project has two aims:

  • Aim 1. Perform detailed germline genetic analysis of the associated CDKN2A/B (9p21), TERT (5p15), RTEL1 (20q13) and CCDC26/MLZE (8q24) regions using three cohorts of prospectively acquired glioma cases and controls to estimate the prevalence and relative risk of known polymorphisms and new alterations.
    • Aim 1a. Perform custom genotyping of up to 384 candidate SNPs/alterations and 150 other alterations newly identified by the American Recovery and Reinvestment Act RC1 grant using two case-control sets: 582 previously collected prospective cases and 532 controls, and 600 cases and 600 matched controls from the UCSF SPORE. Impute additional genotypes and haplotypes and assess association with glioma development.
    • Aim 1b. Further replication and validation based on results from Aim 1a through custom genotyping of up to 384 refined candidate SNPs/alterations, 150 other alterations in 450 new glioma cases and 450 new matched controls and in combined total samples (approximately 1,600 cases and approximately 1,600 controls).
  • Aim 2. Evaluate the clinical, histopathologic and molecular pathologic relevance of the germline CDKN2A/B (9p21), TERT (5p15), RTEL1 (20q13) and CCDC26/MLZE (8q24) alterations.
    • Aim 2a. Determine the associations of the germline alterations with the development of a specific genetic subclass of glioma: expression subclass (for example, proneural, neural, classical, mesenchymal), acquired copy number subclass (for example, +7, -10, -1p, -19q), and/or acquired mutation subclass (for example, PTEN, p53, IDH1/2, EGFR).
    • Aim 2b. Assess and model the association of the germline alterations (Aim 1) and subclasses (Aim 2a) with grade (astrocytoma vs. anaplastic astrocytoma vs. glioblastoma multiforme), morphology (oligodendroglioma vs. malignant oligoastrocytoma vs. astrocytoma), Grade I vs. Grade II glioblastoma multiforme and survival, adjusting for key clinical variables including age and gender.