Related Experiment Videos
Reduced DNA ligase activity in etoposide resistant human lymphatic leukaemia CEM cells
Eva Fredriksson1, Eva Liliemark, Anya Polischouk
1Institute of Environmental Medicine, Karolinska Institutet, P.O. Box 210, SE-171 77, Stockholm, Sweden.
Abstract:
Drug resistance is an obstacle preventing success of cancer chemotherapy. Resistance of vaccinia virus towards the topoisomerase II (topo II) targeting anti-cancer drug etoposide has been mapped to the viral DNA ligase gene. The present study was performed to elucidate if the DNA ligase activity, besides topo II levels, was altered in human lymphatic leukaemia cell strains with different levels of etoposide resistance. At measurements of DNA ligase activity with specific substrates, to distinguish between different DNA ligases, a reduced DNA ligase activity was observed in the resistant substrains. In contrast, the initial step of the ligation process, formation of DNA ligase--AMP complex, did not decrease in the resistant cell strains, suggesting an alteration in a later reaction leading to a deteriorated DNA ligation. The results suggest that decreased DNA ligase activity, besides topo II alterations, may contribute to etoposide resistance of the investigated CEM cells. The relevance of this finding will be further investigated.
Insights
Drug resistance in cancer chemotherapy can be overcome by understanding etoposide resistance mechanisms. This study reveals that reduced DNA ligase activity in CEM cells contributes to etoposide resistance, alongside topoisomerase II alterations.
Area of Science:
- Biochemistry
- Molecular Biology
- Cancer Research
Background:
- Drug resistance is a major challenge in cancer chemotherapy.
- Etoposide, a topoisomerase II (topo II) targeting drug, faces resistance, often linked to the viral DNA ligase gene in vaccinia virus.
- Understanding resistance mechanisms in human cancer cells is crucial for improving treatment efficacy.
Purpose of the Study:
- To investigate alterations in DNA ligase activity in human lymphatic leukaemia cell strains with varying etoposide resistance.
- To determine if DNA ligase activity changes contribute to etoposide resistance in CEM cells.
Main Methods:
- Assessing DNA ligase activity using specific substrates to differentiate between various DNA ligases.
- Measuring the formation of the DNA ligase-AMP complex to evaluate the initial ligation step.
Main Results:
- A significant reduction in DNA ligase activity was observed in etoposide-resistant human leukaemia cell substrains.
- The initial step of DNA ligation (DNA ligase-AMP complex formation) remained unaffected in resistant cells.
- These findings suggest a defect in a later stage of the DNA ligation process.
Conclusions:
- Decreased DNA ligase activity may play a role in etoposide resistance in CEM cells.
- This reduced activity, in addition to potential topoisomerase II alterations, could be a contributing factor to chemotherapy resistance.
- Further investigation is warranted to fully elucidate the clinical relevance of these findings.