Abstract SSY01-03: An RNAi screen identifies a heme biosynthetic mediator as a novel radiosensitizing target for head and neck cancer
Bibliographic record
Abstract
Abstract Introduction: Head and neck cancer (HNC) is a challenging disease due to its heterogeneity and complexity. Despite continued advances in therapeutic options, treatment-associated toxicities and overall clinical outcomes have remained disappointing. Even with radiation therapy (RT), which remains the primary curative modality for HNC, the most effective regimens achieve local control rates of 50-70%, with disease free survival rates of only 30-40% for patients with locally advanced HNSCC. Thus, the development of novel strategies to enhance tumor cell killing, while minimizing damage to the surrounding normal tissues, is critical for improving cure rates with RT. Methods: A siRNA-based high-throughput screen (HTS) was performed for the large-scale identification of novel genes that will selectively sensitize HNC cells to ionizing radiation (IR). The Dharmacon Protein Kinase and Druggable Genome siRNA Libraries were screened using FaDu cells (human hypopharyngeal squamous cell cancer). Radiosensitizing targets were subjected to functional validation studies and in vitro characterization of mechanisms for radiosensitization. In vivo validation studies including tumor formation assays and the treatment of established HNC xenograft models were also conducted. Results: The HTS identified 67 target sequences with potential radiosensitizing effects; the validity of the screen was corroborated by the identification of known radiosensitizing targets (e.g. ATM, ATR, AURKA). Targets reducing the surviving fraction by >50% at 2 Gy relative to their un-irradiated counterparts were selected for further evaluation. A key regulator of the heme biosynthetic pathway was thus identified as a novel tumor-selective radiosensitizing target. Down-regulation of the enzyme plus IR induced caspase-mediated apoptosis and cell cycle arrest in vitro, while delaying tumor growth in vivo. Radiosensitization appeared to be mediated via enhancement of tumor oxidative stress from perturbation of iron homeostasis and increased reactive oxygen species production. This radiosensitizing target was significantly over-expressed in HNC patient biopsies, wherein lower pre-RT mRNA levels correlated with improved survival, suggesting that this enzyme could also be a potential predictor for radiation response. Down-regulation of the enzyme also radiosensitized several different human cancer models, while sparing normal cells. Conclusion: We have successfully developed an RNAi-based radiosensitizer HTS, and uncovered a key regulator of heme biosynthesis as a potent sensitizer for RT, with potentially broad implications in the management of many human malignancies. Citation Format: Emma Ito, Shijun Yue, Eduardo H. Moriyama, Angela B. Hui, Inki Kim, Wei Shi, Nehad M. Alajez, Nirmal Bhogal, GuoHua Li, Alessandro Datti, Aaron D. Schimmer, Brian C. Wilson, Peter P. Liu, Daniel Durocher, Benjamin G. Neel, Brian O'Sullivan, Bernard Cummings, Rob Bristow, Fei-Fei Liu. An RNAi screen identifies a heme biosynthetic mediator as a novel radiosensitizing target for head and neck cancer [abstract]. In: Proceedings of the AACR 101st Annual Meeting 2010; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr SSY01-03
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 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 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
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 teacher head, 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".