Cell cycle and cytostatics
The cell cycle is divided into four phases. In the S-phase, DNA is copied. Then the genetic material is split into two different cells during the division in the M-phase (mitosis). The G1 and G2-phase are phases of relative rest between synthesis and mitosis. The cell can escape for an undetermined period of time from the cell cycle by entering the dormant phase G0. Cytostatics act either in different phases of the cell cycle (mostly during the M and G2-phases) or throughout it.
- Alkylating agents are reactive and bind to DNA and proteins, thereby causing covalent cross-links between DNA strands. These cross-links inhibit the DNA replication process. This action is not phase dependent.
- Antimetabolites are metabolic products with small modifications that interfere in the biosynthesis or function of nucleic acids.
- Antimitotics affect the mitosis and synthesis of nucleic acids and proteins. Furthermore, these agents inhibit microtubule formation necessary for spindle formation.
- DNA strand breakage agents bind to DNA and form free radicals, thereby inhibiting synthesis of DNA or RNA and causing strand breaks.
- Topoisomerase inhibitors inhibit enzymes that are involved in unwinding of DNA and so prevent DNA repair and induce damage of DNA.
Cytostatics can be applied as curative, palliative and adjunctive therapy. Combinations of cytostatics are often used, because they can be more effective than a single cytostatic at maximal dose (synergy). Due to their effects on rapidly dividing cells, the adverse effects of cytostatics usually involve nausea, vomiting, myelosuppression, alopecia, and damage to mucosal epithelium.
The interphase of the cell life cycle is divided into:
Extra info: The interphase of the cell cycle, in which DNA replication occurs, includes all phases except the mitosis.
All of the following drugs are correctly matched with a major adverse effect, EXCEPT:
Extra info: Cardiomyopathy is a major adverse effect with doxorubicin treatment. Nephrotoxicity is an important side effect of cisplatin.
Which of the following statements is true?
Extra info: Most cytostatics act on the DNA in order to prevent replication; cisplatin acts directly on the DNA; 5-fluorouracil inhibits enzymes involved in the nucleotide synthesis.