AAV9-Mediated PTEN Gene Therapy Rescues Hepatic Pathology and Neuroanatomical Abnormalities in a Murine Model of PTEN Hamartoma Tumour Syndrome.

Background/Objectives: PTEN Hamartoma Tumour Syndrome (PHTS) is a rare inherited disorder caused by germline PTEN mutations, presenting with cancer predisposition and neurodevelopmental abnormalities, including macrocephaly. PTEN functions as a tumour suppressor by regulating the PI3K/AKT/mTOR pathway and contributes to cellular adhesion, migration, and genomic stability. As no curative therapy exists, gene therapy represents a promising avenue to correct the underlying genetic defect. Methods: In this study we evaluated the therapeutic potential of AAV9-mediated PTEN gene delivery in a PtenΔ5/+ mouse model, which is predominantly characterized by progressive lymphoid hyperplasia leading to lymph node tumour development, as well as hepatic focal lesions and macrocephaly. Results: Systemic vector delivery did not improve lymph node enlargement which represents the predominant disease phenotype in the PtenΔ5/+ mice at the doses tested, due to restricted vector biodistribution, but it did effectively rescue the hepatic lesions, including steatosis and steatohepatitis-like changes. Mechanistically, AAV-mediated PTEN expression significantly reduced elevated p-AKT levels, indicating attenuated hyperactivation of the PI3K/AKT/mTOR pathway. Additionally, intracranial delivery of the same vector in PtenΔ5/+ mouse neonates ameliorated macrocephaly without apparent adverse effects. Conclusions: These findings highlight the therapeutic potential of AAV9-mediated PTEN gene therapy in PHTS, particularly for hepatic and neuroanatomical manifestations. Optimization of vector biodistribution and transduction efficiency will be critical for clinical translation.