Endonuclease activity and hydrogen peroxide-induced cytotoxicity in human glioblastoma and glioma cell lines

Hydrogen peroxide (H2O2) induced internucleosomal DNA cleavage in human mye logenous leukemic cell lines (HL-60, ML-1, THP-1, U-937), but not in human glioblastoma (T98G, U87MG) and glioma (KG1C) cell lines. However, H2O2 prod uced apoptotic cells, characterized by cell shrinkage, nuclear fragmentatio n and chromatin condensation in glioblastoma and glioma cell lines. Autodig estion experiments revealed that the major endonucleases, present in all le ukemic, glioblastoma and glioma cell lines, were divalent cation-independen t endonuclease(s). The endonuclease(s) present in the lysates of all these cells were activated at acidic, but not at neutral pH. The results suggest that the endonuclease activity might be differently regulated between leuke mic and glioma cell lines.