Foundations · Year 1 · from Foundations
Case 2: Li-Fraumeni Syndrome (TP53 Germline Mutation)
Clinical Image
Source: Wikipedia - Li-Fraumeni syndrome - CC BY-SA 3.0
Case Presentation
A 28-year-old woman is diagnosed with breast cancer. Her family history is striking: her father died of a brain tumor at age 35, her brother had osteosarcoma at age 15, and her paternal aunt had adrenocortical carcinoma in childhood. Given this constellation of early-onset, diverse cancers, Li-Fraumeni syndrome is suspected. Genetic testing confirms a germline pathogenic variant in TP53. The genetic counselor explains that p53 is the "guardian of the genome," responding to DNA damage by activating cell cycle arrest (through p21 induction, which inhibits CDKs) to allow repair, or apoptosis if damage is severe. Without functional p53, cells with DNA damage continue dividing and accumulate mutations. Li-Fraumeni patients have extremely high cancer risk (nearly 100% lifetime), with characteristic tumor spectrum including soft tissue sarcomas, osteosarcoma, breast cancer, brain tumors, adrenocortical carcinoma, and leukemia. She undergoes breast cancer treatment and is enrolled in intensive surveillance including annual whole-body MRI and brain MRI. Radiation therapy is minimized when possible due to increased secondary cancer risk. Her siblings and eventually her children are offered genetic testing.
Key Learning Points
- p53 is a transcription factor that responds to cellular stress (especially DNA damage) by activating genes for cell cycle arrest (p21), DNA repair (GADD45), or apoptosis (BAX, PUMA, NOXA)
- As the most frequently mutated gene in human cancer (>50% of tumors), p53 loss allows cells with damaged DNA to proliferate, accumulating the mutations that drive cancer progression
- Li-Fraumeni syndrome demonstrates that germline p53 mutations cause remarkably broad cancer susceptibility because p53 functions in response to all types of DNA damage in all cell types