A single d(GpG) cisplatin adduct on the estrogen response element decreases the binding of the estrogen receptor

Cisplatin-Induced Nephrotoxicity; Protective Supplements and Gender Differences

Cisplatin (CDDP) has been widely used as a chemotherapeutic agent for solid tumors. The most common side effect of CDDP is nephrotoxicity, and many efforts have been made in the laboratory and the clinic to employ candidate adjuvants to CDDP to minimize this adverse influence. Many synthetic and herbal antioxidants as well as trace elements have been investigated for this purpose in recent years and a variety of positive and negative results have been yielded. However, no definitive supplement has so far been proposed to prevent CDDP-induced nephrotoxicity; however, this condition is gender related and the sex hormone estrogen may protect the kidney against CDDP damage. In this review, the results of research related to the effect of different synthetic and herbal antioxidants supplements are presented and discussed with suggestions included for future work.

HMGA1 enhances the transcriptional activity and binding of the estrogen receptor to its responsive element

The estrogen receptor (ER) plays a critical role in the development of hormone-dependent cancer. Since HMGA1, a member of the "high mobility group" proteins, is overexpressed in certain malignant cells, we investigated the interaction between these nuclear proteins. Transfection of the HMGA1 expression vector increased 2-fold the transcriptional activation of ERE containing promoter by E(2). Furthermore, the HMGA1 protein stimulated severalfold the binding of purified ER to the consensus ERE oligonucleotides in gel mobility shift assays and saturation assays. However, HMGA1 could not bind alone either to consensus or to modified EREs, and the minor groove binding drug distamycin A failed to prevent the synergism between ER and HMGA1. This could suggest that the binding of HMGA1 to DNA was not required for its stimulatory effect. Antibody supershift assays showed that HMGA1 was required for increased binding and suggest a protein-protein interaction between those factors. This was confirmed by pull down assay. These data show that HMGA1 acts in concert with the ER to regulate the expression of estrogen responsive genes through a mechanism that does not require direct binding to DNA. These observations may be relevant in malignant cells expressing both proteins.

Recognition of cisplatin adducts by cellular proteins

Cisplatin is a widely used chemotherapeutic agent. It reacts with nucleophilic bases in DNA and forms 1,2-d(ApG), 1,2-d(GpG) and 1,3-d(GpTpG) intrastrand crosslinks, interstrand crosslinks and monofunctional adducts. The presence of these adducts in DNA is through to be responsible for the therapeutic efficacy of cisplatin. The exact signal transduction pathway that leads to cell cycle arrest and cell death following treatment with the drug is not known but cell death is believed to be mediated by the recognition of the adducts by cellular proteins. Here we describe the structural information available for cisplatin and related platinum adducts, the interactions of the adducts with cellular proteins and the implications of these interactions for cell survival.