PTEN (phosphatase and tensin homolog) is a gene that gives instructions to make the PTEN protein. This protein acts as a tumor suppressor, meaning it helps stop cells from growing and dividing too quickly. When PTEN is lost or changed, cells may grow out of control and form tumors.
The PTEN protein has several important roles inside the cell. In the cytoplasm (the fluid inside the cell), it slows down a growth pathway called PI3K/AKT/mTOR, acting like a brake to prevent unnecessary cell growth and survival signals. In the nucleus (the cell’s control center), PTEN helps repair DNA and regulate cell division. Together, these jobs help protect against cancer.
PTEN is normally present in almost all body tissues. It can be located in the cytoplasm, along the cell membrane, and in the nucleus. Pathologists can test for PTEN in tissue samples to see whether the protein is present or absent in tumor cells.
PTEN can stop working in several different ways. These include mutations in its DNA, deletions (complete loss of the gene), epigenetic silencing (chemical changes that turn the gene off), or interference from small molecules called microRNAs. When PTEN is lost, the pathway it normally controls becomes too active. This allows cancer cells to grow and survive more easily.
Pathologists can check for PTEN in tumor samples in a couple of ways. The most common is immunohistochemistry (IHC), a test that shows if PTEN protein is present in tumor cells. Another option is molecular testing such as next-generation sequencing (NGS), which looks for mutations or deletions in the PTEN gene.
When PTEN is tested, the results describe whether the tumor cells still show PTEN protein or if it has been lost.
Intact (normal) PTEN: The tumor cells still make PTEN protein, which means this pathway is likely working normally.
Loss of PTEN: The tumor cells no longer show PTEN protein. This finding is important because it can signal that the cancer may behave more aggressively or respond differently to certain treatments.
Molecular test results: If DNA testing is done, the report may describe a specific mutation or deletion in the PTEN gene.
Doctors use this information along with other test results to decide on treatment plans and follow-up care.
PTEN loss has been studied in many cancers, and in some it happens very often. Examples include:
Endometrial carcinoma: PTEN is frequently lost in endometrioid carcinoma, a common type of uterine cancer.
Prostate cancer: More than half of prostate cancers show PTEN loss, often linked to a higher chance of the cancer coming back or spreading.
Breast cancer: PTEN loss can occur in triple-negative breast cancers and may be linked to worse outcomes.
Glioblastoma: About 70% of these aggressive brain tumors show PTEN loss.
Colorectal cancer: Some cases show reduced or absent PTEN.
Melanoma and pancreatic cancer: Both can show PTEN loss.
Acute myeloid leukemia (AML): Up to 75% of cases show PTEN loss, which may make the disease harder to treat.
PTEN results can provide valuable information about how a cancer may behave. Tumors that lose PTEN are often more aggressive or more likely to return after treatment. In some cancers, PTEN loss also helps confirm the diagnosis, such as in endometrial carcinoma. PTEN can influence treatment choices as well. For example, breast cancers with PTEN loss may respond differently to HER2-targeted therapy, and prostate cancers with PTEN loss often have worse outcomes. In AML and other cancers, PTEN loss is being studied to better understand its impact on treatment response.
Research suggests that in some cancers affecting the PI3K/AKT pathway, which includes tumors with PTEN loss, daily low-dose aspirin after treatment may reduce the risk of recurrence. This effect is best studied in colorectal cancer, where aspirin has been linked to better survival in patients whose tumors have related pathway changes. While not yet a standard recommendation for PTEN loss alone, it is an important area of ongoing research. Patients should talk with their doctor before starting aspirin, as it may cause side effects.
PTEN mutations can also be inherited. People with inherited PTEN mutations may develop PTEN hamartoma tumor syndrome (PHTS), which includes Cowden syndrome. These conditions increase the risk of both noncancerous and cancerous growths in several parts of the body, including the skin, thyroid, breast, and gastrointestinal tract. Identifying PTEN mutations can be important not just for patients but also for family members.
Was my tumor tested for PTEN?
Did the results show intact or lost PTEN?
What does this mean for my type of cancer?
Should I be tested for an inherited PTEN condition?
Could aspirin therapy be considered for me?