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Anticancer drug-induced apoptosis in human monocytic leukemic cell line U937 requires activation of endonuclease(s)
P Shrivastava1, A Sodhi, P Ranjan
1School of Biotechnology, Banaras Hindu University, Varanasi, India.
Abstract:
Anticancer agents effect tumor cell killing both in vivo and in vitro through the induction of apoptosis. Endonuclease-mediated internucleosomal DNA fragmentation, the most widely used biochemical marker of apoptosis, has been shown to play a central role in apoptosis in many experimental systems. In the present investigation, we report that activation of endonuclease(s) leading to oligonucleosomal DNA fragmentation is common and an essential event in apoptosis, induced by different anticancer drugs, adriamycin, etoposide and cisplatin. The endonuclease inhibitors aurintricarboxylic acid and zinc ion prevented apoptotic cell death in human monocytic leukemic cell line U937, as documented by DNA fragmentation, morphological and nuclear alterations, and cell viability assay. Additional studies suggest endonuclease(s)-mediated DNA fragmentation may not play a central role in apoptosis in the same cell line in response to other inducers such as heat shock and cells may undergo cell death showing all morphological features of apoptosis even in the absence of DNA fragmentation.
Insights
Anticancer drugs induce apoptosis, a programmed cell death, by triggering DNA fragmentation. Inhibiting this DNA fragmentation prevents cancer cell death, but apoptosis can still occur without it in response to other stimuli.
Area of Science:
- Biochemistry
- Molecular Biology
- Cell Biology
Background:
- Apoptosis, or programmed cell death, is crucial for tumor cell elimination by anticancer agents.
- Endonuclease-mediated internucleosomal DNA fragmentation is a widely recognized marker of apoptosis.
- The role of DNA fragmentation in drug-induced apoptosis requires further elucidation.
Purpose of the Study:
- To investigate the role of endonuclease-mediated DNA fragmentation in apoptosis induced by anticancer drugs.
- To determine if DNA fragmentation is essential for anticancer drug-induced cell death.
- To explore alternative pathways of apoptosis in the absence of DNA fragmentation.
Main Methods:
- Induction of apoptosis in human monocytic leukemic cell line U937 using anticancer drugs (adriamycin, etoposide, cisplatin).
- Inhibition of endonuclease activity using aurintricarboxylic acid and zinc ions.
- Assessment of DNA fragmentation, morphological changes, nuclear alterations, and cell viability.
Main Results:
- Anticancer drugs commonly induced endonuclease activation and oligonucleosomal DNA fragmentation.
- Inhibition of endonuclease activity prevented apoptotic cell death, confirming DNA fragmentation's role.
- Heat shock induced apoptosis with morphological features of cell death but without significant DNA fragmentation.
Conclusions:
- Endonuclease-mediated DNA fragmentation is a common and essential event in apoptosis induced by anticancer drugs.
- While DNA fragmentation is critical for drug-induced apoptosis, alternative apoptotic pathways exist, as demonstrated by heat shock induction.