Abstract 6321: BEND3 modulates sensitivity to the UBA1 inhibitor TAK-243 by regulating expression of the multidrug transporter BCRP
Bibliographic record
Abstract
Abstract TAK-243 (MLN7243) is a first-in-class inhibitor of the ubiquitin-activating enzyme (UBA1) that catalyzes the first step in the ubiquitylation cascade whereby proteins are tagged with mono- or poly-ubiquitin to induce their degradation or modify their functions. Based on its preclinical efficacy and tolerability, TAK-243 has entered phase 1 clinical trials in advanced malignancies. However, the determinants of sensitivity to TAK-243 remain largely unknown. Therefore, we conducted a positive-selection, genome-wide CRISPR/Cas9 knockout screen in OCI-AML2 cells followed by selection with lethal TAK-243 concentrations to identify genes essential for TAK-243 action. We identified BEN domain-containing protein 3 (BEND3), a transcriptional repressor and a regulator of chromatin organization, as the top gene whose knockout conferred resistance to TAK-243 (FDR = 0.0012). BEND3-targeting gRNAs were enriched up to 10,000-fold after selection with the drug. To validate the screen results, we independently knocked out BEND3 in OCI-AML2 cells and confirmed the resistance phenotype. In vivo, tumors of BEND3-knockout cells were resistant to TAK243 (20 mg/kg twice weekly) as opposed to control tumors that showed dramatic reductions in tumor growth rate. As assessed by immunoblotting, BEND3 knockout dampened TAK-243 effects on ubiquitylation, proteotoxic stress and DNA damage response. Mechanistically, BEND3 knockout upregulated the ABC efflux transporter breast cancer resistance protein (BCRP; ABCG2), and decreased intracellular levels of TAK-243. It also conferred partial cross-resistance to pevonedistat and TAK-981–related selective inhibitors of the NEDD8-activating enzyme (NAE) and the SUMO-activating enzyme (SAE), respectively, as well as known substrates of BCRP (mitoxantrone and doxorubicin). Finally, TAK-243 sensitivity strongly correlated with BCRP expression in a panel of 30 cancer cell lines of different origin, and chemical inhibition of BCRP but not P-gp sensitized intrinsically resistant high-BCRP cells to TAK-243. Thus, our data demonstrate that BEND3 regulates the expression of BCRP for which TAK-243 is a substrate. Moreover, BCRP expression could serve as a predictor of TAK-243 sensitivity. Citation Format: Samir H. Barghout, Ahmed Aman, Zachary Blatman, Karen Arevalo, Geethu Thomas, Neil MacLean, Xiaoming Wang, Rose Hurren, Troy Ketela, Moustafa Abohawya, Taira Kiyota, Rima Al-Awar, Aaron D. Schimmer. BEND3 modulates sensitivity to the UBA1 inhibitor TAK-243 by regulating expression of the multidrug transporter BCRP [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6321.
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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) | 0.000 | 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 | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 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".