Home » Pet Health » Genes and Cancer » What are Tumor Suppressor Genes?


Cancer in pets can occur because of different factors, including infectious agents like viruses, environmental influences like chemical toxins, and genetic causes. Cancer may arise when these factors affect cells’ typical growth and division. Specific genes called tumor suppressor genes (TSGs) form proteins designed to keep cell growth and division under control, and scientists, therefore, call these genes the cell gatekeepers. Inactivation or “turning off” TSGs can lead to uncontrolled cell growth and cancer, and TSGs are thus vital for preventing cancer.

The three main types of TSGs are as follows:

    1. Genes that inhibit cell growth
    1. Genes that repair damaged DNA
    1. Genes that instruct cells to die (programmed cell death)

TSGs are recessive at the cellular level, which means the TSG copy from the mom and the copy from the dad must mutate for a cell to become cancerous. There is approximately a one-in-a-million chance that a single copy of a TSG will mutate in a cell. Even if such an event occurs, the second copy of the TSG can maintain the gene’s tumor-suppressing function. Collectively, the chance of both copies of a TSG developing a loss of function is one in a billion.

Some TSGs associated with cancer include the TP53 gene, the phosphatase and tensin homolog (PTEN) gene, and the BRCA1 and BRCA2 breast cancer genes.
TP53 gene
The tumor-suppressor TP53 gene is the “guardian of the genome”. This gene leads to the development of the p53 protein, which is involved in repairing the damaged DNA. Without DNA repair, the p53 protein initiates programmed cell death and removes the damaged cells. But, if cells have p53 mutations and damaged DNA evades detection, the cells will not self-destruct, resulting in the development of cancer cells that divide uncontrollably, potentially spreading in the body.

Approximately 50% of human cancers arise from damage to the TP53 gene. Similarly, most cancers in dogs are due to mutations of the TP53 gene, and experts have found TP53 mutations in various cat tumors, including mammary cancers.
Phosphatase and Tensin Homolog (PTEN) gene
The PTEN gene instructs the production of the tumor-suppressor PTEN protein, which controls biological processes such as cell death, metabolism, and growth. If PTEN is not functioning correctly, cells will divide and grow uncontrollably. PTEN mutation in dogs can cause mammary and vascular cancers, while the role of the PTEN gene in feline cancers is not known.
BRCA1 and BRCA2 genes
The proteins arising from the BRCA1 and BRCA2 genes repair damaged DNA. Mutations in these genes are associated with mammary tumor development in dogs.

Gaining a greater understanding of the cause of your pet’s cancer allows you to understand the biology behind cancer. Your newfound knowledge also gives you the confidence to discuss your furry friend’s diagnosis and treatment options with your vet.

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Last Updated: November 14, 2022

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The following sources were referenced to write the content on this page: 

Abreu Velez, AM & Howard, MS 2015, ‘Tumor-suppressor genes, cell cycle regulatory checkpoints, and the skin’, N Am J Med Sci, vol. 7, no. 5, pp. 176-188.

Adega, F, Borges, A & Chaves, R 2016, ‘Cat mammary tumors: genetic models for the human counterpart’, Vet Sci, vol. 3, no. 3, pp. 17-37.

Dickerson, EB, Thomas, R, Fosmire, SP, Lamerato-Kozicki, AR, Bianco, SR, Wojcieszyn, JW, Breen, M, Helfand, SC & Modiano, JF 2005, ‘Mutations of phosphatase and tensin homolog deleted from chromosome 10 in canine hemangiosarcoma’, Vet Pathol, vol. 42, no. 5, pp. 618-632.

Frank, TS 2001, ‘Hereditary cancer syndromes’, Arch Pathol Lab Med, vol. 125, no. 1, pp. 85-90.

Koshino, A, Goto-Koshino, Y, Setoguchi, A, Ohno, K & Tsujimoto, H 2016, ‘Mutation of p53 gene and its correlation with the clinical outcome in dogs with lymphoma’, J Vet Intern Med, vol. 30, no. 1, pp. 223-229.

Mayr, B, Blauensteiner, J, Edlinger, A, Reifinger, M, Alton, K, Schaffner, G & Brem, G 2000, ‘Presence of p53 mutations in feline neoplasms’, Res Vet Sci, vol. 68, no. 1, pp. 63-70.

Morris, LG & Chan, TA 2015, ‘Therapeutic targeting of tumor suppressor genes’, Cancer, vol. 121, no. 9, pp. 1357-1368.

Ozaki, T & Nakagawara, A 2011, ‘Role of p53 in cell death and human cancers’, Cancers, vol. 3, no. 1, pp. 994-1013.

Qiu, C, Lin, D, Wang, J & Wang, L 2008, ‘Expression and significance of PTEN in canine mammary gland tumours’, Res Vet Sci, vol. 85, no. 2, pp. 383-388.

Ressel, L, Millanta, F, Caleri, E, Innocenti, VM & Poli, A 2009, ‘Reduced PTEN protein expression and its prognostic implications in canine and feline mammary tumors’, Vet Pathol, vol. 46, no. 5, pp. 860-868.

Saif, R, Khan, E, Azhar, A, Choudhary, S, Hussain, T, Babar, ME, Awan, AR, Tayyab, M, Zia, S & Wasim, M 2016, ‘Insight of Tp53 mutations and their effect on protein in different feline and canine neoplasms’, Adv Life Sci, vol. 3, no. 2, pp. 42-50.

Thumser-Henner, P, Nytko, KJ & Rohrer Bley, C 2020, ‘Mutations of BRCA2 in canine mammary tumors and their targeting potential in clinical therapy’, BMC Vet Res, vol. 16, no. 1, pp. 30-39.

Wang, L-H, Wu, C-F, Rajasekaran, N & Shin, YK 2018, ‘Loss of tumor suppressor gene function in human cancer: an overview’, Cell Physiol Biochem, vol. 51, no. 6, pp. 2647-2693.

Williams, AB & Schumacher, B 2016, ‘p53 in the DNA-damage-repair process’, Cold Spring Harb Perspect Med, vol. 6, no. 5, pp. a026070- a026086.

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