Principles of Chemotherapy
Chemotherapeutic drugs act on fast diving cells by arresting the mitotic stages of cell cycle.
Cancer is characterized by the transformation of normal cells through uncontrolled division and growth. These malignant cells then spread to the other parts of the body by a process known as metastasis. In the case of
It has been deduced that the chemotherapeutic drugs act on the fast –dividing cells by arresting the various mitotic stages of cell cycle. Hence they are also called ‘cytotoxic’ drugs. These drugs are more effective in individuals with diseases characterized by fast-replicating cells, like
Chemotherapeutic drugs have a better impact on tumors that are ‘young’; in other words those that have a considerable population of differentiated cells. As the tumor ages, the cells loose their ability to differentiate. Such tumors become ‘indifferent’ to chemotherapeutic drugs. Radiation or surgery maybe a better option in this situation.
Some drugs bring about a semblance of orderliness in tumor cells by promoting ‘apoptosis’ or ‘programmed cell death’, which is a function of normal cells. This function is lost when the normal cells become malignant.
Scientists are now working on drugs that target specific features of the cancer cells. Imatinib, a monoclonal antibody drug, has been successful in attacking the Philadelphia chromosome, commonly seen in patients with CML. Efforts are on to identify more such features in order to develop efficient treatment modalities. Intracellular efflux pumps, such as p-glycoprotein, have been identified that actively flush out drugs from inside the cells to the outside. In the year 2007, medications that promote the efficacy of chemotherapy by impairing the functioning of p-glycoprotein have been tested.
Sometimes cytotoxic drugs may not discriminate between normal fast-dividing cells and the abnormal ones. They enter the blood stream and have a profound effect on the healthy cells too, resulting in side–effects. Examples are the hair cells and the cells that make up the intestinal lining, which are damaged during chemotherapy. However, the normal cells are able to revive due to an inherent repair mechanism and the symptoms usually disappear once the treatment terminates. To address this issue, doctors ‘mix and match’ drugs in order to provide the most suitable treatment.
Chemotherapy - References:
- MacDiarmid J.A. et al. (2007)
- "Bacterially Derived 400 nm Particles for Encapsulation and Cancer Cell Targeting of Chemotherapeutics" Cancer Cell 11, 431-445, May 2007