Researchers have identified three possible mechanisms that trigger cancerous growth in cells and the most common hypotheses point to cellular DNA damage as the main culprit. This results in cells that have altered DNA, and hence, altered properties and have the potential to grow at a higher rate. Different factors such as excessive exposure to certain chemicals such as steroids or chemicals in asbestos, exposure to high doses of radiation or hormonal stress have been explained as the cause of the change in DNA composition. These factors can result in activation (or expression) of growth inducing oncogenes, alterations of genes that regulate apoptosis (programmed cell death), or inactivate tumor suppressor genes.
Since the 20th century, treatment options for malignant tumors have broadened from surgery (surgical removal of tumors), to chemodrugtherapy (use of anticancer drugs, often intravenously, to kill cancerous cells or reduce symptoms), and radiotherapy (application of gamma radiation to affective areas to destroy tumor cells) – and in some cases, all three of these options are combined.
The term chemotherapy was used as early as the first decade of the 20th century by the renowned microbiologist and physician, Paul Ehrlich. Originally an antimicrobial procedure, chemo drug therapy is now widely used to treat cancers. Chemotherapy for cancer treatment was carried out in the 1940s when some patients suffering from lymphoma were intravenously given sulfur mustard to observe its effect on their white blood cell count. The patients showed temporary recovery, which was considered a breakthrough and this promoted researchers to look for new chemical agents. Mustine (mechlorethamine) was subsequently discovered in 1942.
It is also worth mentioning that cancer chemo drug therapy can involve a combination of drugs (a cocktail of drugs). The original purpose of chemotherapy was to kill cancer cells through the use of cytotoxic drugs. This is called classical chemotherapy. Non-classical chemotherapy involves the use of antibodies that bind to specific proteins or biochemical factors that are either expressed by tumor cells or essential to their growth, or both. Canada Drugs Direct
This article will summarize the types of drugs used in chemotherapy (chemo drugs or anticancer drugs). Such drugs can be classified on the basis of chemical structure/action or on the basis of biological role/function. We will use the most commonly recognized categories (based on both properties).