Doxorubicin induces apoptosis with profile of large-scale DNA fragmentation and without DNA ladder in anaplastic thyroid carcinoma cells via histone hyperacetylation

Doxorubicin is known to be the most effective single cytotoxic drug against anaplastic thyroid carcinoma (ATC). Although doxorubicin has been shown to cause cell death, at least partly, by inducing apoptosis in ATC cells, the mechanism underlying its pharmacological efficacy has not been fully delineated. We, in this study, revealed that doxorubicin induced apoptosis in ATC cells by altering the acetylation state of histone. Doxorubicin reduced histone deacetylase activity and induced hyperacetylation of histone 3. Noticeably, ladder-like DNA fragments from their genomic DNA on agarose gel were not detected irrespective of several lines of evidence supporting the induction of apoptosis. Pulse field electrophoresis showed disintegration of nuclear DNA into giant fragments of 1-2 Mbp and high molecular-weight fragments of 100-1000 kbp. We next examined whether a histone deacetylase inhibitor trichostatin A (TsA) augmented doxorubicin-induced apoptosis in ATC cells. TSA potentiated doxorubicin-induced stage I apoptosis in ATC cells. Our study sheds light on the development of a new combination therapy strategy for more effective responses for ATC treatment.