Anti-Cancer Drugs

Anti-Cancer Drugs

Cells are pretty amazing when you think about it. Scientists believe that your body produces about two trillion new cells every day. These cells are identical to the original cell and contain the same DNA sequence. But sometimes, the DNA isn't copied correctly, which can cause the new cell to act differently. When a cell starts dividing rapidly and uncontrollably, that's called cancer. It's a disease that happens when cells in a certain part of your body grow out of control.

The good news is that there are lots of drugs that can help fight cancer. In this article, we'll focus on one of those drugs: cisplatin. We'll talk about what it does and how it works. We'll also look at some of its side effects. You don't need to know about other anti-cancer drugs or cancer itself for your exams, but we've included that information to give you some background knowledge on the subject.

What is cancer?

Cancer is a disease that happens when cells divide rapidly and uncontrollably. Healthy cells divide regularly as part of the cell cycle, which is regulated by security measures that tell them when to divide and when to perform other cellular activities. However, in cancerous cells, these security measures are either missing or faulty. This uncontrolled cell division is caused by mutations in the cell's DNA, which can come from many sources including carcinogenic substances like x-rays. Because cancerous cells grow faster than normal cells, they can invade and destroy healthy tissue, including organs. This is why cancer is so dangerous and can be life-threatening. If you want to learn more about this topic, check out our article on Cancer.

What are anti-cancer drugs?

Anti-cancer drugs are used to treat cancer in the body. This treatment method is called chemotherapy and it's used in 28 percent of all cancer cases. Some forms of cancer can be up to 90 percent successfully treated with chemotherapy. There are different types of anti-cancer drugs that work in different ways depending on their classification. They also have different side effects and dosages, and are used to treat different types of cancer. Doctors must consider all these factors when prescribing anti-cancer drugs to their patients.

Classification of anti-cancer drugs

There are several types of anti-cancer drugs available for treating cancer. Alkylating agents work by disrupting the DNA replication process of cancerous cells. They do this by either cross-linking DNA strands or pairing up DNA base pairs abnormally. Antimetabolites interfere with the enzymes involved in DNA synthesis. Hormonal agents alter the hormone levels around the cancerous cell, which affects its cellular division. Plant alkaloids bind to specific proteins during certain stages of the cell cycle, causing the cancerous cell to enter mitotic arrest and die. Each type of anti-cancer drug has its own mechanism of action and targets specific types of cancer. Doctors must evaluate the patient's cancer type and stage, as well as any possible side effects, to determine which type of anti-cancer drug to use.


Cisplatin is a particular anti-cancer drug. To be exact, it is a type of alkylating agent. For the rest of this article, we're going to look specifically at how it works in treating cancers.

Cisplatin as an anti-cancer drug

Cisplatin is an example of an alkylating agent, which is a type of anti-cancer drug. It works by interfering with DNA replication, which ultimately prevents the cancerous cell from dividing. It's important to note that DNA replication is different from cell division. DNA replication is the process of copying the parent DNA to produce a new set of DNA within the cell, while cell division is when the cell splits into two daughter cells. However, DNA replication is a crucial step in cell division and is necessary for the cell to divide properly. To learn more about these topics, you can refer to resources such as "Cell Division" and "DNA Replication" which provide a good introduction to these topics.


Cisplatin has the molecular formula . It is an example of a complex ion with two chloride ligands and two ammonia ligands bonded to a central platinum atom. By looking at the term ‘cisplatin’, we can visualise its structure. Cisplatin is actually one of a pair of two optical isomers, molecules with the same structural formulae but different arrangements of groups around a central atom. In the cis- isomer, the chloride ligands are next to each other. In the trans- isomer, they are opposite one another.

Cisplatin and transplatin. The chloride ligands are circled to help you identify their position
Cisplatin and transplatin. The chloride ligands are circled to help you identify their position

The shape of cisplatin is a square planar. The cis- structure and the square planar shape of cisplatin give it the correct geometry that is fundamental to its function. We cover these types of isomers in more detail in the article Optical Isomerism. If you want to learn about molecular shapes, check out Shapes of Molecules.

Mechanism of action

The structure of cisplatin is important in how it functions as an anti-cancer agent. When cisplatin enters the body, it undergoes an aquation reaction where water replaces one of the chloride ligands. This reaction occurs due to the high concentration of water around the cisplatin ion compared to the concentration of chloride ions.

The aquated cisplatin molecule can then bind to DNA bases, specifically guanine. The nitrogen atom in guanine donates its lone pair of electrons to the platinum ion in cisplatin, forming a dative covalent bond. This process leads to the displacement of the water ligand in another ligand substitution reaction.

Nitrogen can replace water in the ligand substitution reaction because it is a stronger ligand than oxygen. Nitrogen holds its lone pair of electrons less tightly than oxygen, which is more electronegative than nitrogen. The same substitution reaction takes place for the other chloride ligand, but this time the chloride ligand is replaced by a nitrogen atom from guanine on the opposite DNA strand. The binding of cisplatin to guanine cross-links the two DNA strands and distorts the shape of the DNA. This distortion prevents the cell from replicating its DNA, and the cell tries to repair the DNA damage using repair mechanisms but ultimately fails. This triggers apoptosis, cell death. Overall, the structure of cisplatin allows it to effectively bind to DNA and prevent cancerous cells from dividing, ultimately leading to cell death.

Cisplatin binds to guanine bases on opposite DNA strands
Cisplatin binds to guanine bases on opposite DNA strands

Cisplatin can only bind to both strands of DNA because its chloride ligands are positioned on the same side of the platinum ion. In contrast, transplatin can't bind to DNA because its chloride ligands are on opposite sides of the platinum ion. This means it can't stop DNA replication and is completely ineffective as an anti-cancer drug.

Side effects

It is important to note that although cisplatin is not selective and can bind to DNA in all cells, not just cancer cells, it is still a valuable tool in treating cancer. Chemotherapy can be a crucial treatment option for some individuals, and the benefits of cisplatin in particular, such as its high success rate against testicular cancer, should not be overlooked.

While side effects like hair loss, nausea, vomiting, and fatigue can be challenging, they can be managed through medications and other forms of support. Ultimately, the decision to undergo any form of cancer treatment should be made by the patient, with the guidance and support of their healthcare team.

Anti-Cancer Drugs

What are the most common cancer drugs? 

In addition to cisplatin, the most common cancer drugs include vincristine, paclitaxel, and methotrexate. 

What are the classifications of anti-cancer drugs?

There are many classes of cancer drugs. These include alkylating agents, antimetabolites, and hormonal agents.

How do anti-cancer drugs work?

Cancer drugs work in different ways. They mainly work by stopping the cancer cells from further dividing, though different cancer drugs stop the cell division process differently. For example, cisplatin kills cancer cells by stopping them replicating their DNA and triggering cellular death.

What is an anti-cancer drug?

An anti-cancer drug is a drug used to treat cancers.

Can anti-cancer drugs cause cancer?

Unfortunately anticancer drugs can bring about the risk of further cancers developing, as they can also act on non-cancerous cells. Therefore, anti-cancer therapy is very stringently monitored to help prevent such risk from occurring.

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