Étude des voies de signalisation et des mécanismes moléculaires impliqués dans [l']apoptose des cellules leucémiques HL-60 traitées avec des inhibiteurs de topoisomérases I et II
Bibliographic record
Abstract
Chemotherapeutic agents, including camptothecin (CPI) and etoposide (VP1 6), which have been commonly used for cancer treatment for several years.Surprisingly, the exact molecular mechanisms of apoptosis activation induced by these drugs are flot fully characterized.In these studies, we have investigated the importance of some signaling pathways, including those associated with celi death receptors, the MAPKs and protein kinase Abi, in chemotherapy-induced apoptosis using' human leukemia celi unes as models.By indirect immunofluorescence and immunoperoxidase imaging and with gel filtration column chromatography, we observed rapid aggregation at the ceil surface and the appearance of high molecular weight protein complexes primarily involving DR3, DR3 and DR4 after CPI and VP16 treatment in HL-60 celis, respectively.Both drugs failed to rapidly promote FAS aggregation in these ceils.In parallel, the expression level of DR3, DR4 and FAS remained mostly unchanged, while the expression of SODD and FLIP5, inhibitors of the ceil death receptor signaling pathways, decreased substantially 4 h after drug treatment.However, the high expression level of SODD or of dominant negative forms of FADD (FADD-DN) and DAP3 (DAP3-DN), or of the N-terminal deletion mutant of IRADD (IRADD-ND), achieved by transient transfection experiments, did not impair the kinetics of apoptosis after CPI and VP16 treatment in HL-60 and U937 ceils.Iaken together, these observations suggested that CPI and VP 16 induced rapid aggregation of DR4 and DR3, but paradoxically, the importance of these events in signaling apoptosis is uncertain, because the kinetics of apoptosis were unaffected, even in the presence of a high expression level of SODD, FADD-DN, IRADD-ND and DAP3-DN.However, CPI or VP16 treatment in combination with TRML, a DR4 and DR5 ligand, substantially accelerated the kinetics of apoptosis more than treatment with CPI, VP16 or IRAIL alone.In contrast, co-treatment of CPI or VP16 with IWEAK or IL1A, putative DR3 ligands, did not facilitate apoptosis in HL-60 ceils.Ihese fmdings suggest that DR4 aggregation mediated by CPI or VP16 could represent a mean that accelerates TRAIL-induced apoptosis (Bergeron et aï.Mol Cancer Ther 2004, 3(12):1-11).Investigating the importance of the MAPK pathways, we found that both drugs failed to activate MKK3, MKK4 and JNK kinases while p38 was rapidly activated following CPI or VP16 treatment in HL-60.p38 activation appears to be independent of ceil death receptor signaling pathways since it was flot impaired by overexpression of fADD-DN or TRADD ND.In addition, celis treated with CPI in the presence of p38 inhibitors showed increased DNA fragmentation associated with apoptosis compared to celis treated with CPI only.Ihese resuits suggest that p38 activation is coupled to antiapoptotic or survival signaling in CPT-treated ceils.The significance of p38 activation in VP16-treated celis remains enigmatic.In parallel, expression of hcB(SR), an inhibitor of NF-KB activation, increased the kinetics of DNA fragmentation in CPI-treated celis.These resuits indicate that NF-icB activation could be involved in antiapoptotic or survival signaling in HL-60 ceils, in a way similar to that mediated by p38.However, the relationship between p38 and NF-cB activation remains to be investigated.AbI is rapidly activated by both drugs, and HI-60 ceils treated with Abi inhibitor showed reduced kinetics of DNA fragmentation in CPT-treated ceils, whule no DNA fragmentation variation was observed afier VP16 treatment.Thus, Abi activation appears to be associated with signaling that favours CPI-induced apoptosis in these ceils.However, the presence of PKC-inhibitor and of the natural isoforms of p73 and p63 ffiat show N-terminal deletions winch act as dominant negative forms (zs.Np73Œ-t3; ANp63a-), does flot impair the kinetics of apoptosis induced by CPI in HI-60 ceils.Ihese resuits suggest that Abi signaling afier CPI treatment acts independently ofthese pathways.Ihe work presented here indicates that HL-60 ceils treated with CPI or VP1 6 simultaneously induce different signaling pathways.Indeed, Abi activation leads to signaling that accelerates CPI-induced apoptosis in these cancer celis.In parallel, p38 and NF-icB activation is involved in survival signaling that reduces the kinetics of CPI-induced apoptosis in HI-60 celis.Finally, celi death receptor signaling pathways could act as an alternative mechanism or amplification ioop, and accelerate the kinetics of apoptosis in combined treatment involving IRAIL with CPI or V? 16.
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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 | 0.001 |
| 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 | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 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".