Home » Pet Health » Genes and Cancer » How Do Mutations Lead to Cancer?


Hundreds of genes work together to control cell growth, repair, and death. When a cell divides, it creates two new cells called daughter cells, which receive copies of the DNA from the original cell. Copying and creating new DNA is a highly controlled and regulated process. However, the process is still prone to errors, which may lead to DNA mutations.

Gene mutations may occur when:

    • Your pet carries a gene mutation from birth which could either be inherited from a parent or developed when it was in an embryo.
    • Your pet encounters something that damages the genes, like UV radiation or different kinds of herbicides and pesticides.
    • Your pet’s genes wear out and either lose their function or function defectively as your pet ages.

Under normal circumstances, the cell’s DNA repair proteins detect correct mutations. If the mutations go unrepaired, the cells receive signals to die through a process known as programmed cell death. However, if a cell has a defective repair mechanism, the mutation may go unnoticed, and the affected cells escape cell death. Avoiding programmed cell death is the hallmark feature of cancerous cells since the cells with damaged DNA survive and divide uncontrollably.

Cancer genes that control cell growth and can cause cancer are divided into three main categories:

    1. Proto-Oncogenes & Oncogenes: Proto-oncogenes are a class of genes responsible for turning normal cells cancerous when they are mutated. The mutated version of a proto-oncogene is called an oncogene. Proto-oncogenes and oncogenes function as on/off switches. Usually, a proto-oncogene is switched off; however, when it is switched on, it triggers cell growth by directing a cell to grow or divide. Oncogenes are always on, leading to uncontrolled cell growth, causing cancer.
    1. Tumour suppressor genes (TSGs): TSGs are normal genes that protect your pet against cancer by slowing down cell growth and division, repairing mistakes in DNA, and directing them to die in case of abnormal growth. Mutations in these genes cause the cells to grow out of control, causing cancer.
    1. DNA repair genes: DNA repair genes play a vital role in fixing genetic mistakes when DNA copies during multiplying. When the genes are mutated, correcting errors in oncogenes and tumor suppressor genes is more challenging, leading to cancer development.

Not all individuals carrying a cancer-causing gene mutation will develop cancer. For instance, two pups (or kittens) from the same parents could inherit the same gene mutation. Still, only one offspring may develop cancer because cancer-causing mutations carry different levels of risk. Mutations with a high risk are more likely to cause cancer in their offspring, while mutations with a low risk are less likely. It is the mutated gene that determines the level of risk. Reports show that canine mammary cancer, lymphoma, leukemia, and mast cell tumors result from genetic alterations. Similarly, lymphoma, mammary cancer, and mast cell tumors in cats are reported to result from genetic mutations.

Learning how mutations lead to cancer helps you understand your pet’s risk. Talk to your vet about your pet’s bloodline, what increases your pet’s chance of developing cancer, and treatment options after diagnosis. These discussions will help you and your beloved furry friend enjoy many happy tomorrows together.

The Pet Cancer Foundation’s Website Editorial team is comprised of veterinarians, veterinary oncologists, and veterinary technicians, as well as scientific writers and editors who have attained their PhD’s in the life sciences, along with general editors and research assistants. All content found in this section goes through an extensive process with multiple review stages, to ensure this extended resource provides pet families with the most up-to-date information publicly available.

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Last Updated: November 13, 2022

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