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PIK3CA gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

PIK3CA gene

The PIK3CA gene plays a vital role in cell signaling and growth; mutations in this gene are associated with various overgrowth syndromes and several types of cancer.

Normal Function

The PIK3CA gene provides instructions for making the p110 alpha (p110α) protein, which is the catalytic subunit of an enzyme called phosphatidylinositol 3-kinase (PI3K). PI3K adds a phosphate group to other proteins through a process called phosphorylation. This triggers chemical signals within cells that are important for:

  • Cell growth and division (proliferation)
  • Cell movement (migration)
  • Production of new proteins
  • Transport of materials within cells
  • Cell survival

Health Conditions Related to Genetic Changes

Bladder cancer

Somatic mutations in the PIK3CA gene have been found in about half of non-muscle invasive bladder cancer (NMIBC) tumors. These mutations lead to an overactive PI3K enzyme, which contributes to uncontrolled cell growth and division.

Epidermal nevus

Mutations in the PIK3CA gene are associated with some keratinocytic epidermal nevi, which are abnormal skin growths. These somatic mutations cause cells to grow and divide more than normal. Individuals with this condition do not appear to have an elevated risk of developing cancer.

Klippel-Trenaunay syndrome

Somatic mutations in the PIK3CA gene cause Klippel-Trenaunay syndrome, characterized by a port-wine stain, abnormal overgrowth of soft tissues and bones, and vein malformations. These mutations arise randomly during early development, leading to mosaicism (a mixture of cells with and without the mutation). The resulting abnormally active PI3K triggers unregulated cell signaling, leading to overgrowth.

Megalencephaly-capillary malformation syndrome (MCAP)

MCAP is caused by somatic PIK3CA mutations that lead to overgrowth of the brain and enlargement of small blood vessels in the skin. Similar to Klippel-Trenaunay syndrome, these mutations result in mosaicism and abnormally active PI3K signaling.

Other disorders

Other conditions caused by PIK3CA mutations include hemimegalencephaly, fibroadipose hyperplasia, and CLOVES syndrome. Together, these overgrowth disorders are known as the PIK3CA-related overgrowth spectrum (PROS).

Cancers

Somatic mutations in the PIK3CA gene are found in many cancers, including those of the ovary, breast, lung, brain, stomach, and colorectal cancer. These mutations result in an altered p110α subunit that allows PI3K to signal without regulation, contributing to uncontrolled cell proliferation.

Frequently Asked Questions

Early signs often include asymmetry in body size, such as one limb being larger or longer than the other, or a noticeable difference in head circumference. Parents may notice port-wine stains (capillary malformations) on the skin, which are often present at birth or appear shortly after. Other indicators include unusual growth patterns, such as rapid enlargement of specific body parts, or developmental delays. If a child exhibits these asymmetric growth features or vascular skin marks, early evaluation by a geneticist or specialist is recommended.
Somatic mutations, which cause conditions like Klippel-Trenaunay syndrome or MCAP, occur after conception in specific cells and are not inherited from parents; they are generally not passed to children. These conditions are associated with overgrowth and vascular malformations rather than a high risk of cancer. In contrast, somatic mutations found in cancers like bladder cancer are acquired changes in tumor cells. While PIK3CA mutations are common in certain cancers, they are not typically inherited, and having a PIK3CA-related overgrowth syndrome does not significantly increase the general risk of developing cancer compared to the population.
The PIK3CA gene produces the p110 alpha protein, which is part of the PI3K enzyme responsible for adding phosphate groups to other proteins. This phosphorylation triggers signals that tell cells to grow, divide, and survive. When a mutation makes this enzyme overactive, the signaling pathway remains constantly "on," even when it should be off. This leads to unregulated cell proliferation and survival, causing tissues to grow excessively and form malformations, such as enlarged bones, soft tissue overgrowth, or abnormal blood vessel development.
Management focuses on monitoring for complications related to the overgrowth and vascular issues. Regular check-ups with a multidisciplinary team, including geneticists, vascular specialists, and orthopedists, are essential. Patients may need imaging studies to monitor the size and location of malformations. Lifestyle adjustments might include physical therapy to maintain mobility if limb overgrowth affects gait, and careful skin care to prevent injury to areas with vascular malformations. Pain management and psychological support are also important components of long-term care.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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