Project Details
Description
PROJECT SUMMARY
Temozolomide (TMZ) chemotherapy is a key component of treatment for patients with newly diagnosed
glioblastoma (GBM) and provides clinically meaningful survival benefits. Cytotoxicity from TMZ results from
failure to repair TMZ-induced DNA methylation adducts. During replication, these lesions ultimately result in
replication fork collapse associated with DNA double strand breaks that are critically repaired by homologous
recombination (HR). In this context, we recently discovered that retinoblastoma binging protein 4 (RBBP4)
functions in a complex with histone acetyltransferase p300 (p300) as a epigenetic writer to key DNA repair
processes including six key HR genes (RAD50, BRCA1, BARD1 BRIP1 FIGNL1, and RAD51) that play
different roles in HR pathway. Specifically, knockdown of either RBBP4 or p300 in glioma cell lines and GBM
patient-derived xenograft (PDX) models results in marked suppression of these six gene products, impaired
HR activity associated with enhanced sensitivity to PARP inhibitors, and dramatically enhanced sensitivity to
TMZ in animal models. Downstream of RBBP4/p300 complex, bromodomain and extraterminal domain (BET)
family members (BRD2, BRD3, BRD4) function as key readers of p300-mediated acetylation marks to drive
gene expression. Based on this and our preliminary data, we hypothesize that the RBBP4/p300/BRD axis is a
key regulator of HR efficiency and is a promising pharmacologic strategy for developing a robust, novel, TMZ-
sensitizing strategy. There are both p300- and dual p300/BET-inhibitors now entering clinical testing in
oncology, which highlight the importance of fully understanding how this complex functions to regulate DNA
repair. We will explore this concept in a series of three specific aims:
Aim 1: Define the role of RBBP4/p300 in regulation of HR genes. We will extend our initial observations in
GBM43 to define the regulation of HR genes across multiple GBM models by this complex.
Aim 2: Evaluate the impact of RBBP4/p300 on DNA repair proficiency. We hypothesize that coordinated
suppression of multiple HR genes associated with disruption of RBBP4/p300/BET function results in profound
HR suppression and TMZ sensitizing effects as compared to modulation of only one component of HR.
Aim 3: Define the impact of targeting the p300/BRD4 axis on therapy response in GBM We will test the
efficacy of p300 and p300/BET inhibitors alone and in combination with TMZ in PDX models. Ultimately, these
studies are designed to provide a strong rationale to pursue these inhibitors in clinical trials for GBM.
Status | Active |
---|---|
Effective start/end date | 9/19/20 → 6/30/24 |
Funding
- National Cancer Institute: $354,592.00
- National Cancer Institute: $354,592.00
- National Cancer Institute: $363,827.00
- National Cancer Institute: $364,031.00
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