P10.07 Sialate O-acetylesterase (SIAE) over-expression leads to a collapse of the mitochondrial membrane potential and predisposes cells to etoposide treatment in RES256 medulloblastoma cells
Bibliographic record
Abstract
Medulloblastoma is the most common malignant paediatric brain tumour and is the leading cause of childhood cancer related mortality. Current treatment includes maximal safe surgical resection, radiotherapy if the patient is over 3 years of age, and high-dose chemotherapy that usually includes methotrexate, cisplatin, etoposide, vincristine, lomustine and cyclophosphamide. Survivors often suffer significant treatment-related sequelae including endocrine disorders and neurocognitive deficits that negatively impact quality of life. GD3, an oncofoetal ganglioside is re-expressed in medulloblastoma and is thought to be associated with mitochondrially-mediated apoptosis. 9-O-acetyl GD3 (GD3A), its acetylated form, has been shown to protect cells from GD3-mediated apoptosis. Sialate-O-acetylesterase (SIAE) is responsible for cleaving the acetyl group from GD3A. A genome-wide transcriptional analysis of 103 MB patients revealed that this enzyme is significantly down-regulated in MB tissue compared to non-neoplastic foetal and adult brain (p>0.02). To determine if this pathway may serve as a potential therapeutic target we used a well described tet-responsive inducible expression system. SIAE and a mutant of that has been shown to have very little catalytic activity (SIAE-S127A) were expressed in the RES256 cell line. SIAE and SIAE-S127A expression was verified by Western blot analysis after 48 hours of induction with low levels of doxycycline. SIAE expression was also confirmed by SIAE-S127A expressing RES256 cells in conditioned media, but was not secreted by wild-type expressing cells. Over-expression of SIAE showed a significant increase in GD3 expression (p<0.05), and a significant increase in depolarisation of the mitochondrial membrane potential (p<0.05). These changes were not seen on induction of expression of a catalytic mutant SIAE-S127A which has been shown to have almost no catalytic activity, nor by vector controls. With induction of SIAE expression and with etoposide treatment there was a significant reduction in IC50 in SIAE overexpressing clones after 48 hours (p<0.01). After 72 hours of treatment there was a reduction in IC50 (p<0.001). In SIAE-S127A expressing cells there was also a significant reduction in IC50 after 72 hours of treatment (p<0.05). Changes in IC50 for empty vector controls were not significant (p>0.05). Our results suggest that SIAE over-expression leads to a collapse of the mitochondrial membrane potential in RES256 cells. Additionally, these results suggest that SIAE over-expression may sensitize cells to chemotherapeutics, potentially reducing side-effects.
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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".