Abstract IA27: Exploiting the inhibition of cullin-RING-ligases in DSB repair as a therapeutic strategy
Bibliographic record
Abstract
Abstract While single component E3 ubiquitin ligases have established roles in DNA double-strand break (DSB) repair, the function of multicomponent cullin-RING-ligases (CRL) in DSB repair is only beginning to emerge. FBXW7 is a substrate recognition component of Skp1-Cullin1-F-box E3 ubiquitin ligases previously known only to regulate the proteasomal degradation of substrates such as Cyclin E and MCL1. Given that FBXW7 loss promotes genomic instability, we hypothesized that FBXW7 may have a direct function in DSB repair. To establish the functions of FBXW7 in DSB repair, we first demonstrated the rapid localization of FBXW7 to DSB sites in an ATM-dependent manner. Subsequently, we found that FBXW7 depletion impaired nonhomologous end-joining (NHEJ), but not homologous recombination (HR) repair, resulting in persistent radiation-induced DSBs. Investigation of the molecular mechanisms of FBXW7 in NHEJ revealed that FBXW7 interacts with and promotes K63-linked ubiquitination of XRCC4. This ubiquitination of XRCC4 promotes interaction between the XRCC4/XLF/LIG4 and DNAPK/KU70/KU80 complexes to facilitate NHEJ. To begin to therapeutically leverage this mechanism, strategies to both pharmacologically inhibit FBXW7-CRLs and to exploit FBXW7 mutations occurring in human cancers are being developed. To address the former, pevonedistat (MLN4924), an agent which inhibits CRLs via inhibition of cullin-neddylation, inhibits FBXW7-mediated XRCC4 ubiquitination and NHEJ. This activity leads to increased sensitivity of tumor cells to chemotherapy and radiation and represents a strategy that may be particularly effective in cancers with other DSB repair defects. As another strategy to leverage the mechanisms of FBXW7 in NHEJ, loss-of-function mutations in the WD domain of FBXW7 which occur frequently in human cancers are being explored. These mutations render cells defective in NHEJ and more sensitive to DNA damage. Thus, we hypothesize that inhibition of other DSB repair pathways (e.g. alternative-end-joining) may be an effective therapeutic strategy for FBXW7 mutant cancers. These novel mechanisms of NHEJ regulation as well as their implications in the treatment of human cancers with an emphasis on pancreatic and colorectal cancers will be discussed. This work was supported by NIH grants R01CA163895, P50CA130810, R01CA118762, R01CA156744, and R01CA171277. Citation Format: Meredith Morgan. Exploiting the inhibition of cullin-RING-ligases in DSB repair as a therapeutic strategy [abstract]. In: Proceedings of the AACR Special Conference on DNA Repair: Tumor Development and Therapeutic Response; 2016 Nov 2-5; Montreal, QC, Canada. Philadelphia (PA): AACR; Mol Cancer Res 2017;15(4_Suppl):Abstract nr IA27.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".