Quiz 45: Antineoplastic Agents
The term 'cancer' refers to that disease condition which involves the development and reproduction of abnormal cells. The first finding in cancerous cells is that there occur changes in the structure of the cell irrespective of the type of cell. The type of cell can be epithelial, smooth or muscle and along with changes the function of cells is also lost. The second finding is that it is possible to control the growth and reproduction of normal cells but the reproduction of cancer cells is indefinite and uncontrollable. Due to this tumours having no defined function are produced. These tumours are also referred to as neoplasm. Sometimes the reproduction of these cells is at very fast rate as compared to normal cells. This leads to emergence of malignant or life-threatening tumour.
The combination therapy used in the cancer treatment involves the use of two or more anti-cancer drugs. The combination therapy is chosen because of the advantages it offers that increases the efficacy of the drugs involved in the treatment. The most important advantage is that it decreases the chances of development of drug resistance. This is because there is less probability of pathogen or the tumour being resistant to multiple drugs at the same time. The other advantage is that there is an increased chance that all the cancer cells would be eliminated by the use of combination of drugs. This is because different anti-cancer drugs are known to affect the cells affected by the cancer at different points in the cell cycle.
Carmustine is an anti-neoplastic agent. It is highly lipophilic and belongs to the class of nitrosoureas. It can cross the blood-brain barrier very easily due to its highly lipophilic nature. It is administered as an intravenous injection and used in the treatment of several forms of cancers such as brain tumors, leukemias, lymphomas (both Hodgkin's and non-Hodgkin's disease), breast and ovarian cancers, testicular cancers, etc. Carmustine is an alkylating agent that alkylates and causes cross-links in DNA which leads to DNA damage and disruption of cell cycle and division. This results in apoptosis (cell death). It also causes carbamoylation of the proteins that are involved in DNA repair enhancing the cytotoxic effect. They are not restricted to any particular phase of the cell cycle and inhibits cell growth in all phases of the cell cycle. The antimetabolites are the drugs that act inhibit cell cycle by interfering at the S-phase of the cell cycle and are cell cycle-specific. Hence, the option A is not the correct answer. Hormone antagonists are drugs that inhibit the action of hormones that increase the growth of cancer cells. The hormone antagonists do not interfere with the cell cycle and hence are not cytotoxic. Hence, the option C is not the correct answer. Mitotic inhibitors are the drugs that act at the mitotic phase of the cell division and inhibit the cell cycle and cell growth. They are cell cycle-specific. Hence, the option D is not the correct answer. Monoclonal antibodies are the drugs that act by binding to certain growth receptors that are present on the surface of the cells. They are not dependent on the cell cycle for their inhibitory activity. Hence, the option E is not the correct answer. The alkylators are the drugs that alkylate the DNA by forming a covalent bond with DNA and inhibits the synthesis of proteins and other essential cell components. They can act at any phase of the cell cycle and inhibits cell growth. Since carmustine alkylates and creates cross-links in DNA, and can act at any phase of the cell cycle, it is an alkylator. Hence, the option B is the correct answer.