Doxorrubicin
Doxorrubicin comes from the bacterium Streptomyces peucetius, so it is an anthracycline tumor antibiotic. This drug spoils DNA and, therefore can destroy abnormal cells. Doxorrubicin should be administered intravenously, usually every 21 or 28 days.
It is formed by a tetracyclic ring (each ring, called A, B, C and D) plane and by variable side chains. It has two central rings (the B and the C), these have quinone and hydroquinone groups. These groups act as donors or electron receiver and are capable of forming other radicals.
Doxorrubicin works by altering DNA in cells, usually in phase S and in phase G2. It is inserted between the nitrogenous bases of the DNA, this implies important changes. That is, it does not allow the synthesis of DNA, because the Topoisomerase II is inhibited. Consequently, it is not possible to synthesize RNA or proteins. In addition, when joining the doxorubicin with free radicals and DNA, it breaks.
Also, it alters the cell membrane and is able to activate proteins that inhibit the transduction of signals, for example, kinase C. Finally, it induces apoptosis.