In vitro single-strand DNA damage and cancer cell cytotoxicity effects of Temozolomide

Abstract

Temozolomide (TMZ) is approved against certain tumors, but substantial evidences are scarce to demonstrate TMZ as single-strand DNA break agent and reasons behind lack of responses in carcinoma. Plasmid and genomic DNA included as a substrate during assessment of in vitro single-strand break potential of TMZ. Cell based assay was performed to assess DNA damaging activity and cytotoxicity in HeLa. Further, authors tried to evaluate DNA damage and overall cytotoxicity in HeLa using Trypan blue dye exclusion and apoptotic DNA fragmentation assays. Data indicate that TMZ can generate extensive single-strand break on different DNA substrate. A DNA ligase inhibitor L189 appears to plays synergistic role in TMZ ability to decrease cell proliferation in HeLa and some extent of cytotoxicity. However, authors noticed none apoptotic DNA fragments due to toxicity effects of TMZ alone or combined TMZ plus L189. Based on our observations, findings support combined use of TMZ and L189 inhibitor to enhance responsiveness in HeLa possibly by decreasing cellular growth instead of apoptotic cell death pathway.

Dual Reactive Oxygen Species Generator Independent of Light and Oxygen for Tumor Imaging and Catalytic Therapy

“…To explore the specific mechanism of ROS-induced cell apoptosis, we conducted a plasmid DNA nicking assay to determine the DNA cleavage activity of MnSMH NPs. [39][40] Under the trigger of ROS, damaged supercoiled DNA could transform into a nicked form with a single-strand break and a linear form, which could be distinguished by agarose gel electrophoresis due to their different electrophoretic mobilities. As shown in Figure 5f 6c, the MnSMH NPs were principally accumulated in the liver after intravenous injection owing to capture by the reticuloendothelial system.…”