The effect of Irinotecan on HMGB proteins in MCF-7 cells

Irinotecan is a semisynthetic analog of camptothecin, widely used in cancer therapy such as colorectal, lung and breast cancer. It binds to DNA-Topo-I complex and induces break in DNA inhibiting transcription and replication. High mobility group box (HMGB) proteins are the largest group of nonhistone chromosomal proteins that participate in replication, transcription and its translocation from the nucleus to extracellular space is a marker of necrosis in tumor cells. In this study we focused on the effect of irinotecan on HMGB proteins in MCF-7 cells. The cells were incubated in the absence and presence of various concentrations of irinotecan and viability determined by trypan blue and MTT assay. The results showed that irinotecan exhibited time and dose dependent cytotoxicity on the cells. HMGB proteins were extracted by salt and analyzed on SDS-PAGE and immunoblot. Also HMGB release to medium was investigated by western blot. The results revealed that, the content of HMGB proteins decreased on the gel upon increasing irinotecan concentration as western blot against HMGB antibody confirmed it, however HMGB release was not detected in the cells treated by the drug. From the results it is concluded that reduction of HMGB content is not related to HMGB release from the cells, but possibly binging of the drug to chromatin and HMGB condenses the chromatin somehow that HMGB proteins can not be extracted by manual procedures.

Keywords:

Irinotecan , HMGB , MCF-7 cells